The degree to which cKit-expressing progenitors generate cardiomyocytes in the heart is controversial. Genetic fate-mapping studies suggest minimal contribution; however, whether or not minimal contribution reflects minimal cardiomyogenic capacity is unclear because the embryonic origin and role in cardiogenesis of these progenitors remain elusive. Using high-resolution genetic fate-mapping approaches with cKit(CreERT2/+) and Wnt1::Flpe mouse lines, we show that cKit delineates cardiac neural crest progenitors (CNC(kit)). CNC(kit) possess full cardiomyogenic capacity and contribute to all CNC derivatives, including cardiac conduction system cells. Furthermore, by modeling cardiogenesis in cKit(CreERT2)-induced pluripotent stem cells, we show that, paradoxically, the cardiogenic fate of CNC(kit) is regulated by bone morphogenetic protein antagonism, a signaling pathway activated transiently during establishment of the cardiac crescent, and extinguished from the heart before CNC invasion. Together, these findings elucidate the origin of cKit(+) cardiac progenitors and suggest that a nonpermissive cardiac milieu, rather than minimal cardiomyogenic capacity, controls the degree of CNC(kit) contribution to myocardium.
Keywords: BMP signalling; cardiac neural crest; cardiac stem cells; cardiomyogenesis.