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Fig. 4. The constitutively active BMP receptor, ALK-6, ventralises and posteriorises embryos. (A, B) Embryos were injected with the constitutively active human BMP receptor (Alk-6) at stage 1. Phenotypic analysis shows the expected effects of head reduction and shortened trunks in Alk-6-injected embryos (B) compared to noninjected (ni) controls (A). (C–N) Marker analysis of Alk-6-injected embryos. In situ hybridisations were performed on noninjected embryos (C, F, I, L) and embryos injected with 600 pg Alk-6 (D, G, J, M) or 1.2 ng Alk-6 (E, H, K, N) using probes for the anterior gene, otx-2 (C, D, E), the organiser gene, chordin (F, G, H), the posterior gene, Hoxb-9 (I, J, K) and the ventral gene, Xvent-2 (L– N). Expression of otx-2 and chordin was reduced, whereas expression of Hoxb-9 and Xvent-2 was expanded. Embryos are shown from the anterior (C– E), from the dorsal site with anterior to the right (F–K) or from the lateral side with anterior to the right (L – N). |
