Fig. 2. Correlation of Wnt expression with muscle differentiation. (A) A sketch through the dorso-ventral axis of a stage 24 wing bud showing the relationship between Wnt expression and the developing myogenic cells. Initially, Wnt7a is expressed throughout the dorsal ectoderm but, by stage 24, its expression is restricted to the dorsal ectoderm overlying the progress zone. (B) Transverse section through an 8-day limb showing the expression of slow MyHC (orange) versus fast MyHC (green). (C) Diagrammatic sketch of (B). ANC, anconeus; EDC, extensor digitorum communis; EIL, extensor indicis longus; EMR, extensor metacarpi radialis; EMU, extensor metacarpi ulnaris; Ent, entepicondyloulnaris; FCU, flexor carpi ulnaris; PP, pronator profundus; PS, pronator superficialis; SUP, supinator.