MyoD^−/− myoblasts up-regulate Pax3 expression. (A) Under growth conditions (control [Cont]), differentiation conditions (Diff), UV exposure, or treatment with thapsigargin (Thap), Pax3, Pax7, Bcl-2, and Bcl-xL gene expression were compared between wild-type and MyoD^−/− myoblasts by RT-PCR. (B) Pax3 and Pax7 expression were compared between wild-type and MyoD^−/− myoblasts by immunostaining (green). Nuclei were counterstained with DAPI (blue). Bar, 40 µm. (C) Pax3 protein expression was compared between wild-type (wt) and MyoD^−/− myoblasts by Western blotting. (D) Relative Pax3 expression levels normalized by β-actin expression shown in C were measured. (A and C) β-Actin was monitored as a loading control. **, P < 0.01. Error bars indicate SEM.