An integrated genomic analysis of gene-function correlation on schizophrenia susceptibility genes

Genome-wide association studies (GWAS) and post-GWAS analyses of impulsivity: A systematic review

Impulsivity is related to a host of mental and behavioral problems. It is a complex construct with many different manifestations, most of which are heritable. The genetic compositions of these impulsivity manifestations, however, remain unclear. A number of genome-wide association studies (GWAS) and post-GWAS analyses have tried to address this issue. We conducted a systematic review of all GWAS and post-GWAS analyses of impulsivity published up to December 2023. Available data suggest that single nucleotide polymorphisms (SNPs) in more than a dozen of genes (e.g., CADM2, CTNNA2, GPM6B) are associated with different measures of impulsivity at genome-wide significant levels. Post-GWAS analyses further show that different measures of impulsivity are subject to different degrees of genetic influence, share few genetic variants, and have divergent genetic overlap with basic personality traits such as extroversion and neuroticism, cognitive ability, psychiatric disorders, substance use, and obesity. These findings shed light on controversies in the conceptualization and measurement of impulsivity, while providing new insights on the underlying mechanisms that yoke impulsivity to psychopathology.

Paternal aging impacts expression and epigenetic markers as early as the first embryonic tissue lineage differentiation

BACKGROUND

Advanced paternal age (APA) is associated with adverse outcomes to offspring health, including increased risk for neurodevelopmental disorders. The aim of this study was to investigate the methylome and transcriptome of the first two early embryonic tissue lineages, the inner cell mass (ICM) and the trophectoderm (TE), from human blastocysts in association with paternal age and disease risk. High quality human blastocysts were donated with patient consent from donor oocyte IVF cycles from either APA (≥ 50 years) or young fathers. Blastocysts were mechanically separated into ICM and TE lineage samples for both methylome and transcriptome analyses.

RESULTS

Significant differential methylation and transcription was observed concurrently in ICM and TE lineages of APA-derived blastocysts compared to those from young fathers. The methylome revealed significant enrichment for neuronal signaling pathways, as well as an association with neurodevelopmental disorders and imprinted genes, largely overlapping within both the ICM and TE lineages. Significant enrichment of neurodevelopmental signaling pathways was also observed for differentially expressed genes, but only in the ICM. In stark contrast, no significant signaling pathways or gene ontology terms were identified in the trophectoderm. Despite normal semen parameters in aged fathers, these significant molecular alterations can adversely contribute to downstream impacts on offspring health, in particular neurodevelopmental disorders like autism spectrum disorder and schizophrenia.

CONCLUSIONS

An increased risk for neurodevelopmental disorders is well described in children conceived by aged fathers. Using blastocysts derived from donor oocyte IVF cycles to strategically control for maternal age, our data reveals evidence of methylation dysregulation in both tissue lineages, as well as transcription dysregulation in neurodevelopmental signaling pathways associated with APA fathers. This data also reveals that embryos derived from APA fathers do not appear to be compromised for initial implantation potential with no significant pathway signaling disruption in trophectoderm transcription. Collectively, our work provides insights into the complex molecular mechanisms that occur upon paternal aging during the first lineage differentiation in the preimplantation embryo. Early expression and epigenetic markers of APA-derived preimplantation embryos highlight the susceptibility of the future fetus to adverse health outcomes.

Genomic analysis of firework fear and noise reactivity in standard poodles

BACKGROUND

Fear of firework noises and other loud, sudden noises (noise reactivity) is a significant problem for many dogs and may have a negative effect on both welfare and, in severe cases, the life expectancy of dogs. A wide range of behavior traits, including fear-related behaviors, have high heritability estimates in dogs. The aim of this study was to estimate genomic heritability for fear of fireworks and loud noises in dogs.

RESULTS

A genomic heritability estimate was performed based on genome-wide SNPs from standard poodles with records of fear of fireworks and noise reactivity. The study was based on questionnaires answered by owners, who also volunteered to return a cheek swab from their dog for DNA analyses. SNP-based heritability was estimated to be 0.28 for firework fear and 0.16 for noise reactivity. We also identified an interesting region on chromosome 17 that was weakly associated with both traits.

CONCLUSIONS

We have estimated low to medium genomic heritabilities for fear of fireworks and noise reactivity in standard poodles. We have also identified an interesting region on chromosome 17, which harbors genes that have been shown to be involved in different psychiatric traits with anxiety components in humans. The region was associated with both traits; however, the association was weak and need further verification from other studies.

Disruption of Astrocyte-Dependent Dopamine Control in the Developing Medial Prefrontal Cortex Leads to Excessive Grooming in Mice

BACKGROUND

Astrocytes control synaptic activity by modulating perisynaptic concentrations of ions and neurotransmitters including dopamine (DA) and, as such, could be involved in the modulating aspects of mammalian behavior.

METHODS

We produced a conditional deletion of the vesicular monoamine transporter 2 (VMAT2) specifically in astrocytes (aVMTA2cKO mice) and studied the effects of the lack of VMAT2 in prefrontal cortex (PFC) astrocytes on the regulation of DA levels, PFC circuit functions, and behavioral processes.

RESULTS

We found a significant reduction of medial PFC (mPFC) DA levels and excessive grooming and compulsive repetitive behaviors in aVMAT2cKO mice. The mice also developed a synaptic pathology, expressed through increased relative AMPA versus NMDA receptor currents in synapses of the dorsal striatum receiving inputs from the mPFC. Importantly, behavioral and synaptic phenotypes were rescued by re-expression of mPFC VMAT2 and L-DOPA treatment, showing that the deficits were driven by mPFC astrocytes that are critically involved in developmental DA homeostasis. By analyzing human tissue samples, we found that VMAT2 is expressed in human PFC astrocytes, corroborating the potential translational relevance of our observations in mice.

CONCLUSIONS

Our study shows that impairment of the astrocytic control of DA in the mPFC leads to symptoms resembling obsessive-compulsive spectrum disorders such as trichotillomania and has a profound impact on circuit function and behaviors.

Emerging evidence for astrocyte dysfunction in schizophrenia

Schizophrenia is a complex, chronic mental health disorder whose heterogeneous genetic and neurobiological background influences early brain development, and whose precise etiology is still poorly understood. Schizophrenia is not characterized by gross brain pathology, but involves subtle pathological changes in neuronal populations and glial cells. Among the latter, astrocytes critically contribute to the regulation of early neurodevelopmental processes, and any dysfunctions in their morphological and functional maturation may lead to aberrant neurodevelopmental processes involved in the pathogenesis of schizophrenia, such as mitochondrial biogenesis, synaptogenesis, and glutamatergic and dopaminergic transmission. Studies of the mechanisms regulating astrocyte maturation may therefore improve our understanding of the cellular and molecular mechanisms underlying the pathogenesis of schizophrenia.

Detecting Genetic Ancestry and Adaptation in the Taiwanese Han People

The Taiwanese people are composed of diverse indigenous populations and the Taiwanese Han. About 95% of the Taiwanese identify themselves as Taiwanese Han, but this may not be a homogeneous population because they migrated to the island from various regions of continental East Asia over a period of 400 years. Little is known about the underlying patterns of genetic ancestry, population admixture, and evolutionary adaptation in the Taiwanese Han people. Here, we analyzed the whole-genome single-nucleotide polymorphism genotyping data from 14,401 individuals of Taiwanese Han collected by the Taiwan Biobank and the whole-genome sequencing data for a subset of 772 people. We detected four major genetic ancestries with distinct geographic distributions (i.e., Northern, Southeastern, Japonic, and Island Southeast Asian ancestries) and signatures of population mixture contributing to the genomes of Taiwanese Han. We further scanned for signatures of positive natural selection that caused unusually long-range haplotypes and elevations of hitchhiked variants. As a result, we identified 16 candidate loci in which selection signals can be unambiguously localized at five single genes: CTNNA2, LRP1B, CSNK1G3, ASTN2, and NEO1. Statistical associations were examined in 16 metabolic-related traits to further elucidate the functional effects of each candidate gene. All five genes appear to have pleiotropic connections to various types of disease susceptibility and significant associations with at least one metabolic-related trait. Together, our results provide critical insights for understanding the evolutionary history and adaption of the Taiwanese Han population.

