Novel insights into the cellular basis of atrial fibrillation.

Atrial fibrillation is the most common clinical cardiac arrhythmia. It is often initiated by ectopic beats arising from the pulmonary veins and atria. While pulmonary vein myocytes most likely contribute to atrial ectopic beats initiating atrial fibrillation, emerging evidence suggests the existence of other cell populations that may also contribute to atrial arrhythmias. In addition to sinus node-like and intestinal Cajal-like cells, we recently characterized a novel, melanocyte-like cell population in murine and human hearts that may contribute to atrial arrhythmogenic triggers in mice. Murine cardiac melanocyte-like cells are electrically excitable, and express adrenergic and muscarinic receptors. Adult mice lacking the gene encoding dopachrome tautomerase (Dct) are susceptible to atrial arrhythmias, and Dct is expressed by both murine and human cardiac melanocytes. While Dct-expressing cells are present in human hearts in regions from which atrial arrhythmias often arise, the contribution of these cells to clinical atrial arrhythmias remains to be determined.