Identification in 2 Independent Samples of a Novel Schizophrenia RiskHaplotype of the Dystrobrevin Binding Protein Gene (DTNBP1)

Gene Expression and Epigenetic Regulation in the Prefrontal Cortex of Schizophrenia

Schizophrenia pathogenesis remains challenging to define; however, there is strong evidence that the interaction of genetic and environmental factors causes the disorder. This paper focuses on transcriptional abnormalities in the prefrontal cortex (PFC), a key anatomical structure that determines functional outcomes in schizophrenia. This review summarises genetic and epigenetic data from human studies to understand the etiological and clinical heterogeneity of schizophrenia. Gene expression studies using microarray and sequencing technologies reported the aberrant transcription of numerous genes in the PFC in patients with schizophrenia. Altered gene expression in schizophrenia is related to several biological pathways and networks (synaptic function, neurotransmission, signalling, myelination, immune/inflammatory mechanisms, energy production and response to oxidative stress). Studies investigating mechanisms driving these transcriptional abnormalities focused on alternations in transcription factors, gene promoter elements, DNA methylation, posttranslational histone modifications or posttranscriptional regulation of gene expression mediated by non-coding RNAs.

Association of DTNBP1 With Schizophrenia: Findings From Two Independent Samples of Han Chinese Population

OBJECTIVES

Schizophrenia (SZ) is a complex psychiatric disorder that has a strong genetic basis. Dystrobrevin-binding protein 1 (DTNBP1) is one of the genes thought to be pivotal in regulating the glutamatergic system. Studies have suggested that variations in DTNBP1 confer susceptibility to SZ and clinical symptoms. Here, we performed a two-stage independent verification study to identify polymorphisms of the DTNBP1 gene that might be associated with SZ in the Han Chinese population.

METHODS

In stage 1, 14 single nucleotide polymorphisms (SNPs) were genotyped in 528 paranoid SZ patients and 528 healthy controls (HCs) using the Illumina GoldenGate assays on a BeadStation 500G Genotyping System. In stage 2, ten SNPs were genotyped in an independent sample of 1,031 SZ patients and 621 HCs using the Illumina 660k Genotyping System. Clinical symptoms were assessed using the Positive and Negative Syndrome Scale.

RESULTS

There was a significant association related to allele frequency, and a trend association in relation to genotype between SZ patients and HCs at rs4712253 (p = 0.03 and 0.05, respectively). These associations were not evident following Bonferroni correction (p > 0.05 for both). Haplotype association analysis revealed that only two haplotypes (GAG and GAA; rs16876575-rs9464793-rs4712253) were significantly different between SZ patients and HCs (χ² = 4.24, 6.37, p = 0.04 and 0.01, respectively). In addition, in SZ patients there was a significant association in the rs4964793 genotype for positive symptoms, and in the rs1011313 genotype for excitement/hostility symptoms (p = 0.01 and 0.002, respectively). We found a significant association in the baseline symbol digital modalities test (SDMT), forward-digital span (DS), backward-DS, and semantic fluency between SZ patients and HCs (p < 0.05 for all). Finally, the SNP rs1011313 genotypes were associated with SDMT in SZ patients (p = 0.04).

CONCLUSION

This study provides further evidence that SNP rs4712253 of DTNBP1 has a nominal association with SZ in the Han Chinese population. Such a genotype variation may play a role in psychopathology and cognitive function.

Association of functional polymorphisms in 3'-untranslated regions of COMT, DISC1, and DTNBP1 with schizophrenia: a meta-analysis

INTRODUCTION

In recent years, various studies have accumulated evidence of the involvement of single nucleotide polymorphisms (SNPs) in introns and exons in schizophrenia. The association of functional SNPs in the 3'-untranslated regions with schizophrenia has been explored in a number of studies, but the results are inconclusive because of limited meta-analyses. To systematically analyze the association between SNPs in 3'-untranslated regions and schizophrenia, we conducted a meta-analysis by combining all available studies on schizophrenia candidate genes.

MATERIALS AND METHODS

We searched candidate genes from the schizophrenia database and performed a comprehensive meta-analysis using all the available data up to August 2017. The association between susceptible SNPs and schizophrenia was assessed by the pooled odds ratio with 95% confidence interval using fixed-effect and random-effect models.

RESULTS

A total of 21 studies including 8291 cases and 9638 controls were used for meta-analysis. Three investigated SNPs were rs165599, rs3737597, and rs1047631 of COMT, DISC1, and DTNBP1, respectively. Our results suggested that rs3737597 showed a significant association with schizophrenia in Europeans (odds ratio: 1.584, P: 0.002, 95% confidence interval: 1.176-2.134) under a random-effect framework.

CONCLUSION

This meta-analysis indicated that rs3737597 of DISC1 was significantly associated with schizophrenia in Europeans, and it can be suggested as an ethnic-specific risk genetic factor.

Neurodevelopmental disease mechanisms, primary cilia, and endosomes converge on the BLOC-1 and BORC complexes

The biogenesis of lysosome-related organelles complex-1 (BLOC-1) and the bloc-one-related complex (BORC) are the cytosolic protein complexes required for specialized membrane protein traffic along the endocytic route and the spatial distribution of endosome-derived compartments, respectively. BLOC-1 and BORC complex subunits and components of their interactomes have been associated with the risk and/or pathomechanisms of neurodevelopmental disorders. Thus, cellular processes requiring BLOC-1 and BORC interactomes have the potential to offer novel insight into mechanisms underlying behavioral defects. We focus on interactions between BLOC-1 or BORC subunits with the actin and microtubule cytoskeleton, membrane tethers, and SNAREs. These interactions highlight requirements for BLOC-1 and BORC in membrane movement by motors, control of actin polymerization, and targeting of membrane proteins to specialized cellular domains such as the nerve terminal and the primary cilium. We propose that the endosome-primary cilia pathway is an underappreciated hub in the genesis and mechanisms of neurodevelopmental disorders. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 311-330, 2018.

Increased dysbindin-1B isoform expression in schizophrenia and its propensity in aggresome formation

Genetic variations in the human dysbindin-1 gene (DTNBP1) have been associated with schizophrenia. As a result of alternative splicing, the human DTNBP1 gene generates at least three distinct protein isoforms, dysbindin-1A, -1B and -1C. Significant effort has focused on dysbindin-1A, an important player in multiple steps of neurodevelopment. However, the other isoforms, dysbindin-1B and dysbindin-1C have not been well characterized. Nor have been associated with human diseases. Here we report an increase in expression of DTNBP1b mRNA in patients with paranoid schizophrenia as compared with healthy controls. A single-nucleotide polymorphism located in intron 9, rs117610176, has been identified and associated with paranoid schizophrenia, and its C allele leads to an increase of DTNBP1b mRNA splicing. Our data show that different dysbindin splicing isoforms exhibit distinct subcellular distribution, suggesting their distinct functional activities. Dysbindin-1B forms aggresomes at the perinuclear region, whereas dysbindin-1A and -1C proteins exhibit diffused patterns in the cytoplasm. Dysbindin-1A interacts with dysbindin-1B, getting recruited to the aggresome structure when co-expressed with dysbindin-1B. Moreover, cortical neurons over-expressing dysbindin-1B show reduction in neurite outgrowth, suggesting that dysbindin-1B may interfere with dysbindin-1A function in a dominant-negative manner. Taken together, our study uncovers a previously unknown association of DTNBP1b expression with schizophrenia in addition to its distinct biochemical and functional properties.

