Common variants on chromosome 6p22.1 are associated with schizophrenia

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Abstract
A genome-wide association study using the Molecular Genetics of Schizophrenia case-control data set, followed by a meta-analysis that included over 8,000 cases and 19,000 controls, revealed that while common genetic variation that underlies risk to schizophrenia can be identified, there probably are few or no single common loci with large effects. The common variants identified here lie on chromosome 6p22.1 in a region that includes a histone gene cluster and several genes implicated in immunity. In the third of three papers looking at the genetics of schizophrenia, a genome-wide association study using the Molecular Genetics of Schizophrenia case-control data set followed by a meta-analysis further implicates the major histocompatibility complex. The study also reveals that although common schizophrenia susceptibility alleles can be detected, there are probably few or no single common loci with large effects. Schizophrenia, a devastating psychiatric disorder, has a prevalence of 0.5–1%, with high heritability (80–85%) and complex transmission1. Recent studies implicate rare, large, high-penetrance copy number variants in some cases2, but the genes or biological mechanisms that underlie susceptibility are not known. Here we show that schizophrenia is significantly associated with single nucleotide polymorphisms (SNPs) in the extended major histocompatibility complex region on chromosome 6. We carried out a genome-wide association study of common SNPs in the Molecular Genetics of Schizophrenia (MGS) case-control sample, and then a meta-analysis of data from the MGS, International Schizophrenia Consortium and SGENE data sets. No MGS finding achieved genome-wide statistical significance. In the meta-analysis of European-ancestry subjects (8,008 cases, 19,077 controls), significant association with schizophrenia was observed in a region of linkage disequilibrium on chromosome 6p22.1 (P = 9.54 × 10-9). This region includes a histone gene cluster and several immunity-related genes—possibly implicating aetiological mechanisms involving chromatin modification, transcriptional regulation, autoimmunity and/or infection. These results demonstrate that common schizophrenia susceptibility alleles can be detected. The characterization of these signals will suggest important directions for research on susceptibility mechanisms.