Bipolar disorder is a major psychiatric disorder characterized by extreme mood states that alternate between mania and depression. Family, twin, and adoption studies indicate a genetic component to the disease, but the etiology is suspected to be complex, with multiple genes contributing to an increased susceptibility to the disorder. We have previously reported a genome scan in which a genome-wide maximum LOD score indicated evidence of linkage at the marker D22S278 at 22q13. This area is of particular interest since it is also implicated in schizophrenia, and thus may harbor a susceptibility gene common to both disorders. In our further efforts to fine map this region, we examined 10 microsatellite markers spanning an interval of 2.3 MB in a set of 142 parent–proband triads. Linkage disequilibrium to illness was tested using the Transmission Disequilibrium Test. Haplotypes were determined and marker-to-marker linkage disequilibrium across the region was examined. D22S281 and D22S685 yielded suggestive evidence of linkage disequilibrium to bipolar disorder (empirical P values of 0.023 and 0.036, respectively), but a marker-to-marker analysis indicates that a higher density screen is needed to adequately analyze this region.
aDepartment of Psychiatry, University of California, San Diego and San Diego VA Healthcare System, La Jolla, California, USA
bDepartment of Medical Genetics, University of British Columbia, Vancouver, Canada
cDepartment of Psychiatry, St Paul's Hospital, Vancouver, Canada
dDepartment of Psychiatry, University of Cincinnati, Cincinnati, Ohio, USA
Correspondence to John R. Kelsoe, Department of Psychiatry 0603, University of California, San Diego, La Jolla, CA 92093, USA. E-mail: firstname.lastname@example.org
Received 31 August 2001; accepted 22 January 2002