Association of DISC1 gene with schizophrenia in families from two distinct French and Algerian populations

De Novo Variants Found in Three Distinct Schizophrenia Populations Hit a Common Core Gene Network Related to Microtubule and Actin Cytoskeleton Gene Ontology Classes

Schizophrenia (SZ) is a heterogeneous and debilitating psychiatric disorder with a strong genetic component. To elucidate functional networks perturbed in schizophrenia, we analysed a large dataset of whole-genome studies that identified SNVs, CNVs, and a multi-stage schizophrenia genome-wide association study. Our analysis identified three subclusters that are interrelated and with small overlaps: GO:0007017~Microtubule-Based Process, GO:00015629~Actin Cytoskeleton, and GO:0007268~SynapticTransmission. We next analysed three distinct trio cohorts of 75 SZ Algerian, 45 SZ French, and 61 SZ Japanese patients. We performed Illumina HiSeq whole-exome sequencing and identified de novo mutations using a Bayesian approach. We validated 88 de novo mutations by Sanger sequencing: 35 in French, 21 in Algerian, and 32 in Japanese SZ patients. These 88 de novo mutations exhibited an enrichment in genes encoding proteins related to GO:0051015~actin filament binding (p = 0.0011) using David, and enrichments in GO: 0003774~transport (p = 0.019) and GO:0003729~mRNA binding (p = 0.010) using Amigo. One of these de novo variant was found in CORO1C coding sequence. We studied Coro1c haploinsufficiency in a Coro1c+/- mouse and found defects in the corpus callosum. These results could motivate future studies of the mechanisms surrounding genes encoding proteins involved in transport and the cytoskeleton, with the goal of developing therapeutic intervention strategies for a subset of SZ cases.

Disrupted-in-schizophrenia 1 functional polymorphisms and D2 /D3 receptor availability: A [11 C]-(+)-PHNO imaging study

The disrupted-in-schizophrenia 1 (DISC1) protein has been implicated in a range of biological mechanisms underlying chronic mental disorders such as schizophrenia. Schizophrenia is associated with abnormal striatal dopamine signalling, and all antipsychotic drugs block striatal dopamine 2/3 receptors (D_2/3 Rs). Importantly, the DISC1 protein directly interacts and forms a protein complex with the dopamine D₂ receptor (D₂ R) that inhibits agonist-induced D₂ R internalisation. Moreover, animal studies have found large striatal increases in the proportion of D₂ R receptors in a high affinity state (D₂ ^high R) in DISC1 rodent models. Here, we investigated the relationship between the three most common polymorphisms altering the amino-acid sequence of the DISC1 protein (Ser704Cys (rs821616), Leu607Phe (rs6675281) and Arg264Gln (rs3738401)) and striatal D_2/3 R availability in 41 healthy human volunteers, using [¹¹ C]-(+)-PHNO positron emission tomography. We found no association between DISC1 polymorphisms and D_2/3 R availability in the striatum and D₂ R availability in the caudate and putamen. Therefore, despite a direct interaction between DISC1 and the D₂ R, none of its main functional polymorphisms impact striatal D_2/3 R binding potential, suggesting DISC1 variants act through other mechanisms.

The interaction of NOS1AP, DISC1, DAOA, and GSK3B confers susceptibility of early-onset schizophrenia in Chinese Han population

