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
"(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.