The pathophysiological relevance of the histone variant H2A.J in radiation-induced, premature senescence

• Applicant: Professorin Dr. Claudia Rübe
• Subject Area: Nuclear Medicine, Radiotherapy, Radiobiology
• Term: from 2018 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 394229105

The long term side effects following radiotherapy can be traced back to the accumulation of dysfunctional senescent cells combined with the reduced proliferative potential of tissue-specific stem cells; to date the pathomechanisms however remain unclear. In our preliminary studies, we have characterized the novel histone variant H2A.J, whose integration into chromatin increases following ionizing radiation and additionally is associated with cellular senescence.The aim of this research project is to investigate the importance of the histone variant H2A.J in relation to radiation-induced, premature senescence both in-vitro and in-vivo. The molecular biological relationship between radiation-induced DNA damage, local chromatin modifications and subsequent global reorganization of the chromatin architecture is to be investigated using comparative studies between H2A.J+/+ and H2A.J-/- fibroblasts through the means of light- and electron microscopy. Additionally, the alterations in chromatin organization and nuclear integrity shall be structurally and functionally characterized using multi-parametric flow cytometry. The application of high-resolution, precise 3D reconstruction of the entire cell nucleus shall be used to uncover the connections between the chromatin integration of H2A.J following irradiation and the functional reorganization of chromatin.Furthermore, the functionality of H2A.J is to be investigated in the complex tissue configuration of the skin, during and after irradiation. Located in the murine epidermis is the hair follicle and its bulge region which presents an ideal model for the analysis of the differentiation processes of epidermal stem cells. To examine the effect on tissue homeostasis, the radiation-induced DNA damage in different stem cell populations shall be correlated with the chromatin integration of H2A.J and collated with proliferation, differentiation, apoptosis and senescence respectively. Analysis of the specific function of H2A.J in the epidermis shall be inspected in transgenic H2A.J-/- mice. In specific, how the missing H2A.J expression influences premature senescence or, as the case may be, the untimely differentiation of epidermal stem cells, following irradiation. The use of BrdU labeling will capture the division rate, as well as, the self-renewal of the stem cell population and, combined with H2A.J detection, will be collated with premature differentiation. As increased migration of stem cells from their niche leads to a reduced regeneration capacity of the hair follicle in the long term, the functional endpoint of hair growth and coloring shall be analyzed.Overall, the pathophysiological relevance of the histone variant H2A.J in radiation-induced, premature senescence and the untimely differentiation of epidermal stem cells respectively, is to be investigated to uncover possible starting points for the development of a corrective pharmacological therapy.

• DFG Programme: Research Grants