Early erythroid differentiation of human CD34⁺ cells transduced with TRIP-TAL1 and TRIP-ΔbTAL1. (A) CD34⁺ cells transduced with TRIP-EGFP, TRIP-TAL1, and TRIP-ΔbTAL1 were cultured for 7 days in serum-free medium with SCF, IL-3, and IL-6. At day 6, Epo was added to allow terminal erythroid differentiation. Cells were labeled every day with MoAbs directed against CD34 and CD36 cell surface markers. Results are expressed as percent of CD34⁺ cells (mean ± standard deviation [SD], n ≥ 2). (B) Phenotypic analysis of human hematopoietic cells transduced with the TRIP vectors cultured during 3 days as in panel A. Quadrants were set according to isotype controls. Percent of cells for each quadrant is indicated. Boxed numbers indicate the MFI of the CD34 labeling in CD34⁺CD36^- (upper left) or CD34⁺CD36⁺ (upper right) populations. Results are representative of 4 different experiments. (C) High expression of CD34 surface marker on cells with enforced expression of ΔbTAL1, but not of TAL1, compared with control EGFP. Shown are results obtained with CD34⁺CD36^- (▪) and CD34⁺CD36⁺ (▧) cells. Results (mean ± SD; n = 4) are compared with those of EGFP⁺ control cells, referred to as 100%. Inserted in the figure are results of CD34 mRNA expression in both CD34⁺CD36^- and CD34+CD36+ populations obtained using quantitative RT-PCR analysis (representative of 2 experiments). Statistical analyses were performed using the Student t test (paired, 2-sided). ^*P < .05.