Telomerase RNA component, terc, in aging and cancer

Laburpena

Nowadays there is a great interest in delaying the process of aging to improve life expectancy and quality, mainly due to the associated diseases that emerge with it, including cancer. It is extensively known that telomerase and telomeres are involved in the aging process, as telomere attrition is one of the primary hallmarks of aging, among others. Cancer is an important disease that is not exclusively associated with aging, and its initiation and progression depend on many genetic and environmental factors. The telomerase enzyme is directly related with aging and cancer because of its function in telomere maintenance, but also, many non-canonical functions are being described for its two main components, telomerase catalytic subunit (TERT) and telomerase RNA (TERC), being a remarkable one the non-canonical function that TERC has in myelopoiesis. With the increasing interest of using the zebrafish as an animal model, studies about telomeres and telomerase in this species have emerged due to similar telomere length and conservation regarding telomerase components. Also, since the zebrafish has been widely used for disease modelling, it has a great importance in the cancer field. Importantly, the zebrafish has been also used to model leukemia and myeloid malignancies. During the development of this Doctoral Thesis we used the zebrafish animal model to study the effect of the RNA component of telomerase deficiency on aging, hematopoiesis and myeloid proliferation driven by an oncogene. So, that mains objectives were the characterization of the zebrafish terc mutant line aging and hematopoietic phenotypes, and also, the development and characterization of a zebrafish myeloid proliferation model using oncogene expression. For these purposes, we used and manipulated the zebrafish animal model, including maintenance, breeding, and dissecting and also applied many cellular and molecular biology techniques. These include, gene expression analysis, measurement of telomerase activity, in situ hybridization techniques, flow cytometry, histology and cytology techniques, staining on whole zebrafish embryos to label specific cellular lineages, survival analysis, etc. First, we show that terc is expressed from early stages of development and has different expression levels depending on the tissue of adult fish. Next, the terc mutant zebrafish line study concluded that this line has an increased telomere shortening due to absence of telomerase activity, presents premature aging signs and a reduced lifespan in the first generation. Also, terc deficient zebrafish larvae showed hematopoietic defects that affect myelopoiesis, which is not observed in adult fish. This model will help investigate terc roles in aging and cancer, as well as non-canonical functions. Second-generation terc-deficient zebrafish cannot reach adult stage and present aging hallmarks at very short time points, making it a very adequate model for anti-aging drug screening. We developed a model of hyperactivated human HRAS oncogene expression in neutrophils that showed neutrophil expansion and dispersion phenotype that can be ameliorated in terc, but not tert, deficiency conditions. Adult zebrafish model does not show myeloid malignancy signs or leukemia development. Nevertheless, this model has a reduced lifespan and develop a wide range of solid tumors with benign nature.