Expression of transcription factors C/EBPε, PU.1, GATA-1, and differentiation markers (CD34 and MPO) during myeloid differentiation of CD34⁺ cells. Total RNA was extracted from CD34⁺CD38⁺ and CD34⁺/CD33⁺ cells before and after culture with stem cell factor and PIXY321. Cells were harvested at the days indicated. (A) The mRNA expression was studied by RT-PCR and expression of β-actin mRNA was used as an internal control. (B) Differentiation of CD34⁺/CD33⁺ cells as determined by morphology. For each slide, 200 cells were counted, and the number of cells at different stages of differentiation were plotted on a graph.