Article

Schizophrenia risk from complex variation of complement component 4

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Schizophrenia is a heritable brain illness with unknown pathogenic mechanisms. Schizophrenia's strongest genetic association at a population level involves variation in the major histocompatibility complex (MHC) locus, but the genes and molecular mechanisms accounting for this have been challenging to identify. Here we show that this association arises in part from many structurally diverse alleles of the complement component 4 (C4) genes. We found that these alleles generated widely varying levels of C4A and C4B expression in the brain, with each common C4 allele associating with schizophrenia in proportion to its tendency to generate greater expression of C4A. Human C4 protein localized to neuronal synapses, dendrites, axons, and cell bodies. In mice, C4 mediated synapse elimination during postnatal development. These results implicate excessive complement activity in the development of schizophrenia and may help explain the reduced numbers of synapses in the brains of individuals with schizophrenia.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

Supplementary resource (1)

... The largest genetic risk factors for SCZ are associated with the immune-linked major histocompatibility complex (MHC) and complement component 4 (C4) genes consisting of C4A and C4B 4,5 . Increased copy number variants of C4A correlate with increased SCZ risk 5 , with elevated levels of C4A found in post-mortem brain samples 5 and cerebrospinal fluid (CSF) of patients with SCZ 6 . ...
... The largest genetic risk factors for SCZ are associated with the immune-linked major histocompatibility complex (MHC) and complement component 4 (C4) genes consisting of C4A and C4B 4,5 . Increased copy number variants of C4A correlate with increased SCZ risk 5 , with elevated levels of C4A found in post-mortem brain samples 5 and cerebrospinal fluid (CSF) of patients with SCZ 6 . Increased complement C3 deposition on synaptic structures, initiated by C4 in the complement cascade, play a pivotal role in microglia-mediated elimination of synapses 7,8 . ...
... The largest genetic risk factors for SCZ are associated with the immune-linked major histocompatibility complex (MHC) and complement component 4 (C4) genes consisting of C4A and C4B 4,5 . Increased copy number variants of C4A correlate with increased SCZ risk 5 , with elevated levels of C4A found in post-mortem brain samples 5 and cerebrospinal fluid (CSF) of patients with SCZ 6 . Increased complement C3 deposition on synaptic structures, initiated by C4 in the complement cascade, play a pivotal role in microglia-mediated elimination of synapses 7,8 . ...
Preprint
Elevated expression of the complement component 4A (C4A) protein has been linked to an increased risk of schizophrenia (SCZ). However, there are few human models available to study the mechanisms by which C4A contributes to the development of SCZ. In this study, we established a C4A overexpressing neuroimmune cortical organoid (NICO) model, which includes mature neuronal cells, astrocytes, and functional microglia. The C4A NICO model recapitulated several neuroimmune endophenotypes observed in SCZ patients, including modulation of inflammatory genes and increased cytokine secretion. C4A expression also increased microglia-mediated synaptic uptake in the NICO model, supporting the hypothesis that synapse and brain volume loss in SCZ patients may be due to excessive microglial pruning. Our results highlight the role of C4A in the immunogenetic risk factors for SCZ and provide a human model for phenotypic discovery and validation of immunomodulating therapies.
... During human brain development a major function of microglia is synaptic pruning [130]. It was shown that excessive synaptic pruning by microglia contributes to the reduction in synapse density in SZ patients [19,132]. Additionally, reduced synaptic density was observed in a postmortem adult brain from SZ patient [70]. ...
... Additionally, reduced synaptic density was observed in a postmortem adult brain from SZ patient [70]. Schizophrenia's strongest genetic association at a population level involves variation in MHC locus, arising in part from many structurally diverse alleles of the complement component 4 (C4) genes [132]. These alleles generate highly varying levels of C4A and C4B expression in the brain, with each common C4 allele associating with SZ in proportion to its tendency to generate greater expression of C4A. ...
... These alleles generate highly varying levels of C4A and C4B expression in the brain, with each common C4 allele associating with SZ in proportion to its tendency to generate greater expression of C4A. Human C4 protein localizes to neuronal synapses, dendrites, axons and cell bodies and is believed to be involved in synaptic pruning [132]. In line with this, increased elimination of synaptic structures has been observed by SZ patient The hiPSC-derived microglia [134]. ...
Article
Full-text available
Schizophrenia (SZ) is a severe psychiatric disorder, with a prevalence of 1–2% world-wide and substantial health- and social care costs. The pathology is influenced by both genetic and environmental factors, however the underlying cause still remains elusive. SZ has symptoms including delusions, hallucinations, confused thoughts, diminished emotional responses, social withdrawal and anhedonia. The onset of psychosis is usually in late adolescence or early adulthood. Multiple genome-wide association and whole exome sequencing studies have provided extraordinary insights into the genetic variants underlying familial as well as polygenic forms of the disease. Nonetheless, a major limitation in schizophrenia research remains the lack of clinically relevant animal models, which in turn hampers the development of novel effective therapies for the patients. The emergence of human induced pluripotent stem cell (hiPSC) technology has allowed researchers to work with SZ patient-derived neuronal and glial cell types in vitro and to investigate the molecular basis of the disorder in a human neuronal context. In this review, we summarise findings from available studies using hiPSC-based neural models and discuss how these have provided new insights into molecular and cellular pathways of SZ. Further, we highlight different examples of how these models have shown alterations in neurogenesis, neuronal maturation, neuronal connectivity and synaptic impairment as well as mitochondrial dysfunction and dysregulation of miRNAs in SZ patient-derived cultures compared to controls. We discuss the pros and cons of these models and describe the potential of using such models for deciphering the contribution of specific human neural cell types to the development of the disease.
... Another key limitation of animal models is the genetic differences between animals and humans. For example, the schizophrenia risk gene complement component 4 (C4) [31] has C4A and C4B isotypes in human, but solely C4b in mouse. Considering that greater C4A expression in the brain is associated with increased schizophrenia risk [31], the C4b knockout mouse may not be a good model for schizophrenia and other microglia pruning-related disorders. ...
... For example, the schizophrenia risk gene complement component 4 (C4) [31] has C4A and C4B isotypes in human, but solely C4b in mouse. Considering that greater C4A expression in the brain is associated with increased schizophrenia risk [31], the C4b knockout mouse may not be a good model for schizophrenia and other microglia pruning-related disorders. In addition, animal models usually need a long experimental period and motivate the development of in-vitro cell culture models for human microglia study. ...
... In addition to neurodegenerative diseases, microglia dysfunction also connects to a wide range of psychiatric disorders [21,22]. Studies including genome-wide association study [31] and gene coexpression analysis based on human postmortem brain transcriptome data [102] suggested the pathological involvement of microglia in schizophrenia, bipolar disorder, and autism. A robust microglial model that mimics the in-vivo human brain is needed for understanding the roles of microglia in brain disorders. ...
Article
Full-text available
Microglia are resident immune cells in the central nervous system, playing critical roles in brain development and homeostasis. Increasing evidence has implicated microglia dysfunction in the pathogenesis of various brain disorders ranging from psychiatric disorders to neurodegenerative diseases. Using a human cell-based model to illuminate the functional mechanisms of microglia will promote pathological studies and drug development. The recently developed microglia-containing human brain organoids (MC-HBOs), in-vitro three-dimensional cell cultures that recapitulate key features of the human brain, have provided a new avenue to model brain development and pathology. However, MC-HBOs generated from different methods differ in the origin, proportion, and fidelity of microglia within the organoids, and may have produced inconsistent results. To help researchers to develop a robust and reproducible model that recapitulates in-vivo signatures of human microglia to study brain development and pathology, this review summarized the current methods used to generate MC-HBOs and provided opinions on the use of MC-HBOs for disease modeling and functional studies.
... synaptic pruning by microglia (Sekar et al., 2016;Sellgren et al., 2019;Park et al., 2020). ...
... Indeed, this hypothesis and proposed treatment corroborate longitudinal studies of SCZ: synaptic pruning in the cerebral cortex is prevalent in late adolescence and early adulthood, which coincides with the period when SCZ symptoms typically begin to arise (Petanjek et al., 2011;Cannon, 2015). Further, mutations in the complement component 4 gene constitute a risk factor for SCZ development (Sekar et al., 2016), and notably, this SCZ susceptibility gene regulates microgliamediated synaptic pruning in mice during early postnatal development (Sekar et al., 2016;Sellgren et al., 2019;Yilmaz et al., 2021). Similarly, a study of cultured cerebral interneurons derived from patients with SCZ or healthy controls found that, in both types of cultures, exposure to inflammatory-cytokinereleasing microglia resulted in reduced interneuron arborization and synapse formation (Park et al., 2020). ...
... Indeed, this hypothesis and proposed treatment corroborate longitudinal studies of SCZ: synaptic pruning in the cerebral cortex is prevalent in late adolescence and early adulthood, which coincides with the period when SCZ symptoms typically begin to arise (Petanjek et al., 2011;Cannon, 2015). Further, mutations in the complement component 4 gene constitute a risk factor for SCZ development (Sekar et al., 2016), and notably, this SCZ susceptibility gene regulates microgliamediated synaptic pruning in mice during early postnatal development (Sekar et al., 2016;Sellgren et al., 2019;Yilmaz et al., 2021). Similarly, a study of cultured cerebral interneurons derived from patients with SCZ or healthy controls found that, in both types of cultures, exposure to inflammatory-cytokinereleasing microglia resulted in reduced interneuron arborization and synapse formation (Park et al., 2020). ...
Article
Full-text available
In the central nervous system (CNS) neurons are classically considered the functional unit of the brain. Analysis of the physical connections and co-activation of neurons, referred to as structural and functional connectivity, respectively, is a metric used to understand their interplay at a higher level. A myriad of glial cell types throughout the brain composed of microglia, astrocytes and oligodendrocytes are key players in the maintenance and regulation of neuronal network dynamics. Microglia are the central immune cells of the CNS, able to affect neuronal populations in number and connectivity, allowing for maturation and plasticity of the CNS. Microglia and astrocytes are part of the neurovascular unit, and together they are essential to protect and supply nutrients to the CNS. Oligodendrocytes are known for their canonical role in axonal myelination, but also contribute, with microglia and astrocytes, to CNS energy metabolism. Glial cells can achieve this variety of roles because of their heterogeneous populations comprised of different states. The neuroglial relationship can be compromised in various manners in case of pathologies affecting development and plasticity of the CNS, but also consciousness and mood. This review covers structural and functional connectivity alterations in schizophrenia, major depressive disorder, and disorder of consciousness, as well as their correlation with vascular connectivity. These networks are further explored at the cellular scale by integrating the role of glial cell diversity across the CNS to explain how these networks are affected in pathology.
... Distinct from mouse, human C4 is encoded by two closely related genes, C4A and C4B, then typically present in multiple copy numbers (CNs) per genome and gene isotype. SCZ risk attributed to this locus can largely be explained by genetically predicted C4A RNA expression, and elevated C4A expression has been confirmed in SCZ postmortem brain tissue 1 . During brain development, microglia utilize complement signaling for selective removal of supernumerary synapses by complement receptor 3 (C3R)-dependent phagocytosis 2,3 . ...
... CNs of C4 structural elements (C4A-HERV+, C4A-HERV−, C4B-HERV+, and C4B-HERV− CNs) in the KaSP cohort were imputed from MHC genotypes computed from whole genome sequencing (WGS) data. HapMap3 CEU reference haplotype panel, from Sekar et al. 1 , was used to impute pre-annotated C4 haplogroups, using Beagle (version 3.3), with subsets of SNPs in the extended MHC locus (chr6: 25-34 Mb). ...
... To view a copy of this license, visit http://creativecommons.org/ licenses/by/4.0/. © The Author(s) 2022 1 ...
Article
Full-text available
Postsynaptic density is reduced in schizophrenia, and risk variants increasing complement component 4A ( C4A ) gene expression are linked to excessive synapse elimination. In two independent cohorts, we show that cerebrospinal fluid (CSF) C4A concentration is elevated in patients with first-episode psychosis (FEP) who develop schizophrenia (FEP-SCZ: median 0.41 fmol/ul [CI = 0.34–0.45], FEP-non-SCZ: median 0.29 fmol/ul [CI = 0.22–0.35], healthy controls: median 0.28 [CI = 0.24–0.33]). We show that the CSF elevation of C4A in FEP-SCZ exceeds what can be expected from genetic risk variance in the C4 locus, and in patient-derived cellular models we identify a mechanism dependent on the disease-associated cytokines interleukin (IL)−1beta and IL-6 to selectively increase neuronal C4A mRNA expression. In patient-derived CSF, we confirm that IL-1beta correlates with C4A controlled for genetically predicted C4A RNA expression ( r = 0.39; CI: 0.01–0.68). These results suggest a role of C4A in early schizophrenia pathophysiology.
... The strongest common variant association with schizophrenia is localized to the major histocompatibility complex (MHC) 135,144,145 , a genomic region that contains many genes linked to infection and autoimmunity. A comprehensive analysis demonstrated that part of the MHC association with schizophrenia is driven by structural variation in the gene C4, which encodes complement component 4 (C4) 146 . The complement system is part of the innate immune system and also contributes to normal brain development by eliminating immature synapses 147,148 . ...
... In mice, C4 was shown to promote synapse elimination during development. These findings indicate that at least part of the MHC association with schizophrenia may implicate inappropriate synaptic maturation 146 . However, note that the MHC risk locus only represents a minor part of the genetic risk architecture underlying schizophrenia. ...
