Cardiac mesoderm induction by Tbx6 without exogenous factors. Mus musculus

Cardiac mesoderm, a precursor for all cardiovascular lineages, is a promising cell source for basic research and clinical applications. BMP/Nodal/Wnt signaling induces cardiac mesoderm in embryonic stem cells (ESCs); however the molecular mechanism is unclear and the differentiation protocols are labor-intensive. Identification of a master regulator that induces cardiac mesoderm is needed. Here we found that Tbx6 directly reprogrammed mouse fibroblasts into cardiac mesoderm-like cells, which differentiated into cardiomyocytes and smooth muscle cells with addition of lineage-specific transcription factors. In mouse ESCs, BMP/Activin (Nodal) induced Tbx6 in cardiac mesoderm, while inhibition of Tbx6 blocked differentiation into cardiac mesoderm and cardiomyocytes. Conversely, transient expression of Tbx6 induced cardiac mesoderm in ESCs without exogenous factors, and generated all cardiovascular lineages. Mechanistically, Tbx6 directly upregulated Mesp1, inhibited Sox2, and activated BMP/Nodal/Wnt signaling to induce cardiac mesoderm. Thus, Tbx6 acts as a key regulator for cardiac mesoderm induction, and our findings provide new insights into the mechanism of cardiovascular differentiation. Overall design: In this study, we compared the global gene expression patterns of iTbx6 T-GFP ESCs with or without Dox administration. RNA was extracted from embryoid body at day2 and day4 after differentiation.