Gene expression and morphology of GFP⁺progenitor cells. (A) RNA was extracted from the sorted cells in the indicated fractions, and RT-PCR was performed to detect GATA-1, GATA-2, EpoR, c-mpl, and IL-7R expression. The bone marrow Lin^-/c-Kit⁺ hematopoietic progenitor fraction was subdivided into 4 fractions (lanes 1-4). EEP and LEP fractions are represented in lanes 3 and 4, respectively. GFP^- (lane 5) and GFP⁺ (lane 6) cells in the Lin^-/c-Kit^- fractions also are shown. (B) The morphology of the sorted cells are shown by Wright-Giemsa staining. Proerythroblast-like cells were detected in the LEP fraction (GFP⁺/CD71⁺; i,ii). It is likely that erythroid progenitors are i, ii, iii, iv, v, and vi in the LEP and EEP (GFP⁺/CD71^-) fractions. All cells in the GFP^-/CD71⁺ fraction contained azurophil granules (xvi-xx).