Investigation of the expression of genes affecting cytomatrix active zone function in the amygdala in schizophrenia: effects of antipsychotic drugs

Divergence in expression of a singing-related neuroplasticity gene in the brains of 2 Ficedula flycatchers and their hybrids

Species-specific sexual traits facilitate species-assortative mating by reducing mating across species and reducing hybrid sexual attractiveness. For learned sexual traits, such as song in oscine birds, species distinctiveness can be eroded when species co-occur. Transcriptional regulatory divergence in brain regions involved in sensory learning is hypothesized to maintain species distinctiveness, but relatively few studies have compared gene expression in relevant brain regions between closely related species. Species differences in song are an important premating reproductive barrier between the collared (Ficedula albicollis) and pied flycatcher (F. hypoleuca). Here, we compare brain gene expression in adult males from each species and their naturally occurring F1 hybrids. We report overall conserved expression across species in a portion of the brain containing regions and nuclei known to be involved in song responses and learning. Further, among those genes that were differentially expressed between species, we find largely intermediate expression in hybrids. A single gene, SYT4 (synaptotagmin 4), known to be singing-associated, both was differentially expressed and has a putative upstream transcriptional regulatory factor containing fixed differences between the 2 species. Although a finer-scale investigation limited to song-specific regions may reveal further species differences, our findings provide insight into regulatory divergence in the brain between closely related species.

Aberrant methylation in neurofunctional gene serves as a hallmark of tumorigenesis and progression in colorectal cancer

BACKGROUND

DNA methylation is one of the most promising biomarkers in predicting the prognosis of colorectal cancer (CRC). We aimed to develop a DNA methylation biomarker that could evaluate the prognosis of CRC.

METHODS

A promising DNA methylation biomarker was developed by hypermethylated genes in cancer tissue that were identified from Illumina EPIC methylation arrays. A cohort comprising 30 pairs of snap-frozen tumor tissue and adjacent normal tissue was used for correlation analysis between the methylation and expression status of the marker. The other cohort comprising 254 formalin-fixed paraffin-embedded (FFPE) tumor tissue from 254 CRC patients was used for prognosis analysis.

RESULTS

Regulating synaptic membrane exocytosis 2 (RIMS2) was hypermethylated and lowly expressed in CRC comparing to adjacent normal tissue. Hypermethylation of RIMS2 in CRC was correlated with less frequent KRAS mutant and high differentiation. RIMS2 promoter methylation showed independent predictive value for survival outcome (P = 0.015, HR 1.992, 95% CI [(1.140-3.48)]), and a combination of RIMS2 methylation with KRAS status could predict prognosis better.

CONCLUSIONS

RIMS2 is frequently hypermethylated in CRC, which can silence the expression of RIMS2. RIMS2 methylation is a novel biomarker for predicting the prognosis of CRC.

Pirenperone relieves the symptoms of fragile X syndrome in Fmr1 knockout mice

Fragile X syndrome (FXS) is a neurodevelopmental disorder that is caused by the loss of Fragile X-linked mental retardation protein (FMRP), an RNA binding protein that can bind and recognize different RNA structures and regulate the target mRNAs' translation involved in neuronal synaptic plasticity. Perturbations of this gene expression network have been related to abnormal behavioral symptoms such as hyperactivity, and impulsivity. Considering the roles of FMRP in the modulation of mRNA translation, we investigated the differentially expressed genes which might be targeted to revert to normal and ameliorate behavioral symptoms. Gene expression data was analyzed and used the connectivity map (CMap) to understand the changes in gene expression in FXS and predict the effective drug candidates. We analyzed the GSE7329 dataset that had 15 control and 8 FXS patients' lymphoblastoid samples. Among 924 genes, 42 genes were selected as signatures for CMap analysis, and 24 associated drugs were found. Pirenperone was selected as a potential drug candidate for FXS for its possible antipsychotic effect. Treatment of pirenperone increased the expression level of Fmr1 gene. Moreover, pirenperone rescued the behavioral deficits in Fmr1 KO mice including hyperactivity, spatial memory, and impulsivity. These results suggest that pirenperone is a new drug candidate for FXS, which should be verified in future studies.

