Notch Activation Commits Mesoderm Cells to the Cardiac Lineage [cardiomyocytes]

During early development multiple progenitor populations contribute to the formation of the four-chambered heart and its diverse lineages. However, the underlying mechanisms that result in the specification of these progenitor populations are not yet fully understood. We have recently identified a population of cells that gives rise selectively to cardiovascular cells of the heart ventricles. Here, we have used this knowledge to isolate and profile subsets of cardiac mesoderm cells from the mouse embryo and have identified an enrichment for the Notch signaling pathway in ventricular cardiac mesoderm. Using the pluripotent stem cell differentiation system to investigate the role of Notch in a temporally controlled manner, we show that Notch induction increases cardiomyocyte differentiation efficiency. This is due to the enhanced specification of mesoderm to the cardiac lineage. Finally, our data suggests that Notch interacts with WNT signaling to enhance commitment to the cardiac lineage. Overall, our findings support the notion that key signaling events during early heart development are critical for proper lineage specification and segregation and provide additional detail into these processes in mouse and human cardiogenesis. Overall design: Examination of global gene expression in day 30 cardiomyocytes from control, Notch-induced, and Notch-inhibited cardiac mesoderm cultures.