Fig. 3: Proliferation is blunted in Myc-depleted MuSCs and muscle regeneration is strongly impaired in Pax7-MyckO mice.

A Schematic and (B) representative images of isolated single fibers from Pax7-eGFP and Pax7-MycKO mice either fixed immediately (0 h) or cultured for 48 h (48 h) and then stained for eGFP, Pax7 and Ki67 (n = 4). C Percentage of eGFP+ MuSC cells expressing Ki67. D Percentage of eGFP+ MuSC cells in cluster sizes of 1, 2, 3-4 and 5+ . E Schematic of cardiotoxin (CTX) experiment in CON and Pax7-MycKO mice. F TA Muscle mass 4, 7 and 14 days after CTX injury in CON (n = 6, 7, 8) and Pax7-MycKO mice (n = 7, 6, 5) normalized to uninjured contralateral TA mass. G Fiber type proportion for eMHC, IIB and unstained fibers (IIA/X) 14 days after CTX injury in CON (n = 4) and Pax7-MycKO (n = 5) TA cross-sections. H Representative images showing immunostaining for embryonic myosin heavy chain (eMHC; magenta), type IIB (green) and laminin (white) at 4, 7 and 14 days post CTX injury and (I) mean minimum fiber feret size at 14 days in CON (n = 4) and Pax7-MycKO (n = 5) TA cross-sections. J Pax7+ and (K) MyoG+ cell number in TA muscle sections, via immunostaining, 4 (n = 4–5), 7 (n = 3-4) and 14 (n = 3–5) days after CTX injury in CON and Pax7-MycKO mice normalized to cross-sectional area. Uninjured samples represent pooled, un-injected contralateral legs from all time points (CON, n = 13–14; KO, n = 11–12). A, E Created in BioRender. Ruegg, M. (2025) https://BioRender.com/d74q573. Data are presented as mean ± SEM. Two-tailed, Student’s independent t tests (I) or two-way ANOVAs with Sidak’s post hoc test were used to compare between conditions. *, **, and *** denote a significant difference between groups of P  <  0.05, P  <  0.01, and P  <  0.001, respectively.