Genetic polymorphism in DTNBP1 gene is associated with methamphetamine-induced panic disorder

OBJECTIVE

The dysbindin-1 (dystrobrevin-binding protein-1 [DTNBP-1]) gene has repeatedly been shown to be associated with psychotic disorder across diverse populations. In this study, we attempted to investigate the association of the rs3213207 (P1635) genetic polymorphism of the DTNBP1 gene with methamphetamine dependence and with methamphetamine-induced psychosis, manic episodes, and panic disorder in a male Malaysian population.

METHODS

This polymorphism was genotyped in 233 male methamphetamine-dependent subjects and in 301 male controls of the following 4 different ethnicities: Malay, Chinese, Kadazan-Dusun, and Bajau. Intergroup statistical analyses were performed by using the χ(2) test and the Fisher exact test where necessary. In cases of multiple comparisons, the Bonferroni correction was performed.

RESULTS

Our results indicated that the DTNBP1 rs3213207 polymorphism did not show any significant association with risk of methamphetamine dependence, either in the pooled subjects or after stratification into the 4 different ethnic groups (P > 0.05). Furthermore, we did not find any association of this polymorphism with methamphetamine-induced psychosis and episodes of methamphetamine-induced mania. However, there was a strong association between this polymorphism and the occurrence of methamphetamine-induced panic disorder in the pooled subjects (odds ratio [OR] = 6.739, P < 0.001) and in the Malay (OR = 11.93, P = 0.022) and Kadazan-Dusun (OR = 115.0, P < 0.001) groups.

CONCLUSIONS

Our findings suggest that the DTNBP1 rs3213207 polymorphism may contribute to methamphetamine-induced panic disorder in the pooled Malaysian male population, especially in the Malay and Kadazan-Dusun ethnic groups. However, no association was found with methamphetamine dependence, methamphetamine-induced psychosis, or methamphetamine-induced mania.

Genes and schizophrenia: from a Festschrift Seminar honoring William T. Carpenter Jr, MD

Recent data have begun to elucidate the genetic architecture of schizophrenia, as well as provide new insights into the relationships of specific genetic factors across diagnostic boundaries, with specific symptom domains, and in the prediction of antipsychotic treatment response. Not surprisingly, work conducted at the Maryland Psychiatric Research Center (MPRC), led by Dr William Carpenter, has helped to guide the thinking behind much of this work, as well as contributed valuable data toward these efforts. In this article, I will briefly summarize some of the major findings emerging from these lines of research and highlight the role of the Dr Carpenter and his colleagues at the MPRC in this area.

Epistatic interaction between COMT and DTNBP1 modulates prefrontal function in mice and in humans

Cognitive functions are highly heritable and the impact of complex genetic interactions, though undoubtedly important, has received little investigation. Here we show in an animal model and in a human neuroimaging experiment a consistent non-linear interaction between two genes--catechol-O-methyl transferase (COMT) and dysbindin (dys; dystrobrevin-binding protein 1 (DTNBP1))--implicated through different mechanisms in cortical dopamine signaling and prefrontal cognitive function. In mice, we found that a single genetic mutation reducing expression of either COMT or DTNBP1 alone produced working memory advantages, while, in dramatic contrast, genetic reduction of both in the same mouse produced working memory deficits. We found evidence of the same non-linear genetic interaction in prefrontal cortical function in humans. In healthy volunteers (N=176) studied with functional magnetic resonance imaging during a working memory paradigm, individuals homozygous for the COMT rs4680 Met allele that reduces COMT enzyme activity showed a relatively more efficient prefrontal engagement. In contrast, we found that the same genotype was less efficient on the background of a dys haplotype associated with decreased DTNBP1 expression. These results illustrate that epistasis can be functionally multi-directional and non-linear and that a putatively beneficial allele in one epistastic context is a relatively deleterious one in another. These data also have important implications for single-locus association analyses of complex traits.

Differences between blood donors and a population sample: implications for case-control studies

BACKGROUND

Selecting appropriate controls for studies of genetic variation in case series is important. The two major candidates involve the use of blood donors or a random sample of the population.

METHODS

We compare and contrast the two different populations of controls for studies of genetic variation using data from parents enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC). In addition we compute different biases using a series of hypothetical assumptions.

RESULTS

The study subjects who had been blood donors differed markedly from the general population in social, health-related, anthropometric, and personality-related variables. Using theoretical examples, we show that blood donors are a poor control group for non-genetic studies of diseases related to environmentally, behaviourally, or socially patterned exposures. However, we show that if blood donors are used as controls in genetic studies, these factors are unlikely to make a major difference in detecting true associations with relatively rare disorders (cumulative incidence through life of <10%). Nevertheless, for more common disorders, the reduction in accuracy resulting from the inclusion in any control population of individuals who have or will develop the disease in question can create a greater bias than can socially patterned factors.

CONCLUSIONS

Information about the medical history of a control and the parents of the control (as a proxy for whether the control will develop the disease) is more important with regard to the choice of controls than whether the controls are a random population sample or blood donors.

The DTNBP1 (dysbindin-1) gene variant rs2619522 is associated with variation of hippocampal and prefrontal grey matter volumes in humans

DTNBP1 is one of the most established susceptibility genes for schizophrenia, and hippocampal volume reduction is one of the major neuropathological findings in this severe disorder. Consistent with these findings, the encoded protein dysbindin-1 has been shown to be diminished in glutamatergic hippocampal neurons in schizophrenic patients. The aim of this study was to investigate the effects of two single nucleotide polymorphisms of DTNBP1 on grey matter volumes in human subjects using voxel-based morphometry. Seventy-two subjects were included and genotyped with respect to two single nucleotide polymorphisms of DTNBP1 (rs2619522 and rs1018381). All participants underwent structural magnetic resonance imaging (MRI). MRI data were preprocessed and statistically analysed using standard procedures as implemented in SPM5 (Statistical Parametric Mapping), in particular the voxel-based morphometry (VBM) toolbox. We found significant effects of the DTNBP1 SNP rs2619522 bilaterally in the hippocampus as well as in the anterior middle frontal gyrus and the intraparietal cortex. Carriers of the G allele showed significantly higher grey matter volumes in these brain regions than T/T homozygotes. Compatible with previous findings on a role of dysbindin in hippocampal functions as well as in major psychoses, the present study provides first direct in vivo evidence that the DTNBP1 SNP rs2619522 is associated with variation of grey matter volumes bilaterally in the hippocampus.

