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

G72 gene is associated with susceptibility to methamphetamine psychosis

Methamphetamine psychosis is considered as one of the pharmacological models of schizophrenia, and a hyperdopaminergic one. However, many lines of experimental evidence indicate that glutamatergic signaling is also involved in development of methamphetamine psychosis. Several genes related to glutamate function, e.g. the DTNBP1, G72, and GRM3 genes, were shown to be associated with schizophrenia susceptibility. Recently, we found significant association of the DTNBP1 gene with methamphetamine psychosis. This finding prompted us to examine the G72 gene encoding the d-amino acid oxidase activator (DAOA), which metabolizes d-serine, an NMDA co-agonist, in methamphetamine psychosis. Six SNPs of the G72 gene, which previously showed significant association with schizophrenia, were analyzed in 209 patients with methamphetamine psychosis and 291 age- and sex-matched normal controls. One SNP of M22 (rs778293) showed a significant association with methamphetamine psychosis (genotype: p=0.00016, allele: p=0.0015). Two haplotypes G-A of M12 (rs3916965)-M15 (rs2391191) (p=0.00024) and T-T of M23 (rs947267)-M24 (rs1421292) (p=0.00085) also showed associations with methamphetamine psychosis. The present findings suggest that the G72 gene may contribute to a predisposition to not only schizophrenia but also to methamphetamine psychosis.

Association between the dysbindin gene (DTNBP1) and cognitive functions in Japanese subjects

AIM

The dysbindin gene (dystrobrevin binding protein 1: DTNBP1) is a susceptibility gene for schizophrenia. Susceptibility genes for schizophrenia have been hypothesized to mediate liability for the disorder at least partly by influencing cognitive performance. This report investigated the relationship between cognitive function and the dysbindin gene.

METHODS

The possible association between a single nucleotide polymorphism (SNP) of DTNBP1 (rs2619539: P1655), which is a risk-independent SNP for schizophrenia in Japanese populations, and memory and IQ was investigated in 70 schizophrenia patients and 165 healthy volunteers in a Japanese population.

RESULTS

This SNP was associated with two memory scales, verbal memory and general memory, on the Wechsler Memory Scale-Revised (WMS-R), and three subcategories of the Wechsler Adult Intelligence Scale-Revised (WAIS-R), vocabulary, similarities and picture completion in healthy subjects. The SNP, however, did not influence either the indices of WMS-R, IQ or subcategories of WAIS-R in schizophrenia patients.

CONCLUSION

A risk-independent SNP in DTNBP1 may have an impact on cognitive functions such as memory and IQ in healthy subjects.

Dysbindin modulates brain function during visual processing in children

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 function is poorly understood. It has been proposed that DTNBP1 may be associated with differences in visual processing. To test this, we examined the impact on visual processing in 61 healthy children aged 10-12 years of a genetic variant in DTNBP1 (rs2619538) that was common to all schizophrenia associated haplotypes in an earlier UK-Irish study. We tested the hypothesis that carriers of the risk allele would show altered occipital cortical function relative to noncarriers. Functional Magnetic Resonance Imaging (fMRI) was used to measure brain responses during a visual matching task. The data were analysed using statistical parametric mapping and statistical inferences were made at p<0.05 (corrected for multiple comparisons). Relative to noncarriers, carriers of the risk allele had greater activation in the lingual, fusiform gyrus and inferior occipital gyri. In these regions DTNBP1 genotype accounted for 19%, 20% and 14% of the inter-individual variance, respectively. Our results suggest that that genetic variation in DTNBP1 is associated with differences in the function of brain areas that mediate visual processing, and that these effects are evident in young children. These findings are consistent with the notion that the DTNBP1 gene influences brain development and can thereby modulate vulnerability to schizophrenia.

Fine mapping and association studies in a candidate region for autism on chromosome 2q31-q32

Autism (OMIM %209850) is a neurodevelopmental disorder with a strong genetic component. We previously reported a de novo rearrangement of chromosome 2q31 in a patient with autism [Gallagher et al. (2003); J Autism Dev Disord 33(1):105-108]. Further cytogenetic analysis revealed this to be a 46,XY, t(9;2)(q31.1;q32.2q31.3) translocation. Association mapping with microsatellite and SNP markers of this translocated region on 2q revealed association with markers in Integrin alpha-4 (ITGA4; GeneID 3676). ITGA4 was tested for association in a sample of 179 trio-based families. SNP markers in exons 16 and 17 showed evidence of association. Mutation screening revealed a G to A synonymous variation in the last nucleotide of exon 16 (rs12690517), significantly associated with autism in the Irish sample (OR = 1.6; P = 0.04). The location of this SNP at a putative splice donor site may affect the splicing of the ITGA4 protein. Haplotype analysis showed significant overtransmission of haplotypes surrounding this marker. These markers were investigated in two additional samples, 102 families from Vanderbilt University (VT) (n = 102), and AGRE (n = 267). A non-significant trend towards overtransmission of the associated allele of rs12690517 in the Irish sample (OR = 1.2; P = 0.067) and haplotypes at the 3' end of ITGA4 was observed in the AGRE sample. The VT sample showed association with markers and haplotypes across the gene, but no association with the rs12690517 marker or its surrounding haplotypes. The combined sample showed evidence of association with rs12690517 (OR = 1.3; P = 0.008) and surrounding haplotypes. The findings indicate some evidence for the role of ITGA4 as candidate gene for autism.

In silico whole genome association scan for murine prepulse inhibition

BACKGROUND

The complex trait of prepulse inhibition (PPI) is a sensory gating measure related to schizophrenia and can be measured in mice. Large-scale public repositories of inbred mouse strain genotypes and phenotypes such as PPI can be used to detect Quantitative Trait Loci (QTLs) in silico. However, the method has been criticized for issues including insufficient number of strains, not controlling for false discoveries, the complex haplotype structure of inbred mice, and failing to account for genotypic and phenotypic subgroups.

METHODOLOGY/PRINCIPAL FINDINGS

We have implemented a method that addresses these issues by incorporating phylogenetic analyses, multilevel regression with mixed effects, and false discovery rate (FDR) control. A genome-wide scan for PPI was conducted using over 17,000 single nucleotide polymorphisms (SNPs) in 37 strains phenotyped. Eighty-nine SNPs were significant at a false discovery rate (FDR) of 5%. After accounting for long-range linkage disequilibrium, we found 3 independent QTLs located on murine chromosomes 1 and 13. One of the PPI positives corresponds to a region of human chromosome 6p which includes DTNBP1, a gene implicated in schizophrenia. Another region includes the gene Tsn which alters PPI when knocked out. These genes also appear to have correlated expression with PPI.

