Fig. 10. Hand1 regulates cardiomyocyte proliferation versus differentiation in vitro via G1 cell-cycle progression or exit. (A) Myocardial beating in embryoid bodies (differentiated for up to 14 days) derived from wild-type (+/+), Hand1-null (-/-), control (responder transgene alone, co) and Hand1-overexpressing (oe) ES-cell lines. (B) Quantitative real-time PCR analysis on RNA extracted from embryoid bodies following 14 days of differentiation, for an array of cardiac markers. (C) Western blots of day-14 EBs using antibodies for cyclin D2, Cdk4 and Gapdh. (D) Quantification of protein levels from C normalised to Gapdh using scanning densitometry.