Article
Full-text available
Psychiatric genetics has made substantial progress in the last decade, providing new insights into the genetic etiology of psychiatric disorders, and paving the way for precision psychiatry, in which individual genetic profiles may be used to personalize risk assessment and inform clinical decision‐making. Long recognized to be heritable, recent evidence shows that psychiatric disorders are influenced by thousands of genetic variants acting together. Most of these variants are commonly occurring, meaning that every individual has a genetic risk to each psychiatric disorder, from low to high. A series of large‐scale genetic studies have discovered an increasing number of common and rare genetic variants robustly associated with major psychiatric disorders. The most convincing biological interpretation of the genetic findings implicates altered synaptic function in autism spectrum disorder and schizophrenia. However, the mechanistic understanding is still incomplete. In line with their extensive clinical and epidemiological overlap, psychiatric disorders appear to exist on genetic continua and share a large degree of genetic risk with one another. This provides further support to the notion that current psychiatric diagnoses do not represent distinct pathogenic entities, which may inform ongoing attempts to reconceptualize psychiatric nosology. Psychiatric disorders also share genetic influences with a range of behavioral and somatic traits and diseases, including brain structures, cognitive function, immunological phenotypes and cardiovascular disease, suggesting shared genetic etiology of potential clinical importance. Current polygenic risk score tools, which predict individual genetic susceptibility to illness, do not yet provide clinically actionable information. However, their precision is likely to improve in the coming years, and they may eventually become part of clinical practice, stressing the need to educate clinicians and patients about their potential use and misuse. This review discusses key recent insights from psychiatric genetics and their possible clinical applications, and suggests future directions.
... Previous studies have suggested that inflammatory cytokines mediate the immune system and brain, which may lead to decreased availability of serotonin and other neurotransmitters, activation of the hypothalamicpituitary-adrenal axis, and increased oxidative stress in the brain [10,11]. A series of studies have demonstrated that complement is a key driver of inflammation, and complement dysregulation plays a critical role in neurodevelopment, such as developmentally timed synaptic pruning in the brain, causing pathology in psychosis [12][13][14]. Although changes in inflammatory and complement levels might contribute to the pathogenesis of psychosis, findings concerning peripheral levels across different stages of psychosis are mixed [3,[15][16][17][18][19], with findings of increased and decreased levels and no difference. ...
... However, in the complement-specific prediction model, C5 and C5a significantly contributed to the prediction of conversion. In the few studies on the complement levels of patients with psychosis, most of the results focused on complement C3 and C4 [12], while there are few studies on the role of complement C5 in psychosis, and most of them are insignificant findings [4,17]. In general, complement activation follows various pathways, and the final step of the pathway converges upon the cleavage of complement C5 into complement fragments C5a and C5b. ...
Article
Full-text available
Immunological/inflammatory factors are implicated in the development of psychosis. Complement is a key driver of inflammation; however, it remains unknown which factor is better at predicting the onset of psychosis. This study aimed to compare the alteration and predictive performance of inflammation and complement in individuals at clinical high risk (CHR). We enrolled 49 individuals at CHR and 26 healthy controls (HCs). Twenty-five patients at CHR had converted to psychosis (converter) by the 3-year follow-up. Inflammatory cytokines, including interleukin (IL)-1β, 6, 8, 10, tumor necrosis factor-alpha (TNF-alpha), macrophage colony-stimulating factor levels, and complement proteins (C1q, C2, C3, C3b, C4, C4b, C5, C5a, factor B, D, I, H) were measured by enzyme-linked immunosorbent assay at baseline. Except for TNF- alpha, none of the inflammatory cytokines reached a significant level in either the comparison of CHR individuals and HC or between CHR-converters and non-converters. The C5, C3, D, I, and H levels were significantly lower (C5, p = 0.006; C3, p = 0.009; D, p = 0.026; I, p = 0.016; H, p = 0.019) in the CHR group than in the HC group. Compared to non-converters, converters had significantly lower levels of C5 (p = 0.012) and C5a (p = 0.007). None of the inflammatory factors, but many complement factors, showed significant correlations with changes in general function and symptoms. None of the inflammatory markers, except for C5a and C5, were significant in the discrimination of conversion outcomes in CHR individuals. Our results suggest that altered complement levels in the CHR population are more associated with conversion to psychosis than inflammatory factors. Therefore, an activated complement system may precede the first-episode of psychosis and contribute to neurological pathogenesis at the CHR stage.
... Finally, the newest identified research trends were cluster #29 'physical exercise' (S=1; 2011) (Pajonk et al., 2010) and cluster #13 'inflammation' (S=0.973; 2015) (Sekar et al., 2016), which extends to cluster #24 'biomarker' (S=1; 2019) (Orlovska-Waast et al., 2019). The timeline view permits us to identify that the latest most active clusters were clusters #2 'long-acting injectable', #7 'high risk/ultrahigh risk', #13 'inflammation', #24 'biomarker' and #29 'physical exercise' (Supplementary Table 1. ...
... For the latter, we conducted a refining process with a qualitative analysis of highly cited references of each cluster to clearly identify whether given clusters are organized around studies that specifically address negative symptoms (Supplementary Tables 1, 2 and 3). Such conflation can be seen with the cluster on 'inflammation', which is rather nonspecific to negative symptoms, with highly cited papers mainly on the link between inflammation, genetics, depression or specific risk factors for schizophrenia (Müller, 2018;Sekar et al., 2016;Upthegrove et al., 2017). However, in the 'sensitivity analysis', this cluster reemerges, with specific studies focusing on the links between inflammation and negative symptoms (Goldsmith et al., 2018;Goldsmith and Rapaport, 2020;Momtazmanesh et al., 2019). ...
Article
Full-text available
Research on negative symptoms of schizophrenia has received renewed interest since the 1980s. A scientometric analysis that objectively maps scientific knowledge, with changes in recent trends, is currently lacking. We searched the Web of Science Core Collection (WOSCC) on December 17, 2021 using relevant keywords. R-bibliometrix and CiteSpace were used to perform the analysis. We retrieved 27,568 references published between 1966 and 2022. An exponential rise in scientific interest was observed, with an average annual growth rate in publications of 16.56% from 1990 to 2010. The co-cited reference network that was retrieved presented 24 different clusters with a well-structured network (Q=0.7921; S=0.9016). Two distinct major research trends were identified: research on the conceptualization and treatment of negative symptoms. The latest trends in research on negative symptoms include evidence synthesis, nonpharmacological treatments, and computational psychiatry. Scientometric analyses provide a useful summary of changes in negative symptom research across time by identifying intellectual turning point papers and emerging trends. These results will be informative for systematic reviews, meta-analyses, and generating novel hypotheses.
... Complex trait association studies have rarely assess SVs 106 but there have been notable breakthroughs in autism, 35,107 schizophrenia 13,[108][109][110] and a few other disorders which have implicated a role for SVs in their etiology. [111][112][113][114] ...
... 275 Secondly, direct ascertainment of deletions around the amylase genes revealed their contribution to body mass index 276 and finally the characterisation of deletions of the complement component 4 (C4 ) genes helped elucidate the role of C4 expression in mediating schizophrenia. 109 These examples demonstrate the detrimental potential for SVs, and the importance of their characterisation along with complex traits. More recently, CNVs profiled on arrays have been revisited but with much larger sample sizes (>50,000), creating the opportunity to profile more rare variants. ...
Thesis
Structural Variants (SVs) are large scale rearrangements of the genome resulting in linear and spatial changes which can profoundly affect the function of the genome. SVs contribute the majority of nucleotide variation among human genomes by number of basepairs and have been linked to various diseases and traits including schizophrenia, autism and obesity. In this thesis whole genome sequence data at 15X coverage were generated using 12,354 samples from the INTERVAL cohort. A combination of Genome STRiP, Lumpy, CNVnator and svtools was used to call deletions, duplications and inversions. I implemented a stringent, tiered QC procedure to minimise false positives. For duplications and deletions I modelled sequential random forests on read alignment parameters, resulting in 88% sensitivity and 99% specificity for deletions, and 92% specificity and 55% sensitivity for duplications. Final tuning of the overall quality score was modelled to ensure that 90% of carrier genotypes were identical among duplicate samples. Finally, a graph-based procedure was used to collapse SVs with significant overlap in carriers and in genomic coordinates. The final callset consists of 123,801 sites, with each sample containing approximately 3,300 SVs. After rigorous QC, I compared the cohort to similar population cohorts including 1000 genomes project and Hall-SV. The cohort is sensitive - capturing 93% and 92% of common deletions from each cohort respectively. There is less sensitivity at duplications, where INTERVAL captures only 65% and 75% respectively. The majority of detected variants are rare: 95% have MAF < 0.01, and 49% are singletons, both figure are in line with expectations set by other similarly sized cohorts such as gnomAD-SV. Intergenic SVs are more common than all SVs affecting coding regions, and multi-gene SVs are the most rare class as expected. SVs are well tagged by SNPs - 88%, 97%, 93% and 46% of deletions, inversions, reference MEIs and duplications have at least one SNP in high LD (r2>0.8)- suggesting that genotyping of the SVs is high quality. We evaluated the contribution of SVs on a comprehensive range of phenotypes available in the cohort. These traits include a range of blood cell traits and phenotypes relating to inflammation and immunity including 1,348 metabolites, 92 plasma proteins and 125 full blood count traits. I modelled linear associations between single SVs and each trait, and identified 495 signals across 196 regions. After conditional analysis, I estimate SVs have a causal role in 34 signals, and are the lead variant in 54 signals. Chapter four details several examples of the contribution the SV is making to the association, describes potential genetic mechanisms, and gathers additional clinical data such as electronic health records and gene expression information to comprehensively describe the role of the SV at the association. Finally, there were 481 signals with genome wide significant SNPs present. At 339 signals, at least one SNP became non-significant when conditioning on the SV, suggesting that many SV signals have been accounted for by proxy previously. SVs are challenging to detect, however here I demonstrate the importance of including SVs in GWAS and further studies in understanding complex traits.
... While attempts have been made to characterise the effects of specific alleles [90], most contribute only a minimal degree of risk (median odds ratio 1.05), and are therefore unlikely to have major pathophysiological relevance in isolation [89]. However, functional consequences of increased genetic risk may be detected by assessing polygenic risk scores. ...
Article
Full-text available
Cognitive deficits are a core feature of schizophrenia, account for much of the impaired functioning associated with the disorder and are not responsive to existing treatments. In this review, we first describe the clinical presentation and natural history of these deficits. We then consider aetiological factors, highlighting how a range of similar genetic and environmental factors are associated with both cognitive function and schizophrenia. We then review the pathophysiological mechanisms thought to underlie cognitive symptoms, including the role of dopamine, cholinergic signalling and the balance between GABAergic interneurons and glutamatergic pyramidal cells. Finally, we review the clinical management of cognitive impairments and candidate novel treatments.
... A polymorphic TE insertion can be exapted as a functional element depending on its site of insertion within the genome, or it can disrupt an already existing enhancer 21 . Additionally, polymorphic TEs have been shown to be closely associated with complex phenotypes in GWAS investigations suggesting that polymorphic nonreference TEs (nrTEs) may contribute to disease phenotypes through cis-regulatory effects [22][23][24] . ...
Preprint
Full-text available
Transposable Elements (TEs) are mobile genetic elements that constitute half of the human genome. Recent studies suggest that polymorphic non-reference TEs (nrTEs) may contribute to cognitive diseases, such as schizophrenia, through a cis-regulatory effect. The aim of this work is to identify sets of nrTEs putatively linked to an increased risk of developing schizophrenia. To do so, we inspected the nrTE content of genomes from the Dorsolateral Prefrontal Cortex of schizophrenic and control individuals, and identified 38 nrTEs which possibly contribute to the emergence of this psychiatric disorder. Furthermore, we performed in silico functional inferences and found, for instance, that 9 of the 38 nrTEs act as expression/alternative splicing quantitative trait loci (eQTLs/sQTLs) in the brain, suggesting a possible role in shaping the human cognitive genome structure. Therefore, to our knowledge, this is the first attempt at identifying polymorphic nrTEs that can contribute to the functionality of the brain. Finally, we suggest that a neurodevelopmental genetic mechanism, which involves evolutionarily young nrTEs, can be the key to understanding the ethiopathogenesis of this complex disorder.
... A1 astrocytes, with longer dendrites in vivo and in vitro, lose the ability to promote neuronal survival, growth, synapse formation, and phagocytosis . In addition, A1 astrocytes secrete a saturated lipid (Guttenplan et al., 2021) that rapidly and selectively kills retinal ganglion cells, cortical neurons, spinal motor neurons, and human dopaminergic neurons, but not preganglionic and gamma motor neurons (Sekar et al., 2016). Oligodendrocytes form and maintain white matter myelin sheaths around axons in the CNS (Morrison et al., 2013). ...
Article
Full-text available
Astrocytes (AST) are abundant glial cells in the human brain, accounting for approximately 20–50% percent of mammalian central nervous system (CNS) cells. They display essential functions necessary to sustain the physiological processes of the CNS, including maintaining neuronal structure, forming the blood–brain barrier, coordinating neuronal metabolism, maintaining the extracellular environment, regulating cerebral blood flow, stabilizing intercellular communication, participating in neurotransmitter synthesis, and defending against oxidative stress et al. During the pathological development of brain tumors, stroke, spinal cord injury (SCI), neurodegenerative diseases, and other neurological disorders, astrocytes undergo a series of highly heterogeneous changes, which are called reactive astrocytes, and mediate the corresponding pathophysiological process. However, the pathophysiological mechanisms of reactive astrocytes and their therapeutic relevance remain unclear. The microRNAs (miRNAs) are essential for cell differentiation, proliferation, and survival, which play a crucial role in the pathophysiological development of CNS diseases. In this review, we summarize the regulatory mechanism of miRNAs on reactive astrocytes in CNS diseases, which might provide a theoretical basis for the diagnosis and treatment of CNS diseases.
... One example of this is the haplotypes of HLA-DRB1-HLA-DQA1-HLA-DQB1 greatly increased the risk of type 1 diabetes 39 . Another example is the identification of different alleles of the complement component 4 (C4) genes within the MHC region for the development of schizophrenia 40 . Even though we only demonstrated our targeted approach using GM12878 cells, it has been shown that a CRISPR-based strategy for the enrichment of HMW DNA molecules can be similarly applied to primary tissues, including peripheral blood mononuclear cells 11 and breast tumors 13 . ...
