Relative expression of Fli-1 and GABPα in murine fetal liver–derived megakaryocytes. (A) Steady-state RNA levels measured by quantitative real-time RT-PCR of Fli-1 and GABPα both relative to GAPDH in CD41⁺/GPIbα^–immature megakaryocytes (□) and CD41⁺/GPIbα⁺ mature megakaryocytes (▪). (B) Relative protein levels of Fli-1 and GABPα in mature megakaryocytes. On the left, Western blots of known amounts of nuclear extracts were compared to known concentration of the appropriate recombinant proteins to determine the relative ratio of GABPα to Fli-1 proteins in nuclear extracts from fetal liver–derived mature megakaryocytes. Quantitative analysis by QuantImage analysis is shown on the right. For all studies in panels A and B, the mean ± one SD of 3 experiments, each in triplicate, is shown.