Impaired proliferation and precocious activation of Myogenin in p38-γ–deficient satellite cells. (A) Proliferation analysis of wild-type and p38-γ^−/− satellite cells. Cells were seeded at the same density (10⁵), and cells on separate plates were dissociated and counted every 24 h for 3 d. Error bars represent ±SEM for n = 3. (B and C) Real-time RT-PCR for myogenin, Myod, Myf5, Pax7, and p38-γ transcripts from wild-type and p38-γ^−/− satellite cells. RNA was extracted from satellite cells immediately after isolation (B) or after several days in culture (C). Error bars represent ±SEM for n = 7–9. Asterisks denote significance (P < 0.008). (D) Immunoblot analysis of Myogenin protein expression from proliferating and differentiating wild-type and p38-γ^−/− satellite cell–derived myoblasts. Tubulin was used as a loading control.