Article
Full-text available
Constructing high-quality haplotype-resolved genome assemblies has substantially improved the ability to detect and characterize genetic variants. A targeted approach providing readily access to the rich information from haplotype-resolved genome assemblies will be appealing to groups of basic researchers and medical scientists focused on specific genomic regions. Here, using the 4.5 megabase, notoriously difficult-to-assemble major histocompatibility complex (MHC) region as an example, we demonstrated an approach to construct haplotype-resolved assembly of the targeted genomic region with the CRISPR-based enrichment. Compared to the results from haplotype-resolved genome assembly, our targeted approach achieved comparable completeness and accuracy with reduced computing complexity, sequencing cost, as well as the amount of starting materials. Moreover, using the targeted assembled personal MHC haplotypes as the reference both improves the quantification accuracy for sequencing data and enables allele-specific functional genomics analyses of the MHC region. Given its highly efficient use of resources, our approach can greatly facilitate population genetic studies of targeted regions, and may pave a new way to elucidate the molecular mechanisms in disease etiology. Low-cost targeted approach to construct haplotype-resolved assemblies is needed to facilitate population genetic studies. Here, the authors demonstrate assembling high-quality MHC haplotypes with CRISPR-based enrichment and long-read sequencings.
... Finally, post-mortem findings of decreased dendritic spines and synaptic markers [85][86][87][88][89][90] and genetic evidence of variants in synaptic protein coding genes [91][92][93][94] suggest that synaptic dysfunction plays an important role in psychosis pathophysiology. Recent neuroimaging studies have provided in vivo evidence for synaptic density decreases in psychosis patients, using [ 11 C]UBC-J to image synaptic glycoprotein SV2A, 31,32 a putative marker of synaptic density. ...
Article
Full-text available
Background and Hypothesis Converging lines of evidence suggest that dysfunction of cortical GABAergic inhibitory interneurons is a core feature of psychosis. This dysfunction is thought to underlie neuroimaging abnormalities commonly found in patients with psychosis, particularly in the hippocampus. These include increases in resting cerebral blood flow (CBF) and glutamatergic metabolite levels, and decreases in ligand binding to GABAA α5 receptors and to the synaptic density marker synaptic vesicle glycoprotein 2A (SV2A). However, direct links between inhibitory interneuron dysfunction and these neuroimaging readouts are yet to be established. Conditional deletion of a schizophrenia susceptibility gene, the tyrosine kinase receptor Erbb4, from cortical and hippocampal inhibitory interneurons leads to synaptic defects, and behavioral and cognitive phenotypes relevant to psychosis in mice. Study Design Here, we investigated how this inhibitory interneuron disruption affects hippocampal in vivo neuroimaging readouts. Adult Erbb4 conditional mutant mice (Lhx6-Cre;Erbb4F/F, n = 12) and their wild-type littermates (Erbb4F/F, n = 12) were scanned in a 9.4T magnetic resonance scanner to quantify CBF and glutamatergic metabolite levels (glutamine, glutamate, GABA). Subsequently, we assessed GABAA receptors and SV2A density using quantitative autoradiography. Results Erbb4 mutant mice showed significantly elevated ventral hippccampus CBF and glutamine levels, and decreased SV2A density across hippocampus sub-regions compared to wild-type littermates. No significant GABAA receptor density differences were identified. Conclusions These findings demonstrate that specific disruption of cortical inhibitory interneurons in mice recapitulate some of the key neuroimaging findings in patients with psychosis, and link inhibitory interneuron deficits to non-invasive measures of brain function and neurochemistry that can be used across species.
... Genetic variations in complement component 4 (C4) copy number have been linked to the increased risk of schizophrenia. In addition, schizophrenia patients exhibit elevated C4 expression in the cerebral cortex (Rey et al., 2020; Schizophrenia Working Group of the Psychiatric Genomics, 2014; Sekar et al., 2016). Although the exact mechanism underlying schizophrenia is unknown, the neuropathology of patients' brains is characterized by reduced thickness and synaptic density in the cortex (Glantz and Lewis, 2000;Thompson et al., 2001) consistent with the idea that C4 overexpression leads to enhanced microglia-mediated synaptic engulfment. ...
Article
Full-text available
In the brain, the complement system plays a crucial role in the immune response and in synaptic elimination during normal development and disease. Here, we sought to identify pathways that modulate the production of complement component 4 (C4), recently associated with an increased risk of schizophrenia. To design a disease-relevant assay, we first developed a rapid and robust 3D protocol capable of producing large numbers of astrocytes from pluripotent cells. Transcriptional profiling of these astrocytes confirmed the homogeneity of this population of dorsal fetal-like astrocytes. Using a novel ELISA-based small-molecule screen, we identified epigenetic regulators, as well as inhibitors of intracellular signaling pathways, able to modulate C4 secretion from astrocytes. We then built a connectivity map to predict and validate additional key regulatory pathways, including one involving c-Jun-kinase. This work provides a foundation for developing therapies for CNS diseases involving the complement cascade.
... Our final article is a mini-review by Ferranti and Foster, which highlights a role for CB2 in schizophrenia, a disease becoming increasingly understood to possess inflammatory risk factors (Comer et al., 2020a) and microglia-mediated mechanisms (Sekar et al., 2016;Comer et al., 2020b). This article highlights that in addition to, or maybe through, inflammatory mediator signaling, a role for CB2 receptors in microglia on associated behaviors, such as contextual fear memory. ...
... While introns do not encode protein sequences, they can regulate gene expression, alternative splicing (28), and intron-mediated enhancement (29). For example, the genes coding for complements 4A (C4A) and 4B (C4B) are distinguished by the presence or absence of a human endogenous retroviral (HERV) insertion (intron 9) that expands the C4 gene from 14kb to 21kb without changing the C4 protein sequence; the C4-HERV sequence could increase the ratio of C4A to C4B expression, which was found to be strongly associated with schizophrenia (30). Accordingly, it is necessary to test whether rs532193193 present in the intron could influence the expression of SFT2D2 in a future study. ...
Article
Full-text available
Background The relative risk of GWAS-confirmed loci strongly associated with schizophrenia may be underestimated due to the decay of linkage disequilibrium between index SNPs and causal variants. This study is aimed to investigate schizophrenia-associated signals detected in the 1q24-25 region in order to identify a causal variant in LD with GWAS index SNPs, and the potential biological functions of the risk gene. Methods Re-genotyping analysis was performed in the 1q24-25 region that harbors three GWAS index SNPs associated with schizophrenia (rs10489202, rs11586522, and rs6670165) in total of 9801 case-control subjects of Chinese Han origin. Circulating autoantibody levels were assessed using an in-house ELISA against a protein derived fragment encoded by SFT2D2 in total of 682 plasma samples. Results A rare variant (rs532193193) in the SFT2D2 locus was identified to be strongly associated with schizophrenia. Compared with control subjects, patients with schizophrenia showed increased anti-SFT2D2 IgG levels. Receiver operating characteristic (ROC) analysis revealed an area under the ROC curve (AUC) of 0.803 with sensitivity of 28.57% against specificity of 95% for the anti-SFT2D2 IgG assay. Discussion Our findings indicate that SFT2D2 is a novel gene for risk of schizophrenia, while endogenous anti-SFT2D2 IgG may underlie the pathophysiology of the immunological aspects of schizophrenia.
... Доказательства наличия нейровоспаления, иммунных расстройств, системного воспаления и оксидативного стресса при ШЗ получены при изучении постмортального мозга, на экспериментальных животных, при клинических исследованиях и в полногеномных ассоциативных исследованиях (GWAS) [12,21,24,25,26,28]. Так, при обострениях ШЗ имеет место повышение уровня провоспалительных цитокинов в ликворе и крови, а также увеличение транскрипции белков иммунной системы в префронтальной коре мозга [12,21,24]. ...
Article
IL-17A is a proinflammatory cytokine involved in pathogenesis of some neuroinflammatory diseases of the brain. However, its role in schizophrenia is poorly understood. Currently, noninvasive neuroimaging techniques are widely used to assess abnormalities in brain morphology and interactions of neuronal networks in schizophrenia. The aim of this work was to study associations between IL-17A level and brain morphometric parameters in schizophrenia, in order to clarify immune factors of pathogenesis and search for biomarkers of unfavorable disease course. 45 patients with schizophrenia and 30 healthy volunteers were included into the study. The levels of cytokines (IL-5, IL-6, IL-8, IL-10, IL-17A) and inflammatory markers were determined by ELISA or multiplex analysis. MRI scans were performed with a Siemens Magnetom Verio 3T MRI scanner. We used Kruskal–Wallis test to assess significant differences in immunological parameters followed by Mann–Whitney paired comparison; Student test to assess the significance of differences in morphometric parameters of the brain; Fisher exact test to assess the differences in discrete variables, with the differences considered statistically significant at p < 0.05. IL-17A levels were found to be increased in schizophrenia. Its elevated content was associated with increased levels of C-reactive protein, IL-5, IL-6, IL-8, IL-10, and the presence of morphometric changes of frontal and temporal cortex in the patients. So far, the relationships between IL-17A levels, immunoinflammatory parameters and structural brain changes have not been studied in schizophrenia. In the present work, we found an association of elevated IL-17A levels with decreased cortical thickness in several brain regions, systemic inflammation and activation of Th2-link of adaptive immunity in the patients with schizophrenia. According to the literature, a number of brain areas, where cortical thickness was associated with IL-17A levels may be relevant to pathogenesis of the disease and, in particular, to the development of negative symptoms, including impoverishment of interests, speech, and emotions. The results are important for understanding the role of immune disorders in pathogenesis of schizophrenia, including structural changes of the brain, and suggest that IL-17A may be a biomarker of these disorders. Confirmation of associations between structural neuroimaging findings, laboratory markers of inflammation and immune disorders may provide the basis for new multidisciplinary approaches to the diagnosis and prognosis of schizophrenia.
... The MHC gene, which is located on chromosome 6, is tightly linked to immunity (15). Sekar et al. demonstrated the impact of a particular mutation of the Complement 4 (C4) gene, which produced the complement protein C4, on synaptic pruning during the crucial stages of brain development, thus increasing the risk of schizophrenia (16). Evidence has identified aberrant immune function not only in the earliest stage of illness, but also before the onset of the disease (17). ...
Article
Full-text available
Background Dysregulation of immunity, such as levels of inflammatory factors, has been regarded as a sign of schizophrenia. Changes in cytokine levels are not only described in the early onset of disease, but also observed in ultra-high risk (UHR) individuals. This study aimed to investigate the potential of cytokines as biomarkers for psychotic disorders and in individuals at UHR of developing a psychotic disorder in the future. Methods The Luminex liquid chip technology was used to detect the concentrations of Interferon-gamma (INF-γ), Interleukin (IL)-2, Interleukin (IL)-4, Interleukin (IL)-6, Interleukin (IL)-17, Interleukin-1beta (IL-1β), and Tumor Necrosis Factor-beta (TNF-β) in the plasma of all subjects. Meanwhile, the plasma level of Tumor Necrosis Factor-Alpha (TNF-α) was measured with the enzyme-linked immunosorbent assay (ELISA) kits. Then, the levels of these cytokines were compared among patients with Drug-naïve first-episode schizophrenia (FES; n = 40), UHR population (UHR; n = 49), and healthy controls (HCs; n = 30). Baseline cytokine levels were compared among UHR individuals who later transitioned (UHR-T; n = 14), those who did not transition (UHR-NT; n = 35), and HCs ( n = 30). Results Our analysis results showed that IL-1β levels were significantly higher in UHR group than HC group ( p = 0.015). Meanwhile, TNF-α concentration was significantly increased in FES group compared with HC group ( p = 0.027). IL-17 ( p = 0.04) and TNF-β ( p = 0.008) levels were significantly higher in UHR-T group compared with UHR-NT group. Conclusion In conclusion, our findings suggest that the immuno-inflammatory activation level is increased in the early stage of psychosis before psychotic conversion and the Drug-naïve FES. IL-1β and TNF-α are the representatives of the specific biomarkers for UHR and FES, respectively. IL-17 and TNF-β may be the potential selective predictive biomarkers for future transition in UHR individuals.
... First, Apoe is a major regulator of lipid homeostasis (e.g., Lanfranco et al., 2020), serving as a key player in fatty acid (FA) metabolism, by shuttling FA from neurons to astrocyte mitochondria where FAs are processed to produce ATP; the ATP produced in astrocytes then activates interneurons, driving increases in inhibitory transmission (Bowser and Khakh, 2004;Ioannou et al., 2019;Qi et al., 2021). Second, Apoe is directly involved in synapse elimination (Singhrao et al., 1999;Stevens et al., 2007;Schafer et al., 2012;Sekar et al., 2016;Dejanovic et al., 2018;Kang et al., 2018;Metaxas et al., 2019;Vukojicic et al., 2019;Wu et al., 2019;Yin et al., 2019;Datta et al., 2020;Györffy et al., 2020;Savage et al., 2020;Werneburg et al., 2020). Synapse elimination almost certainly drives forgetting, linking the effects observed here with classic (amnestic) PSI effects (Wang et al., 2020; for reviews see Davis and Squire, 1984;Hernandez and Abel, 2008;Kasai et al., 2021). ...
Article
Full-text available
Synaptic integrity and function depend on myriad proteins - labile molecules with finite lifetimes that need to be continually replaced with freshly synthesized copies. Here we describe experiments designed to expose synaptic (and neuronal) properties and functions that are particularly sensitive to disruptions in protein supply, identify proteins lost early upon such disruptions, and uncover potential, yet currently underappreciated failure points. We report here that acute suppressions of protein synthesis are followed within hours by reductions in spontaneous network activity levels, impaired oxidative phosphorylation and mitochondrial function, and, importantly, destabilization and loss of both excitatory and inhibitory postsynaptic specializations. Conversely, gross impairments in presynaptic vesicle recycling occur over longer time scales (days), as does overt cell death. Proteomic analysis identified groups of potentially essential ‘early-lost’ proteins including regulators of synapse stability, proteins related to bioenergetics, fatty acid and lipid metabolism, and, unexpectedly, numerous proteins involved in Alzheimer’s disease pathology and amyloid beta processing. Collectively, these findings point to neuronal excitability, energy supply and synaptic stability as early-occurring failure points under conditions of compromised supply of newly synthesized protein copies.
