Fig. 5. Co-activation of Pax3 and Zic1 in concert with Wnt signaling is essential for neural crest determination of the ectoderm in vivo. (A-F) Synthetic mRNA was injected into a ventral animal blastomere at the eight-cell stage. Embryos were harvested at stage 15 for in situ hybridization with Foxd3 (A,C,E) or Slug (B,D,F) probes. A higher magnification view is shown in the right half of each panel. Pax3 and Zic1 mRNA injection with lacZ mRNA (A-F; ß-gal activity was visualized by incubating with Red-Gal), ß-catenin-MO (Gene Tools; 10 ng/cell; C-F), and ß-catenin (50 pg of DNA/cell; E,F).