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Fig. 5. Ectopic activation of the BMP pathway expands Hox expression to the organiser side. (A–H) Vegetal views (organiser is up) of noninjected (ni) and Alk-6-injected embryos stained for Hoxd-1 (A, B), Hoxc-6 (C, D), Hoxa-7 (E, F) and Hoxb-8 (G, H). Ectopic Alk-6 expression results in an expansion of the Hox expression on the organiser side. (I) A cross section (as indicated in the schematic drawing) of the marginal zone of an Alk-6-injected embryo (stage 11.5, organiser side indicated by O). Ectopic expression of Hoxd-1 on the organiser side is present in the mesoderm, but not in the overlying ectoderm (arrowheads). The dashed lines indicate Brachet’s cleft, which separates involuted mesoderm and the non-involuted tissue (i.e. neuroectoderm on the organiser side and preinvoluted mesoderm on the non-organiser side). |
