Cytokine-induced activation of Ras effectors in Mx1-Cre, Nras^G12D myeloid cells. (A) The Mac1⁻Gr1^lowcKit⁺ gate was used to enrich for immature myeloid lineage cells. (B) Levels of phosphorylated ERK and S6 (pERK and pS6) were assayed in 3-month-old F1 WT, Mx1-Cre, Nras^G12D, and Mx1-Cre, Kras^G12D cells before and after stimulation with a saturating dose of IL-3 (50 ng/mL) or SCF (100 ng/mL) for 10 and 30 minutes. The vertical line in each panel indicates the basal level of protein phosphorylation in unstimulated WT cells. (C) Levels of pERK and pS6 were quantitated by median fluorescence signal from pFACS in panel B and compared with WT basal level, which was assigned a value of 1.