Figure 6

Later-forming fibres do not accumulate slow MyHC in response to Shh. Dorsal muscle mass from contralateral (A-C) and operated (D-F) wing implants grown to HH30 and stained for Pan MyHC (MF20, A,D) and slow MyHC (Na8, B,E) after in situ hybridisation for Shh mRNA (C,F). Shh mRNA is widespread in the dorsal muscle mass, which is expanded and poorly split (A,D). In contralateral muscle most slow fibres are in the medial region of the dorsal/posterior muscle block (B). In the operated limb, slow MyHC is more abundant in the dorsal region, with numerous cells in ectopic lateral locations (arrows, E). Note that the ventral region of the dorsal muscle mass has few if any ectopic slow fibres.