Researchers studying North Americans can't confirm first risk gene linked to stroke

Saturday, February 07, 2004

An interim analysis of data from a major, North American study of ischemic stroke failed to confirm the presence of a risk gene previously found in the Icelandic population. The data comes from the "Siblings With Ischemic Stroke Study" (SWISS), an ongoing, multicenter study of sibling pairs who've suffered ischemic strokes.

Last year scientists at deCODE genetics, a population-based genomics company, found the first gene believed to confer susceptibility to ischemic stroke. Ischemic stroke is one of two major types of stroke. It happens when a blocked blood vessel deprives brain tissue of oxygen and nutrients.

Studying the DNA of people in Iceland, deCODE scientists identified an association between a variant of the gene PDE4D and increased risk of ischemic strokes due to atherosclerosis, the buildup of plaque inside an artery causing narrowing of the blood vessel. PDE4D is located on the region of chromosome 5 called the STRK1 locus.

After studying the DNA of the first 100 sibling pairs participating in SWISS, researchers could not find a major gene affecting stroke risk at the STRK1 locus.

"It's really odd," says principal investigator Dr. James Meschia, a neurologist from Mayo Clinic in Jacksonville. "Our study is ongoing, but this result highlights the importance of validating in the U.S. population initial discoveries made elsewhere." He says volunteers in studies such as SWISS are invaluable in that effort.

Meschia says it's possible the at-risk variant of the PDE4D gene found in the Icelandic population isn't widely distributed in the United States because the American population is much more genetically diverse. Iceland, on the other hand, has a fairly homogeneous population due to centuries of geographic isolation.

Meschia presented this data from SWISS at the American Stroke Association's 29th International Stroke Conference Feb. 5-7 in San Diego. SWISS is sponsored by the National Institute of Neurological Disorders and Stroke.

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