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Brain magnetic resonance study of Mecp2 deletion effects on anatomy and metabolism
Abstract
Rett syndrome, a neurodevelopmental X-linked disorder, represents the most important genetic cause of severe mental retardation in the female population and results from a mutation in the gene encoding methyl-CpG-binding protein 2 (MECP2). We report here the first characterization of Mecp2-null mice, by in vivo magnetic resonance imaging and spectroscopy, delineating the cerebral phenotype associated with the lack of Mecp2. We performed a morphometric study that revealed a size reduction of the whole brain and of structures involved in cognitive and motor functions (cerebellum and motor cortex). Significant metabolic anomalies, including reduced N-acetylaspartate, myo-inositol, and glutamine plus glutamate, and increased choline levels were evidenced. These findings indicate that not only neuronal but also glial metabolism is affected in Mecp2-null mice. Furthermore, we uncovered an important reduction of brain ATP level, a hitherto undetected anomaly of energy metabolism that may reflect and contribute to cerebral injury and dysfunction.
... Animal studies have been further conducted to explore the relationship between macroscopic brain structure changes and RTT phenotype. Saywell et al. investigated MECP2-null mice, a widely recognized experimental model of RTT, using conventional brain MRI and found a global reduction in its brain size, a feature constantly observed in patients with RTT (46). Reduced cerebellum size may account for some of the neurological signs observed in RTT, including cognition and motor coordination impairments. ...
... Reduced cerebellum size may account for some of the neurological signs observed in RTT, including cognition and motor coordination impairments. Moreover, the authors found significant thinning of some specific structures, such as the motor cortex and the corpus callosum (46). Elsewhere, Allemang-Grand et al. used a high-resolution MRI with deformation-based morphometric approaches to examine the brain structure of different mouse models carrying MECP2 mutations, demonstrating the severity of the mutation and the stage of behavioral impairment were associated with the degree of neuroanatomical changes (47). ...
... In addition to morphological studies, MRI sequences can provide other information about brain changes in patients with RTT; for example, the underlying tissue microstructure can be examined using diffusion MRI (dMRI) (55)(56)(57), functional information can be gathered using functional MRI (fMRI) (57), metabolic differences can be identified using magnetic resonance spectroscopy (MRS) (46), and cerebral blood flow (CBF) can be assessed using arterial spin labeling (ASL) (58,59). ...
Rett syndrome (RTT) is a rare neurodevelopmental disorder characterized by severe cognitive, social, and physical impairments resulting from de novo mutations in the X-chromosomal methyl-CpG binding protein gene 2 (MECP2). While there is still no cure for RTT, exploring up-to date neurofunctional diagnostic markers, discovering new potential therapeutic targets, and searching for novel drug efficacy evaluation indicators are fundamental. Multiple neuroimaging studies on brain structure and function have been carried out in RTT-linked gene mutation carriers to unravel disease-specific imaging features and explore genotype-phenotype associations. Here, we reviewed the neuroimaging literature on this disorder. MRI morphologic studies have shown global atrophy of gray matter (GM) and white matter (WM) and regional variations in brain maturation. Diffusion tensor imaging (DTI) studies have demonstrated reduced fractional anisotropy (FA) in left peripheral WM areas, left major WM tracts, and cingulum bilaterally, and WM microstructural/network topology changes have been further found to be correlated with behavioral abnormalities in RTT. Cerebral blood perfusion imaging studies using single-photon emission CT (SPECT) or PET have evidenced a decreased global cerebral blood flow (CBF), particularly in prefrontal and temporoparietal areas, while magnetic resonance spectroscopy (MRS) and PET studies have contributed to unraveling metabolic alterations in patients with RTT. The results obtained from the available reports confirm that multimodal neuroimaging can provide new insights into a complex interplay between genes, neurotransmitter pathway abnormalities, disease-related behaviors, and clinical severity. However, common limitations related to the available studies include small sample sizes and hypothesis-based and region-specific approaches. We, therefore, conclude that this field is still in its early development phase and that multimodal/multisequence studies with improved post-processing technologies as well as combined PET–MRI approaches are urgently needed to further explore RTT brain alterations.
... Mecp2 (−/y)null Yes [116,120,121] Yes [164] No [165,166] Mecp2 (−/y) -308 ...
... Despite this, the authors here presented a highly reproducible technique that could be used in future neuroanatomical assessments and were the first high-resolution MRI examinations of a transgenic mouse model. In 2006, Saywell et al. [116] examined the hemizygous male Mecp2 KO mouse. The authors calculated the volume of many different structures including the cerebellum, caudate, putamen, hippocampus, thalamus, olfactory bulbs, and lateral ventricles. ...
... MRI was employed to calculate 4 different neuroanatomical measures: total brain volume, cerebellar volume, ventricular volume, and motor cortex thickness. Similar to the study by Saywell et al. [116], smaller total brain volumes were found in the Mecp2 KO mice at all time points. The cerebellar volume was also decreased initially, but was normalized at 42 days of age. ...
In order to understand the consequences of the mutation on behavioral and biological phenotypes relevant to autism, mutations in many of the risk genes for autism spectrum disorder have been experimentally generated in mice. Here, we summarize behavioral outcomes and neuroanatomical abnormalities, with a focus on high-resolution magnetic resonance imaging of postmortem mouse brains. Results are described from multiple mouse models of autism spectrum disorder and comorbid syndromes, including the 15q11-13, 16p11.2, 22q11.2, Cntnap2, Engrailed2, Fragile X, Integrinβ3, MET, Neurexin1a, Neuroligin3, Reelin, Rett, Shank3, Slc6a4, tuberous sclerosis, and Williams syndrome models, and inbred strains with strong autism-relevant behavioral phenotypes, including BTBR and BALB. Concomitant behavioral and neuroanatomical abnormalities can strengthen the interpretation of results from a mouse model, and may elevate the usefulness of the model system for therapeutic discovery.
... Whereas these early pioneer studies primarily focused on mitochondrial morphology, they were extended by reports on functional impairments of mitochondria. These included less negative mitochondrial membrane potentials and an increased ratio of FAD/NADH [14], increased respiration rates [15], an intensified oxidative burden [14,16], and lowered cerebral ATP content [17]. Furthermore, various pathways closely related to mitochondrial metabolism were found to be modulated in patient plasma [8] and MeCP2-deficient mouse neocortex [18]. ...
... The available data present a range of findings concerning the metabolic conditions of MeCP2-deficient brain tissue. Reduced brain ATP levels in Mecp2-null mice [17] and heterozygous Mecp2-mutant female mice [25], increased ATP production with intensified ATP turnover rates in neonatal Mecp2 −/y hippocampal neurons [58], comparable ATP contents in acute hippocampal tissue slices from Mecp2 −/y mice [59], and unchanged ATP/O ratios in male Mecp2-null mouse brain mitochondria [15] were reported. It, therefore, seems that more detailed analyses with cell-type-specific resolutions will be required to solve the issue of cellular ATP supply and consumption in MeCP2-deficient neuronal networks. ...
Rett syndrome (RTT) is a genetic neurodevelopmental disorder with mutations in the X-chromosomal MECP2 (methyl-CpG-binding protein 2) gene. Most patients are young girls. For 7-18 months after birth, they hardly present any symptoms; later they develop mental problems, a lack of communication, irregular sleep and breathing, motor dysfunction, hand stereotypies, and seizures. The complex pathology involves mitochondrial structure and function. Mecp2-/y hippocampal astrocytes show increased mitochondrial contents. Neurons and glia suffer from oxidative stress, a lack of ATP, and increased hypoxia vulnerability. This spectrum of changes demands comprehensive molecular studies of mitochondria to further define their pathogenic role in RTT. Therefore, we applied a comparative proteomic approach for the first time to study the entity of mitochondrial proteins in a mouse model of RTT. In the neocortex and hippocampus of symptomatic male mice, two-dimensional gel electrophoresis and subsequent mass-spectrometry identified various differentially expressed mitochondrial proteins, including components of respiratory chain complexes I and III and the ATP-synthase FoF1 complex. The NADH-ubiquinone oxidoreductase 75 kDa subunit, NADH dehydrogenase [ubiquinone] iron-sulfur protein 8, NADH dehydrogenase [ubiquinone] flavoprotein 2, cytochrome b-c1 complex subunit 1, and ATP synthase subunit d are upregulated either in the hippocampus alone or both the hippocampus and neocortex of Mecp2-/y mice. Furthermore, the regulatory mitochondrial proteins mitofusin-1, HSP60, and 14-3-3 protein theta are decreased in the Mecp2-/y neocortex. The expressional changes identified provide further details of the altered mitochondrial function and morphology in RTT. They emphasize brain-region-specific alterations of the mitochondrial proteome and support the notion of a metabolic component of this devastating disorder.
... Reduction in the whole brain size and weight has been reported in most Mecp2 mutant mice (Saywell et al., 2006;Stearns et al., 2007;Ward et al., , 2009). In particular, through Magnetic Resonance Imaging (MRI), Saywell and colleagues proved that 5-8 weeks old KO male mice feature the expected global reduction in brain size (Saywell et al., 2006). ...
... Reduction in the whole brain size and weight has been reported in most Mecp2 mutant mice (Saywell et al., 2006;Stearns et al., 2007;Ward et al., , 2009). In particular, through Magnetic Resonance Imaging (MRI), Saywell and colleagues proved that 5-8 weeks old KO male mice feature the expected global reduction in brain size (Saywell et al., 2006). ...
Rett syndrome (RTT) is a X-linked neurodevelopmental disorder which represents the leading cause of severe incurable intellectual disability in females worldwide. The vast majority of RTT cases are caused by mutations in the X-linked MECP2 gene, and preclinical studies on RTT largely benefit from the use of mouse models of Mecp2, which present a broad spectrum of symptoms phenocopying those manifested by RTT patients. Neurons represent the core targets of the pathology; however, neuroanatomical abnormalities that regionally characterize the Mecp2 deficient mammalian brain remain ill-defined. Neuroimaging techniques, such as MRI and MRS, represent a key approach for assessing in vivo anatomic and metabolic changes in brain. Being non-invasive, these analyses also permit to investigate how the disease progresses over time through longitudinal studies. To foster the biological comprehension of RTT and identify useful biomarkers, we have performed a thorough in vivo longitudinal study of MRI and MRS in Mecp2 deficient mouse brains. Analyses were performed on both genders of two different mouse models of RTT, using an automatic atlas-based segmentation tool that permitted to obtain a detailed and unbiased description of the whole RTT mouse brain. We found that the most robust alteration of the RTT brain consists in an overall reduction of the brain volume. Accordingly, Mecp2 deficiency generally delays brain growth, eventually leading, in heterozygous older animals, to stagnation and/or contraction. Most but not all brain regions participate to the observed deficiency in brain size; similarly, the volumetric defect progresses diversely in different brain areas also depending on the specific Mecp2 genetic lesion and gender. Interestingly, in some regions volumetric defects anticipate overt symptoms, possibly revealing where the pathology originates and providing a useful biomarker for assessing drug efficacy in pre-clinical studies.
... Another report of a study in which MRI was performed for children with RTT revealed decreased volumes of the cerebellum, whereas cerebral cortical volumes and subcortical gray matter volumes were preserved in the children (Shiohama et al., 2019). In addition, MRI studies using a mouse model for RTT such as Mecp2-null KO mice showed volume loss in many of the same areas as humans, suggesting that these models reproduce the human phenotypic gross anatomy (Saywell et al., 2006;Ward et al., 2009). However, these studies using RTT mouse models limited their analyses to certain areas and detailed volume changes throughout the Mecp2-deficient brain have not been fully investigated. ...
... Our data showed the global and local volume reduction in the brain of Mecp2-KO mice compared with WT mice, and further analysis revealed the specific volume changes and laterality in several brain regions. The overall volume reduction of the brain has consistently been found in RTT patients (Murakami et al., 1992;Reiss et al., 1993;Carter et al., 2008) and in mouse models (Saywell et al., 2006;Ward et al., 2009). These gross reductions in the RTT brain may correlate with cellular phenotypes, such as generalized reductions in neuronal soma size and dendritic arborizations (Armstrong et al., 1995). ...
Rett syndrome (RTT) is a severe progressive neurodevelopmental disorder characterized by various neurological symptoms. Almost all RTT cases are caused by mutations in the X-linked methyl-CpG-binding protein 2 (MeCP2) gene, and several mouse models have been established to understand the disease. However, the neuroanatomical abnormalities in each brain region of RTT mouse models have not been fully understood. Here, we investigated the global and local neuroanatomy of the Mecp2 gene-deleted RTT model (Mecp2-KO) mouse brain using T2-weighted 3D magnetic resonance imaging with different morphometry to clarify the brain structural abnormalities that are involved in the pathophysiology of RTT. We found a significant reduction in global and almost all local volumes in the brain of Mecp2-KO mice. In addition, a detailed comparative analysis identified specific volume reductions in several brain regions in the Mecp2-deficient brain. Our analysis also revealed that the Mecp2-deficient brain shows changes in hemispheric asymmetry in several brain regions. These findings suggest that MeCP2 affects not only the whole-brain volume but also the region-specific brain structure. Our study provides a framework for neuroanatomical studies of a mouse model of RTT.
... Adenosine levels are also dependent on ATP levels (Boison, 2015), therefore, we cannot exclude the potential role of dysregulated bioenergetics due to dysfunctional mitochondria in RTT. Although lower levels of ATP were already reported in the brain of Mecp2 -/y mice (Saywell et al., 2006;Toloe et al., 2014), in the present work, we did not detected significant differences on the content of ATP when comparing hippocampus and cortex from WT and Mecp2 -/y mice. Interestingly, studies performed in organotypic hippocampal cultures have shown a downregulation on mitochondrial gene expression (Großer et al., 2012). ...
... Moreover, a quantitative decrease in electron transport chain units and reduced efficiency of glucose metabolism were found in RTT mouse models (De Filippis et al., 2015;Kriaucionis et al., 2006;Saywell et al., 2006). Also lower A 1 R receptor number or lower responsiveness of the A 1 R did not explain lower tonic adenosinergic inhibition because Mecp2 -/y mice had enhanced A 1 R protein levels (as revealed by binding assays and western blot technique), and the response to an added A 1 R agonist was even higher in slices of Mecp2 -/y mice. ...
Rett syndrome (RTT; OMIM#312750) is mainly caused by mutations in the X-linked MECP2 gene (methyl-CpG-binding protein 2 gene; OMIM*300005), which leads to impairments in the brain-derived neurotrophic factor (BDNF) signalling. The boost of BDNF mediated effects would be a significant breakthrough but it has been hampered by the difficulty to administer BDNF to the central nervous system. Adenosine, an endogenous neuromodulator, may accomplish that role since through A2AR it potentiates BDNF synaptic actions in healthy animals. We thus characterized several hallmarks of the adenosinergic and BDNF signalling in RTT and explored whether A2AR activation could boost BDNF actions.
For this study, the RTT animal model, the Mecp2 knockout (Mecp2−/y) (B6.129P2 (C)-Mecp2tm1.1Bird/J) mouse was used. Whenever possible, parallel data was also obtained from post-mortem brain samples from one RTT patient. Ex vivo extracellular recordings of field excitatory post-synaptic potentials in CA1 hippocampal area were performed to evaluate synaptic transmission and long-term potentiation (LTP). RT-PCR was used to assess mRNA levels and Western Blot or radioligand binding assays were performed to evaluate protein levels. Changes in cortical and hippocampal adenosine content were assessed by liquid chromatography with diode array detection (LC/DAD).
Hippocampal ex vivo experiments revealed that the facilitatory actions of BDNF upon LTP is absent in Mecp2−/y mice and that TrkB full-length (TrkB-FL) receptor levels are significantly decreased. Extracts of the hippocampus and cortex of Mecp2−/y mice revealed less adenosine amount as well as less A2AR protein levels when compared to WT littermates, which may partially explain the deficits in adenosinergic tonus in these animals. Remarkably, the lack of BDNF effect on hippocampal LTP in Mecp2−/y mice was overcome by selective activation of A2AR with CGS2168.