Catenin Alpha 2 May Be a Biomarker or Potential Drug Target in Psychiatric Disorders with Perseverative Negative Thinking

AlphaN-catenin gene CTNNA2 has been implicated in intrauterine brain development, as well as in several psychiatric disorders and cardiovascular diseases. Our present aim was to investigate CTNNA2 gene-wide associations of single-nucleotide polymorphisms (SNPs) with psychiatric and cardiovascular risk factors to test the potential mediating role of rumination, a perseverative negative thinking phenotype in these associations. Linear mixed regression models were run by FaST-LMM within a sample of 795 individuals from the Budakalasz Health Examination Survey. The psychiatric outcome variables were rumination and its subtypes, and ten Brief Symptom Inventory (BSI) scores including, e.g., obsessive-compulsive, depression, anxiety, hostility, phobic anxiety, and paranoid ideation. Cardiovascular outcome variables were BMI and the Framingham risk scores for cardiovascular disease, coronary heart disease, myocardial infarction, and stroke. We found nominally significant CTNNA2 associations for every phenotype. Rumination totally mediated the associations of CTNNA2 rs17019243 with eight out of ten BSI scores, but none with Framingham scores or BMI. Our results suggest that CTNNA2 genetics may serve as biomarkers, and increasing the expression or function of CTNNA2 protein may be a potential new therapeutic approach in psychiatric disorders with perseverative negative thinking including, e.g., depression. Generally, an antiruminative agent could be a transdiagnostic and preventive psychopharmacon.

Neuropeptide Y gene variants in obesity, dietary intake, blood pressure, lipid and glucose metabolism: A longitudinal birth cohort study

OBJECTIVE

Neuropeptide Y affects several physiological functions, notably appetite regulation. We analysed the association between four single nucleotide polymorphisms (SNP) in the NPY gene (rs5574, rs16147, rs16139, rs17149106) and measures of obesity, dietary intake, physical activity, blood pressure, glucose and lipid metabolism from adolescence to young adulthood.

METHODS

The sample included both birth cohorts of the Estonian Children Personality Behaviour and Health Study at ages 15 (n = 1075 with available complete data), 18 (n = 913) and 25 (n = 926) years. Linear mixed-effects regression models were used for longitudinal association between NPY SNP-s and variables of interest. Associations at ages 15, 18 and 25 were analysed by ANOVA.

RESULTS

Rs5574 CC-homozygotes had a greater increase per year in waist-to-hip ratio (WHR) and a smaller decrease in daily energy intake and carbohydrate intake from age 15-25 years; fasting glucose and cholesterol were higher in rs5574 CC-homozygotes. Rs16147 TT-homozygotes had higher body weight and a greater increase in sum of 5 skinfolds, waist circumference, WHR and waist-to-height ratio; however, they had lower carbohydrate intake throughout the observation period. Rs16147 TT-homozygotes and both rs16139 and rs17149106 heterozygotes had higher triglyceride levels. All NPY SNP-s were associated with blood pressure: rs5574 TT-and rs16147 CC-homozygotes had a smaller increase in diastolic blood pressure, while rs16139 and rs17149106 heterozygous had lower blood pressure throughout the study.

CONCLUSION

Variants of the NPY gene were associated with measures of obesity, dietary intake, glucose and lipid metabolism and blood pressure from adolescence to young adulthood.

Molecular Mechanisms of L1 and NCAM Adhesion Molecules in Synaptic Pruning, Plasticity, and Stabilization

Mammalian brain circuits are wired by dynamic formation and remodeling during development to produce a balance of excitatory and inhibitory synapses. Synaptic regulation is mediated by a complex network of proteins including immunoglobulin (Ig)- class cell adhesion molecules (CAMs), structural and signal-transducing components at the pre- and post-synaptic membranes, and the extracellular protein matrix. This review explores the current understanding of developmental synapse regulation mediated by L1 and NCAM family CAMs. Excitatory and inhibitory synapses undergo formation and remodeling through neuronal CAMs and receptor-ligand interactions. These responses result in pruning inactive dendritic spines and perisomatic contacts, or synaptic strengthening during critical periods of plasticity. Ankyrins engage neural adhesion molecules of the L1 family (L1-CAMs) to promote synaptic stability. Chondroitin sulfates, hyaluronic acid, tenascin-R, and linker proteins comprising the perineuronal net interact with L1-CAMs and NCAM, stabilizing synaptic contacts and limiting plasticity as critical periods close. Understanding neuronal adhesion signaling and synaptic targeting provides insight into normal development as well as synaptic connectivity disorders including autism, schizophrenia, and intellectual disability.

Overexpression of complement component C4 in the dorsolateral prefrontal cortex, parietal cortex, superior temporal gyrus and associative striatum of patients with schizophrenia

BACKGROUND

In schizophrenia, abnormal synaptic pruning during adolescence may be due to altered expression of the Complement component 4 (C4). Overexpression of C4 genes has been identified in the total cerebral cortex and in 6 different brain regions of schizophrenic patients compared to controls. These alterations should be replicated and extended to other brain regions relevant to schizophrenia. Moreover, it remains unknown whether cerebral and peripheral C4 expression levels are related.

METHODS

We explored C4 genes expression both at the cerebral and peripheral levels. Using shinyGEO application we analyzed C4 expression from eight Gene Expression Omnibus datasets obtained from 196 schizophrenic patients and 182 control subjects. First, we compared C4 expression between schizophrenic patients and controls in postmortem cerebral samples from 7 different brain regions. Then, we compared C4 expression between schizophrenic patients and controls in 4 peripheral tissues.

RESULTS

At the cerebral level, we provide further evidence of C4 overexpression in schizophrenic patients. Consistently with a previous report, we found C4 overexpression in the dorsolateral prefrontal cortex and in the parietal cortex of schizophrenic patients. The observation of C4 overexpression was further extended to the superior temporal cortex and the associative striatum of schizophrenic patients. Conversely, no significant alteration of C4 expression was observed in peripheral tissues.

CONCLUSIONS

Our results support the hypothesis of an excessive Complement activity in various brain regions of schizophrenic patients which may disrupt the synaptic pruning process occurring during adolescence. C4 overexpression may be specific to the cerebral tissue while other alterations of the Complement system may be detected at the systemic level.

Genome integrity and neurogenesis of postnatal hippocampal neural stem/progenitor cells require a unique regulator Filia

Endogenous DNA double-strand breaks (DSBs) formation and repair in neural stem/progenitor cells (NSPCs) play fundamental roles in neurogenesis and neurodevelopmental disorders. NSPCs exhibit heterogeneity in terms of lineage fates and neurogenesis activity. Whether NSPCs also have heterogeneous regulations on DSB formation and repair to accommodate region-specific neurogenesis has not been explored. Here, we identified a regional regulator Filia, which is predominantly expressed in mouse hippocampal NSPCs after birth and regulates DNA DSB formation and repair. On one hand, Filia protects stalling replication forks and prevents the replication stress-associated DNA DSB formation. On the other hand, Filia facilitates the homologous recombination-mediated DNA DSB repair. Consequently, Filia^-/- mice had impaired hippocampal NSPC proliferation and neurogenesis and were deficient in learning, memory, and mood regulations. Thus, our study provided the first proof of concept demonstrating the region-specific regulations of DSB formation and repair in subtypes of NSPCs.

