New candidate genes for bipolar disorder: evidence from two Scandinavian association studies

Abstract

Bipolar disorder (BD) has a complex and important genetic component. Many genes, each with a small effect, are believed to interact with each other and with environmental factors, to confer susceptibility to the disorder. Recent whole genome analyses (WGA)s have found association between DGKH, PALB2, MYO5B, ANK3, CACNA1C and BD. We wanted to replicate these findings in a Scandinavian sample. There was no significant association between single nucleotide polymorphisms (SNP)s in DGKH and BD in a sample comprising 594 cases and 1421 controls. This result was in accordance with other recent findings and makes it more unlikely that DGKH is a major susceptibility gene for BD. In a replication study of PALB2 association to BD, we found some evidence to support an association to BD in our Scandinavian sample. This was followed by investigations of BRCA2, a gene which function is closely related to that of PALB2, were we found a stronger and significant association to BD. These findings may give support to the hypothesis of common risk/protective genetic variants for cancer and psychiatric disorders.