671 Cross-talk between covalent DNA modifications and chromatin architecture: DNA dioxygenase Tet2 mediates the effects of chromatin architectural protein CTCF on epidermal barrier maintenance, inflammation and tumorigenesis

Epigenetic regulatory machinery drives cell differentiation process via controlling covalent DNA/histone modifications and spatial chromatin interactions involving gene promoters and enhancers. Alterations in epigenetic regulatory mechanisms contribute to the development of many pathological conditions, including inflammation and cancer. Chromatin architectural protein CTCF controls enhancer/promoter interactions and terminal keratinocyte (KC) differentiation: ChIP-seq analyses revealed predominance of the CTCF binding to the distal gene regulatory elements versus gene promoters in KCs, while tamoxifen-treated K14-CreER/Ctcf fl/fl mice show alterations of the epidermal barrier structure and inflammation. Microarray analyses revealed that, together with altered expression of the genes involved in the control of KC differentiation, immune response and tumorigenesis, DNA 5-methylcytosine oxidizing Tet2 and Tet3 enzymes were markedly upregulated in the epidermis of K14-CreER/Ctcf fl/fl mice compared to controls. Furthermore, genetic Tet2 ablation in the compound K14-CreER/Ctcf fl/fl/Tet2 fl/fl mice was capable of rescuing alterations of epidermal barrier structure and inflammation caused by Ctcf loss in KCs. Also, K14-CreER/Ctcf fl/fl/Tet2 fl/fl mice showed significantly reduced capacity to develop epidermal tumors in chemical skin carcinogenesis model compared to K14-CreER/Ctcf fl/fl or control mice. Thus, these data suggest that Tet2-mediated DNA 5-methylcytosine oxidation plays pivotal roles in mediating the effects of CTCF on genome architecture during epidermal barrier maintenance in normal skin, as well as promotes epidermal inflammation and tumorigenesis upon CTCF ablation.