Functionality of CXCR4 expressed on transduced CD34⁺ cells. (A) CXCR4-transduced CB CD34⁺ cells were stimulated with SDF-1 (300 ng/mL) for the indicated times and intracellular F-actin content was measured by FACS. Data indicate fold increase in F-actin content following stimulation with SDF-1 compared to unstimulated cells. Data represent mean ± SE of 3 independent experiments. (B) CXCR4-transduced CB and MPB CD34⁺ cells were tested in a transwell migration assay for their migration toward different SDF-1 concentrations as indicated. Data indicate percent migrating cells to SDF-1. Bars represent mean ± SE of 5 independent experiments. ^*P < .04 (CB), ^*P = .03 (MPB) compared to control GFP-transduced cells at 125 ng/mL SDF-1. ^*P < .05 (CB), ^*P < .05 (MPB) compared to control GFP-transduced cells at 10 ng/mL SDF-1.