Enforced expression of wild-type Flt3-RTK and W51 Flt3-ITD in human CB-CD34⁺ cells. (A) Map of MIGR1, wtFlt3, and W51 Flt3-ITD retroviruses used in this study. (B) Transduction efficiencies were determined by EGFP expression using flow cytometry analysis. Purified CB-CD34⁺ cells were prestimulated for 48 hours in QBSF-60 supplemented with KL, FL, and Tpo (100 ng/mL) and then subjected to 3 transduction rounds as described in “Materials and methods.” (C) Immunoblot of whole-cell protein extracts from transduced and sorted CB-CD34⁺ cells with anti-Flt3 antibody (Ab). LTR indicates long terminal repeat.