miR-155 promotes proliferation of the LKS and myeloid progenitor compartments and functions in a cell-intrinsic manner during FLT3-ITD–driven MPD. (A) Total BrdU⁺ staining of LKS and myeloid progenitor cells (Lin^–, c-Kit⁺, Sca1^–) in BM. Representative flow cytometric plots and percentages are shown. (B) Experimental strategy for producing WT:FLT3-ITD and WT:FLT3-ITD 155^−/− BM chimeric mice. (C-D) Spleen analysis of WT:FLT3-ITD and WT:FLT3-ITD 155^−/− BM chimeric mice at 3 months posttransplant. Total numbers of various cell populations determined by flow cytometry. (E) Analysis of BM from WT:FLT3-ITD and WT:FLT3-ITD 155^−/− BM chimeric mice at 3 months posttransplant. Total numbers of various cell populations determined by flow cytometry. Data are representative of at least 2 independent experiments. Each point represents a sample from 1 mouse. *P ≤ .05; **P ≤ .01; ***P ≤ .001.