Further evidence for the association between G72/G30 genes and schizophrenia in two ethnically distinct populations

Recently, the nested genes G72 and G30 on chromosome 13q32-q33 have been implicated in the etiology of schizophrenia. We genotyped six single-nucleotide polymorphisms (SNPs: rs3916965, rs3916967, rs2391191, rs778294, rs779293 and rs3918342), which span approximately 82.5 kb in the region encompassing the G72/G30 genes in 1176 Han Chinese subjects (588 cases and 588 controls) and 365 Scottish subjects (183 cases and 182 controls). Significant association between an allele of marker rs778293 and schizophrenia was found in our Chinese samples (P = 0.0013), and was replicated in the Scottish samples (P = 0.022). LD analysis revealed that four SNPs between rs3916965 and rs778294 were in LD, called block I, and the two distal SNPs (rs778293 and rs3918342) constituted a block II in both the Chinese and Scottish samples. We selected one SNP from each block (rs778294 from block I and rs778293 from block II), and then analyzed the haplotypes. A significant difference was observed for the common haplotype GC in the Chinese sample (P = 0.0145), and was replicated in the Scottish sample (P = 0.003). On meta-analysis, we separately analyzed the studies in Asian and European populations because of significant heterogeneity in the homogeneity test. We found a statistically significant association between rs778293 and schizophrenia in Asian populations, but no difference was found between cases and controls in the European populations. Overall, our data give further support to the existing evidence that G72/G30 genes are involved in conferring susceptibility to schizophrenia.

A family-based and case-control association study of the NOTCH4 gene and schizophrenia

Recently a strong positive association between schizophrenia and Notch4 has been reported. Both individual markers and haplotypes showed association with the disease, with five markers (three microsatellites and two SNPs) being tested. In order to test this finding we genotyped these markers in the Han Chinese population using a sample of 544 cases and 621 controls as well as >300 trios. Analysis of allele, genotype and haplotype frequencies in both samples showed no association between the markers and the disease. Our results would indicate that a significant role for the Notch4 gene in schizophrenia can be ruled out in the Han Chinese. However, similar studies are necessary in the Caucasian population as linkage disequilibrium arrangements and founder effects may differ between these two populations.