CONCLUSIONS/SIGNIFICANCE

These results support the usefulness of using an improved in silico mapping method to identify QTLs for complex traits such as PPI which can be then be used for to help identify loci influencing schizophrenia in humans.

Dysbindin-1, a schizophrenia-related protein, functionally interacts with the DNA- dependent protein kinase complex in an isoform-dependent manner

DTNBP1 has been recognized as a schizophrenia susceptible gene, and its protein product, dysbindin-1, is down-regulated in the brains of schizophrenic patients. However, little is known about the physiological role of dysbindin-1 in the central nervous system. We hypothesized that disruption of dysbindin-1 with unidentified proteins could contribute to pathogenesis and the symptoms of schizophrenia. GST pull-down from human neuroblastoma lysates showed an association of dysbindin-1 with the DNA-dependent protein kinase (DNA-PK) complex. The DNA-PK complex interacts only with splice isoforms A and B, but not with C. We found that isoforms A and B localized in nucleus, where the kinase complex exist, whereas the isoform C was found exclusively in cytosol. Furthermore, results of phosphorylation assay suggest that the DNA-PK complex phosphorylated dysbindin-1 isoforms A and B in cells. These observations suggest that DNA-PK regulates the dysbindin-1 isoforms A and B by phosphorylation in nucleus. Isoform C does not contain exons from 1 to 6. Since schizophrenia-related single nucleotide polymorphisms (SNPs) occur in these introns between exon 1 and exon 6, we suggest that these SNPs might affect splicing of DTNBP1, which leads to impairment of the functional interaction between dysbindin-1 and DNA-PK in schizophrenic patients.

The dystrobrevin-binding protein 1 gene: features and networks

The dystrobrevin-binding protein 1 (DTNBP1) gene has been one of the most studied and promising schizophrenia susceptibility genes since it was first reported to be associated with schizophrenia in the Irish Study of High Density Schizophrenia Families (ISHDSF). Although many studies have been performed both at the functional level and in association with psychiatric disorders, there has been no systematic review of the features of the DTNBP1 gene, protein or the relationship between function and phenotype. Using a bioinformatics approach, we identified the DTNBP1 gene in 13 vertebrate species. The comparison of these genes revealed a conserved gene structure, protein-coding sequence and dysbindin domain, but a diverse noncoding sequence. The molecular evolutionary analysis suggests the DTNBP1 gene probably originated in chordates and matured in vertebrates. No signature of recent positive selection was seen in any primate lineage. The DTNBP1 gene likely has many more alternative transcripts than the current three major isoforms annotated in the NCBI database. Our examination of risk haplotypes revealed that, although the frequency of a single nucleotide polymorphism (SNP) or haplotype might be significantly different in cases from controls, difference between major geographic populations was even larger. Finally, we constructed the first DTNBP1 interactome and explored its network features. Besides the biogenesis of lysosome-related organelles complex 1 and dystrophin-associated protein complex, several molecules in the DTNBP1 network likely provide insight into the role of DTNBP1 in biological systems: retinoic acid, beta-estradiol, calmodulin and tumour necrosis factor. Studies of these subnetworks and pathways may provide opportunities to deepen our understanding of the mechanisms of action of DTNBP1 variants.

Role of glutamate in schizophrenia: integrating excitatory avenues of research

Schizophrenia is a debilitating lifelong disorder affecting up to 1% of the population worldwide, producing significant financial and emotional hardship for patients and their families. As yet, the causes of schizophrenia and the mechanism of action of antipsychotic drugs are unknown, and many patients do not respond well to currently available medications. Attempts to find risk factors for the disorder using epidemiological methods have shown that schizophrenia is highly heritable, and path analyses predict that the disorder is caused by several genes in combination with nongenetic factors. Therefore, intensive research efforts have been made to identify genes creating vulnerability to schizophrenia and also genes predicting response to treatment. Interactions of the glutamatergic system with dopaminergic and serotonergic circuitry are crucial for normal brain function, and their disruption may be a mechanism by which the pathophysiology of schizophrenia is manifest. Genes within the glutamatergic system are therefore strong candidates for investigation, and these include the glutamate receptor genes in addition to genes encoding neuregulin, dysbindin, D-amino acid oxidase and G72/G30. These genetic studies could eventually reveal new targets for antipsychotic drug treatment, which currently focuses on inhibition of the dopaminergic system. However, a recent breakthrough indicates clinical efficacy of a drug stimulating the metabotropic glutamate receptor II, LY2140023, which has improved efficacy for negative and cognitive symptoms of schizophrenia. Studies of larger patient samples are required to consolidate these data. Further investigation of glutamatergic targets is likely to reinvigorate antipsychotic drug development.

Variation in the dysbindin gene and normal cognitive function in three independent population samples

The association between DTNBP1 genotype and cognitive abilities was investigated in three population samples (1054 Scottish, 1806 Australian and 745 English) of varying age. There was evidence in each of the cohorts for association (P < 0.05) to single nucleotide polymorphisms (SNPs) and haplotypes previously shown to relate to cognition. By comparison with previous findings, these associations included measures of memory, and there was at best equivocal evidence of association with general cognitive ability. Of the SNPs typed in all three cohorts, rs2619528 and rs1011313 showed significant association with measures of executive function in two cohorts, rs1018381 showed significant association with verbal ability in one cohort and rs2619522 showed significance/marginal significance with tests of memory, speed and executive function in two cohorts. For all these SNPs, the direction and magnitude of the allelic effects were consistent between cohorts and with previous findings. In the English cohort, a previously untested SNP (rs742105) located in a distinct haplotype block upstream of the other SNPs showed the strongest significance (P < 0.01) for measures of memory but weaker significance for general cognitive ability. Our results therefore support involvement of the dysbindin gene in cognitive function, but further work is needed to clarify the specific functional variants involved and the cognitive abilities with which they are associated.

