Fig. 5. Bmp4 antagonizes Chordin activity in the embryo. Four-cell stage embryos were injected, into each blastomere, with Bmp4 MOs (12 ng) or Chordin MOs (7 ng), or co-injected with a mixture of the two (n=15 per experimental set). (A-C) Sizzled is expressed in the ventral center at stage 12 (A) and on the ventral side (B,C) at tailbud stage. (D-F) Depletion of Bmp4 results in the lack of Sizzled expression at late gastrula stage (D) and in significant reductions at tadpole stage (E,F). Expression of Six3, an eye marker, is expanded. (G-I) Chordin depletion gives rise to a phenotype opposite to that seen in Bmp4 MO embryos, with increased Sizzled expression and reduced Six3. (J-L) Bmp4 is epistatic to Chordin in co-injection experiments.