Contribution of Rare Copy Number Variants to Bipolar Disorder Risk Is Limited to Schizoaffective Cases.

BACKGROUND: Genetic risk for bipolar disorder (BD) is conferred through many common alleles, while a role for rare copy number variants (CNVs) is less clear. Subtypes of BD including schizoaffective disorder bipolar type (SAB), bipolar I disorder (BD I), and bipolar II disorder (BD II) differ according to the prominence and timing of psychosis, mania, and depression. The genetic factors contributing to the combination of symptoms among these subtypes are poorly understood. METHODS: Rare large CNVs were analyzed in 6353 BD cases (3833 BD I [2676 with psychosis, 850 without psychosis, and 307 with unknown psychosis history], 1436 BD II, 579 SAB, and 505 BD not otherwise specified) and 8656 controls. CNV burden and a polygenic risk score (PRS) for schizophrenia were used to evaluate the relative contributions of rare and common variants to risk of BD, BD subtypes, and psychosis. RESULTS: CNV burden did not differ between BD and controls when treated as a single diagnostic entity. However, burden in SAB was increased relative to controls (p = .001), BD I (p = .0003), and BD II (p = .0007). Burden and schizophrenia PRSs were increased in SAB compared with BD I with psychosis (CNV p = .0007, PRS p = .004), and BD I without psychosis (CNV p = .0004, PRS p = 3.9 × 10-5). Within BD I, psychosis was associated with increased schizophrenia PRSs (p = .005) but not CNV burden. CONCLUSIONS: CNV burden in BD is limited to SAB. Rare and common genetic variants may contribute differently to risk for psychosis and perhaps other classes of psychiatric symptoms.

Systematic Analysis and Biomarker Study for Alzheimer's Disease.

Revealing the relationship between dysfunctional genes in blood and brain tissues from patients with Alzheimer's Disease (AD) will help us to understand the pathology of this disease. In this study, we conducted the first such large systematic analysis to identify differentially expressed genes (DEGs) in blood samples from 245 AD cases, 143 mild cognitive impairment (MCI) cases, and 182 healthy control subjects, and then compare these with DEGs in brain samples. We evaluated our findings using two independent AD blood datasets and performed a gene-based genome-wide association study to identify potential novel risk genes. We identified 789 and 998 DEGs common to both blood and brain of AD and MCI subjects respectively, over 77% of which had the same regulation directions across tissues and disease status, including the known ABCA7, and the novel TYK2 and TCIRG1. A machine learning classification model containing NDUFA1, MRPL51, and RPL36AL, implicating mitochondrial and ribosomal function, was discovered which discriminated between AD patients and controls with 85.9% of area under the curve and 78.1% accuracy (sensitivity = 77.6%, specificity = 78.9%). Moreover, our findings strongly suggest that mitochondrial dysfunction, NF-κB signalling and iNOS signalling are important dysregulated pathways in AD pathogenesis.

Genome-wide significant locus for Research Diagnostic Criteria Schizoaffective Disorder Bipolar type.

Studies have suggested that Research Diagnostic Criteria for Schizoaffective Disorder Bipolar type (RDC-SABP) might identify a more genetically homogenous subgroup of bipolar disorder. Aiming to identify loci associated with RDC-SABP, we have performed a replication study using independent RDC-SABP cases (n = 144) and controls (n = 6,559), focusing on the 10 loci that reached a p-value <10-5 for RDC-SABP in the Wellcome Trust Case Control Consortium (WTCCC) bipolar disorder sample. Combining the WTCCC and replication datasets by meta-analysis (combined RDC-SABP, n = 423, controls, n = 9,494), we observed genome-wide significant association at one SNP, rs2352974, located within the intron of the gene TRAIP on chromosome 3p21.31 (p-value, 4.37 × 10-8 ). This locus did not reach genome-wide significance in bipolar disorder or schizophrenia large Psychiatric Genomic Consortium datasets, suggesting that it may represent a relatively specific genetic risk for the bipolar subtype of schizoaffective disorder.

Novel ATP2A2 mutations in a large sample of individuals with Darier disease.