Schizophrenia-Like Behavioral Impairments in Mice with Suppressed Expression of Piccolo in the Medial Prefrontal Cortex

Piccolo, a presynaptic cytomatrix protein, plays a role in synaptic vesicle trafficking in the presynaptic active zone. Certain single-nucleotide polymorphisms of the Piccolo-encoding gene PCLO are reported to be associated with mental disorders. However, a few studies have evaluated the relationship between Piccolo dysfunction and psychotic symptoms. Therefore, we investigated the neurophysiological and behavioral phenotypes in mice with Piccolo suppression in the medial prefrontal cortex (mPFC). Downregulation of Piccolo in the mPFC reduced regional synaptic proteins, accompanied with electrophysiological impairments. The Piccolo-suppressed mice showed an enhanced locomotor activity, impaired auditory prepulse inhibition, and cognitive dysfunction. These abnormal behaviors were partially ameliorated by the antipsychotic drug risperidone. Piccolo-suppressed mice received mild social defeat stress showed additional behavioral despair. Furthermore, the responses of these mice to extracellular glutamate and dopamine levels induced by the optical activation of mPFC projection in the dorsal striatum (dSTR) were inhibited. Similarly, the Piccolo-suppressed mice showed decreased depolarization-evoked glutamate and -aminobutyric acid elevations and increased depolarization-evoked dopamine elevation in the dSTR. These suggest that Piccolo regulates neurotransmission at the synaptic terminal of the projection site. Reduced neuronal connectivity in the mPFC-dSTR pathway via suppression of Piccolo in the mPFC may induce behavioral impairments observed in schizophrenia.

In silico screening using bulk and single-cell RNA-seq data identifies RIMS2 as a prognostic marker in basal-like breast cancer: A retrospective study

Single-cell RNA-seq has become a powerful tool to understand tumor cell heterogenicity. This study tried to screen prognosis-related genes in basal-like breast tumors and evaluate their correlations with cellular states at the single-cell level.Bulk RNA-seq data of basal-like tumor cases from The Cancer Genome Atlas-Breast Cancer (TCGA-BRCA) and single-cell RNA-seq from GSE75688 were retrospectively reviewed. Kaplan-Meier survival curves, univariate and multivariate analysis based on Cox regression model were conducted for survival analysis. Gene set enrichment analysis (GSEA) and single-cell cellular functional state analysis were performed.Twenty thousand five hundred thirty genes with bulk RNA-seq data in TCGA were subjected to screening. Preliminary screening identified 10 candidate progression-related genes, including CDH19, AQP5, SDR16C5, NCAN, TTYH1, XAGE2, RIMS2, GZMB, LY6D, and FAM3B. By checking their profiles using single-cell RNA-seq data, only CDH19, SDR16C5, TTYH1, and RIMS2 had expression in primary triple-negative breast cancer (TNBC) cells. Prognostic analysis only confirmed that RIMS2 expression was an independent prognostic indicator of favorable progression free survival (PFS) (HR: 0.78, 95%: 0.64-0.95, P  = .015). GSEA analysis showed that low RIMS2 group expression had genes significantly enriched in DNA Repair, and MYC Targets V2. Among the 89 basal-like cells, RIMS2 expression was negatively correlated with DNA repair and epithelial-to-mesenchymal transition (EMT).RIMS2 expression was negatively associated with DNA repair capability of basal-like breast tumor cells and might serve as an independent indicator of favorable PFS.