Cell adhesion molecule close homolog of L1 binds to the dopamine receptor D2 and inhibits the internalization of its short isoform

Cell adhesion molecule close homolog of L1 (CHL1) and the dopamine receptor D2 (DRD2) are associated with psychiatric and mental disorders. We here show that DRD2 interacts with CHL1 in mouse brain, as evidenced by co-immunostaining, proximity ligation assay, co-immunoprecipitation, and pull-down assay with recombinant extracellular CHL1 domain fused to Fc (CHL1-Fc). Direct binding of CHL1-Fc to the first extracellular loop of DRD2 was shown by ELISA. Using HEK cells transfected to co-express CHL1 and the short (DRD2-S) or long (DRD2-L) DRD2 isoforms, co-localization of CHL1 and both isoforms was observed by immunostaining and proximity ligation assay. Moreover, CHL1 inhibited agonist-triggered internalization of DRD2-S. Proximity ligation assay showed close interaction between CHL1 and DRD2 in neurons expressing dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP32) or tyrosine hydroxylase (TH) in tissue sections of adult mouse striatum. In cultures of striatum or ventral midbrain, CHL1 was also closely associated with DRD2 in DARPP32- or TH-immunopositive cells, respectively. In the dorsal striatum of CHL1-deficient mice, lower levels of DRD2 and phosphorylated TH were observed, when compared to wild-type littermates. In the ventral striatum of CHL1-deficient mice, levels of phosphorylated DARPP32 were reduced. We propose that CHL1 regulates DRD2-dependent presynaptic and postsynaptic functions.

Motor Neuron Generation from iPSCs from Identical Twins Discordant for Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a complex neurodegenerative disorder characterized by the loss of the upper and lower motor neurons. Approximately 10% of cases are caused by specific mutations in known genes, with the remaining cases having no known genetic link. As such, sporadic cases have been more difficult to model experimentally. Here, we describe the generation and differentiation of ALS induced pluripotent stem cells reprogrammed from discordant identical twins. Whole genome sequencing revealed no relevant mutations in known ALS-causing genes that differ between the twins. As protein aggregation is found in all ALS patients and is thought to contribute to motor neuron death, we sought to characterize the aggregation phenotype of the sporadic ALS induced pluripotent stem cells (iPSCs). Motor neurons from both twins had high levels of insoluble proteins that commonly aggregate in ALS that did not robustly change in response to exogenous glutamate. In contrast, established genetic ALS iPSC lines demonstrated insolubility in a protein- and genotype-dependent manner. Moreover, whereas the genetic ALS lines failed to induce autophagy after glutamate stress, motor neurons from both twins and independent controls did activate this protective pathway. Together, these data indicate that our unique model of sporadic ALS may provide key insights into disease pathology and highlight potential differences between sporadic and familial ALS.

Genetic and clinical predictors of CD4 lymphocyte recovery during suppressive antiretroviral therapy: Whole exome sequencing and antiretroviral therapy response phenotypes

Increase of peripheral blood CD4 lymphocyte counts is a key goal of combined antiretroviral therapy (cART); most, but not all, recipients respond adequately and promptly. A small number of studies have examined specific genetic factors associated with the extent of CD4 recovery. We report a genome-wide examination of factors that predict CD4 recovery in HIV-infected women. We identified women in in a cohort study who were on cART with viral load below 400 copies, and drew racially and ethnically matched samples of those with good CD4 response over 2 years or poor response. We analyzed the exomes of those women employing next generation sequencing for genes associated with CD4 recovery after controlling for non-genetic factors identified through forward stepwise selection as important. We studied 48 women with good CD4 recovery and 42 with poor CD4 recovery during virologically-suppressive cART. Stepwise logistic regression selected only age as a statistically significant (p<0.05) non-genetic predictor of response type (each additional year of age reduced the odds of good recovery by 11% (OR = 0.89, CI = 0.84–0.96, p = 0.0009). After adjustment for age and genomic estimates of race and ethnicity, 41 genes harbored variations associated with CD4 recovery group (p≤0.001); 5 of these have been previously reported to be associated with HIV infection, 4 genes would likely influence CD4 homeostasis, and 13 genes either had known functions or were members of product families that had functions for which interactions with HIV or effects on lymphocyte homeostasis were biologically plausible. Greater age was the strongest acquired factor that predicted poor CD4 cell recovery. Sequence variations spanning 41 genes were independently predictive of CD4 recovery. Many of these genes have functions that impact the cell cycle, apoptosis, lymphocyte migration, or have known interactions with HIV. These findings may help inform new hypotheses related to responses to HIV therapy and CD4 lymphocyte homeostasis.

Close Homolog of L1 Regulates Dendritic Spine Density in the Mouse Cerebral Cortex Through Semaphorin 3B

Dendritic spines in the developing mammalian neocortex are initially overproduced and then eliminated during adolescence to achieve appropriate levels of excitation in mature networks. We show here that the L1 family cell adhesion molecule Close Homolog of L1 (CHL1) and secreted repellent ligand Semaphorin 3B (Sema3B) function together to induce dendritic spine pruning in developing cortical pyramidal neurons. Loss of CHL1 in null mutant mice in both genders resulted in increased spine density and a greater proportion of immature spines on apical dendrites in the prefrontal and visual cortex. Electron microscopy showed that excitatory spine synapses with postsynaptic densities were increased in the CHL1-null cortex, and electrophysiological recording in prefrontal slices from mutant mice revealed deficiencies in excitatory synaptic transmission. Mechanistically, Sema3B protein induced elimination of spines on apical dendrites of cortical neurons cultured from wild-type but not CHL1-null embryos. Sema3B was secreted by the cortical neuron cultures, and its levels increased when cells were treated with the GABA antagonist gabazine. In vivo CHL1 was coexpressed with Sema3B in pyramidal neuron subpopulations and formed a complex with Sema3B receptor subunits Neuropilin-2 and PlexinA4. CHL1 and NrCAM, a closely related L1 adhesion molecule, localized primarily to distinct spines and promoted spine elimination to Sema3B or Sema3F, respectively. These results support a new concept in which selective spine elimination is achieved through different secreted semaphorins and L1 family adhesion molecules to sculpt functional neural circuits during postnatal maturation.SIGNIFICANCE STATEMENT Dendritic spines in the mammalian neocortex are initially overproduced and then pruned in adolescent life through unclear mechanisms to sculpt maturing cortical circuits. Here, we show that spine and excitatory synapse density of pyramidal neurons in the developing neocortex is regulated by the L1 adhesion molecule, Close Homolog of L1 (CHL1). CHL1 mediated spine pruning in response to the secreted repellent ligand Semaphorin 3B and associated with receptor subunits Neuropilin-2 and PlexinA4. CHL1 and related L1 adhesion molecule NrCAM localized to distinct spines, and promoted spine elimination to Semaphorin 3B and -3F, respectively. These results support a new concept in which selective elimination of individual spines and nascent synapses can be achieved through the action of distinct secreted semaphorins and L1 adhesion molecules.

Epigenetic Regulations in Neuropsychiatric Disorders

Precise genetic and epigenetic spatiotemporal regulation of gene expression is critical for proper brain development, function and circuitry formation in the mammalian central nervous system. Neuronal differentiation processes are tightly regulated by epigenetic mechanisms including DNA methylation, histone modifications, chromatin remodelers and non-coding RNAs. Dysregulation of any of these pathways is detrimental to normal neuronal development and functions, which can result in devastating neuropsychiatric disorders, such as depression, schizophrenia and autism spectrum disorders. In this review, we focus on the current understanding of epigenetic regulations in brain development and functions, as well as their implications in neuropsychiatric disorders.

Attempts to replicate genetic associations with schizophrenia in a cohort from north India

Schizophrenia is a chronic, severe, heritable disorder. Genome-wide association studies, conducted predominantly among Caucasians, have indicated > 100 risk alleles, with most significant SNPs on chromosome 6. There is growing interest as to whether these risk alleles are relevant in other ethnic groups as well. Neither an Indian genome-wide association studies nor a systematic replication of GWAS findings from other populations are reported. Thus, we analyzed 32 SNPs, including those associated in the Caucasian ancestry GWAS and other candidate gene studies, in a north Indian schizophrenia cohort (n = 1009 patients; n = 1029 controls) using a Sequenom mass array. Cognitive functioning was also assessed using the Hindi version of the Penn Computerized Neuropsychological Battery in a subset of the sample. MICB (rs6916394) a previously noted Caucasian candidate, was associated with schizophrenia at the p = 0.02 level. One SNP, rs2064430, AHI1 (6q23.3, SZ Gene database SNP) was associated at the p = 0.04 level. Other candidates had even less significance with rs6932590, intergenic (p = 0.07); rs3130615, MICB (p = 0.08); rs6916921, NFKBIL1 (p = 0.08) and rs9273012, HLA-DQA1 (p = 0.06) and haplotypic associations (p = 0.01-0.05) of 6p SNPs were detected. Of note, nominally significant associations with cognitive variables were identified, after covarying for age and diagnostic status. SNPs with p < 0.01 were: rs3130375, with working memory (p = 0.007); rs377763, with sensorimotor (p = 0.004); rs6916921, NFKBIL1 with emotion (p = 0.01). This relative lack of significant positive associations is likely influenced by the sample size and/or differences in the genetic architecture of schizophrenia across populations, encouraging population specific studies to identify shared and unique genetic risk factors for schizophrenia.

