Dysbindin gene variants are associated with bipolar I disorder in a Korean population

The dysbindin gene (DTNBP1) has been associated with schizophrenia in several populations. Because the clinical characteristics of schizophrenia and bipolar disorder overlap in many respects and findings from genetic studies have suggested common genes between them, we conducted a case control association study of bipolar disorder in Korea to investigate the genetic association between DTNBP1 and bipolar disorder. In total, 163 patients with bipolar disorder and 350 controls were evaluated. We genotyped three single nucleotide polymorphisms of DTNBP1 (SNP A, P1763, and P1320) and analyzed the allele, genotype, and haplotype associations with bipolar disorder. We found significant genotypic associations with P1763 and P1320, but no association with SNP A in the bipolar I group. When we included bipolar II and schizoaffective disorder in the affected phenotype, the significance decreased. A positive association was observed between the SNP A-P1763 haplotype and the bipolar I phenotype. This haplotype association was lost when we either broadened our phenotype or included P1320 in a haplotype. The positive results of the present study lost significance after a Bonferroni correction for multiple testing. These findings are consistent with previous findings that showed a positive association of DTNBP1 with bipolar disorders. Moreover, our results suggest that DTNBP1 may contribute more to bipolar I disorder than bipolar II disorder or schizoaffective disorder. Further comprehensive studies will be required to clarify these association, however, it seems likely that DTNBP1 is a susceptibility gene for bipolar disorder.