Distinct phases of Wnt/β-catenin signaling direct cardiomyocyte formation in zebrafish

► Wnt/b-catenin signaling is used reiteratively during heart development. ► We examine the roles of Wnt signaling in cardiac cell formation in zebrafish. ► Wnt signaling in pre-cardiac mesoderm prevents cardiac cell differentiation. ► Increased Wnt signaling in pre-cardiac mesoderm leads to cell death. ► Wnt signaling later promotes atrial cell differentiation.