Marking efficieny of CFU in nonexpanded and expanded fractions. In vitro transduction efficiency of CFU was assessed at the end of transduction for both fractions and the end of expansion for the expanded fraction. The efficiency was calculated by from the percentage of individual plucked CFU positive for neo sequences by PCR. For each animal, the percentage of CFU positive for the neogene is shown at the end of transduction for the nonexpanded fraction (End Transduction-NE), at the end of transduction for the fraction subsequently expanded (End Transduction-Exp), as well as colonies plated at the end of the expansion period for the expanded fraction (End Expansion).