Hematopoietic progenitor-derived colony formation of GATA-2irGFP- and control irGFP-expressing bone marrow cells. Unsorted irGFP- and GATA-2irGFP–transduced cells (n = 3) and flow cytometric sorted, GFP⁺ (POS) (n = 3) and GFP⁻ (NEG) (n = 2) cells for each vector, as indicated, were cultured in duplicate in semisolid media and colonies enumerated as described in Materials and Methods. Data are expressed as the mean number (± standard error) of hematopoietic colonies per 10⁴ cells. The values within both the unsorted and sorted positive groups were statistically significantly different (P < .03 and P< .02, respectively) from each other.