Fig. 7. Sox17ß requires ß-catenin to robustly activate target gene transcription in animal caps. (A) Embryos were injected at the two-cell stage with the indicated combinations of: Sox17ß mRNA (200 pg), RNA encoding a N-terminal deleted form of stabilized ß-catenin (N-ß-catenin, 100 pg) (Yost et al., 1996), or an antisense ß-catenin morpholino oligos (ßcat-MO; 20 ng). At blastula stage, animal cap tissue was explanted and cultured for 3-4 hours until gastrula stage, when it was assayed by real-time RT-PCR for the expression of Sox17 target genes. The histograms show the relative expression levels normalized to the loading control, ODC. Plakoglobin (Plako) is control gene that is neither a Sox17 nor ß-catenin target. (B) A proportion of each sample from the same experiment was assayed by immunoblotting with anti-ß-catenin, anti-Sox17ß or anti-tubulin antibodies. Injected N-ß-catenin protein has a higher molecular weight than endogenous ß-catenin because of the presence of an epitope tag. Tubulin is a loading control.