Functional genetic variation at the NRGN gene and schizophrenia: evidence from a gene-based case-control study and gene expression analysis.

Genome-wide association and follow-up studies have reported an association between schizophrenia and rs12807809 of the NRGN gene on chromosome 11q24.2. We investigated the association of five linkage disequilibrium-tagging SNPs and haplotypes that cover the NRGN gene with schizophrenia in a Japanese sample of 2,019 schizophrenia patients and 2,574 controls to determine whether rs12807809 is the most strongly associated variant for schizophrenia in the vicinity of the NRGN gene. We found that the rs12807809-rs12278912 haplotype of the NRGN gene was associated with schizophrenia (global P = 0.0042). The frequencies of the TG and TA haplotypes of rs12807809-rs12278912 in patients were higher (OR = 1.14, P = 0.0019) and lower (OR = 0.85, P = 0.0053), respectively, than in the controls. We did not detect any evidence of association of schizophrenia with any SNPs; however, two nominal associations of rs12278912 (OR = 1.10, P = 0.057) and rs2075713 (OR = 1.10, P = 0.057) were observed. Furthermore, we detected an association between the rs12807809-rs12278912 haplotype and NRGN expression in immortalized lymphoblasts derived from 45 HapMap JPT subjects (z = 2.69, P = 0.007) and confirmed the association in immortalized lymphoblasts derived from 42 patients with schizophrenia and 44 healthy controls (z = 3.09, P = 0.002). The expression of the high-risk TG haplotype was significantly lower than the protective TA haplotype. The expression was lower in patients with schizophrenia than in controls; however, this difference was not statistically significant. This study provides further evidence of the association of the NRGN gene with schizophrenia, and our results suggest that there is a link between the TG haplotype of rs12807809-rs12278912, decreased expression of NRGN and risk of developing schizophrenia.