EPO expression in CD34⁺ cells. (A) Bone marrow cells were first enriched for CD34⁺ cells by magnetic sorting.22 Cells were further separated by fluorescence-activated cell sorting by using phycoerythrin-labeled anti-34 antibody recognizing a different CD34 epitope and cocktail of anti-lin (CD2, CD14, CD15, CD16, CD19, and glycophorin) antibodies labeled with fluorescein isothiocyanate. CD34⁺lin⁻ (R1) and CD34⁺lin⁺ (R2). (B) Total RNA from separated cells (4 × 10⁴ of CD34⁺lin⁻ and 1 × 10⁴ of CD34⁺lin⁺) was prepared for RT-PCR (35 cycles) with EPO and G6PD primers (CD34⁺lin⁻ cDNA template was prepared from 4 times more cells than CD34⁺lin⁺ cDNA, which resulted in higher genomic DNA contamination detected by PCR). CD34⁺lin⁺ cells (lane R2) contain EPO mRNA, whereas CD34⁺lin⁻ do not (lane R1). Size marker 123 bp ladder (M), negative control (−), genomic DNA (g), EPO and G6PD cDNA (+).