Fig. 8. Shh protein is restricted to its site of synthesis in Disp mutants. Cross-sections of wild-type (A) and Disp^-/- (B) embryos at 9.5 dpc at the heart level. In the wild-type (A) sections, Shh immunoreactivity (brown) is strong in the notochord and floor plate and it extends out bi-directionally in a graded fashion (arrows and arrowheads). In sections of Disp^-/- embryos (B), Shh immunoreactivity is only detected in the notochord (arrows) and no extended staining is present. nt, neural tube; fp, floor plate; nc, notochord.