PCA of expressed genes and pairwise comparisons of different stages of early human erythroid progenitors. (A) PCA plot of 3 biological replicates at 4 different stages of early erythroid differentiation. (B) Pairwise comparison of the gene expression at different stages of early erythroid progenitors. (Upper right) Pearson and Spearman coefficient values. (Lower left) Scatter density plot. PC, principle component; R_p, Pearson product-moment correlation coefficient; R_s, Spearman rank correlation coefficient.