Fig. 3. Signals from the medial dermomyotome downregulate Wnt6 expression. (A) Removal of the whole dermomyotome leads to the upregulation of Wnt6 expression in the ectoderm overlying the somites (arrowhead). (B) Removal of the medial region of the dermomyotome is sufficient to upregulate Wnt6 expression (arrowhead). (C,D) Transverse section across the operated region of embryos shown in A,B, respectively, showing a lateromedial extension of ectodermal Wnt6 expression (medial extent indicated by arrowheads). (E) Grafting of a medial dermomyotomal lip to the segmental plate, and in situ hybridization against Wnt11. Although no endogenous Wnt11 expression is detectable yet, the graft shows solid Wnt11 expression (arrowhead). (F) Transverse section showing the loss of Wnt6 expression in the ectoderm covering the paraxial mesoderm after grafting medial dermomytomal lip from quail to the segmental plate (arrowheads; asterisk marks a region on the control side slightly damaged during sectioning). (G) Presence of the quail-derived graft shown in F marked by QCPN antibody. (H) Implantation of Wnt3a-producing cells into the somites leads to the upregulation of Wnt11 expression (arrowheads). (I) Transverse section at the operated site of the embryo shown in H. Wnt11 expression is upregulated in the medial dermomyotomal lip (arrowhead); the position of the implanted cells is indicated by a broken line.