Fig. 4. Effect of FGF treatment on cdxA and cdxB expression in the neural tube. Dorsal views of stage 9 embryos hybridized with cdxA (A,B) and stage 15 embryos hybridized with cdxB (C,D). Untreated control embryos (A,C) and embryos treated for 6 hours (B) or overnight (D) with recombinant FGF2 protein in culture. In B and D white arrowheads show the normal boundary of expression and black arrowheads show the anteriorized limit of expression in the neural tube upon FGF2 treatment. In controls black arrowheads show the normal boundary.