Analysis of chromosome 18 DNA markers in multiplex pedigrees with manic depression

Six pedigrees segregating manic-depressive illness (MDI) were analyzed for linkage to 21 highly polymorphic microsatellite DNA markers on chromosome 18. These markers span almost the entire length of the chromosome, and gaps between markers are less than 20 cM. In particular, we analyzed several markers localizing to the pericentromeric region of chromosome 18 which generated lod scores suggestive of linkage in an independent study. Lod score analysis was performed and results were examined by family. One region produced positive lod scores, though at 18q23 and not in the pericentromeric region. We additionally used two nonparametric methods because the true mode of transmission of MDI is unknown; results were again somewhat suggestive for markers in the region of 18q23 but not in the pericentromeric region.