Association of genetic variations in DTNBP1 with cognitive function in schizophrenia patients and healthy subjects

The dystrobrevin-binding protein 1 gene (DTNBP1) has been regarded as a susceptibility gene for schizophrenia. Recent studies have investigated its role on cognitive function that is frequently impaired in schizophrenia patients, and generated inconsistent results. The present study was performed to elucidate effects of genetic variations in DTNBP1 on various cognitive domains in both schizophrenia patients and healthy subjects. Comprehensive neuropsychological tests were administered to 122 clinically stable schizophrenia patients and 119 healthy subjects. Based on positive findings reported in previous association studies, six SNPs were selected and genotyped. Compared to healthy subjects, schizophrenia patients showed expected lower performance for all of the cognitive domains. After adjusting for age, gender, and educational level, four SNPs showed a nominally significant association with cognitive domains. The association of rs760761 and rs1018381 with the attention and vigilance domain remained significant after applying the correction for multiple testing (P < 0.001). Similar association patterns were observed both, in patients and healthy subjects. The observed results suggest the involvement of DTNBP1 not only in the development of attention deficit of schizophrenia, but also in the inter-individual variability of this cognitive domain within the normal functional range.

Association of P1635 and P1655 polymorphisms in dysbindin (DTNBP1) gene with schizophrenia

OBJECTIVES

Schizophrenia (SCZ) is a severe psychiatric disorder with a lifetime prevalence of approximately 1% in most of the populations studied. SCZ is multifactorial with the contribution of multiple susceptibility genes that could act in conjunction with epigenetic processes and environmental factors. There is some evidence supporting the association between genetic variants in dysbindin (DTNBP1) gene and SCZ in populations. In this study, we investigated the association between polymorphisms P1635 and P1655 in dysbindin gene with SCZ.

METHODS

Totally, 115 unrelated patients with SCZ and 117 unrelated healthy volunteers were studied. Genomic DNA was extracted from blood. Genotyping was done with the PCR-RFLP method. The allele and genotype associations were analysed with X 2 test. The Benjamini-Hochberg procedure was used to correct p values for multiple comparisons.

RESULTS

The results showed no significant difference between patients and controls in allelic frequencies or genotypic distributions of SNP P1635 (p = 0.809), but a significant difference between the case and control groups for SNP P1655 (p = 0.009) was found. We could also find a significant positive association between A-C haplotype and SCZ (OR = 1.7, 95% CI 1.18-2.42; p = 0.004, p c = 0.02) and a protective effect for A-G haplotype (p = 0.003, OR = 0.57, 95% CI 1.18-2.42; p = 0.003, p c = 0.02).

CONCLUSION

This study may provide further support for the association between SNP polymorphisms in DTNBP1 and SCZ in the Iranian population. Studies with more markers and subjects for various populations will be necessary to understand the genetic contribution of the gene to the development of SCZ.

Can genetics inform the management of cognitive deficits in schizophrenia?

There is no doubt that schizophrenia has a significant genetic component and a number of candidate genes have been identified for this debilitating disorder. Of note, several of these are implicated in cognition. Cognitive deficits constitute core symptoms of schizophrenia, and while current antipsychotic treatment strategies aim to help psychosis-related symptomatology, the cognitive symptom domain is largely inadequately treated. A number of other pharmacological approaches (e.g. using drugs that target specific neurotransmitter systems) have also been attempted for the amelioration of cognitive deficits in this population; however, these too have had limited success so far. Psychological interventions appear promising, though there has been speculation regarding whether or not these produce long-term functional improvements. Pharmacogenetic studies of the cognitive effects of currently available antipsychotics, although in relatively early stages, suggest that the treatment of cognitive deficits in schizophrenia may be advanced by focusing on genetic variants associated with specific cognitive dysfunctions in the general population and using this to match the most relevant pharmacological and/or psychological interventions with the genetic and cognitive profiles of the target population. Such a strategy would encourage bottom-up advances in drug development and provide a platform for individualised treatment of cognitive deficits in schizophrenia.

Association Study of the Dystrobrevin-Binding Gene With Schizophrenia in Australian and Indian Samples

Numerous studies have reported association between variants in the dystrobrevin binding protein 1 (dysbindin) gene (DTNBP1) and schizophrenia. However, the pattern of results is complex and to date, no specific risk marker or haplotype has been consistently identified. The number of single nucleotide polymorphisms (SNPs) tested in these studies has ranged from 5 to 20. We attempted to replicate previous findings by testing 16 SNPs in samples of 41 Australian pedigrees, 194 Australian cases and 180 controls, and 197 Indian pedigrees. No globally significant evidence for association was observed in any sample, despite power calculations indicating sufficient power to replicate several previous findings. Possible explanations for our results include sample differences in background linkage dis-equilibrium and/or risk allele effect size, the presence of multiple risk alleles upon different haplotypes, or the presence of a single risk allele upon multiple haplotypes. Some previous associations may also represent false positives. Examination of Caucasian HapMap phase II genotype data spanning theDTNBP1region indicates upwards of 40 SNPs are required to satisfactorily assess all nonredundant variation withinDTNBP1and its potential regulatory regions for association with schizophrenia. More comprehensive studies in multiple samples will be required to determine whether specificDTNBP1variants function as risk factors for schizophrenia.

Dysbindin-1 modulates prefrontal cortical activity and schizophrenia-like behaviors via dopamine/D2 pathways

Dysbindin-1 regulates D2-receptor trafficking and is implicated in schizophrenia and related cognitive abnormalities, but whether this molecular effect mediates the clinical manifestations of the disorder is unknown. We explored in dysbindin-1-deficient mice (dys-/-) (1) schizophrenia-related behaviors, (2) molecular and electrophysiological changes in medial prefrontal cortex (mPFC) and (3) the dependence of these on D2-receptor stimulation. Dysbindin-1 disruption altered dopamine-related behaviors and impaired working memory under challenging/stressful conditions. Dys-/- pyramidal neurons in mPFC layers II/III were hyperexcitable at baseline but hypoexcitable following D2 stimulation. Dys-/- were also respectively more and less sensitive to D2 agonist- and antagonist-induced behavioral effects. Dys-/- had reduced expression of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and CaMKKβ in mPFC. Chronic D2 agonist treatment reproduced these changes in protein expression, and some of the dys-/- behavioral effects. These results elucidate dysbindin's modulation of D2-related behavior, cortical activity and mPFC CaMK components, implicating cellular and molecular mechanisms of the association of dysbindin with psychosis.

