Expression of ErbB receptors in ES cell-derived cardiomyocytes

To explore the role of ErbB-mediated signaling in cardiogenesis of ES cells, we examined the expression of ErbB receptors as well as effects of a ligand and inhibitors using Nkx2.5GFP ES cells, in which the GFP gene was knocked-in to the Nkx2.5 locus to monitor cardiac differentiation. Although all ErbB receptors were expressed in developing embryoid bodies, expression of ErbB4 was almost exclusively found in differentiated cardiomyocytes. Heregulin beta1, a ligand of ErbB receptors, enhanced the generation of Nkx2.5/GFP(+) cardiomyocytes in embryoid bodies, while AG1478 and PD153035, inhibitors of ErbBs, drastically blocked the generation of Nkx2.5/GFP(+) cardiomyocytes. These results suggest that the signaling pathway mediated by ErbBs is important in the induction and differentiation of cardiomyocytes from ES cells.