Fig. 6. Gene expression domains in E10.5 Ednra^+/+ (top) and Ednra^–/– (bottom) embryos. The sketches illustrate a ventral view of the mandibular arch, with the orientation of each arch half depicted above. Color-coded keys define both mesenchymal and epithelial gene expression domains. (A) In wild-type (Ednra^+/+) embryos, the overlapping expression domains of Dlx5 and Dlx6 are shown on the left-hand side, while the right side depicts Msx1, Dlx2, Twist and Gata3 expression domains. Epithelial expression of Fgf8, Dlx2 and Edn1 are also shown on both sides. In Ednra^–/– embryos, expression of both Dlx5 and Dlx6 is disrupted in the arch mesenchyme, as is Dlx2 expression in the rostral arch epithelium. By contrast, mesenchymal expression domains of Msx1, Dlx2 and Twist expand either proximally or distally, creating a large region of overlap. The Gata3 expression domain appears unchanged. (B) Hand2 expression is shown in two domains: one that requires Ednra signaling and one that does not require Ednra signaling.