Representative FACS analysis of competitively repopulated NOD/SCID mice. Three-channel FACS analysis of mouse BM 10 weeks after transplantation of human CD34⁺ cells transduced with either LV-GFP or LV-YFP. (A) Frequency of transgene expression in the human cell (hCD45⁺) graft. FACS plots from a competitively repopulated mouse, showing both GFP- and YFP-positive cells (top panels), and 2 reference mice, showing either YFP- or GFP-positive cells (middle and bottom panels), as indicated. Percentages of transgene-positive cells detected in each channel (FL-2: YFP; FL-1: GFP + YFP, FL-3: human CD45 [hCD45]) are given in the respective quadrant. (B-C) Multilineage engraftment by transduced SRCs. Percentages shown represent the fraction of transgene-expressing cells among the indicated lineage marker-positive cells (scored in the FL-3 channel). Because both GFP and YFP signals emit in the FL-1 channel, we calculated the frequency of GFP-expressing cells by subtracting the fraction of YFP-expressing cells, scored in FL-2, from the percentage of cells scored positive in FL-1. Mouse numbers are as in Table 1.