Fig. 1

Endoderm Progenitors Arise in an Fgf Ligand-Expressing Domain, but Their Specification Is Inhibited by Fgf Signaling

(A) Representative image of a 50% epiboly (5.3 hpf) embryo stained for sox32 by WISH.

(B) Sections of three 50% epiboly embryos stained for sox32 by WISH. Dashed line represents the border of the YSL and blastoderm, and arrows indicate sox32-positive endoderm progenitors. Scale bar, 25 μm.

(C) Sections of 50% epiboly embryos stained for fgf3 and fgf8a. Note that fgf3 is also expressed in the YSL. Scale bar, 25 μm.

(D) Images of 75% epiboly (8 hpf) zebrafish embryos treated with DMSO or PD-0325901 from sphere stage, stained for sox17 by WISH. Arrowhead indicates dorsal forerunner cells to aid comparison of stages.

(E) Quantification of sox17-positive cells in embryos as in (D) treated with DMSO (d), SU-5402 (SU), or PD-0325901 (PD). Means ± SD, Mann-Whitney U test; ^∗p < 0.05.

(F) Quantification of sox17-positive cells at 90% epiboly after treatment with DMSO (d) or PD-0325901 (PD) from sphere (s), 30% epiboly (30), or 50% epiboly (50), corresponding to 4, 4.7, and 5.3 hpf, respectively. Means ± SD, Mann-Whitney U test; ^∗p < 0.05.

(G) qPCR for indicated genes in dissociated embryonic cells treated with recombinant human NODAL and/or bFGF. Means ±SEM, n = 3, t test; ^∗p < 0.05.

(H) Double fluorescence in situ hybridization (FISH) for lft2 and sox32 in flat-mounted 50% epiboly embryos treated with DMSO or PD-0325901. White box indicates enlargement in right panel and dotted line marks the boundary between the YSL and margin.

(I) Graph of quantification of sox32-positive cells in (H). Means ± SD, Mann-Whitney U test; ^∗p < 0.05.

Scale bars, 100 μm unless otherwise stated. See also Figure S1.