Fig. 8. FoxD3 acts upstream of Nodal in axis formation and mesoderm induction. (A) Control. At the four-cell stage, both dorsal blastomeres were injected with FoxD3MO (25 ng) alone (C), or in combination with 10 pg of Xnr1 RNA (D). At the dose used, injection of Xnr1 alone (B) did not perturb axis formation in most embryos. (E) Quantification of a representative experiment. (F) To assess the dependence of Xnr1 and VegT activity on FoxD3, the animal pole was injected at the one-cell stage embryo with VegT (500 pg) or Xnr1 (100 pg) alone, or in combination with FoxD3MO or mismatch MO (50 ng). Animal explants were analyzed by RT-PCR at the gastrula stage (stage 11) for the expression of Brachyury (Xbra), MyoD, Goosecoid (Gsc), Xnr1 and Xnr2. As controls, the oligonucleotides were injected alone or in combination with FoxD3 RNA (300 pg). PCR controls are as described in Fig. 2.