RNA expression profiles during in vitro erythroid differentiation are similar to ex vivo isolated erythroid precursors. RNA was isolated at subsequent days of differentiation to identify changes in the transcriptome (4 independent donors). (A) Bars represent the number of transcripts that are up- (red) or downregulated (blue) each day in reference to the start of the culture (false discovery rate <0.01 and log fold change >2, or <−2). Lines reflect cumulative number of unique genes differentially expressed over the time course. (B) Heatmap of z-transformed expression values (log2-CPM) for all genes encoding for blood group antigens and or blood group bearing moieties. (C) The transcriptome of MEP (black squares) and CD71^highCD235^high erythroblasts (black circles) isolated from bone marrow was compared with the transcriptome of differentiating cRBC using principle component analysis (PC1 vs PC3). (D) A Pearson correlation matrix of all samples used in panels A-C. Mean transcript levels (transcripts per million mapped reads) were compared between MEP and cRBC d0 (E) and between freshly isolated erythroblasts and cRBC d3 (F).