A follow-up report of a genome search for affective disorder predisposition loci in the Old Order Amish.

Progress of a full-genome scan for predisposition loci for affective disorder in the Old Order Amish is reported. LOD-score results have been previously published for 51 loci on chromosomes 1 and 11, collectively. The present report contains results for an additional 367 loci throughout the genome with extensive coverage on chromosomes 1, 2, 3, 4, 6, 7, 9, 10, 13, 14, 18, 19, and 21 (average marker density for these chromosomes = 10.7 cM). Analyses were conducted in a four-stage process: (1) two-point LOD scores were calculated for all loci under a dominant model with reduced penetrance, consistent with results of segregation analyses of these pedigrees; (2) a screen for the sharing of alleles in similarly affected individuals was used to highlight areas potentially important for further analysis; (3) the preceding areas and markers on densely covered chromosomes were analyzed using the affected-pedigree-member (APM) method; and (4) the sharing of extended haplotypes in affected individuals was examined in areas showing apparent clustering of significant allele sharing as assessed by the APM method. Of the 367 markers analyzed, no statistically significant LOD scores resulted. Some degree (P < .05) of allele sharing was found at 74 loci, and 3.8% of all markers analyzed (N = 14) passed more stringent significance criteria suggestive of linkage (P < or = .001 for at least one of the weighting functions). Multilocus APM and detailed exploration of extended haplotype sharing in areas highlighted by the APM analyses provided methods for more informative exploration of potentially suggestive results but did not identify areas clearly involved in the etiology of affective disorder in this population.