Figure 5

(A) The proportion of fast MyHC myotubes is decreased in Igf-2 deficient mice (maternal disomy Chromosome 7 - MatDi) at E14.5 compared to WT sibling controls (Student t-test, p = 0.06). By E15.5 there is an overall drop of 50% in the proportion of fast MyHC in MatDi embryos compared to WT (statistically significant by Student t-test, p = 0.03). (B) Embryo immunoblotting for Igf-2 demonstrates a stage related increase in Igf-2 protein between E10.5 and E15.5 in WT and absence of Igf-2 in MatDi embryos at E14.5 and E15.5 Tracks 1–4 E10.5, E13.5, E14.5 and E15.5 WT embryos respectively, Track 5 E14.5 MatDi, Track 6 E15.5 MatDi and Track 7 E15.5 WT. (C) In some Mat Di muscles fast MyHC staining is almost entirely abolished compared (D) to WT siblings in which over half of myotubes at this stage contain fast MyHC. In the posterior insertional region of the diaphragm, the intensity of staining and number of fast MyHC positive skeletal myotubes at E15.5 is, (E) decreased in maternal disomy mutant embryos (19% fast MyHC positive myotubes) compared to (F) litter mate controls (MatDi Con 38% fast MyHC myotubes). Magnification bars represent 10 microns.