POPULATION GENETICS

CAUCASIANS AND INDIANS EXHIBIT GENETIC DISJUNCTION IN SCHIZOPHRENIA: A tenuous link between schizophrenia's genetic basis in Caucasians and Indians calls for more comprehensive research on the latter. Large-scale analyses of the human genome have identified over a hundred genetic variations associated with schizophrenia; however, these have focused largely on European and North American populations. Researchers led by the University of Delhi's BK Thelma, and Smita Deshpande of the Dr. Ram Manohar Lohia Hospital, India, selected 32 gene variations from past studies to look for similar associations in Indians. Many assays met limited success, though the team found significant correlations between certain variations and specific cognitive hallmarks of schizophrenia. Aside from differences in genetic architecture, the lack of adequate and comparable genetic data on schizophrenia in Indians may contribute to this apparent difference to schizophrenia in Caucasian patients. This shows a clear need for more schizophrenia genetic studies in India.

Homophilic binding of the neural cell adhesion molecule CHL1 regulates development of ventral midbrain dopaminergic pathways

Abnormal development of ventral midbrain (VM) dopaminergic (DA) pathways, essential for motor and cognitive function, may underpin a number of neurological disorders and thereby highlight the importance of understanding the birth and connectivity of the associated neurons. While a number of regulators of VM DA neurogenesis are known, processes involved in later developmental events, including terminal differentiation and axon morphogenesis, are less well understood. Recent transcriptional analysis studies of the developing VM identified genes expressed during these stages, including the cell adhesion molecule with homology to L1 (Chl1). Here, we map the temporal and spatial expression of CHL1 and assess functional roles of substrate-bound and soluble-forms of the protein during VM DA development. Results showed early CHL1 in the VM, corresponding with roles in DA progenitor migration and differentiation. Subsequently, we demonstrated roles for CHL1 in both axonal extension and repulsion, selectively of DA neurons, suggestive of a role in guidance towards forebrain targets and away from hindbrain nuclei. In part, CHL1 mediates these roles through homophilic CHL1-CHL1 interactions. Collectively, these findings enhance our knowledge of VM DA pathways development, and may provide new insights into understanding DA developmental conditions such as autism spectrum disorders.

Chronic mild stress impairs latent inhibition and induces region-specific neural activation in CHL1-deficient mice, a mouse model of schizophrenia

Schizophrenia is a neurodevelopmental disorder characterized by abnormal processing of information and attentional deficits. Schizophrenia has a high genetic component but is precipitated by environmental factors, as proposed by the 'two-hit' theory of schizophrenia. Here we compared latent inhibition as a measure of learning and attention, in CHL1-deficient mice, an animal model of schizophrenia, and their wild-type littermates, under no-stress and chronic mild stress conditions. All unstressed mice as well as the stressed wild-type mice showed latent inhibition. In contrast, CHL1-deficient mice did not show latent inhibition after exposure to chronic stress. Differences in neuronal activation (c-Fos-positive cell counts) were noted in brain regions associated with latent inhibition: Neuronal activation in the prelimbic/infralimbic cortices and the nucleus accumbens shell was affected solely by stress. Neuronal activation in basolateral amygdala and ventral hippocampus was affected independently by stress and genotype. Most importantly, neural activation in nucleus accumbens core was affected by the interaction between stress and genotype. These results provide strong support for a 'two-hit' (genes x environment) effect on latent inhibition in CHL1-deficient mice, and identify CHL1-deficient mice as a model of schizophrenia-like learning and attention impairments.

Whole-genome sequencing in multiplex families with psychoses reveals mutations in the SHANK2 and SMARCA1 genes segregating with illness

A current focus in psychiatric genetics is detection of multiple common risk alleles through very large genome-wide association study analyses. Yet families do exist, albeit rare, that have multiple affected members who are presumed to have a similar inherited cause to their illnesses. We hypothesized that within some of these families there may be rare highly penetrant mutations that segregate with illness. In this exploratory study, the genomes of 90 individuals across nine families were sequenced. Each family included a minimum of three available relatives affected with a psychotic illness and three available unaffected relatives. Twenty-six variants were identified that are private to a family, alter protein sequence, and are transmitted to all sequenced affected individuals within the family. In one family, seven siblings with schizophrenia spectrum disorders each carry a novel private missense variant within the SHANK2 gene. This variant lies within the consensus SH3 protein-binding motif by which SHANK2 may interact with post-synaptic glutamate receptors. In another family, four affected siblings and their unaffected mother each carry a novel private missense variant in the SMARCA1 gene on the X chromosome. Both variants represent candidates that may be causal for psychotic disorders when considered in the context of their transmission pattern and known gene and disease biology.

Laboratory testing for the diagnosis, evaluation, and management of systemic lupus erythematosus: Still more questions for the next generations: A Tribute and Thanks and in Memory of my mentor: Henry G. Kunkel

This paper is a review, personal memoir, a tribute to Henry Kunkel, and a critique regarding laboratory tests used for the evaluation, diagnosis, and understanding Autoimmune Rheumatic Diseases, in particular systemic lupus erythematosus (SLE).

Reversal of dendritic phenotypes in 16p11.2 microduplication mouse model neurons by pharmacological targeting of a network hub

The architecture of dendritic arbors contributes to neuronal connectivity in the brain. Conversely, abnormalities in dendrites have been reported in multiple mental disorders and are thought to contribute to pathogenesis. Rare copy number variations (CNVs) are genetic alterations that are associated with a wide range of mental disorders and are highly penetrant. The 16p11.2 microduplication is one of the CNVs most strongly associated with schizophrenia and autism, spanning multiple genes possibly involved in synaptic neurotransmission. However, disease-relevant cellular phenotypes of 16p11.2 microduplication and the driver gene(s) remain to be identified. We found increased dendritic arborization in isolated cortical pyramidal neurons from a mouse model of 16p11.2 duplication (dp/+). Network analysis identified MAPK3, which encodes ERK1 MAP kinase, as the most topologically important hub in protein-protein interaction networks within the 16p11.2 region and broader gene networks of schizophrenia-associated CNVs. Pharmacological targeting of ERK reversed dendritic alterations associated with dp/+ neurons, outlining a strategy for the analysis and reversal of cellular phenotypes in CNV-related psychiatric disorders.

Association study of MiRSNPs with schizophrenia, tardive dyskinesia and cognition

MicroRNAs (miRNAs) bind to 3'UTRs of genes and negatively regulate their expression. With ~50% of miRNAs expressing in the brain, they play an important role in neuronal development, plasticity, cognition and neurological disorders. Conserved miRNA targets are present in >60% genes in humans and are under evolutionary pressure to maintain pairing with miRNA. However, such binding may be affected by genetic variant(s) in the target sites (MiRSNPs), thereby altering gene expression. Differential expression of a large number of genes in postmortem brains of schizophrenia (SZ) patients compared to controls has been documented. Thus studying the role of MiRSNPs which are underinvestigated in SZ becomes attractive. We systematically selected 35 MiRSNPs with predicted functional relevance in 3'UTRs of genes shown previously to be associated with SZ, genotyped and tested their association with disease, using independent discovery and replication samples (total n=1017 cases; n=1073 controls). We also explored genetic associations with two sets of quantitative traits, namely tardive dyskinesia (TD) and cognitive functions disrupted in SZ in subsets of the study cohort. In the primary analysis, a significant association of MiRSNP rs7430 at PPP3CC was observed with SZ in the discovery and the replication samples [discovery: P=0.01; OR (95% CI) 1.24 (1.04-1.48); replication: P=0.03; OR (95% CI) 1.20 (1.02-1.43)]. In the exploratory analyses, five SNPs were nominally associated with TD (P values 0.04-0.004). Separately, 12 SNPs were associated with one or more of the eight cognitive domains (P values 0.05-0.003). These associations, particularly the SNP at PPP3CC merit further investigations.

