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Loss of PV⁺ interneurons and decreased mRNA and protein levels of GABAA (α3) in PFC of Df(h22q11)/+ mice. a Immunofluorescence staining against PV⁺ interneurons in 50 μm fixed sections from PFC of WT (n = 6) and Df(h22q11)/+ (n = 6) mice. PFC was delineated, and PV⁺ interneurons were identified and counted in layers II/III and V/VI separately using Leica fluorescence microscope with a 63× oil lens. A significant decrease was detected in the number of PV⁺ interneurons in layers II/III (p < 0.05), while no difference was shown in layers V/VI in PFC of Df(h22q11)/+ compared with WT mice. Data were analyzed using Student t test. Results were considered significant when p value <0.05 (*p < 0.05). Data are presented as mean ± S.D. b Quantitative real time PCR was used to quantify the mRNA levels of Gabra1, Gabra2, and Gabra3. mRNA levels of Gabra1 and Gabra2 remained unchanged, while a significant decrease was detected at the Gabra3 mRNA levels (q < 0.05). Data from WT (n = 8) and Df(h22q11)/+ (n = 8) mice were analyzed with multiple t tests. Results were considered significant when Benjamini Krieger Yuketieli corrected p value (q value) < 0.05 (*q < 0.05). Data are presented as mean ± S.D. Western blot was used to immunoblot and quantify the protein levels of GABAA (α1), GABAA (α2), and GABAA (α3) in PFC of Df(h22q11)/+ compared with WT littermates. No significant change was detected in the protein levels of c GABAA (α1) or d GABAA (α2). e Protein levels of GABAA (α3) were significantly reduced in PFC of Df(h22q11)/+ compared with WT mice (q < 0.01). Data from WT (n = 6) and Df(h22q11)/+ (n = 6) mice. Data were analyzed with multiple t tests. Results were considered significant when q < 0.05 (**q < 0.01). Data are presented as mean ± S.D. f High-resolution confocal images of GABAA (α3) positive soma from layers II/III PFC of (n = 5) Df(h22q11)/+ and (n = 5) WT littermates. The number of GABAA (α3) positive puncta around soma was quantified, and a significant decrease was detected for soma from layers II/III PFC of Df(h22q11)/+ compared with WT mice (p < 0.05). Data were analyzed using Student t test. Results were considered significant when p < 0.05 (*p < 0.05). Data are presented as mean ± S.D.
Source publication
The 22q11.2 deletion has been identified as a risk factor for multiple neurodevelopmental disorders. Behavioral and cognitive impairments are common among carriers of the 22q11.2 deletion. Parvalbumin expressing (PV+) interneurons provide perisomatic inhibition of excitatory neuronal circuits through GABAA receptors, and a deficit of PV+ inhibitory...
Citations
... A great amount of high-quality work has been conducted in animal models of NDDs, many of which use an induced CNV to model disease processes. Whilst animal research does tend to support findings in human populations [144][145][146]; these studies were also excluded for two reasons. Firstly, like cellular models, animal models cannot accurately represent human NDD symptoms, for example hallucinations or theory of mind. ...
Cumulative evidence suggests neurodevelopmental disorders are closely related. The risk of these disorders is increased by a series of copy number variant syndromes – phenotypically heterogeneous genetic disorders, present in a minority of the population. Recent models suggest that a disruption in the balance between excitatory and inhibitory neural activity may contribute to the aetiology of neurodevelopmental disorders, and may be additionally disturbed in copy number variant syndromes. In this systematic review, the databases PubMed, Embase, and Scopus were searched for studies of excitation/inhibition imbalance in relation to neurodevelopmental disorders in human copy number variant samples. A total of 53 studies were included, representing a variety of copy number variants and research methodologies. The resulting data suggests excitation/inhibition balance is indeed disrupted in different copy number variant populations, providing insight into a putative mechanism of both idiopathic and genetic neurodevelopmental disorders. However, the high level of heterogeneity in the data set, alongside emerging techniques for excitation/inhibition assessment, prompts further investigation of this field.
... More generally, deficits in inhibitory signaling have been reported in the prefrontal cortex and hippocampus in other mouse models of 22q11.2DS [43,44], and human 22q11.2DS cerebral cortical organoids have been found to display increased spontaneous firing [45]. ...