Ablation of Mrds1/Ofcc1 induces hyper-γ-glutamyl transpeptidasemia without abnormal head development and schizophrenia-relevant behaviors in mice

Mutations in the Opo gene result in eye malformation in medaka fish. The human ortholog of this gene, MRDS1/OFCC1, is a potentially causal gene for orofacial cleft, as well as a susceptibility gene for schizophrenia, a devastating mental illness. Based on this evidence, we hypothesized that this gene could perform crucial functions in the development of head and brain structures in vertebrates. To test this hypothesis, we created Mrds1/Ofcc1-null mice. Mice were examined thoroughly using an abnormality screening system referred to as "the Japan Mouse Clinic". No malformations of the head structure, eye or other parts of the body were apparent in these knockout mice. However, the mutant mice showed a marked increase in serum γ-glutamyl transpeptidase (GGT), a marker for liver damage, but no abnormalities in other liver-related measurements. We also performed a family-based association study on the gene in schizophrenia samples of Japanese origin. We found five single nucleotide polymorphisms (SNPs) located across the gene that showed significant transmission distortion, supporting a prior report of association in a Caucasian cohort. However, the knockout mice showed no behavioral phenotypes relevant to schizophrenia. In conclusion, disruption of the Mrds1/Ofcc1 gene elicits asymptomatic hyper-γ-glutamyl-transpeptidasemia in mice. However, there were no phenotypes to support a role for the gene in the development of eye and craniofacial structures in vertebrates. These results prompt further examination of the gene, including its putative contribution to hyper-γ-glutamyl transpeptidasemia and schizophrenia.

Effects of DTNBP1 genotype on brain development in children

BACKGROUND

Schizophrenia is a neurodevelopmental disorder, and risk genes are thought to act through disruption of brain development. Several genetic studies have identified dystrobrevin-binding protein 1 (DTNBP1, also known as dysbindin) as a potential susceptibility gene for schizophrenia, but its impact on brain development is poorly understood. The present investigation examined for the first time the effects of DTNBP1 on brain structure in children. Our hypothesis was that a genetic variation in DTNBP1 (i.e., the single nucleotide polymorphism rs2619538) would be associated with differences in both gray and white matter brain regions previously implicated in schizophrenia.

METHODS

Magnetic resonance imaging and voxel-based morphometry were used to examine brain structure in 52 male children aged between 10 and 12 years. Statistical inferences on the effects of DTNBP1 genotype on gray and white matter volume (GMV and WMV) were made at p < .05 after family-wise error correction for multiple comparisons across the whole brain.

RESULTS

Individuals homozygous for the schizophrenia high-risk allele (AA) compared with those homozygous for the low-risk allele (TT) expressed reduced GMV in the left anterior cingulate gyrus and reduced WMV in the left medial frontal area.

CONCLUSIONS

Our results suggest that genetic variation in DTNBP1 is associated with differences in gray and white matter; and that these effects are already evident in children as young as 10-12 years. These findings are consistent with the notion that the DTNBP1 genotype influences brain development and may thereby modulate vulnerability to schizophrenia.

GWA study data mining and independent replication identify cardiomyopathy-associated 5 (CMYA5) as a risk gene for schizophrenia

We conducted data-mining analyses using the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) and molecular genetics of schizophrenia genome-wide association study supported by the genetic association information network (MGS-GAIN) schizophrenia data sets and performed bioinformatic prioritization for all the markers with P-values ≤0.05 in both data sets. In this process, we found that in the CMYA5 gene, there were two non-synonymous markers, rs3828611 and rs10043986, showing nominal significance in both the CATIE and MGS-GAIN samples. In a combined analysis of both the CATIE and MGS-GAIN samples, rs4704591 was identified as the most significant marker in the gene. Linkage disequilibrium analyses indicated that these markers were in low LD (3 828 611-rs10043986, r(2)=0.008; rs10043986-rs4704591, r(2)=0.204). In addition, CMYA5 was reported to be physically interacting with the DTNBP1 gene, a promising candidate for schizophrenia, suggesting that CMYA5 may be involved in the same biological pathway and process. On the basis of this information, we performed replication studies for these three single-nucleotide polymorphisms. The rs3828611 was found to have conflicting results in our Irish samples and was dropped out without further investigation. The other two markers were verified in 23 other independent data sets. In a meta-analysis of all 23 replication samples (family samples, 912 families with 4160 subjects; case-control samples, 11 380 cases and 15 021 controls), we found that both markers are significantly associated with schizophrenia (rs10043986, odds ratio (OR)=1.11, 95% confidence interval (CI)=1.04-1.18, P=8.2 × 10(-4) and rs4704591, OR=1.07, 95% CI=1.03-1.11, P=3.0 × 10(-4)). The results were also significant for the 22 Caucasian replication samples (rs10043986, OR=1.11, 95% CI=1.03-1.17, P=0.0026 and rs4704591, OR=1.07, 95% CI=1.02-1.11, P=0.0015). Furthermore, haplotype conditioned analyses indicated that the association signals observed at these two markers are independent. On the basis of these results, we concluded that CMYA5 is associated with schizophrenia and further investigation of the gene is warranted.

Dystrobrevin-binding protein 1 gene (DTNBP1) variants associated with cerebrospinal fluid homovanillic acid and 5-hydroxyindoleacetic acid concentrations in healthy volunteers

The dystrobrevin binding protein-1 (DTNBP1) gene encodes dysbindin-1, a protein involved in neurodevelopmental and neurochemical processes related mainly to the monoamine dopamine. We investigated possible associations between eleven DTNBP1 polymorphisms and cerebrospinal fluid (CSF) concentrations of the major dopamine metabolite homovanillic acid (HVA), the major serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA), and the major noradrenaline metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) in healthy human subjects (n=132). Two polymorphisms, rs2619538 and rs760666, were nominally associated with CSF HVA and 5-HIAA concentrations, whereas a third polymorphism, rs909706, showed association only with HVA. After correction for multiple testing only the associations between rs2619538 and HVA and 5-HIAA concentrations remained significant. No significant association was found between any of the investigated DTNBP1 polymorphisms and CSF MHPG concentrations. The results suggest that genetic variation in DTNBP1 gene affects the regulation of dopamine and serotonin turnover in the central nervous system of healthy volunteers.

Cell biology of the BLOC-1 complex subunit dysbindin, a schizophrenia susceptibility gene

There is growing interest in the biology of dysbindin and its genetic locus (DTNBP1) due to genetic variants associated with an increased risk of schizophrenia. Reduced levels of dysbindin mRNA and protein in the hippocampal formation of schizophrenia patients further support involvement of this locus in disease risk. Here, we discuss phylogenetically conserved dysbindin molecular interactions that define its contribution to the assembly of the biogenesis of lysosome-related organelles complex-1 (BLOC-1). We explore fundamental cellular processes where dysbindin and the dysbindin-containing BLOC-1 complex are implicated. We propose that cellular, tissue, and system neurological phenotypes from dysbindin deficiencies in model genetic organisms, and likely individuals affected with schizophrenia, emerge from abnormalities in few core cellular mechanisms controlled by BLOC-1-dysbindin-containing complex rather than from defects in dysbindin itself.

Pharmacogenetic approaches to cognitive enhancement in schizophrenia

Research in the area of pharmacogenetics in psychiatry is aimed at identifying clinically relevant genetic variations that can predict treatment response. Ultimately, the goal is to individualize treatment in order to optimize outcome in disorders in which incomplete treatment response is common. Positive symptoms in patients with schizophrenia appear to be the most amenable to the currently available agents; however, negative symptoms and cognitive deficits frequently persist even when frank psychosis is well controlled. Given the relationship between these persistent traits and functional disability in schizophrenia, efforts are under way to directly target cognitive impairment and negative symptoms pharmacologically in order to improve quality of life. To date, most pharmacogenetic studies of schizophrenia have been focused on predicting clinical efficacy and side effects. In this review, we discuss the potential use of cognition as a primary outcome measure of interest in future pharmacogenetic trials of schizophrenia.

