Fig. 2. Wnt11 and En1 are expressed in distinct populations of the chick dorsal subectodermal mesenchyme in the epaxial domain. Dorsal views at HH23 of the forelimb (fo) level, and corresponding sections, hybridized with Wnt11 (A-C), En1 (D-F), Sim1 (G-I) and MyoD (J-L) probes. (A-C) Wnt11 transcripts are detected in the dorsomedial subectodermal mesenchyme. (D-F) En1 expression is detected in the dorsolateral mesenchyme. (G-I) Sim1 is detected in a few mesenchymal cells on each side of a notch (arrowhead) in the ectoderm, at the limit between the epaxial and the hypaxial domain, as well as in the Wolffian duct (Wd). (J-L) MyoD-positive cells are localized below the En1-and the Sim1-expressing cells, in the myotome (my). ec, ectoderm; dml, dorsomedial lip; nc, notochord; nt, neural tube. Scale bars: 100 µm in A,B,D,E,G,H,J,K; 50 µm for C,F,I,L.