Uncovering Novel Regulatory Pathways and Functions of the Telomerase RNA Component in the Hematopoietic System

About This Grant

PROJECT SUMMARY/ABSTRACT Mutations in telomerase cause bone marrow failure in patients suffering with dyskeratosis congenita and other associated telomere biology disorders. While mutations in these patients are found in different components of telomerase, mutations in genes that regulate the processing of the RNA component of telomerase, TERC, are the most prevalent. Due to a lack of adequate models and intrinsic difficulties in studying human telomerase in physiologically relevant cells, the molecular pathways that control TERC biogenesis and decay during hematopoiesis remain largely unknown. Progress in the field has been hampered by species and even cell-type specific differences in telomerase biology that limit our understanding of the molecular mechanisms leading to the disproportionate role of TERC in hematopoietic failure when compared to other components of telomerase. A better understanding of the molecular regulation of TERC biogenesis and function in hematopoietic cells is essential for development of novel alternatives for patients, which remain without a cure. The focus of this proposal is to use different in vitro and in vivo approaches to decipher molecular pathways controlling TERC biogenesis and decay in blood cells, as well as the function of TERC during erythroid, myeloid and lymphoid development. We have developed unique models, including targeted hematopoietic differentiation of human pluripotent stem cells, transplantation of primary CD34+ human stem cells into sub-lethally irradiated mice, and studies in primary patient samples, that will allow a complete analysis of the pathways regulating TERC decay and function during hematopoietic development. For that, two specific aims are proposed that will both identify novel regulators of TERC decay in blood cells, as well as specific functions of TERC in the hematopoietic system. Aim 1 will determine the role of novel, recently identified 3'- end RNA deadenylases to TERC processing in the blood, and to which extent different RNA deadenylases prevent TERC degradation by the exosome. We will complement these experiments with the identification of the molecular effectors of a novel route for TERC decay, triggered by differential TERC capping on its 5'- end, and mediated by trafficking to the cytoplasm. We will investigate if modulation of these different pathways can rescue hematopoietic development in telomerase mutants. Aim 2 will investigate novel functions of TERC outside telomerase that can explain the disproportionate role that mutations that affect TERC levels show in bone marrow failure. We have created unique cellular systems where we can uncouple TERC expression from telomere length, and will utilize them during hematopoietic differentiation to study direct functions of TERC on DNA damage and regulation of hematopoietic gene expression programs. These studies will determine the molecular mechanisms controlling TERC decay and function in hematopoietic cells. Our unique cellular tools, combined with our expertise in telomerase, RNA decay, and stem cell biology puts us in an ideal position to make a significant impact in this field.