Dysbindin (DTNBP1)--a role in psychotic depression?

Previous studies yielded evidence for dysbindin (DTNBP1) to impact the pathogenesis of schizophrenia on the one hand and affective disorders such as bipolar or major depressive disorder (MDD) on the other. Thus, in the present study we investigated whether DTNBP1 variation was associated with psychotic depression as a severe clinical manifestation of MDD possibly constituting an overlapping phenotype between affective disorders and schizophrenia. A sample of 243 Caucasian inpatients with MDD (SCID-I) was genotyped for 12 SNPs spanning 92% of the DTNBP1 gene region. Differences in DTNBP1 genotype distributions across diagnostic subgroups of psychotic (N = 131) vs. non-psychotic depression were estimated by Pearson Chi(2) test and logistic regression analyses adjusted for age, gender, Beck Depression Inventory (BDI) and the Global Assessment of Functioning Scale (GAF). Overall, patients with psychotic depression presented with higher BDI and lower GAF scores expressing a higher severity of the illness as compared to depressed patients without psychotic features. Four DTNBP1 SNPs, particularly rs1997679 and rs9370822, and the corresponding haplotypes, respectively, were found to be significantly associated with the risk of psychotic depression in an allele-dose fashion. In summary, the present results provide preliminary support for dysbindin (DTNBP1) gene variation, particularly SNPs rs1997679 and rs9370822, to be associated with the clinical phenotype of psychotic depression suggesting a possible neurobiological mechanism for an intermediate trait on the continuum between affective disorders and schizophrenia.

The first decade and beyond of transcriptional profiling in schizophrenia

Gene expression changes in brains of individuals with schizophrenia (SZ) have been hypothesized to reflect possible pathways related to pathophysiology and/or medication. Other factors having robust effects on gene expression profiling in brain and possibly influence the schizophrenia transcriptome such as age and pH are examined. Pathways of curated gene expression or gene correlation networks reported in SZ (white matter, apoptosis, neurogenesis, synaptic plasticity, glutamatergic and GABAergic neurotransmission, immune and stress-response, mitochondrial, and neurodevelopment) are not unique to SZ and have been associated with other psychiatric disorders. Suggestions going forward to improve the next decade of profiling: consider multiple brain regions that are carefully dissected, release large datasets from multiple brain regions in controls to better understand neurocircuitry, integrate genetics and gene expression, measure expression variants on genome wide level, peripheral biomarker studies, and analyze the transcriptome across a developmental series of brains. Gene expression, while an important feature of the genomic landscape, requires further systems biology to advance from control brains to a more precise definition of the schizophrenia interactome.

Dysbindin-1 genotype effects on emotional working memory

We combined functional imaging and genetics to investigate the behavioral and neural effects of a dysbindin-1 (DTNBP1) genotype associated with the expression level of this important synaptic protein, which has been implicated in schizophrenia. On a working memory (WM) task for emotional faces, participants with the genotype related to increased expression showed higher WM capacity for happy faces compared with the genotype related to lower expression. Activity in several task-related brain areas with known DTNBP1 expression was increased, including hippocampal, temporal and frontal cortex. Although these increases occurred across emotions, they were mostly observed in areas whose activity correlated with performance for happy faces. This suggests effects of variability in DTNBP1 on emotion-specific WM capacity and region-specific task-related brain activation in humans. Synaptic effects of DTNBP1 implicate that altered dopaminergic and/or glutamatergic neurotransmission may be related to the increased WM capacity. The combination of imaging and genetics thus allows us to bridge the gap between the cellular/molecular and systems/behavioral level and extend the cognitive neuroscience approach to a comprehensive biology of cognition.

Neuroplasticity signaling pathways linked to the pathophysiology of schizophrenia

Schizophrenia is a severe mental illness that afflicts nearly 1% of the world's population. One of the cardinal pathological features of schizophrenia is perturbation in synaptic connectivity. Although the etiology of schizophrenia is unknown, it appears to be a developmental disorder involving the interaction of a potentially large number of risk genes, with no one gene producing a strong effect except rare, highly penetrant copy number variants. The purpose of this review is to detail how putative schizophrenia risk genes (DISC-1, neuregulin/ErbB4, dysbindin, Akt1, BDNF, and the NMDA receptor) are involved in regulating neuroplasticity and how alterations in their expression may contribute to the disconnectivity observed in schizophrenia. Moreover, this review highlights how many of these risk genes converge to regulate common neurotransmitter systems and signaling pathways. Future studies aimed at elucidating the functions of these risk genes will provide new insights into the pathophysiology of schizophrenia and will likely lead to the nomination of novel therapeutic targets for restoring proper synaptic connectivity in the brain in schizophrenia and related disorders.

Nucleocytoplasmic shuttling of dysbindin-1, a schizophrenia-related protein, regulates synapsin I expression

Dysbindin-1 is a 50-kDa coiled-coil-containing protein encoded by the gene DTNBP1 (dystrobrevin-binding protein 1), a candidate genetic factor for schizophrenia. Genetic variations in this gene confer a susceptibility to schizophrenia through a decreased expression of dysbindin-1. It was reported that dysbindin-1 regulates the expression of presynaptic proteins and the release of neurotransmitters. However, the precise functions of dysbindin-1 are largely unknown. Here, we show that dysbindin-1 is a novel nucleocytoplasmic shuttling protein and translocated to the nucleus upon treatment with leptomycin B, an inhibitor of exportin-1/CRM1-mediated nuclear export. Dysbindin-1 harbors a functional nuclear export signal necessary for its nuclear export, and the nucleocytoplasmic shuttling of dysbindin-1 affects its regulation of synapsin I expression. In brains of sandy mice, a dysbindin-1-null strain that displays abnormal behaviors related to schizophrenia, the protein and mRNA levels of synapsin I are decreased. These findings demonstrate that the nucleocytoplasmic shuttling of dysbindin-1 regulates synapsin I expression and thus may be involved in the pathogenesis of schizophrenia.

