Fig. 1

Initial Position of Tg(ins:GFP)-Expressing Cells

12- (A–C, and F), 15- (D–E, and I), and 18- (G–H) somite stage (corresponding to 15, 16.5, and 18 hpf, respectively) Tg(ins:GFP) embryos showing GFP (green; [A–B and D–I]), TOPRO (white; [B, E, and H]), β-catenin (red; [B, E, and H]) and Tg(sox17:DsRed)^s903 (red; [F and I]) staining. Dorsal views of fixed embryos (A, D, and G), and confocal images of transverse sections (B, E, and H) and of ventral views (F and I). (A) One Tg(ins:GFP)-expressing cell (arrow) is present in the endoderm of this 12-somite stage embryo. Cells in the anterior neural tube (arrowhead) also express the ins:GFP transgene. (B) The Tg(ins:GFP)-expressing cell (arrow) is located in the medio-lateral axis between the notochord and left somite. (C) Schematic diagram of a transverse section showing Tg(ins:GFP)-expressing cells (green) within the endodermal sheet (yellow), as well as the notochord (red), somites (blue), neural tube (gray), and LPM (purple) at the 12-somite stage. Note that the endoderm consists of a monolayer of cells located at the ventral-most side of the embryo. (D, E, G, and H) At the 15- (D and E) and 18- (G and H) somite stage, Tg(ins:GFP)-expressing cells (arrows) lie bilateral to the notochord. Cells in the anterior neural tube (arrowhead) also express the ins:GFP transgene. (E and H) Mesenchymal cells (arrowheads) have migrated toward the midline. (F and I) At the 12- (F) and 15- (I) somite stage, gaps (asterisks) can be observed in the midline of the fusing endodermal sheet (red). Most Tg(ins:GFP)-expressing cells (green; arrows) are located bilateral to the notochord.