Eleven trinucleotide repeat loci that map to chromosome 12 excluded from involvement in the pathogenesis of bipolar disorder.

The hypothesis that one or more genes containing expanded trinucleotide repeats contribute to the pathogenesis of bipolar disorder has received support from three independent studies demonstrating that bipolar patients tend to have larger CAG/CTG repeat expansion detection products than controls. In an attempt to identify the specific expanded CAG/CTG locus or loci which are associated with bipolar disorder, we determined repeat size at CAG/CTG loci mapping to candidate regions for bipolar disorder. Recent linkage studies suggest the existence of a bipolar susceptibility gene on chromosome 12q23-q24.1 in the region of the Darier's disease (DAR) gene. In this study we report our findings from 11 loci which map to chromosome 12, including CAG repeat polymorphisms within the genes SCA2 and ASH1. We conclude that all of these loci are excluded as candidates for CAG/CTG repeat expansion in bipolar disorder.