Identification of Novel Targets of RBM5 in the Healthy and Injured Brain

The tumor suppressor RNA-binding motif 5 (RBM5) regulates the expression levels and cassette exon-definition (i.e. splicing) of a select set of mRNAs in a tissue-specific manner. Most RBM5-regulated targets were identified in oncological investigations and frequently involve genes which mediate apoptotic cell death. Little is known about the role of RBM5 in the brain. Also, it is unclear if a brain injury may be required to detect RBM5 mediated effects on pro-apoptotic genes due to their low expression levels in the healthy adult CNS at baseline. Conditional/floxed (brain-specific) gene deleter mice were generated to elucidate CNS-specific RBM5 mRNA targets. Male/female mice were subjected to a severe controlled cortical impact (CCI) traumatic brain injury (TBI) in order to increase the background expression of pro-death mRNAs and facilitate testing of the hypothesis that RBM5 inhibition decreases post-injury upregulation of caspases/FAS in the CNS. As expected, a CCI increased caspases/FAS mRNA in the injured cortex. RBM5 KO did not affect their levels or splicing. Surprisingly, KO increased the mRNA levels of novel targets including casein kinase 2 alpha prime interacting protein (Csnka2ip/CKT2) - a gene not thought to be expressed in the brain, contrary to findings here. Twenty-two unique splicing events were also detected in KOs including increased block-inclusion of cassette exons 20-22 in regulating synaptic membrane exocytosis 2 (Rims2). In conclusion, here we used genome-wide transcriptomic analysis on healthy and injured RBM5 KO mouse brain tissue to elucidate the first known gene targets of this enigmatic RBP in this CNS.

Molecular alterations in the medial temporal lobe in schizophrenia

The medial temporal lobe (MTL) and its individual structures have been extensively implicated in schizophrenia pathophysiology, with considerable efforts aimed at identifying structural and functional differences in this brain region. The major structures of the MTL for which prominent differences have been revealed include the hippocampus, the amygdala and the superior temporal gyrus (STG). The different functions of each of these regions have been comprehensively characterized, and likely contribute differently to schizophrenia. While neuroimaging studies provide an essential framework for understanding the role of these MTL structures in various aspects of the disease, ongoing efforts have sought to employ molecular measurements in order to elucidate the biology underlying these macroscopic differences. This review provides a summary of the molecular findings in three major MTL structures, and discusses convergent findings in cellular architecture and inter-and intra-cellular networks. The findings of this effort have uncovered cell-type, network and gene-level specificity largely unique to each brain region, indicating distinct molecular origins of disease etiology. Future studies should test the functional implications of these molecular changes at the circuit level, and leverage new advances in sequencing technology to further refine our understanding of the differential contribution of MTL structures to schizophrenia.

New insights into tardive dyskinesia genetics: Implementation of whole-exome sequencing approach

Tardive dyskinesia (TD) is an adverse movement disorder induced by chronic treatment with antipsychotics drugs. The contribution of common genetic variants to TD susceptibility has been investigated in recent years, but with limited success. The aim of the current study was to investigate the potential contribution of rare variants to TD vulnerability. In order to identify TD risk genes, we performed whole-exome sequencing (WES) and gene-based collapsing analysis focusing on rare (allele frequency < 1%) and putatively deleterious variants (qualifying variants). 82 Jewish schizophrenia patients chronically treated with antipsychotics were included and classified as having severe TD or lack of any abnormal movements based on a rigorous definition of the TD phenotype. First, we performed a case-control, exome-wide collapsing analysis comparing 39 schizophrenia patients with severe TD to 3118 unrelated population controls. Then, we checked the potential top candidate genes among 43 patients without any TD manifestations. All the genes that were found to harbor one or more qualifying variants in patients without any TD features were excluded from the final list of candidate genes. Only one gene, regulating synaptic membrane exocytosis 2 (RIMS2), showed significant enrichment of qualifying variants in TD patients compared with unrelated population controls after correcting for multiple testing (Fisher's exact test p = 5.32E-08, logistic regression p = 2.50E-08). Enrichment was caused by a single variant (rs567070433) due to a frameshift in an alternative transcript of RIMS2. None of the TD negative patients had qualifying variants in this gene. In a validation cohort of 140 schizophrenia patients assessed for TD, the variant was also not detected in any individual. Some potentially suggestive TD genes were detected in the TD cohort and warrant follow-up in future studies. No significant enrichment in previously reported TD candidate genes was identified. To the best of our knowledge, this is the first WES study of TD, demonstrating the potential role of rare loss-of-function variant enrichment in this pharmacogenetic phenotype.

