Gene expression analysis of CD34⁺CD38^−/lo HSCs cultured on OP9-DL1 cells. (A) Temporal kinetics of gene expression by quantitative real-time QRT-PCR analysis from human CD34⁺CD38^−/lo HSCs cultured on either OP9-control or OP9-DL1 cells for 6, 10, 14, and 18 days, as indicated. (B) Flow cytometric analysis for the cell surface expression of CD7 and CD1a from a day-50 HSC/OP9-DL1 coculture, with CD34 expression shown for cells gated as CD7⁺ CD1a⁻. (C) Gene expression analysis by QRT-PCR from the coculture-derived subsets as indicated in panel B: CD34⁺CD7⁺⁺CD1a⁻, CD34⁻CD7⁺⁺CD1a⁻, CD34⁻CD7⁺⁺CD1a⁺, CD34⁻CD7⁺CD1a⁺⁺; see figure key. CD3⁺ T cells and CD33⁺ myeloid cells were purified from the Lin⁺ fraction of UCB samples and served as controls. Transcript levels for the indicated genes were normalized to human β-actin, and these data are representative of 3 independent experiments, with the STD error bars shown corresponding to values obtained from triplicate wells within an individual experiment.