Srf loss within SCs does not affect their proliferation but impairs their motility. (A) control and Srf mutant plantaris muscle section immunostained for Pax7 (green), laminin (magenta), and nuclear staining with DAPI 1 wk after CH. Yellow arrows indicate Pax7-expressing SCs. (B) Number of Pax7⁺ cells per myofiber in control and mutant plantaris muscle sections before (SO) and after 1, 3, and 5 wk of CH (n = 7–12 muscles from n = 4–7 mice). (C) Normalized percentage of EdU⁺ cells in control and mutant FACS-sorted SCs cultured in rich medium for 5 d (n = 8–5 mice). (D) Percentage of PH3⁺ cells in control and mutant FACS-sorted SCs cultured in rich medium for 5 d (n = 3–4 mice). (E) Mean velocity (micrometers per minute) of control and mutant MBs determined by time-lapse videomicroscopy (one representative experiment). Data are means ± SEM. *, P < 0.05; **, P < 0.01.