Id2 reduction increases Gata1, EpoR, Hbb-b1, Eklf, and CD71 expression levels in Gfi-1^−/− mice. RNA was purified from (A) whole BMCs and (B) purified Lin⁻ BM progenitors from the indicated mice to determine the expression of genes that regulate erythroid development and cell-cycle genes by real-time qRT-PCR. TaqMan primers were used to determine the expression of each of the indicated genes. Expression levels are reported relative Gapdh expression in mouse BMCs. *P < .05. (C) Western blot analysis of Gata1, Gata2, EpoR, Eklf, and Cyclin E protein levels in Gfi-1^+/+, Gfi-1^−/−, and Gfi-1^−/−;Id2^+/− BMCs. (D) Summary of potential mechanism of how Id2 reduction in the Gfi-1^−/− background restores impaired erythroid development.