Genome-wide supported risk variant for bipolar disorder alters anatomical connectivity in the human brain.

Bipolar disorder is a devastating, highly heritable mental disorder related to disturbed connectivity between limbic and frontal brain areas. A meta-analysis of genome-wide association studies as well as independent replications showed ankyrin 3 (ANK3) to be one of the best-supported risk genes for bipolar disorder. Using an imaging genetics approach employing diffusion tensor imaging in 88 healthy volunteers, we show decreased white matter integrity, indicated by lower fractional anisotropy and longitudinal diffusivity, in healthy carriers of the ANK3 rs10994336 risk genotype in the anterior limb of the internal capsule. We are also able to show that the resulting alterations of cortical-striatal-thalamic circuits are related to impaired set-shifting and increased risk-taking. For risk-allele carriers of ANK3 rs9804190 no white matter alterations or neuropsychological impairments were observed. In sum, our findings show that ANK3 rs10994336 or a variant in linkage-disequilibrium is functional in the human brain and also influences behavioral phenotypes related to bipolar disorder.