15 April 2009
By Julie Steenhuysen
The study is the first to identify common genetic variants influencing stroke risk in the United States and may lead to better treatments, they reported on Wednesday.
While other stroke–related genes have been discovered, none involved such a wide portion of the population, said Eric Boerwinkle of The University of Texas Health Science Center.
“This is a first step in unraveling the genetic contributions of this debilitating disease,” said Boerwinkle, whose team was one of several contributing to the study published in the New England Journal of Medicine.
Stroke is the third–leading cause of death in the United States and causes serious long–term disabilities for many worldwide.
Boerwinkle said the teams found two genetic variants on chromosome 12 near two genes that are implicated in stroke. One, called WNK1, is associated with blood pressure control and the other, NINJ2, is linked with brain injury repair.
The two genes, next to each other, both are also strongly linked with ischemic stroke, which is the most common type of stroke and is caused by blocked blood vessels in the brain.
Boerwinkle said it is not clear which specific gene is implicated, but he said the most likely suspect is NINJ2.
They found two single–letter changes in the DNA, known as single nucleotide polymorphisms or SNPs – pronounced “snips” –near NINJ2 that seem to send the strongest stroke “signal.” One is found in about 20 percent of whites they checked and 10 percent of African–Americans.
Having just one copy of this genetic variation can raise the risk of ischemic strokes by about 30 percent, he said – although the study says it is unlikely the SNPs are the actual cause of stroke but probably associated with the actual genetic cause.
The findings come from an analysis of the genetic code of more than 19,000 people in the United States and Europe taking part in four long–term studies of cardiovascular risks.
The teams were looking for SNPs among 1,544 people who had strokes, compared with 18,058 people who did not.
Boerwinkle said more work needs to be done to sort out which genes are at play, but he said the findings should give drug companies a new target for researching better treatments.
Dr. Walter Koroshetz, deputy director of the U.S. National Institute of Neurological Disorders and Stroke, which supported the study, said the findings are not strong enough to alter a patient's stroke prevention strategy.
But he said the results “will lead scientists to direct their attention to new, important biologic mechanisms and hopefully new treatments to prevent stroke.”