... C4A and C4B are two highly conserved isoforms of C4, which reside in the major histocompatibility complex (MHC) locus [25]. The previous study has shown that alleles increasing C4A expression correlate with increased SCZ risk, but alleles that increase C4B expression do not alter SCZ risk [26], and the plasma level of C4 is increased in patients with SCZ, as well as inversely correlated with the cortex thickness [27,28]. In vivo studies also showed the overexpression of C4A in mice would reduce cortical synapse density, increase microglial engulfment of synapses, and lead to behavioral changes in the mice [25]. ...
Article
Full-text available
Background Schizophrenia (SCZ) is a chronic and severe mental illness with no cure so far. Mendelian randomization (MR) is a genetic method widely used to explore etiologies of complex traits. In the current study, we aimed to identify novel proteins underlying SCZ with a systematic analytical approach. Methods We integrated protein quantitative trait loci (pQTLs) of the brain, cerebrospinal fluid (CSF), and plasma with the latest and largest SCZ genome-wide association study (GWAS) via a systematic analytical framework, including two-sample MR analysis, Steiger filtering analysis, and Bayesian colocalization analysis. Results The genetically determined protein level of C4A/C4B (OR = 0.70, p = 1.66E−07) in the brain and ACP5 (OR = 0.42, p = 3.73E−05), CNTN2 (OR = 0.62, p = 2.57E−04), and PLA2G7 (OR = 0.71, p = 1.48E−04) in the CSF was associated with a lower risk of SCZ, while the genetically determined protein level of TIE1 (OR = 3.46, p = 4.76E−05), BCL6 (OR = 3.63, p = 1.59E−07), and MICB (OR = 4.49, p = 2.31E−11) in the CSF were associated with an increased risk for SCZ. Pathway enrichment analysis indicated that genetically determined proteins suggestively associated with SCZ were enriched in the biological process of the immune response. Conclusion In conclusion, we identified one protein in the brain and six proteins in the CSF that showed supporting evidence of being potentially associated with SCZ, which could provide insights into future mechanistic studies to find new treatments for the disease. Our results also supported the important role of neuroinflammation in the pathogenesis of SCZ.
... Data analysis, not One-way ANOVA. 2 Chi-square test. 3 Scheffe's post hoc test. ...
Article
Background and hypothesis: Gut microbiota alterations have been reported in severe mental illness (SMI) but fewer studies have probed for signs of gut barrier disruption and inflammation. We hypothesized that gut leakage of microbial products due to intestinal inflammation could contribute to systemic inflammasome activation in SMI. Study design: We measured plasma levels of the chemokine CCL25 and soluble mucosal vascular addressin cell adhesion molecule-1 (sMAdCAM-1) as markers of T cell homing, adhesion and inflammation in the gut, lipopolysaccharide binding protein (LBP) and intestinal fatty acid binding protein (I-FABP) as markers of bacterial translocation and gut barrier dysfunction, in a large SMI cohort (n = 567) including schizophrenia (SCZ, n = 389) and affective disorder (AFF, n = 178), relative to healthy controls (HC, n = 418). We assessed associations with plasma IL-18 and IL-18BPa and leukocyte mRNA expression of NLRP3 and NLRC4 as markers of inflammasome activation. Study results: Our main findings were: (1) higher levels of sMAdCAM-1 (P = .002), I-FABP (P = 7.6E-11), CCL25 (P = 9.6E-05) and LBP (P = 2.6E-04) in SMI compared to HC in age, sex, BMI, CRP and freezer storage time adjusted analysis; (2) the highest levels of sMAdCAM-1 and CCL25 (both P = 2.6E-04) were observed in SCZ and I-FABP (P = 2.5E-10) and LBP (3) in AFF; and (3), I-FABP correlated with IL-18BPa levels and LBP correlated with NLRC4. Conclusions: Our findings support that intestinal barrier inflammation and dysfunction in SMI could contribute to systemic inflammation through inflammasome activation.
... Other GCN determination methods based on the multiple elements of RCCX CNV such as the paralog ratio test and the high resolution melting PCR have been described [30,45]. Digital PCR has been used for the GCN determination of C4 paralogous gene variants and HERV-K(C4) CNV [46], but the methodological performance of the digital PCR has not been evaluated on the genetic elements of RCCX CNV yet. ...
Article
Full-text available
Quantitative PCR (qPCR) is used for the determination of gene copy number (GCN). GCNs contribute to human disorders, and characterize copy number variation (CNV). The single laboratory method validations of duplex qPCR assays with hydrolysis probes on CYP21A1P and CYP21A2 genes, residing a CNV (RCCX CNV) and related to congenital adrenal hyperplasia, were performed using 46 human genomic DNA samples. We also performed the verifications on 5 qPCR assays for the genetic elements of RCCX CNV; C4A , C4B , CNV breakpoint, HERV-K(C4) CNV deletion and insertion alleles. Precision of each qPCR assay was under 1.01 CV%. Accuracy (relative error) ranged from 4.96±4.08% to 9.91±8.93%. Accuracy was not tightly linked to precision, but was significantly correlated with the efficiency of normalization using the RPPH1 internal reference gene (Spearman’s ρ: 0.793–0.940, p>0.0001), ambiguity (ρ = 0.671, p = 0.029) and misclassification (ρ = 0.769, p = 0.009). A strong genomic matrix effect was observed, and target-singleplex (one target gene in one assay) qPCR was able to appropriately differentiate 2 GCN from 3 GCN at best. The analysis of all GCNs from the 7 qPCR assays using a multiplex approach increased the resolution of differentiation, and produced 98% of GCNs unambiguously, and all of which were in 100% concordance with GCNs measured by Southern blot, MLPA and aCGH. We conclude that the use of an internal (in one assay with the target gene) reference gene, the use of allele-specific primers or probes, and the multiplex approach (in one assay or different assays) are crucial for GCN determination using qPCR or other methods.
... The most highly enriched cellular component terms were major histocompatibility complex (MHC) class protein complexes, enriched with upregulated genes. MHC molecules participate in negatively regulation of synaptic plasticity [28][29][30][31], and overexpression of MHC complex I protein can lead to a decreased ability to form synapses, which has been linked to several central nervous system (CNS) disorders, including autism spectrum disorders (ASDs) and schizophrenia [32,33]. MHC may exert its effects by interacting with inflammatory cytokines that are involved in epilepsy [33,34]. ...
Article
Full-text available
Abstract Background DBA/1 mice have a higher susceptibility to generalized audiogenic seizures (AGSz) and seizure-induced respiratory arrest (S-IRA) than C57/BL6 mice. The gene expression profile might be potentially related to this difference. This study aimed to investigate the susceptibility difference in AGSz and S-IRA between DBA/1 and C57BL/6 mice by profiling long noncoding RNAs (lncRNAs) and mRNA expression. Methods We compared lncRNAs and mRNAs from the brainstem of the two strains with Arraystar Mouse lncRNA Microarray V3.0 (Arraystar, Rockville, MD). Gene Ontology (GO) and pathway analyses were performed to determine the potentially related biological functions and pathways based on differentially expressed mRNAs. qRT–PCR was carried out to validate the results. Results A total of 897 lncRNAs and 438 mRNAs were differentially expressed (fold change ≥2, P
... It has been argued that common small-effect risk variants identified in GWASwhich explain around one-third of the genetic liability to schizophrenia (Legge et al., 2021)may provide solid therapeutic targets to inform precision medicine approaches (Gandal et al., 2016). A landmark study reported common variants that increase C4A expression in the brain in correlation with increased schizophrenia risk (Sekar et al., 2016), possibly through enhanced synaptic pruning (Yilmaz et al., 2021). Despite this exciting discovery, deciphering the genes and associated mechanisms influenced by common variants in schizophrenia has been difficult. ...
Article
Full-text available
Schizophrenia is a serious mental illness affecting 0.7% of the world's population. Despite over 50 years of schizophrenia drug identification and development, there have been no fundamental advances in the treatment of schizophrenia since the 1980s. Complex genetic aetiology and elusive pathomechanisms have made it difficult for researchers to develop models that sufficiently reflect pathophysiology to support effective drug discovery. However, recent large-scale, well-powered genomic studies have identified risk genes that represent tractable entry points to decipher disease mechanisms in heterogeneous patient populations and develop targeted treatments. Replicating schizophrenia-associated gene variants in mouse models is an important strategy to start understanding their pathogenicity and role in disease biology. Furthermore, longitudinal studies in a wide range of genetic mouse models from early postnatal life are required to assess the progression of this disease through developmental stages to improve early diagnostic strategies and enable preventative measures. By expanding and refining our approach to schizophrenia research, we can improve prevention strategies and treatment of this debilitating disease.
... In schizophrenia, the complement system is a key intervenient in synapse elimination by microglia, in particular the components C4 and C3. The former, which is increased in the hippocampus of patients (in neurons and synapses) [53], activates C3, that binds to a receptor exclusively expressed by myeloid cells, including microglia [26,54,55]. Other authors demonstrated that C4 variants associated with schizophrenia, increase C3 deposition in neurons [51], synaptic engulfment by microglia [51,56] and reduce the connectivity in the PFC of prepubertal rats [56]. ...
Article
Full-text available
Schizophrenia is a psychiatric disorder with significant impact on individuals and society. The current pharmacologic treatment, which principally alleviates psychosis, is focused on neurotransmitters modulation, relying on drugs with severe side effects and ineffectiveness in a significant percentage of cases. Therefore, and due to difficulties inherent to diagnosis and treatment, it is vital to reassess alternative cellular and molecular drug targets. Distinct risk factors – genetic, developmental, epigenetic, and environmental – have been associated with disease onset and progression, giving rise to the proposal of different pathophysiological mechanisms and putative pharmacological targets. Immunity is involved and, particularly microglia – innate immune cells of the central nervous system, critically involved in brain development – have captured attention as cellular players. Microglia undergo marked morphologic and functional alterations in the human disease, as well as in animal models of schizophrenia, as reported in several original papers. We cluster the main findings of clinical studies by groups of patients: (1) at ultra-high risk of psychosis, (2) with a first episode of psychosis or recent-onset schizophrenia, and (3) with chronic schizophrenia; in translational studies, we highlight the time window of appearance of particular microglia alterations in the most well studied animal model in the field (maternal immune activation). The organization of clinical and translational findings based on schizophrenia-associated microglia changes in different phases of the disease course may help defining a temporal pattern of microglia changes and may drive the design of novel therapeutic strategies.
... These studies have been particularly valuable for schizophreniaa highly heritable condition [1] with poorly understood etiology. Recently, such studies have yielded unambiguous associations between schizophrenia and both common and rare genetic variants [2][3][4], some of which have led to promising etiologic hypotheses [5]. Increasing sample sizes is expected to continue to yield further genetic risk variants. ...
Article
Full-text available
Genome-wide studies are among the best available tools for identifying etiologic processes underlying psychiatric disorders such as schizophrenia. However, it is widely recognized that disorder heterogeneity may limit genetic insights. Identifying phenotypes indexing genetic differences among patients with non-affective psychotic disorder will improve genome-wide studies of these disorders. The present study systematically reviews existing literature to identify phenotypes that index genetic differences among patients with schizophrenia and related disorders. We systematically reviewed family-based studies and genome-wide molecular-genetic studies investigating whether phenotypic variation in patients with non-affective psychotic disorders (according to DSM or equivalent systems) was associated with genome-wide genetic variation (PROSPERO number CRD42019136169). An electronic database search of PubMed, EMBASE, and PsycINFO from inception until 17 May 2019 resulted in 4347 published records. These records included a total of 813 relevant analyses from 264 articles. Two independent raters assessed the quality of all analyses based on methodologic rigor and power. We found moderate to strong evidence for a positive association between genetic/familial risk for non-affective psychosis and four phenotypes: early age of onset, negative/deficit symptoms, chronicity, and functional impairment. Female patients also tended to have more affected relatives. Severity of positive symptoms was not associated with genetic/familial risk for schizophrenia. We suggest that phenotypes with the most evidence for reflecting genetic difference in participating patients should be measured in future large-scale genetic studies of schizophrenia to improve power to discover causal variants and to facilitate discovery of modifying genetic variants.
... Many loci identified from GWAS are intergenic and locate to non-protein-coding regions of the genome 3 . Although the functional mechanisms of some variants have been reported 4,5 , most genomic loci have not been studied and little is known about target genes, pathways or mechanisms of action. There are multiple reports that GWAS variants are overrepresented in sequences that regulate gene expression 3 . ...
Preprint
Full-text available
The majority of disease-associated variants identified through genome-wide association studies (GWAS) are located outside of protein-coding regions, and are collectively overrepresented in sequences that regulate gene expression. Prioritizing candidate regulatory variants and potential biological mechanisms for further functional experiments, such as genome editing, can be challenging, especially in regions with a high number of variants in strong linkage disequilibrium or multiple proximal gene targets. Improved annotation of the regulatory genome can help identify promising variants and target genes for further experiments and accelerate translation of identified GWAS loci into important biological insights. To advance this area, we developed FORGEdb (https://forge2.altiusinstitute.org/files/forgedb.html), a web-based tool that can rapidly integrate data for individual genetic variants, providing information on associated regulatory elements, transcription factor (TF) binding sites and target genes. FORGEdb uses annotations derived from data across a wide range of biological samples to delineate the regulatory context for each variant at the cell type level. Different datatypes, including CADD scores, expression quantitative trait loci (eQTLs), activity-by-contact (ABC) interactions, Contextual Analysis of TF Occupancy (CATO) scores, TF motifs, DNase I hotspots, histone mark ChIP-seq and chromatin states in FORGEdb are made available for >37 million variants, and these annotations are integrated into a FORGEdb score to guide assignment of functional importance. The inclusion of a wide range of genomic annotations, such as ABC interactions and CADD scores, provides a comprehensive resource for researchers seeking to prioritize variants for functional validation. In summary, FORGEdb provides an expansive and unique resource for the analysis of genomic variants associated with complex traits and diseases.
... Complement 4 (C4) promotes the activation of C3, making C3 firmly attached to its target, mediating the phagocytosis of the labeled target by microglia (152). Therefore, C4 deficiency led to synaptic elimination aberrant (153). In a complement-focused study, patients with ASD have significantly higher degrees of C4B variant deficiency, compared with controls (154), it could also find that C1q, C3, and C4 mRNA levels were visibly reduced in the prefrontal cortex (155). ...