Darier disease (DD) is a rare autosomal dominantly inherited skin disorder caused by mutations in ATP2A2, which is expressed in both the skin and the brain and encodes for SERCA2. We have screened the coding regions of ATP2A2 in a total of 95 unrelated individuals with DD to identify the pathogenic mutations. We identified 66 potentially pathogenic mutations in ATP2A2 for 74 of the 95 individuals with DD of which 45 (68%) are thought to be novel. Forty-nine (74%) are unique to an individual and 17 (26%) were found in more than one individual or overlap with previously identified variants. The results suggest that mutations in ATP2A2 may not be as family-specific as first thought. The spectrum of mutations identified will inform understanding of the pathogenesis of DD.

Identification of a CACNA2D4 deletion in late onset bipolar disorder patients and implications for the involvement of voltage-dependent calcium channels in psychiatric disorders.

The GWAS-based association of CACNA1C with bipolar disorder (BPD) is one of the strongest genetic findings to date. CACNA1C belongs to the family of CACN genes encoding voltage-dependent calcium channels (VDCCs). VDCCs are involved in brain circuits and cognitive processes implicated in BPD and schizophrenia (SZ). Recently, it was shown that rare copy number variations (CNVs) are found at an increased frequency in SZ and to a lesser extent also in BPD, suggesting the involvement of CNVs in the causation of these diseases. We hypothesize that CNVs in CACN genes can influence the susceptibility to BPD, SZ, and/or schizoaffective disorder (SZA). A search for CNVs in eight CACN genes in a patient-control sample of European decent was performed. A total of 709 BP patients, 645 SZ patients, 189 SZA patients, and 1,470 control individuals were screened using the Multiplex Amplicon Quantification (MAQ) method. We found a rare, partial deletion of 35.7 kb in CACNA2D4 in two unrelated late onset bipolar I patients and in one control individual. All three deletions shared the same breakpoints removing exons 17-26 of CACNA2D4, comprising part of the CACHE domain. Based on the data we cannot claim causality to BPD of the identified CACNA2D4 deletion but nevertheless this deletion can be important in unraveling the underlying processes leading to psychiatric diseases in general and BPD in particular.

Variation at the GABAA receptor gene, Rho 1 (GABRR1) associated with susceptibility to bipolar schizoaffective disorder.

We have previously reported evidence that variation at GABA(A) receptor genes is associated with susceptibility to bipolar disorder with schizophrenia-like psychotic features (Research Diagnostic Criteria (RDC) schizoaffective disorder, bipolar type) with gene-wide significance at GABRB1, GABRA4, GABRB3, GABRA5, and GABRR3. Here we provide suggestive evidence implicating a sixth member of the gene family, GABRR1 (gene-wide P = 0.0058; experiment-wide corrected significance P = 0.052).

Rare copy number variants: a point of rarity in genetic risk for bipolar disorder and schizophrenia.

CONTEXT: Recent studies suggest that copy number variation in the human genome is extensive and may play an important role in susceptibility to disease, including neuropsychiatric disorders such as schizophrenia and autism. The possible involvement of copy number variants (CNVs) in bipolar disorder has received little attention to date. OBJECTIVES: To determine whether large (>100,000 base pairs) and rare (found in <1% of the population) CNVs are associated with susceptibility to bipolar disorder and to compare with findings in schizophrenia. DESIGN: A genome-wide survey of large, rare CNVs in a case-control sample using a high-density microarray. SETTING: The Wellcome Trust Case Control Consortium. PARTICIPANTS: There were 1697 cases of bipolar disorder and 2806 nonpsychiatric controls. All participants were white UK residents. MAIN OUTCOME MEASURES: Overall load of CNVs and presence of rare CNVs. RESULTS: The burden of CNVs in bipolar disorder was not increased compared with controls and was significantly less than in schizophrenia cases. The CNVs previously implicated in the etiology of schizophrenia were not more common in cases with bipolar disorder. CONCLUSIONS: Schizophrenia and bipolar disorder differ with respect to CNV burden in general and association with specific CNVs in particular. Our data are consistent with the possibility that possession of large, rare deletions may modify the phenotype in those at risk of psychosis: those possessing such events are more likely to be diagnosed as having schizophrenia, and those without them are more likely to be diagnosed as having bipolar disorder.

Affective temperaments across the bipolar-unipolar spectrum: examination of the TEMPS-A in 927 patients and controls.

