Killer genes

Many people unknowingly harbor a cerebral time bomb: an intracranial aneurysm, or abnormal bulge in a brain artery. Most of the time, the aneurysm causes no obvious trouble -- but rarely, and often without warning, it ruptures. Such hemorrhagic strokes occur in about 28,000 people per year, kill 60 percent of victims within a month -- some within minutes -- and leave only one-third of survivors free of brain damage. (Vice president elect Joe Biden, who had surgery to repair two burst aneurysms in 1988, was one of the lucky ones.)

About two percent of the population have intracranial aneurysms. High blood pressure and smoking put people at risk, but the condition also tends to run in families. Now, Murat Gunel, professor of neurosurgery and neurobiology, and his colleagues have identified three areas of the human genome associated with intracranial aneurysm. The discovery paves the way for future diagnostic tests. It may also be the beginning of an explanation for the disease.

Gunel's team studied genetic information in blood samples of over 10,000 Finnish, Japanese, and Dutch patients, about one-fifth of whom had aneurysms. (The study appears in the December issue of Nature Genetics.) They found three abnormalities that were more frequent in people with aneurysms. Normally, Gunel suspects, these sections of the genome may be involved somehow in keeping blood vessels healthy.

"We think that age-related diseases might be happening because of failure of these repair mechanisms," says Gunel. "It opens a huge new area of research" -- and perhaps a way to prevent damage.