BCR-ABL and v-SRC expression reconstitute the erythroid phenotype in EpoR−/− fetal liver cells. (A) Epo-independent BCR-ABL-generated bursts (BFU-E) cultured either in 15% serum alone (a) or in serum supplemented with IL-3, IL-6, and SF (b); Epo-dependent EpoR-generated colony cultured in Epo and IL3, IL-6, and SF is shown as control (c) (×100). (B) Cytospin preparations and May-Grünwald Giemsa staining of individual BCR-ABL-generated BFU-E-derived colonies generated in the absence (a) or presence of IL-3, IL-6, and SF (b) show erythroid cells at different stages of differentiation (×1,000). (C) Genomic PCR of BCR-ABL on individual BFU-E from EpoR (lanes 1 and 2)- or BCR-ABL (lanes 3–6)-derived colonies plated in the presence of 15% serum only (lanes 5 and 6), serum supplemented with IL-3, IL-6, and SF (lanes 3 and 4), or Epo and IL-3, IL-6, and SF (lanes 1 and 2). The PCR reaction was run on a 1.5% agarose gel and shows a band of 404 bp corresponding to the amplified breakpoint region of BCR-ABL. A positive control using a BCR-ABL containing plasmid MSCV-P210 is shown (lane 7). (D) GFP-positive v-SRC reconstituted BFU-E from EpoR−/− fetal liver cells (×100). Results are from one representative experiment.