Foxd3 regulation of axis formation is dependent on the Nodal signaling pathway. Wild-type (WT) or MZoep mutant embryos were injected at the one-cell stage with zebrafish foxd3 (25pg) or Xenopus ActivinβB (25pg) mRNA and analyzed at the 24hpf stage (A,B,D,E,G,H) or early somitogenesis stage (11hpf) (C,F,I). Uninjected (A,B), foxd3-injected (D,E), and Activin-injected (G,H) wild-type (A,D,G) and MZoep (B,E,H) embryos at 24hpf are shown (lateral views of live embryos with anterior left). In situ hybridization showing notochord expression of no tail (ntl) (C,F,I) in uninjected (C), FoxD3-injected (F), and Activin-injected (I) MZoep embryos at early somitogenesis stage (11hpf) (dorsal views with anterior up).