Biphasic Development of the Mammalian Ventricular Conduction System

Rationale: The ventricular conduction system controls the propagation of electric activity through the heart to coordinate cardiac contraction. This system is composed of specialized cardiomyocytes organized in defined structures including central components and a peripheral Purkinje fiber network. How the mammalian ventricular conduction system is established during development remains controversial. Objective: To define the lineage relationship between cells of the murine ventricular conduction system and surrounding working myocytes. Methods and Results: A retrospective clonal analysis using the α-cardiac actinnlaacZ/+ mouse line was carried out in three week old hearts. Clusters of clonally related myocytes were screened for conductive cells using connexin40-driven enhanced green fluorescent protein expression. Two classes of clusters containing conductive cells were obtained. Mixed clusters, composed of conductive and working myocytes, reveal that both cell types develop from common progenitor cells,...