Comprehensive analysis of tagging sequence variants in DTNBP1 shows no association with schizophrenia or with its composite neurocognitive endophenotypes

In a previous study we identified a relatively homogeneous subtype of schizophrenia characterized by pervasive cognitive deficit, which was the exclusive contributor to our findings of linkage to 6p25-p24. The 6p region contains Dysbindin (DTNBP1), considered to be one of the major schizophrenia candidate genes. While multiple studies have reported association between genetic variation in DTNBP1 and schizophrenia, the findings have been inconsistent and controversial, leading to recent calls for systematic re-examination and unambiguous evidence of association. To address this, we have undertaken a comprehensive survey of common genetic variation within DTNBP1 and its association with schizophrenia, using a HapMap-based gene-tagging approach. We genotyped 39 tSNPs in a sample of 336 cases and 172 controls of Anglo-Irish ancestry, with the phenotype defined as clinical schizophrenia, and as composite neurocognitive endophenotypes. Allele and haplotype frequencies, and LD structure in our control sample were similar to those in other European populations. Using multivariate generalized linear modeling, we observed no significant association between any tSNP and any outcome variable. Association with haplotypes was examined across the gene and in the previously associated 5' region. Neither global haplotype tests, nor specific analysis of the "risk" haplotype previously reported in an ethnically related population, the Irish high-density schizophrenia families, showed significant evidence of association with schizophrenia or with the neurocognitive endophenotypes in our sample. The framework and results of this study should facilitate further attempts at re-analysis of DTNBP1, in terms of standardized approaches to both phenotype definition and analysis of genetic variation.

Analysis of copy number variation using quantitative interspecies competitive PCR

Over recent years small submicroscopic DNA copy-number variants (CNVs) have been highlighted as an important source of variation in the human genome, human phenotypic diversity and disease susceptibility. Consequently, there is a pressing need for the development of methods that allow the efficient, accurate and cheap measurement of genomic copy number polymorphisms in clinical cohorts. We have developed a simple competitive PCR based method to determine DNA copy number which uses the entire genome of a single chimpanzee as a competitor thus eliminating the requirement for competitive sequences to be synthesized for each assay. This results in the requirement for only a single reference sample for all assays and dramatically increases the potential for large numbers of loci to be analysed in multiplex. In this study we establish proof of concept by accurately detecting previously characterized mutations at the PARK2 locus and then demonstrating the potential of quantitative interspecies competitive PCR (qicPCR) to accurately genotype CNVs in association studies by analysing chromosome 22q11 deletions in a sample of previously characterized patients and normal controls.

Novel linkage to chromosome 20p using latent classes of psychotic illness in 270 Irish high-density families

BACKGROUND

Several lines of evidence suggest that the clinical heterogeneity of schizophrenia is due to genetic heterogeneity. Genetic heterogeneity may decrease the signal-to-noise ratio in linkage and association studies. Therefore, linkage studies of clinically homogeneous classes of psychotic illness may result in greater power to detect at least some loci.

METHODS

Latent class analysis was used to divide psychotic subjects from 270 Irish high-density families (N = 755) into six classes based on the Operational Criteria Checklist for Psychotic Illness. We heuristically call them Bipolar, Schizoaffective, Mania, Schizomania, Deficit Syndrome, and Core Schizophrenia. The latter four had prevalences of greater than .08 and were individually tested for linkage in a 10-cM nonparametric autosomal genomewide scan. Empirical significance was determined using 200 simulated genome scans.

RESULTS

Seven regions achieved empirical criteria for suggestive significance for at least one latent class: 5q23.2-q35.3, 8q13.1-q23.1, 10q23.33-q26.3, 12q21.2-q24.32, 19q13.32-q13.43, 20p13-q22.3, and 21q11.2-q22.3. Five of 200 simulated scans resulted in seven suggestively significant loci (experiment-wide p = .03). Furthermore, at 20p13-p12.2, the Mania and Schizomania classes individually achieved criteria, whereas Deficit Syndrome had a suggestive logarithm of the odds peak 28 cM centromeric to this locus.

CONCLUSIONS

Using empirically derived, clinically homogeneous phenotypes, four chromosomal regions were suggestively linked but provided little evidence of linkage using traditional operationalized criteria. This approach was particularly fruitful on chromosome 20, which had previously yielded little evidence of linkage. Future studies of psychiatric illness may increase their ability to detect linkage or association by using clinically homogeneous phenotypes.

Genomic structural variation and schizophrenia

It has recently been demonstrated that a large amount of structural variation exists in the human genome. Since 2004, when two landmark studies reported polymorphic levels of copy number variation in phenotypically normal individuals, our understanding of genome-wide levels of copy number variation has grown. This has inspired hypotheses about this class of variation's contribution to complex genetic phenotypes, including the specific hypothesis that structural variation is associated with psychiatric illness. The technology to accurately and efficiently detect polymorphic structural variants is still largely under development, but some examples of genomic imbalance contributing to schizophrenia and bipolar disorder already have been identified. Although much optimism surrounds this burgeoning field, the technical challenges in reliably identifying structural variation mean recent literature should be approached with caution.

Association of schizophrenia with DTNBP1 but not with DAO, DAOA, NRG1 and RGS4 nor their genetic interaction

Recent reports indicate that DAO, DAOA, DTNBP1, NRG1 and RGS4 are some of the most-replicated genes implicated in susceptibility to schizophrenia. Also, the functions of these genes could converge in a common pathway of glutamate metabolism. The aim of this study was to evaluate if each of these genes, or their interaction, was associated with schizophrenia. A case-control study was conducted in 589 Spanish patients having a diagnosis of schizophrenia, and compared with 617 equivalent control subjects. Several single nucleotide polymorphisms (SNPs) in each gene were determined in all individuals. SNP and haplotype frequencies were compared between cases and controls. The interaction between different SNPs at the same, or at different gene, loci was analyzed by the multifactor dimensionality reduction (MDR) method. We found a new schizophrenia risk and protective haplotypes in intron VII of DTNBP1; one of the most important candidate genes for this disorder, to-date. However, no association was found between DAO, DAOA, NRG1 and RGS4 and schizophrenia. The hypothesis that gene-gene interaction in these five genes could increase the risk for the disorder was not confirmed in the present study. In summary, these results may provide further support for an association between the dysbindin gene (DTNBP1) and schizophrenia, but not between the disease and DAO, DAOA, NRG1 and RGS4 or with the interaction of these genes. In the light of recent data, these results need to be interpreted with caution and future analyses with dense genetic maps are awaited.

Early visual processing deficits in dysbindin-associated schizophrenia

BACKGROUND

Variation at the dysbindin gene (DTNBP1) has been associated with increased risk for schizophrenia in numerous independent samples and recently with deficits in general and domain-specific cognitive processing. The relationship between dysbindin risk variants and sensory-level deficits in schizophrenia remains to be explored. We investigated P1 performance, a component of early visual processing on which both patients and their relatives show deficits, in carriers and noncarriers of a known dysbindin risk haplotype.

