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Fig. 1. Organizer genes are expressed in vegetal pole explants. (A) Double in situ hybridization for chordin (BCIP, blue) and cerberus (BM Purple) in a sectioned stage 10 embryo. The two genes show overlap in endodermal-fated vegetal cells. (B–H) Stage 8.5 embryos were dissected and vegetal pole explants were cultured for 2 h before in situ hybridization for chordin (B, n = 12), cerberus (C, n = 9), gsc (D, n = 12), frzb (E, n = 15), noggin (F, n = 12), and Xbra (H, n = 14). All views are animal, dorsal side is to the right. (G1, 2) Vegetal explants were sectioned sagittally (n = 18), and each half was hybridized in situ for chordin (G1) or Xsox17β (G2). Internal views of the sections, dorsal side up, animal sides facing each other. (G1 + 2) The two halves juxtaposed and viewed from the animal side. (I–K) Timing and FGF-dependency of chordin expression in vegetal explants. (I) Stage 9 explant, immediately after dissection (n = 12). (J, K) Explants after 2 h incubation, in the absence (J, n = 15) or presence (K, n = 11) of the MEK inhibitor U0126, which blocks the FGF pathway. |
