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Epigenetic imprinting by DNA demethylation - T lymphocyte effector/memory cell differentiation as a model system

Prof. Thiel (first supervisor), Prof. Radbruch (second supervisor), Dr. Dong (mentor); Charité

Epigenetic modifications at DNA level by cytosine methylation/demethylation are essential in the control of several aspects of mammalian development, including parental imprinting, X chromosome inactivation, and tissue-specific expression of genes. DNA methylation has also been implicated in the initiation and progression of many pathologies including cancer. While maintenance and de novo DNA methylation are relative well understood, the mechanisms that underlie demethylation remain unclear. It is not clear whether imprinting of genes is due to the inhibition of de novo methylation and/or by active demethylation. During lineage differentiation of human naïve Th cells into IFN- γ-producing effector/memory Th1 cells, we observed dynamic demethylation of the IFNG gene locus. The question is now how demthylation is imprinted to the IFNG gene and lineage transcription factors, such as Tbet, GATA-3 and RoRγt.
We are dedicated to address the mechanisms of DNA demethylation imprinting using T lymphocyte effector/memory cell differentiation as a model system and by applying highly competitive research approaches. We will use a genome-wide shRNA library to identify shRNAs that inhibit IFN-γ production by highthroughput flow cytometry. We will then validate candidate genes that block demethylation imprinting of the IFNG gene and transcription factor genes by nextgeneration deep sequencing and/or in vitro functional assays. One central goal of this project is to find common mechanisms of demethylation by testing candidate genes in different developmental systems. This project will promote us not only to understand the epigenetic imprinting of immunological function and memory Th1 cells, but also to reveal general mechanisms of epigenetic imprinting by demethylation. In addition, this project will identify potential targets for the treatment of immune-mediated diseases.

References
Dong J, Ivascu C, Chang HD, Wu P, Angeli R, Maggi L, Eckhardt F, Tykocinski L, Haefliger C, Möwes B, Sieper J, Annunziato F, Radbruch A, Thiel A. IL-10 is excluded from the functional memory of human CD4+ memory T lymphocytes. J. Immunol. 2007; 179:2389-96.

Ivascu C, Wasserkort R, Lesche R, Dong J, Stein H, Thiel A, Eckhardt F. DNA methylation profiling of transcription factor genes in normal lymphocyte development and lymphomas. Int J Biochem Cell Biol. 2007; 39:1523-38.