ClinVar

Kakiuchi et al. (2003) used DNA microarray analysis of lymphoblastoid cells derived from 2 pairs of Japanese twins discordant for bipolar disorder (612371) to detect causative genes. In a study of 197 unrelated Japanese patients with bipolar disorder and 451 controls, they found an association between a -116C-G polymorphism in the promoter region of XBP1 and susceptibility to bipolar disorder (odds ratio = 4.6). The polymorphism occurs at the putative binding site of XBP1 and presumably interferes with the feedback loop. The concordance rate in monozygotic twins (more than 65%) is much higher than in dizygotic twins (more than 14%). Possible mechanisms of discordance between monozygotic twins include point mutations, extension of triplet repeats, chromosomal aberrations, altered X chromosome inactivation, and aberrant DNA methylation.

In a study of 153 bipolar disorder patients and 174 controls in a Chinese population, Hou et al. (2004) found no significant association between the -116C-G polymorphism and bipolar disorder (p = 0.674 for genotype and p = 0.436 for allele frequency).