Overall, in Mecp2−/y mice there is an impairment on adenosinergic system and BDNF signalling. These findings set the stage for adenosine-based pharmacological therapeutic strategies for RTT, highlighting A2AR as a therapeutic target in this devastating pathology.
... Therefore, astrocytic dysfunction may result in aberrant metabolic support in the brain. Brain magnetic resonance spectroscopy (MRS) of Mecp2 308/y and Mecp2 tm1.1Bird/y mice found significant metabolic anomalies, including a reduced amount of the sugar myo-inositol, which is an abundant osmolyte in glial cells and considered a putative glial marker [31,36]. Myo-inositol was normalized when mice were treated with CNF1 [31]. ...
... Cerebrospinal fluid and brains of RTT patients contain high levels of glutamate [47,48]. However, another brain MRS study showed decreased levels of glutamine/glutamate in brains of Mecp2 tm1.1Bird/y mice [36]. Additional studies found that astrocytes cultured from Mecp2 tm1.1Bird/y brains had higher glutamate clearance due to a lack of negative feedback from glutamate transporter downregulation [21]. ...
Rett syndrome (RTT) is a rare, X-linked neurodevelopmental disorder typically affecting females, resulting in a range of symptoms including autistic features, intellectual impairment, motor deterioration, and autonomic abnormalities. RTT is primarily caused by the genetic mutation of the Mecp2 gene. Initially considered a neuronal disease, recent research shows that glial dysfunction contributes to the RTT disease phenotype. In the following manuscript, we review the evidence regarding glial dysfunction and its effects on disease etiology.
... Also, brain ATP content is affected. Higher resting ATP levels with increased ATP turnover rates were reported for neonatal hippocampal Mecp2 −/y neurons (Toloe et al., 2014), whereas whole brain studies on adult symptomatic male and female Rett mice detected reduced ATP concentrations (Saywell et al., 2006;De Filippis et al., 2015;Valenti et al., 2017). ...
... Also in Rett mice, lowered enzymatic activities of the respiratory complexes are evident in brain and skeletal muscle (Kriaucionis et al., 2006;Gold et al., 2014;De Filippis et al., 2015;Valenti et al., 2017). In concert with altered O 2 consumption rates (Kriaucionis et al., 2006) these changes may easily culminate in reduced brain ATP contents (Saywell et al., 2006;De Filippis et al., 2015;Valenti et al., 2017). ...
Rett syndrome (RTT), an X chromosome-linked neurodevelopmental disorder affecting almost exclusively females, is associated with various mitochondrial alterations. Mitochondria are swollen, show altered respiratory rates, and their inner membrane is leaking protons. To advance the understanding of these disturbances and clarify their link to redox impairment and oxidative stress, we assessed mitochondrial respiration in defined brain regions and cardiac tissue of male wildtype (WT) and MeCP2-deficient (Mecp2-/y) mice. Also, we quantified for the first time neuronal redox-balance with subcellular resolution in cytosol and mitochondrial matrix. Quantitative roGFP1 redox imaging revealed more oxidized conditions in the cytosol of Mecp2-/y hippocampal neurons than in WT neurons. Furthermore, cytosol and mitochondria of Mecp2-/y neurons showed exaggerated redox-responses to hypoxia and cell-endogenous reactive oxygen species (ROS) formation. Biochemical analyzes exclude disease-related increases in mitochondrial mass in Mecp2-/y hippocampus and cortex. Protein levels of complex I core constituents were slightly lower in Mecp2-/y hippocampus and cortex than in WT; those of complex V were lower in Mecp2-/y cortex. Respiratory supercomplex-formation did not differ among genotypes. Yet, supplied with the complex II substrate succinate, mitochondria of Mecp2-/y cortex and hippocampus consumed more O2 than WT. Furthermore, mitochondria from Mecp2-/y hippocampus and cortex mediated an enhanced oxidative burden. In conclusion, we further advanced the molecular understanding of mitochondrial dysfunction in RTT. Intensified mitochondrial O2 consumption, increased mitochondrial ROS generation and disturbed redox balance in mitochondria and cytosol may represent a causal chain, which provokes dysregulated proteins, oxidative tissue damage, and contributes to neuronal network dysfunction in RTT.
... Further, they raise the possibility that impaired mitochondrial function could indeed play a contributing rather than passive role in RTT pathogenic progression. Finally, the decreased ATP levels that have been observed in the symptomatic MeCP2-null mouse brain (Saywell et al., 2006), in the female Mecp2 308 mouse brain (De Filippis et al., 2015), and in isolated Mecp2 −/y microglia (Jin et al., 2015) provides further evidence that the absence of MeCP2 leads to impaired mitochondrial function. ...
... Functional studies have supported this, as Gibson et al. (2010) showed decreased cytochrome c oxidase activity (Complex IV) in SH-SY5Y cells following MeCP2 knockdown, and Gold et al. (2014) reported a marked decrease in the activities of Complexes II, Complex III and Complex IV in both cerebellum and skeletal muscle of symptomatic MeCP2-null mice. Additional studies have reported increased respiration rates-but lower mitochondrial efficiencies-in mitochondria isolated from acute MeCP2-null mouse hippocampal slices (Großer et al., 2012), along with decreased ATP levels in both MeCP2-null mice brains (Saywell et al., 2006), and in MeCP2-null microglia cells (Jin et al., 2015). Similarly, Kriaucionis et al. (2006) reported that symptomatic MeCP2-null mice display increased expression of ubiquinolcytochrome c reductase core protein 1 (Uqcrc1), and increased uncouple respiration rates upstream of complex IV. ...
First described over 50 years ago, Rett syndrome (RTT) is a neurodevelopmental disorder caused primarily by mutations of the X-linked MECP2 gene. RTT affects predominantly females, and has a prevalence of roughly 1 in every 10,000 female births. Prior to the discovery that mutations of MECP2 are the leading cause of RTT, there were suggestions that RTT could be a mitochondrial disease. In fact, several reports documented altered mitochondrial structure, and deficiencies in mitochondrial enzyme activity in different cells or tissues derived from RTT patients. With the identification of MECP2 as the causal gene, interest largely shifted toward defining the normal function of MeCP2 in the brain, and how its absence affects the neurodevelopment and neurophysiology. Recently, though, interest in studying mitochondrial function in RTT has been reignited, at least in part due to observations suggesting systemic oxidative stress does play a contributing role in RTT pathogenesis. Here we review data relating to mitochondrial alterations at the structural and functional levels in RTT patients and model systems, and present a hypothesis for how the absence of MeCP2 could lead to altered mitochondrial function and elevated levels of cellular oxidative stress. Finally, we discuss the prospects for treating RTT using interventions that target specific aspects of mitochondrial dysfunction and/or oxidative stress.
... Finally, ANT1 gene, which encodes for mitochondrial adenine nucleotides translocator, is up-regulated in MeCP2-null mouse and in RTT patient fibroblasts (Forlani et al., 2010). As consequence of these mitochondrial alterations, mitochondrial respiration would be less efficient, leading to reduced brain ATP levels, as detected in a magnetic resonance study on MeCP2-deficient mice (Saywell et al., 2006). Although these data are indicative of widespread mitochondrial dysfunction, the cause of defective mitochondria is still unclear and it remains to be investigated whether and how alterations in pathways/biomolecules of the mitochondrial energy metabolism are involved in the pathogenesis of the syndrome and could cause the chronic OS observed in RTT patients. ...
... Markers of oxidative stress such as lipid peroxidation, plasma isoprostanes and protein modifications have been described to be increased in RTT patients (De Felice et al., 2012b). Consistent with a harmful role of ROS in lipid metabolism and mitochondrial function, brain profile of cholinecontaining phospholipids has been found to be abnormal in MeCP2 mutant mice (Saywell et al., 2006;De Filippis et al., 2012) and in patients (Naidu et al., 2001). Blood samples of patients revealed a reduced activity of the scavenging enzyme superoxide dismutase (Sierra et al., 2001) as well as decreased vitamin E levels (Formichi et al., 1998). ...
... Finally, ANT1 gene, which encodes for mitochondrial adenine nucleotides translocator, is up-regulated in MeCP2-null mouse and in RTT patient fibroblasts (Forlani et al., 2010). As consequence of these mitochondrial alterations, mitochondrial respiration would be less efficient, leading to reduced brain ATP levels, as detected in a magnetic resonance study on MeCP2-deficient mice (Saywell et al., 2006). ...
... Markers of oxidative stress such as lipid peroxidation, plasma isoprostanes and protein modifications have been described to be increased in RTT patients (De Felice et al., 2012b). Consistent with a harmful role of ROS in lipid metabolism and mitochondrial function, brain profile of cholinecontaining phospholipids has been found to be abnormal in MeCP2 mutant mice (Saywell et al., 2006;De Filippis et al., 2012) and in patients (Naidu et al., 2001). Blood samples of patients revealed a reduced activity of the scavenging enzyme superoxide dismutase (Sierra et al., 2001) as well as decreased vitamin E levels (Formichi et al., 1998). ...
... The bioenergetic alterations are maintained in Rett mice brains. This agrees with studies that reported a decrease in brain ATP synthesis [33][34][35], but while knowledge was mostly limited to whole brain analysis, we have studied bioenergetic function both between different brain areas and at two different time-points through the phenotype progression. Our results in symptomatic 7 m.o. ...
Background
Rett syndrome is a neuropediatric disease occurring due to mutations in MECP2 and characterized by a regression in the neuronal development following a normal postnatal growth, which results in the loss of acquired capabilities such as speech or purposeful usage of hands. While altered neurotransmission and brain development are the center of its pathophysiology, alterations in mitochondrial performance have been previously outlined, shaping it as an attractive target for the disease treatment.
Methods
We have thoroughly described mitochondrial performance in two Rett models, patients’ primary fibroblasts and female Mecp2 tm1.1Bird−/+ mice brain, discriminating between different brain areas. The characterization was made according to their bioenergetics function, oxidative stress, network dynamics or ultrastructure. Building on that, we have studied the effect of leriglitazone, a PPARγ agonist, in the modulation of mitochondrial performance. For that, we treated Rett female mice with 75 mg/kg/day leriglitazone from weaning until sacrifice at 7 months, studying both the mitochondrial performance changes and their consequences on the mice phenotype. Finally, we studied its effect on neuroinflammation based on the presence of reactive glia by immunohistochemistry and through a cytokine panel.
Results
We have described mitochondrial alterations in Rett fibroblasts regarding both shape and bioenergetic functions, as they displayed less interconnected and shorter mitochondria and reduced ATP production along with increased oxidative stress. The bioenergetic alterations were recalled in Rett mice models, being especially significant in cerebellum, already detectable in pre-symptomatic stages. Treatment with leriglitazone recovered the bioenergetic alterations both in Rett fibroblasts and female mice and exerted an anti-inflammatory effect in the latest, resulting in the amelioration of the mice phenotype both in general condition and exploratory activity.
Conclusions
Our studies confirm the mitochondrial dysfunction in Rett syndrome, setting the differences through brain areas and disease stages. Its modulation through leriglitazone is a potential treatment for this disorder, along with other diseases with mitochondrial involvement. This work constitutes the preclinical necessary evidence to lead to a clinical trial.
... More recent MRI studies using voxelbased methods have provided evidence of selective alterations in related brain regions such as cerebellum, occipital cortex, and anterior frontal lobe for the gray matter, as well as the corpus callosum and fibers in the frontal area for the white matter (Carter et al., 2008;Mahmood et al., 2010;Shiohama et al., 2019). MRI studies on Mecp2-null(KO) mice showed overlapping brain areas with decreased volume, supporting the hypothesis of regional brain reduction in RTT (Saywell et al., 2006;Akaba et al., 2022). In accordance with the previous studies, our results also exhibited more regional reductions in gray matter volume and more regional alterations in white matter parameters in girls with RTT. ...
Rett syndrome (RTT) is a neurodevelopmental disorder caused by loss-of-function variants in the MECP2 gene, currently with no cure. Neuroimaging is an important tool for obtaining non-invasive structural and functional information about the in vivo brain. Multiple approaches to magnetic resonance imaging (MRI) scans have been utilized effectively in RTT patients to understand the possible pathological basis. This study combined developmental evaluations with clinical severity, T1-weighted imaging, and diffusion tensor imaging, aiming to explore the structural alterations in cohorts of young girls with RTT, idiopathic autism spectrum disorder (ASD), or typical development. Voxel-based morphometry (VBM) was used to determine the voxel-wised volumetric characteristics of gray matter, while tract-based spatial statistics (SPSS) was used to obtain voxel-wised properties of white matter. Finally, a correlation analysis between the brain structural alterations and the clinical evaluations was performed. In the RTT group, VBM revealed decreased gray matter volume in the insula, frontal cortex, calcarine, and limbic/paralimbic regions; TBSS demonstrated decreased fractional anisotropy (FA) and increased mean diffusivity (MD) mainly in the corpus callosum and other projection and association fibers such as superior longitudinal fasciculus and corona radiata. The social impairment quotient and clinical severity were associated with these morphometric alterations. This monogenic study with an early stage of RTT may provide some valuable guidance for understanding the disease pathogenesis. At the same time, the pediatric-adjusted analytic pipelines for VBM and TBSS were introduced for significant improvement over classical approaches for MRI scans in children.
... A downward trend in brain-to-body-weight ratios was also observed in our P14 pups, similar to the trends of decreasing brain volume that have been observed in neu-roligin3 mGluR5 -/-mice, a model of another monogenic heritable form of autism [31]. Another longitudinal study performed on a model of Rett syndrome, a neurodevelopmental X-linked disorder, showed smaller total brain volumes for multiple age groups [32]. Saywell et al. specifically showed a decrease in ventricular volume as being negatively correlated with improved locomotive activity. ...
The number of reported cases of neurodevelopmental disorders has increased significantly in the last few decades, but the etiology of these diseases remains poorly understood. There is evidence of a fundamental link between genetic abnormalities and symptoms of autism spectrum disorders (ASDs), and the most common monogenetic inheritable form of ASDs is Fragile X Syndrome (FXS). Previous studies indicate that FXS is linked to glutamate signaling regulation by the G-protein-coupled metabotropic glutamate receptor 5 (mGluR5), which has been shown to have a regulatory role in neuroinflammation. We characterized the effect of knocking out mGluR5 in an organism known to have complex cognitive functions—the rat. The heterozygous phenotype is the most clinically relevant; therefore, we performed analysis in heterozygous pups. We showed developmental abnormalities in heterozygous mGluR5 knockout rats, as well as a significant increase in chemokine (C-X-C motif) ligand 1 (CXCL) expression, a hallmark indicator of early onset inflammation. We quantified an increase in microglial density in the knockout pups and quantified morphological phenotypes representative of greater reactivity in the male vs. female and postnatal day 28 heterozygous pups compared to postnatal day 14 heterozygous pups. In response to injury, reactive microglia release matrix metalloproteases, contribute to extracellular matrix (ECM) breakdown, and are responsible for eradicating cellular and molecular debris. In our study, the changes in microglial density and reactivity correlated with abnormalities in the mRNA expression levels of ECM proteins and with the density of perineuronal nets. We saw atypical neuropsychiatric behavior in open field and elevated plus tests in heterozygous pups compared to wild-type litter and age-matched controls. These results demonstrate the pathological potential of the mGluR5 knockout in rats and further support the presence of neuroinflammatory roots in ASDs.