Genetic predisposition to high anxiety- and depression-like behavior coincides with diminished DNA methylation in the adult rat amygdala

Understanding biological mechanisms that shape vulnerability to emotional dysfunction is critical for elucidating the neurobiology of psychiatric illnesses like anxiety and depression. To elucidate molecular and epigenetic alterations in the brain that contribute to individual differences in emotionality, our laboratory utilized a rodent model of temperamental differences. Rats bred for low response to novelty (Low Responders, LRs) are inhibited in novel situations and display high anxiety, helplessness, and diminished sociability compared to High Novelty Responder (HR) rats. Our current transcriptome profiling experiment identified widespread gene expression differences in the amygdala of adult HR/LR rats; we hypothesize that HR/LR gene expression and downstream behavioral differences stem from distinct epigenetic (specifically DNA methylation) patterning in the HR/LR brain. Although we found similar levels of DNA methyltransferase proteins in the adult HR/LR amygdala, next-generation sequencing analysis of the methylome revealed 793 differentially methylated genomic sites between the groups. Most of the differentially methylated sites were hypermethylated in HR versus LR, so we next tested the hypothesis that enhancing DNA methylation in LRs would improve their anxiety/depression-like phenotype. We found that increasing DNA methylation in LRs (via increased dietary methyl donor content) improved their anxiety-like behavior and decreased their typically high levels of Forced Swim Test (FST) immobility; however, dietary methyl donor depletion exacerbated LRs' high FST immobility. These data are generally consistent with findings in depressed patients showing that treatment with DNA methylation-promoting agents improves depressive symptoms, and highlight epigenetic mechanisms that may contribute to individual differences in risk for emotional dysfunction.

Rab3 interacting molecule 3 mutations associated with autism alter regulation of voltage-dependent Ca²⁺ channels

Autism is a neurodevelopmental psychiatric disorder characterized by impaired reciprocal social interaction, disrupted communication, and restricted and stereotyped patterns of interests. Autism is known to have a strong genetic component. Although mutations in several genes account for only a small proportion of individuals with autism, they provide insight into potential biological mechanisms that underlie autism, such as dysfunction in Ca(2+) signaling, synaptic dysfunction, and abnormal brain connectivity. In autism patients, two mutations have been reported in the Rab3 interacting molecule 3 (RIM3) gene. We have previously demonstrated that RIM3 physically and functionally interacts with voltage-dependent Ca(2+) channels (VDCCs) expressed in neurons via the β subunits, and increases neurotransmitter release. Here, by introducing corresponding autism-associated mutations that replace glutamic acid residue 176 with alanine (E176A) and methionine residue 259 with valine (M259V) into the C2B domain of mouse RIM3, we demonstrate that both mutations partly cancel the suppressive RIM3 effect on voltage-dependent inactivation of Ba(2+) currents through P/Q-type CaV2.1 recombinantly expressed in HEK293 cells. In recombinant N-type CaV2.2 VDCCs, the attenuation of the suppressive RIM3 effect on voltage-dependent inactivation is conserved for M259V but not E176A. Slowing of activation speed of P/Q-type CaV2.1 currents by RIM3 is abolished in E176A, while the physical interaction between RIM3 and β subunits is significantly attenuated in M259V. Moreover, increases by RIM3 in depolarization-induced Ca(2+) influx and acetylcholine release are significantly attenuated by E176A in rat pheochromocytoma PC12 cells. Thus, our data raise the interesting possibility that autism phenotypes are elicited by synaptic dysfunction via altered regulation of presynaptic VDCC function and neurotransmitter release.

Deletion of Rapgef6, a candidate schizophrenia susceptibility gene, disrupts amygdala function in mice

In human genetic studies of schizophrenia, we uncovered copy-number variants in RAPGEF6 and RAPGEF2 genes. To discern the effects of RAPGEF6 deletion in humans, we investigated the behavior and neural functions of a mouse lacking Rapgef6. Rapgef6 deletion resulted in impaired amygdala function measured as reduced fear conditioning and anxiolysis. Hippocampal-dependent spatial memory and prefrontal cortex-dependent working memory tasks were intact. Neural activation measured by cFOS phosphorylation demonstrated a reduction in hippocampal and amygdala activation after fear conditioning, while neural morphology assessment uncovered reduced spine density and primary dendrite number in pyramidal neurons of the CA3 hippocampal region of knockout mice. Electrophysiological analysis showed enhanced long-term potentiation at cortico-amygdala synapses. Rapgef6 deletion mice were most impaired in hippocampal and amygdalar function, brain regions implicated in schizophrenia pathophysiology. The results provide a deeper understanding of the role of the amygdala in schizophrenia and suggest that RAPGEF6 may be a novel therapeutic target in schizophrenia.

