In the two recent separate studies, researchers examined caveolin-3 (CAV3) and the cardiac ryanodine receptor (RyR2) and found molecular and functional evidence in both to implicate them as SIDS-susceptibility genes. Researchers examined the tissue of 135 unrelated cases of SIDS -- in infants with an average age of 3 months old -- that had been referred to Mayo Clinic's Sudden Death Genomics Laboratory for molecular autopsy. In each study, two of the 135 cases possessed mutations in either CAV3 or RyR2.
SIDS -- the sudden, unexplained death of an infant under 1 year old -- is estimated to cause 2,500 infant deaths each year. "Combined with our previous discoveries, we now estimate that defects in genes that provide the blueprints for the critical controllers of the heart's electrical system might have played a key role in more than 300 of those tragedies," says Michael J. Ackerman, M.D., Ph.D., principal investigator of both studies and director of Mayo Clinic's Long QT Syndrome Clinic and Sudden Death Genomics Laboratory. "We are continuing to expose the causes of SIDS. So far, we have now added six genes to the SIDS most-wanted list."
In 2001, a team of investigators led by Dr. Ackerman identified the first cardiac gene, SCN5A, linked to SIDS. In 2005, a comprehensive search of the five channel genes that cause a potentially lethal heart rhythm syndrome known as long QT syndrome (LQTS) was found in 5 percent to 10 percent of SIDS cases.