Foxa2 identifies a novel ventricular-specific cardiac progenitor population during gastrulation.

The recent identification of novel progenitor populations that contribute to the developing heart in a distinct temporal and spatial manner has fundamentally improved our understanding of cardiac development. However, little remains known about cardiac specification events prior to the establishment of the heart tube, or the mechanisms that direct atrial versus ventricular specification. We have identified a novel progenitor population that gives rise specifically to cardiovascular cells of the ventricles but not the atria, and to the epicardium of the differentiated heart. We determined that this cell population is first specified during gastrulation, when it transiently expresses Foxa2, a gene not previously implicated in cardiac development. Using chimeric mosaic analysis we further demonstrate that Foxa2 is cell-autonomously required for the development of ventricular cells. Finally, we reveal the existence of an analogous Foxa2+ cardiac mesoderm population during in vitro differentiation from embryonic stem cells and illustrate that these cells express genes relevant for heart development. Our data thus describe the first progenitor population identified as early as gastrulation that displays ventricular-specific differentiation potential. Together, these findings provide important new insights into the developmental origin of ventricular and atrial myocytes, and will lead to the establishment of new strategies for generating these cell types from pluripotent stem cells. Overall design: Examination of global gene expression in four different cell types