The 22q11.2 deletion is a risk factor for multiple psychiatric disorders including schizophrenia and also increases vulnerability to middle-ear problems that can cause hearing impairment. Up to 60% of deletion carriers experience hearing impairment and ~30% develop schizophrenia in adulthood. It is not known if these risks interact. Here we used the Df1/+ mouse model of the 22q11.2 deletion to investigate how hearing impairment might interact with increased genetic vulnerability to psychiatric disease to affect brain function. We measured brain function using cortical auditory evoked potentials (AEPs), which are commonly measured non-invasively in humans. After identifying one of the simplest and best-validated methods for AEP measurement in mice from the diversity of previous approaches, we measured peripheral hearing sensitivity and cortical AEPs in Df1/+ mice and their WT littermates. We exploited large inter-individual variation in hearing ability among Df1/+ mice to distinguish effects of genetic background from effects of hearing impairment. Central auditory gain and adaptation were quantified by comparing brainstem activity and cortical AEPs and by analyzing the growth of cortical AEPs with increasing sound level or inter-tone interval duration. We found that level-dependent AEP growth was abnormally large in Df1/+ mice regardless of hearing impairment, but other AEP measures of central auditory gain and adaptation depended on both genotype and hearing phenotype. Our results demonstrate the relevance of comorbid hearing loss to auditory brain dysfunction in 22q11.2DS and also identify potential biomarkers for psychiatric disease that are robust to hearing impairment.
... deletion [54]. Studies in both humans with the deletion and 2p11.2 deletion mouse models also support disturbed E-I neurotransmitter system balance because of the deletion, with alterations in both glutamate and GABAergic neurotransmission supported [55][56][57], although effects on glutamate are not always found in patients [58]. While several studies have characterised the impact of 22q11.2 ...
Autism spectrum disorders (ASD) are a heterogenous set of syndromes characterised by social impairment and cognitive symptoms. Currently, there are limited treatment options available to help people with ASD manage their symptoms. Understanding the biological mechanisms that result in ASD diagnosis and symptomatology is an essential step in developing new interventional strategies. Human genetic studies have identified common gene variants of small effect and rare risk genes and copy number variants (CNVs) that substantially increase the risk of developing ASD. Reverse translational studies using rodent models based on these genetic variants provide new insight into the biological basis of ASD. Here we review recent findings from three ASD associated CNV mouse models (16p11.2, 2p16.3 and 22q11.2 deletion) that show behavioural and cognitive phenotypes relevant to ASD. These models have identified disturbed excitation-inhibition neurotransmitter balance, evidenced by dysfunctional glutamate and GABA signalling, as a key aetiological mechanism. These models also provide emerging evidence for serotoninergic neurotransmitter system dysfunction, although more work is needed to clarify the nature of this. At the brain network level, prefrontal cortex (PFC) dysfunctional connectivity is also evident across these models, supporting disturbed PFC function as a key nexus in ASD aetiology. Overall, published data highlight the utility and valuable insight gained into ASD aetiology from preclinical CNV mouse models. These have identified key aetiological mechanisms that represent putative novel therapeutic targets for the treatment of ASD symptoms, making them useful translational models for future drug discovery, development and validation.
... To generate biologically-informed hypotheses from rs-fMRI, we relate spatial maps of case-control differences to brain maps from multiple published sources, including metabolic positron emission tomography (PET), and post-mortem gene expression (36)(37)(38)(39). This approach can help explore human phenotypes relating to findings from pre-clinical 22qDel studies, such as altered mitochondria (40)(41)(42)(43), neurovascular development (44)(45)(46)(47), and cell type markers (48)(49)(50). ...
... deletion model. 94 General Factors (Age of Evaluation, Species, Sex, Experimental Bias) SCZ is often diagnosed in late adolescence and early adulthood. Along with the illness onset, patients show deficits in GABAergic transmission and impairment in cortical gamma frequency oscillations, which are thought to depend upon the normal functioning of PV interneurons. 1 We found that all animal models significantly affected PV interneurons in both brain areas when PV markers were evaluated in adulthood. ...
Background
Consistent with postmortem findings in patients, most animal models for schizophrenia (SCZ) present abnormal levels of parvalbumin (PV), a marker of fast-spiking GABAergic interneurons, in the prefrontal cortex (PFC) and hippocampus (HIP). However, there are discrepancies in the literature. PV reductions lead to a functional loss of PV interneurons, which is proposed to underly SCZ symptoms. Given its complex etiology, different categories of animal models have been developed to study SCZ, which may distinctly impact PV levels in rodent brain areas.
Study Design
We performed a quantitative meta-analysis on PV-positive cell number/density and expression levels in the PFC and HIP of animal models for SCZ based on pharmacological, neurodevelopmental, and genetic manipulations.
