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Fig. 7. Organiser gene expression in FGFR-deficient embryos. (A-H) Four-cell embryos were treated with 80 μM SU5402 until early gastrula stage 10.5 and fixed for in situ hybridisation. This treatment yielded class V embryos. In A-C, embryos were cut in two halves along the dorsoventral midline prior to hybridisation in order to improve probe penetration. The organiser genes cerberus (cerb; A), dickkopf1 (dkk1, B), hex (C), otx2 (D), goosecoid (gsc; E) and chordin (chd; F) are normally expressed in class V embryos, whereas noggin (nog; G) is not. Conversely, the epidermis inducer bmp4 is ectopically expressed in the dorsal ectoderm of class V embryos (H). Thus, BMP signalling is probably upregulated in prospective neural tissue in absence of FGF activity. (A-C) Dorsal towards the right. (D-G) Vegetal view, dorsal towards the top. (H) Dorsal view, anterior towards the top, broken lines indicate the blastopore. |