Although many major breakthrough had identificated potential susceptibility genes for schizophrenia, the aetiology of schizophrenia is still unknown. In the present study, we focused on the N-methyl-Daspartate receptors related genes nitric oxide synthase 1 adaptor gene (NOS1AP), disrupted in schizophrenia 1 gene (DISC1), d-amino acid oxidase activator gene (DAOA), and glycogen synthase kinase 3-beta gene (GSK3B). A family-based genetic association study (459 Han Chinese subjects in 153 nuclear families) using 3 single nucleotide polymorphisms in NOS1AP, 2 in DISC1, 1 in DAOA and 1 in GSK3B was conducted. We found rs12742393 have just positive trend with schizophrenia (SCZ) (p=0.07) after FDR correction. NOS1AP mRNA and serum levels were significantly elevated in SCZ patients (p<0.001; p<0.001) compared with healthy control. However, expression Quantitative Trait Loci (eQTL) analysis have demonstrated that rs12742393 genotype were not significantly associated with the NOS1AP mRNA expression. GMDR identified a significant seven-locus interaction model involving (NOS1AP-rs348624, rs12742393, rs1415263, DISC1-rs821633, rs1000731, DAOA-rs2391191and GSK3B- rs6438552) with a good testing accuracy (0.72). Our finding suggested statistically significant role of interaction of NOS1AP, DISC1, DAOA, and GSK3B polymorphisms (NOS1AP-rs348624, rs12742393, rs1415263, DISC1-rs821633, rs1000731, DAOA-rs2391191and GSK3B-rs6438552) in EOS susceptibility.

Association analysis of DISC1 gene polymorphisms with Attention-Deficit Hyperactivity Disorder in Iranian population

Background & Objectives:

Attention deficit hyperactivity disorder (ADHD) is a common heritable psychiatric disorder with a worldwide prevalence of 5%. The etiology of ADHD is still incompletely understood, but several studies, consistently indicate the strong role of genetic factors on this disorder. The aim of this study was to determine the effect of three SNPs rs11122319, rs11122330 and rs6675281 in the etiology of ADHD in an Iranian children

Methods:

In this research work, for the first time, we investigated the association of three SNPs (rs11122330, rs6675281 and rs11122319) in the DISC1 gene with ADHD in Iranian population. Two hundred fourthy subjects composed of 120 patients and 120 healthy controls were included and tetra-primer ARMS PCR technique was used for genotyping all selected SNPs.

Results:

We found differences in genotype and allele distributions of rs 6675281 polymorphism between our patients and controls. The A, T and A alleles were the more frequent alleles in rs11122319, rs6675281 and rs11122330 polymorphisms in both case and control groups respectively. The TT genotype was more frequent in control group compared to patients. (P value = 0.008, OR= 1.5837, 95% CI= 1.1012 to 2.2776).

Conclusion:

Our findings strengthens the role of DISC1 gene as a susceptibility locus for ADHD and indicate that rs6675281 polymorphism is a susceptibility factor for ADHD for the first time in children reported in an Iranian population in this part of the world.

Functional properties of rare missense variants of human CDH13 found in adult attention deficit/hyperactivity disorder (ADHD) patients

The CDH13 gene codes for T-cadherin, a GPI-anchored protein with cell adhesion properties that is highly expressed in the brain and cardiovascular system. Previous studies have suggested that CDH13 may be a promising candidate gene for Attention Deficit/Hyperactivity Disorder (ADHD). The aims of this study were to identify, functionally characterize, and estimate the frequency of coding CDH13 variants in adult ADHD patients and controls. We performed sequencing of the CDH13 gene in 169 Norwegian adult ADHD patients and 63 controls and genotyping of the identified variants in 641 patients and 668 controls. Native and green fluorescent protein tagged wild type and variant CDH13 proteins were expressed and studied in CHO and HEK293 cells, respectively. Sequencing identified seven rare missense CDH13 variants, one of which was novel. By genotyping, we found a cumulative frequency of these rare variants of 2.9% in controls and 3.2% in ADHD patients, implying that much larger samples are needed to obtain adequate power to study the genetic association between ADHD and rare CDH13 variants. Protein expression and localization studies in CHO cells and HEK293 cells showed that the wild type and mutant proteins were processed according to the canonical processing of GPI-anchored proteins. Although some of the mutations were predicted to severely affect protein secondary structure and stability, no significant differences were observed between the expression levels and distribution of the wild type and mutant proteins in either HEK293 or CHO cells. This is the first study where the frequency of coding CDH13 variants in patients and controls is reported and also where the functional properties of these variants are examined. Further investigations are needed to conclude whether CDH13 is involved in the pathogenesis of ADHD or other conditions.

