Fig. 1. Smad6 does not induce neural markers in the chick. (A-G) Experiments to test the activity of Smad6. Smad6-IRES-GFP was electroporated into one half of the chick neural tube (A,B). Staining against phospho-Smad1 (A) reveals that activation of Smad1 has been inhibited in the electroporated cells (green in B), while in control GFP electroporated embryos (C,D) phospho-Smad1 is not altered (C). cSmad6 injection into the marginal zone in Xenopus (E) induces a secondary axis (F), while GFP-injected controls appear normal (G). (H-N) Smad6 does not induce neural markers. Electroporation of Smad6 into competent area opaca epiblast at stage 3+ (H) does not induce Brachyury (I,L; light blue), Sox2 (J) or Sox3 (M) (purple). In this and subsequent figures, electroporated cells were visualized by staining with anti-GFP antibody (K, N; brown). (O-Q) Positive controls. cSmad6 or GFP was injected at the two-cell stage and animal caps isolated at early gastrula (O). Smad6 (P) can neuralize animal caps, while GFP cannot (Q), as assessed by Sox3 expression.