METHODS

Event-related potential responses to simple visual isolated-check stimuli were measured using high-density electrical scalp recordings in 26 individuals meeting DSM-IV criteria for schizophrenia, comprising 14 patients who were carriers of the dysbindin risk haplotype and 12 patients who were nonrisk haplotype carriers.

RESULTS

Carriers of the dysbindin risk haplotype demonstrated significantly reduced P1 amplitudes compared with noncarriers. A large effect size of d = .89 was calculated for the difference in P1 amplitude over scalp sites where the deficit was maximal.

CONCLUSIONS

The P1 deficits associated with a dysbindin risk haplotype previously identified in our sample presents functional confirmation of its deleterious effect on brain activity. Building on evidence of dysbindin's role in higher cognitive function, these early visual processing deficits suggest a generalized role for dysbindin in brain function and is likely to be part of the mechanism by which illness susceptibility is mediated.

Differential RNA expression between schizophrenic patients and controls of the dystrobrevin binding protein 1 and neuregulin 1 genes in immortalized lymphocytes

The dystrobrevin binding protein 1 (DTNBP1) and neuregulin 1 (NRG1) genes have been related to schizophrenia (SZ) and bipolar disorder (BP) by several whole-genome linkage and associations studies. Few expression studies in post-mortem brains have also reported a lower or a higher expression of DTNBP1 and NRG1, respectively, in SZ. Since the difficulty to access post-mortem brains, we evaluated RNA expression of DTNBP1 and NRG1 in immortalized lymphocytes of SZ patients and unrelated-family controls. An antipsychotic stimulation was also used to challenge the genetic background of the subjects and enhance differential expression. Immortalized lymphocytes of twelve SZ and twelve controls were grown individually in the presence or not of the antipsychotic olanzapine (Zyprexa; EliLilly). RNA was extracted and pooled in four groups of three SZ and four groups of three controls, and used to probe Agilent 18K microchips. Mean gene expression values were contrasted between SZ and control groups using a T-test. For DTNBP1, RNA expression was lower in SZ than in controls before (-28%; p=0.02) and after (-30%; p=0.01) olanzapine stimulation. Similarly, NRG1 GGF2 isoform showed a lower expression in SZ before (-29%; p=0.04) and after (-33%; p=0.02) olanzapine stimulation. In contrast, NRG1 GGF isoform showed no significant difference between SZ and controls (-7%; p=0.61, +3%; p=0.86, respectively), but was slightly repressed by olanzapine in controls (-8%; p=0.008) but not in SZ (+1%; p=0.91). These results are in agreement with those observed in post-mortem brain when the isoforms involved are considered.

Is there protective haplotype of dysbindin gene (DTNBP1) 3 polymorphisms for major depressive disorder

Dysbindin gene has been repeatedly associated with psychiatric disorders and schizophrenia in particular. This study aimed to investigate the variants of dysbindin gene in major depressive disorder (MDD). One hundred and eighty eight patients with MDD and 350 controls were investigated for 4 variants within the dysbindin gene (rs3213207 A/G, rs1011313 C/T, rs760761 C/T, and rs2619522 A/C). Haplotype analyses revealed a significant association with MDD (p=0.0007, protective A-C-T-A and A-C-C-C haplotypes), in particular the effect was due to the rs760761 (C/T) and rs2619522 (A/C) haplotype (p=0.000026). These results suggest a protective effect of some dysbindin gene haplotypes on the development of MDD. Coupled with previous findings on schizophrenia, our finding suggests that dysbindin gene variants may have a role in the susceptibility to MDD. Adequately powered further studies in different ethnic groups are warranted.

The dysbindin gene (DTNBP1) is associated with methamphetamine psychosis

BACKGROUND

The dysbindin (DTNBP1 [dystrobrevin-binding protein 1]) gene has repeatedly been shown to be associated with schizophrenia across diverse populations. One study also showed that risk haplotypes were shared with a bipolar disorder subgroup with psychotic episodes, but not with all cases. DTNBP1 may confer susceptibility to psychotic symptoms in various psychiatric disorders besides schizophrenia.

METHODS

Methamphetamine psychosis, the psychotic symptoms of which are close to those observed in schizophrenia, was investigated through a case (n = 197)-control (n = 243) association analyses of DTNBP1.

RESULTS

DTNBP1 showed significant associations with methamphetamine psychosis at polymorphisms of P1635 (rs3213207, p = .00003) and SNPA (rs2619538, p = .049) and the three-locus haplotype of P1655 (rs2619539)-P1635-SNPA (permutation p = .0005). The C-A-A haplotype, which was identical to the protective haplotype previously reported for schizophrenia and psychotic bipolar disorders, was a protective factor (p = .0013, odds ratio [OR] = .62, 95% confidence interval [CI] .51-.77) for methamphetamine psychosis. The C-G-T haplotype was a risk for methamphetamine psychosis (p = .0012, OR = 14.9, 95% CI 3.5-64.2).

CONCLUSIONS

Our genetic evidence suggests that DTNBP1 is involved in psychotic liability not only for schizophrenia but also for other psychotic disorders, including substance-induced psychosis.

Dysbindin (DTNBP1) and the biogenesis of lysosome-related organelles complex 1 (BLOC-1): main and epistatic gene effects are potential contributors to schizophrenia susceptibility

BACKGROUND

The DTNBP1 gene, encoding dysbindin, has been strongly implicated in schizophrenia (SZ) susceptibility by a series of independent genetic association and gene expression studies. Among its known functions, dysbindin is part of a protein complex, termed the biogenesis of lysosome-related organelles complex 1 (BLOC-1), the molecular components of which might be involved in the regulation of vesicular trafficking and dendrite branching.

METHODS

A systematic investigation of the other seven BLOC-1 genes (MUTED, PLDN, CNO, SNAPAP, BLOC1S1, BLOC1S2, and BLOC1S3) for evidence of association with SZ was undertaken in a sample of 373 SZ cases and 812 control subjects. Possible epistasis between combinations of BLOC-1 genes, including DTNBP1, was tested with a novel method of investigating for gene-gene interaction. Quality control measures were incorporated into genotyping strategy, and all results were corrected for multiple testing to prevent false positive results.

