Fig. 2.

FMRP is required for efficient priming of muscle stem cells to rapidly activate the myogenic program, self-renewal, and differentiation. a Fraction of PAX7(+) satellite cells accumulating MYF5 (left) and MYOD (right) after 1 h culture of single EDL myofibers. b Representative immunostaining of PAX7 (green) and MYOD (red) on single EDL myofibers isolated from adult wild-type and Fmr1 ^−/− mice after 48 h culture. c Numbers of satellite cells undergoing self-renewal (PAX7+MYOD−), activating the myogenic program (PAX7+MYOD+) and differentiating (PAX7−MYOD+) on single EDL myofibers isolated from adult wild-type (white) and Fmr1 ^−/− (gray) mice after 2-day culture. d Levels of MyoD, Myog, and Myh3 transcripts, relative to Actb, in satellite cells isolated from adult muscle of wild-type (wt, black) and Fmr1 ^−/− (gray) mice, after 4-day culture. e Levels of MYOG protein, relative to ACTB, from cell lysates of 4-day cultured satellite cells isolated from muscle of wt (black) and Fmr1 ^−/− (white) mice. Representative immunoblot is shown. MYOG levels are calculated by densitometry of three immunoblots. f Levels of Pax7 and Myf5 transcripts, relative to Actb, in satellite cells isolated from adult muscle of wild-type (wt, black) and Fmr1 ^−/− (gray) mice, 2 days after ctx injury. g Representative images of EdU(+) MyoD(+) satellite cells present on transverse sections of TA muscle, 3 days after ctx injury. White arrows indicate MYOD(+) EdU(+) satellite cells. Scale bar, 50 μm. h Fraction of MYOD(+) satellite cells that are EdU(+), as indicated in g. All values indicate mean (n ≥ 3) ± s.e.m. *p < 0.05, ***p < 0.001