... Apart from oncology, neurology is the most prevalent domain of research that has benefited from results obtained by ex vivo metabolic NMR analysis. This is also true for studies of metabolic profiles of brain extracts from animal models, such as models of multiple sclerosis and mental retardation [78][79][80]. Moreover, the metabolome of neural and other stem cells has been investigated by tissue extracts and static cell suspension, in order to study the multidrug resistance of stem cells in general, and the metabolism of pluripotent embryonic stem cells in particular [8,53,[81][82][83]. ...
This is a broad overview and critical review of a particular group of closely related ex vivo and in vitro metabolic NMR spectroscopic methods. The scope of interest comprises studies of cultured cells and excised tissue, either intact or after physicochemical extraction of metabolites. Our detailed discussion includes pitfalls that have led to erroneous statements in the published literature, some of which may cause serious problems in metabolic and biological interpretation of results. To cover a wide range of work from relevant research areas, we consider not only the most recent achievements in the field, but also techniques that proved to be valid and successful in the past, although they may not have generated a very significant number of papers more recently. Thus, this comparative review also aims at providing background information useful for judiciously choosing between the metabolic ex vivo/in vitro NMR methods presented. Finally, the methods of interest are discussed in the context of, and in relation to, other metabolic analysis protocols such as HR-MAS and cell perfusion NMR, as well as the mass spectrometry approach.
... In support of these assumptions, increased energy expenditure and intensified ATP turnover were brought to light in neonatal hippocampal Mecp2 −/y neurons [59], and a mitochondrial energy-wasting status has been proposed for RTT [60]. This may explain why decreased ATP levels were found in full brain-analyses on male and female Mecp2-mutant mice [21,61]. However, focusing on adult Mecp2 −/y hippocampus, we did not observe decreased ATP levels in that specific brain region [53]. ...
Using unsupervised metabolomics, we defined the complex metabolic conditions in the cortex of a mouse model of Rett syndrome (RTT). RTT, which represents a cause of mental and cognitive disabilities in females, results in profound cognitive impairment with autistic features, motor disabilities, seizures, gastrointestinal problems, and cardiorespiratory irregularities. Typical RTT originates from mutations in the X-chromosomal methyl-CpG-binding-protein-2 (Mecp2) gene, which encodes a transcriptional modulator. It then causes a deregulation of several target genes and metabolic alterations in the nervous system and peripheral organs. We identified 101 significantly deregulated metabolites in the Mecp2-deficient cortex of adult male mice; 68 were increased and 33 were decreased compared to wildtypes. Pathway analysis identified 31 mostly upregulated metabolic pathways, in particular carbohydrate and amino acid metabolism, key metabolic mitochondrial/extramitochondrial pathways, and lipid metabolism. In contrast, neurotransmitter-signaling is dampened. This metabolic fingerprint of the Mecp2-deficient cortex of severely symptomatic mice provides further mechanistic insights into the complex RTT pathogenesis. The deregulated pathways that were identified—in particular the markedly affected amino acid and carbohydrate metabolism—confirm a complex and multifaceted metabolic component in RTT, which in turn signifies putative therapeutic targets. Furthermore, the deregulated key metabolites provide a choice of potential biomarkers for a more detailed rating of disease severity and disease progression.
... Abnormalities of mitochondria were found in patients with Rett syndrome, a syndromic form of ASD caused by mutations in MECP2 [51,59]. Rett syndrome patients have impaired mitochondria and redox function [60], mitochondrial genes are differentially expressed in Rett patients [61], with reduced ATP concentrations [62]. Our data expand on these observations found through a combination of patient samples, animal models, and traditional 2-D cellular cultures by using 3-D cerebral organoids in conjunction with traditional transcriptional studies, with single-cell RNAseq, and Nanopore sequencing to examine RNA base modifications, to examine how early environmental exposure can exacerbate genetically predisposed intellectual disabilities. ...
Autism spectrum disorder (ASD) manifests early in childhood. While genetic variants increase risk for ASD, a growing body of literature has established that in utero chemical exposures also contribute to ASD risk. These chemicals include air-based pollutants like diesel particulate matter (DPM). A combination of single-cell and direct transcriptomics of DPM-exposed human-induced pluripotent stem cell-derived cerebral organoids revealed toxicogenomic effects of DPM exposure during fetal brain development. Direct transcriptomics, sequencing RNA bases via Nanopore, revealed that cerebral organoids contain extensive RNA modifications, with DPM-altering cytosine methylation in oxidative mitochondrial transcripts expressed in outer radial glia cells. Single-cell transcriptomics further confirmed an oxidative phosphorylation change in cell groups such as outer radial glia upon DPM exposure. This approach highlights how DPM exposure perturbs normal mitochondrial function and cellular respiration during early brain development, which may contribute to developmental disorders like ASD by altering neurodevelopment.
... This includes dampened activities of cytochrome c oxidase and succinate cytochrome c reductase [17][18][19][20][21], a diminished mitochondrial membrane potential (ΔΨm), a higher degree of FAD/-NADH oxidation, increased levels of reactive oxygen species (ROS), as well as intensified ATP turnover rates [22][23][24]. In whole-brain analyses of adult male and female MeCP2-deficient mice even lower cellular ATP contents were confirmed [20,21,25]. ...
The neurodevelopmental disorder Rett syndrome (RTT) affects mostly females. Upon an apparently normal initial development, cognitive impairment, irregular breathing, motor dysfunction, and epilepsy occur. The complex pathogenesis includes, among others, mitochondrial impairment, redox imbalance, and oxidative damage. As these arise already in neonatal Rett mice, they were proposed contributors of disease progression. Several mitochondrial studies in RTT used either full brains or selected brain regions only. Here, we mapped mitochondria-related ROS generation brain wide. Using sophisticated multi-sample spectrofluorimetry, H2O2 release by isolated mitochondria was quantified in a coupled reaction of Amplex UltraRed and horseradish peroxidase. All brain regions and the entire lifespan were characterized in male and female mice. In WT mice, mitochondrial H2O2 release was usually highest in cortex and lowest in hippocampus. Maximum rates occurred at postnatal day (PD) 10 and they slightly declined with further maturation. Already at PD 10, male and female Rett mice showed exaggerated mitochondrial H2O2 releases in first brain regions and persistent brain-wide increases from PD 50 on. Interestingly, female Rett mice were more intensely affected than male Rett mice, with their brainstem, midbrain and hippocampus being most severely struck. In conclusion, we used a reliable multi-sample cuvette-based assay on mitochondrial ROS release to perform brain-wide analyzes along the entire lifespan. Mitochondrial H2O2 release in Rett mice is intensified in all brain regions, affects hemizygous males and heterozygous females, and involves all maturational stages. Therefore, intensified mitochondrial H2O2 release seriously needs to be considered throughout RTT pathogenesis and may constitute a potential therapeutic target.
... Structural brain anomalies were also described in mouse models of DBDs. Indeed, reduced volume of cerebellum as well as reduced thickness of corpus callosum were observed in Mecp2-null mice [31], while the Fragile X syndrome mouse model exhibits an increased volume of the parieto-temporal lobe and a smaller striatum [32]. To investigate whether such anatomical defects are present in the Mir146a −/− mice, we performed magnetic resonance imaging (MRI) studies at P30, the earliest stage that allows us to measure the volume of the cortex and the hippocampus. ...
Background:
Formation and maintenance of appropriate neural networks require tight regulation of neural stem cell proliferation, differentiation, and neurogenesis. microRNAs (miRNAs) play an important role in brain development and plasticity, and dysregulated miRNA profiles have been linked to neurodevelopmental disorders including autism, schizophrenia, or intellectual disability. Yet, the functional role of miRNAs in neural development and postnatal brain functions remains unclear.
Methods:
Using a combination of cell biology techniques as well as behavioral studies and brain imaging, we characterize mouse models with either constitutive inactivation or selectively hippocampal knockdown of the neurodevelopmental disease-associated gene Mir146a, the most commonly deregulated miRNA in developmental brain disorders (DBD).
Results:
We first show that during development, loss of miR-146a impairs the differentiation of radial glial cells, neurogenesis process, and neurite extension. In the mouse adult brain, loss of miR-146a correlates with an increased hippocampal asymmetry coupled with defects in spatial learning and memory performances. Moreover, selective hippocampal downregulation of miR-146a in adult mice causes severe hippocampal-dependent memory impairments indicating for the first time a role for this miRNA in postnatal brain functions.
Conclusion:
Our results show that miR-146a expression is critical for correct differentiation of neural stem cell during brain development and provide for the first time a strong argument for a postnatal role of miR-146a in regulating hippocampal-dependent memory. Furthermore, the demonstration that the Mir146a-/- mouse recapitulates several aspects reported in DBD patients, including impaired neurogenesis, abnormal brain anatomy, and working and spatial memories deficits, provides convincing evidence that the dysregulation of miR146a contributes to the pathogenesis of DBDs.
... Several reports provide an insight into mitochondrial dysfunction in brain of MeCP2 null mouse and Rett syndrome patients reviewed in detail by Shulyakova et al. (2017). Altered mitochondrial respiratory chain complex genes, proteins, and enzyme activities, and reduced ATP level have also been documented in RTT condition (Kriaucionis et al. 2006;Pecorelli et al. 2013;Gold et al. 2014;Valenti et al. 2017;De Filippis et al. 2015;Li et al. 2013;Saywell et al. 2006;Gibson et al. 2010;Jin et al. 2015). It has been suggested that progressive deterioration of motor functions and brain dysfunction in RTT may be related to the ROS overproduction and that potentially contribute to RTT-like symptoms (De Filippis et al. 2015;Kriaucionis et al. 2006). ...
Astrocytes play the central role in CNS metabolism to support neuronal functions. Mehyl-CpG-binding protein 2 (MeCP2) is the global transcription factor with differential expression in neuronal and non-neuronal cells. MeCP2 mutation and downstream detrimental effects have been reported in astrocytes also in MeCP2-associated neurodevelopmental disorder-Rett syndrome. Several studies have shown mitochondrial impairment linked to ROS production and reduced ATP synthesis in Rett patients and models, but consequences of MeCP2 deficiency on mitochondrial electron transport chain complexes in astrocytes and effect of known antioxidant quercetin aglycone has not yet been reported. The present study aimed to investigate effect of quercetin on mitochondrial functioning in MeCP2-deficient astrocytes. Our data show onefold upregulated Uqcrc1 and Ndufv2 gene expression, subtle change in protein expression, and significantly reduced mitochondrial respiratory chain complex-II and complex-III enzyme activities in MeCP2 knock-down astrocytes. Intracellular calcium robustly increased and mitochondrial membrane potential decreased, while no change in ROS was observed in MeCP2 knock-down astrocytes. Quercetin increased MeCP2 and normalized Uqcrc1 and Ndufv2 gene expression but did not modulate MeCP2 and Ndufv2 proteins expression. Interestingly, quercetin upregulated significantly the mitochondrial respiratory complex-II, complex-III, and complex-IV activities in dose-dependent manner. It also restored intracellular calcium level and mitochondrial membrane potential. In vitro observations suggest the beneficial effect of quercetin in mitochondrial functioning in MeCP2-deficient condition. There are no reports focusing on role of quercetin in mitochondrial function in MeCP2-deficient astrocytes, and these observations serve as preliminary data to evaluate quercetin’s effects in vivo.
... To our knowledge, it is unclear whether RTT patients are deficient in choline. Some studies reported elevated levels of choline, while others found no difference in choline levels with respect to controls [48][49][50][51][52][53]. We showed here that choline's rescue of RTT deficits may not be as straightforward as restoring cholinergic function as previously thought [18,19]. ...
Rett syndrome (RTT) is a postnatal neurodevelopmental disorder that primarily affects girls, with 95% of RTT cases resulting from mutations in the methyl-CpG-binding protein 2 (MECP2) gene. Choline, a dietary micronutrient found in most foods, has been shown to be important for brain development and function. However, the exact effects and mechanisms are still unknown. We found that 13 mg/day (1.7 × required daily intake) of postnatal choline treatment to Mecp2-conditional knockout mice rescued not only deficits in motor coordination, but also their anxiety-like behaviour and reduced social preference. Cortical neurons in the brains of Mecp2-conditional knockout mice supplemented with choline showed enhanced neuronal morphology and increased density of dendritic spines. Modelling RTT in vitro by knocking down the expression of the MeCP2 protein with shRNA, we found that choline supplementation to MeCP2-knockdown neurons increased their soma sizes and the complexity of their dendritic arbors. Rescue of the morphological defects could lead to enhanced neurotransmission, as suggested by an observed trend of increased expression of synaptic proteins and restored miniature excitatory postsynaptic current frequency in choline-supplemented MeCP2-knockdown neurons. Through the use of specific inhibitors targeting each of the known physiological pathways of choline, synthesis of phosphatidylcholine from choline was found to be essential in bringing about the changes seen in the choline-supplemented MeCP2-knockdown neurons. Taken together, these data reveal a role of choline in modulating neuronal plasticity, possibly leading to behavioural changes, and hence, a potential for using choline to treat RTT.
... The measurement of GABA is technically demanding due to its low concentration and complex resonance splitting pattern but can be quantified at field strengths above 7 T if SNR is sufficient and spectra are well-shimmed. At lower field strengths, e.g., 3 T, specialized editing techniques such as MEGAPRESS are required [177]. ...
As we enter the post-genomic era, understanding the role and function of single or group of genes in the context of a whole functioning organism, has become paramount in terms of human health. Much of this work is being carried out in rodent models of diseases, requiring the use of in vivo non-invasive imaging techniques to study the animals. Here we review the use of magnetic resonance imaging (MRI) and multi-nuclear magnetic resonance spectroscopy (MRS) for the phenotypic characterization of the ever increasing numbers of murine models of health and disease. We describe the current MRI and MRS strategies being applied to the characterization of these models and point out potential pitfalls and limitations of the available techniques. Finally, we review the latest advances in MRI and MRS and their potential application to pre-clinical studies.
... Brain magnetic resonance imaging in Mecp2-/y mice detected a significant reduction in the thickness of the corpus callosum (Saywell et al. 2006). Diffusion tensor imaging (DTI) studies in Rett syndrome patients also found a significant reduction in fractional anisotropy (FA) in the corpus callosum (Mahmood et al. 2010). ...
avMethyl‑CpG binding protein 2 (MeCP2) is an epigenetic regulator, which preferentially binds to methylated CpG dinucleotides in DNA. MeCP2 mutations have been linked to Rett syndrome, a neurodevelopmental disorder characterized by severe intellectual disability in females. Earlier studies indicated that loss of MeCP2 function in neuronal cells was the sole cause of Rett syndrome. Subsequent studies have linked MeCP2 expression in CNS glial cells to Rett syndrome pathogenesis. In this review, we have discussed the role of MeCP2 in glial subtypes, astrocytes, oligodendrocytes and microglia, and how loss of MeCP2 function in these cells has a profound influence on both glial and neuronal function.
... Obvious consequence of these mitochondrial changes is a less efficient respiratory chain and thus limited ATP synthesis. Indeed, magnetic resonance tomography and biochemical assays confirmed reduced brain ATP levels in male and female Mecp2mutant mice [26,33]. In view of the severe respiratory disturbances and frequent apneas in Rett patients [34][35][36], systemic hypoxia may occur and challenge mitochondrial function further. ...