RESULTS

We identified significant evidence of association between BLOC1S3 and SZ (odds ratio = 1.45, confidence interval = 1.13-1.86, p = .0028, corrected p = .0389). We also report evidence for epistatic interaction between DTNBP1 and MUTED contributing to SZ in the absence of a significant main effect at MUTED (p = .0009, corrected p = .0252). Single marker and epistasis results remained significant after correction for multiple testing.

CONCLUSIONS

Together these data provide evidence for the involvement of the BLOC-1 protein complex in SZ pathogenesis.

Association study between the dystrobrevin binding protein 1 gene (DTNBP1) and schizophrenia: a meta-analysis

Positional, functional and association studies have strongly implicated the dystrobrevin binding protein 1 gene (DTNBP1) as a promising novel candidate gene for schizophrenia. Since the first association study was reported, there have been many attempts to replicate it. However the results have been mixed and these subsequent studies have produced negative as well as positive results. To reconcile these conflicting findings and to give a comprehensive picture of the relationship of DTNBP1 and schizophrenia, the current meta-analysis combined all published association studies involving nine polymorphisms up to May 2006. The results (12 studies including 3429 cases, 3376 controls and 721 trios) showed that there were five single nucleotide polymorphisms (SNPs) with p values < 0.05, however, sensitivity analyses showed that only one SNP was consistent across all nine studies (four of the five SNPs became non-significant after removal of one study), indicating that one study may cause the association findings for each of these four SNPs. In conclusion, there is only a weak association of one SNP in DTNBP1 with schizophrenia, which is not significant after multiple testing.

Fine mapping versus replication in whole-genome association studies

Association replication studies have a poor track record and, even when successful, often claim association with different markers, alleles, and phenotypes than those reported in the primary study. It is unknown whether these outcomes reflect genuine associations or false-positive results. A greater understanding of these observations is essential for genomewide association (GWA) studies, since they have the potential to identify multiple new associations that that will require external validation. Theoretically, a repeat association with precisely the same variant in an independent sample is the gold standard for replication, but testing additional variants is commonplace in replication studies. Finding different associated SNPs within the same gene or region as that originally identified is often reported as confirmatory evidence. Here, we compare the probability of replicating a gene or region under two commonly used marker-selection strategies: an "exact" approach that involves only the originally significant markers and a "local" approach that involves both the originally significant markers and others in the same region. When a region of high intermarker linkage disequilibrium is tested to replicate an initial finding that is only weak association with disease, the local approach is a good strategy. Otherwise, the most powerful and efficient strategy for replication involves testing only the initially identified variants. Association with a marker other than that originally identified can occur frequently, even in the presence of real effects in a low-powered replication study, and instances of such association increase as the number of included variants increases. Our results provide a basis for the design and interpretation of GWA replication studies and point to the importance of a clear distinction between fine mapping and replication after GWA.

Unravelling the genome: a review of molecular genetic research in schizophrenia

BACKGROUND

Schizophrenia is a common and complex mental illness that affects approximately 1% of the population worldwide. Despite intensive research over the years, the aetiology and pathogenesis of schizophrenia is poorly understood. However, it has long been recognised that schizophrenia is highly familial suggesting a possible genetic aetiology.

AIM

To review recent molecular genetic research in schizophrenia.

METHODS

Medline and Embase search.

RESULTS

Over the past decade, with the completion of the Human Genome Project, molecular genetic research has now identified a number of genes that are very likely to predispose to schizophrenia.

CONCLUSION

This article discusses the methodologies that have been used to identify schizophrenia susceptibility genes and provides a review of recently identified genes thought to play a role in the pathogenesis of this illness.

Failure to confirm allelic and haplotypic association between markers at the chromosome 6p22.3 dystrobrevin-binding protein 1 (DTNBP1) locus and schizophrenia

Background

Previous linkage and association studies may have implicated the Dystrobrevin-binding protein 1 (DTNBP1) gene locus or a gene in linkage disequilibrium with DTNBP1 on chromosome 6p22.3 in genetic susceptibility to schizophrenia.

Methods

We used the case control design to test for of allelic and haplotypic association with schizophrenia in a sample of four hundred and fifty research subjects with schizophrenia and four hundred and fifty ancestrally matched supernormal controls. We genotyped the SNP markers previously found to be significantly associated with schizophrenia in the original study and also other markers found to be positive in subsequent studies.

Results

We could find no evidence of allelic, genotypic or haplotypic association with schizophrenia in our UK sample.

Conclusion

The results suggest that the DTNBP1 gene contribution to schizophrenia must be rare or absent in our sample. The discrepant allelic association results in previous studies of association between DTNBP1 and schizophrenia could be due population admixture. However, even positive studies of European populations do not show any consistent DTNBP1 alleles or haplotypes associated with schizophrenia. Further research is needed to resolve these issues. The possible confounding of linkage with association in family samples already showing linkage at 6p22.3 might be revealed by testing genes closely linked to DTNBP1 for allelic association and by restricting family based tests of association to only one case per family.

Functional genomics and schizophrenia: endophenotypes and mutant models

This article summarizes the rationale, methods, and results of gene discovery programs in schizophrenia research and describes functional methods of investigating potential candidate genes. It focuses next on the most prominent current candidate genes and describes (1) evidence for their association with schizophrenia and research into the function of each gene; (2) investigation of the clinical phenotypes and endophenotypes associated with each gene, at the levels of psychopathologic, neurocognitive, electrophysiologic, neuroimaging, and neuropathologic findings; and (3) research into the ethologic, cognitive, social, and psychopharmacologic phenotype of mutants with targeted deletion of each gene. It examines gene-gene and gene-environment interactions. Finally, it looks at future directions for research.