Article
Full-text available
Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by variable impairment of social communication and repetitive behaviors, highly restricted interests, and/or sensory behaviors beginning early in life. Many individuals with ASD have dysfunction of microglia, which may be closely related to neuroinflammation, making microglia play an important role in the pathogenesis of ASD. Mounting evidence indicates that microglia, the resident immune cells of the brain, are required for proper brain function, especially in the maintenance of neuronal circuitry and control of behavior. Dysfunction of microglia will ultimately affect the neural function in a variety of ways, including the formation of synapses and alteration of excitatory–inhibitory balance. In this review, we provide an overview of how microglia actively interact with neurons in physiological conditions and modulate the fate and functions of synapses. We put a spotlight on the multi-dimensional neurodevelopmental roles of microglia, especially in the essential influence of synapses, and discuss how microglia are currently thought to influence ASD progression.
... In addition, the enrichment of these associations in biological processes such as nervous system development, regulation of neuron differentiation, or neurogenesis, were of special interest within the framework of the neurodevelopmental hypothesis of SZ. Moreover, the C4A locus in the Major Histocompatibility Complex (MHC) in chromosome 6, which is the locus with the top association with SZ, has been shown to participate in synaptic pruning, determination of synapse density, and microglial engulfment of synapses (Sekar et al. 2016;Yilmaz et al. 2021). ...
Article
Full-text available
Since more than 3 decades, schizophrenia (SZ) has been regarded as a neurodevelopmental disorder. The neurodevelopmental hypothesis proposes that SZ is associated with genetic and environmental risk factors, which influence connectivity in neuronal circuits during vulnerable developmental periods. We carried out a non-systematic review of genetic/environmental factors that increase SZ risk in light of its neurodevelopmental hypothesis. We also reviewed the potential impact of SZ-related environmental and genetic risk factors on grey and white matter pathology and brain function based on magnetic resonance imaging and post-mortem studies. Finally, we reviewed studies that have used patient-derived neuronal models to gain knowledge of the role of genetic and environmental factors in early developmental stages. Taken together, these studies indicate that a variety of environmental factors may interact with genetic risk factors during the pre- or postnatal period and/or during adolescence to induce symptoms of SZ in early adulthood. These risk factors induce disturbances of macro- and microconnectivity in brain regions involving the prefrontal, temporal and parietal cortices and the hippocampus. On the molecular and cellular level, a disturbed synaptic plasticity, loss of oligodendrocytes and impaired myelination have been shown in brain regions of SZ patients. These cellular/histological phenotypes are related to environmental risk factors such as obstetric complications, maternal infections and childhood trauma and genetic risk factors identified in recent genome-wide association studies. SZ-related genetic risk may contribute to active processes interfering with synaptic plasticity in the adult brain. Advances in stem cell technologies are providing promising mechanistic insights into how SZ risk factors impact the developing brain. Further research is needed to understand the timing of the different complex biological processes taking place as a result of the interplay between genetic and environmental factors.
... Despite the lack of knowledge regarding the mechanisms that lead to these disorders, compelling evidence suggests that the immune system, particularly inflammation and autoimmunity, plays a role in the origin and disease course of mental disorders [5]. The most associated locus in SCZ genome-wide association studies (GWAS) maps to the major histocompatibility complex on chromosome 6, specifically the complement 4 A (C4A) locus [6,7]. ...
Article
Full-text available
The diagnostic criteria for schizophrenia (SCZ) and bipolar disorder (BD) are based on clinical assessments of symptoms. In this pilot study, we applied high-throughput antibody-based protein profiling to serum samples of healthy controls and individuals with SCZ and BD with the aim of identifying differentially expressed proteins in these disorders. Moreover, we explored the influence of polygenic burden for SCZ and BD on the serum levels of these proteins. Serum samples from 113 individuals with SCZ and 125 with BD from the PsyCourse Study and from 44 healthy controls were analyzed by using a set of 155 antibodies in an antibody-based assay targeting a selected panel of 95 proteins. For the cases, genotyping and imputation were conducted for DNA samples and SCZ and BD polygenic risk scores (PRS) were calculated. Univariate linear and logistic models were used for association analyses. The comparison between SCZ and BD revealed two serum proteins that were significantly elevated in BD after multiple testing adjustment: “complement C9” and “Interleukin 1 Receptor Accessory Protein”. Moreover, the first principal component of variance in the proteomics dataset differed significantly between SCZ and BD. After multiple testing correction, SCZ-PRS, BD-PRS, and SCZ-vs-BD–PRS were not significantly associated with the levels of the individual proteins or the values of the proteome principal components indicating no detectable genetic effects. Overall, our findings contribute to the evidence suggesting that the analysis of circulating proteins could lead to the identification of distinctive biomarkers for SCZ and BD. Our investigation warrants replication in large-scale studies to confirm these findings.
... It has been suggested that microenvironment interaction, especially the abnormal interaction between glial cells and synapses, is one of the neuropathological mechanisms underlying Rett syndrome, Down syndrome, spinal muscular atrophy, and other diseases (10). More and more recent studies have found that the communication between neurons and glial cells is related to several neuropsychiatric and neurodegenerative diseases, such as schizophrenia (11). ...
Article
Full-text available
Background Synapse-associated proteins (SAPs) play important roles in central nervous system (CNS) tumors. Recent studies have reported that γ-aminobutyric acidergic (GABAergic) synapses also play critical roles in the development of gliomas. However, biomarkers of GABAergic synapses in low-grade gliomas (LGGs) have not yet been reported. Methods mRNA data from normal brain tissue and gliomas were obtained from the Genotype-Tissue Expression (GTEx) and The Cancer Genome Atlas (TCGA) databases, respectively. A validation dataset was also obtained from the Chinese Glioma Genome Atlas (CGGA) database. The expression patterns of GABAergic synapse-related genes (GSRGs) were evaluated with difference analysis in LGGs. Then, a GABAergic synapse-related risk signature (GSRS) was constructed with least absolute shrinkage and selection operator (LASSO) Cox regression analysis. According to the expression value and coefficients of identified GSRGs, the risk scores of all LGG samples were calculated. Univariate and multivariate Cox regression analyses were conducted to evaluate related risk scores for prognostic ability. Correlations between characteristics of the tumor microenvironment (TME) and risk scores were explored with single-sample gene set enrichment analysis (ssGSEA) and immunity profiles in LGGs. The GSRS-related pathways were investigated by gene set variation analysis (GSVA). Real-time PCR and the Human Protein Atlas (HPA) database were applied to explore related expression of hub genes selected in the GSRS. Results Compared with normal brain samples, 25 genes of 31 GSRGs were differentially expressed in LGG samples. A constructed five-gene GSRS was related to clinicopathological features and prognosis of LGGs by the LASSO algorithm. It was shown that the risk score level was positively related to the infiltrating level of native CD4 T cells and activated dendritic cells. GSVA identified several cancer-related pathways associated with the GSRS, such as P53 pathways and the JAK-STAT signaling pathway. Additionally, CA2, PTEN, OXTR, and SLC6A1 (hub genes identified in the GSRS) were regarded as the potential predictors in LGGs. Conclusion A new five-gene GSRS was identified and verified by bioinformatics methods. The GSRS provides a new perspective in LGG that may contribute to more accurate prediction of prognosis of LGGs.
... The current study is the first to observe that the complement cascade as the top biological pathway is related with change in omega-3 PUFAs in a CHR population. These observations provide vital evidence in omega-3-based treatment response in psychosis for the following reasons: (i) Genetic studies have reported evidence of a potentially causal relationship between increased long chain PUFA concentrations and lowered risk of psychosis [64,65]; (ii) Complement related immune activity has been found to be involved in the pathophysiology of schizophrenia [66][67][68][69][70]; and (iii) in rodents, Madore et al. found a link between maternal omega-3 PUFA and microglia associated synaptic pruning through complement protein activity in off-springs [15]. However several studies have observed the beneficial effects of omega-3 PUFAs in various inflammatory and metabolic conditions [14,15,[71][72][73][74], one recent study by Manousopoulou et al., explored the influence of dietary intake of omega-3 PUFAs on the plasma proteome of patients with fatty liver disease. ...
Article
Full-text available
Preliminary evidence indicates beneficial effects of omega-3 polyunsaturated fatty acids (PUFAs) in early psychosis. The present study investigates the molecular mechanism of omega-3 PUFA-associated therapeutic effects in clinical high-risk (CHR) participants. Plasma samples of 126 CHR psychosis participants at baseline and 6-months follow-up were included. Plasma protein levels were quantified using mass spectrometry and erythrocyte omega-3 PUFA levels were quantified using gas chromatography. We examined the relationship between change in polyunsaturated PUFAs (between baseline and 6-month follow-up) and follow-up plasma proteins. Using mediation analysis, we investigated whether plasma proteins mediated the relationship between change in omega-3 PUFAs and clinical outcomes. A 6-months change in omega-3 PUFAs was associated with 24 plasma proteins at follow-up. Pathway analysis revealed the complement and coagulation pathway as the main biological pathway to be associated with change in omega-3 PUFAs. Moreover, complement and coagulation pathway proteins significantly mediated the relationship between change in omega-3 PUFAs and clinical outcome at follow-up. The inflammatory protein complement C5 and protein S100A9 negatively mediated the relationship between change in omega-3 PUFAs and positive symptom severity, while C5 positively mediated the relationship between change in omega-3 and functional outcome. The relationship between change in omega-3 PUFAs and cognition was positively mediated through coagulation factor V and complement protein C1QB. Our findings provide evidence for a longitudinal association of omega-3 PUFAs with complement and coagulation protein changes in the blood. Further, the results suggest that an increase in omega-3 PUFAs decreases symptom severity and improves cognition in the CHR state through modulating effects of complement and coagulation proteins.
... In addition, Toxoplasma infection can increase neural cell death, alteration in neural gene expression and the release of inflammatory mediators in neurospheres [132]. Thus, this infection could be correlated with psychiatric diseases and human CNS disorders including Alzheimer, dementia, depression and schizophrenia [54, [133][134][135][136]. On the other hand, due to the overexpression of complement components in Toxoplasma-infected brain [53,63], and the upregulation of C1q, C3, and C4b in some mental disorders including schizophrenia, alzheimer's disease, aging and multiple sclerosis [54, [137][138][139][140], it could be interesting to focus on therapeutic studies that share more information regarding the possible correlations between parasitic disease including toxoplasmosis and mental disorders and their association with the complement system. ...
Article
Full-text available
The complement system exerts crucial functions both in innate immune responses and adaptive humoral immunity. This pivotal system plays a major role dealing with pathogen invasions including protozoan parasites. Different pathogens including parasites have developed sophisticated strategies to defend themselves against complement killing. Some of these strategies include the employment, mimicking or inhibition of host’s complement regulatory proteins, leading to complement evasion. Therefore, parasites are proven to use the manipulation of the complement system to assist them during infection and persistence. Herein, we attempt to study the interaction´s mechanisms of some prominent infectious protozoan parasites including Plasmodium, Toxoplasma, Trypanosoma, and Leishmania dealing with the complement system. Moreover, several crucial proteins that are expressed, recruited or hijacked by parasites and are involved in the modulation of the host´s complement system are selected and their role for efficient complement killing or lysis evasion is discussed. In addition, parasite’s complement regulatory proteins appear as plausible therapeutic and vaccine targets in protozoan parasitic infections. Accordingly, we also suggest some perspectives and insights useful in guiding future investigations.
Chapter
Schizophrenia is a disturbance in an individual's mood, thinking, and behavior, characterized by a distorted sense of reality. DSM‐5 organizes the various types of schizophrenia into a gradient ranging from the mildest form to the most severe that represents a significant impairment of behavior. Sociological interest in schizophrenia is based upon the social factors contributing to its origin and its connection to social class position.
Article
Neuropathic pain is a debilitating condition resulting from damage to the nervous system. Imbalance of spinal excitation and inhibition has been proposed to contribute to neuropathic pain. However, the structural basis of this imbalance remains unknown. Using a preclinical model of neuropathic pain, we show that microglia selectively engulf spinal synapses that are formed by central neurons and spare those of peripheral sensory neurons. Furthermore, we reveal that removal of inhibitory and excitatory synapses exhibits distinct temporal patterns, in which microglia-mediated inhibitory synapse removal precedes excitatory synapse removal. We also find selective and gradual increase in complement depositions on dorsal horn synapses that corresponds to the temporal pattern of microglial synapse pruning activity and type-specific synapse loss. Together, these results define a specific role for microglia in the progression of neuropathic pain pathogenesis and implicate these immune cells in structural remodeling of dorsal horn circuitry.
Article
There is a consensus in the field that microglia play a prominent role in neurodevelopmental processes like synaptic pruning and neuronal network maturation. Thus, a current momentum of associating microglia deficits with neurodevelopmental disorders (NDDs) emerged. This concept is challenged by rodent studies and clinical data. Intriguingly, reduced numbers of microglia or altered microglial functions do not necessarily lead to overt NDD phenotypes, and neuropsychiatric symptoms seem to develop primarily in adulthood. Hence, it remains open for discussion whether microglia are truly indispensable for healthy neurodevelopment. Here, we critically discuss the role of microglia in synaptic pruning and highlight area- and age dependency. We propose an updated model of microglia-mediated synaptic pruning in the context of NDDs and discuss the potential of targeting microglia for treatment of these disorders.
Chapter
In this chapter, I review studies in nonhuman primates that emulate the circuit failure in prefrontal cortex responsible for working memory and cognitive control deficits in schizophrenia. These studies have characterized how synaptic malfunction, typically induced by blockade of NMDAR, disrupts neural function and computation in prefrontal networks to explain errors in cognitive tasks that are seen in schizophrenia. This work is finding causal relationships between pathogenic events of relevance to schizophrenia at vastly different levels of scale, from synapses, to neurons, local, circuits, distributed networks, computation, and behavior. Pharmacological manipulation, the dominant approach in primate models, has limited construct validity for schizophrenia pathogenesis, as the disease results from a complex interplay between environmental, developmental, and genetic factors. Genetic manipulation replicating schizophrenia risk is more advanced in rodent models. Nonetheless, gene manipulation in nonhuman primates is rapidly advancing, and primate developmental models have been established. Integration of large scale neural recording, genetic manipulation, and computational modeling in nonhuman primates holds considerable potential to provide a crucial schizophrenia model moving forward. Data generated by this approach is likely to fill several crucial gaps in our understanding of the causal sequence leading to schizophrenia in humans. This causal chain presents a vexing problem largely because it requires understanding how events at very different levels of scale relate to one another, from genes to circuits to cognition to social interactions. Nonhuman primate models excel here. They optimally enable discovery of causal relationships across levels of scale in the brain that are relevant to cognitive deficits in schizophrenia. The mechanistic understanding of prefrontal circuit failure they promise to provide may point the way to more effective therapeutic interventions to restore function to prefrontal networks in the disease.