Rett syndrome (RTT) is a neurodevelopmental disorder with mutations in the MECP2 gene. Mostly girls are affected, and an apparently normal development is followed by cognitive impairment, motor dysfunction, epilepsy, and irregular breathing. Various indications suggest mitochondrial dysfunction. In Rett mice, brain ATP levels are reduced, mitochondria are leaking protons, and respiratory complexes are dysregulated. Furthermore, we found in MeCP2-deficient mouse ( Mecp2 −/y ) hippocampus an intensified mitochondrial metabolism and ROS generation. We now used emission ratiometric 2-photon imaging to assess mitochondrial morphology, mass, and membrane potential (ΔΨm) in Mecp2 −/y hippocampal astrocytes. Cultured astrocytes were labeled with the ΔΨm marker JC-1, and semiautomated analyses yielded the number of mitochondria per cell, their morphology, and ΔΨm. Mecp2 −/y astrocytes contained more mitochondria than wild-type (WT) cells and were more oxidized. Mitochondrial size, ΔΨm, and vulnerability to pharmacological challenge did not differ. The antioxidant Trolox opposed the oxidative burden and decreased the mitochondrial mass, thereby dampening the differences among WT and Mecp2 −/y astrocytes; mitochondrial size and ΔΨm were not markedly affected. In conclusion, mitochondrial alterations and redox imbalance in RTT also involve astrocytes. Mitochondria are more numerous in Mecp2 −/y than in WT astrocytes. As this genotypic difference is abolished by Trolox, it seems linked to the oxidative stress in RTT.
... Previous MRI studies of human RTT patients have identified volume loss in frontal gray matter, basal ganglia, substantia nigra, midbrain, cerebellum, and brainstem [37][38][39]. MRI studies of Mecp2-null mice also show volume reductions in many of the same regions as humans, suggesting that these models recapitulate the gross anatomical impairments of the human phenotype [40,41]. However, these studies limited their analyses to a few regions of interest only providing a snapshot of the profile of volumetric changes within the Mecp2 disrupted brain. ...
Background
Rett syndrome (RTT) is a neurodevelopmental disorder that predominantly affects girls. The majority of RTT cases are caused by de novo mutations in methyl-CpG-binding protein 2 (MECP2), and several mouse models have been created to further understand the disorder. In the current literature, many studies have focused their analyses on the behavioral abnormalities and cellular and molecular impairments that arise from Mecp2 mutations. However, limited efforts have been placed on understanding how Mecp2 mutations disrupt the neuroanatomy and networks of the brain.
Methods
In this study, we examined the neuroanatomy of male and female mice from the Mecp2tm1Hzo, Mecp2tm1.1Bird/J, and Mecp2tm2Bird/J mouse lines using high-resolution magnetic resonance imaging (MRI) paired with deformation-based morphometry to determine the brain regions susceptible to Mecp2 disruptions.
Results
We found that many cortical and subcortical regions were reduced in volume within the brains of mutant mice regardless of mutation type, highlighting regions that are susceptible to Mecp2 disruptions. We also found that the volume within these regions correlated with behavioral metrics. Conversely, regions of the cerebellum were differentially affected by the type of mutation, showing an increase in volume in the mutant Mecp2tm1Hzo brain relative to controls and a decrease in the Mecp2tm1.1Bird/J and Mecp2tm2Bird/J lines.
Conclusions
Our findings demonstrate that the direction and magnitude of the neuroanatomical differences between control and mutant mice carrying Mecp2 mutations are driven by the severity of the mutation and the stage of behavioral impairments.
... The measurement of GABA is technically demanding due to its low concentration and complex resonance splitting pattern but can be quantified at field strengths above 7 T if SNR is sufficient and spectra are well-shimmed. At lower field strengths, e.g., 3 T, specialized editing techniques such as MEGAPRESS are required [177]. ...
As we enter the post-genomic era, understanding the role and function of single or group of genes in the context of a whole functioning organism, has become paramount in terms of human health. Much of this work is being carried out in rodent models of diseases, requiring the use of in vivo non-invasive imaging techniques to study the animals. Here we review the use of magnetic resonance imaging (MRI) and multi-nuclear magnetic resonance spectroscopy (MRS) for the phenotypic characterization of the ever increasing numbers of murine models of health and disease. We describe the current MRI and MRS strategies being applied to the characterization of these models and point out potential pitfalls and limitations of the available techniques. Finally, we review the latest advances in MRI and MRS and their potential application to pre-clinical studies.
... The altered circulating levels of carnitine and/or acyl-carnitine (i.e., phenotypes suggestive of deficiencies in the long-chain FAO) present in RTT children would support this hypothesis 20,32 . As a consequence of these mitochondrial alterations, mitochondrial energy production would be less efficient and lead to reduced ATP levels, as detected in a magnetic resonance study on Mecp2-deficient mice 10 . Although these data are indicative of widespread mitochondrial dysfunction, the cause of defective mitochondria is unclear, and it remains to be determined whether and how alterations in the mitochondrial metabolic pathways are involved in the pathogenesis of autism spectrum disorders and cause functional impairment of organs, as in the case of cardiac dysfunction observed in both RTT patients and animal models 8,32,43 . ...
... The altered circulating levels of carnitine and/or acyl-carnitine (i.e., phenotypes suggestive of deficiencies in the long-chain FAO) present in RTT children would support this hypothesis 20,32 . As a consequence of these mitochondrial alterations, mitochondrial energy production would be less efficient and lead to reduced ATP levels, as detected in a magnetic resonance study on Mecp2-deficient mice 10 . Although these data are indicative of widespread mitochondrial dysfunction, the cause of defective mitochondria is unclear, and it remains to be determined whether and how alterations in the mitochondrial metabolic pathways are involved in the pathogenesis of autism spectrum disorders and cause functional impairment of organs, as in the case of cardiac dysfunction observed in both RTT patients and animal models 8,32,43 . ...
Rett syndrome (RTT) is a neurodevelopmental disease that leads to intellectual deficit, motor disability, epilepsy and increased risk of sudden death. Although in up to 95% of cases this disease is caused by de novo loss-of-function mutations in the X-linked methyl-CpG binding protein 2 gene, it is a multisystem disease associated also with mitochondrial metabolic imbalance. In addition, the presence of long QT intervals (LQT) on the patients’ electrocardiograms has been associated with the development of ventricular tachyarrhythmias and sudden death. In the attempt to shed light on the mechanism underlying heart failure in RTT, we investigated the contribution of the carnitine cycle to the onset of mitochondrial dysfunction in the cardiac tissues of two subgroups of RTT mice, namely Mecp2+/− NQTc and Mecp2+/− LQTc mice, that have a normal and an LQT interval, respectively. We found that carnitine palmitoyltransferase 1 A/B and carnitine acylcarnitine translocase were significantly upregulated at mRNA and protein level in the heart of Mecp2+/− mice. Moreover, the carnitine system was imbalanced in Mecp2+/− LQTc mice due to decreased carnitine acylcarnitine transferase expression. By causing accumulation of intramitochondrial acylcarnitines, this imbalance exacerbated incomplete fatty acid oxidation, which, in turn, could contribute to mitochondrial overload and sudden death.
... Brain-derived neurotrophic factor (BDNF) is one of the most studied target genes whose expression is modulated by MeCP2 and involved in neuronal survival, differentiation, synaptic plasticity, and myelination. Brain magnetic resonance study in Mecp2-/y mice detected a significant reduction in the thickness of the corpus callosum which shows that white matter is affected in Rett syndrome (Saywell et al. 2006). Furthermore, it has been shown that myelin gene expression are altered in MeCP2-null mice (Nguyen et al. 2013;Vora et al. 2010). ...
Methyl CpG binding protein 2 (MeCP2) is a multifunctional protein which binds to methylated CpG, mutation of which cause a neurodevelopmental disorder, Rett syndrome. MeCP2 can function as both transcriptional activator and repressor of target gene. MeCP2 regulate gene expression in both neuron and glial cells in central nervous system (CNS). Oligodendrocytes, the myelinating cells of CNS, are required for normal functioning of neurons and are regulated by several transcription factors during their differentiation. In current study, we focused on the role of MeCP2 as transcription regulator of myelin genes in cultured rat oligodendrocytes. We have observed expression of MeCP2 at all stages of oligodendrocyte development. MeCP2 knockdown in cultured oligodendrocytes by small interference RNA (siRNA) has shown increase in myelin genes (myelin basic protein (MBP), proteolipid protein (PLP), myelin oligodendrocyte glycoprotein (MOG), and myelin-associated oligodendrocyte basic protein (MOBP)), neurotrophin (brain-derived neurotrophic factor (BDNF)), and transcriptional regulator (YY1) transcripts level, which are involved in regulation of oligodendrocyte differentiation and myelination. Further, we also found that protein levels of MBP, PLP, DM-20, and BDNF also significantly upregulated in MeCP2 knockdown oligodendrocytes. Our study suggests that the MeCP2 acts as a negative regulator of myelin protein expression.
... Previous MRI examinations of the Mecp2 mouse have reported findings of decreased total brain volume and cerebellar a motor cortex decreases are consistent with the absolute volume differences in the Mecp2 308 model used here. 47,48 A recent study on the BTBR mouse model 49 is in good agreement with the results BTBR (vs B6) mice shown here, 22 including reductions in the fronto-cortical areas and thalamus, and increases in hippocampus and cerebellum. Another recent study by Portmann et al. ...
Autism is a heritable disorder, with over 250 associated genes identified to date, yet no single gene accounts for 41–2% of cases. The clinical presentation, behavioural symptoms, imaging and histopathology findings are strikingly heterogeneous. A more complete understanding of autism can be obtained by examining multiple genetic or behavioural mouse models of autism using magnetic resonance imaging (MRI)-based neuroanatomical phenotyping. Twenty-six different mouse models were examined and the consistently found abnormal brain regions across models were parieto-temporal lobe, cerebellar cortex, frontal lobe, hypothalamus and striatum. These models separated into three distinct clusters, two of which can be linked to the under and overconnectivity found in autism. These clusters also identified previously unknown connections between Nrxn1α, En2 and Fmr1; Nlgn3, BTBR and Slc6A4; and also between X monosomy and Mecp2. With no single treatment for autism found, clustering autism using neuroanatomy and identifying these strong connections may prove to be a crucial step in predicting treatment response.
... Functionally impaired and less efficient mitochondria may result in lower brain ATP levels, which were indeed detected by MRI in Mecp2 − /y mice [33]. Yet, in adult MeCP2-deficient hippocampus, we found normal ATP content [34], which suggests a compensatory stimulation of mitochondrial respiration to guarantee proper ATP supply. ...
RTT (Rett syndrome) is a severe progressive neurodevelopmental disorder with a monogenetic cause, but complex and multifaceted clinical appearance. Compelling evidence suggests that mitochondrial alterations and aberrant redox homoeostasis result in oxidative challenge. Yet, compared with other severe neuropathologies, RTT is not associated with marked neurodegeneration, but rather a chemical imbalance and miscommunication of neuronal elements. Different pharmacotherapies mediate partial improvement of conditions in RTT, and also antioxidants or compounds improving mitochondrial function may be of potential merit. In the present paper, we summarize findings from patients and transgenic mice that point towards the nature of RTT as a mitochondrial disease. Also, open questions are addressed that require clarification to fully understand and successfully target the associated cellular redox imbalance.
... RTT's main cause are mutations in the MECP2 gene that encodes a transcriptional regulator (Amir et al., 1999). Postmortem studies revealed a decrease in neuronal size and dendritic arborization in the brain of RTT individuals with increased cell density and global reduction in brain volume (Belichenko et al., 1994(Belichenko et al., , 2009Subramaniam et al., 1997;Kaufmann and Moser, 2000;Armstrong, 2001;Akbarian, 2002;Saywell et al., 2006). The pathological process leading to these features is still unclear and recent studies in animal models of RTT using conditional Mecp2 knock-out in adult mice have challenged the idea of a developmental failure by suggesting the hypothesis of a deficit in the maintenance of the dendritic arbor structure (Schule et al., 2008;Matijevic et al., 2009). ...
Rett Syndrome (RTT) is a neurodevelopmental disorder associated with intellectual disability, mainly caused by loss-of-function mutations in the MECP2 gene. RTT brains display decreased neuronal size and dendritic arborization possibly caused by either a developmental failure or a deficit in the maintenance of dendritic arbor structure. To distinguish between these two hypotheses, the development of Mecp2-knockout mouse hippocampal neurons was analyzed in vitro. Since a staging system for the in vitro development of mouse neurons was lacking, mouse and rat hippocampal neurons development was compared between 1-15 days in vitro (DIV) leading to a 6-stage model for both species. Mecp2-knockout hippocampal neurons displayed reduced growth of dendritic branches from stage 4 (DIV4) onwards. At stages 5-6 (DIV9-15), synapse number was lowered in Mecp2-knockout neurons, suggesting increased synapse elimination. These results point to both a developmental and a maintenance setback affecting the final shape and function of neurons in RTT.
... It is possible to speculate that increased genes related to mitochondrial subunits could be a consequence of increased cells request of energy (ATP). This hypothesis is in line with recent study where the authors have shown decreased levels of ATP in brain mouse RTT [34]. ...
Rett syndrome (RTT) is mainly caused by mutations in the X-linked methyl-CpG binding protein (
MeCP2
) gene. By binding to methylated promoters on CpG islands, MeCP2 protein is able to modulate several genes and important cellular pathways. Therefore, mutations in
MeCP2
can seriously affect the cellular phenotype. Today, the pathways that
MeCP2
mutations are able to affect in RTT are not clear yet. The aim of our study was to investigate the gene expression profiles in peripheral blood lymphomonocytes (PBMC) isolated from RTT patients to try to evidence new genes and new pathways that are involved in RTT pathophysiology. LIMMA (Linear Models for MicroArray) and SAM (Significance Analysis of Microarrays) analyses on microarray data from 12 RTT patients and 7 control subjects identified 482 genes modulated in RTT, of which 430 were upregulated and 52 were downregulated. Functional clustering of a total of 146 genes in RTT identified key biological pathways related to mitochondrial function and organization, cellular ubiquitination and proteosome degradation, RNA processing, and chromatin folding. Our microarray data reveal an overexpression of genes involved in ATP synthesis suggesting altered energy requirement that parallels with increased activities of protein degradation. In conclusion, these findings suggest that mitochondrial-ATP-proteasome functions are likely to be involved in RTT clinical features.
... Neuroanatomical studies of brain areas affected in Rett patients reported a reduction in overall brain volume and atrophy in regions associated with motor function including the caudate nucleus [9] and cerebellum [10,11]. Mecp2 null mice also display abnormalities in the cerebellum and motor cortex [12] and suggest this to be a mechanism for behaviourally recorded reductions in locomotor activity in the open-field [13][14][15][16]. However, it is conceivable that reduced ambulatory activity may not be a direct indicator of locomotion, but instead reflects altered anxiety levels in response to the novel environment, and this would be in agreement with previous studies providing compelling evidence that Mecp2 deficient mice have heightened levels of anxiety [6,13,[17][18][19][20][21][22][23]. ...
Numerous experimental models have been developed to reiterate endophenotypes of Rett syndrome, a neurodevelopmental disorder with a multitude of motor, cognitive and vegetative symptoms. Here, female Mecp2Stop mice [1] were characterised at mild symptomatic conditions in tests for anxiety (open field, elevated plus maze) and home cage observation systems for food intake, locomotor activity and circadian rhythms.
Aged 8–9 months, Mecp2Stop mice presented with heightened body weight, lower overall activity in the open field, but no anxiety phenotype. Although home cage activity scans conducted in two different observation systems, PhenoMaster and PhenoTyper, confirmed normal circadian activity, they revealed severely compromised habituation to a novel environment in all parameters registered including those derived from a non-linear decay model such as initial exploration maximum, decay half-life of activity and span, as well as plateau. Furthermore, overall activity was significantly reduced in nocturnal periods due to reductions in both fast ambulatory movements, but also a slow lingering. In contrast, light-period activity profiles during which the amount of sleep was highest remained normal in Mecp2Stop mice.
These data confirm the slow and progressive development of Rett-like symptoms in female Mecp2Stop mice resulting in a prominent reduction of overall locomotor activity, while circadian rhythms are maintained. Alterations in the time-course of habituation may indicate deficiencies in cognitive processing.
