Periodic Reporting for period 1 - coDNAres (Regulation of DNA resection, DNA repair and genomic stability by cohesin in undifferentiated Caenorhabditis elegans germ cells)
Período documentado: 2021-10-01 hasta 2023-09-30
DNA double-strand breaks (DSBs) are the most hazardous type of DNA damage threatening genomic stability. In response to this challenge, eukaryotes have evolved conserved mechanisms for DNA damage response and repair pathways. Although these pathways are highly conserved, they are not fully understood. Maintaining a balance between error-prone mechanisms, such as Non-Homologous End-Joining (NHEJ), and high-fidelity mechanisms, such as Homologous Recombination (HR), is crucial for cell fitness. This balance is particularly exerted at the level of licensing HR through the initial step of the pathway known as DNA end resection. Therefore, a comprehensive study of this step is essential for understanding genetic diseases, such as cancer, and holds significant potential for guiding future therapeutic strategies.
Cohesin complexes, with their tripartite ring-like structure, are highly conserved factors known for their roles in preventing genome instability. The cohesin complex consists of three subunits, and the kleisin subunit varies between mitotic and meiotic phases—Rad21/Scc1 during mitosis and Rec8 during meiosis. It has been described roles for cohesin in chromosome segregation and DNA repair, but as short, all based in providing close proximity of sister chromatids. But little it’s known about an active function in DNA repair further tethering DNA molecules, e. g. participating in the decision of NHEJ/HR pathway or mediating early DNA resection. Unraveling how cohesin regulates various aspects of DNA metabolism is not only a crucial biological question but also holds clear relevance for human health.
This project aimed to challenge and expand the preconceived notions of mitotic and meiotic cohesin complexes, particularly exploring the potential roles of the REC-8 kleisin outside of meiosis. Additionally, it sought to illuminate cohesin-specific functions of different complexes and compare the active contributions of SCC-1- and REC-8-cohesin complexes in various aspects of DNA metabolism, including DNA resection and repair. Using Caenorhabditis elegans as a model system provided a unique opportunity to study systemic DNA damage response mechanisms in a tissue-specific manner, focusing on mitotically proliferating undifferentiated germ cells and embryonic development. The project successfully achieved all its objectives, both scientifically and from a career point of view.
Cohesin complexes, with their tripartite ring-like structure, are highly conserved factors known for their roles in preventing genome instability. The cohesin complex consists of three subunits, and the kleisin subunit varies between mitotic and meiotic phases—Rad21/Scc1 during mitosis and Rec8 during meiosis. It has been described roles for cohesin in chromosome segregation and DNA repair, but as short, all based in providing close proximity of sister chromatids. But little it’s known about an active function in DNA repair further tethering DNA molecules, e. g. participating in the decision of NHEJ/HR pathway or mediating early DNA resection. Unraveling how cohesin regulates various aspects of DNA metabolism is not only a crucial biological question but also holds clear relevance for human health.
This project aimed to challenge and expand the preconceived notions of mitotic and meiotic cohesin complexes, particularly exploring the potential roles of the REC-8 kleisin outside of meiosis. Additionally, it sought to illuminate cohesin-specific functions of different complexes and compare the active contributions of SCC-1- and REC-8-cohesin complexes in various aspects of DNA metabolism, including DNA resection and repair. Using Caenorhabditis elegans as a model system provided a unique opportunity to study systemic DNA damage response mechanisms in a tissue-specific manner, focusing on mitotically proliferating undifferentiated germ cells and embryonic development. The project successfully achieved all its objectives, both scientifically and from a career point of view.
Throughout this project, we have uncovered roles of REC-8 outside of meiosis, contributing to genome stability in mitotically proliferating tissues. Both REC-8 and SCC-1 play crucial roles in preventing the accumulation of DNA damage, proving essential for the genome stability of proliferating tissues. Alterations in normal REC-8 or SCC-1 levels result in defects in germ cells and embryonic development, due to defects in chromosome segregation and DNA repair. The project has also introduced novel biochemical approaches, including the measurement of DNA break accumulation in single cells through the COMET assay and the utilization of laser beam irradiation to examine subnuclear-stripped UVC-damaged regions in C. elegans' germline and embryo cells. These innovative methods will significantly help to advance in the study of DNA damage and repair in the nematode.
The project's findings have been disseminated within the scientific community through conferences and workshops, and are expected to be published within a year.
The project's findings have been disseminated within the scientific community through conferences and workshops, and are expected to be published within a year.
The outcomes of this project have provided insights into how cells respond to DNA stress, orchestrating a robust DNA Damage Response and preventing the accumulation of DNA damage, a phenomenon associated with human diseases like cancer. Additionally, comprehending how cohesin complexes contribute to genome stability in the germ cells of higher eukaryotes may have implications for our understanding of human syndromes known as cohesinopathies. These syndromes are linked to mutations in cohesin subunits and are associated with sterility, birth defects, and genetic diseases, including cancer.
Moreover, the prevention of genome instability in germ cells is crucial for the survival of species, as mutations originating in germ cells can be inherited by all cells in the offspring. From a different perspective, this study has potential long-term applications in cancer therapies, such as personalized treatment targets or the utilization of modified cohesin versions to selectively eliminate cancer cells.
Moreover, the prevention of genome instability in germ cells is crucial for the survival of species, as mutations originating in germ cells can be inherited by all cells in the offspring. From a different perspective, this study has potential long-term applications in cancer therapies, such as personalized treatment targets or the utilization of modified cohesin versions to selectively eliminate cancer cells.