OBJECTIVE: There is currently a great deal of interest in the use of affective temperaments as possible intermediate phenotypes for bipolar disorder. However, much of the literature in this area is conflicting. Our aims were to test the hypothesis of a gradient in affective temperament scores, as measured by the Temperament Evaluation of Memphis, Pisa, Paris and San Diego (TEMPS-A), from bipolar disorder type I (BP-I), through bipolar disorder type II (BP-II), recurrent major depressive disorder (MDD-R), and a control group (CG) in the largest sample to date of 927 subjects. METHODS: Non parametric tests were used to compare TEMPS-A scores between diagnostic groups and multinomial logistic regression was used to test the association between TEMPS-A scores and diagnosis while controlling for current mood state, age and gender. RESULTS: Although the BP-II group scored higher than the BP-I and MDD-R groups on several TEMPS-A subscales, these differences were not significant when confounding variables were controlled for. The dysthymic subscale differentiated between affected and controls and the anxious subscale differentiated the MDD-R group from controls. LIMITATIONS: The cross-sectional design did not allow us to evaluate potential longitudinal changes of temperament scores, which were assessed only with a self-report questionnaire. CONCLUSION: We failed to find evidence of a gradient in affective temperament scores. Both unipolar and bipolar patients reported high dysthymic scores relative to controls, perhaps supporting a unitary view of depression across the bipolar-unipolar spectrum. Taking account of potential confounders will be important in future studies which seek to use affective temperaments as intermediate phenotypes in genetic research.

Gene ontology analysis of GWA study data sets provides insights into the biology of bipolar disorder.

We present a method for testing overrepresentation of biological pathways, indexed by gene-ontology terms, in lists of significant SNPs from genome-wide association studies. This method corrects for linkage disequilibrium between SNPs, variable gene size, and multiple testing of nonindependent pathways. The method was applied to the Wellcome Trust Case-Control Consortium Crohn disease (CD) data set. At a general level, the biological basis of CD is relatively well known for a complex genetic trait, and it thus acted as a test of the method. The method, known as ALIGATOR (Association LIst Go AnnoTatOR), successfully detected biological pathways implicated in CD. The method was also applied to a meta-analysis of bipolar disorder, and it implicated the modulation of transcription and cellular activity, including that which occurs via hormonal action, as an important player in pathogenesis.

P2RX7: A bipolar and unipolar disorder candidate susceptibility gene?

The chromosomal region 12q24 has been previously implicated by linkage studies of both bipolar disorder and unipolar mood disorder and we have reported two pedigrees segregating both bipolar disorder and Darier's disease that show linkage across this region. The gene P2RX7 is located in this chromosomal region and has been recently reported as a susceptibility gene for bipolar disorder and unipolar depression. The non-synonymous SNP rs2230912 (resulting in amino-acid polymorphism Q460R) showed the strongest association and has been postulated to be pathogenically relevant. We have investigated this gene in a large UK case-control sample (bipolar I disorder N = 687, unipolar recurrent major depression N = 1,036, controls N = 1,204). Neither rs2230912 nor any of 8 other SNPs genotyped across P2RX7 was found to be associated with mood disorder in general, nor specifically with bipolar or unipolar disorder. Further, sequencing of our two chromosome 12-linked bipolar-Darier families showed no evidence of rare variants at P2RX7 that could explain the linkage. Our data do not provide support for rs2230912 or the other polymorphisms studied within the P2RX7 locus, being involved in susceptibility to mood disorders.

Collaborative genome-wide association analysis supports a role for ANK3 and CACNA1C in bipolar disorder.

To identify susceptibility loci for bipolar disorder, we tested 1.8 million variants in 4,387 cases and 6,209 controls and identified a region of strong association (rs10994336, P = 9.1 x 10(-9)) in ANK3 (ankyrin G). We also found further support for the previously reported CACNA1C (alpha 1C subunit of the L-type voltage-gated calcium channel; combined P = 7.0 x 10(-8), rs1006737). Our results suggest that ion channelopathies may be involved in the pathogenesis of bipolar disorder.

Association scan of 14,500 nonsynonymous SNPs in four diseases identifies autoimmunity variants.

