Uncovering the Number and Clonal Dynamics of Mesp1 Progenitors during Heart Morphogenesis

The heart arises from distinct sources of cardiac progenitors that independently express Mesp1 during gastrulation. The precise number of Mesp1 progenitors that are specified during the early stage of gastrulation, and their clonal behavior during heart morphogenesis, is currently unknown. Here, we used clonal and mosaic tracing of Mesp1-expressing cells combined with quantitative biophysical analysis of the clonal data to define the number of cardiac progenitors and their mode of growth during heart development. Our data indicate that the myocardial layer of the heart derive from ~250 Mesp1-expressing cardiac progenitors born during gastrulation. Despite arising at different time points and contributing to different heart regions, the temporally distinct cardiac progenitors present very similar clonal dynamics. These results provide insights into the number of cardiac progenitors and their mode of growth and open up avenues to decipher the clonal dynamics of progenitors in other organs and tissues. Chabab et al. show that about 250 Mesp1 cardiac progenitors specified during gastrulation contribute to heart myocardium morphogenesis. Distinct subpopulations of Mesp1 progenitors, emerging at different time points during development and leading to the formation of different regions of the heart, share similar proliferative capacities.SCOPUS: ar.j