Generation of T/NK-cell precursors and the induction of human T-cell development from human stem cells requires high levels of Notch signaling. (A) Flow cytometric analysis of CD34 and CD7 expression in human CD34⁺CD38⁻Lin⁻ CB precursors after 10 or 16 days of coculture on OP9-DL1 stromal cells in the presence of various concentrations of the γ-secretase inhibitor DAPT (GSI). Numbers in quadrants indicate the percentage of the corresponding population. Results shown are representative for 5 independent experiments. (B) Corresponding cellularity of CD34⁺CD7⁻, CD34⁺CD7⁺, CD34⁻CD7⁺, and CD34⁻CD7⁻ subsets for cultures depicted in panel A. Data are presented on a log scale and shows mean plus or minus SEM (n = 5). (C) Flow cytometric analysis of CD7 and CD1 expression at day 16 of the same cultures as in panel A. (D) Corresponding cellularity of CD7⁺CD1⁺ T cell–committed precursors as depicted in panel C. Data are presented on a log scale and show mean plus or minus SEM (n = 5). *Significant difference (P < .05).