Personalized medicine in psychiatry: problems and promises

The central theme of personalized medicine is the premise that an individual's unique physiologic characteristics play a significant role in both disease vulnerability and in response to specific therapies. The major goals of personalized medicine are therefore to predict an individual's susceptibility to developing an illness, achieve accurate diagnosis, and optimize the most efficient and favorable response to treatment. The goal of achieving personalized medicine in psychiatry is a laudable one, because its attainment should be associated with a marked reduction in morbidity and mortality. In this review, we summarize an illustrative selection of studies that are laying the foundation towards personalizing medicine in major depressive disorder, bipolar disorder, and schizophrenia. In addition, we present emerging applications that are likely to advance personalized medicine in psychiatry, with an emphasis on novel biomarkers and neuroimaging.

Association study of three microsatellite polymorphisms located in introns 1, 8, and 9 of DISC1 with schizophrenia in the Chinese Han population

AIMS

This study explores more polymorphisms in Disrupted-in-schizophrenia-1 (DISC1) for schizophrenia, which confer risk of developing the disorder.

RESULTS

We report three short tandem repeat (STR) loci ((ATCC)n1, D1S1621, and (ATCC)n2) in DISC1 that showed a significant association with schizophrenia in a set of Chinese Han individuals, including 310 schizophrenics and 400 controls. The STRs in DISC1 associated with schizophrenia occur in intronic sequences in the vicinity of a critical splice junction that gives rise to the expression of DISC1 isoforms. The frequencies of allele 12 of (ATCC)n1, alleles 11 and 12, allele 13 and allele 15 of D1S1621, and allele 10 of (ATCC)n2 were significantly higher in schizophrenia patients than in controls. In contrast, the frequencies of alleles 9 and 10 of (ATCC)n1 and allele 16 and alleles17 and 18 of D1S1621 were significantly lower in schizophrenia patients than in controls.

CONCLUSIONS

Our results provide further evidence for an effect of the DISC1 gene on the etiology of schizophrenia and suggest that STRs in the DISC1 gene may be genetic risk factors for schizophrenia.

DISC1 (disrupted-in-schizophrenia 1) is associated with cortical grey matter volumes in the human brain: a voxel-based morphometry (VBM) study

DISC1 (Disrupted-In-Schizophrenia 1), one of the top candidate genes for schizophrenia, has been associated with a range of major mental illnesses over the last two decades. DISC1 is crucially involved in neurodevelopmental processes of the human brain. Several haplotypes and single nucleotide polymorphisms of DISC1 have been associated with changes of grey matter volumes in brain regions known to be altered in schizophrenia and other psychiatric disorders. The aim of the present study was to investigate the effects of two single nucleotide polymorphisms (SNPs) of DISC1 on grey matter volumes in human subjects using voxel-based morphometry (VBM). 114/113 participating subjects (psychiatric patients and healthy controls) were genotyped with respect to two at-risk SNPs of DISC1, rs6675281 and rs821616. All participants underwent structural magnetic resonance imaging (MRI). MRI data was statistically analyzed using voxel-based morphometry. We found significant alterations of grey matter volumes in prefrontal and temporal brain regions in association with rs6675281 and rs821616. These effects of DISC1 polymorphisms on brain morphology provide further support for an involvement of DISC1 in the neurobiology of major psychiatric disorders such as schizophrenia.

