Three papers in Nature provide new insights into genetic variation and schizophrenia risk. Using combined data from three large cohorts, the papers jointly reveal significant associations to individual loci that implicate immunity, cognition and brain development. Additionally, one of the papers provides genetic evidence for a substantial polygenic component to risk of schizophrenia that also contributes to risk of bipolar disorder.
Pamela Sklar and the International Schizophrenia Consortium show that common genetic variation underlies risk of schizophrenia. Their study identifies common variants within the major histocompatibility complex (MHC) locus, and provides molecular genetic evidence for a substantial polygenic component to risk of schizophrenia that involved thousands of common alleles of very small effect. These alleles of small effect also contribute to risk of bipolar disorder.
Kari Stefansson and colleagues present a genome-wide association of single nucleotide polymorphisms (SNPs) and reveal significant associations to individual loci that implicate immunity, brain development, memory and cognition in predisposition to schizophrenia.
Pablo Gejmans and the Molecular Genetics of Schizophrenia use a case-control study design to show an association between the MHC genomic locus and schizophrenia. Their results suggest a possible involvement of chromatin proteins in this disorder.
Together, by using meta-analysis of almost 10,000 cases and 20,000 controls, these three studies indicate that although common genetic variation that underlies risk to schizophrenia can be identified, there are probably few or no single common loci with large effects.
Pamela Sklar (Massachusetts General Hospital, Boston, MA, USA) Author paper 
Kari Stefansson (DeCODE Genetics, Regykjavik, Iceland) Author paper 
Pablo Gejman (NorthShore University HealthSystem Research Institute, Evanston, IL, USA) Author paper 
Abstracts available online:
Abstract of Paper 1.
Abstract of Paper 2.
Abstract of Paper 3.
(C) Nature press release.
Message posted by: Trevor M. D'Souza