How a recently identified gene disrupts normal heart rhythm

Washington, March 4 : An international team of researchers has for the first time found out how variants of a specific gene called CAPON can disrupt normal heart rhythm.

The new discovery by experts from the Cedars-Sinai Heart Institute, Johns Hopkins University and China Medical University and Hospital in Taiwan attains significance because CAPON was not even suspected of existing in heart tissue or playing a role in heart function until recently.

The researchers said that their study, conducted in guinea pigs, confirmed that CAPON naturally exists in the ventricles, pumping chambers of the heart. According to them, the gene interacts with a signalling molecule in heart muscle, called NOS1, to influence signalling pathways and modify cell-to-cell interactions that control electrical currents.

Cedars-Sinai Heart Institute Director Dr. Eduardo Marban, senior author of the study report, says that the effects of CAPON and its variants are seen in the "QT interval" of EKGs, which reflect electrical activity from the time the ventricles are stimulated to the end of the heart muscle activity in a single heartbeat.

Dr. Marban further says that QT interval abnormalities can represent serious heart rhythm problems, and even the risk of sudden death.

In the study report, its authors note that long and short QT syndromes can be caused by rare congenital disorders that affect the ion channels (calcium ion and potassium ion channels), but most deaths caused by sudden arrhythmias occur in people who do not have these genetic mutations.

Until recently, researchers were unable to explain the basis of QT interval abnormalities in otherwise healthy people.

In 2006, Dr. Marban and his colleagues discovered an association between QT intervals and the CAPON gene by studying the genetic makeup of individuals who had long or short QT intervals.

The study, which was reported in Nature Genetics at the relevant time, was surprising because CAPON, while known for its involvement in brain nerve cells, was not expected to exist in heart tissue.

In the current study, the researchers have confirmed the existence of CAPON in heart tissue and illuminated its effects on heart function.

"(The new) "findings provide a rationale for the association of CAPON gene variants with extremes of the QT interval in human populations," states an article on the current study, published online in Proceedings of the National Academy of Sciences.

ANI