We have genotyped 14,436 nonsynonymous SNPs (nsSNPs) and 897 major histocompatibility complex (MHC) tag SNPs from 1,000 independent cases of ankylosing spondylitis (AS), autoimmune thyroid disease (AITD), multiple sclerosis (MS) and breast cancer (BC). Comparing these data against a common control dataset derived from 1,500 randomly selected healthy British individuals, we report initial association and independent replication in a North American sample of two new loci related to ankylosing spondylitis, ARTS1 and IL23R, and confirmation of the previously reported association of AITD with TSHR and FCRL3. These findings, enabled in part by increased statistical power resulting from the expansion of the control reference group to include individuals from the other disease groups, highlight notable new possibilities for autoimmune regulation and suggest that IL23R may be a common susceptibility factor for the major 'seronegative' diseases.

Variation at the DAOA/G30 locus influences susceptibility to major mood episodes but not psychosis in schizophrenia and bipolar disorder.

CONTEXT: Variation at the DAOA/G30 locus has been described to be associated with both schizophrenia and bipolar disorder, but there is little consistency between studies of the tested polymorphisms or variants showing association. OBJECTIVES: To obtain a stringent replication of association in large samples of both disorders using consistent clinical and laboratory methods, and to test the hypothesis that association at DAOA/G30 identifies an underlying domain of psychopathological abnormalities that cuts across traditional diagnostic categories. DESIGN: A systematic study of polymorphisms at DAOA/G30 using genetic case-control association analysis. SETTING: Subjects were unrelated and ascertained from general psychiatric inpatient and outpatient services. PARTICIPANTS: White persons from the United Kingdom meeting criteria for DSM-IV schizophrenia (n = 709) or bipolar I disorder (n = 706) and 1416 ethnically matched controls. METHODS: Nine polymorphisms that tag common genetic variations at DAOA/G30 were genotyped in all of the individuals, and comparisons were made between affected and unaffected individuals. RESULTS: We identified significant association (P = .01-.047) between 3 single-nucleotide polymorphisms and bipolar disorder but failed to find association with schizophrenia. Analyses across the traditional diagnostic categories revealed significant evidence (P = .002-.02) for association with 4 single-nucleotide polymorphisms in the subset of cases (n = 818) in which episodes of major mood disorder had occurred (gene-wide P = .009). We found a similar pattern of association in bipolar cases and in schizophrenia cases in which individuals had experienced major mood disorder. In contrast, we found no evidence for association in the subset of cases (n = 1153) in which psychotic features occurred (all P>.08). CONCLUSIONS: Despite being originally described as a schizophrenia susceptibility locus, our data suggest that variation at the DAOA/G30 locus does not primarily increase susceptibility for prototypical schizophrenia or psychosis. Instead, our results imply that variation at the DAOA/G30 locus influences susceptibility to episodes of mood disorder across the traditional bipolar and schizophrenia categories.

Genetic variation of brain-derived neurotrophic factor (BDNF) in bipolar disorder: case-control study of over 3000 individuals from the UK.

BACKGROUND: Brain-derived neurotrophic factor (BDNF) influences neuronal survival, proliferation and plasticity. Three family-based studies have shown association of the common Valine (Val) allele of the Val66Met polymorphism of the BDNF gene with susceptibility to bipolar disorder. AIMS: To replicate this finding. METHOD: We genotyped the Val66Met polymorphism in our UK White bipolar case-control sample (n=3062). RESULTS: We found no overall evidence of allele or genotype association. However, we found association with disease status in the subset of 131 individuals that had experienced rapid cycling at some time (P=0.004). We found a similar association on re-analysis of our previously reported family-based association sample (P < 0.03, one-tailed test). CONCLUSIONS: Variation at the Val66Met polymorphism of BDNF does not play a major role in influencing susceptibility to bipolar disorder as a whole, but is associated with susceptibility to the rapid-cycling subset of the disorder.

Operation of the schizophrenia susceptibility gene, neuregulin 1, across traditional diagnostic boundaries to increase risk for bipolar disorder.

