Fig. 3

,Reduced muscle fiber caliber and MuSC proliferation in Fmr1^-/- mice. a Cryo-sections (20 μm) of adult tibialis anterior muscle isolated from wild-type (WT, left) and Fmr1^-/- mice (right) immunolabelled with laminin (red) and nuclei counterstained with DAPI (blue): myofibers show reduced diameter in Fmr1^-/- muscle. b Left panel shows qRT-PCR quantification of mRNA encoding Fmrp isolated from whole muscle of adult WT and Fmr1^-/- mice. Values represent mean + SEM; n = 2, two-tailed paired Student’s t test is indicated. ** p < 0.01. Fmr1 RNA is detectable at lower levels in Fmr1^-/- as described [30, 38, 39]. Right panel: quantification of mean myofiber cross-sectional area (CSA) in wild-type and Fmr1^-/- muscle cryosections. Values represent mean + SD; n = 250. CSA from two mice. Two-tailed unpaired Student’s t test is indicated. *** p value < 0.0001, (N = 2 male mice per genotype). c–d. Muscle stem cells isolated from Fmr1^-/- mice do not proliferate well in culture. c The proportion of VCAM⁺, CD45^- MuSC is similar in adult WT and Fmr1^-/- mice. However, there is a noticeable reduction in the VCAM^-, CD45⁺ cells suggesting effects on the leukocyte compartment. d Equal numbers of FACS purified MuSC isolated from the hind limb muscle of adult WT and Fmr1^-/- mice were plated in culture for 0 or 6 days. Fmr1^-/- cells show poor population expansion (N = 1 male mouse per genotype)