Sox17 promotes the expansion of CD34⁺CD43⁺CD45^−/low cells. (A) Growth curve of ECs from day 6 EBs that were transduced with a Sox17-ERT or a control retrovirus. ECs (2 × 10⁴) were transduced with the indicated retrovirus on OP9 cells and cultured in the presence of 20 ng/mL of SCF and TPO and 200nM 4-OHT. The absolute numbers of cells were determined and plotted. Representative data from repeated experiments are shown. (B) Appearance of a representative colony generated by Sox17-overexpressing cells in panel A observed under an inverted microscope. Images were collected using BIOREVO BZ-9000 (KEYENCE) with CFI Plan Fluor ELWD DM 20×C (Nikon). (C) Typical cell morphology of Sox17-overexpressing cells in panel A. Sorted cells were cytospun onto glass slides and observed after Wright-Giemsa staining. ECs, pre-HPCs, and HPCs from day 8 EBs served as controls. Images were collected using BIOREVO BZ-9000 (KEYENCE) with CFI Plan ApoVC 100×H (Nikon). (D) Flow cytometric analysis of expanded cells on overexpression of Sox17. ECs from day 6 EBs and pre-HPCs and HPCs from day 8 EBs were transduced with a Sox17-ERT or a control retrovirus cultured on OP9 in the presence of 20 ng/mL of SCF and TPO and 200nM 4-OHT for 10-15 days and then analyzed for their immunophenotypes.