DISC1 variants 37W and 607F disrupt its nuclear targeting and regulatory role in ATF4-mediated transcription

Disrupted-In-Schizophrenia 1 (DISC1), a strong genetic candidate for psychiatric illness, encodes a multicompartmentalized molecular scaffold that regulates interacting proteins with key roles in neurodevelopment and plasticity. Missense DISC1 variants are associated with the risk of mental illness and with brain abnormalities in healthy carriers, but the underlying mechanisms are unclear. We examined the effect of rare and common DISC1 amino acid substitutions on subcellular targeting. We report that both the rare putatively causal variant 37W and the common variant 607F independently disrupt DISC1 nuclear targeting in a dominant-negative fashion, predicting that DISC1 nuclear expression is impaired in 37W and 607F carriers. In the nucleus, DISC1 interacts with the transcription factor Activating Transcription Factor 4 (ATF4), which is involved in the regulation of cellular stress responses, emotional behaviour and memory consolidation. At basal cAMP levels, wild-type DISC1 inhibits the transcriptional activity of ATF4, an effect that is weakened by both 37W and 607F independently, most likely as a consequence of their defective nuclear targeting. The common variant 607F additionally reduces DISC1/ATF4 interaction, which likely contributes to its weakened inhibitory effect. We also demonstrate that DISC1 modulates transcriptional responses to endoplasmic reticulum stress, and that this modulatory effect is ablated by 37W and 607F. By showing that DISC1 amino acid substitutions associated with psychiatric illness affect its regulatory function in ATF4-mediated transcription, our study highlights a potential mechanism by which these variants may impact on transcriptional events mediating cognition, emotional reactivity and stress responses, all processes of direct relevance to psychiatric illness.

DISC1-binding proteins in neural development, signalling and schizophrenia

In the decade since Disrupted in Schizophrenia 1 (DISC1) was first identified it has become one of the most convincing risk genes for major mental illness. As a multi-functional scaffold protein, DISC1 has multiple identified protein interaction partners that highlight pathologically relevant molecular pathways with potential for pharmaceutical intervention. Amongst these are proteins involved in neuronal migration (e.g. APP, Dixdc1, LIS1, NDE1, NDEL1), neural progenitor proliferation (GSK3β), neurosignalling (Girdin, GSK3β, PDE4) and synaptic function (Kal7, TNIK). Furthermore, emerging evidence of genetic association (NDEL1, PCM1, PDE4B) and copy number variation (NDE1) implicate several DISC1-binding partners as risk factors for schizophrenia in their own right. Thus, a picture begins to emerge of DISC1 as a key hub for multiple critical developmental pathways within the brain, disruption of which can lead to a variety of psychiatric illness phenotypes.

Association study between Disrupted-in-Schizophrenia-1 (DISC1) and Japanese patients with treatment-resistant schizophrenia (TRS)

Treating the 20-30% of patients with schizophrenia whose symptoms are resistant to antipsychotic treatment, a condition known as treatment-resistant schizophrenia (TRS), can be problematic. Recently, an association between Disrupted-in-Schizophrenia-1 (DISC1), a candidate susceptibility gene for schizophrenia, and TRS was reported. Associations between three missense SNPs, rs3738401 (Q264R), rs6675281 (L607F), and rs821616 (S704C) in DISC1, especially rs3738401, showed strong significance. Thus, the main aim of our current study was to examine if the reported possible functional polymorphisms in DISC1 were related to Japanese TRS. First, DISC1 was re-investigated in 485 Japanese patients with schizophrenia and 660 healthy controls with a case-control study using four candidate SNPs, rs751229, rs3738401, rs821597, and rs821616. DISC1 was not associated with schizophrenia in the Japanese population. Second, we investigated whether these SNPs contributed to TRS in 127 inpatients with schizophrenia (35 patients; TRS and 92 patients; non-TRS). The genotypic distributions of these four SNPs were not significantly different between TRS and non-TRS in either genotypic or recessive models of minor alleles. In addition, clinical variables, such as improvement in clinical symptoms, duration of hospitalization, and total antipsychotics dose amounts, were not different among the genotypes of these SNPs. Taken together, results showed that DISC1 had no apparent degree of association with Japanese patients with schizophrenia as a candidate susceptibility gene for disease per se or TRS.