Fig. 1. Regulation of Pax3, Zic1 and Foxd3 expression in early Xenopus embryos. (A-C) The expression of Pax3 (A), Zic1 (B) and Foxd3 (C) at the early neurula stage as analyzed by whole-mount in situ hybridization. (D-F) Double-labeled in situ hybridization at the neurula stage (stage 15). (D) Pax3 (light blue) and Foxd3 (magenta); (E) Zic1 (light blue) and Foxd3 (magenta); (F) Pax3 (magenta) and Zic1 (light blue). (G-N) Effects of BMP and Wnt signals on Pax3, Zic1 and Foxd3 expression. Synthetic mRNAs of CA-BMPR (50 pg/cell; G-I), dnBMPR (200 pg/cell; J-L) or Wnt3a (10 pg of DNA/cell; M,N) were injected into two left animal blastomeres at the eight-cell stage. Whole-mount in situ hybridization was performed with Pax3 (G,J,M), Zic1 (H,K) and FoxD3 (I,L,N) probes. Arrows in J-N indicate ectopic expression of each marker gene; arrowheads in F indicate the Pac3⁺/Zic1⁺ area.