Transduction of primary hematopoietic progenitors by HIV-based (LT) and MLV-based (RT) promoter traps. (A) FACS analysis of GFP expression in murine hematopoietic progenitors transduced with matched amounts of the indicated vector traps and analyzed 5 days after transduction. The frequency and MFI of GFP-positive cells are indicated. Representative results of 2 experiments performed. (B) FACS analysis of GFP expression in human cord blood CD34+ cells stimulated for 36 hours with a cytokine cocktail, transduced with matched vector amounts yielding low-copy (< 1) integration per cell, and analyzed after 1 week in liquid culture. The percentage of GFP-positive cells is indicated. Representative results of 2 experiments performed. (C) FACS analysis of GFP expression (histogram) of puromycin-selected cells from the populations shown in panel B. UC indicates unselected cells.