Dysbindin-1, WAVE2 and Abi-1 form a complex that regulates dendritic spine formation

Genetic variations in dysbindin-1 (dystrobrevin-binding protein-1) are one of the most commonly reported variations associated with schizophrenia. As schizophrenia could be regarded as a neurodevelopmental disorder resulting from abnormalities of synaptic connectivity, we attempted to clarify the function of dysbindin-1 in neuronal development. We examined the developmental change of dysbindin-1 in rat brain by western blotting and found that a 50 kDa isoform is highly expressed during the embryonic stage, whereas a 40 kDa one is detected at postnatal day 11 and increased thereafter. Immunofluorescent analyses revealed that dysbindin-1 is enriched at the spine-like structure of primary cultured rat hippocampal neurons. We identified WAVE2, but not N-WASP, as a binding partner for dysbindin-1. We also found that Abi-1, a binding molecule for WAVE2 involved in spine morphogenesis, interacts with dysbindin-1. Although dysbindin-1, WAVE2 and Abi-1 form a ternary complex, dysbindin-1 promoted the binding of WAVE2 to Abi-1. RNA interference-mediated knockdown of dysbindin-1 led to the generation of abnormally elongated immature dendritic protrusions. The present results indicate possible functions of dysbindin-1 at the postsynapse in the regulation of dendritic spine morphogenesis through the interaction with WAVE2 and Abi-1.

DTNBP1 gene is associated with some symptom factors of schizophrenia in Chinese Han nationality

OBJECTIVE

To study the association of DTNBP1 gene with some symptom factors of schizophrenia.

METHODS

A total of 285 unrelated schizophrenic individuals were recruited from December 2004 to January 2009 for genetic analysis, and their symptom factors were assessed based on the Positive and Negative Syndrome Scale (PANSS). The quantitative trait test was performed by the UNPHASED program (version 3.0.12) to investigate the association between scored positive and negative symptoms and the single nucleotide polymorphisms (SNPs) in DTNBP1 gene.

RESULTS

The quantitative trait test showed allelic association of rs909706 with the excitement symptom of schizophrenia (P<0.05, adjusted by 10,000 permutations), while the genotype C/G of rs2619539 with a negative symptom, lack of spontaneity and flow of conversation (P<0.05, adjusted by 10,000 permutations).

CONCLUSION

DTNBP1 variations are possibly associated with some symptoms of schizophrenia, which could partly explain the relationship between the susceptibility gene DTNBP1 and that disease.

Analysis of HapMap tag-SNPs in dysbindin (DTNBP1) reveals evidence of consistent association with schizophrenia

Dystrobrevin binding protein 1 (DTNBP1), or dysbindin, is thought to be critical in regulating the glutamatergic system. While the dopamine pathway is known to be important in the aetiology of schizophrenia, it seems likely that glutamatergic dysfunction can lead to the development of schizophrenia. DTNBP1 is widely expressed in brain, levels are reduced in brains of schizophrenia patients and a DTNBP1 polymorphism has been associated with reduced brain expression. Despite numerous genetic studies no DTNBP1 polymorphism has been strongly implicated in schizophrenia aetiology. Using a haplotype block-based gene-tagging approach we genotyped 13 SNPs in DTNBP1 to investigate possible associations with DTNBP1 and schizophrenia. Four polymorphisms were found to be significantly associated with schizophrenia. The strongest association was found with an A/C SNP in intron 7 (rs9370822). Homozygotes for the C allele of rs9370822 were more than two and a half times as likely to have schizophrenia compared to controls. The other polymorphisms showed much weaker association and are less likely to be biologically significant. These results suggest that DTNBP1 is a good candidate for schizophrenia risk and rs9370822 is either functionally important or in disequilibrium with a functional SNP, although our observations should be viewed with caution until they are independently replicated.

A reappraisal of the association between Dysbindin (DTNBP1) and schizophrenia in a large combined case-control and family-based sample of German ancestry

BACKGROUND

Dysbindin (DTNBP1) is a widely studied candidate gene for schizophrenia (SCZ); however, inconsistent results across studies triggered skepticism towards the validity of the findings. In this HapMap-based study, we reappraised the association between Dysbindin and SCZ in a large sample of German ethnicity.

METHOD

Six hundred thirty-four cases with DSM-IV SCZ, 776 controls, and 180 parent-offspring trios were genotyped for 38 Dysbindin SNPs. We also studied two phenotypically-defined subsamples: 147 patients with a positive family history of SCZ (FH-SCZ+) and SCZ patients characterized for cognitive performance with Trail-Making Tests A and B (TMT-A: n=219; TMT-B: n=247). Given previous evidence of gene-gene interactions in SCZ involving the COMT gene, we also assessed epistatic interactions between Dysbindin markers and 14 SNPs in COMT.

RESULTS

No association was detected between Dysbindin markers and SCZ, or in the FH-SCZ+ subgroup. Only one marker (rs1047631, previously reported to be part of a risk haplotype), showed a nominally significant association with performance on TMT-A and TMT-B; these findings did not remain significant after correction for multiple comparisons. Similarly, no pair-wise epistatic interactions between Dysbindin and COMT markers remained significant after correction for 504 pair-wise comparisons.

CONCLUSIONS

Our results, based on one of the largest samples of European Caucasians and using narrowly-defined criteria for SCZ, do not support the etiological involvement of Dysbindin markers in SCZ. Larger samples may be needed in order to unravel Dysbindin's possible role in the genetic basis of proposed intermediate phenotypes of SCZ or to detect epistatic interactions.

Genetics and intermediate phenotypes of the schizophrenia--bipolar disorder boundary

Categorization of psychotic illnesses into schizophrenic and affective psychoses remains an ongoing controversy. Although Kraepelinian subtyping of psychosis was historically beneficial, modern genetic and neurophysiological studies do not support dichotomous conceptualization of psychosis. Evidence suggests that schizophrenia and bipolar disorder rather present a clinical continuum with partially overlapping symptom dimensions, neurophysiology, genetics and treatment responses. Recent large scale genetic studies have produced inconsistent findings and exposed an urgent need for re-thinking phenomenology-based approach in psychiatric research. Epidemiological, linkage and molecular genetic studies, as well as studies in intermediate phenotypes (neurocognitive, neurophysiological and anatomical imaging) in schizophrenia and bipolar disorders are reviewed in order to support a dimensional conceptualization of psychosis. Overlapping and unique genetic and intermediate phenotypic signatures of the two psychoses are comprehensively recapitulated. Alternative strategies which may be implicated into genetic research are discussed.

Nature and nurture in neuropsychiatric genetics: where do we stand?

Both genetic and nongenetic risk factors, as well as interactions and correlations between them, are thought to contribute to the etiology of psychiatric and behavioral phenotypes. Genetic epidemiology consistently supports the involvement of genes in liability. Molecular genetic studies have been less successful in identifying liability genes, but recent progress suggests that a number of specific genes contributing to risk have been identified. Collectively, the results are complex and inconsistent, with a single common DNA variant in any gene influencing risk across human populations. Few specific genetic variants influencing risk have been unambiguously identified. Contemporary approaches, however, hold great promise to further elucidate liability genes and variants, as well as their potential inter-relationships with each other and with the environment. We will review the fields of genetic epidemiology and molecular genetics, providing examples from the literature to illustrate the key concepts emerging from this work.