Results
Our results confirmed that PV levels are significantly reduced in the PFC and HIP regardless of the animal model. By categorizing into subgroups, we found that all pharmacological models based on NMDA receptor antagonism decreased PV-positive cell number/density or PV expression levels in both brain areas examined. In neurodevelopmental models, abnormal PV levels were confirmed in both brain areas in maternal immune activation models and HIP of the methylazoxymethanol acetate model. In genetic models, negative effects were found in neuregulin 1 and ERBB4 mutant mice in both brain regions and the PFC of dysbindin mutant mice. Regarding sex differences, male rodents exhibited PV reductions in both brain regions only in pharmacological models, while few studies have been conducted in females.
Conclusion
Overall, our findings support deficits in prefrontal and hippocampal PV interneurons in animal models for SCZ.
... Plastic changes of interneuron structure and function, whether through disease-relevant genetic insult, exogenous neuronal activation, receptor modulation, or experience-induced alterations, are poised to remodel computations within mPFC, and the routing of circuit-specific information through mPFC, to sculpt behavior. Numerous interneuron adaptations have been reported following each of these types of manipulations, manifesting as changes to mesoscopic and microscopic interneuron structure (e.g., Boksa et al., 2016;Al-Absi et al., 2020;Gildawie et al., 2020;Bueno-Fernandez et al., 2021), protein expression (e.g., Stedehouder et al., 2018;Mukherjee et al., 2019;Reichelt et al., 2021), and intrinsic physiology (e.g., Campanac and Hoffman, 2013;Dao et al., 2020;Zorrilla de San Martin et al., 2020). Here, we highlight some recent advances in our understanding of how plasticity in the synaptic and circuit connectivity of mPFC interneurons can reshape typical and disordered mPFC function and associated behavior (see also Yang et al., 2021). ...
Prefrontal cortex (PFC) inhibitory microcircuits regulate the gain and timing of pyramidal neuron firing, coordinate neural ensemble interactions, and gate local and long-range neural communication to support adaptive cognition and contextually tuned behavior. Accordingly, perturbations of PFC inhibitory microcircuits are thought to underlie dysregulated cognition and behavior in numerous psychiatric diseases and relevant animal models. This review, based on a Mini-Symposium presented at the 2022 Society for Neuroscience Meeting, highlights recent studies providing novel insights into: (1) discrete medial PFC (mPFC) interneuron populations in the mouse brain; (2) mPFC interneuron connections with, and regulation of, long-range mPFC afferents; and (3) circuit-specific plasticity of mPFC interneurons. The contributions of such populations, pathways, and plasticity to rodent cognition are discussed in the context of stress, reward, motivational conflict, and genetic mutations relevant to psychiatric disease.
... locus have been developed to better understand the contribution of single and multiple 22q11.2 genes to developmental, cell-specific, and behavioral deviations relative to wild-type littermates [54][55][56][57][58][59]. For example, Tbx1 heterozygous mice showed significant alterations of myelinated axons in the fimbria, lower mRNA levels of oligodendrocyte-related genes, and postnatal progenitor cells from the subventricular zone produced fewer oligodendrocytes in vitro [60]. ...
Recently, increasing numbers of rare pathogenic genetic variants have been identified that are associated with variably elevated risks of a range of neurodevelopmental outcomes, notably including Autism Spectrum Disorders (ASD), Schizophrenia Spectrum Disorders (SSD), and Intellectual Disability (ID). This review is organized along three main questions: First, how can we unify the exclusively descriptive basis of our current psychiatric diagnostic classification system with the recognition of an identifiable, highly penetrant genetic risk factor in an increasing proportion of patients with ASD or SSD? Second, what can be learned from studies of individuals with ASD or SSD who share a common genetic basis? And third, what accounts for the observed variable penetrance and pleiotropy of neuropsychiatric phenotypes in individuals with the same pathogenic variant? In this review, we focus on findings of clinical and preclinical studies of the 22q11.2 deletion syndrome (22q11DS). This particular variant is not only one of the most common among the increasing list of known rare pathogenic variants, but also one that benefits from a relatively long research history. Consequently, 22q11DS is an appealing model as it allows us to: (1) elucidate specific genotype–phenotype associations, (2) prospectively study behaviorally defined classifications, such as ASD or SSD, in the context of a known, well-characterized genetic basis, and (3) elucidate mechanisms underpinning variable penetrance and pleiotropy, phenomena with far-reaching ramifications for research and clinical practice. We discuss how findings from animal and in vitro studies relate to observations in human studies and can help elucidate factors, including genetic, environmental, and stochastic, that impact the expression of neuropsychiatric phenotypes in 22q11DS, and how this may inform mechanisms underlying neurodevelopmental expression in the general population. We conclude with research priorities for the field, which may pave the way for novel therapeutics.
