Representative FACS analyses of NGFR transgene expression in progeny of MINGFR-transduced, CD34⁺Lin⁻cells recovered from SCID-hu bone mice. Harvested cells from implanted human bone fragments were stained with the FITC-conjugated MA2.1 antibody recognizing the donor cell's HLA, and the PE-conjugated anti-NGFR antibody recognizing the transgene expression on cell surface. Viable cells were then collected and analyzed by FACS. Bone fragments in the absence of injected cells (A) and the presence of mock-transduced cells (B) were included as controls to distinguish donor cells (MA2.1⁺) from endogenous human cells and/or contaminating murine cells (MA2.1⁻). Cells recovered from two different bone implants injected with sorted CD34⁺Lin⁻NGFR⁺ cells transduced with MINGFR are shown in (C) and (D). Approximately 35.5% (C) and 44.7% (D) of donor-derived cells were expressing the NGFR reporter after 9 weeks in vivo. See Materials and Methods for experimental details and Table 2 for a summary.