Mef2c expression pattern during myeloid differentiation. (A) Quantitative RT-PCR was performed on cells isolated by FACS analysis from BM from B6 mice to determine Mef2c expression levels. RNA levels were normalized by comparing Hprt levels. Mef2c levels relative to that found in cells isolated from heart are shown. Shown is the mean and standard deviation of 2 assays each performed in duplicate. The following surface markers were used to isolate the indicated populations: HSC (cKit⁺Sca1⁺Lin⁻), CMP (Lin⁻Kit⁻Sca1⁻CD34⁺CD16/32⁻), GMP (Lin⁻Kit⁻Sca1⁻CD34⁺CD16/32⁺), MEP (Lin⁻Kit⁻Sca1⁻CD34⁻CD16/32⁻), erythroid precursors (TER119⁺), myeloid precursors (CD11b⁺), granulocytes (CD11b⁺Gr1^hi), and macrophages (CD11b⁺F4/80⁺). Mature monocyte (CD11b⁺Gr1⁻) cells were isolated from blood. Cytospins were microscopically examined to verify more than 90% purity of the different cell types. For early progenitors, the differentiation status was confirmed by analysis of RNA transcripts for different transcription factors. (B) The level of Mef2c transcripts in committed myeloid progenitors (CD11b⁺) in BM was analyzed after GM-CSF or M-CSF stimulation by quantitative RT-PCR.