Rett syndrome (RTT) is a severe neurodevelopmental disorder that typically arises from spontaneous germline mutations in the X-chromosomal methyl-CpG binding protein 2 (MECP2) gene. For the first 6–18 months of life, the development of the mostly female patients appears normal. Subsequently, cognitive impairment, motor disturbances, hand stereotypies, epilepsy, and irregular breathing manifest, with previously learned skills being lost. Early mitochondrial impairment and a systemic oxidative burden are part of the complex pathogenesis, and contribute to disease progression. Accordingly, partial therapeutic merits of redox-stabilizing and antioxidant (AO) treatments were reported in RTT patients and Mecp2-mutant mice. Pursuing these findings, we conducted a full preclinical trial on male and female mice to define the therapeutic value of an orally administered AO cocktail composed of vitamin E, N-acetylcysteine, and α-lipoic acid. AO treatment ameliorated some of the microcephaly-related aspects. Moreover, the reduced growth, lowered blood glucose levels, and the hippocampal synaptic plasticity of Mecp2−/y mice improved. However, the first-time detected intensified oxidative DNA damage in Mecp2-mutant cortex persisted. The behavioral performance, breathing regularity, and life expectancy of Mecp2-mutant mice did not improve upon AO treatment. Long-term-treated Mecp2+/− mice eventually became obese. In conclusion, the AO cocktail ameliorated a subset of symptoms of the complex RTT-related phenotype, thereby further confirming the potential merits of AO-based pharmacotherapies. Yet, it also became evident that long-term AO treatment may lose efficacy and even aggravate the metabolic disturbances in RTT. This emphasizes the importance of a constantly well-balanced redox balance for systemic well-being.
Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in the methyl‐CpG‐binding protein 2 (MeCP2) in the neurons and glial cells of the central nervous system. Currently, therapeutics for RTT is aimed at restoring the loss‐of‐function by MeCP2 gene therapy, but that approach has multiple challenges. We have already reported impaired mitochondrial bioenergetics in MeCP2 deficient astrocytes. Docosahexaenoic acid (DHA), a polyunsaturated fatty acid, has been shown with health benefits, but its impact on mitochondrial functions in MeCP2 deficient astrocytes has never been paid much attention. The present study aimed to investigate the effects of DHA on mitochondrial respiratory chain regulation in MeCP2 knockdown astrocytes. We determined NADH dehydrogenase (ubiquinone) flavoprotein 2 (Ndufv2‐complex‐I), Ubiquinol cytochrome c reductase core protein (Uqcrc1‐complex‐III) genes expression, Ndufv2 protein expression, respiratory electron transport chain complex I, II, III, and IV enzyme activities, intracellular Ca+2, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) in DHA pre‐incubated MeCP2 knock‐down rat primary cortical astrocytes. Our study demonstrates that 100 µM DHA increases MeCP2 gene and protein expression. Increases brain‐derived neurotrophic factor (BDNF) and Uqcrc1 gene expression, Ndufv2 protein expression, but has no effect on glial fibrillary acidic protein (GFAP) gene expression. DHA treatment also increases mitochondrial respiratory Complexes II and III activities and reduces intracellular calcium levels. Taken together, the effects of DHA seem independent of MeCP2 deficiency in astrocytes. Hence, further studies are warranted to understand the complicated mechanisms of DHA and for its therapeutic significance in MeCP2‐mediated mitochondrial dysfunction and in RTT disease. Role of DHA in MeCP2‐mediated mitochondrial dysfunction.
Rett syndrome (RTT) is a severe neurodevelopmental disorder characterized by loss of spoken language and hand use, characteristic repetitive hand stereotypies, and gait problems. RTT is usually caused by mutations in the X-linked gene methyl-CpG-binding protein 2 (MECP2). Extensive work has been performed to understand how MeCP2 dysfunction affects cells, circuits, physiology, and behavior. Promisingly, restoration of MeCP2 expression in symptomatic RTT mice reverses clinical phenotypes, suggesting that the disease will be modifiable if not fully reversible. This chapter reviews clinical features of RTT, the current understanding of the molecular, cellular, and circuit role of MeCP2, and approaches to therapy.
Les maladies du neurodéveloppement (MND) regroupent des pathologies caractérisées par des troubles de la cognition, de la communication, du comportement en conséquence d'un développement cérébral atypique. Les MND incluent la déficience intellectuelle (DI), les troubles du spectre autistique (TSA), le trouble du déficit de l'attention et les troubles de l'apprentissage. Avec une prévalence globale de 3%, les MND sont responsables de 10% des dépenses de santé dans les pays développés et constituent donc un défi médical et socioéconomique majeur. Les microARNs (miARNs) sont de petits ARNs non codant de ~20-22 nucléotides. Ils exercent une régulation post-transcriptionnelle de l'expression génique en dégradant ou réprimant la traduction d'ARNs messagers spécifiques. Chaque miARN ciblant plusieurs centaines de transcrits, ils constituent des médiateurs clés de l'expression génique. Les microARNs régulent la majorité des processus biologiques et notamment le développement cérébral. Plusieurs miARNs ont été associés à des pathologies neurologiques comme la maladie d'Alzheimer ou la sclérose latérale amyotrophique mais aussi à des MND telles que le TSA, la DI et l'épilepsie. Des études d'expression réalisées sur divers échantillons de patients TSA ont identifié miR-146a comme le miARN le plus fréquemment dérégulé. Une expression anormale de ce miARN a également été observée dans des cas de DI et d'épilepsie. Il est important de noter que moduler l'expression de miR-146a est suffisant pour réduire la latence, la durée et l'intensité des crises d'épilepsie induites dans des modèles rongeurs d'épilepsie télencéphalique. miR-146a est un régulateur connu des voies de signalisation NFκB, Notch et Wnt/β-caténine et a été associé à des cas de cancers et de maladies inflammatoires mais peu de choses sont connues sur ses fonctions dans le cerveau. Des travaux in vitro décrivent le rôle de miR-146a dans la survie et l'apoptose des neurones, la croissance axonale et l'endocytose des récepteurs AMPA. Notre groupe a également montré l'effet pro-neuronal de la sur-expression de miR-146a dans des cellules souches neurales humaines H9. Collectivement, ces données donnent un aperçu des fonctions de miR-146a dans des cellules en culture mais ne fournissent que peu d'informations quant à son rôle in vivo au cours du neurodéveloppement. Nous avons donc caractérisé la souris Mir146a-/- par des techniques d'imagerie, de biologie cellulaire et moléculaire ainsi que des études de comportement. Nous avons démontré que la neurogenèse est altérée dans les souris Mir146a-/-. Au jour embryonnaire 14 (E14), les embryons mutants ont plus de progéniteurs neuraux engagés vers un destin neuronal ainsi qu'un plus grand nombre de neurones post-mitotiques dans le néocortex. Grâce à des cultures de cellules primaires, nous avons montré que l'absence de miR-146a cause une augmentation de la croissance dendritique ainsi qu'une altération de la recapture du glutamate par les astrocytes et nous avons prouvé que le transporteur de glutamate GLT-1 est une cible directe de miR-146a. Des analyses transcriptomiques sur des échantillons de cerveau à E14, P30 et P60 indiquent que la perte de miR-146a affecte principalement les neurones. Enfin, des analyses par IRM et des études de comportement montrent une anatomie anormale de l'hippocampe ainsi qu'une altération des capacités d'apprentissage chez les souris mutantes. Ce travail décrit une des premières caractérisations du neurodéveloppement d'un modèle murin inactivé pour un miARN. Il montre que miR-146a est impliqué dans le contrôle de la balance entre renouvellement des progéniteurs neuraux et différentiation neuronale. Il démontre également que plusieurs signes retrouvés chez les patients comme l'altération de la neurogenèse, l'anatomie anormale du cerveau et les défauts d'apprentissage, sont également observés chez les souris Mir146a-/-, soulignant la pertinence de ce modèle pour l'étude des maladies du neurodéveloppement.
Rett syndrome (RTT) is a rare congenital disorder which in most cases (95%) is caused by methyl-CpG binding protein 2 (MECP2) mutations. RTT is characterized by regression in global development, epilepsy, autistic features, acquired microcephaly, habitual hand clapping, loss of purposeful hand skills, and autonomic dysfunctions. Although the literature has demonstrated decreased volumes of the cerebrum, cerebellum, and the caudate nucleus in RTT patients, surface-based brain morphology including cortical thickness and cortical gyrification analyses are lacking in RTT. We present quantitative surface- and voxel-based morphological measurements in young children with RTT and Rett-like syndrome (RTT-l) with MECP2 mutations. The 8 structural T1-weighted MR images were obtained from 7 female patients with MECP2 mutations (3 classic RTT, 2 variant RTT, and 2 RTT-l) (mean age 5.2 [standard deviation 3.3] years old). Our analyses demonstrated decreased total volumes of the cerebellum in RTT/RTT-l compared to gender- and age-matched controls (t (22)=-2.93, p =.008, Cohen's d = 1.27). In contrast, global cerebral cortical surface areas, global/regional cortical thicknesses, the degree of global gyrification, and global/regional gray and white matter volumes were not statistically significantly different between the two groups. Our findings, as well as literature findings, suggest that early brain abnormalities associated with RTT/RTT-l (with MECP2 mutations) can be detected as regionally decreased cerebellar volumes. Decreased cerebellar volume may be helpful for understanding the etiology of RTT/RTT-l.
Rett syndrome (RTT) is a rare neurodevelopmental disorder, characterized by severe behavioral and physiological symptoms. Mutations in the methyl CpG binding protein 2 gene (MECP2) cause more than 95% of classic cases, and currently there is no cure for this devastating disorder. Recently we have demonstrated that neurobehavioral and brain molecular alterations can be rescued in a RTT mouse model, by pharmacological stimulation of the brain serotonin receptor 7 (5-HT7R). This member of the serotonin receptor family, crucially involved in the regulation of brain structural plasticity and cognitive processes, can be stimulated by systemic repeated treatment with LP-211, a brain-penetrant selective agonist. The present study extends previous findings by demonstrating that LP-211 treatment (0.25 mg/kg, once per day for 7 days) rescues mitochondrial respiratory chain impairment, oxidative phosphorylation deficiency and the reduced energy status in the brain of heterozygous female mice from two highly validated mouse models of RTT (MeCP2-308 and MeCP2-Bird mice). Moreover, LP-211 treatment completely restored the radical species overproduction by brain mitochondria in the MeCP2-308 model and partially recovered the oxidative imbalance in the more severely affected MeCP2-Bird model. These results provide the first evidence that RTT brain mitochondrial dysfunction can be rescued targeting the brain serotonin receptor 7 and add compelling preclinical evidence of the potential therapeutic value of LP-211 as a pharmacological approach for this devastating neurodevelopmental disorder.
In the last 15 years a strong correlation between oxidative stress (OxS) and Rett syndrome (RTT), a rare neurodevelopmental disorder known to be caused in 95% of the cases, by a mutation in the methyl-CpG-binding protein 2 (MECP2) gene, has been well documented. Here, we revised, summarized and discussed the current knowledge on the role of lipid peroxidation byproducts, with special emphasis on 4-hydroxynonenal (4HNE), in RTT pathophysiology. The posttranslational modifications of proteins via 4HNE, known as 4HNE protein adducts (4NHE-PAs), causing detrimental effects on protein functions, appear to contribute to the clinical severity of the syndrome, since their levels increase significantly during the subsequent 4 clinical stages, reaching the maximum degree at stage 4, represented by a late motor deterioration. In addition, 4HNE-PA are only partially removed due to the compromised functionality of the proteasome activity, contributing therefore to the cellular damage in RTT. All this will lead to a characteristic subclinical inflammation, defined “OxInflammation”, derived by a positive feedback loop between OxS byproducts and inflammatory mediators that in a long run further aggravates the clinical features of RTT patients. Therefore, in a pathology completely orphan of any therapy, aiming 4HNE as a therapeutic target could represent a coadjuvant treatment with some beneficial impact in these patients.
This chapter examines the conditions to develop organism models of disease. It is focused on rare diseases because we demonstrate (Chap. 2) that autism is a common denominator to a set of rare diseases. We define the place of the organism models in the translational strategy. We suggest four criteria to improve the validity of organism models: (1) identical etiology in model and in paragon, (2) similar molecular signature, (3) comparable pathophysiological pathways, and (4) experimental analysis of the model must match clinical observations in paragon. We focus on the consequences of an approach examining together the clinical aspects of the disease and its biological correlates. The requirement for using different species to examine the different facets of a disease is discussed in a tissue-specific strategy.
A strong correlation between oxidative stress (OS) and Rett syndrome (RTT), a rare neurodevelopmental disorder affecting females in the 95% of the cases, has been well documented although the source of OS and the effect of a redox imbalance in this pathology has not been yet investigated. Using freshly isolated skin fibroblasts from RTT patients and healthy subjects, we have demonstrated in RTT cells high levels of H2O2 and HNE protein adducts. These findings correlated with the constitutive activation of NADPH-oxidase (NOX) and that was prevented by a NOX inhibitor and iron chelator pre-treatment, showing its direct involvement. In parallel, we demonstrated an increase in mitochondrial oxidant production, altered mitochondrial biogenesis and impaired proteasome activity in RTT samples. Further, we found that the key cellular defensive enzymes: glutathione peroxidase, superoxide dismutase and thioredoxin reductases activities were also significantly lower in RTT. Taken all together, our findings suggest that the systemic OS levels in RTT can be a consequence of both: increased endogenous oxidants as well as altered mitochondrial biogenesis with a decreased activity of defensive enzymes that leads to posttranslational oxidant proteins modification and a proteasome activity impairment.
Copyright © 2015. Published by Elsevier B.V.
Rett syndrome (RTT, MIM 312750), is a rare and orphan progressive neurodevelopmental disorder affecting almost exclusively the female gender with a frequency of 1:15,000 live births. The disease is characterized by a period of 6 to 18 months of apparently normal neurodevelopment, followed by an early neurological regression, with a progressive loss of acquired cognitive, social, and motor skills. RTT is known to be caused in the 95% of the cases by sporadic de novo loss-of-function mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene encoding methyl-CpG binding protein 2 (MeCP2), a nuclear protein able to regulates gene expression. Despite almost two decades of research into the functions and role of MeCP2, little is known about the mechanisms leading from MECP2 mutation to the disease.
Paternally and maternally inherited deletions and duplications of human chromosome 15q11-13 are relatively common in the human population. Furthermore, duplications in the 15q region are often associated with autism. Both maternal and paternal interstitial 15q11-13 duplication mouse models have been previously created, where several behavioral differences were found in the paternal duplication (patDp/+) mouse but not in the maternal duplication (matDp/+). These included decreased sociability, behavioral inflexibility, abnormal ultrasonic vocalizations, decreased spontaneous activity, and increased anxiety. Similarly, in the current study, we found several anatomical differences in the patDp/+ mice that were not seen in the matDp/+ mice. Regional differences that are evident only in the paternal duplication are a smaller dentate gyrus and smaller medial striatum. These differences may be responsible for the behavioral inflexibility. Furthermore, a smaller dorsal raphe nucleus could be responsible for the reported serotonin defects. This study highlights consistency that can be found between behavioral and anatomical phenotyping. Autism Res 2015. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.
© 2015 International Society for Autism Research, Wiley Periodicals, Inc.
