Irf8^−/− MDPs do not express Klf4 mRNA. (A) Flow cytometric analysis of Lin⁻ Sca-1⁻ CD117^int/+ CD115⁺ MDPs. Numbers in parentheses indicate percentages of MDPs relative to whole bone marrow cells. Similar results were obtained in three other independent experiments. (B) Lin⁻ Sca-1⁻ CD117^int/+ CD115⁺ MDPs were isolated from WT and Irf8^−/− mice by cell sorting. Klf4, Csf1r, and Kit mRNA expression levels were analyzed by qRT-PCR in triplicate using the ΔΔCT method and were normalized by comparison with levels of Gapdh (mean ± standard deviation). (**) P < .01, (***) P < .001 (Student t test).