Fig. 4. Disp null mutants phenocopy Smo mutants. (A-D) External morphology of wild-type (A), Disp^-/- (B), Smo^-/- (C) and Shh^-/- (D) embryos at 9.5 dpc. All views are lateral except B,C, which represent lateral ventral views. Note that embryos in B,C have initiated but failed to complete turning. By contrast, Shh^-/- embryo (D) collected at a similar stage has completed embryonic turning. (E-H) Cross-sections of 9.5 dpc wild-type (E), Disp^-/- (F), Smo^-/- (G) and Shh^-/- (H) embryos at the level of the heart tube stained with Hematoxylin and Eosin. Arrows in F,G indicate the linear heart tube in Disp (F) and Smo (G) mutants, when compared with the multichambered heart in the wild-type (E) and Shh^-/- (H) embryos. All major cell types are present in a grossly normal organization in Disp mutants (F).