Figure 4: Cardiomyocyte (CM) specific gene expression profiles, as determined by RT-PCR and immunostaining, of CM derived from mouse embryonic stem (ES) cells, Nanog induced pluripotent stem (iPS) cells, and Fbx15-iPS cells. (a) CM-associated structural protein gene expression profiles. The expression of Actn1, Myh6, Myh7, Myl7, Myl2, and Nppb was analyzed by semiquantitative RT-PCR analysis. GAPDH was used as an internal control. (b) Immunofluorescent staining of typical CM-specific proteins on day 15 of differentiation in CM derived from ES, Nanog-iPS, and Fbx15-iPS cells. Cells were stained with Nkx2.5 (green), GATA4 (green), atrial natriuretic peptide (ANP; green), myosin heavy chain (MHC; red), and -actinin (red). Scale bar = 50 μm.