Association study of dysbindin gene with clinical and outcome measures in a representative cohort of Italian schizophrenic patients

There is evidence suggesting that Dysbindin (DTNBP1) is a susceptibility gene for schizophrenia in Caucasian, Chinese, and Japanese populations. We sought to determine if dysbindin was associated with schizophrenia and its symptoms in a representative group of schizophrenic patients from a Community-Based Mental Health Service (CMHS) in Verona, Italy. A prevalence cohort of schizophrenic patients (n = 141) was assessed at baseline and then 3 and 6 years later. Eighty patients and 106 healthy controls were genotyped for polymorphisms in dysbindin. We tested if diagnosis, clinical symptoms as measured by the Brief Psychiatric Rating Scale (BPRS), and functioning as measured by the Global Assessment of Functioning Scale (GAF), were associated with the presence of certain dysbindin polymorphisms. Finally, using the longitudinal clinical data, we tested if patients carrying dysbindin high-risk haplotypes had a more unfavorable longitudinal clinical outcome. A trend towards statistical association (P = 0.058) between schizophrenia and rs2619538 was found. Using GENECOUNTING software, we found that rs2619538-P1583 (P = 0.048), P1320-P1757 (P = 0.034), and rs2619538-P1583-P1578 (P = 0.040) haplotypes occurred more often in cases compared to controls before correction for multiple testing. The rs2619538-P1583 haplotype was more likely to be transmitted to subjects with more severe and persistent psychopathology. These preliminary results are compatible with the view that DTNBP1 is a susceptibility factor for schizophrenia, and is associated with worse psychopathology.

No association evidence between schizophrenia and dystrobrevin-binding protein 1 (DTNBP1) in Taiwanese families

Several linkage studies have shown significant linkage of schizophrenia to chromosome 6p region, which includes the positional candidate genes, Dystrobrevin-binding protein 1 (DTNBP1). The aim was to examine the association evidence of the candidate gene in 693 Taiwanese families with at least two affected siblings of schizophrenia. We genotyped nine SNPs of this gene with average intermarker distance of 17 kb. Intermarker linkage disequilibrium was calculated with GOLD. Single locus and haplotype association analyses were performed with TRANSMIT program. We found no significant association between schizophrenia and DTNBP1 either through single locus or haplotype analyses. We failed to replicate the association evidence between DTNBP1 and schizophrenia and this gene may not play a major role in the etiology of schizophrenia in this Taiwanese family sample.

Association study between Apolipoprotein L and schizophrenia by exhaustive and rule-based combination analysis for identification of multilocus interactions

Several single marker association and haplotypic analyses have been performed to identify susceptible genes for various common diseases, but these approaches using candidate genes did not provide accurate and consistent evidence in each analysis. This inconsistency is partly due to the fact that the common diseases are caused by complex interactions among various genetic factors. Therefore, in this study, to evaluate exhaustive genotype or allele combinations, we applied the binomial and random permutation test (BRP) proposed by Tomita et al. [IPSJ Digital Courier, 2, 691-709 (2006)] for the association analysis between an Apolipoprotein L gene cluster and schizophrenia. Using the seven selected representative single nucleotide polymorphisms (SNPs) based on the results of linkage disequilibrium evaluation, we analyzed 845 schizophrenic patients and 707 healthy controls, and investigated the validation of risk and protective factors with two randomly divided data sets. A comparative study of a method for analyzing the interactions was performed by conventional methods. Even if all the tested methods were used for analysis, the risk factor with a high significance was not commonly selected from both independent data sets. However, the significant interactions for the protective factor against disease development were commonly obtained from both data sets by BRP analysis. In conclusion, although it is considered that the causality of schizophrenia is too complex to identify a susceptible interaction using a small sample size, it was suggested that the healthy controls tend to have the same combination of certain alleles or genotypes for protection from disease development when BRP as a new exhaustive combination analytical method was used.

DTNBP1 (Dystrobrevin binding protein 1) and schizophrenia: association evidence in the 3' end of the gene

OBJECTIVES

Dysbindin (DTNBP1) has been identified as a susceptibility gene for schizophrenia (SZ) through a positional approach. However, a variety of single nucleotide polymorphisms (SNPs) and haplotypes, in different parts of the gene, have been reported to be associated in different samples, and a precise molecular mechanism of disease remains to be defined. We have performed an association study with two well-characterized family samples not previously investigated at the DTNBP1 locus.

METHODS

We examined 646 subjects in 136 families with SZ, largely of European ancestry (EA), genotyping 26 SNPs in DTNBP1.

RESULTS

Three correlated markers (rs875462, rs760666, and rs7758659) at the 3' region of DTNBP1 showed evidence for association to SZ (p = 0.004), observed in both the EA (p = 0.031) and the African American (AA) subset (p = 0.045) with the same over-transmitted allele. The most significant haplotype in our study was rs7758659-rs3213207 (global p = 0.0015), with rs3213207 being the most frequently reported associated marker in previous studies. A non-conservative missense variant (Pro272Ser) in the 3' region of DTNBP1 that may impair DTNBP1 function was more common in SZ probands (8.2%) than in founders (5%) and in dbSNP (2.1%), but did not reach statistical significance.

CONCLUSION

Our results provide evidence for an association of SZ with SNPs at the 3' end of DTNBP1 in the samples studied.

Association between the DTNBP1 gene and intelligence: a case-control study in young patients with schizophrenia and related disorders and unaffected siblings

BACKGROUND

The dystrobrevin-binding protein 1 (DTNBP1) gene is a susceptibility gene for schizophrenia. There is growing evidence that DTNPB1 contributes to intelligence and cognition. In this study, we investigated association between single nucleotide polymorphisms (SNPs) in the DTNBP1 gene and intellectual functioning in patients with a first episode of schizophrenia or related psychotic disorder (first-episode psychosis, FEP), their healthy siblings, and unrelated controls.

METHODS

From all subjects IQ measurements were obtained (verbal IQ [VIQ], performance IQ [PIQ], and full scale IQ [FSIQ]). Seven SNPs in the DTNBP1 gene were genotyped using single base primer extension and analyzed by matrix-assisted laser deionization mass spectrometry (MALDI-TOF).

RESULTS

Mean VIQ, PIQ, and FSIQ scores differed significantly (p < 0.001) between patients, siblings, and controls. Using a family-based and a case-control design, several single SNPs were significantly associated with IQ scores in patients, siblings, and controls.

CONCLUSION

Although preliminary, our results provide evidence for association between the DTNBP1 gene and intelligence in patients with FEP and their unaffected siblings. Genetic variation in the DTNBP1 gene may increase schizophrenia susceptibility by affecting intellectual functioning.

A resistance gene in disguise for schizophrenia?