First effects of rising amyloid-β in transgenic mouse brain: synaptic transmission and gene expression

Understanding the earliest changes in Alzheimer’s disease may help in the prevention of cognitive impairment. In a transgenic mouse model, Cummings et al. show that synaptic changes occur shortly after soluble amyloid-β levels become measurable, and before the rapid increases in total Aβ and Aβ₄₂:Aβ₄₀ that lead to detectable plaque deposition.

Detecting and treating Alzheimer’s disease, before cognitive deficits occur, has become the health challenge of our time. The earliest known event in Alzheimer’s disease is rising amyloid-β. Previous studies have suggested that effects on synaptic transmission may precede plaque deposition. Here we report how relative levels of different soluble amyloid-β peptides in hippocampus, preceding plaque deposition, relate to synaptic and genomic changes. Immunoprecipitation-mass spectrometry was used to measure the early rise of different amyloid-β peptides in a mouse model of increasing amyloid-β (‘TASTPM’, transgenic for familial Alzheimer’s disease genes APP/PSEN1). In the third postnatal week, several amyloid-β peptides were above the limit of detection, including amyloid-β₄₀, amyloid-β₃₈ and amyloid-β₄₂ with an intensity ratio of 6:3:2, respectively. By 2 months amyloid-β levels had only increased by 50% and although the ratio of the different peptides remained constant, the first changes in synaptic currents, compared to wild-type mice could be detected with patch-clamp recordings. Between 2 and 4 months old, levels of amyloid-β₄₀ rose by ∼7-fold, but amyloid-β₄₂ rose by 25-fold, increasing the amyloid-β₄₂:amyloid-β₄₀ ratio to 1:1. Only at 4 months did plaque deposition become detectable and only in some mice; however, synaptic changes were evident in all hippocampal fields. These changes included increased glutamate release probability (P < 0.001, n = 7–9; consistent with the proposed physiological effect of amyloid-β) and loss of spontaneous action potential-mediated activity in the cornu ammonis 1 (CA1) and dentate gyrus regions of the hippocampus (P < 0.001, n = 7). Hence synaptic changes occur when the amyloid-β levels and amyloid-β₄₂:amyloid-β₄₀ ratio are still low compared to those necessary for plaque deposition. Genome-wide microarray analysis revealed changes in gene expression at 2–4 months including synaptic genes being strongly affected but often showing significant changes only by 4 months. We thus demonstrate that, in a mouse model of rising amyloid-β, the initial deposition of plaques does not occur until several months after the first amyloid-β becomes detectable but coincides with a rapid acceleration in the rise of amyloid-β levels and the amyloid-β₄₂:amyloid-β₄₀ ratio. Prior to acceleration, however, there is already a pronounced synaptic dysfunction, reflected as changes in synaptic transmission and altered gene expression, indicating that restoring synaptic function early in the disease progression may represent the earliest possible target for intervention in the onset of Alzheimer’s disease.

Antipsychotic drug-associated gene-miRNA interaction in T-lymphocytes

Antipsychotic drugs (APDs) can have a profound effect on the human body that extends well beyond our understanding of their neuropsychopharmacology. Some of these effects manifest themselves in peripheral blood lymphocytes, and in some cases, particularly in clozapine treatment, result in serious complications. To better understand the molecular biology of APD action in lymphocytes, we investigated the influence of chlorpromazine, haloperidol and clozapine in vitro, by microarray-based gene and microRNA (miRNA) expression analysis. JM-Jurkat T-lymphocytes were cultured in the presence of the APDs or vehicle alone over 2 wk to model the early effects of APDs on expression. Interestingly both haloperidol and clozapine appear to regulate the expression of a large number of genes. Functional analysis of APD-associated differential expression revealed changes in genes related to oxidative stress, metabolic disease and surprisingly also implicated pathways and biological processes associated with neurological disease consistent with current understanding of the activity of APDs. We also identified miRNA-mRNA interaction associated with metabolic pathways and cell death/survival, all which could have relevance to known side effects of APDs. These results indicate that APDs have a significant effect on expression in peripheral tissue that relate to both known mechanisms as well as poorly characterized side effects.

