Linkage analysis of a completely ascertained sample of familial schizophrenics and bipolars from Palau, Micronesia

We report on linkage analysis of a completely ascertained population of familial psychosis derived from the oceanic nation of Palau. Palau, an archipelago of islands in the Southern Pacific, currently has a population of approximately 23,000 individuals. The peoples of Palau populated these islands recently in human history, approximately 2,000 years ago. As both historical and genetic evidence suggest, the population is far more homogeneous than most other populations undergoing genetic studies, and should therefore prove quite useful for mapping genetic variants having a meaningful impact on susceptibility to psychotic disorders. Moreover, for our study, essentially all on-island schizophrenics (150) and individuals with other psychotic disorders (25) participated. By analysis of narrow (only schizophrenia) and broad (all psychosis) diagnostic schemes, two-point linkage analyses suggest that two regions of the genome harbor genetic variants affecting liability in most families, 3q28 (LOD=3.03) and 17q32.2 (LOD=2.80). Results from individual pedigrees also support 2q37.2, 2p14, and 17p13 as potentially harboring important genetic variants. Most of these regions have been implicated in other genetic studies of psychosis in populations physically quite distant from this Oceanic population, although some (e.g., 3q28) appear to be novel results for schizophrenia linkage analyses.