Article
Recent evidence indicates that DDR1 participates in myelination and that variants of DDR1 are associated with decreased cognitive processing speed (PS) in schizophrenia (SZ). Here, we explored whether DDR1 variants were associated with PS in subjects diagnosed with an early psychosis (EP), a condition often preceding SZ. Data from two Spanish independent samples (from Reus and Santander) including patients with EP (n = 75 and n = 312, respectively) and healthy controls (HCs; n = 57 and n = 160) were analyzed. The Trail Making Test part A was used to evaluate PS. Participants underwent genotyping to identify DDR1 variants rs1264323 and rs2267641. Cross-sectional data were analyzed with general linear models and longitudinal data were analyzed using mixed models. We examined the combined rs1264323AA-rs2267641AC/CC genotypes (an SZ-risk combination) on PS. The SZ-risk combined genotypes were associated with increased PS in EP patients but not in HCs in the cross-sectional analysis. In the longitudinal analysis, the SZ-risk combined genotypes were significantly associated with increased PS in both HCs and EP patients throughout the 10-year follow-up but no genotype × time interaction was observed. These results provide further evidence that DDR1 is involved in cognition and should be replicated with other samples.
Article
Microglia are multifaceted cells that act as immune sentinels, with important roles in pathological events, but also as integral contributors to the normal development and function of neural circuits. In the last decade, our understanding of the contributions these cells make to synaptic health and dysfunction has expanded at a dizzying pace. Here we review the known mechanisms that govern the dynamics of microglia allowing these motile cells to interact with synapses, and recruit microglia to specific sites on neurons. We then review the molecular signals that may underlie the function of microglia in synaptic remodeling. The emerging picture from the literature suggests that microglia are highly sensitive cells, reacting to neuronal signals with dynamic and specific actions tuned to the need of specific synapses and networks.
Article
Background: Cognitive disturbances in schizophrenia have been linked to a lower density of dendritic spines on pyramidal neurons in the prefrontal cortex (PFC). Complement component C4, which has previously been found at higher levels in schizophrenia, marks synapses for phagocytosis by microglia. Thus, elevated consumption of dendritic spines by microglia mediated through excessive complement activity may play a role in lower spine density in schizophrenia. However, it is unclear if microglia themselves have the molecular capacity for enhanced phagocytosis of spines in schizophrenia. Methods: Transcript levels for complement components and microglia-specific phagocytic markers were quantified using quantitative PCR in the PFC of 62 matched pairs of schizophrenia and unaffected comparison subjects and in antipsychotic-exposed monkeys. Results: Relative to comparison subjects, schizophrenia subjects had higher mRNA levels for C4 (+154 %); C1q (+69 %), which initiates the classical complement pathway that includes C4; and for microglia-specific markers that enable phagocytic activity including TAM receptor tyrosine kinases Axl (+27 %) and MerTK (+27 %) and lysosome-associated glycoprotein CD68 (+27 %) (all p ≤ .042). Transcript levels for microglial phagocytic markers were correlated with C4 mRNA levels in schizophrenia subjects (all r ≥ 0.31, p ≤ .015). We also found further evidence consistent with microglial activation in schizophrenia, including higher mRNA levels for THIK1 (TWIK-related halothane-inhibited potassium channel: +30 %) and lower mRNA levels for the purinergic receptor P2Y12 (-27 %) (all p ≤ .016). Transcript levels were unchanged in antipsychotic-exposed monkeys. Conclusions: These results are consistent with the presence of increased complement activity and an elevated molecular capacity of microglia for phagocytosis in the same schizophrenia subjects.
Article
Alterations of radiomic features (RFs) in gray matter are observed in schizophrenia, of which the results may be limited by small study samples and confounding effects of drug therapies. We tested for RFs alterations of gray matter in never-treated first-episode schizophrenia (NT-FES) patients and examined their associations with known gene expression profiles. RFs were examined in the first sample with 197 NT-FES and 178 healthy controls (HCs) and validated in the second independent sample (90 NT-FES and 74 HCs). One-year follow-up data were available from 87 patients to determine whether RFs were associated with treatment outcomes. Associations between identified RFs in NT-FES and gene expression profiles were evaluated. NT-FES exhibited alterations of 30 RFs, with the greatest involvement of microstructural heterogeneity followed by measures of brain region shape. The identified RFs were mainly located in the central executive network, frontal-temporal network, and limbic system. Two baseline RFs with the involvement of microstructural heterogeneity predicted treatment response with moderate accuracy (78% for the first sample, 70% for the second sample). Exploratory analyses indicated that RF alterations were spatially related to the expression of schizophrenia risk genes. In summary, the present findings link brain abnormalities in schizophrenia with molecular features and treatment response.
Article
Tryptophan is an essential amino acid absorbed by the gut depending on a homoeostatic microbiome. Up to 95% of unbound tryptophan is converted into tryptophan catabolites (TRYCATs) through the kynurenine system. Recent studies identified conflicting associations between altered levels of TRYCATs and genetic polymorphisms in major depressive disorder (MDD), schizophrenia (SCZ), and bipolar disorder (BD). This meta-analysis aimed to understand how tryptophan catabolic pathways are altered in MDD, SCZ, and BD. When compared to healthy controls, participants with MDD had moderately lower levels of tryptophan associated with a moderate increase of kynurenine/tryptophan ratios and no differences in kynurenine. While significant differences were found in SCZ for any of the TRYCATs, studies on kynurenic acid found opposing directions of effect sizes depending on the sample source. Unique changes in levels of TRYCATs were also observed in BD. Dynamic changes in levels of cytokines and other immune/inflammatory elements modulate the transcription and activity of kynurenine system enzymes, which lastly seems to be impacting glutamatergic neurotransmission via N-methyl-D-aspartate and α-7 nicotine receptors.
Article
Full-text available
Neurodevelopmental disorders arise due to various risk factors that can perturb different stages of brain development, and a combinatorial impact of these risk factors programs the phenotype in adulthood. While modeling the complete phenotype of a neurodevelopmental disorder is challenging, individual developmental perturbations can be successfully modeled in vivo in animals and in vitro in human cellular models. Nevertheless, our limited knowledge of human brain development restricts modeling strategies and has raised questions of how well a model corresponds to human in vivo brain development. Recent progress in high-resolution analysis of human tissue with single-cell and spatial omics techniques has enhanced our understanding of the complex events that govern the development of the human brain in health and disease. This new knowledge can be utilized to improve modeling of neurodevelopmental disorders and pave the way to more accurately portraying the relevant developmental perturbations in disease models.
Article
Несмотря на достижения современной науки, серьезной проблемой в управлении сахарным диабетом 1 типа (СД1) у детей и подростков является преодоление последствий, связанных с осложнениями данного заболевания. Быстрое развитие микрососудистых диабетических осложнений (ретинопатии, нейропатии, нефропатии) остается существенным препятствием в поддержании высокого качества жизни и социальной адаптации молодых пациентов, что позволяет обратиться к изучению иммунных механизмов, участвующих в процессах повреждения микроциркуляторного русла в условиях дисметаболических отклонений, сопутствующих СД1. Цель работы. Оценить роль нарушений цитокинового баланса в сыворотке крови в формировании микроангиопатий у подростков с СД1. Материалы и м етоды. Обследовано 140 подростков с СД1 типа возраста 14-18 лет, которые были распределены на 2 группы: I группа –пациенты с уровнем гликированного гемоглобина (HbA1c) более 9% (n=65), и II группа – подростки с уровнем HbA1C≤ 9,0% (n=75). Каждая группа была подразделена на подгруппы: Iа (n=50), IIа (n=38) – подростки с диабетической ретинопатией, нефропатией или нейропатией; Iб (n=15), IIб (n=37) – с неосложненным течением заболевания. Группу контроля составили 36 подростков с нормальной массой тела, без нарушений углеводного обмена и отягощенной по сахарному диабету наследственности. Определение уровней TNF-α, IL-1β, VCAM-1, фракталкина в сыворотке крови проводили методом иммуноферментного анализа с использованием тест-систем «BIOMEDICAGRUPPE» (Германия), «RayBiotech» (США). Результаты. Формирование микроангиопатий у подростков с различным уровнем гликемического контроля ассоциировано с повышением сывороточной концентрации медиаторов, вовлеченных в неоангиогенез и процессы ремоделирования сосудистой стенки: TNF- α , IL-1β, VCAM-1, при сравнении с группой контроля (p<0,05) и статистически значимым снижением фракталкина у всех подростков с осложненным и неосложненным течением СД1. Проведенное исследование позволило установить, что развитие микрососудистых осложнений у подростков с СД1 сопряжено с нарушением иммунного реагирования с тенденцией направленности цитокинового баланса по Тh1 типу, усилением процессов межклеточного взаимодействия, дисбалансом биорегуляторных молекул и способствует формированию воспалительного режима иммунорегуляции. В ыводы. Выявленные закономерности наряду с оценкой показателей метаболического контроля, позволят персонифицировать подходы к ранней диагностике микрососудистых осложнений у подростков с СД1 и предотвратить их дальнейшую прогрессию.
Preprint
Full-text available
Over 100 genetic loci harbor schizophrenia associated variants, yet how these common variants confer risk is uncertain. The CommonMind Consortium has sequenced dorsolateral prefrontal cortex RNA from schizophrenia cases (n=258) and control subjects (n=279), creating the largest publicly available resource to date of gene expression and its genetic regulation; ∼5 times larger than the latest release of GTEx. Using this resource, we find that ∼20% of the schizophrenia risk loci have common variants that could explain regulation of brain gene expression. In five loci, these variants modulate expression of a single gene: FURIN, TSNARE1, CNTN4, CLCN3 or SNAP91 . Experimentally altered expression of three of them, FURIN , TSNARE1 , and CNTN4 , perturbs the proliferation and apoptotic index of neural progenitors and leads to neuroanatomical deficits in zebrafish. Furthermore, shRNA mediated knock-down of FURIN1 in neural progenitor cells derived from human induced pluripotent stem cells produces abnormal neural migration. Although 4.2% of genes (N = 693) display significant differential expression between cases and controls, 44% show some evidence for differential expression. All fold changes are ≤ 1.33, and an independent cohort yields similar differential expression for these 693 genes (r = 0.58). These findings are consistent with schizophrenia being highly polygenic, as has been reported in investigations of common and rare genetic variation. Co-expression analyses identify a gene module that shows enrichment for genetic associations and is thus relevant for schizophrenia. Taken together, these results pave the way for mechanistic interpretations of genetic liability for schizophrenia and other brain diseases.
Chapter
For the past 40 years, our team has conducted a unique program of research investigating the prenatal risks for schizophrenia and related adult psychiatric disorders. The New England Family Study is a long-term prospective cohort study of over 16,000 individuals followed from the prenatal period for over 50 years. This chapter summarizes several major phases and findings from this work, highlighting recent results on maternal prenatal bacterial infections and brain imaging. Implications regarding the causes and potential prevention of major psychotic disorders are discussed.
Book
Full-text available
Ligun N.V., Dorokhov V.B., Putilov A.A., Torshin V.I. Sleep of poor and good nappers under the afternoon exposure to very weak electromagnetic fields. In: B. Kryzhanovsky, W. Dunin-Barkowski, V. Redko, Y. Tiumentsev (eds.) Advances in Neural Computation, Machine Learning, and Cognitive Research VI: Selected Papers from the XXIV International Conference on Neuroinformatics, October 17-21, 2022, Moscow, Russia. Springer book series: Studies in Computational Intelligence, 2023, Volume 1064, Pages 255—262. https://doi.org/10.1007/978-3-031-19032-2. https://link.springer.com/chapter/10.1007/978-3-031-19032-2_27
Article
ADGRG1 (also called GPR56) plays critical roles in brain development and wiring, including cortical lamination, central nervous system (CNS) myelination, and developmental synaptic refinement. However, the underlying mechanism(s) in mediating such diverse functions is not fully understood. Here, we investigate the function of one specific alternative splicing isoform, the GPR56 splice variant 4 (S4), to test the hypothesis that alternative splicing variants of GPR56 in part support its different functions. We created a new transgenic mouse line, Gpr56∆S4 , using CRISPR/Cas9, in which GPR56 S4 was deleted. Detailed phenotype analyses show that Gpr56∆S4 mice manifest no deficits in cortical architecture and CNS myelination compared to controls. Excitingly, they present significantly increased synapse densities, decreased synapse engulfment by microglia, and impaired eye-segregation. Taken together, our findings support that the GPR56 S4 variant is dispensable for cortical development and CNS myelination but is essential for microglia-mediated synaptic pruning.
Article
The complement gene C4A has been implicated in schizophrenia through genome-wide association studies (GWAS) and, in vitro and animal studies. However, few studies have examined epigenetic modification of the C4A gene in schizophrenia. We hypothesized that DNA methylation levels of the C4A gene are altered in schizophrenia, and the interaction between DNA methylation and the copy number (CN) of the C4A gene leads to the higher C4 levels seen in schizophrenia. In this study, C4A DNA methylation levels, C4A CN and C4 levels were measured in the peripheral blood of 183 schizophrenia cases (SZ) and 212 healthy controls (HC). The Positive and Negative Syndrome Scale (PANSS) was used to determine the severity of psychopathology in the cases. MethyLight assay was used to measure DNA methylation levels and droplet digital polymerase chain reaction (ddPCR) was used for the calculated copy number (cCN) determination. The cCNs were also grouped into copy number variation (CNV) types: deletion, normal, and duplication. Methylation levels were measured as percentage of methylated reference (PMR) values. Both C4A PMR (rs = 0.469, p < 0.001) and C4A cCN (rs = 0.210, p < 0.001) were positively correlated with C4 levels, which in turn were higher in SZ than HC. However, we found no difference in C4A PMR values or C4A CNV types between SZ and HC. Our results suggest the potential involvement of an epigenetic modification and CNV of C4A in the upregulation of complement C4 in schizophrenia.
