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New genetic risks for schizophrenia identified

Results from a multistage genome-wide association study have identified 13 new risk loci for schizophrenia, a discovery that may pave the way to a more complete understanding of the genetic component of the disorder.

Patrick F. Sullivan, MD, of the University of North Carolina School of Medicine, and colleagues first analyzed genome-wide single nucleotide polymorphism (SNP) data from a Swedish national sample of 5,001 patients with schizophrenia and 6,243 controls, followed by a meta-analysis of existing data from the Psychiatric Genomics Consortium that included 8,832 schizophrenia cases and 12,067 controls. Finally, the researchers obtained replication results for SNPs in 168 genomic regions in independent samples of 7,413 schizophrenia cases, 19,762 controls and 581 parent–offspring trios. Nearly 60,000 patients were included in the entire study.

 

Patrick F. Sullivan

According to the researchers, 22 loci were significantly associated with schizophrenia. Thirteen of these loci are new discoveries, and one locus, NCAN, has been implicated in bipolar disorder. Further examination of these loci indicated that two pathways may play a role in the etiology of schizophrenia. The first is a calcium channel pathway that includes the genes CACNA1C and CACNB2, which have been associated with five major psychiatric disorders. The second pathway — microRNA 137 — is responsible for neuronal development.

The researchers estimated that genetic influences accounted for at least 32% of the risk for schizophrenia. Thousands of loci, they said, may contribute to the heritability of the disorder. However, identifying all of them would be "an exercise in diminishing returns." Instead, Sullivan and colleagues proposed the identification of 2,000 loci responsible for schizophrenia risk, which would be sufficient to provide a clear picture of the biological processes behind schizophrenia.

"What's really exciting about this is that now we can use standard, off-the-shelf genomic technologies to help us fill in the missing pieces," Sullivan said in a press release. "We now have a clear and obvious path to getting a fairly complete understanding of the genetic part of schizophrenia. That wouldn't have been possible 5 years ago."

Disclosure: See the study for a full list of financial disclosures.