Transposons for HSC gene transfer. Plasmid encoding the hyperactive SB100X transposase were cotransfected by nucleofection with transposon-containing constructs in CD34⁺ stem or progenitor cells enriched from cord blood. Transfected cells were subsequently injected into immunodeficient NOD-γ_c^−/− (nonobese diabetic–severe combined immunodeficient) mice. The transplanted cells contributed to efficient hematopoietic reconstitution and robust multilineage gene marking.²¹