Article
Full-text available
Thousands of genomic segments appear to be present in widely varying copy numbers in different human genomes. We developed ways to use increasingly abundant whole-genome sequence data to identify the copy numbers, alleles and haplotypes present at most large multiallelic CNVs (mCNVs). We analyzed 849 genomes sequenced by the 1000 Genomes Project to identify most large (>5-kb) mCNVs, including 3,878 duplications, of which 1,356 appear to have 3 or more segregating alleles. We find that mCNVs give rise to most human variation in gene dosage-seven times the combined contribution of deletions and biallelic duplications-and that this variation in gene dosage generates abundant variation in gene expression. We describe 'runaway duplication haplotypes' in which genes, including HPR and ORM1, have mutated to high copy number on specific haplotypes. We also describe partially successful initial strategies for analyzing mCNVs via imputation and provide an initial data resource to support such analyses.
Article
Full-text available
Whole exome sequencing has proven to be a powerful tool for understanding the genetic architecture of human disease. Here we apply it to more than 2,500 simplex families, each having a child with an autistic spectrum disorder. By comparing affected to unaffected siblings, we show that 13% of de novo missense mutations and 43% of de novo likely gene-disrupting (LGD) mutations contribute to 12% and 9% of diagnoses, respectively. Including copy number variants, coding de novo mutations contribute to about 30% of all simplex and 45% of female diagnoses. Almost all LGD mutations occur opposite wild-type alleles. LGD targets in affected females significantly overlap the targets in males of lower intelligence quotient (IQ), but neither overlaps significantly with targets in males of higher IQ. We estimate that LGD mutation in about 400 genes can contribute to the joint class of affected females and males of lower IQ, with an overlapping and similar number of genes vulnerable to contributory missense mutation. LGD targets in the joint class overlap with published targets for intellectual disability and schizophrenia, and are enriched for chromatin modifiers, FMRP-associated genes and embryonically expressed genes. Most of the significance for the latter comes from affected females.
Article
Full-text available
Schizophrenia is a highly heritable disorder. Genetic risk is conferred by a large number of alleles, including common alleles of small effect that might be detected by genome-wide association studies. Here we report a multi-stage schizophrenia genome-wide association study of up to 36,989 cases and 113,075 controls. We identify 128 independent associations spanning 108 conservatively defined loci that meet genome-wide significance, 83 of which have not been previously reported. Associations were enriched among genes expressed in brain, providing biological plausibility for the findings. Many findings have the potential to provide entirely new insights into aetiology, but associations at DRD2 and several genes involved in glutamatergic neurotransmission highlight molecules of known and potential therapeutic relevance to schizophrenia, and are consistent with leading pathophysiological hypotheses. Independent of genes expressed in brain, associations were enriched among genes expressed in tissues that have important roles in immunity, providing support for the speculated link between the immune system and schizophrenia.
Article
Full-text available
The formation of precise connections between retina and lateral geniculate nucleus (LGN) involves the activity-dependent elimination of some synapses, with strengthening and retention of others. Here we show that the major histocompatibility complex (MHC) class I molecule H2-D(b) is necessary and sufficient for synapse elimination in the retinogeniculate system. In mice lacking both H2-K(b) and H2-D(b) (K(b)D(b)(-/-)), despite intact retinal activity and basal synaptic transmission, the developmentally regulated decrease in functional convergence of retinal ganglion cell synaptic inputs to LGN neurons fails and eye-specific layers do not form. Neuronal expression of just H2-D(b) in K(b)D(b)(-/-) mice rescues both synapse elimination and eye-specific segregation despite a compromised immune system. When patterns of stimulation mimicking endogenous retinal waves are used to probe synaptic learning rules at retinogeniculate synapses, long-term potentiation (LTP) is intact but long-term depression (LTD) is impaired in K(b)D(b)(-/-) mice. This change is due to an increase in Ca(2+)-permeable AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors. Restoring H2-D(b) to K(b)D(b)(-/-) neurons renders AMPA receptors Ca(2+) impermeable and rescues LTD. These observations reveal an MHC-class-I-mediated link between developmental synapse pruning and balanced synaptic learning rules enabling both LTD and LTP, and demonstrate a direct requirement for H2-D(b) in functional and structural synapse pruning in CNS neurons.
Article
Full-text available
Schizophrenia is a common disease with a complex aetiology, probably involving multiple and heterogeneous genetic factors. Here, by analysing the exome sequences of 2,536 schizophrenia cases and 2,543 controls, we demonstrate a polygenic burden primarily arising from rare (less than 1 in 10,000), disruptive mutations distributed across many genes. Particularly enriched gene sets include the voltage-gated calcium ion channel and the signalling complex formed by the activity-regulated cytoskeleton-associated scaffold protein (ARC) of the postsynaptic density, sets previously implicated by genome-wide association and copy-number variation studies. Similar to reports in autism, targets of the fragile X mental retardation protein (FMRP, product of FMR1) are enriched for case mutations. No individual gene-based test achieves significance after correction for multiple testing and we do not detect any alleles of moderately low frequency (approximately 0.5 to 1 per cent) and moderately large effect. Taken together, these data suggest that population-based exome sequencing can discover risk alleles and complements established gene-mapping paradigms in neuropsychiatric disease.
Article
Full-text available
Inherited alleles account for most of the genetic risk for schizophrenia. However, new (de novo) mutations, in the form of large chromosomal copy number changes, occur in a small fraction of cases and disproportionally disrupt genes encoding postsynaptic proteins. Here we show that small de novo mutations, affecting one or a few nucleotides, are overrepresented among glutamatergic postsynaptic proteins comprising activity-regulated cytoskeleton-associated protein (ARC) and N-methyl-d-aspartate receptor (NMDAR) complexes. Mutations are additionally enriched in proteins that interact with these complexes to modulate synaptic strength, namely proteins regulating actin filament dynamics and those whose messenger RNAs are targets of fragile X mental retardation protein (FMRP). Genes affected by mutations in schizophrenia overlap those mutated in autism and intellectual disability, as do mutation-enriched synaptic pathways. Aligning our findings with a parallel case-control study, we demonstrate reproducible
Article
Full-text available
Significance We identified a human-specific endogenous retroviral insert (hsERV) that acts as an enhancer for human PRODH , hsERV_PRODH. PRODH encodes proline dehydrogenase, which is involved in neuromediator synthesis in the CNS. We show that the hsERV_PRODH enhancer acts synergistically with the CpG island of PRODH and is regulated by methylation. We detected high PRODH expression in the hippocampus, which was correlated with the undermethylated state of this enhancer. PRODH regulatory elements provide neuron-specific transcription in hippocampal cells, and the mechanism of hsERV_PRODH enhancer activity involves the binding of transcriptional factor SOX2. Because PRODH is associated with several neurological disorders, we hypothesize that the human-specific regulation of PRODH by hsERV_PRODH may have played a role in human evolution by upregulating the expression of this important CNS-specific gene.
Article
Full-text available
Immune molecules, including complement proteins C1q and C3, have emerged as critical mediators of synaptic refinement and plasticity. Complement localizes to synapses and refines the developing visual system through C3-dependent microglial phagocytosis of synapses. Retinal ganglion cells (RGCs) express C1q, the initiating protein of the classical complement cascade, during retinogeniculate refinement; however, the signals controlling C1q expression and function remain elusive. Previous work implicated an astrocyte-derived factor in regulating neuronal C1q expression. Here we identify retinal transforming growth factor (TGF)-β as a key regulator of neuronal C1q expression and synaptic pruning in the developing visual system. Mice lacking TGF-β receptor II (TGFβRII) in retinal neurons had reduced C1q expression in RGCs and reduced synaptic localization of complement, and phenocopied refinement defects observed in complement-deficient mice, including reduced eye-specific segregation and microglial engulfment of RGC inputs. These data implicate TGF-β in regulating neuronal C1q expression to initiate complement- and microglia-mediated synaptic pruning.
Article
Full-text available
DNA sequence variation within human leukocyte antigen (HLA) genes mediate susceptibility to a wide range of human diseases. The complex genetic structure of the major histocompatibility complex (MHC) makes it difficult, however, to collect genotyping data in large cohorts. Long-range linkage disequilibrium between HLA loci and SNP markers across the major histocompatibility complex (MHC) region offers an alternative approach through imputation to interrogate HLA variation in existing GWAS data sets. Here we describe a computational strategy, SNP2HLA, to impute classical alleles and amino acid polymorphisms at class I (HLA-A, -B, -C) and class II (-DPA1, -DPB1, -DQA1, -DQB1, and -DRB1) loci. To characterize performance of SNP2HLA, we constructed two European ancestry reference panels, one based on data collected in HapMap-CEPH pedigrees (90 individuals) and another based on data collected by the Type 1 Diabetes Genetics Consortium (T1DGC, 5,225 individuals). We imputed HLA alleles in an independent data set from the British 1958 Birth Cohort (N = 918) with gold standard four-digit HLA types and SNPs genotyped using the Affymetrix GeneChip 500 K and Illumina Immunochip microarrays. We demonstrate that the sample size of the reference panel, rather than SNP density of the genotyping platform, is critical to achieve high imputation accuracy. Using the larger T1DGC reference panel, the average accuracy at four-digit resolution is 94.7% using the low-density Affymetrix GeneChip 500 K, and 96.7% using the high-density Illumina Immunochip. For amino acid polymorphisms within HLA genes, we achieve 98.6% and 99.3% accuracy using the Affymetrix GeneChip 500 K and Illumina Immunochip, respectively. Finally, we demonstrate how imputation and association testing at amino acid resolution can facilitate fine-mapping of primary MHC association signals, giving a specific example from type 1 diabetes.
Article
Full-text available
Schizophrenia is a severe mental disorder with a lifetime risk of about 1%, characterized by hallucinations, delusions and cognitive deficits, with heritability estimated at up to 80%(1,2). We performed a genome-wide association study of 3,322 European individuals with schizophrenia and 3,587 controls. Here we show, using two analytic approaches, the extent to which common genetic variation underlies the risk of schizophrenia. First, we implicate the major histocompatibility complex. Second, we provide molecular genetic evidence for a substantial polygenic component to the risk of schizophrenia involving thousands of common alleles of very small effect. We show that this component also contributes to the risk of bipolar disorder, but not to several non-psychiatric diseases.
Article
Full-text available
The human RCCX is a common multiallelic copy number variation locus whose number of segments varies between one and four in a chromosome. The monomodular form normally comprises four functional genes, but in duplicated RCCX segments generally only the gene-encoding complement component C4 produces a protein. C4 genes can code either for a C4A or a C4B isotype protein and exhibit dichotomous size variation. Distinct RCCX variants show association with numerous diseases; however, identification of the basis of these associations is often challenging, not least because the RCCX is localized in the major histocompatibility complex (MHC) region, a genomic area characterized by exceedingly long-range linkage disequilibrium. Here we present a detailed analysis on RCCX variants and their relationship with so-called 'ancestral' or 'conserved extended' MHC haplotypes in healthy Caucasians. In addition to former investigations, precise order and size of all C4A and C4B genes were determined even in trimodular RCCX structures. Considering C4 copy numbers, length, isotype specificity and CYP21A2 copy numbers, we have identified 15 distinct RCCX variants and described the RCCX structures involved in 29 repeatedly occurring MHC haplotypes. The findings should become a useful tool for future RCCX- and MHC-related disease association studies.
Article
Full-text available
Schizophrenia is a neurodevelopmental disorder whose clinical features include impairments in perception, cognition and motivation. These impairments reflect alterations in neuronal circuitry within and across multiple brain regions that are due, at least in part, to deficits in dendritic spines, the site of most excitatory synaptic connections. Dendritic spine alterations have been identified in multiple brain regions in schizophrenia, but are best characterized in layer 3 of the neocortex, where pyramidal cell spine density is lower. These spine deficits appear to arise during development, and thus are likely the result of disturbances in the molecular mechanisms that underlie spine formation, pruning, and/or maintenance. Each of these mechanisms may provide insight into novel therapeutic targets for preventing or repairing the alterations in neural circuitry that mediate the debilitating symptoms of schizophrenia. This article is part of a Special Issue entitled: Spine Plasticity and Pathology in Brain Disorders.
Article
Full-text available
The genetic association of the major histocompatibility complex (MHC) to rheumatoid arthritis risk has commonly been attributed to alleles in HLA-DRB1. However, debate persists about the identity of the causal variants in HLA-DRB1 and the presence of independent effects elsewhere in the MHC. Using existing genome-wide SNP data in 5,018 individuals with seropositive rheumatoid arthritis (cases) and 14,974 unaffected controls, we imputed and tested classical alleles and amino acid polymorphisms in HLA-A, HLA-B, HLA-C, HLA-DPA1, HLA-DPB1, HLA-DQA1, HLA-DQB1 and HLA-DRB1, as well as 3,117 SNPs across the MHC. Conditional and haplotype analyses identified that three amino acid positions (11, 71 and 74) in HLA-DRβ1 and single-amino-acid polymorphisms in HLA-B (at position 9) and HLA-DPβ1 (at position 9), which are all located in peptide-binding grooves, almost completely explain the MHC association to rheumatoid arthritis risk. This study shows how imputation of functional variation from large reference panels can help fine map association signals in the MHC.
