The finding could benefit African-Americans by making it possible to detect who is at increased risk for developing arrhythmia and allowing those affected to take preventive measures. The study is one of the first in which researchers have been able to discern how genetics influences arrhythmia risk across a range of populations of people who originated from different geographic regions.

In an article published in the August 23, 2002, issue of the journal Science, the research team led by HHMI investigator Mark T. Keating reported that 13.2 percent of African-Americans in the study carried an altered form of the gene SCN5A. This gene codes for a protein called a sodium channel, a molecular pore that initiates heartbeats by allowing sodium to flow across the membrane of the cardiac muscle cell.

The variant form of the gene creates sodium channels in heart muscle cells that remain open longer than normal sodium channels, prolonging contraction of the heart and contributing to arrhythmia. Keating authored the paper with colleagues at Harvard Medical School, the University of Utah, Columbia University and St. George's Hospital Medical School in London.

Keating emphasized that although arrhythmias are serious disorders, the effect of the gene variant is subtle. "People who have this gene variant are not likely to have an arrhythmia," he said. "All of us harbor gene variants that we may not know about. Fortunately, our hearts are remarkably well buffered against such problems, and arrhythmias are rare. What's often required for a dangerous arrhythmia is that several things go wrong at the same time
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
22-Aug-2002