CFU-S assays were performed as described in Materials and Methods. The number of total and PCR-positive CFU-S colonies found after injection of either Bodipy-selected (25% least fluorescent) or nonselected transduced cells are shown. The cells selected for lower Bodipy fluorescence produced a significantly higher number of PCR-positive colonies than cells that were nonselected (χ2 = 10.607; P = .001).