The role of cleaved-protamine 2 in sperm chromatin dynamics.

• Applicant: Dr. Lena Arevalo
• Subject Area: Reproductive Medicine, Urology ; Developmental Biology
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 396780147

Studies on reproduction, be it in medical or evolutionary contexts, have always put a great emphasis on the processes involved in sperm development and function. This is mainly due to the role these processes play in cases of male infertility and the strong evolutionary pressures on underlying genes. The packaging of paternal DNA in the sperm cell nucleus and its protection during transit is a crucial aspect of correct sperm function. Successful fertilization and embryo survival depend on the correct execution of the complete reorganization of paternal chromatin during spermatogenesis, a process unique to sperm cells. Condensation by histones does not provide the size reduction and shielding necessary for transport through the male and female reproductive tracts. Histones are therefore replaced by testes specific protamines during chromatin reorganization. The two mammalian protamines (PRM1 and PRM2) have been studied extensively in the context of male infertility as well as sperm head phenotype and are crucial to sperm function. Yet there is an essential aspect that still is a missing piece in the puzzle of sperm chromatin condensation: the processing of PRM2. While otherwise very similar to PRM1, PRM2 is produced as a longer pre-protein and processed, separating the C-terminal (DNA binding) part of PRM2 and the highly different and functionally unexplored N-terminal domain, which is cleaved off and not part of the final chromatin package in mature sperm (cleaved-PRM2). It has been shown that this processing is imperative for proper chromatin condensation and the prevention of DNA damage, yet our knowledge about this domain and its function is rudimentary at best. We propose to study the function and role of cleaved-PRM2 and its interaction with other key proteins in the regulation and execution of chromatin condensation during spermiogenesis in a mouse model. The proposed study is designed as an interdisciplinary approach, combining CRISPR/Cas gene editing and comparative evolutionary methodologies. This will give us the unique opportunity to gain insight into the molecular basis of the organization and protection of the paternal genome and advance our understanding of the involvement of protamine-mediated DNA reorganization in male infertility.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Hubert Schorle