Scientific literature on atypical development is so vast that a systematic review could not fit in some 40 pages; therefore, we had to make choices. First, we have limited our presentation to intellectual disability (ID), leaving aside behavioral and psychiatric disorders. After defining ID, the main causes are presented (genetic and environmental) with special emphasis on gene–environment correlations and/or interactions. We then selected two genetic disorders linked to ID (Phenylketonuria and Fragile X) to present both the research methodologies and the type of findings, before discussing the contribution of cross-syndrome comparisons. To uncover a causal link between genetic events and a behavioral phenotype, it is often essential to use model organisms. The advantage of such models, plus the requirements and limitations involved in their use, are presented before concluding the chapter
Folate and choline, two nutrients involved in the one-carbon metabolic cycle, are intimately involved in regulating DNA integrity, synthesis, biogenic amine synthesis, and methylation. In this review, we discuss evidence that folate and choline play an important role in normal cognitive development, and that altered levels of these nutrients during periods of high neuronal proliferation and synaptogenesis can result in diminished cognitive function. We also discuss the use of these nutrients as therapeutic agents in a spectrum of developmental disorders in which intellectual disability is a prominent feature, such as in Fragile-X, Rett syndrome, Down syndrome, and Autism spectrum disorders. A survey of recent literature suggests that nutritional supplements have mild, but generally consistent, effects on improving cognition. Intervening with supplements earlier rather than later during development is more effective in improving cognitive outcomes. Given the mild improvements seen after treatments using nutrients alone, and the importance of the genetic profile of parents and offspring, we suggest that using nutraceutics early in development and in combination with other therapeutics are likely to have positive impacts on cognitive outcomes in a broad spectrum of complex neurodevelopmental disorders.
Autism spectrum disorder(s) (ASDs) is a neurodevelopmental disorder characterized by stereotyped behaviours and impairments in communication and social interactions. This heterogeneity has been a major obstacle in uncovering the aetiology and biomarkers of ASDs. Rodent models with genetic modifications or environmental insults have been created to study particular endophenotypes and bridge the gap between genetics and behavioural phenotypes. Translational neuroimaging modalities with their ability to screen the brain noninvasively and yield structural, biochemical and functional information provide a unique platform for discovery and evaluation of such endophenotypes in preclinical and clinical research.
We reviewed literature on translational neuroimaging in rodent models of ASDs. The most prominent models will be described and the respective neuroimaging endophenotypes will be discussed with reference to human data. A perspective on future directions of translational neuroimaging in animal models of ASDs will be given.
To date, we experience a proliferation of rodent models which recapitulate specific liabilities identified in ASDs patients. Translational neuroimaging in these models is emerging but is skewed towards magnetic resonance imaging (MRI) modalities. Volumetric and structural assessments of the brain are dominating and a host of endophenotypes have been reported that allude to findings in ASDs patients but with only few to converge among the models. Caveats of current studies are the diverging biological conditions related to genetic background and age of the animals. It is anticipated that longitudinal and functional assessments will gain much importance and will help elucidating mechanistic relationship between behavioural and structural endophenotypes.
To test the specificity of N-acetylaspartate (NAA) as a neuronal marker for proton nuclear magnetic resonance (1H NMR) spectroscopy, purified and characterized cultured cells were analyzed for their NAA content using both 1H NMR and HPLC. Cell types studied included cerebellar granule neurons, type-1 astrocytes, meningeal cells, oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells, and oligodendrocytes. A high concentration of NAA was found in extracts of cerebellar granule neurons (approximately 12 nmol/mg of protein), whereas NAA remained undetectable in purified type-1 astrocytes, meningeal cells, and mature oligodendrocytes. However, twice the neuronal level of NAA was found in O-2A progenitors grown in vitro. In addition significant levels of NAA were also detected in cultures of immature oligodendrocytes. Our data partly support previous suggestions that NAA may be a useful neuronal marker for 1H NMR spectroscopic examination of the adult brain. However, they also raise the further possibility that alterations of NAA associated with some specific brain disorders, particularly disorders seen in newborn and young children, may reflect abnormalities in the development of oligodendroglia or their precursors.
Neuronal changes in the brain of a Rett syndrome patient were examined in a frontal lobe biopsy performed at age 3 years and in the postmortem brain at age 15 years. In the brain biopsy, frontal cortex contained numerous scattered pyramidal neurons with cytoplasmic vacuolation and increased cytoplasmic density, with no neuronophagia or inflammation detected; electron microscopy showed these neurons to have large, lucent-appearing mitochondria, very abundant ribosomal content, and some lipofuscin granules. Postmortem brain 12 years later showed scattered neurons in frontal cortex, substantia nigra, and cerebellar folia, with increased electron density of the cytoplasm, stacks of ribosomal endoplasmic reticulum, and large amounts of disorganized membranous material, including autophagic-type organelles. Mitochondria of these neurons contained electron-dense, finely granular matrix inclusions; in the substantia nigra, some spherical mitochondrial inclusions completely filled the matrix space. Golgi preparations of (autopsy) frontal cortex and cerebellar folia showed truncation and thickening of dendrites and a degenerate appearance of cortical pyramidal neurons, similar to changes found in aged brain. Synaptophysin immunohistochemistry indicated that the density of synapses was not greatly altered compared to controls in frontal cortex and cerebellum. The patient also had a second genetic defect, severe combined immunodeficiency with thymic aplasia, which may be X-linked.
Quantitative proton magnetic resonance spectroscopy was performed in frontal, parietal and occipital white and gray matter of young adults with use of a fully relaxed, short-echo time stimulated echo acquisition mode localization sequence at 2.0 T. Separate concentrations of the neuronal compounds N-acetylaspartate (NAA) and N-acetylaspartylglutamate (NAAG) were obtained by user-independent spectral analysis (LCModel). Except for occipital gray matter in which an NAA concentration of 10.1 +/- 1.0 mM correlated with enhanced neuronal density in visual cortex, NAA was found to be homogeneously distributed throughout cortical white and gray matter at a concentration of 8.0-8.9 mM. NAAG concentrations of 1.5-2.7 mM were higher in white matter than levels of 0.6-1.5 mM found in gray matter, contributing up to 25% of total N-acetyl-containing compounds. The frontal to parieto-occipital increase of both gray and white matter NAAG levels is also reflected in the distribution of total NAA.
Unlabelled:
Rett syndrome (RS), found exclusively in girls, is characterised by a global deceleration of psychomotor development, loss of acquired speech, loss of manual skills and subsequent deceleration of head growth. The cause of this syndrome is so far unknown. To date there are no biological markers for RS; clinical diagnostic criteria were proposed by the Rett Syndrome Diagnostic Criteria Work Group 1988. The first objective of this study was to assay the levels of very long-chain fatty acids (VLCFA), i.e. C22:0, C24:0, C26:0, by gas chromatography in sera of 30 girls with RS. The VLCFA levels in the studied group were lower than the reference range for healthy children and control group. VLCFA levels were again measured after 2 months of L-carnitine administration in the same groups. VLCFA levels had increased. It is possible that the low VLCFA levels have some relation to the lowered carnitine levels. It may be that low carnitine levels impede transportation to mitochondria, thus the oxidation of long-chain fatty acids is inhibited, and compensated to a certain extent by intensified beta-oxidation of VLCFA in the peroxisomal system. Raising carnitine levels could improve substrate delivery for mitochondrial beta-oxidation of long-chain fatty acids, thus reducing the use of VLCFA as substrates for beta-oxidation. We consider VLCFA to be secondary to the pathogenesis of RS, but the possible abnormalities in their levels may provide an insight into the development of this disease.
Conclusion:
Very long-chain fatty acid and carnitine levels are decreased in Rett syndrome L-Carnitine administration increased very long-chain fatty acid levels in serum.
Rett syndrome (RTT) is an inherited neurodevelopmental disorder of females that occurs once in 10,000-15,000 births. Affected females develop normally for 6-18 months, but then lose voluntary movements, including speech and hand skills. Most RTT patients are heterozygous for mutations in the X-linked gene MECP2 (refs. 3-12), encoding a protein that binds to methylated sites in genomic DNA and facilitates gene silencing. Previous work with Mecp2-null embryonic stem cells indicated that MeCP2 is essential for mouse embryogenesis. Here we generate mice lacking Mecp2 using Cre-loxP technology. Both Mecp2-null mice and mice in which Mecp2 was deleted in brain showed severe neurological symptoms at approximately six weeks of age. Compensation for absence of MeCP2 in other tissues by MeCP1 (refs. 19,20) was not apparent in genetic or biochemical tests. After several months, heterozygous female mice also showed behavioral symptoms. The overlapping delay before symptom onset in humans and mice, despite their profoundly different rates of development, raises the possibility that stability of brain function, not brain development per se, is compromised by the absence of MeCP2.
To investigate breathing rhythm and brain stem autonomic control in patients with Rett disorder.
Two university teaching hospitals in the United Kingdom and the Rett Centre, Sweden.
56 female patients with Rett disorder, aged 2-35 years; 11 controls aged 5-28 years.
One hour recordings of breathing movement, blood pressure, ECG R-R interval, heart rate, transcutaneous blood gases, cardiac vagal tone, and cardiac sensitivity to baroreflex measured on-line with synchronous EEG and video. Breathing rhythms were analysed in 47 cases.
Respiratory rhythm was normal during sleep and abnormal in the waking state. Forced and apneustic breathing were prominent among 5-10 year olds, and Valsalva breathing in the over 18 year olds, who were also most likely to breathe normally. Inadequate breathing peaked among 10-18 year olds. Inadequate and exaggerated breathing was associated with vacant spells. Resting cardiac vagal tone and cardiac sensitivity to baroreflex were reduced.
Labile respiratory rhythms and poor integrative inhibition in Rett disorder suggest brain immaturity. Linking this to an early monoaminergic defect suggests possible targets for the MECP2 gene in clinical intervention. Exaggerated and inadequate autonomic responses may contribute to sudden death.
Mutations in MECP2 are associated with Rett syndrome, an X-linked neurodevelopmental disorder. To identify genes targeted by Mecp2, we sequenced 100 in vivo Mecp2-binding sites in mouse brain. Several sequences mapped to an imprinted gene cluster on chromosome 6, including Dlx5 and Dlx6, whose transcription was roughly two times greater in brains of Mecp2-null mice compared with those of wild-type mice. The maternally expressed gene DLX5 showed a loss of imprinting in lymphoblastoid cells from individuals with Rett syndrome. Because Dlx5 regulates production of enzymes that synthesize gamma-aminobutyric acid (GABA), loss of imprinting of Dlx5 may alter GABAergic neuron activity in individuals with Rett syndrome. In mouse brain, Dlx5 imprinting was relaxed, yet Mecp2-mediated silent-chromatin structure existed at the Dlx5-Dlx6 locus in brains of wild-type, but not Mecp2-null, mice. Mecp2 targeted histone deacetylase 1 to a sharply defined, approximately 1-kb region at the Dlx5-Dlx6 locus and promoted repressive histone methylation at Lys9 at this site. Chromatin immunoprecipitation-combined loop assays showed that Mecp2 mediated the silent chromatin-derived 11-kb chromatin loop at the Dlx5-Dlx6 locus. This loop was absent in chromatin of brains of Mecp2-null mice, and Dlx5-Dlx6 interacted with far distant sequences, forming distinct active chromatin-associated loops. These results show that formation of a silent-chromatin loop is a new mechanism underlying gene regulation by Mecp2.
Rett syndrome (RTT) is a severe form of mental retardation, which is caused by spontaneous mutations in the X-linked gene
MECP2. How the loss of MeCP2 function leads to RTT is currently unknown. Mice lacking the Mecp2 gene initially show normal postnatal development but later acquire neurological phenotypes, including heightened anxiety,
that resemble RTT. The MECP2 gene encodes a methyl-CpG-binding protein that can act as a transcriptional repressor. Using cDNA microarrays, we found that
Mecp2-null animals differentially express several genes that are induced during the stress response by glucocorticoids. Increased
levels of mRNAs for serum glucocorticoid-inducible kinase 1 (Sgk) and FK506-binding protein 51 (Fkbp5) were observed before and after onset of neurological symptoms, but plasma glucocorticoid was not significantly elevated
in Mecp2-null mice. MeCP2 is bound to the Fkbp5 and Sgk genes in brain and may function as a modulator of glucocorticoid-inducible gene expression. Given the known deleterious effect
of glucocorticoid exposure on brain development, our data raise the possibility that disruption of MeCP2-dependent regulation
of stress-responsive genes contributes to the symptoms of RTT.
The first in vivo magnetic resonance study of experimental cerebral malaria is presented. Cerebral involvement is a lethal complication of malaria. To explore the brain of susceptible mice infected with Plasmodium berghei ANKA, multimodal magnetic resonance techniques were applied (imaging, diffusion, perfusion, angiography, spectroscopy). They reveal vascular damage including blood-brain barrier disruption and hemorrhages attributable to inflammatory processes. We provide the first in vivo demonstration for blood-brain barrier breakdown in cerebral malaria. Major edema formation as well as reduced brain perfusion was detected and is accompanied by an ischemic metabolic profile with reduction of high-energy phosphates and elevated brain lactate. In addition, angiography supplies compelling evidence for major hemodynamics dysfunction. Actually, edema further worsens ischemia by compressing cerebral arteries, which subsequently leads to a collapse of the blood flow that ultimately represents the cause of death. These findings demonstrate the coexistence of inflammatory and ischemic lesions and prove the preponderant role of edema in the fatal outcome of experimental cerebral malaria. They improve our understanding of the pathogenesis of cerebral malaria and may provide the necessary noninvasive surrogate markers for quantitative monitoring of treatment.
Rett Syndrome (RTT) is a devastating neurological disorder that is caused by mutations in the MECP2 gene. Mecp2-mutant mice have been used as a model system to study the disease mechanism. Our previous work has suggested that MeCP2 malfunction in neurons is the primary cause of RTT in the mouse. However, the neurophysiological consequences of MeCP2 malfunction remain obscure. Using whole-cell patch-clamp recordings in cortical slices, we show that spontaneous activity of pyramidal neurons is reduced in Mecp2-mutant mice. This decrease is not caused by a change in the intrinsic properties of the recorded neurons. Instead, the balance between cortical excitation and inhibition is shifted to favor inhibition over excitation. Moreover, analysis of the miniature excitatory postsynaptic currents (mEPSCs)/inhibitory postsynaptic currents (mIPSCs) in the Mecp2-mutant cortex reveals a reduction in mEPSC amplitudes, without significant change in the average mIPSC amplitude or frequency. These findings provide the first detailed electrophysiological analysis of Mecp2-mutant mice and provide a framework for understanding the pathophysiology of the disease and tools for studying the underlying disease mechanisms.
• autism
• cortical circuit
• MeCP2
• mental retardation
Rett syndrome is a severe X-linked neurological disorder in which most patients have mutations in the methyl-CpG binding protein 2 (MECP2) gene and suffer from bioaminergic deficiencies and life-threatening breathing disturbances. We used in vivo plethysmography, in vitro electrophysiology, neuropharmacology, immunohistochemistry, and biochemistry to characterize the consequences of the MECP2 mutation on breathing in wild-type (wt) and Mecp2-deficient (Mecp2-/y) mice. At birth, Mecp2-/y mice showed normal breathing and a normal number of medullary neurons that express tyrosine hydroxylase (TH neurons). At approximately 1 month of age, most Mecp2-/y mice showed respiratory cycles of variable duration; meanwhile, their medulla contained a significantly reduced number of TH neurons and norepinephrine (NE) content, even in Mecp2-/y mice that showed a normal breathing pattern. Between 1 and 2 months of age, all unanesthetized Mecp2-/y mice showed breathing disturbances that worsened until fatal respiratory arrest at approximately 2 months of age. During their last week of life, Mecp2-/y mice had a slow and erratic breathing pattern with a highly variable cycle period and frequent apneas. In addition, their medulla had a drastically reduced number of TH neurons, NE content, and serotonin (5-HT) content. In vitro experiments using transverse brainstem slices of mice between 2 and 3 weeks of age revealed that the rhythm produced by the isolated respiratory network was irregular in Mecp2-/y mice but could be stabilized with exogenous NE. We hypothesize that breathing disturbances in Mecp2-/y mice, and probably Rett patients, originate in part from a deficiency in noradrenergic and serotonergic modulation of the medullary respiratory network.
