VE-cad⁺CD41⁻ hemogenic endothelial cells produce T cells in both YS and P-Sp with similar frequency. (A) VE-cad⁺CD41⁻ or VE-cad⁻CD41⁺ cells were sorted from E9.5 WT YS and P-Sp and were plated on OP9-DL1 stromal cells in a limited dilution manner (75-300 cells/well). After 7-10 days, each well containing cobblestone-forming area and lymphocyte-like cells was analyzed by flow cytometry. (B) CD4⁺CD8⁺DP cells were obtained from VE-cad⁺CD41⁻ cell population, not from VE-cad⁻CD41⁺ cells at a frequency of 1 of 162 YS VE-cad⁺ cells (left panel) and 1 of 165 P-Sp VE-cad⁺ cells (right panel), respectively.