FLICKR, MARCO CASTELLANI
At least half of schizophrenia patients who have no family history of the disorder harbor de novo mutations, according to research published online on Sunday (August 7) in Nature Genetics, suggesting genetics may play a role even when the disease is not inherited. Specifically, researchers sequenced the exomes, or protein-coding DNA, of 53 patients with seemingly non-inherited cases of schizophrenia—meaning they had no immediate family members nor aunts, uncles, nieces, nephews or grandparents who had the disease—as well as 22 unaffected individuals and the parents of these subjects. In 27 of the schizophrenia patients, they identified 40 new mutations in 40 different genes, including one in DGCR2, a gene located in a region of chromosome 22 known to be associated with schizophrenia.
"The fact that the mutations are all from different genes is particularly fascinating,” lead researcher Maria Karayiorgou of Columbia University in New York told the BBC. "It suggests that many more mutations than we suspected may contribute to schizophrenia."
The reason so many different genes carried new mutations likely stems from the fact that the disease is so complex and involves a variety of genetic pathways, providing a large target for mutations. This, combined with the high rate of mutations that affected protein structure and function, could explain why the disease is so common, affecting about one in every 100 people, the authors said.