Figure 4

Proximal VE and ExE are sufficient to induce PGCs in distal epiblast. (A) Schematic of the experimental design. E6.75–E7.0 Stella:gfp embryos were isolated and either the VE was isolated whole (cup shaped), the proximal region containing the PGC precursor cluster surgically removed and the VE "filled" with the ExE and distal epiblast (-cluster); or the embryo was cut in three parts and the part containing the PGC precursor cluster discarded (-cluster -proximal VE). (B-G) Explants derived from E6.75–E7.0 whole (B, C), -cluster (D, E) and -cluster -proximal VE (F, G) immunostained to detect Stella(GFP) (B, D, F), followed by staining to detect alkaline phosphatase-activity (C, E, G). Arrows show same PGCs in the different panels. (H-J) Sagittal section showing double LacZ and alkaline phosphatase-activity staining in E6.75 wild type (H), ROSA26:LacZ (I) and -cluster (J) explants cultured for 3 days. In -cluster explants, the ExE and VE were from wild type embryos and the distal epiblast was from a ROSA26:LacZ embryos. Arrows show the PGC cluster in each explant; the VE is also indicated. Scale bar is 200 μm.