Figure 7.

Inducible, skeletal muscle‐specific up‐regulation of FoxP1 impedes muscle regeneration following injury. (A–B) FoxP1 (A) and Acta1 (B) mRNA expression measured in proliferating C2C12 myoblasts (Day 0) and following 1, 2, or 5 days of differentiation into myotubes. (C–G) Tibialis anterior muscles of CRE+ FoxP1^iSkmTg/Tg mice and CRE‐ littermate controls (CON) were injured via direct injection of cardiotoxin on the same day as tamoxifen treatments were initiated. Twenty‐four days post‐injury, FoxP1^iSkmTg/Tg mice showed reduced muscle mass (C), and reduced cross‐sectional area (CSA) of regenerating myofibres, as visualized in tibialis anterior muscle cross‐sections stained with H&E (D) and as quantified in (E–G). Cross‐sectional area data were binned, fit with a Gaussian least squares regression and significance was determined by calculating the extra sum‐of‐squares F test. Statistical differences were determined by conducting one‐way ANOVAs in panels (A) and (B), and unpaired two‐tailed t‐tests or Mann–Whitney tests in panels (C) and (E). Data are reported as mean ± SEM.