Fig. 4. BMP signalling restricts ventral endoderm formation. sox17 (in blue) and foxi1 (green) expression at 70% epiboly in wild type (A-C) and in embryos injected with DN-Ras RNA (300 ng/µl) at the one-cell stage (D-I). Arrows in C,F,I indicate the boundary between the epidermis and endoderm. (J-L) sox17 expression at 75% epiboly in wild-type embryo (J); in an embryo injected into one ventral blastomere at the 16-cell stage with a mixture of RNAs encoding Bmp2b, Bmp4 and Bmp7 (5 ng/µl, 5 ng/µl and 40 ng/µl) (K); and in an embryo injected at the one- or two-cell stage with a mixture of Bmp2b, Bmp4 and Bmp7 RNAs (2.5 ng/µl, 2.5 ng/µl and 20 ng/µl) (L). (A-F) Lateral views; (G-I,L) dorsal views; (J,K) ventral views.