... does harbor a reduction in GABA-ergic parvalbumin containing cortical interneurons in 22q11.2DS (Al-Absi et al., 2020). Therefore, a potential mechanism of altered sleep and sleep-associated EEG oscillations may involve neurodevelopmental changes to cortical structure and GABAergic signaling in cortical inhibitory networks in 22q11.2DS. ...
Background
Young people living with 22q11.2 Deletion Syndrome (22q11.2DS) are at increased risk of schizophrenia, intellectual disability, attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). In common with these conditions, 22q11.2DS is also associated with sleep problems. We investigated whether abnormal sleep or sleep-dependent network activity in 22q11.2DS reflects convergent, early signatures of neural circuit disruption also evident in associated neurodevelopmental conditions.
Methods
In a cross-sectional design, we recorded high-density sleep EEG in young people (6–20 years) with 22q11.2DS (n=28) and their unaffected siblings (n=17), quantifying associations between sleep architecture, EEG oscillations (spindles and slow waves) and psychiatric symptoms. We also measured performance on a memory task before and after sleep.
Results
22q11.2DS was associated with significant alterations in sleep architecture, including a greater proportion of N3 sleep and lower proportions of N1 and REM sleep than in siblings. During sleep, deletion carriers showed broadband increases in EEG power with increased slow-wave and spindle amplitudes, increased spindle frequency and density, and stronger coupling between spindles and slow-waves. Spindle and slow-wave amplitudes correlated positively with overnight memory in controls, but negatively in 22q11.2DS. Mediation analyses indicated that genotype effects on anxiety, ADHD and ASD were partially mediated by sleep EEG measures.
Conclusions
This study provides a detailed description of sleep neurophysiology in 22q11.2DS, highlighting alterations in EEG signatures of sleep which have been previously linked to neurodevelopment, some of which were associated with psychiatric symptoms. Sleep EEG features may therefore reflect delayed or compromised neurodevelopmental processes in 22q11.2DS, which could inform our understanding of the neurobiology of this condition and be biomarkers for neuropsychiatric disorders.
Funding
This research was funded by a Lilly Innovation Fellowship Award (UB), the National Institute of Mental Health (NIMH 5UO1MH101724; MvdB), a Wellcome Trust Institutional Strategic Support Fund (ISSF) award (MvdB), the Waterloo Foundation (918-1234; MvdB), the Baily Thomas Charitable Fund (2315/1; MvdB), MRC grant Intellectual Disability and Mental Health: Assessing Genomic Impact on Neurodevelopment (IMAGINE) (MR/L011166/1; JH, MvdB and MO), MRC grant Intellectual Disability and Mental Health: Assessing Genomic Impact on Neurodevelopment 2 (IMAGINE-2) (MR/T033045/1; MvdB, JH and MO); Wellcome Trust Strategic Award ‘Defining Endophenotypes From Integrated Neurosciences’ Wellcome Trust (100202/Z/12/Z MO, JH). NAD was supported by a National Institute for Health Research Academic Clinical Fellowship in Mental Health and MWJ by a Wellcome Trust Senior Research Fellowship in Basic Biomedical Science (202810/Z/16/Z). CE and HAM were supported by Medical Research Council Doctoral Training Grants (C.B.E. 1644194, H.A.M MR/K501347/1). HMM and UB were employed by Eli Lilly & Co during the study; HMM is currently an employee of Boehringer Ingelheim Pharma GmbH & Co KG. The views and opinions expressed are those of the author(s), and not necessarily those of the NHS, the NIHR or the Department of Health funders.
... We have recently reported on deficit of GABA A receptor expression in the prefrontal cortex of Df(h22q11)/+ mice that also exhibited decreased gamma oscillatory synchrony and reduced synaptic plasticity in the cortical-hippocampal networks (Nilsson et al., 2018;Al-Absi et al., 2020;Tripathi et al., 2020). Df(h22q11)/+ mice further display deficits in multiple cognitive and behavioral domains that resemble core neurodevelopmental symptoms of 22q11.2DS ...
... In our previous study, we reported multi-site deficits affecting the GABAergic inhibitory circuits in the prefrontal cortex of Df(h22q11)/+ mice, involving altered levels of GABA A (α3) receptors (Al-Absi et al., 2020). Interestingly, treatment of 22q11.2 ...
