Vonica A , Gumbiner BM .

5R01 GM066977 NIGMS NIH HHS , HD40724 NICHD NIH HHS , P30-CA-08784 NCI NIH HHS , R37 GM037432-22 NIGMS NIH HHS , R37 GM374432 NIGMS NIH HHS , R37 GM037432 NIGMS NIH HHS , R01 GM066977 NIGMS NIH HHS , F32 HD040724 NICHD NIH HHS

	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.
	Fig. 5. Ectopic activation of the Wnt pathway in tier B and C cells induces expression of organizer genes only in injected cells. Double in situ hybridization of stage 9 embryos for the indicated organizer genes (purple) and coinjected LacZ (red). β-catenin (500 pg RNA) and LacZ (1 ng RNA) were injected at the 32 cell stage in the indicated tiers, on the ventral side of the embryo. Panels A, F, and K are dorsal views showing the wild-type expression pattern for Sia, gsc, and chordin, respectively. Activation of the genes in ventral cells is restricted to the injection site. chordin (21 embryos for tier B, 30 embryos for tier C) and Sia (24 embryos for tier B and 19 embryos for tier C) are activated in both tiers B and C (M, O, and C, E, respectively), but gsc (28 embryos for tier B and 22 for tier C) only in tier C (H, J).
	Supplementary Fig. S1.
	Supplementary Fig. S2.
	Supplementary Fig. S3.
	Supplementary Fig. S4.

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