Fig. 5. Double inhibition of the FGF and BMP pathways causes formation of an excess of endoderm precursors all around the embryo. (A-H) sox17 expression at 80% epiboly in wild-type embryos (A,E) or embryos injected at the one-cell stage with noggin RNA at 25 ng/µl (B,F), DN-Ras RNA at 300 ng/µl (C,G), or co-injected with noggin and DN-Ras RNA (D,H). Although inhibition of the BMP (B,F) or FGF/MAPK (C,G) pathways alone have modest effects on endoderm formation, blocking both pathways dramatically increases the number of endoderm precursors. (A-D) Dorsal views; (E,H) ventral views.