Figure 1

VE and ExE are both important for the formation of PGC precursors. (A) Schematic of the experimental design: E5.75 embryos were isolated and either cultured whole or after the surgical removal the VE (-VE) or the ExE (-ExE). (B) E5.75 Blimp1:gfp embryo showing GFP signal in the VE (white arrows). PGC precursors emerge approximately 12 hours later in the proximal epiblast region adjacent to the asterisks. (C, D) Explants derived from E5.75 -VE Blimp1:gfp embryos cultured for 1 day, D1 (C) and 3 days, D3 (D). (E-H) Explants derived from E5.75 whole and -ExE Blimp1:gfp embryos cultured for 1 day, D1 (E, G) and 3 days, D3 (F, H). E, G, white arrows point to Blimp1(GFP)-positive VE; F, white asterisk marks Blimp1(GFP)-positive PGC precursors in the proximal-posterior part of explant; H, red arrow points to Blimp1(GFP)-negative VE, but Blimp1(GFP)-positive epiblast. Cartoons adjacent to the explants elucidate the morphology of the explant. Abbreviations: Emb, tissue derived from epiblast; ExE, extraembryonic ectoderm; thick black line, endoderm. (I, J) Explants derived from E5.75 whole and -ExE ΔPEOct4:gfp (I) and Stella:gfp (J) embryos cultured for 3 days, D3. White asterisk marks the proximal-posterior part of explant; -ExE explants were inserted in the lower left corner of I and J. K, After 4 days of culture, the cluster of Blimp1(GFP)-positive cells present in explants from whole embryos turns positive for alkaline phosphatase-activity (AP). Scale bar in B-J is 100 μm and K is 25 μm.