Association between regulating synaptic membrane exocytosis 2 gene polymorphisms and degenerative lumbar scoliosis

Degenerative lumbar scoliosis (DLS) is a spinal deformity that develops after skeletal maturity and progresses with age. In contrast to adolescent idiopathic scoliosis, the genetic association of DLS has not yet been elucidated. The purpose of this study was to investigate the association between regulating synaptic membrane exocytosis 2 (RIMS2, OBOE) gene polymorphisms and DLS. Two coding single-nucleotide polymorphisms [rs2028945 (Gln1200Gln) and rs10461 (Ala1327Ala)] of RIMS2 were selected and genotyped by direct sequencing. As a result, the rs10461 was associated with DLS in allele frequencies (P=0.008) and genotype distributions (P=0.006 in the codominant model, 0.018 in the dominant model and 0.029 in the recessive model). In the analysis of haplotypes, two haplotypes exhibited significant differences between the control and DLS groups (CC haplotype, P=0.009 in the codominant model, 0.038 in the dominant model and 0.030 in the recessive model; CT haplotype, P=0.041 in the codominant model and 0.021 in the dominant model). These findings suggest that RIMS2 may be associated with the development of DLS.

RIM3γ and RIM4γ are key regulators of neuronal arborization

The large isoforms of the Rab3 interacting molecule (RIM) family, RIM1α/β and RIM2α/β, have been shown to be centrally involved in mediating presynaptic active zone function. The RIM protein family contains two additional small isoforms, RIM3γ and RIM4γ, which are composed only of the RIM-specific C-terminal C2B domain and varying N-terminal sequences and whose function remains to be elucidated. Here, we report that both, RIM3γ and RIM4γ, play an essential role for the development of neuronal arborization and of dendritic spines independent of synaptic function. γ-RIM knock-down in rat primary neuronal cultures and in vivo resulted in a drastic reduction in the complexity of neuronal arborization, affecting both axonal and dendritic outgrowth, independent of the time point of γ-RIM downregulation during dendrite development. Rescue experiments revealed that the phenotype is caused by a function common to both γ-RIMs. These findings indicate that γ-RIMs are involved in cell biological functions distinct from the regulation of synaptic vesicle exocytosis and play a role in the molecular mechanisms controlling the establishment of dendritic complexity and axonal outgrowth.

Finding the needle in the haystack: a review of microarray gene expression research into schizophrenia

BACKGROUND

With an estimated 80% heritability, molecular genetic research into schizophrenia has remained inconclusive. Recent large-scale, genome-wide association studies only identified a small number of susceptibility genes with individually very small effect sizes. However, the variable expression of the phenotype is not well captured in diagnosis-based research as well as when assuming a 'heterogenic risk model' (as apposed to a monogenic or polygenic model). Hence, the expression of susceptibility genes in response to environmental factors in concert with other disease-promoting or protecting genes has increasingly attracted attention.

METHOD

The current review summarises findings of microarray gene expression research with relevance to schizophrenia as they emerged over the past decade.

RESULTS

Most findings from post mortem, peripheral tissues and animal models to date have linked altered gene expression in schizophrenia to presynaptic function, signalling, myelination, neural migration, cellular immune mechanisms, and response to oxidative stress consistent with multiple small effects of many individual genes. However, the majority of results are difficult to interpret due to small sample sizes (i.e. potential type-2 errors), confounding factors (i.e. medication effects) or lack of plausible neurobiological theory.

CONCLUSION

Nevertheless, microarray gene expression research is likely to play an important role in the future when investigating gene/gene and gene/environment interactions by adopting a neurobiologically sound theoretical framework.