Small RNAs: essential regulators of gene expression and defenses against environmental stresses in plants

Eukaryotic genomes produce thousands of diverse small RNAs (smRNAs), which play vital roles in regulating gene expression in all conditions, including in survival of biotic and abiotic environmental stresses. SmRNA pathways intersect with most of the pathways regulating different steps in the life of a messenger RNA (mRNA), starting from transcription and ending at mRNA decay. SmRNAs function in both nuclear and cytoplasmic compartments; the regulation of mRNA stability and translation in the cytoplasm and the epigenetic regulation of gene expression in the nucleus are the main and best-known modes of smRNA action. However, recent evidence from animal systems indicates that smRNAs and RNA interference (RNAi) also participate in the regulation of alternative pre-mRNA splicing, one of the most crucial steps in the fast, efficient global reprogramming of gene expression required for survival under stress. Emerging evidence from bioinformatics studies indicates that a specific class of plant smRNAs, induced by various abiotic stresses, the sutr-siRNAs, has the potential to target regulatory regions within introns and thus may act in the regulation of splicing in response to stresses. This review summarizes the major types of plant smRNAs in the context of their mechanisms of action and also provides examples of their involvement in regulation of gene expression in response to environmental cues and developmental stresses. In addition, we describe current advances in our understanding of how smRNAs function in the regulation of pre-mRNA splicing. WIREs RNA 2016, 7:356-381. doi: 10.1002/wrna.1340 For further resources related to this article, please visit the WIREs website.

Cadherins and catenins in dendrite and synapse morphogenesis

Neurons are highly polarized specialized cells. Neuronal integrity and functional roles are critically dependent on dendritic architecture and synaptic structure, function and plasticity. The cadherins are glycosylated transmembrane proteins that form cell adhesion complexes in various tissues. They are associated with a group of cytosolic proteins, the catenins. While the functional roles of the complex have been extensively investigates in non-neuronal cells, it is becoming increasingly clear that components of the complex have critical roles in regulating dendritic and synaptic architecture, function and plasticity in neurons. Consistent with these functional roles, aberrations in components of the complex have been implicated in a variety of neurodevelopmental disorders. In this review, we discuss the roles of the classical cadherins and catenins in various aspects of dendrite and synapse architecture and function and their relevance to human neurological disorders. Cadherins are glycosylated transmembrane proteins that were initially identified as Ca(2+)-dependent cell adhesion molecules. They are present on plasma membrane of a variety of cell types from primitive metazoans to humans. In the past several years, it has become clear that in addition to providing mechanical adhesion between cells, cadherins play integral roles in tissue morphogenesis and homeostasis. The cadherin family is composed of more than 100 members and classified into several subfamilies, including classical cadherins and protocadherins. Several of these cadherin family members have been implicated in various aspects of neuronal development and function. (1-3) The classical cadherins are associated with a group of cytosolic proteins, collectively called the catenins. While the functional roles of the cadherin-catenin cell adhesion complex have been extensively investigated in epithelial cells, it is now clear that components of the complex are well expressed in central neurons at different stages during development. (4,5) Recent exciting studies have shed some light on the functional roles of cadherins and catenins in central neurons. In this review, we will provide a brief overview of the cadherin superfamily, describe cadherin family members expressed in central neurons, cadherin-catenin complexes in central neurons and then focus on role of the cadherin-catenin complex in dendrite morphogenesis and synapse morphogenesis, function and plasticity. The final section is dedicated to discussion of the emerging list of neural disorders linked to cadherins and catenins. While the roles of cadherins and catenins have been examined in several different types of neurons, the focus of this review is their role in mammalian central neurons, particularly those of the cortex and hippocampus. Accompanying this review is a series of excellent reviews targeting the roles of cadherins and protocadherins in other aspects of neural development.

Dysfunction in the coagulation system and schizophrenia

Although different hypotheses have been formulated to explain schizophrenia pathogenesis, the links between them are weak. The observation that five psychotic patients on chronic warfarin therapy for deep-vein thrombosis showed long-term remission of psychotic symptoms made us suspect that abnormalities in the coagulation pathway, specifically low tissue plasminogen activator (tPA) activity, could be one of the missing links. Our hypothesis is supported by a high prevalence of conditions affecting tPA activity in drug-naive schizophrenia, such as antiphospholipid antibodies, elevated cytokine levels, hyperinsulinemia and hyperhomocysteinemia. We recently screened a group of schizophrenia patients and controls for conditions affecting tPA activity. Free-protein S deficiency was highly prevalent among patients, but not found in controls. Free-protein S and functional protein C are natural anticoagulants that form complexes that inhibit tPA inhibitors. All participants had normal protein C levels, suggesting that protein S could have a role in schizophrenia, independent of protein C. Chronic patients and those studied during acute episodes had between three and six conditions affecting tPA and/or protein S activity, while patients in remission had up to two, which led us to postulate that multiple conditions affecting tPA and/or protein S activity could contribute to the full expression of schizophrenia phenotype. This paper describes the physiological roles of tPA and protein S, reviewing how their activity influences pathogenesis and comorbidity of schizophrenia. Next, it analyzes how activity of tPA and protein S is influenced by biochemical abnormalities found in schizophrenia. Last, it suggests future directions for research, such as studies on animal models and on therapeutic approaches for schizophrenia aiming at increasing tPA and protein S activity.

Interaction between CHL1 and serotonin receptor 2c regulates signal transduction and behavior in mice

The serotonergic system plays important roles in multiple functions of the nervous system and its malfunctioning leads to neurological and psychiatric disorders. Here, we show that the cell adhesion molecule close homolog of L1 (CHL1), which has been linked to mental disorders, binds to a peptide stretch in the third intracellular loop of the serotonin 2c (5-HT2c) receptor through its intracellular domain. Moreover, we provide evidence that CHL1 deficiency in mice leads to 5-HT2c-receptor-related reduction in locomotor activity and reactivity to novelty, and that CHL1 regulates signaling pathways triggered by constitutively active isoforms of the 5-HT2c receptor. Furthermore, we found that the 5-HT2c receptor and CHL1 colocalize in striatal and hippocampal GABAergic neurons, and that 5-HT2c receptor phosphorylation and its association with phosphatase and tensin homolog (PTEN) and β-arrestin 2 is regulated by CHL1. Our results demonstrate that CHL1 regulates signal transduction pathways through constitutively active 5-HT2c receptor isoforms, thereby altering 5-HT2c receptor functions and implicating CHL1 as a new modulator of the serotonergic system.

Age-dependent loss of parvalbumin-expressing hippocampal interneurons in mice deficient in CHL1, a mental retardation and schizophrenia susceptibility gene

In humans, deletions/mutations in the CHL1/CALL gene are associated with mental retardation and schizophrenia. Juvenile CHL1-deficient (CHL1(-/-) ) mice have been shown to display abnormally high numbers of parvalbumin-expressing (PV(+) ) hippocampal interneurons and, as adults, display behavioral traits observed in neuropsychiatric disorders. Here, we addressed the question whether inhibitory interneurons and synaptic plasticity in the CHL1(-/-) mouse are affected during brain maturation and in adulthood. We found that hippocampal, but not neocortical, PV(+) interneurons were reduced with age in CHL1(-/-) mice, from a surplus of +27% at 1 month to a deficit of -20% in adulthood compared with wild-type littermates. This loss occurred during brain maturation, correlating with microgliosis and enhanced interleukin-6 expression. In parallel with the loss of PV(+) interneurons, the inhibitory input to adult CA1 pyramidal cells was reduced and a deficit in short- and long-term potentiation developed at CA3-CA1 excitatory synapses between 2 and 9 months of age in CHL1(-/-) mice. This deficit could be abrogated by a GABAA receptor agonist. We propose that region-specific aberrant GABAergic synaptic connectivity resulting from the mutation and a subsequently enhanced synaptic elimination during brain maturation lead to microgliosis, increase in pro-inflammatory cytokine levels, loss of interneurons, and impaired synaptic plasticity. Close homolog of L1-deficient (CHL1(-/-) ) mice have abnormally high numbers of parvalbumin (PV)-expressing hippocampal interneurons in juvenile animals, but in adult animals a loss of these cells is observed. This loss correlates with an increased density of microglia (M), enhanced interleukin-6 (IL6) production and a deficit in short- and long-term potentiation at CA3-CA1 excitatory synapses. Furthermore, adult CHL1(-/-) mice display behavioral traits similar to those observed in neuropsychiatric disorders of humans.