Mutation screening of the DTNBP1 exonic sequence in 669 schizophrenics and 710 controls using high-resolution melting analysis

A large number of independent studies have reported evidence for association between the dysbindin gene (DTNBP1) and schizophrenia; however, specific risk alleles have been not been implicated as causal. In this study we set out to perform a comprehensive assessment of DNA variation within the exonic sequence of DTNBP1. To achieve this we optimized a high-resolution melting analysis (HRMA) protocol and applied it to screen all 11 DTNBP1 exons for DNA variants in a sample of 669 cases and 710 controls from the UK. Despite identifying seven exonic variants with a minor allele frequency (MAF) >0.01, none was significantly associated with schizophrenia (minimum P = 0.054), showing that the strong association we previously reported in this sample is not the result of association to a common functional variant located within the exonic sequence of any of the three major DTNBP1 transcripts. We also sought additional support for DTNBP1 as a susceptibility gene for schizophrenia by testing the hypothesis that rare exonic highly penetrant variants exist at the DTNBP1 locus. Our analysis failed to identify an enrichment of rare functional variants in the patients compared to the controls. Taken as a whole, this data demonstrate that if DTNBP1 is a risk gene for schizophrenia then risk is not conferred by mutations that affect the structure of the dysbindin protein.

Cytosolic protein interactions of the schizophrenia susceptibility gene dysbindin

Using immunoprecipitation, mass spectrometry, and western blot analysis we investigated cytosolic protein interactions of the schizophrenia susceptibility gene dysbindin in mammalian cells. We identified novel interactions with members of the exocyst, dynactin and chaperonin containing T-complex protein complexes, and we confirmed interactions reported previously with all members of the biogenesis of lysosome-related organelles complex-1 and the adaptor-related protein complex 3. We report interactions between dysbindin and the exocyst and dynactin complex that confirm a link between two important schizophrenia susceptibility genes: dysbindin and disrupted-in-schizophrenia-1. To expand upon this network of interacting proteins we also investigated protein interactions for members of the exocyst and dynactin complexes in mammalian cells. Our results are consistent with the notion that impairment of aspects of the synaptic vesicle life cycle may be a pathogenic mechanism in schizophrenia.

No association of dysbindin with symptom factors of schizophrenia in an Irish case-control sample

Robust associations between the dysbindin gene (DTNBP1) and schizophrenia have been demonstrated in many but not all samples, and evidence that this gene particularly predisposes to negative symptoms in this illness has been presented. The current study sought to replicate the previously reported negative symptom associations in an Irish case-control sample. Association between dysbindin and schizophrenia has been established in this cohort, and a factor analysis of the assessed symptoms yielded three factors, Positive, Negative, and Schneiderian. The sequential addition method was applied using UNPHASED to assess the relationship between these symptom factors and the high-risk haplotype. No associations were detected for any of the symptom factors indicating that the dysbindin risk haplotype does not predispose to a particular group of symptoms in this sample. Several possibilities, such as differing risk haplotypes, may explain this finding.

DTNBP1 (dysbindin) gene variants modulate prefrontal brain function in schizophrenic patients--support for the glutamate hypothesis of schizophrenias

Dysbindin (DTNBP1) is a recently characterized protein that seems to be involved in the modulation of glutamatergic neurotransmission in the human brain, thereby influencing prefrontal cortex function and associated cognitive processes. While association, neuroanatomical and cellular studies indicate that DTNBP1 might be one of several susceptibility genes for schizophrenia, the effect of dysbindin on prefrontal brain function at an underlying neurophysiological level has not yet been explored for these patients. The NoGo-anteriorization (NGA) is a topographical event-related potential measure, which has been established as a valid neurophysiological marker of prefrontal brain function. In the present study, we investigated the influence of seven dysbindin gene variants on the NGA in a group of 44 schizophrenic patients. In line with our a priori hypothesis, one DTNBP1 polymorphism previously linked to schizophrenia (rs2619528) was found to be associated with changes in the NGA; however, the direction of this association directly contrasts with our previous findings in a healthy control sample. This differential impact of DTNBP1 gene variation on prefrontal functioning in schizophrenic patients vs. healthy controls is discussed in terms of abnormal glutamatergic baseline levels in patients suffering from schizophrenic illnesses. This is the first report on a role of DTNBP1 gene variation for prefrontal functioning at a basic neurophysiological level in schizophrenic patients. An impact on fundamental processes of cognitive response control may be one mechanism by which DTNBP1 gene variants via glutamatergic transmission contribute to the pathophysiology underlying schizophrenic illnesses.

Dysbindin regulates the transcriptional level of myristoylated alanine-rich protein kinase C substrate via the interaction with NF-YB in mice brain

Background

An accumulating body of evidence suggests that Dtnbp1 (Dysbindin) is a key susceptibility gene for schizophrenia. Using the yeast-two-hybrid screening system, we examined the candidate proteins interacting with Dysbindin and revealed one of these candidates to be the transcription factor NF-YB.

Methods

We employed an immunoprecipitation (IP) assay to demonstrate the Dysbindin-NF-YB interaction. DNA chips were used to screen for altered expression of genes in cells in which Dysbindin or NF-YB was down regulated, while Chromatin IP and Reporter assays were used to confirm the involvement of these genes in transcription of Myristoylated alanine-rich protein kinase C substrate (MARCKS). The sdy mutant mice with a deletion in Dysbindin, which exhibit behavioral abnormalities, and wild-type DBA2J mice were used to investigate MARCKS expression.

Results

We revealed an interaction between Dysbindin and NF-YB. DNA chips showed that MARCKS expression was increased in both Dysbindin knockdown cells and NF-YB knockdown cells, and Chromatin IP revealed interaction of these proteins at the MARCKS promoter region. Reporter assay results suggested functional involvement of the interaction between Dysbindin and NF-YB in MARCKS transcription levels, via the CCAAT motif which is a NF-YB binding sequence. MARCKS expression was increased in sdy mutant mice when compared to wild-type mice.

Conclusions

These findings suggest that abnormal expression of MARCKS via dysfunction of Dysbindin might cause impairment of neural transmission and abnormal synaptogenesis. Our results should provide new insights into the mechanisms of neuronal development and the pathogenesis of schizophrenia.

Association study of DTNBP1 with schizophrenia in a US sample

BACKGROUND

Straub et al. (2002b) located a susceptibility region for schizophrenia at the DTNBP1 locus. At least 40 studies (including one study in US populations) attempted to replicate this original finding, but the reported findings are highly diverse and at least five pathways by which dysbindin protein might be involved in schizophrenia have been proposed. This study aimed to test the association in two common US populations by using powerful analytic methods.

METHODS

Six markers at DTNBP1 were genotyped by mass spectroscopy ('MassARRAY' technique) in a sample of 663 individuals, including 346 healthy individuals European-Americans (EAs) and 48 African-Americans (AAs), and 317 individuals with schizophrenia (235 EAs and 82 AAs). Thirty-eight ancestry-informative markers were genotyped in this sample to infer the ancestry proportions. Diplotype, haplotype, genotype, and allele frequency distributions were compared between the cases and controls, controlling for possible population stratification, admixture, and sex-specific effects, and taking interaction effects into account, using a logistic regression analysis (an extended structured association method).

