RUNX2 enrichment and epigenetic landscape during the differentiation of osteoblast cultures at the Mck locus. (A) The muscle creatine kinase (Mck) gene is transcriptionally controlled by three conserved regulatory regions: the upstream enhancer (−1256 to −1050), the proximal promoter (−358 to +7), and the small intronic enhancer (SIE, +904 to +998). In MC3T3-E1 cultures, the Mck locus displays hypersensitivity at the promoter region but not at the upstream or intronic enhancer regions. (B) Activating histone marks are absent within this region in induced BMSC cultures: (i) H3K4me1 (yellow tracks), (ii) H3K3me3 (blue tracks), (iii) H3K9ac (green tracks), and (iv) H3K27ac (red tracks) and (v) merge of all activating histone marks. The repressive H3K27me3 mark (black tracks) is dynamically enriched in differentiating cultures. All scaling of tracks shown here are equal between each culturing time point and locus position. A 30-way alignment of sequence conservation among placental mammals is shown above each gene locus.