Expression of a two-pore domain K+ channel (TASK-1) in developing avian and mouse ventricular conduction systems.

In this study, we report the identification and amino acid sequence of a novel two-pore domain potassium channel (TASK-1) in chicken. This protein, cTASK-1, is highly similar to mouse and human TASK-1 particularly within the pore regions. We describe the expression profile of both chicken and mouse TASK-1 in the embryonic heart as the ventricular conduction system develops. The developmental distribution of TASK-1 is similar in chicken and mouse. Initially, TASK-1 is expressed throughout the myocardium of the early heart tube. However, as cardiogenesis proceeds, ventricular expression becomes restricted to the trabeculated myocardium and eventually the bundle of His, bundle branches, and Purkinje fibers of the mature conduction system. This finding suggests that components of the ventricular conduction system differentiate from TASK-1-positive myocytes of the early heart tube that retain TASK-1 expression as they mature. Our results are consistent with a common mechanism for ventricular conduction system development in avians and mammals, despite differences in the anatomy of the mature conduction systems of these organisms.