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Schizophrenia Linked to Rare, Often Unique Genetic Glitches
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The model emerging from the new study is quite different. It says most cases of schizophrenia may be caused by rare genetic glitches that are individually potent.
The turnaround is the result of sophisticated gene scans conducted on 233 schizophrenics, including 83 who got the disease in childhood, a more serious condition. The scans looked for rare stretches of DNA where more than 100,000 "letters" of genetic code were either missing or mistakenly present in duplicate.
About 15 percent of schizophrenics, and 20 percent of those affected in childhood, had such glitches, compared with 5 percent of healthy individuals who were also studied. Yet the glitches, including one previously associated with autism, were different in each person.
Unlike previous scans based on older technology, which could at best find general genomic "neighborhoods" where mutations associated with schizophrenia are present, the new scans pinpointed the individual genes affected.
"It's fabulous to be able to find these mutations directly rather than indirectly," said Mary-Claire King, a geneticist at the University of Washington who was on the team. "You just go for the jugular."
The genes implicated are diverse, but many are known to play crucial roles in how the brain gets wired early in life. Normally that process starts with a huge overproduction of neurons, followed by a controlled winnowing that leaves only those that have made proper connections.
"Changes in these genes could bias the way circuits get sculpted out and could perhaps lead to a brain in which signals that would normally get filtered out don't get filtered out," which could interfere with thinking and prompt hallucinations, Insel said.
The delayed onset of the disease can be explained by the fact that some genes and brain connections do not take on central roles until young adulthood, said Jonathan Sebat of Cold Spring Harbor Laboratory, one of the study leaders.
"Genes have timing," Sebat said. "They follow developmental programs for where and when they're going to be active."