... locus is further reported to disrupt the brain GABAergic transmission (Crabtree et al., 2016). Results from our previous study (Al-Absi et al., 2020), where we observed alterations in the levels of GABA A receptors in the prefrontal cortex, in addition to the results from this study may provide supporting evidence in this direction. The loss of GAD67 + interneurons in CA1 of Df(h22q11)/+ mice can also contribute to the reduction of GABA A receptor binding levels in this brain subregion. ...
The 22q11.2 hemizygous deletion confers high risk for multiple neurodevelopmental disorders. Inhibitory signaling, largely regulated through GABAA receptors, is suggested to serve a multitude of brain functions that are disrupted in the 22q11.2 deletion syndrome.
We investigated the putative deficit of GABAA receptors and the potential substrates contributing to the inhibitory and excitatory dysregulations in hippocampal networks of the Df(h22q11)/+ mouse model of the 22q11.2 hemizygous deletion. The Df(h22q11)/+ mice exhibited impairments in several hippocampus-related functional domains, represented by impaired spatial memory and sensory gating functions. Autoradiography using the [³H]muscimol tracer revealed a significant reduction in GABAA receptor binding in the CA1 and CA3 subregions, together with a loss of GAD67⁺ interneurons in CA1 of Df(h22q11)/+ mice. Furthermore, electrophysiology recordings exhibited significantly higher neuronal activity in CA3, in response to the GABAA receptor antagonist, bicuculline, as compared with wild type mice. Density and volume of dendritic spines in pyramidal neurons were reduced and Sholl analysis also showed a reduction in the complexity of basal dendritic tree in CA1 and CA3 subregions of Df(h22q11)/+ mice.
Overall, our findings demonstrate that hemizygous deletion in the 22q11.2 locus leads to dysregulations in the inhibitory circuits, involving reduced binding levels of GABAA receptors, in addition to functional and structural modulations of the excitatory networks of hippocampus.
... Reduced PV+ cell density could arise from disrupted PV+ cell migration to cortex during embryonic development (~E13-E17), increased PV+ cell death during postnatal development (~P5-P15), and/or reduction in PV expression in cortical interneurons after development (64,65). Previous work suggests that otitis media develops soon after ear opening (at P11) in affected Df1/+ ears (13), a finding consistent with our observation of hearing impairment in Df1/+ mice at 3-6 weeks of age. ...
... Previous studies of mouse models of 22q11.2DS have reported altered laminar distribution and/or reduced density of PV+ interneurons in the medial prefrontal cortex and hippocampus (37,(64)(65)(66)(67). Abnormalities in PV+ interneurons are also a common finding in human schizophrenia, and are thought to contribute to cognitive deficits (25,(70)(71)(72)(73). Thus, auditory cortical PV+ interneuron abnormalities in mouse models of 22q11.2DS ...
Background
Hearing impairment is a risk factor for schizophrenia. Patients with 22q11.2 Deletion Syndrome (22q11.2DS) have a 25-30% risk of schizophrenia, and up to 60% also have varying degrees of hearing impairment, primarily from middle ear inflammation. The Df1/+ mouse model of 22q11.2DS recapitulates many features of the human syndrome, including schizophrenia-relevant brain abnormalities and high inter-individual variation in hearing ability. However, the relationship between brain abnormalities and hearing impairment in Df1/+ mice has not been examined.
Methods
We measured auditory brainstem responses (ABRs), cortical auditory evoked potentials, and/or cortical parvalbumin-positive (PV+) interneuron density in over 70 adult mice (32 Df1/+, 39 wild-type). We also performed longitudinal ABR measurements in an additional 20 animals (13 Df1/+, 7 wild-type) from 3 weeks of age.
Results
Electrophysiological markers of central auditory excitability were elevated in Df1/+ mice. PV+ interneurons, which are implicated in schizophrenia pathology, were reduced in density in auditory cortex but not secondary motor cortex. Both auditory brain abnormalities correlated with hearing impairment, which affected approximately 60% of adult Df1/+ mice and typically emerged before 6 weeks of age.
Conclusions
In the Df1/+ mouse model of 22q11.2DS, abnormalities in central auditory excitability and auditory cortical PV+ immunoreactivity correlate with hearing impairment. This is the first demonstration of cortical PV+ interneuron abnormalities correlating with hearing impairment in a mouse model of either schizophrenia or middle ear inflammation.
