IFN-γ induces expression of PU.1 in erythroblasts. (A) Microarray heat map of unsupervised cluster analysis for genes expressed in CD71⁺ erythroblasts from BM of WT, CD70TG, IFN-γ^−/−, and CD70TG*IFN-γ^−/− mice. Red represents high expression; and green, low expression. Three mice were analyzed per group. (B) Venn diagram displaying potential PU.1 and GATA-1 targets among the IFN-γ–regulated genes in CD70TG mice. (C) Western blot analysis of PU.1 and GATA-1 expression on purified CD71⁺ BM cells from 2 mice per experimental group. (D) Flow cytometric analysis of PU.1 expression in MEPs of WT, CD70TG, IFN-γ^−/−, and CD70TG*IFN-γ^−/− mice. Horizontal line represents the value of the isotype control. Data are mean ± SD for 3 mice per group. Results are representative from 2 independently performed experiments. *Significant difference (P < .05) between CD70TG mice and all other groups (1-way ANOVA with Bonferroni correction). (E) Quantitative PCR analysis of PU.1 mRNA on WT CD71⁺ erythroblasts cultured overnight with or without IFN-γ. (F) Quantitative PCR analysis of PU.1 and GATA-1 mRNA on WT MEPs cultured overnight with or without IFN-γ. (E-F) Data are presented as the fold induction of gene expression with IFN-γ compared with the medium control for 7 (E), or 9 and 6 (F) mice per group, pooled from at least 2 independently performed experiments. *P < .01 (E) or P < .05 (F) using paired Student t test. n.s. indicates not significant.