Figure 5

MD6.0-lacZ reporter and endogenous MyoD differ in response to activity. A, Immunoreactivity of MyoD (red) and Syndecan-4 (green) in single fibres isolated from five day denervated or contralateral control EDL muscles. Note rise in MyoD in the small nuclei of Syndecan-4⁺ satellite cells (arrows) after denervation. Large fibre nuclei (arrowheads) also have more MyoD after denervation. B, Expression of MyoD protein in activated satellite cell (arrow) and fibre (arrowhead) nuclei after three days culture in vitro (upper panels). In situ hybridisation for MyoD mRNA (lower panels; and protein, inset) in fibres from an innervated EDL muscle immediately after isolation (con) or after five days floating culture in vitro (5 div) in a well without Matrigel coating. C, Myotubes derived from TA/EDL of P0 MD6.0-lacZ mice were allowed to mature in differentiation medium for 11 days (con) or treated for the final four days with medium supplemented with 10 mM KCl (KCl) to induce depolarization. Cultures were analysed by X-gal staining (blue).