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Missing DNA chunks tied to schizophrenia risk (AP)

NEW YORK - Two huge international studies show that people who lack certain chunks of DNA run a dramatically higher risk of getting schizophrenia, a finding that could help exposed strange doors to understanding and diagnosing the disease.

These deletions are rare, both found in less than 1 percent of schizophrenia patients. But each one boosts the risk of disease through as much as 15-fold, by dint of. one estimate.

Scientists said studying such abnormalities may help them find new medications by shedding light on what causes the disease. And if enough rare aberrations can be found eventually, they may be combined into a test to help in diagnosis, said Kari Stefansson, chief executive officer of deCode Genetics of Reykjavik, Iceland, and an author of one of the studies.

Schizophrenia is currently diagnosed by its symptoms.

The human DNA be possible to be thought of as a very in extent string of letters — about 3 billion of them — that sometimes form words (genes). Each newly identified deletion removes a section of about half a the masses to 2 million letters.

In the past, scientists have ground specific genes and deletions linked to schizophrenia peril. But the new work is notable because two large studies independently identified the same two DNA deletions, and those aberrations be in possession of such a tumid impact on disease risk. Stefansson’s paper also reports evidence for a third deletion.

While the DNA deletions are linked to only a tiny fraction of schizophrenia cases, it’s not unusual that a very rare cause of a disease provides insights that apply more generally, said Dr. Pamela Sklar of Massachusetts General Hospital, an author of the other paper. She said such knowledge can lead to treatments for many people.

Both papers were published online Wednesday by the journal Nature. Experts not connected with the work praised the results.

“This is frightful” for basic research into the disease, said Dr. Linda Brzustowicz of Rutgers University. But since the deletions found so far are related to such a small fraction of schizophrenia cases, she said it’s too early for companies to offer to test people for them.

Stefansson’s paper, which included authors from more than a dozen centers in the United States, Europe and China, reported findings from DNA tests in about 4,700 people with schizophrenia and greater degree than 40,000 healthy people. Sklar’s paper, which included scientists from 11 institutes in the United States, Europe and Australia, tested about 3,400 people with schizophrenia and 3,200 others.

Both papers found that while the deletions were rare in schizophrenia patients, they were even rarer in people without the disease. Scientists say the disease results from a combination of genetic predisposition and environmental influences.

The two deletions found by both inquiry groups boost schizophrenia risk 12-fold and 15-fold, Stefansson’s group calculated. A third deletion his group found appears to raise risk about threefold.

Sklar said she was “absolutely delighted” that the papers found the two deletions independently, using different methods.

Anne Pulver, a schizophrenia genetics expert at Johns Hopkins University, uttered the papers represent a welcome shift in focus for finding genetic variants that affect risk of schizophrenia.

Traditionally, that search has centered on relatively common variants, each with little effect on an individual’s hazard. The new approach seeks rare variants that play a larger role. The new approach should resist be the same subgroups of patients with different genetic causes for the sake of their disease, she said. Eventually that could lead to treatments that are tailored to the differing biological causes, with improved outcomes, she said.

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On the Net:

Nature: http://www.nature.com/nature

Information on schizophrenia: http://www.nimh.nih.gov/health/topics/schizophrenia