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FIG. 1. Anatomy of the early endoderm in Xenopus (A–C), zebrafish (D–F), and mouse (G, H) embryos, shown in conjuction with
schematic fate maps which depict the origin of the majority of the endoderm (A) in the vegetal hemisphere of Xenopus embryos and (D)
in the four marginal blastomere tiers in Danio (Warga and Nusslein-Volhard, 1999). (B) Photomicrograph of the Xenopus blastula (Hausen
and Riebesell, 1991), with pigmented ectodermal precursors in the blastocoel roof (top) and endoderm precursors in the vegetal pole
(bottom). Data are also shown for mRNA in situ hybridization for endodermal markers, Xsox17 (C) in Xenopus (Zorn et al., 1999b) and
Bonnie and clyde (Bon; side view in E, top view in F) in D. rerio (Kikuchi et al., 2000). (G,H) Mouse embryo at the end of gastrulation, when
the endoderm (arrows in G) is transiently an external tissue layer, and with the endoderm stripped away (H) to reveal its relationship to the
rest of the epiblast (Wells and Melton, 2000). Individual panels reprinted with permission from (B) Springer-Verlag Publishers, (D, G, and
H) The Company of Biologists Ltd., and (E and F) Cold Spring Harbor Laboratory Press. |
