The Japanese Schizophrenia Sib-Pair Linkage Group (JSSLG) is a multisite collaborative study group that was organized to create a national resource for affected sib pair (ASP) studies of schizophrenia in Japan. We used a high-density single-nucleotide-polymorphism (SNP) genotyping assay, the Illumina BeadArray linkage mapping panel (version 4) comprising 5,861 SNPs, to perform a genomewide linkage analysis of JSSLG samples comprising 236 Japanese families with 268 nonindependent ASPs with schizophrenia. All subjects were Japanese. Among these families, 122 families comprised the same subjects analyzed with short tandem repeat markers. All the probands and their siblings, with the exception of seven siblings with schizoaffective disorder, had schizophrenia. After excluding SNPs with high linkage disequilibrium, we found significant evidence of linkage of schizophrenia to chromosome 1p21.2-1p13.2 (LOD=3.39) and suggestive evidence of linkage to 14q11.2 (LOD=2.87), 14q11.2-q13.2 (LOD=2.33), and 20p12.1-p11.2 (LOD=2.33). Although linkage to these regions has received little attention, these regions are included in or partially overlap the 10 regions reported by Lewis et al. that passed the two aggregate criteria of a meta-analysis. Results of the present study--which, to our knowledge, is the first genomewide analysis of schizophrenia in ASPs of a single Asian ethnicity that is comparable to the analyses done of ASPs of European descent--indicate the existence of schizophrenia susceptibility loci that are common to different ethnic groups but that likely have different ethnicity-specific effects.

Recent progress in genotyping technology and the development of public databases has enabled large-scale genome-wide association tests with diseases. We performed a two-stage genome-wide association study (GWAS) of bipolar disorder (BD) in Japanese cohorts. First we used Affymetrix 100K GeneChip arrays in the analysis of 107 cases with bipolar I disorder and 107 controls, and selected markers that were nominally significant (P < 0.01) in at least one of the three models (1,577 markers in total). In the follow-up stage, we analyzed these markers using an Illumina platform (1,526 markers; 51 markers were not designable for the platform) and an independent sample set, which consisted of 395 cases (bipolar I + II) and 409 controls. We also assessed the population stratification of current samples using principal components analysis. After the two-stage analysis, 89 markers remained nominally significant (allelic P < 0.05) with the same allele being consistently over-represented in both the first and the follow-up stages. However, none of these were significant after correction for multiple-testing by false discovery rates. Sample stratification was virtually negligible. Collectively, this is the first GWAS of BD in the Japanese population. But given the small sample size and the limited genomic coverage, these results should be taken as preliminary.

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