Ectopic expression of Mef2c inhibits granulocytic differentiation in both Irf8^+/+ and Irf8^−/− BM cells. BM cells were enriched for Lin^neg progenitors and infected with indicated vectors and sorted for GFP infection before plating into methylcellulose cultures with the designated cytokines. (A) Flow cytometric analysis of cells isolated from methylcellulose cultures after 1 week show the loss of Gr1⁺ cells in cultures infected with Mef2c. The percentage of cells within each immunotyped population is indicated. Typical results of 4 independent experiments. (B) Colony numbers and colony types from infected B6 BM cultures were scored after 1 week, showing a decrease in colonies containing mature granulocytes, in agreement with FACS analysis. Error bars denote standard deviation from the mean. (C) Cytospins of cells isolated from methylcellulose cultures from Mef2c- or GFP-infected Irf8^−/− BM cells demonstrate the absence of granulocytic forms, consistent with the results from the FACS analysis shown in the right panel of panel A.