Neuronal cell adhesion genes and antidepressant response in three independent samples

Drug-effect phenotypes in human lymphoblastoid cell lines recently allowed to identify CHL1 (cell adhesion molecule with homology to L1CAM), GAP43 (growth-associated protein 43) and ITGB3 (integrin beta 3) as new candidates for involvement in the antidepressant effect. CHL1 and ITGB3 code for adhesion molecules, while GAP43 codes for a neuron-specific cytosolic protein expressed in neuronal growth cones; all the three gene products are involved in synaptic plasticity. Sixteen polymorphisms in these genes were genotyped in two samples (n=369 and 90) with diagnosis of major depressive episode who were treated with antidepressants in a naturalistic setting. Phenotypes were response, remission and treatment-resistant depression. Logistic regression including appropriate covariates was performed. Genes associated with outcomes were investigated in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) genome-wide study (n=1861) as both individual genes and through a pathway analysis (Reactome and String databases). Gene-based analysis suggested CHL1 rs4003413, GAP43 rs283393 and rs9860828, ITGB3 rs3809865 as the top candidates due to their replication across the largest original sample and the STAR*D cohort. GAP43 molecular pathway was associated with both response and remission in the STAR*D, with ELAVL4 representing the gene with the highest percentage of single nucleotide polymorphisms (SNPs) associated with outcomes. Other promising genes emerging from the pathway analysis were ITGB1 and NRP1. The present study was the first to analyze cell adhesion genes and their molecular pathways in antidepressant response. Genes and biomarkers involved in neuronal adhesion should be considered by further studies aimed to identify predictors of antidepressant response.

Conversion of psychological stress into cellular stress response: roles of the sigma-1 receptor in the process

Psychiatrists empirically recognize that excessive or chronic psychological stress can result in long-lasting impairments of brain functions that partly involve neuronal cell damage. Recent studies begin to elucidate the molecular pathways activated/inhibited by psychological stress. Activation of the hypothalamic-pituitary-adrenal axis under psychological stress causes inflammatory oxidative stresses in the brain, in part due to elevation of cytokines. Psychological stress or neuropathological conditions (e.g., accumulation of β-amyloids) trigger 'cellular stress responses', which promote upregulation of molecular chaperones to protect macromolecules from degradation. The unfolded protein response, the endoplasmic reticulum (ER)-specific cellular stress response, has been recently implicated in the pathophysiology of neuropsychiatric disorders and the pharmacology of certain clinically used drugs. The sigma-1 receptor is an ER protein whose ligands are shown to exert antidepressant-like and neuroprotective actions. Recent studies found that the sigma-1 receptor is a novel ligand-operated ER chaperone that regulates bioenergetics, free radical generation, oxidative stress, unfolded protein response and cytokine signaling. The sigma-1 receptor also regulates morphogenesis of neuronal cells, such as neurite outgrowth, synaptogenesis, and myelination, which can be perturbed by cellular stress. The sigma-1 receptor may thus contribute to a cellular defense system that protects nervous systems against chronic psychological stress. Findings from sigma receptor research imply that not only cell surface monoamine effectors but also intracellular molecules, especially those at the ER, may provide novel therapeutic targets for future drug developments.

Exome sequencing to detect rare variants associated with general cognitive ability: a pilot study

Variation in human cognitive ability is of consequence to a large number of health and social outcomes and is substantially heritable. Genetic linkage, genome-wide association, and copy number variant studies have investigated the contribution of genetic variation to individual differences in normal cognitive ability, but little research has considered the role of rare genetic variants. Exome sequencing studies have already met with success in discovering novel trait-gene associations for other complex traits. Here, we use exome sequencing to investigate the effects of rare variants on general cognitive ability. Unrelated Scottish individuals were selected for high scores on a general component of intelligence (g). The frequency of rare genetic variants (in n = 146) was compared with those from Scottish controls (total n = 486) who scored in the lower to middle range of the g distribution or on a proxy measure of g. Biological pathway analysis highlighted enrichment of the mitochondrial inner membrane component and apical part of cell gene ontology terms. Global burden analysis showed a greater total number of rare variants carried by high g cases versus controls, which is inconsistent with a mutation load hypothesis whereby mutations negatively affect g. The general finding of greater non-synonymous (vs. synonymous) variant effects is in line with evolutionary hypotheses for g. Given that this first sequencing study of high g was small, promising results were found, suggesting that the study of rare variants in larger samples would be worthwhile.

Interaction of the cell adhesion molecule CHL1 with vitronectin, integrins, and the plasminogen activator inhibitor-2 promotes CHL1-induced neurite outgrowth and neuronal migration

The cell adhesion molecule close homolog of L1 (CHL1) plays important functional roles in the developing and adult nervous system. In search of the binding partners that mediate the diverse and sometimes opposing functions of CHL1, the extracellular matrix-associated proteins vitronectin and plasminogen activator inhibitor-2 (PAI-2) were identified as novel CHL1 interaction partners and tested for involvement in CHL1-dependent functions during mouse cerebellar development. CHL1-induced cerebellar neurite outgrowth and cell migration at postnatal days 6-8 were inhibited by a CHL1-derived peptide comprising the integrin binding RGD motif, and by antibodies against vitronectin or several integrins, indicating a vitronectin-dependent integrin-mediated pathway. A PAI-2-derived peptide, or antibodies against PAI-2, urokinase type plasminogen activator (uPA), uPA receptor, and several integrins reduced cell migration. CHL1 colocalized with vitronectin, PAI-2, and several integrins in cerebellar granule cells, suggesting an association among these proteins. Interestingly, at the slightly earlier age of 4-5 d, cerebellar neurons did not depend on CHL1 for neuritogenesis and cell migration. However, differentiation of progenitor cells into neurons at this stage was dependent on homophilic CHL1-CHL1 interactions. These observations indicate that homophilic CHL1 trans-interactions regulate differentiation of neuronal progenitor cells at early postnatal stages, while heterophilic trans-interactions of CHL1 with vitronectin, integrins, and the plasminogen activator system regulate neuritogenesis and neuronal cell migration at a later postnatal stage of cerebellar morphogenesis. Thus, within very narrow time windows in postnatal cerebellar development, distinct types of molecular interactions mediated by CHL1 underlie the diverse functions of this protein.

A recurrent deletion syndrome at chromosome bands 2p11.2-2p12 flanked by segmental duplications at the breakpoints and including REEP1

We identified an identical and recurrent 9.4-Mbp deletion at chromosome bands 2p11.2-2p12, which occurred de novo in two unrelated patients. It is flanked at the distal and proximal breakpoints by two homologous segmental duplications consisting of low copy repeat (LCR) blocks in direct orientation, which have >99% sequence identity. Despite the fact that the deletion was almost 10 Mbp in size, the patients showed a relatively mild clinical phenotype, that is, mild-to-moderate intellectual disability, a happy disposition, speech delay and delayed motor development. Their phenotype matches with that of previously described patients. The 2p11.2-2p12 deletion includes the REEP1 gene that is associated with spastic paraplegia and phenotypic features related to this are apparent in most 2p11.2-2p12 deletion patients, but not in all. Other hemizygous genes that may contribute to the clinical phenotype include LRRTM1 and CTNNA2. We propose a recurrent but rare 2p11.2-2p12 deletion syndrome based on (1) the identical, non-random localisation of the de novo deletion breakpoints in two unrelated patients and a patient from literature, (2) the patients' phenotypic similarity and their phenotypic overlap with other 2p deletions and (3) the presence of highly identical LCR blocks flanking both breakpoints, consistent with a non-allelic homologous recombination (NAHR)-mediated rearrangement.

