DNA Brain

DNA variants linked to schizophrenia, bipolar

CARDIFF U. (UK) — Researchers have found new molecular evidence that 11 genetic regions have strong links to schizophrenia and bipolar disorder, including six regions not previously observed.

The researchers also found that many of these DNA variations contribute to both diseases.

The findings, reported by the Psychiatric Genome-Wide Association Study Consortium (PGC), represent significant advances in these severe and debilitating disorders. Scientists believe they can start to link the genetic variations to the breakdown of specific brain functions which causes both diseases

The findings, based on genetic data from tens of thousands of patients, have just been published online in two papers in the journal Nature Genetics.

“The genetic variants we have identified are common in the population—everyone carries many of them, but people with the disorders carry more,” says Michael O’Donovan, a psychiatry professor and one of three researchers at Cardiff University involved in the international study.

“The success of this study demonstrates the need for international co-ordination in harnessing data from very large samples to exploit the power of genetics to reveal new insights,” add O’Donovan. “Over the next two years we expect to have data from study samples that are three or four times larger than those we have now, and this can be expected to have the same impact for our research as ever more powerful particle accelerators have had in physics.”

Michael Owen, a psychiatry professor at Cardiff and study co-author, says it may be a few years before scientists are able to see a larger part of the genetic picture. “However, for the first time, we are in a position to make tentative functional links between some of the genes identified.

“One particularly exciting finding is the involvement of a type of molecule, known as a microRNA, which acts as a molecular switch to turn off other genes. This microRNA is also known to regulate aspects of the development and maturation of nerve cells in the brain. The findings suggest disruption of these development processes as likely factors in the origins of mental disorder,” says Owen.

Both schizophrenia and bipolar disorder usually strike in late adolescence or early adulthood. Some of the most prominent symptoms in schizophrenia are persistent delusions, hallucinations, and cognitive problems.

Bipolar disorder (or manic-depressive illness) is characterized by episodes of severe mood problems including mania and depression. Despite the availability of treatments, these illnesses are usually chronic and  often lead to prolonged disability and personal suffering.

Family history is a strong risk factor for both disorders. The new findings are further evidence for the general assumption that dozens of genes, along with environmental factors, contribute to disease risk.

The Psychiatric Genome-Wide Association Study Consortium is the largest consortium ever in psychiatry, involving more than 250 researchers from more than 20 countries.

The effort is supported by the National Institute of Mental Health (US). The Cardiff research also was supported by the Wellcome Trust, the European Union, and the National Institute for Social and Healthcare Research (UK).

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