RESULTS

Conventional case-control comparisons showed that genotypes of the markers P1578 (rs1018381) and P1583 (rs909706) were nominally associated with schizophrenia in EAs and in AAs, respectively. These associations became less or nonsignificant after controlling for population stratification and admixture effects (using structured association or regression analysis), and became nonsignificant after correction for multiple testing. However, regression analysis showed that the common diplotypes (ACCCTT/GCCGCC or GCCGCC/GCCGCC) and the interaction effects of haplotypes GCCGCC/GCCGCC significantly affected risk for schizophrenia in EAs, effects that were modified by sex. Fine-mapping using d or J statistics located the specific markers (d: P1328; J: P1333) closest to the putative risk sites in EAs.

CONCLUSION

This study shows that DTNBP1 is a risk gene for schizophrenia in EAs. Variation at DTNBP1 may modify risk for schizophrenia in this population.

DTNBP1 is associated with imaging phenotypes in schizophrenia

Dystrobrevin binding protein 1 (DTNBP1) has been identified as putative schizophrenia susceptibility gene, but it remains unknown whether polymorphisms relate to altered cerebral structure. We examined relationships between a previously implicated DTNBP1 risk variant [P1578] and global and segmented brain tissue volumes and regional cortical thickness in schizophrenia (n = 62; 24 risk carriers) and healthy subjects (n = 42; 11 risk carriers), across ethnic groups and within Caucasians. Schizophrenia patients showed similar brain volumes, but significantly reduced brain-size adjusted gray matter and CSF volumes and cortical thinning in a widespread neocortical distribution compared to controls. DTNBP1 risk was found associated with reduced brain volume, but not with tissue sub-compartments. Cortical thickness, which was weakly associated with brain size, showed regional variations in association with genetic risk, although effects were dominated by highly significant genotype by diagnosis interactions over broad areas of cortex. Risk status was found associated with regional cortical thinning in patients, particularly in temporal networks, but with thickness increases in controls. DTNBP1 effects for brain volume and cortical thickness appear driven by different neurobiological processes. Smaller brain volumes observed in risk carriers may relate to previously reported DTNBP1/cognitive function relationships irrespective of diagnosis. Regional cortical thinning in patient, but not in control risk carriers, may suggest that DTNBP1 interacts with other schizophrenia-related risk factors to affect laminar thickness. Alternatively, DTNBP1 may influence neural processes for which individuals with thicker cortex are less vulnerable. Although DTNBP1 relates to cortical thinning in schizophrenia, morphological changes in the disorder are influenced by additional genetic and/or environmental factors.

Reduced occipital and prefrontal brain volumes in dysbindin-associated schizophrenia

A three-marker C-A-T dysbindin haplotype identified by Williams et al (PMID: 15066891) is associated with increased risk for schizophrenia, decreased mRNA expression, poorer cognitive performance, and early sensory processing deficits. We investigated whether this same dysbindin risk haplotype was also associated with structural variation in the gray matter volume (GMV). Using voxel-based morphometry, whole-volume analysis revealed significantly reduced GMVs in both the right dorsolateral prefrontal and left occipital cortex, corresponding to the behavioral findings of impaired spatial working memory and EEG findings of impaired visual processing already reported. These data provide important evidence of the influence of dysbindin risk variants on brain structure, and suggest a possible mechanism by which disease risk is being increased.

The dystrobrevin binding protein 1 (DTNBP1) gene is associated with schizophrenia in the Irish Case Control Study of Schizophrenia (ICCSS) sample

BACKGROUND

DTNBP1 is associated with schizophrenia in many studies, but the associated alleles and haplotypes vary between samples.

METHOD

We assessed nine single nucleotide polymorphisms (SNPs) in this gene for association with schizophrenia in a new sample of 1021 cases and 626 controls from Ireland.

RESULTS

Four SNPs give evidence of association (0.000018<p<0.045), most strongly with the common allele at rs760761. A haplotype of the common alleles of five markers (including rs760761) and the minor allele of rs2619538 overlapping the 5' end of the DTNBP1 gene also gives evidence for association (p=0.0002). Secondary analyses showed no difference in the association signal based on sex or family history. These results are in agreement with the most consistently observed association with common alleles and common-allele haplotypes, reported in a previous study of Irish cases and controls but not in an Irish high-density family sample. Our results do not support the prior report from a Swedish sample of increased association in cases with a family history of psychotic illness. Comparison of human, chimpanzee and rhesus sequence suggest that rs760761 is a particularly variable position in the primate lineage.

CONCLUSION

This study provides further evidence from a large case/control sample for association of common DTNBP1 alleles and haplotypes with schizophrenia.

Whole genome association study in a homogenous population in Shandong peninsula of China reveals JARID2 as a susceptibility gene for schizophrenia

DNA pooling can provide an economic and efficient way to detect susceptibility loci to complex diseases. We carried out a genome screen with 400 microsatellite markers spaced at approximately 10 cm in two DNA pools consisting of 119 schizophrenia (SZ) patients and 119 controls recruited from a homogenous population in the Chang Le area of the Shandong peninsula of China. Association of D6S289, a dinucleotide repeat polymorphism in the JARID2 gene with SZ, was found and confirmed by individual genotyping (X² = 17.89; P = .047). In order to refine the signal, we genotyped 14 single nucleotide polymorphisms (SNPs) covering JARID2 and the neighboring gene, DNTBP1, in an extended sample of 309 cases and 309 controls from Shandong peninsula (including the samples from the pools). However, rs2235258 and rs9654600 in JARID2 showed association in allelic, genotypic and haplotypic tests with SZ patients from Chang Le area. This was not replicates in the extended sample, we conclude that JARID2 could be a susceptibility gene for SZ.

Association of the dystrobrevin binding protein 1 gene (DTNBP1) in a bipolar case-control study (BACCS)

Recent studies suggest a degree of overlap in genetic susceptibility across the traditional categories of schizophrenia and bipolar disorder. There is some evidence for an association of the dystrobrevin binding protein 1 gene (DTNBP1) with schizophrenia, and, thus, this gene has also become a focus of further investigation in bipolar disorder (BD). The aim of our study is to explore the association of DTNBP1 with BD and with a sub phenotype, presence/absence of psychotic symptoms, in a sample of 515 patients with BD (ICD10/DSMIV) and 1,316 ethnically matched control subjects recruited from the UK. Seven DTNBP1 SNPs: rs2743852 (SNP C), rs760761 (P1320), rs1011313 (P1325), rs3213207 (P1635), rs2619539 (P1655), rs16876571 and rs17470454 were investigated using the SNPlex genotyping system and 1 SNP (rs2619522) genotypes were imputed. Association analyses were conducted in a sample of 452 cases and 956 controls. We found significant differences in genotypic and allelic frequencies of rs3213207 and rs760761 of DTNBP1 between bipolar patients and controls. We also showed a global haplotypic association and an association of a particular haplotype with BD. Our results are consistent with previous studies in term of a general association between DTNBP1 and bipolar disorder and provide additional evidence that a portion of the genotypic overlap between schizophrenia and bipolar affective disorder is attributable to this gene.