Quantitative analyses of GATA-1 and GATA-2 mRNAs during erythroid differentiation. (A) Bone marrow cells were analyzed for CD71 and Ter119 expression. Cells in open boxes (i-iii) were sorted and analyzed for GATA-1 expression level in B. The percentage of cells in each box is shown. (B) The relative GATA-1 and GATA-2 mRNA levels at different stages of erythroid cell development were measured by quantitative RT-PCR and normalized to the level of GAPDH mRNA. Erythroid differentiation is indicated by the x-axis from left to right.