Figure 6. Myoblast proliferation is enhanced by a loss of Abl2.

(A,B) In vivo labeling of E13.5-E14.5 diaphragm muscles shows that EdU incorporation is greater in Abl2^−/− myoblasts than wild type (wt) myoblasts. (C) Representative images of cultured diaphragm cells stained with MyoD to label myoblasts, DAPI to label all cells and EdU to label proliferating cells. (D) At initial plating, a similar number of MyoD⁺ cells are isolated from Abl2^−/− and wild type mice. (E) Cultured MyoD⁺ myoblasts from Abl2^−/− diaphragm muscles showed increased EdU incorporation. (F) In contrast, non-muscle cells (MyoD⁻) from Abl2 mutant and wild type mice proliferate at similar rates. (G) Abl2 heterozygous myoblasts proliferated at a rate that was intermediate between wild type and Abl2 homozygous mutant myoblasts. (H) Representative images of cultured diaphragm cells stained with MyoD to label myoblasts, DAPI to label all cells, and phospho-Histone H3 (pHH3), a marker for mitotic cells. (I) MyoD⁺ myoblasts, cultured from the diaphragm muscle of Abl2^−/− mice, showed a greater percentage of mitotic figures than myoblasts isolated from wild type mice. *p=0.1, **p<0.05, ****p<0.001.

Figure 6—figure supplement 1. The number of Pax7⁺cells is increased in proportion to the increased length of myofibers.

Serial cross-sections of the diaphragm were stained with antibodies to Laminin to outline muscle fibers and with antibodies to Pax7 to label satellite cells. The number of Pax7⁺ cells was divided by the total number of muscle fibers in each visual field. Longer muscle fibers in Abl2^−/− mice have proportionally more Pax7⁺ cells. The graph shows the mean (±s.d.) number of Pax7⁺ cells in serial cross sections from three mice in each group. Scale bar is 50 µm.