Candidate genes and functional noncoding variants identified in a canine model of obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD), a severe mental disease manifested in time-consuming repetition of behaviors, affects 1 to 3% of the human population. While highly heritable, complex genetics has hampered attempts to elucidate OCD etiology. Dogs suffer from naturally occurring compulsive disorders that closely model human OCD, manifested as an excessive repetition of normal canine behaviors that only partially responds to drug therapy. The limited diversity within dog breeds makes identifying underlying genetic factors easier.

RESULTS

We use genome-wide association of 87 Doberman Pinscher cases and 63 controls to identify genomic loci associated with OCD and sequence these regions in 8 affected dogs from high-risk breeds and 8 breed-matched controls. We find 119 variants in evolutionarily conserved sites that are specific to dogs with OCD. These case-only variants are significantly more common in high OCD risk breeds compared to breeds with no known psychiatric problems. Four genes, all with synaptic function, have the most case-only variation: neuronal cadherin (CDH2), catenin alpha2 (CTNNA2), ataxin-1 (ATXN1), and plasma glutamate carboxypeptidase (PGCP). In the 2 Mb gene desert between the cadherin genes CDH2 and DSC3, we find two different variants found only in dogs with OCD that disrupt the same highly conserved regulatory element. These variants cause significant changes in gene expression in a human neuroblastoma cell line, likely due to disrupted transcription factor binding.

CONCLUSIONS

The limited genetic diversity of dog breeds facilitates identification of genes, functional variants and regulatory pathways underlying complex psychiatric disorders that are mechanistically similar in dogs and humans.

Omega-3 fatty acid deficiency disrupts endocytosis, neuritogenesis, and mitochondrial protein pathways in the mouse hippocampus

Omega-3 fatty acid (n-3 FA) deficiency is an environmental risk factor for schizophrenia, yet characterization of the consequences of deficiency at the protein level in the brain is limited. We aimed to identify the protein pathways disrupted as a consequence of chronic n-3 deficiency in the hippocampus of mice. Fatty acid analysis of the hippocampus following chronic dietary deficiency revealed a 3-fold decrease (p < 0.001) in n-3 FA levels. Label free LC-MS/MS analysis identified and profiled 1008 proteins, of which 114 were observed to be differentially expressed between n-3 deficient and control groups (n = 8 per group). The cellular processes that were most implicated were neuritogenesis, endocytosis, and exocytosis, while specific protein pathways that were most significantly dysregulated were mitochondrial dysfunction and clathrin mediated endocytosis (CME). In order to characterize whether these processes and pathways are ones influenced by antipsychotic medication, we used LC-MS/MS to test the differential expression of these 114 proteins in the hippocampus of mice chronically treated with the antipsychotic agent haloperidol. We observed 23 of the 114 proteins to be differentially expressed, 17 of which were altered in the opposite direction to that observed following n-3 deficiency. Overall, our findings point to disturbed synaptic function, neuritogenesis, and mitochondrial function as a consequence of dietary deficiency in n-3 FA. This study greatly aids our understanding of the molecular mechanism by which n-3 deficiency impairs normal brain function, and provides clues as to how n-3 FA exert their therapeutic effect in early psychosis.

Significant association of close homologue of L1 gene polymorphism rs2272522 with schizophrenia in Qatar

INTRODUCTION

Previous reports have found that polymorphisms in the close homologue of L1 (CHL1) gene located on chromosome 3p26 are associated with schizophrenia among different ethnic populations. The aim of this study was to examine the associations of single nucleotides polymorphisms (SNPs) of the CHL1 gene locus, including rs2055314 (C/T), rs2272522 (C/T) and rs331894 (A/G), with schizophrenia in the Qatari population.

METHODS

An association case control study was carried out on 86 Qatari schizophrenic patients from the Psychiatry Hospital, Hammed Medical Corporation, Qatar and 88 Qatari unrelated, healthy, control subjects. Schizophrenia was diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition (DSM-IV) criteria for schizophrenia by two independent psychiatrists. Genotyping of the SNPs rs2055314 (C/T), rs2272522 (C/T) and rs331894 (A/G) was conducted using the 5' nuclease assay with the TaqMan MGB probe and an ABI 7500.

RESULTS

Individuals with the rs2272522 TT genotype had approximately 4.2 times greater risk of schizophrenia compared to individuals with the CC genotype (OR = 4.21; 95% CI: 1.12-15.53; P = 0.047). In addition, individuals carrying a T allele of the rs2272522 SNP had a significantly increased risk of schizophrenia (1.78 times) among the population (P = 0.028). SNPs rs2055314 and rs331894 had no significant association with schizophrenia. Pairwise linkage disequilibrium (LD) between the three polymorphisms was modest in the schizophrenic group.

DISCUSSION

The rs2272522 polymorphism was found to exhibit a highly significant association with schizophrenia in the Qatari population. This finding supports the hypothesis that cell adhesion molecules may be involved in the etiology of this disease among Qatari patients.

The regulated secretory pathway and human disease: insights from gene variants and single nucleotide polymorphisms

The regulated secretory pathway provides critical control of peptide, growth factor, and hormone release from neuroendocrine and endocrine cells, and neurons, maintaining physiological homeostasis. Propeptides and prohormones are packaged into dense core granules (DCGs), where they frequently undergo tissue-specific processing as the DCG matures. Proteins of the granin family are DCG components, and although their function is not fully understood, data suggest they are involved in DCG formation and regulated protein/peptide secretion, in addition to their role as precursors of bioactive peptides. Association of gene variation, including single nucleotide polymorphisms (SNPs), with neuropsychiatric, endocrine, and metabolic diseases, has implicated specific secreted proteins and peptides in disease pathogenesis. For example, a SNP at position 196 (G/A) of the human brain-derived neurotrophic factor gene dysregulates protein processing and secretion and leads to cognitive impairment. This suggests more generally that variants identified in genes encoding secreted growth factors, peptides, hormones, and proteins involved in DCG biogenesis, protein processing, and the secretory apparatus, could provide insight into the process of regulated secretion as well as disorders that result when it is impaired.

A combined analysis of microarray gene expression studies of the human prefrontal cortex identifies genes implicated in schizophrenia

Small cohort sizes and modest levels of gene expression changes in brain tissue have plagued the statistical approaches employed in microarray studies investigating the mechanism of schizophrenia. To combat these problems a combined analysis of six prior microarray studies was performed to facilitate the robust statistical analysis of gene expression data from the dorsolateral prefrontal cortex of 107 patients with schizophrenia and 118 healthy subjects. Multivariate permutation tests identified 144 genes that were differentially expressed between schizophrenia and control groups. Seventy of these genes were identified as differentially expressed in at least one component microarray study but none of these individual studies had the power to identify the remaining 74 genes, demonstrating the utility of a combined approach. Gene ontology terms and biological pathways that were significantly enriched for differentially expressed genes were related to neuronal cell-cell signaling, mesenchymal induction, and mitogen-activated protein kinase signaling, which have all previously been associated with the etiopathogenesis of schizophrenia. The differential expression of BAG3, C4B, EGR1, MT1X, NEUROD6, SST and S100A8 was confirmed by real-time quantitative PCR in an independent cohort using postmortem human prefrontal cortex samples. Comparison of gene expression between schizophrenic subjects with and without detectable levels of antipsychotics in their blood suggests that the modulation of MT1X and S100A8 may be the result of drug exposure. In conclusion, this combined analysis has resulted in a statistically robust identification of genes whose dysregulation may contribute to the mechanism of schizophrenia.

Cadherins in brain morphogenesis and wiring

Cadherins are Ca(2+)-dependent cell-cell adhesion molecules that play critical roles in animal morphogenesis. Various cadherin-related molecules have also been identified, which show diverse functions, not only for the regulation of cell adhesion but also for that of cell proliferation and planar cell polarity. During the past decade, understanding of the roles of these molecules in the nervous system has significantly progressed. They are important not only for the development of the nervous system but also for its functions and, in turn, for neural disorders. In this review, we discuss the roles of cadherins and related molecules in neural development and function in the vertebrate brain.