We examined the hypothesis that -485 T, a novel polymorphism in the promoter region of the neuropeptide Y gene which was shown to be associated with schizophrenia in our previous paper, confers susceptibility to the disease. For a case-control association study, 331 unrelated Japanese schizophrenics (S(1): milder cases in the previous study, n = 212; and S(2): additional severer cases, n = 119) and 199 unrelated normal controls were recruited. Contribution of -485 T to the risk and the severity of the illness was examined by (1) comparing the risk in each genotype in the general population, (2) testing correlations between the gene-dose of -485 T, and the severity of chronic outcome in S(2) assessed with the Positive and Negative Symptom Scale, and (3) comparing the distribution of age at onset in S(1) + S(2) among the three genotypes. -485 T was significantly associated with schizophrenia in S(1) + S(2). Significant negative correlations were observed between the gene-dose and the symptom assessment scores in all items. The homozygote of -485 T showed a second peak frequency in the late-onset group both in males and females, while the homozygote of the alternative allele showed a single peak in the early-onset group. The higher risk of schizophrenia in the heterozygote than in the homozygote of -485 T in the general population did not support the possibility of linkage disequilibrium with a susceptibility gene. -485 T most likely confers resistance but not susceptibility to schizophrenia. An interaction between a nuclear resistance gene and a presumptive pathogenic gene in the mitochondrial DNA was suggested.

Association between the 5q31.1 gene neurogenin1 and schizophrenia

Multiple lines of evidence suggest that schizophrenia results from aberrant neurodevelopment. The neurogenin1 gene (neurog1) consists of a single 1,666 bp exon that encodes a basic helix-loop-helix (bHLH) transcription factor that causes neuronal differentiation and induces cortical and glutamatergic differentiation programs. Because of its function and its location in 5q31.1, which has been linked to schizophrenia in multiple samples, we tested it for association with the disorder. We sequenced neurog1 in 25 affected subjects from the Irish Study of High-Density Schizophrenia Families. We observed a 5'-UTR SNP at position -60, already present in databases as rs8192558, and tested it along with rs2344485, rs8192559, and rs2344484. Narrow, intermediate, and broad diagnostic definitions were used. The major alleles of rs8192558 and rs2344484 were over-transmitted to affected subjects using both Pedigree Disequilibrium Test (PDT) (0.01 < or = P < or = 0.06) and FBAT (0.02 < or = P < or = 0.07). A haplotype consisting of the major alleles of all four SNPs was significantly over-transmitted in FBAT to the broad definition (P = 0.049), with trend significance to the narrow and intermediate definitions, and with trend significance in PDT. In confirmatory tests using 657 cases and 411 controls, this haplotype was slightly but not significantly over-represented in cases (81% vs. 77%, P = 0.21). These results, along with a priori evidence for the involvement of neurog1 in neurodevelopment, suggest that variants in neurog1 might have a small effect on susceptibility to schizophrenia. This gene should be tested in additional and larger samples.

ThePIP5K2AandRGS4genes are differentially associated with deficit and non-deficit schizophrenia

Several putative schizophrenia susceptibility genes have recently been reported, but it is not clear whether these genes are associated with schizophrenia in general or with specific disease subtypes. In a previous study, we found an association of the neuregulin 1 (NRG1) gene with non-deficit schizophrenia only. We now report an association study of four schizophrenia candidate genes in patients with and without deficit schizophrenia, which is characterized by severe and enduring negative symptoms. Single-nucleotide polymorphisms (SNPs) were genotyped in the DTNBP1 (dysbindin), G72/G30 and RGS4 genes, and the relatively unknown PIP5K2A gene, which is located in a region of linkage with both schizophrenia and bipolar disorder. The sample consisted of 273 Dutch schizophrenia patients, 146 of whom were diagnosed with deficit schizophrenia and 580 controls. The strongest evidence for association was found for the A-allele of SNP rs10828317 in the PIP5K2A gene, which was associated with both clinical subtypes (P = 0.0004 in the entire group; non-deficit P = 0.016, deficit P = 0.002). Interestingly, this SNP leads to a change in protein composition. In RGS4, the G-allele of the previously reported SNP RGS4-1 (single and as part of haplotypes with SNP RGS4-18) was associated with non-deficit schizophrenia (P = 0.03) but not with deficit schizophrenia (P = 0.79). SNPs in the DTNBP1 and G72/G30 genes were not significantly associated in any group. In conclusion, our data provide further evidence that specific genes may be involved in different schizophrenia subtypes and suggest that the PIP5K2A gene deserves further study as a general susceptibility gene for schizophrenia.

The role of DTNBP1, NRG1, and AKT1 in the genetics of schizophrenia in Finland

Several putative schizophrenia susceptibility genes have recently been identified. Significant associations between schizophrenia and neuregulin 1 (NRG1) and dysbindin (DTNBP1) were first reported in 2002 and studies in several populations have since independently reported positive associations to these gene regions. Further, both tentative functional and genetic data have implicated the role of AKT1 in the genetic background of this disorder. However, findings have not been consistent in all populations. We investigated the allelic diversity of these three genes NRG1, DTNBP1 and AKT1 in a representative nation-wide study sample of 441 Finnish schizophrenia families consisting of 865 affected individuals, in order to assess their role in one of the largest population-based study samples. DTNBP1 and AKT1 failed to show evidence of association, whereas two SNPs in the 3' region of the NRG1 gene yielded suggestive evidence of association (p=0.012 and p=0.048) in family-based association analyses. Thus, our study does not indicate that AKT1 or DTNBP1 play a role in the etiology of schizophrenia in the Finnish population. Furthermore, results do not support a major role for NRG1, but we cannot completely exclude a minor role of this gene in the Finnish population.

Risk factors for schizophrenia--all roads lead to dopamine

Schizophrenia is a debilitating disease of major public health importance, the incidence of which shows prominent worldwide variation (up to fivefold) and is about 40% greater in men than in women. Furthermore, epidemiological studies have shown that the incidence is higher among those who grow up in urban areas and among migrants. Recent evidence indicates that, although the neurochemical origins of schizophrenia do not necessarily lie in dopamine dysregulation, this operates as the final common pathway underlying positive psychotic symptoms and may also play a role in negative and cognitive symptoms. The last few years have seen the development of a plausible model in which schizophrenia is seen as the consequence of the actions of a number of component causes, such as genes or early environmental hazards that subtly alter subsequent neurodevelopment, thereby predisposing the child to later dopamine dysregulation.

Schizophrenia: a common disease caused by multiple rare alleles

Schizophrenia is widely held to stem from the combined effects of multiple common polymorphisms, each with a small impact on disease risk. We suggest an alternative view: that schizophrenia is highly heterogeneous genetically and that many predisposing mutations are highly penetrant and individually rare, even specific to single cases or families. This "common disease--rare alleles" hypothesis is supported by recent findings in human genomics and by allelic and locus heterogeneity for other complex traits. We review the implications of this model for gene discovery research in schizophrenia.

