Fig. 2. Depletion of XTcf3 causes a dorso-anteriorized phenotype. (A) Vegetal views of wild-type uninjected gastrula (top left; brown) and embryos injected with increasing doses of XTcf3 oligos (T1); 2.5 ng (top right; blue), 3.0 ng (bottom left; mauve) or 3.5 ng (bottom right; red). (B) Phenotypes of tailbud stage embryos (top) and isolated marginal zones (bottom) from uninjected controls (Un) or embryos injected with the indicated doses of XTcf3 oligos (T1; in ng). The embryos are from the same experiment as in A and the color code is the same. Excessive elongation is evident in isolated XTcf3^– marginal zone explants. (C) Phenotype of XTcf3^– embryos (TCF^–, 4 ng oligo T1) at the early tadpole stage (Un, uninjected). (D-F) Injection of XTcf3 RNA can rescue the XTcf3^– phenotype. These experiments used oligo T1 (3 ng, D,E) or T2 (5 ng, F). 100 pg of XTcf3 RNA was injected in rescued embryos. (D)Vegetal views of uninjected (Un, brown) and XTcf3^– gastrulae (TCF^–, mauve) compared to embryos from the same experiment injected with XTcf3 RNA (right row, arrowheads). Note reduced blastopore protrusion and delayed gastrulation in the rescued XTcf3^– embryos (bottom right two embryos). (E,F) Phenotypes of XTcf3^– (TCF^–) and rescued embryos (TCF^– +RNA) at the tailbud stage. Prominent notochords (arrowhead in E) and swollen anterior endoderm (arrowhead in F) in XTcf3^– embryos are absent in rescued embryos. Heads are reduced in rescued embryos (arrows) owing to the ventralizing effect of overexpressed XTcf3.