The Role of Telomere Clustering and Compaction in Cellular Senescence
Date
2020-06-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Chronological age is highly correlated with the development of numerous diseases, including cancer. Thus, delaying the onset of cellular aging should increase healthspan and reduce the period of morbidity that is seen as one approaches maximal lifespan. One of the main contributors to age-related diseases is replicative senescence, which is induced by a telomere-specific DNA damage response. This highly regulated pathway is modulated by an interplay between telomere length and shelterin proteins, such as Telomere Repeat-binding Factor 2 (TRF2). Since telomeres shorten with each cell division, telomere length has been used as a biomarker for cellular aging. However, many cancer cells display short telomeres despite their continued replicative capability. This indicates that cells can extend their cellular lifespan with relatively short telomeres if other factors are in place. Here, we have developed a method for 3D quantitative immunofluorescence microscopy of telomeres in interphase cells that includes image acquisition, processing and analysis to accurately determine telomere count, length and volume. Using this technique, we observed that long telomeres in telomerase-immortalized cells as well as DNA damage positive-telomeres in replicatively senescent cells can cluster, resulting in lower telomere counts. Analysis of individual telomeres by super-resolution microscopy techniques showed that telomeres in senescent cells have significantly more damage foci and are less dense when compared to low passage replicating cells. Alternatively, cell strains with short telomeres, but elevated TRF2 levels, showed more telomere compaction which correlated with an absence of DNA damage responses and increased replicative lifespan. These results show that telomere compaction, rather than average telomere length, may be more indicative of both cellular senescence and immortality, and provides novel insights into the key mechanisms involved in the development of age-related diseases due to the accumulation of senescent cells.
Description
Keywords
Telomeres, Cellular Senescence, DNA damage response, Super-resolution microscopy, Telomere compaction
Citation
Adam, N. J. (2020). The Role of Telomere Clustering and Compaction in Cellular Senescence (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.