Analysis of Epo target genes in basophilic and polychromatic erythroblasts (R4). (A) mRNA expression of Bcl-x_L, (B) Serpina3G, (C) Fasl, and (D) Erfe relative to Gapdh in R4 erythroblasts. mRNA expression ratio was normalized to the control mean value of 1. Mean values of 3 samples for genotype (controls, Tfr2^BMKO) are graphed. Error bars indicate standard error. Asterisks refer to a statistically significant difference. *P < .05; ***P < .005.