Expression of myogenic markers in wild-type and <i>MyoD^−/−</i> myoblast cultures.

<p>(A) Fluorescence views of myoblasts isolated from wild-type and <i>MyoD^−/−</i> mice. Immunostaining for Pax7 (green) and MyoD (red) showed that nearly all wild-type myoblasts expressed Pax7 and MyoD while <i>MyoD^−/−</i> cells expressed only Pax7 (n = 3). Scale bar = 25 µm. (B) After 3 days of culture in low serum conditions, sarcomeric myosin heavy chain (MHC) immunostaining clearly demonstrated that wild-type myoblasts differentiated into MHC⁺ myocytes and myotubes while myogenic differentiation was delayed for <i>MyoD^−/−</i> myoblasts (n = 3). Scale bar = 50 µm. (C) More than 90% of stable wild-type and <i>MyoD^−/−</i> myoblast transformants expressed nuclear lacZ after co-transfection of PGK-nlacZ-MAR/PGK-puro followed by puromycin selection. Scale bar = 50 µm. Nuclei were counter-stained with DAPI (blue).