Role of Histon H2A deubiquitinase 2A-DUB/Mysm1 in lymphoid development and interaction with p53-mediated apoptotic programs

• Applicant: Privatdozentin Dr. Martina Gatzka
• Subject Area: Dermatology ; Immunology
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 266397124

Sequential differentiation of specialized cell populations from pluripotent progenitors requires the collaboration of histone modifying and chromatin remodeling enzymes with sequence-specific DNA binding transcription factors (TF) in larger multi-protein complexes to activate and silence lineage-specific genes in a coordinated manner. Histone H2A deubiquitinase 2A-DUB/Mysm1, an epigenetic regulator highly expressed in lymphocytes and the skin, potentially fulfills several critical functions at different stages of hematopoietic and skin development: 1. In the DNA-damage response (DDR) required for efficient somatic recombination of T cell receptor (TCR) and immunoglobin (Ig) genes during early lymphocyte development. 2. In regulating access of sequence-specific TFs to DNA during differentiation of lymphocytes and skin cells. 3. In the DDR induced by reactive oxygen species (ROS) and irradiation. Therefore, H2A deubiquitination by 2A-DUB/Mysm1 might be involved in regulating protection from autoimmunity, lymphoma and cancer. Because mice with an engineered deficiency in 2A-DUB/Mysm1 (Mysm1 KO mice) have a number of defects in T cell and skin development - including severe thymus hypoplasia along with altered activation of peripheral T cells, skin atrophy and premature aging -, we propose here to characterize the role of Mysm1 in T cells, the skin, and in associated diseases using genetic, immunological and molecularbiological approaches. Based on the applicants preliminary data identifying the Ink4/ARF pathway as potential mediator of increased apoptosis and reduced proliferation rates in Mysm1-deficient thymocytes and epidermal cells, the interplay of 2A-DUB/Mysm1 with the p19ARF/Ink4a promoter will be investigated and verified in our newly generated p53-/-Mysm1-/- and Cdkn2a/ARF-/- Mysm1-/- double-KO (DKO) mice. The role of histone H2A deubiquitination by Mysm1 in thymocyte development and selection will be explored in Lck-Cre x Mysm1flox/flox mice as well as in p53-/-Mysm1-/- DKO and H-Y TCR transgenic mice. Additional molecular interactions and binding partners of Mysm1 in T cell and skin cell populations will be verified by ChIP-based approaches. Ultimately, the impact of potential alterations in the T cell repertoire or in genetic instability in T cells and skin cells as a consequence of Mysm1-deficiency will be explored in autoimmune and tumor models in a translational approach. This investigation aims at providing a better understanding of how epigenetic mechanisms interact with lineage-specific TFs and differentiation programs to regulate T cell and skin development and how epigenetics contribute to the prevention of autoimmunity and cancer.

• DFG Programme: Research Grants