Myogenic property of iSkM progenitor cells generated from MEFs. (a) Representative expression of M-cadherin analyzed by FACS in MEFs (upper), mixture of MEFs and iSkM progenitor cells (middle), and purified iSkM progenitor cells (lower). n > 3 for each group. (b) Numbers of M-cadherin-positive cells generated by exogenous expression of Pax3, Mef2b, and Pitx1 or Pax7, Mef2b, and Pitx1. n = 6. (c) Immunocytochemical analysis of Pax3, Pax7, Myf5, MyoD, and Myogenin in iSkM progenitor cells. Scale bar: 200 µm. n = 6. (d) Expression of exogenous genes in iSkM progenitor cells. n = 6. (e) Endogenous expression of several muscle marker genes in iSkM progenitor cells, MEFs, cultured SCs, and myotubes. n = 6. (f) Representative immunostaining of MyHC and myogenin in iSkM cells 4 days after induction of differentiation. n > 6. Scale bar: 200 µm. (g) Co-culture of GFP–cSCs (GFP: green) and iSkM progenitor cells (Kusabira-Orange: red) showing formation of GFP/Kusabira-Orange-double-positive myotubes. n > 6. Scale bar: 200 µm. (h) Representative images of Dystrophin-positive myofibers in iSkM progenitor cell from MEFs-transplanted mdx mice. Scale bar: 100 µm. (i) Quantitative analysis of numbers of Dystrophin-positive fibers in transplanted tibialis anterior/extensor digitorum longus muscles. n = 4–6. Error bars indicate SEM. *P < 0.05, **P < 0.01, ***P < 0.001 by Student’s t-test in (b), or by ANOVA with Tukey–Kramer test in (e,i).