Fig. 5. Fgf10 signaling regulates Sp8 and Sp9. Dorsal views of Sp8 expression (A,B) and Sp9 expression (C,D) in E9.5 mouse embryos. (E-H) Dorsal views of Sp8 expression in chick limb buds. (I-L) Dorsal views (I,J) and ventral views (K,L) of Sp9 expression in chick limb buds. All panels are with the anterior towards the top. (A-D) Sp8 and Sp9 expression detected in wild-type mouse embryos (A,C, black arrowheads), was significantly downregulated in Fgf10^–/– embryos (B,D, red arrowheads). Implantation of Fgf10-soaked beads upregulated chick Sp8 expression in the surface ectoderm and in the AER after 6 hours (F; compare with the contralateral control, E). Implantation of SU5402-beads downregulated expression of chick Sp8 in the AER after 24 hours (red arrowhead in H; compare with the contralateral control, G). Implantation of Fgf10-beads upregulated chick Sp9 expression in the surface ectoderm and in the AER after 6 hours (J; compare with the contralateral control, I). Implantation of SU5402-beads downregulated expression of chick Sp9 in the AER after 24 hours (red arrowhead in L; compare with the contralateral control, K). Arrowheads in E,F and I,J indicate the anterior margin of the expression domain. The asterisks in F,H,J,L indicate implanted beads.