Fig. 1. Endoderm commitment occurs at the onset of gastrulation. (A) Diagram of the experimental procedure. DMNB-caged fluorescein was injected at the 1-cell stage. At the late blastula stage, fluorescein was uncaged in a few cells at the animal pole or at the very margin of the donor embryo. At 50% epiboly-germ ring, labelled cells were transplanted to the animal pole of a late blastula (dome) host. (B,C) Anterior to the left, dorsal to the top. (B) Cells transplanted from the animal pole of the donor populated the eye and the forebrain and differentiated accordingly. (C) In contrast, marginalmost cells taken just before or at the onset of gastrulation colonised the endoderm-derived territories and expressed the endodermal marker fkd7 (section in D). Some of these cells also populated the hatching gland (not shown). The white dots indicate the limit of the YSL. e, eye; no, notochord; nt, neural tube; AP, Animal Pole; M, Margin.
