Hemato- endothelial potential in Etv2⁺/Flt-1⁺. Flk-1⁺/Etv2⁻ or Flk-1⁺/Etv2⁺ cells from Etv2-Venus^+/− embryos (E7.5 embryo; 500 cells/35-mm well, E8.5 embryo proper; 8000 cells/35-mm well) were cultured on OP9 for 10 days with growth factors (erythropoietin, IL-3, G-CSF, SCF, and VEGF). (Aa) HPCs were preferentially observed in E7.5 Flk-1⁺/Etv2⁺ population (bottom). Similar cells did not develop from Flk-1⁺/Etv2⁻ cells (top). CD45⁺ cells or Flk-1⁺ plexus-like structures were only observed from Flk-1⁺/Etv2⁺ culture. Scale bar indicates 100 μm. (b) Flow cytometric analysis of cells generated from Flk-1⁺/Etv2⁻ or Flk-1⁺/Etv2⁺ embryonic cells. Mac-1⁺CD45⁺granulocytes or Ter119⁺ erythroid cells developed from E7.5 Flk-1⁺/Etv2⁺ fraction. Almost no cells were seen in the same FSC/SSC area containing HPCs from Flk-1⁺/Etv2⁻ cells cultured in the same condition. (Ba) Flk-1⁺/Etv2⁻ or Flk-1⁺/Etv2⁺ cells from E8.5 intra-embryo parts also showed similar results. After 10 days of culture, CD45⁺HPCs or Flk-1⁺/ICAM2⁺ ECs were seen from Flk-1⁺/Etv2⁺ cells (bottom), whereas few or no similar cells developed from Flk-1⁺/Etv2⁻ (top). Scale bar indicates 100 μm. (b) ECs developed more efficiently from E8.5 embryo proper Flk-1⁺/Etv2⁺ cells than from Flk-1⁺/Etv2⁻ cells. CD45⁺c-Kit⁺cells were seen only from E8.5 embryo proper Flk-1⁺/Etv2⁺ population.