Autopsy studies in 8 girls with the Rett syndrome dying between 4 and 15 years showed: Diffuse cerebral atrophy/micrencephaly, with a decrease in brain weight by 13.8 to 33.8% of age-matched controls, apparently related to the duration of the disorder; Mild, but inconsistent diffuse cortical atrophy without developmental disorders apart from occasional microdysgenesis (three cases), but increased amounts of neuronal lipofuscin, and occasional mild astrocytic gliosis; Mild, but inconsistent spongy changes in cerebral and cerebellar white matter, optic nerve (two cases), and myelinated fascicles of the brainstem tegmentum, without signs of dys- or demyelination, and apparently different from the spongy myelinopathy common to aminoacidopathies; Most conspicuous was an underpigmentation of the substantia nigra which contained many fewer well-pigmented neurons for age (53-73%), and fewer pigmented granules per neuron, while the total number of nigral neurons and the triphasic substructure of neuromelanin were normal for age. No pathologic changes were seen in locus coeruleus, nucleus basalis of Meynert, and nucleus dorsalis raphe; Electron microscopy of autopsy material from an 11-year-old girl showed increased amounts of neuronal lipofuscin without signs of a storage disorder. Reactive and degenerating axons in the caudate nucleus were possibly related to the nigral changes, suggesting some dysfunction of the dopaminergic nigro-striatal system, while the synaptic organization of the neostriatum appeared unaffected. Peripheral nerve from a patient dying in advanced stage showed increased numbers of unmyelinated (regenerated?) axons, with almost no demyelination and few remyelinated axons, suggesting axonal degeneration rather than hypomyelination, but exogenous factors (malnutrition) cannot be excluded. The pathogenetic mechanisms of the morphologic brain lesions and their relations to clinical and neurochemical findings in Rett syndrome are unknown and deserve further intensive investigations.
(1)Diffuse cerebral atrophy/micrencephaly, with a decrease in brain weight by 13.8 to 33.8 % of age-matched controls, apparently related to the duration of the disorder;(2)Mild, but inconsistent diffuse cortical atrophy without developmental disorders apart from occasional microdysgenesis (three cases), but increased amounts of neuronal lipofuscin, and occasional mild astrocytic gliosis;(3)Mild, but inconsistent spongy changes in cerebral and cerebellar white matter, optic nerve (two cases), and myelinated fascicles of the brainstem tegmentum, without signs of dys- or demyelination, and apparently different from the spongy myelinopathy common to aminoacidopathies;(4)Mest conspicuous was an underpigmentation of the substantia nigra which contained many fewer well-pigmented neurons for age (53–73 %), and fewer pigmented granules per neuron, while the total number of nigral neurons and the triphasic substructure of neuromelanin were normal far age. No pathologic changes were seen in locus coeruleus, nucleus basalis of Meynert, and nucleus dorsalis raphe;(5)Electron microscopy of autopsy material from an 11-year-old girl showed increased amounts of neuronal lipefuscin without signs of a storage disorder. Reactive and degenerating axons in the caudate nucleus were pessibly related to the nigral changes, suggesting some dysfunction of the dopaminergic nigro-striatal system, while the synaptic organization of the neostriatum appeared unaffected.(6)Peripheral nerve from a patient dying in advanced stage showed increased numbers of unmyelinated (regenerated?) axons, with almost no demyelination and few remyelinated axons, suggesting axonal degeneration rather than hypomyelination, but exogenous factors (malnutrition) cannot be excluded.
Proton T(2) relaxation times of cerebral water and metabolites were measured before, during, and after transient forebrain ischemia in rat at 9.4 T using localized proton magnetic resonance spectroscopy ((1)H-MRS) with Hahn echoes formed at different echo times (TEs). It was found that the T(2) values of water and N-acetyl aspartate (NAA) methyl, but not total creatine (tCr) methyl, decrease significantly (approximately 10%) during ischemia, and this T(2) reduction is reversed by reperfusion. The T(2) reduction observed for NAA was most likely caused by the extravascular component of the blood oxygenation level-dependent (BOLD) effect induced by a drastically increased deoxyhemoglobin content during ischemia. The absence of T(2) changes for tCr can probably be explained by the fact that the BOLD-related T(2) decrease was counterbalanced by the conversion of phosphocreatine (PCr) to creatine (Cr), which has a longer T(2) than PCr, during ischemia. The changes in T(2) should be taken into account for the quantification of metabolite concentrations during ischemia.
The 1H NMR spectrum of the putative neurotransmitter dipeptide N-acetylaspartylglutamate (NAAG) is described, along with its identification in acid extracts of tissues of the central and peripheral nervous systems of the rat. The N-acetyl methyl resonance of NAAG (2.058 ppm) is close to that of N-acetylaspartate (NAA, 2.022 ppm), a prominent signal in 1H NMR spectra of the brain. The tissue concentration of NAAG is such that resonances of NAAG do not contribute greatly to 1H NMR spectra of the brain, except in studies of the brain stem or thalamus. In the spinal cord and peripheral nerves the level of NAAG is similar to that of NAA, and NAAG is a major metabolite contributing to the 1H NMR spectrum. The implications of these observations for 1H NMR spectra in vivo are discussed.
A method for 3-dimensional (3-D) visualization of dendritic spines and varicosities in human cortical neurons is described. Intracellular microinjection of Lucifer Yellow was used to display the morphology of dendrites on pyramidal and non-pyramidal neurons. Confocal laser scanning microscopy was used for imaging, and 3-D reconstructions and analysis of spines and varicosities were performed. The frontal, temporal, parietal and occipital cortices, and hippocampus in normal and pathological human brains were studied. Using this technique spines can be visualized from both sides of dendrites, which are ‘hidden’ in 2-D representations, and therefore not usually included in the extimation of dendritic spine density/total spine numbers. In patients with Rett's syndrome and some epilepsy patients, a regional loss of dendritic spines (‘naked’ dendrites) was found. These results will be included in the Human Brain Mapping Project.
The 1H NMR spectrum of the putative neurotransmitter dipeptide N-acetylaspartylglutamate (NAAG) is described, along with its identification in acid extracts of tissues of the central and peripheral nervous systems of the rat. The N-acetyl methyl resonance of NAAG (2.058 ppm) is close to that of N-acetylaspartate (NAA, 2.022 ppm), a prominent signal in 1H NMR spectra of the brain. The tissue concentration of NAAG is such that resonances of NAAG do not contribute greatly to 1H NMR spectra of the brain, except in studies of the brain stem or thalamus. In the spinal cord and peripheral nerves the level of NAAG is similar to that of NAA, and NAAG is a major metabolite contributing to the 1H NMR spectrum. The implications of these observations for 1H NMR spectra in vivo are discussed.
Rett syndrome is a neurodegenerative disease of young girls that begins in early childhood with autismlike behavior and loss of language skills, and progresses with marked deterioration of the motor system in the second decade of life. The purpose of this study was to determine if neuroanatomic changes detected with MR imaging could help to explain the clinical presentation and progression of signs and symptoms in these patients. Accordingly, computer-assisted planimetry was used to measure various dimensions of cerebral, cerebellar, and brainstem structures on sagittal and transverse MR images of 13 patients with Rett syndrome and 10 healthy volunteers. Dimensions of the cerebrum, basal ganglia, cerebellum, and brainstem were measured on transverse images. Areas of cerebellar vermian lobules, the fourth ventricle, the pituitary gland, and the corpus callosum were measured on sagittal images. Fourteen dimensions and areas were measured in each patient and each control subject; according to two-tailed Student's t tests, all but two values were significantly smaller in the patients with Rett syndrome than in control subjects. Graphing the measurements against age by using simple linear regression revealed progressive cerebellar atrophy without evidence of atrophy of the brainstem or cerebrum. Our results indicate that patients with Rett syndrome have global hypoplasia of the brain and progressive cerebellar atrophy increasing with age. Cerebellar atrophy with age may contribute to the deterioration of the motor system seen in older patients with Rett syndrome.
The etiology of Rett syndrome is unknown. Structural mitochondrial abnormalities have been described in muscle in patients with Rett syndrome. We report three children with Rett syndrome and normal muscle mitochondrial structure on light and electron microscopy. However, all had abnormalities in mitochondrial respiratory chain enzymes.
Combined MRI/MRS studies were performed in 9 girls with Rett syndrome of different ages. NAA, as marker of neuronal tissue, was found to decrease with increasing age. There was no evidence for a defective energy metabolism. The data point towards a probably secondary degenerative process in the pathogenesis of Rett syndrome.
Rett's syndrome (RS) is a clinically defined disorder that appears to be unique to girls and is characterized by apparent cognitive and motor skill loss early in life. We report our findings in the brains of three girls with RS, which were studied in comparison with age-matched controls by means of gapless serial section. Reduced neuronal cell size and increased cell-packing density were present throughout the cortical and subcortical regions of the brain in all cases without evidence of active degeneration. These observations appear to be consistent with a curtailment of development. Further, the degree of abnormality in each case correlates more closely with the clinical presentation of the patient at the time of death than with the age of the patient or duration of symptoms.
A total of eight girls with Rett syndrome were examined, by 31phosphorous magnetic resonance spectroscopy (31P MRS) (4 girls), proton MRS (1H MRS) (4 girls), muscle biopsying (2 girls), and determination of pyruvate and lactate in plasma (5 girls), to investigate the hypothesis of a mitochondrial malfunction as the etiology for this neurologic disorder. Almost all examinations, including electron microscopy in search of structural mitochondrial abnormalities, gave normal results, the only exception being the not unexpected finding of slight neurogenic atrophy in the muscle biopsy specimen from a 15-year-old girl.
We report the ultrastructural and biochemical alterations of muscle mitochondria in two girls with Rett syndrome. Our findings suggest the presence of an energy metabolism impairment the primary or secondary role of which in the pathogenesis of this syndrome cannot be defined at present.
Rett syndrome is a pediatric neurological disorder of unknown etiology defined by the presence of severe neurodevelopment decline, acquired microcephaly, dementia, abnormalities of movement, autistic behavior, and seizures in young female children. In this study, the neuroanatomy of 11 females with Rett syndrome and 15 age- and gender-matched control subjects was investigated in vivo with quantitative neuroimaging techniques. Compared to control subjects, the patients with Rett syndrome were found to have significantly reduced cerebral volume; evidence of greater loss of gray matter in comparison to white matter; regional variation in cortical gray matter, with the frontal regions showing the largest decrease; and reduced volume of the caudate nucleus and midbrain, even when taking into account general reduction in the size of the brain. In addition, there was no evidence of an ongoing degenerative process in this sample of girls with Rett syndrome. The consistency of these data with results from neuropathological investigations points to the need for continued quantitative neuroimaging studies of children with this condition. In particular, research employing serial longitudinal scans of very young children manifesting early signs of the clinical syndrome holds promise for helping to elucidate the neuropathological pathways leading to the debilitating clinical manifestations of Rett syndrome.
Various neocortical areas from four females aged 16-24 years with Rett syndrome (RS) were investigated and compared with brains of therapy-resistant partial epilepsy (TRPE) patients (18-25 years), infantile autism (IA), and control brains (24 and 58 years). The cytoarchitecture of area 10 (frontal), area 21 (temporal), area 4 (primary motor cortex), and area 17 (primary visual cortex) was studied by the combined Klüver-Barrera (luxol fast blue and cresyl violet) standard procedure. Autofluorescence of lipofuscin, immunofluorescence of synaptic vesicle proteins [synaptophysin (p38)] and lectin-stained (Wisteria floribunda agglutinin) perineuronal nets (PNs) were studied in the cortices using dual-channel confocal laser scanning microscopy. The brains of RS females show various types of morphological/cytoarchitectonical abnormalities of single pyramidal neurons in layers II-III, and V-VII of different cortical areas. The abnormalities include mild losses of pyramidal neurons, more pronounced in layers II and III than in layers V and VII, and more evident in frontal and temporal areas than in the visual cortex. Microdysgenesis, including abnormalities due to neuronal migration disorders, was not found in RS, in contrast to the observations in TRPE patients, strongly indicating that RS is not a neuronal migration disorder. Lipofuscin distribution was normal but amounts were lower in RS cases than in control and TRPE brains. PNs were less expressed in cortices of the IA case but were clearly overexpressed in the motor cortex of RS. Quantitative analysis of p38 showed a decrease in the area occupied by p38 immunoreactivity by 20-40% in RS compared with controls. It is concluded that RS could best be explained by a postnatal synaptogenic developmental deficiency; the basic defect, however, is still completely unknown.
Rett syndrome (RS), a neurodevelopmental disorder of unknown etiology occurring almost exclusively in females, is characterized by autistic-like behavior, motor dysfunction, loss of language skills, dementia, and microcephaly. This study is a follow-up and extension of a previously reported neuroimaging study of patients with RS. We replicated previously reported findings with a larger patient population, and the volumetric MRI analysis was extended to include an analysis of neuroanatomy of the posterior fossa. Twenty girls with RS were compared with individually age- and gender-matched normal controls. Patients with RS showed global reduction in gray- and white-matter volumes. The prefrontal, posterior-frontal, and anterior-temporal regions showed the largest bilateral decrease in gray-matter volume, whereas white-matter volume was uniformly reduced throughout the brain. We found confirmation for the preferential reduction in caudate nucleus volume. However, we observed no preferential reduction in midbrain volume despite a preferential reduction in the midsagittal area of this region. We also present an individual case comparison between monozygotic twins discordant for RS.
Thirteen patients (mean age 8.4 + 5.3 years) with Rett syndrome (RS) were studied with EEG and 99mTc-HMPAO SPECT. Eleven patients had background abnormalities and 10 patients paroxysmal activity in EEG. Hypoperfusion of varying severity was detected in 11 patients, 7 patients having multiple lesions. Bifrontal hypoperfusion, observed in 6 patients, was the most distinctive finding. Hypoperfusion was observed also in other cortical regions, except for the occipital lobes. There was no correlation between severity of the background abnormality or presence of paroxysmal activity in EEG and grade of hypoperfusion. There was, however, an association between the severity of hypoperfusion and early manifestation of symptoms in patients with RS. Whether this early-onset group of patients represents a different disease entity or only reflects disease variability the basic pathology being the same, is a possibility that deserves further clarification.
Rett syndrome is a progressive neurological paediatric disorder associated with severe mental deficiency, which affects only girls. The aim of this study was to determine if brain blood flow abnormalities detected with 99Tc(m)-ethyl-cysteinate-dimer (99Tc[m]-ECD) single photon emission tomography (SPET) can explain the clinical manifestation and progression of the disease. Qualitative and quantitative global and regional brain blood flow was evaluated in 12 girls with Rett syndrome and compared with an aged-matched reference group of children. In comparison with the reference group, SPET revealed a considerable global reduction in cerebral perfusion in the groups of girls with Rett syndrome. A large statistical difference was noted, which was more evident when comparing the control group with girls with stage IV Rett syndrome than girls with stage III Rett syndrome. The reduction in cerebral perfusion reflects functional disturbance in the brain of children with Rett syndrome. These data confirm that 99Tc(m)-ECD brain SPET is sensitive in detecting hypoperfused areas in girls with Rett syndrome that may be associated with brain atrophy, even when magnetic resonance imaging appears normal.
Rett syndrome, a neurodevelopmental disorder predominantly affecting girls, is characterized by regression of psychomotor development, communication dysfunction, and hand stereotypies. Brain morphologic studies demonstrate increased neuronal packing density and reduced dendritic arborizations, suggesting an arrest or interruption of normal maturation. Numerous neurotransmitter systems have been implicated. Among these, cerebrospinal fluid glutamate levels are elevated and glutamate receptors, particularly in putamen, are reduced. Therefore, 1H spectroscopy at 4.1 Tesla was used to evaluate glutamate, creatine, and N-acetylaspartate in six girls with Rett syndrome and four normal sibling controls. The ratio of creatine to N-acetylaspartate was significantly elevated in white matter, primarily reflecting reduced N-acetylaspartate levels, and normal in gray matter. The glutamate to N-acetylaspartate ratio was elevated in gray matter and normal in white matter. These findings are consistent with previous neuropathologic and neurochemical findings and indicate the feasibility of imaging these metabolites in vivo.