Cadherins and neuropsychiatric disorders

Cadherins mediate cell-cell adhesion but are also involved in intracellular signaling pathways associated with neuropsychiatric disease. Most of the ∼100 cadherins that are expressed in the brain exhibit characteristic spatiotemporal expression profiles. Cadherins have been shown to regulate neural tube regionalization, neuronal migration, gray matter differentiation, neural circuit formation, spine morphology, synapse formation and synaptic remodeling. The dysfunction of the cadherin-based adhesive system may alter functional connectivity and coherent information processing in the human brain in neuropsychiatric disease. Several neuropsychiatric disorders, such as epilepsy/mental retardation, autism, bipolar disease and schizophrenia, have been associated with cadherins, mostly by genome-wide association studies. For example, CDH15 and PCDH19 are associated with cognitive impairment; CDH5, CDH8, CDH9, CDH10, CDH13, CDH15, PCDH10, PCDH19 and PCDHb4 with autism; CDH7, CDH12, CDH18, PCDH12 and FAT with bipolar disease and schizophrenia; and CDH11, CDH12 and CDH13 with methamphetamine and alcohol dependency. To date, disease-causing mutations are established for PCDH19 in patients with epilepsy, cognitive impairment and/or autistic features. In conclusion, genes encoding members of the cadherin superfamily are of special interest in the pathogenesis of neuropsychiatric disease because cadherins play a pivotal role in the development of the neural circuitry as well as in mature synaptic function.

Modeling the functional genomics of autism using human neurons

Human neural progenitors from a variety of sources present new opportunities to model aspects of human neuropsychiatric disease in vitro. Such in vitro models provide the advantages of a human genetic background combined with rapid and easy manipulation, making them highly useful adjuncts to animal models. Here, we examined whether a human neuronal culture system could be utilized to assess the transcriptional program involved in human neural differentiation and to model some of the molecular features of a neurodevelopmental disorder, such as autism. Primary normal human neuronal progenitors (NHNPs) were differentiated into a post-mitotic neuronal state through addition of specific growth factors and whole-genome gene expression was examined throughout a time course of neuronal differentiation. After 4 weeks of differentiation, a significant number of genes associated with autism spectrum disorders (ASDs) are either induced or repressed. This includes the ASD susceptibility gene neurexin 1, which showed a distinct pattern from neurexin 3 in vitro, and which we validated in vivo in fetal human brain. Using weighted gene co-expression network analysis, we visualized the network structure of transcriptional regulation, demonstrating via this unbiased analysis that a significant number of ASD candidate genes are coordinately regulated during the differentiation process. As NHNPs are genetically tractable and manipulable, they can be used to study both the effects of mutations in multiple ASD candidate genes on neuronal differentiation and gene expression in combination with the effects of potential therapeutic molecules. These data also provide a step towards better understanding of the signaling pathways disrupted in ASD.

Meta-analysis of genome-wide association studies identifies common variants in CTNNA2 associated with excitement-seeking

The tendency to seek stimulating activities and intense sensations define excitement-seeking, a personality trait akin to some aspects of sensation-seeking. This trait is a central feature of extraversion and is a component of the multifaceted impulsivity construct. Those who score high on measures of excitement-seeking are more likely to smoke, use other drugs, gamble, drive recklessly, have unsafe/unprotected sex and engage in other risky behaviors of clinical and social relevance. To identify common genetic variants associated with the Excitement-Seeking scale of the Revised NEO Personality Inventory, we performed genome-wide association studies in six samples of European ancestry (N=7860), and combined the results in a meta-analysis. We identified a genome-wide significant association between the Excitement-Seeking scale and rs7600563 (P=2 × 10(-8)). This single-nucleotide polymorphism maps within the catenin cadherin-associated protein, alpha 2 (CTNNA2) gene, which encodes for a brain-expressed α-catenin critical for synaptic contact. The effect of rs7600563 was in the same direction in all six samples, but did not replicate in additional samples (N=5105). The results provide insight into the genetics of excitement-seeking and risk-taking, and are relevant to hyperactivity, substance use, antisocial and bipolar disorders.

RNA-Seq of human neurons derived from iPS cells reveals candidate long non-coding RNAs involved in neurogenesis and neuropsychiatric disorders

Genome-wide expression analysis using next generation sequencing (RNA-Seq) provides an opportunity for in-depth molecular profiling of fundamental biological processes, such as cellular differentiation and malignant transformation. Differentiating human neurons derived from induced pluripotent stem cells (iPSCs) provide an ideal system for RNA-Seq since defective neurogenesis caused by abnormalities in transcription factors, DNA methylation, and chromatin modifiers lie at the heart of some neuropsychiatric disorders. As a preliminary step towards applying next generation sequencing using neurons derived from patient-specific iPSCs, we have carried out an RNA-Seq analysis on control human neurons. Dramatic changes in the expression of coding genes, long non-coding RNAs (lncRNAs), pseudogenes, and splice isoforms were seen during the transition from pluripotent stem cells to early differentiating neurons. A number of genes that undergo radical changes in expression during this transition include candidates for schizophrenia (SZ), bipolar disorder (BD) and autism spectrum disorders (ASD) that function as transcription factors and chromatin modifiers, such as POU3F2 and ZNF804A, and genes coding for cell adhesion proteins implicated in these conditions including NRXN1 and NLGN1. In addition, a number of novel lncRNAs were found to undergo dramatic changes in expression, one of which is HOTAIRM1, a regulator of several HOXA genes during myelopoiesis. The increase we observed in differentiating neurons suggests a role in neurogenesis as well. Finally, several lncRNAs that map near SNPs associated with SZ in genome wide association studies also increase during neuronal differentiation, suggesting that these novel transcripts may be abnormally regulated in a subgroup of patients.

Extracellular matrix abnormalities in schizophrenia

Emerging evidence points to the involvement of the brain extracellular matrix (ECM) in the pathophysiology of schizophrenia (SZ). Abnormalities affecting several ECM components, including Reelin and chondroitin sulfate proteoglycans (CSPGs), have been described in subjects with this disease. Solid evidence supports the involvement of Reelin, an ECM glycoprotein involved in corticogenesis, synaptic functions and glutamate NMDA receptor regulation, expressed prevalently in distinct populations of GABAergic neurons, which secrete it into the ECM. Marked changes of Reelin expression in SZ have typically been reported in association with GABA-related abnormalities in subjects with SZ and bipolar disorder. Recent findings from our group point to substantial abnormalities affecting CSPGs, a main ECM component, in the amygdala and entorhinal cortex of subjects with schizophrenia, but not bipolar disorder. Striking increases of glial cells expressing CSPGs were accompanied by reductions of perineuronal nets, CSPG- and Reelin-enriched ECM aggregates enveloping distinct neuronal populations. CSPGs developmental and adult functions, including neuronal migration, axon guidance, synaptic and neurotransmission regulation are highly relevant to the pathophysiology of SZ. Together with reports of anomalies affecting several other ECM components, these findings point to the ECM as a key component of the pathology of SZ. We propose that ECM abnormalities may contribute to several aspects of the pathophysiology of this disease, including disrupted connectivity and neuronal migration, synaptic anomalies and altered GABAergic, glutamatergic and dopaminergic neurotransmission.

VMAT2: a dynamic regulator of brain monoaminergic neuronal function interacting with drugs of abuse

The monoaminergic neuron, in particular the dopaminergic neuron, is central to mediating the hedonic and addictive properties of drugs of abuse. The effects of amphetamine (AMPH) and cocaine (COC), for example, depend on the ability to increase dopamine in the synapse, by effects on either the plasma membrane transporter DAT or the vesicular transporter for monoamine storage, VMAT2. The potential role of DAT as a target for AMPH and COC has been reviewed extensively. Here, we present VMAT2 as a target that enables the rewarding and addictive actions of these drugs, based on imaging, neurochemical, biochemical, cell biological, genetic, and immunohistochemical evidence. The presence of VMAT2 in noradrenergic, serotoninergic, histaminergic, and potentially trace aminergic neurons invites consideration of a wider role for aminergic neurotransmission in AMPH and COC abuse and addiction.