Interleukin 3 and schizophrenia: the impact of sex and family history

Chromosome 5q21-33 has been implicated in harboring risk genes for schizophrenia. In this paper, we report evidence that multiple single nucleotide polymorphisms in and around interleukin 3 (IL3) are associated with the disease in the Irish Study of High-Density Schizophrenia Families (ISHDSF), the Irish Case-Control Study of Schizophrenia (ICCSS) and the Irish Trio Study of Schizophrenia (ITRIO). The associations are sex-specific and depend on the family history (FH) of schizophrenia. In all three samples, rs31400 shows female-specific and FH-dependent associations (P=0.0062, 0.0647 and 0.0284 for the ISHDSF, ICCSS and ITRIO, respectively). Several markers have similar associations in one or two of the three samples. In haplotype analyses, identical risk and protective haplotypes are identified in the ISHDSF and ITRIO samples in several multimarker combinations. For ICCSS, the same haplotypes are implicated; however, the risk haplotypes observed in the family samples become protective. Several significant markers, rs440970, rs31400 and rs2069803, are located in and around known estrogen response elements, promoter and enhancer of the IL3 gene. They may explain the sex-specific associations and be functional for the expression of IL3 gene.

Dystrobrevins in muscle and non-muscle tissues

The alpha- and beta-dystrobrevins belong to the family of dystrophin-related and dystrophin-associated proteins. As constituents of the dystrophin-associated protein complex, alpha-dystrobrevin was believed to have a role predominantly in muscles and beta-dystrobrevin in non-muscle tissues. Recent reports described novel localisations and molecular characteristics of alpha-dystrobrevin isoforms in non-muscle tissues (developing and adult). While single and double knockout studies have revealed distinct functions of dystrobrevin in some tissues, these also suggested a strong compensatory mechanism, where dystrobrevins displaying overlapping tissue expression pattern and structure/function similarity can substitute each other. No human disease has been unequivocally associated within mutations of dystrobrevin genes. However, some significant exceptions to these overlapping expression patterns, mainly in the brain, suggest that dystrobrevin mutations might underlie some specific motor, behavioural or cognitive defects. Dystrobrevin binding partner DTNBP1 (dysbindin) is a probable susceptibility gene for schizophrenia and bipolar affective disorder in some populations. As dysbindin abnormality is linked to Hermansky-Pudlak syndrome, dystrobrevins and/or their binding partners may also be required for proper function of other non-muscle tissues.

Positive association of schizophrenia to JARID2 gene

Dysbindin (DTNBP1) is a positional candidate gene for 6p22.3-linked schizophrenia (SZ). However, so far, no disease-causing alleles have been identified. DTNBP1 is immediately adjacent to JARID2, a member of the ARID (AT-rich interaction domain) family of transcription modulators. We have previously suggested that proteins which bind to AT-rich domains could play a role in SZ pathogenesis. Consequently, we explored the possibility that JARID2 itself could be a candidate gene for 6p22.3-linked SZ. We used a case control design to analyze single nucleotide polymorphisms (SNPs) and insertion/deletion variants affecting AT-rich domains in both the DTNBP1 and JARID2 genes. Three of the DTNBP1 SNPs analyzed had previously been shown to be associated with SZ. We did not detect any significant difference in allele, genotype or haplotype distribution for any of these DTNBP1 markers. However, we did detect a significant difference in allele distribution for a tetranucleotide repeat polymorphism in the JARID2 gene that affects an AT-rich domain. A significant increase in short alleles (less than 11 repeats) was found in patients with SZ (chi(2) = 7.02; P = 0.008). No other JARID2 marker displayed statistically significant allele and genotype distributions. Our findings suggest that JARID2 should be viewed as a candidate gene for 6p22.3-linked SZ.

DTNBP1 genotype influences cognitive decline in schizophrenia

OBJECTIVE

Intellectual decline is common in schizophrenia and predicts functional outcome. While many patients undergo intellectual decline that typically predates the onset of symptoms, few studies have investigated the underlying mechanism through which this occurs. The current study assessed the relationship between intellectual decline in schizophrenia and genetic variation in dysbindin-1 (DTNBP1).

METHODS

We assessed cognitive decline in 183 Caucasian patients with schizophrenia using a proxy measure of premorbid IQ with which current general cognitive ability (g) was compared. We then tested for a relationship between the risk haplotype identified in previous work (CTCTAC) and intellectual decline.

RESULTS

We found that carriers of the CTCTAC haplotype, demonstrated a significantly greater decline in IQ as compared with non-carriers (p=0.05).

CONCLUSIONS

These data suggest that DTNBP1 influences the severity of intellectual decline in schizophrenia and may represent one underlying cause for heterogeneity in cognitive course.

Variance in neurocognitive performance is associated with dysbindin-1 in schizophrenia: A preliminary study

Susceptibility genes for schizophrenia have been hypothesised to mediate liability for the disorder at least partly by influencing cognitive performance. We investigated the association between genotype and cognitive performance for a Dysbindin risk haplotype which is associated with schizophrenia in our sample. Fifty-two patients with schizophrenia or schizoaffective disorder (24 risk haplotypes carriers versus 28 non-risk haplotype carriers) were assessed in areas of cognition showing evidence of familial deficits in schizophrenia. Verbal and spatial memory, working memory, and attentional control was assessed using selected measures from the Weschler memory scale (WMS), Cambridge automated test battery (CANTAB), continuous performance test (CPT), and a simple go/no-go task. Pre-morbid IQ was also assessed using the Weschler Test of Adult Reading (WTAR). Patients carrying the Dysbindin risk haplotype showed significantly lower spatial working memory performance than patients who were non-risk carriers, with genotype explaining 12% of variance in performance. Our study suggests that the increased risk for schizophrenia associated with dysbindin may be partly mediated by its influence on pre-frontal function.

Schizophrenia susceptibility genes: in search of a molecular logic and novel drug targets for a devastating disorder

Schizophrenia is a devastating psychiatric disorder that affects approximately one percent of the population worldwide. We argue that the efforts to decipher the genetic causes of schizophrenia have reached another turning point and describe evidence supporting some of the major recent genetic findings in the field. In addition, we identify some general areas of caution in the interpretation of these findings and addresses the promise this recently acquired knowledge holds for the generation of reliable animal models, characterization of genetic interactions, dissection of the disease pathophysiology and development of novel, mechanism-based treatments for the patients.