Fig. 1: Erk1/2 are required for satellite cell viability upon activation.

a Western blot analysis for the indicated proteins using tibialis anterior (TA) lysate from samples taken at baseline (Base.) and following 3, 7 and 14 days (d) after cardiotoxin (CTX) administration. Results from two different mice are shown. b Schematic representation of breeding of Mapk3^−/− and Mapk1-loxP(f)-targeted mice with the Pax7^Cre-ERT2 mouse as well as with the Cre-dependent R26eGFP reporter mouse. c Schematic showing the timing of tamoxifen (Tmx) and CTX treatments in 2-month-old mice. d Representative images of TA muscle sections from mice of the indicated genotypes stained with H&E (left panels), anti-myosin antibody (MF-20, green) and anti-laminin antibody (red, middle panels) or with anti-Pax7 antibody (green, right panels) 10 days post-CTX injury. Scale bars = 100 μm. Samples from 3 different mice were analyzed. e Experimental scheme showing mice injected with Tmx for 3 days, then with CTX on day 4, followed by 3 more days of Tmx injections. f Representative histological sections showing eGFP fluorescence (green) and immunostained for laminin (red) 4 days post-CTX injection in mice of the indicated genotypes. Nuclei are stained with Dapi (blue). Scale bar = 100 μm. Samples from 3 different mice were analyzed. g Schematic representation of the Tmx treatment regimen. Two-week-old mice received Tmx injections for 5 consecutive days and were placed on Tmx chow after weaning. h Quantification of Pax7⁺ satellite cells from uninjured TA muscle sections from mice of the indicated genotypes. n = 3 mice per group. Significance was determined using a two-tailed Student’s t test, ***P < 0.001. i Schematic representation of Tmx treatment. Two-month-old mice received daily Tmx injection for 5 consecutive days and were subsequently placed on Tmx chow for 10 months. j Quantification of satellite cell numbers from uninjured TA muscle sections from 1-year-old mice of the indicated genotypes. n = 3 mice per group. Significance was determined using a two-tailed Student’s t test, **P = 0.005. Data represent mean ± SEM for all graphs.