Genome screening for linkage disequilibrium in a Costa Rican sample of patients with bipolar-I disorder: A follow-up study on chromosome 18

Linkage disequilibrium (LD) methods offer great promise for mapping complex traits, but have thus far been applied sparingly. In this paper we describe an LD mapping study of severe bipolar disorder (BP‐I) in the genetically isolated population of the Central Valley of Costa Rica. This study provides the first complete screen of a chromosome for a complex trait using LD mapping and presents the first application of a new LD mapping statistic (ancestral haplotype reconstruction (AHR)) that evaluates haplotype sharing among affected individuals. The results of this chromosome‐wide analysis are instructive for genome‐wide LD mapping in isolated populations. Furthermore, the analysis continues to support a possible BP‐I locus on 18pter, suggested by previous analyses in this population. Evidence for a possible BP‐I locus on 18q12.2 is also described. © 2001 Wiley‐Liss, Inc.