D-amino acid oxidase activity is inhibited by an interaction with bassoon protein at the presynaptic active zone

Schizophrenia is a highly heritable neuropsychiatric disorder affecting ∼1% of the world's population. Linkage and association studies have identified multiple candidate schizophrenia susceptibility genes whose functions converge on the glutamatergic neurotransmitter system. One such susceptibility gene encoding D-amino acid oxidase (DAO), an enzyme that metabolizes the NMDA receptor (NMDAR) co-agonist D-serine, has the potential to modulate NMDAR function in the context of schizophrenia. To further investigate its cellular regulation, we sought to identify DAO-interacting proteins that participate in its functional regulation in rat cerebellum, where DAO expression is especially high. Immunoprecipitation with DAO-specific antibodies and subsequent mass spectrometric analysis of co-precipitated proteins yielded 24 putative DAO-interacting proteins. The most robust interactions occurred with known components of the presynaptic active zone, such as bassoon (BSN) and piccolo (PCLO). The interaction of DAO with BSN was confirmed through co-immunoprecipitation assays using DAO- and BSN-specific antibodies. Moreover, DAO and BSN colocalized with one another in cultured cerebellar granule cells and in synaptic junction membrane protein fractions derived from rat cerebellum. The functional consequences of this interaction were studied through enzyme assay experiments, where DAO enzymatic activity was significantly inhibited as a result of its interaction with BSN. Taking these results together, we hypothesize that synaptic D-serine concentrations may be under tight regulation by a BSN-DAO complex. We therefore predict that this mechanism plays a role in the modulation of glutamatergic signaling through NMDARs. It also furthers our understanding of the biology underlying this potential therapeutic entry point for schizophrenia and other psychiatric disorders.

The molecular genetics of autism spectrum disorders: genomic mechanisms, neuroimmunopathology, and clinical implications

Autism spectrum disorders (ASDs) have become increasingly common in recent years. The discovery of single-nucleotide polymorphisms and accompanying copy number variations within the genome has increased our understanding of the architecture of the disease. These genetic and genomic alterations coupled with epigenetic phenomena have pointed to a neuroimmunopathological mechanism for ASD. Model animal studies, developmental biology, and affective neuroscience laid a foundation for dissecting the neural pathways impacted by these disease-generating mechanisms. The goal of current autism research is directed toward a systems biological approach to find the most basic genetic and environmental causes to this severe developmental disease. It is hoped that future genomic and neuroimmunological research will be directed toward finding the road toward prevention, treatment, and cure of ASD.

A de novo 1p34.2 microdeletion identifies the synaptic vesicle gene RIMS3 as a novel candidate for autism

Background

A child with autism and mild microcephaly was found to have a de novo 3.3 Mb microdeletion on chromosome 1p34.2p34.3. The hypothesis is tested that this microdeletion contains one or more genes that underlie the autism phenotype in this child and in other children with autism spectrum disorders.

Methods

To search for submicroscopic chromosomal rearrangements in the child, array comparative genomic hybridisation (aCGH) was performed using a 19 K whole genome human bacterial artificial chromosome (BAC) array and the Illumina 610-Quad BeadChip microarray. Ingenuity pathway analysis (IPA) was used to construct functional biological networks to identify candidate autism genes. To identify putative functional variants in candidate genes, mutation screening was performed using polymerase chain reaction (PCR) based Sanger sequencing in 512 unrelated autism patients and 462 control subjects.

Results

A de novo 3.3 Mb deletion containing ∼43 genes in chromosome 1p34.2p34.3 was identified and subsequently confirmed using fluorescence in situ hybridization (FISH). Literature review and bioinformatics analyses identified Regulating Synaptic Membrane Exocytosis 3 (RIMS3) as the most promising autism candidate gene. Mutation screening of this gene in autism patients identified five inherited coding variants, including one (p.E177A) that segregated with the autism phenotype in a sibship, was predicted to be deleterious, and was absent in 1161 controls.

Conclusions

This case report and mutation screening data suggest that RIMS3 is an autism causative or contributory gene. Functional studies of RIMS3 variants such as p.E177A should provide additional insight into the role of synaptic proteins in the pathophysiology of autism.