CONTEXT: Family and twin data suggest that, in addition to susceptibility genes specific for bipolar disorder or schizophrenia, genes exist that contribute to susceptibility across the traditional kraepelinian divide. Several studies have provided evidence that variation at the neuregulin 1 (NRG1) gene on chromosome 8p12 influences susceptibility to schizophrenia. The most consistent finding has been that one particular haplotype (the "core" haplotype) is overrepresented in cases compared with control subjects. OBJECTIVE: To investigate the possible role of NRG1 in bipolar disorder. DESIGN: Genetic case-control association analysis. SETTING: Subjects were unrelated and ascertained from general psychiatric inpatient and outpatient services. PARTICIPANTS: Five hundred twenty-nine patients with DSM-IV bipolar I disorder and 1011 controls from the United Kingdom (100% white). METHODS: We genotyped the markers constituting the NRG1 core haplotype in cases and controls and reanalyzed our existing data from 573 DSM-IV schizophrenia cases with this larger set of controls. RESULTS: We found a significant difference in haplotype distribution between bipolar cases and controls globally (P = .003) and specifically for the core haplotype. Frequencies were 10.2% for bipolar cases and 7.8% for controls (effect size, as measured by odds ratio [OR], 1.37; 95% confidence interval [CI], 1.03-1.80; P = .04). The effect size in our bipolar sample was similar to that in our schizophrenia sample (OR, 1.22; 95% CI, 0.92-1.61). In the bipolar cases with predominantly mood-incongruent psychotic features (n = 193), the effect was greater (OR, 1.71; 95% CI, 1.29-2.59; P = .009), as was the case in the subset of schizophrenia cases (n = 27) who had experienced mania (OR, 1.64; 95% CI, 0.54-5.01). CONCLUSIONS: Our findings suggest that neuregulin 1 plays a role in influencing susceptibility to bipolar disorder and schizophrenia and that it may exert a specific effect in the subset of functional psychosis that has manic and mood-incongruent psychotic features.

Bipolar disorder and polymorphisms in the dysbindin gene (DTNBP1).

BACKGROUND: Several studies support the dysbindin (dystrobrevin binding protein 1) gene (DTNBP1) as a susceptibility gene for schizophrenia. We previously reported that variation at a specific 3-locus haplotype influences susceptibility to schizophrenia in a large United Kingdom (UK) Caucasian case-control sample. METHODS: Using similar methodology to our schizophrenia study, we have investigated this same 3-locus haplotype in a large, well-characterized bipolar sample (726 Caucasian UK DSM-IV bipolar I patients; 1407 ethnically matched controls). RESULTS: No significant differences were found in the distribution of the 3-locus haplotype in the full sample. Within the subset of bipolar I cases with predominantly psychotic episodes of mood disturbance (n = 133) we found nominally significant support for association at this haploptype (p < .042) and at SNP rs2619538 (p = .003), with a pattern of findings similar to that in our schizophrenia sample. This finding was not significant after correction for multiple testing. CONCLUSIONS: Our data suggest that variation at the polymorphisms examined does not make a major contribution to susceptibility to bipolar disorder in general. They are consistent with the possibility that DTNBP1 influences susceptibility to a subset of bipolar disorder cases with psychosis. However, our subset sample is small and the hypothesis requires testing in independent, adequately powered samples.

Mutational analysis of two positional candidate susceptibility genes for bipolar disorder on chromosome 12q23-q24: phenylalanine hydroxylase and human LIM-homeobox LHX5.

OBJECTIVES: In the search for chromosome 12 genes potentially involved in the pathogenesis of bipolar disorder we will screen Phenylalanine hydroxylase and human LIM-homeobox LHX5 genes for sequence variants, both of which have been suggested as candidate genes. The genes lie on chromosome 12q23-24, near the Darier's disease gene, ATP2A2. We have previously reported two families in which the pattern of segregation of illness is consistent with genetic linkage between this chromosomal region and a putative highly penetrant autosomal dominant major affective disorder locus (pedigree 324, maximum LOD=2.1; pedigree 5501, maximum LOD=3.6). METHODS: We screened the coding and intronic flanking regions of the phenylalanine hydroxylase and LHX5 genes for sequence variation by denaturing high-performance liquid chromatography in individuals from the pedigrees. RESULTS: In total, nine single nucleotide polymorphisms and one 6 base pair deletion were identified. CONCLUSION: Our studies allowed us to conclude that none of these variants act as a highly penetrant autosomal dominant susceptibility locus for mood disorder in our families.