Article
Full-text available
Schizophrenia is a complex disorder, caused by both genetic and environmental factors and their interactions. Research on pathogenesis has traditionally focused on neurotransmitter systems in the brain, particularly those involving dopamine. Schizophrenia has been considered a separate disease for over a century, but in the absence of clear biological markers, diagnosis has historically been based on signs and symptoms. A fundamental message emerging from genome-wide association studies of copy number variations (CNVs) associated with the disease is that its genetic basis does not necessarily conform to classical nosological disease boundaries. Certain CNVs confer not only high relative risk of schizophrenia but also of other psychiatric disorders. The structural variations associated with schizophrenia can involve several genes and the phenotypic syndromes, or the 'genomic disorders', have not yet been characterized. Single nucleotide polymorphism (SNP)-based genome-wide association studies with the potential to implicate individual genes in complex diseases may reveal underlying biological pathways. Here we combined SNP data from several large genome-wide scans and followed up the most significant association signals. We found significant association with several markers spanning the major histocompatibility complex (MHC) region on chromosome 6p21.3-22.1, a marker located upstream of the neurogranin gene (NRGN) on 11q24.2 and a marker in intron four of transcription factor 4 (TCF4) on 18q21.2. Our findings implicating the MHC region are consistent with an immune component to schizophrenia risk, whereas the association with NRGN and TCF4 points to perturbation of pathways involved in brain development, memory and cognition.
Article
Full-text available
A small number of rare, recurrent genomic copy number variants (CNVs) are known to substantially increase susceptibility to schizophrenia. As a consequence of the low fecundity in people with schizophrenia and other neurodevelopmental phenotypes to which these CNVs contribute, CNVs with large effects on risk are likely to be rapidly removed from the population by natural selection. Accordingly, such CNVs must frequently occur as recurrent de novo mutations. In a sample of 662 schizophrenia proband-parent trios, we found that rare de novo CNV mutations were significantly more frequent in cases (5.1% all cases, 5.5% family history negative) compared with 2.2% among 2623 controls, confirming the involvement of de novo CNVs in the pathogenesis of schizophrenia. Eight de novo CNVs occurred at four known schizophrenia loci (3q29, 15q11.2, 15q13.3 and 16p11.2). De novo CNVs of known pathogenic significance in other genomic disorders were also observed, including deletion at the TAR (thrombocytopenia absent radius) region on 1q21.1 and duplication at the WBS (Williams-Beuren syndrome) region at 7q11.23. Multiple de novos spanned genes encoding members of the DLG (discs large) family of membrane-associated guanylate kinases (MAGUKs) that are components of the postsynaptic density (PSD). Two de novos also affected EHMT1, a histone methyl transferase known to directly regulate DLG family members. Using a systems biology approach and merging novel CNV and proteomics data sets, systematic analysis of synaptic protein complexes showed that, compared with control CNVs, case de novos were significantly enriched for the PSD proteome (P=1.72 × 10⁻⁶. This was largely explained by enrichment for members of the N-methyl-D-aspartate receptor (NMDAR) (P=4.24 × 10⁻⁶) and neuronal activity-regulated cytoskeleton-associated protein (ARC) (P=3.78 × 10⁻⁸) postsynaptic signalling complexes. In an analysis of 18 492 subjects (7907 cases and 10 585 controls), case CNVs were enriched for members of the NMDAR complex (P=0.0015) but not ARC (P=0.14). Our data indicate that defects in NMDAR postsynaptic signalling and, possibly, ARC complexes, which are known to be important in synaptic plasticity and cognition, play a significant role in the pathogenesis of schizophrenia.
Article
Full-text available
We examined the role of common genetic variation in schizophrenia in a genome-wide association study of substantial size: a stage 1 discovery sample of 21,856 individuals of European ancestry and a stage 2 replication sample of 29,839 independent subjects. The combined stage 1 and 2 analysis yielded genome-wide significant associations with schizophrenia for seven loci, five of which are new (1p21.3, 2q32.3, 8p23.2, 8q21.3 and 10q24.32-q24.33) and two of which have been previously implicated (6p21.32-p22.1 and 18q21.2). The strongest new finding (P = 1.6 × 10(-11)) was with rs1625579 within an intron of a putative primary transcript for MIR137 (microRNA 137), a known regulator of neuronal development. Four other schizophrenia loci achieving genome-wide significance contain predicted targets of MIR137, suggesting MIR137-mediated dysregulation as a previously unknown etiologic mechanism in schizophrenia. In a joint analysis with a bipolar disorder sample (16,374 affected individuals and 14,044 controls), three loci reached genome-wide significance: CACNA1C (rs4765905, P = 7.0 × 10(-9)), ANK3 (rs10994359, P = 2.5 × 10(-8)) and the ITIH3-ITIH4 region (rs2239547, P = 7.8 × 10(-9)).
Article
Full-text available
The major mechanism for generating diversity of neuronal connections beyond their genetic determination is the activity-dependent stabilization and selective elimination of the initially overproduced synapses [Changeux JP, Danchin A (1976) Nature 264:705-712]. The largest number of supranumerary synapses has been recorded in the cerebral cortex of human and nonhuman primates. It is generally accepted that synaptic pruning in the cerebral cortex, including prefrontal areas, occurs at puberty and is completed during early adolescence [Huttenlocher PR, et al. (1979) Brain Res 163:195-205]. In the present study we analyzed synaptic spine density on the dendrites of layer IIIC cortico-cortical and layer V cortico-subcortical projecting pyramidal neurons in a large sample of human prefrontal cortices in subjects ranging in age from newborn to 91 y. We confirm that dendritic spine density in childhood exceeds adult values by two- to threefold and begins to decrease during puberty. However, we also obtained evidence that overproduction and developmental remodeling, including substantial elimination of synaptic spines, continues beyond adolescence and throughout the third decade of life before stabilizing at the adult level. Such an extraordinarily long phase of developmental reorganization of cortical neuronal circuitry has implications for understanding the effect of environmental impact on the development of human cognitive and emotional capacities as well as the late onset of human-specific neuropsychiatric disorders.
Article
Full-text available
Schizophrenia, a devastating psychiatric disorder, has a prevalence of 0.5-1%, with high heritability (80-85%) and complex transmission. Recent studies implicate rare, large, high-penetrance copy number variants in some cases, but the genes or biological mechanisms that underlie susceptibility are not known. Here we show that schizophrenia is significantly associated with single nucleotide polymorphisms (SNPs) in the extended major histocompatibility complex region on chromosome 6. We carried out a genome-wide association study of common SNPs in the Molecular Genetics of Schizophrenia (MGS) case-control sample, and then a meta-analysis of data from the MGS, International Schizophrenia Consortium and SGENE data sets. No MGS finding achieved genome-wide statistical significance. In the meta-analysis of European-ancestry subjects (8,008 cases, 19,077 controls), significant association with schizophrenia was observed in a region of linkage disequilibrium on chromosome 6p22.1 (P = 9.54 x 10(-9)). This region includes a histone gene cluster and several immunity-related genes--possibly implicating aetiological mechanisms involving chromatin modification, transcriptional regulation, autoimmunity and/or infection. These results demonstrate that common schizophrenia susceptibility alleles can be detected. The characterization of these signals will suggest important directions for research on susceptibility mechanisms.
Article
Full-text available
Schizophrenia is a complex disorder, caused by both genetic and environmental factors and their interactions. Research on pathogenesis has traditionally focused on neurotransmitter systems in the brain, particularly those involving dopamine. Schizophrenia has been considered a separate disease for over a century, but in the absence of clear biological markers, diagnosis has historically been based on signs and symptoms. A fundamental message emerging from genome-wide association studies of copy number variations (CNVs) associated with the disease is that its genetic basis does not necessarily conform to classical nosological disease boundaries. Certain CNVs confer not only high relative risk of schizophrenia but also of other psychiatric disorders. The structural variations associated with schizophrenia can involve several genes and the phenotypic syndromes, or the 'genomic disorders', have not yet been characterized. Single nucleotide polymorphism (SNP)-based genome-wide association studies with the potential to implicate individual genes in complex diseases may reveal underlying biological pathways. Here we combined SNP data from several large genome-wide scans and followed up the most significant association signals. We found significant association with several markers spanning the major histocompatibility complex (MHC) region on chromosome 6p21.3-22.1, a marker located upstream of the neurogranin gene (NRGN) on 11q24.2 and a marker in intron four of transcription factor 4 (TCF4) on 18q21.2. Our findings implicating the MHC region are consistent with an immune component to schizophrenia risk, whereas the association with NRGN and TCF4 points to perturbation of pathways involved in brain development, memory and cognition.
Article
Full-text available
A remarkable difference has been observed between the reactivity of the two forms of human complement component C4. C4B binds twice as effectively as C4A to antibody-coated red cells, but the reverse occurs with protein-antigen complexes. C4B reacts much more effectively with hydroxyl groups than C4A and this is reversed for reaction with amino groups in spite of the very small difference in amino acid sequence between the two forms of C4. No other differences in stability, activation or inactivation were observed. These findings emphasise the biological advantage of the duplication of the C4 gene in its reaction with a wide range of antigenic structures. The correlation of the presence of different forms of C4 with susceptibility to autoimmune diseases may be explicable by these big differences in binding reactivity.
Article
Full-text available
The development of functional connections between the axons of retinal ganglion cells and the neurons of the dorsal lateral geniculate nucleus (LGNd) of fetal and neonatal cats was studied using an in vitro assay. Extracellular microelectrode recordings of single units were made from histologically identified sites in the LGNd of isolated diencephalon preparations between embryonic day 39 ( E39 ) and postnatal day 2 (P2). (Gestation is 65 days in the cat.) Postsynaptic units activated by electrical stimulation of one or both optic nerves were found at all ages tested from E39 onwards. Over 90% of the units studied in the fetal preparations received convergent excitation from both optic nerves, compared with roughly half of the units studied in the neonatal optic nerves, compared with roughly half of the units studied in the neonatal preparations. Inhibition was detected in the LGNd of the neonatal preparations, but in only the oldest of the fetal preparations ( E59 ). This physiological change from predominantly convergent excitation to an adult-like mixture of excitation and inhibition seen at birth coincides with the change from mixed to segregated afferent input from the two eyes seen anatomically ( Shatz , C. J. (1983) J. Neurosci . 3: 482-499). These results indicate that attainment of the adult pattern of retinogeniculate connectivity involves the elimination of already functional synapses.
Article
Full-text available
Converging evidence indicates that a profound reorganization of human brain function takes place during adolescence: the amount of deep sleep and the rate of brain metabolism fall sharply; the latency of certain event-related potentials declines; the capacity to recover function after brain injury diminishes; and adult problem-solving "power" appears. A reduction in cortical synaptic density has recently been observed and might account for all of these changes. Such synaptic "pruning" may be analogous to the programmed elimination of neural elements in very early development. A defect in this maturational process may underlie those cases of schizophrenia that emerge during adolescence.
Article
Full-text available
Several lines of evidence suggest that autoimmune mechanisms might contribute to the development of schizophrenia. Important factors involved in immune responses in man include the human leukocyte antigens and components of the complement system. In the present study we attempted to confirm a positive association between a homozygous deficiency in complement factor C4B and schizophrenia as previously reported. We also determined parental genotypes in a subset of our schizophrenic patients to test the hypothesis of a genetic mechanism depending on the mother's genotype. C4B deficiency was found in similar frequency among patients (n = 176) and controls (n = 145). There was also no increased frequency of C4B deficiency in the mothers of schizophrenic patients. Our study does not support a widespread or consistent association between a deficiency in complement component C4B and schizophrenia.
Article
Full-text available
A pilot study of the density of dendritic spines on pyramidal neurons in layer III of human temporal and frontal cerebral neocortex in schizophrenia. Postmortem material from a group of eight prospectively diagnosed schizophrenic patients, five archive schizophrenic patients, 11 non-schizophrenic controls, and one patient with schizophrenia-like psychosis, thought to be due to substance misuse, was impregnated with a rapid Golgi method. Spines were counted on the dendrites of pyramidal neurons in temporal and frontal association areas, of which the soma was in layer III (which take part in corticocortical connectivity) and which met strict criteria for impregnation quality. Altogether 25 blocks were studied in the schizophrenic group and 21 in the controls. If more than one block was examined from a single area, the counts for that area were averaged. All measurements were made blind: diagnoses were only disclosed by a third party after measurements were completed. Possible confounding affects of coexisting Alzheimer's disease were taken into account, as were the effects of age at death and postmortem interval. There was a significant (p<0.001) reduction in the numerical density of spines in schizophrenia (276/mm in control temporal cortex and 112/mm in schizophrenic patients, and 299 and 101 respectively in the frontal cortex). An analysis of variance, taking out effects of age at death and postmortem interval, which might have explained the low spine density for some of the schizophrenic patients, did not affect the significance of the results. The results support the concept of there being a defect in the fine structure of dendrites of pyramidal neurons, involving loss of spines, in schizophrenia and may help to explain the loss of cortical volume without loss of neurons in this condition, although the effect of neuroleptic drugs cannot be ruled out.
Article
Full-text available
The symptoms of schizophrenia imply disruption to brain systems supporting higher-order cognitive activity, but whether these systems are impacted differentially against a background of diffuse cortical gray-matter deficit remains ambiguous. Some unaffected first-degree relatives of schizophrenics also manifest cortical gray-matter deficits, but it is unclear whether these changes are isomorphic with those in patients, and the answer is critical to understanding the neurobiological conditions necessary for disease expression given a predisposing genotype. Here we report three-dimensional cortical surface maps (probabilistic atlases matching subjects' anatomy point by point throughout cortex) in monozygotic (MZ) and dizygotic (DZ) twins discordant for chronic schizophrenia along with demographically matched control twins. A map encoding the average differences between schizophrenia patients and their unaffected MZ co-twins revealed deficits primarily in dorsolateral prefrontal cortex, superior temporal gyrus, and superior parietal lobule. A map encoding variation associated with genetic proximity to a patient (MZ co-twins > DZ co-twins > control twins) isolated deficits primarily in polar and dorsolateral prefrontal cortex. In each case, the statistical significance was confirmed through analysis of 10,000 Monte Carlo permutations, and the remaining cortex was shown to be significantly less affected by contrast analysis. The disease-related deficits in gray matter were correlated with measures of symptom severity and cognitive dysfunction but not with duration of illness or antipsychotic drug treatment. Genetic and disease-specific influences thus affect gray matter in partially nonoverlapping areas of predominantly heteromodal association cortex, changes that may act synergistically in producing overt behavioral features of the disorder.