Cold Spring Harbor Laboratory Conference on Telomeres and Telomerase May 4 –8, 2021 Abstract Telomeres are specialized protein-nucleic acid complexes that protect the ends of eukaryotic chromosomes. In most eukaryotes, telomeres contain short DNA repeats that are maintained by the telomerase reverse transcriptase. It has long been recognized that age and replication-associated telomere shortening is a driver of the cellular and organismal aging process, and that telomere length and integrity are regulators of human life span. Short or dysfunctional telomeres drive cells into senescence or cell death and are causative for numerous age-associated pathologies in humans, ranging from stem cell dysfunction, cognitive disorders and dementia to the age dependent increase in cancer risk. Mutations in telomere and telomerase components causing accelerated telomere shortening, such as observed in Dyskeratosis Congenita are directly associate with age-associated disorders and reduced lifespan, emphasizing the importance of understanding telomere function for the human health span and prevention of age-associated pathologies. As a result, the telomere field is now highly diverse and dynamic, representing a wide variety of research areas in which telomeres play crucial roles (aging, telomere syndromes, stem cells, cell cycle progression, cancer, meiosis and fertility, recombination, replication). The field encompasses research with mouse and human systems as well as insights gained from a wide variety of different model organisms (birds, frogs, flies, plants, nematodes, protozoa, budding yeast, fission yeast). This meeting focuses on understanding the interplay of telomeric proteins with cellular pathways that regulate genome integrity, on progress in the fields of telomerase regulation and biogenesis, on the regulation of aging and immortality by telomere maintenance pathways and on telomere dependent pathologies as function of telomere length, integrity and organismal age. The previous eleven Cold Spring Harbor Laboratory meetings on Telomeres and Telomerase have been crucial in bringing together a diverse group of researchers from all parts of the world, and have resulted in vigorous discussion and synergistic interactions stimulated by the presentation of mostly unpublished data. Because the CSHL Telomeres and Telomerase conference remains the only opportunity for scientists in this rapidly growing field to interact as a whole, this meeting is unique and of the utmost importance for the future of the field. Moreover, the format of CSHL meetings, for which nearly all talks are chosen from submitted abstracts, maximizes the opportunity for new independent investigators, postdocs and graduate students to present their work in a highly visible venue. These meetings have all had a uniformly high attendance rate from an international group of researchers, and the podium and posters have consistently presented the major discoveries in the field well before pub...