Rett syndrome (RTT, MIM 312750) is a progressive neurodevelopmental disorder and one of the most common causes of mental retardation in females, with an incidence of 1 in 10,000-15,000 (ref. 2). Patients with classic RTT appear to develop normally until 6-18 months of age, then gradually lose speech and purposeful hand use, and develop microcephaly, seizures, autism, ataxia, intermittent hyperventilation and stereotypic hand movements. After initial regression, the condition stabilizes and patients usually survive into adulthood. As RTT occurs almost exclusively in females, it has been proposed that RTT is caused by an X-linked dominant mutation with lethality in hemizygous males. Previous exclusion mapping studies using RTT families mapped the locus to Xq28 (refs 6,9,10,11). Using a systematic gene screening approach, we have identified mutations in the gene (MECP2 ) encoding X-linked methyl-CpG-binding protein 2 (MeCP2) as the cause of some cases of RTT. MeCP2 selectively binds CpG dinucleotides in the mammalian genome and mediates transcriptional repression through interaction with histone deacetylase and the corepressor SIN3A (refs 12,13). In 5 of 21 sporadic patients, we found 3 de novo missense mutations in the region encoding the highly conserved methyl-binding domain (MBD) as well as a de novo frameshift and a de novo nonsense mutation, both of which disrupt the transcription repression domain (TRD). In two affected half-sisters of a RTT family, we found segregation of an additional missense mutation not detected in their obligate carrier mother. This suggests that the mother is a germline mosaic for this mutation. Our study reports the first disease-causing mutations in RTT and points to abnormal epigenetic regulation as the mechanism underlying the pathogenesis of RTT.
To determine cerebral regional concentrations of N-acetyl aspartate (NAA), total choline (Cho), and total creatine (Cr) in Rett syndrome (RS) using 1H magnetic resonance spectroscopic imaging (MRSI).
The biochemical defect underlying RS is unknown. Because in vivo MRSI can detect important cerebral metabolites, MRSI has a potential to reveal impairment of regional cerebral metabolism in RS noninvasively.
High-resolution, multislice 1H MRSI was carried out in 17 girls with RS. The control group consisted of nine healthy children.
In patients with RS, average Cho concentration was 12% higher (p < 0.005) and average NAA concentration 11% lower (p < 0.0001) compared with the control group. Regional metabolic differences included significantly lower NAA concentration in the frontal gray and white matter, insula, and hippocampus in RS; no difference in regional Cho and Cr concentrations were found. A 20 to 38% higher Cho:NAA ratio in frontal and parietal gray and white matter, insular gray matter, and hippocampus (p < 0.05) and a 14 to 47% lower NAA:Cr ratio in frontal cortical gray matter, parietal and temporal white matter, insula, and putamen (p < 0.05) were found in subjects with RS compared with controls. Patients with seizures had higher average concentrations of Cho, Cr, and NAA compared with those without seizures (8-19%, p < 0.05).
Metabolic impairment in RS involves both gray and white matter and particularly involves frontal and parietal lobes and the insular cortex. Loss of NAA most likely reflects reduced neuronal and dendritic tree size; increased Cho concentration may result from gliosis.
Here are present the data concerning the intellectual, language and frontal performances of 24 children who had undergone surgery because of cerebellar hemispheric or vermis tumors and one girl with viral cerebellitis. The children with right cerebellar tumors presented auditory sequential memory and language processing disturbances; those with left cerebellar tumors showed deficits in spatial tests and visual sequential memory. The girl with cerebellitis showed a complex neuropsychological picture with impairment in processing language and in general sequential functions. Lesions of the vermis lead to two pictures: 1) a postsurgical mutism that could be subdivided into speech disorders (even to the extent of anarthria) and true language disturbances similar to frontal aphasia; and 2) behavioral disturbances ranging from irritability to a truly autistic response. These data seem to support the recently attributed role of the cerebellum as a modulator of the superior mental and social functions.
Acquired cerebellar lesions in adults have been shown to produce impairments in higher function as exemplified by the cerebellar cognitive affective syndrome. It is not yet known whether similar findings occur in children with acquired cerebellar lesions, and whether developmental factors influence their presentation. In studies to date, survivors of childhood cerebellar tumours who demonstrate long-term deficits in cognitive functions have undergone surgery as well as cranial irradiation or methotrexate treatment. Investigation of the effects of the cerebellar lesion independent of the known deleterious effects of these agents is important for understanding the role of the cerebellum in cognitive and affective development and for informing treatment and rehabilitation strategies. If the cerebellar contribution to cognition and affect is significant, then damage in childhood may influence a wide range of psychological processes, both as an immediate consequence and as these processes fail to develop normally later on. In this study we evaluated neuropsychological data in 19 children who underwent resection of cerebellar tumours but who received neither cranial irradiation nor methotrexate chemotherapy. Impairments were noted in executive function, including planning and sequencing, and in visual-spatial function, expressive language, verbal memory and modulation of affect. These deficits were common and in some cases could be dissociated from motor deficits. Lesions of the vermis in particular were associated with dysregulation of affect. Behavioural deficits were more apparent in older than younger children. These results reveal that clinically relevant neuropsychological changes may occur following cerebellar tumour resection in children. Age at the time of surgery and the site of the cerebellar lesion influence the neurobehavioural outcome. The results of the present study indicate that the cerebellar cognitive affective syndrome is evident in children as well as in adults, and they provide further clinical evidence that the cerebellum is an essential node in the distributed neural circuitry subserving higher-order behaviours.
Tumor necrosis factor alpha (TNFalpha) appears to take part in the pathogenesis of multiple sclerosis and to contribute to the degeneration of oligodendrocytes as well as neurons. TNFalpha is produced by microglia and astrocytes, which also produce hormones and cytokines that influence its biological activity. Thus, in mixed cultures the effects of exogenous TNFalpha might be modified by products of astrocytes and microglia. The effects of TNFalpha in oligodendrocyte-enriched cultures are reported below. We prepared the cultures by shaking oligodendrocytes off primary mixed glial-cell cultures from brains of 2-day-old rats at 7 days in vitro and plating them (0 days post-shake, DPS). Platelet-derived growth factor and fibroblast growth factor were included in the media at 1-5 DPS in order to encourage proliferation. At 2 DPS media were added with no TNFalpha (controls) or 1000, 2000 or 5000 U/ml of TNFalpha, and at 5 DPS media were replaced with fresh serum-free media. Cultures were fixed with 4% paraformaldehyde at 5, 7, 9 and 12 DPS and immunostained. Oligodendrocyte progenitors were not reduced in numbers immediately after the incubation with TNFalpha (i. e. at 5 DPS). However, after an additional 4 days in culture fewer progenitors remained in the cultures that had been treated with TNFalpha than in the untreated cultures. In the absence of the growth factors there were fewer progenitors, but their numbers also were reduced by TNFalpha. Maturation to the myelin basic protein (MBP)-positive stage was inhibited by about 36% at 9 DPS by 1000-2000 U/ml of TNFalpha, while numbers of O4+/MBP- precursors were unaffected. It is interesting that the steady-state number of O4-positive precursors was unchanged by TNFalpha at 9 DPS, when there were reductions in the numbers of A2B5-positive progenitors and MBP-positive mature oligodendrocytes. That observation suggests that the rates of proliferation, death and maturation are controlled by multiple factors, with a particularly vulnerable time at the maturation to the MBP-positive stage. At 5000 U/ml TNFalpha the specific effect on maturation was overtaken cytotoxicity. These data and a summary of the literature suggest that inhibition of MBP expression is sensitive to lower TNFalpha concentrations and incubation times than is cell survival. Specific effects on numbers of MBP-positive cells, morphology and MBP expression occur at 1000-2000 U/ml for 48-72 h or at up to 10000 U/ml for</=24 h, and the deficits remain after removal of the TNFalpha.
To clarify magnetic resonance imaging (MRI) findings in three adult patients with Rett syndrome who had been diagnosed with mental retardation and autism.
Clinical and MRI findings in three adult cases with Rett syndrome were studied. Ages (in years) in three adult cases with Rett Syndrome were 46 in Case 1, 35 in Case 2 and 20 in Case 3. They were able to walk and their convulsions were well controlled.
MRI findings in all patients showed mild cerebral atrophy, especially in the frontal and temporal lobes and two of the cases also had mild cerebellar atrophy. One case also showed a narrowing of the brainstem and thinning of the corpus callosum.
These results indicate that abnormalities in MRI imaging, in cases where there is narrowing of the brainstem and thinning of the corpus callosum, may be due to congenital hypoplasia. It was also seen that cerebellar atrophy became more distinct in older cases.
This paper will review the study of the neuropathology of Rett syndrome as it has evolved through several phases. In the 1986 the first descriptions of the Rett brain, by Seitelberger and Jellinger, identified that the brains were small, and that there was quantitatively less melanin in the pars compacta of the substantia nigra than in non-Rett brains. There were reports of non- specific gliosis and cell loss in the spinal cords and in the cerebellum, but with traditional neuropathology techniques there were no pathognomonic features that defined a specific neuropathology for Rett syndrome. This apparent absence of pathology was enigmatic in view of the profound clinical phenotype which involved dysfunction of cortex, basal ganglia, the limbic. autonomic and peripheral nervous systems. In the 1990's evaluation of the accumulating and careful reports of the clinical, functional, anatomic and chemical features of Rett syndrome suggested that the basis of Rett syndrome could be an interruption of brain development. MRI and autopsy examinations revealed that the brain in Rett syndrome was small, and that, unlike the brain in a degenerative disease, it did not become progressively smaller over time. Moreover, only the brain, and no other organ was small, emphasizing the susceptibility of the nervous system in the Rett disorder. Using Golgi studies a selective alteration in the size of dendrites of pyramidal neurons in the frontal, motor and temporal lobes was defined. Regional decreases of dendritic spines were also observed and immunocytochemical studies defined alterations in synaptic sites, early response gene activity and interneurons. MAP-2 immunoreactivity was found to be altered in selected neuronal populations. Studies of neurotransmitters using various techniques in various brain regions and CSF defined alterations (increases or decreases) in most systems, with only, according to Wenk, the studies of the cholinergic system being consistently decreased. The hypothesis that there are decreased neurotransmitters in Rett syndrome remains attractive, for it explains many of the functional deficits in Rett syndrome, and suggests a mechanism for defective brain maturation. However, the measurement of neurotransmitters and the interpretation of the results is problematic; the studies have included girls and women at various stages of the Rett disorder, using numerous techniques and various Rett tissues. In 2000 Rett families and researchers rejoiced at the long awaited identification of a mutated gene in Rett syndrome. Now MeCP2 is the focus of research into the neuropathology of Rett syndrome. An understanding of how this DNA methylating protein contributes to normal brain development should allow us to understand the deficits in Rett syndrome. Most importantly, it may allow us to devise strategies for therapy.
Neuroimaging is a key instrument for determining structural and in vivo functional status of the brain, non-invasively. Multiple approaches can now determine aspects of anatomic and neurochemical changes in brain, and have been utilized effectively in Rett Syndrome patients to understand the biological basis of this neurodevelopmental disorder. Studies performed at our institute include volumetric analyses of MRI, magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), cerebral blood flow measurements with MRI, and positron emission tomography scans (PET). These studies have provided considerable insight into mechanisms underlying the clinical features of this disease. Volumetric analyses suggest that decreased brain volume in RS results from global reductions in both gray and white matter of the brain. A selective vulnerability of the frontal lobes is evidenced by the preferential reduction of blood flow, increased choline and reduced n-acetyl aspartate (NAA) by MRS, and increased glucose uptake in these same regions as shown by ((18)F)-fluorodeoxyglucose (FDG) PET scans. We hypothesize that the increased glucose uptake relates to increased glutamate cycling in synapses. The resulting neuroexcitotoxic injury to the developing brain contributes to the seizures, behavioral disturbance and respiratory irregularities commonly seen in phases 1 and 2 of this disorder.
Molecular water pumps (MWPs) are characterized as biochemical systems existing at a compartmental boundary of living cells that can actively pump water against its gradient. A role for the observed intercompartmental transport of N-acetyl-L-aspartate (NAA), between neurons and oligodendrocytes in the CNS, as an efflux MWP for the removal of neuronal metabolic water has been proposed. In this review, accumulating evidence in support of such a role for NAA is presented, and the dynamics of the NAA cycle in myelinated neurons are considered. Based on the results of recent investigations, it is calculated that 1 mol of NAA is synthesized for every 40 mol of glucose (Glc) equivalent oxidized in the brain, and each mol of NAA may transport 121 mol of metabolic water out of neurons. In addition, turnover of total brain NAA is very rapid and appears to be only 16.7 h. Thus, the most important characteristic of NAA in the brain may not be its static level, but a dynamic aspect related to its rapid turnover. The relationship of NAA as a potential MWP to Canavan disease (CD), a genetic spongiform leukodystrophy in which the catabolic portion of the NAA cycle is deficient, and in a newly recognized brain disorder, hypoacetylaspartia, where the anabolic portion of the NAA cycle appears to be deficient, are discussed.
Rett syndrome is a progressive neurologic disorder affecting girls in early childhood with loss of achieved psychomotor abilities and mental retardation. Six sedated female patients (4 to 15 years of age) with a diagnosis of Rett syndrome were studied with [(18)F]fluorodeoxyglucose (FDG) and underwent positron emission tomography scanning of the brain. Relative tracer concentrations between different areas of the brain were assessed, and results were compared with 18 age-matched control subjects. Patients were divided into two age groups: 3 to 8 years of age and 9 to 15 years of age. A relative decrease in [(18)F]FDG uptake in the lateral occipital areas in relation with the whole brain and a relative increase in the cerebellum was evident in both age groups (P < 0.001, unpaired Student t test). A relative increase in frontal tracer uptake was observed in the younger group. Sensorimotor areas and relations between cortical and subcortical structures were preserved in all patients. Changes in glucose cerebral metabolism resemble the regional distribution of normal children less than 1 year of age, likely reflecting a maturational arrest. Changes in frontal areas parallel those in postmortem N-methyl-D-aspartate receptor densities and could correlate with different clinical stages of the disease. This pattern differs from those described in Down syndrome, autism, and Alzheimer's disease.
Cerebral metabolic changes that concur to motor and/or cognitive disorders in actively drinking alcoholics are not well established. We tested the hypothesis that chronic alcoholics exhibit profound alterations in the cerebral metabolism of scyllo-inositol. Brain metabolism was explored in nine actively drinking and 11 recently detoxified chronic alcoholics by in vivo brain (1)H-MRS and in vitro(1)H-MRS of blood serum and cerebrospinal fluid. The cohort was composed of individuals with acute, subacute or chronic encephalopathy or without any clinical encephalopathy. Chronic alcoholism is associated with a hitherto unrecognized accumulation of brain scyllo-inositol. Our results suggest that scyllo-inositol is produced within the central nervous system and shows a diffuse but heterogenous distribution in brain where it can persist several weeks after detoxification. Its highest levels were observed in subjects with a clinically symptomatic alcohol-related encephalopathy. When detected, brain scyllo-inositol takes part in a metabolic encephalopathy since it is associated with reduced N-acetylaspartate and increased creatine. High levels of cerebral scyllo-inositol are correlated with altered glial and neuronal metabolism. Our findings suggest that the accumulation of scyllo-inositol may precede and take part in the development of symptomatic alcoholic metabolic encephalopathy.
- M T Dotti
- L Manneschi
- A Malandrini
- N De Stefano
- F Caznerale
- A Federico
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Loss of silent-chromatin looping and impaired imprinting of DLX5 in Rett syndrome
- S Horike
- S Cai
- M Miyano
- J F Cheng
- T Kohwi-Shigematsu
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