Fig. 3. Essential and conserved role of vertebrate smo in Hh signaling. (A,B) Lateral view of wild-type and mutant embryos at 24 hpf (A) and 12 hpf (B) demonstrating the absence of ptc1 expression in the mutants. (C-E) ptc-1 expression in response to manipulation of Hh signaling components in wild-type and mutant embryos indicates a conserved role of smo in the pathway in zebrafish. Embryos were injected at one- to two-cell stages and ptc1 expression is determined at 12 hpf. (C) shh mRNA injection. (D) twhh mRNA injection. (E) PKI mRNA injection. Arrows indicate ectopic expression.