Telomeres are repeat sequences of DNA at the ends of chromosomes that protect the genetic information from errors in recombination. In most birds and mammals (including humans), telomeres shorten over the lifetime of an organism through cellular division and through oxidative stress. Cellular senescence occurs when telomeres become critically short. This is associated with declines in function and an increase in mortality, often, but not always, age-related. Telomeres can be protected by antioxidant activity and repaired or lengthened by the enzyme telomerase. Restoration of telomeres through telomerase activity is common during development, but in most endotherms, telomerase activity is dramatically reduced in somatic tissues after development. This is thought to be because high telomerase activity is associated with an increased risk of cancer. In contrast, ectotherms including insects, fish and reptiles, retain the ability to repair and lengthen somatic telomeres throughout life by maintaining telomerase activity. Ectotherms may exhibit fundamental differences in telomere dynamics compared to endotherms, with important implications for age related declines in function.
Much of our early understanding of telomere dynamics has come from in vitro studies or laboratory systems, but there is an increasing focus on non-model systems both in the laboratory and in the wild. Laboratory systems are important because they provide opportunities to generate mechanistic detail. However, they stop short of addressing the issue of how telomere dynamics play out in natural populations over longer time frames. Environmental and climatic variation can have significant impacts on an animals’ life history across both temporal and spatial scales with potential implications for telomere dynamics. Telomere dynamics can vary both within and between populations and species as a result of different life history strategies, particularly through differences in growth and metabolic rate. For example, species that have greater annual reproductive output, faster growth and higher metabolism generally have greater telomere attrition and reduced longevity compared to species that grow more slowly, invest less in reproductive events and have lower metabolism. These life history patterns tend to be closely linked to climate. The effects of the thermal environment on cellular dynamics and telomere length are complex in ectotherms with many temperature-dependent processes (e.g., growth, metabolism, telomere attrition and telomerase activity) occur on different temporal scales and/or at different thermal optima. Studying how telomere dynamics respond to natural environmental factors provides a greater understanding of what influences variation in individual fitness and ultimately population and community dynamics.
Our research addresses many of the above issues. We use wild populations of the spotted snow skink (Niveoscincus ocellatus) to understand the factors that influence telomere length at birth and how telomere dynamics change across an individual’s lifetime. This system represents an ideal opportunity to examine telomere dynamics because we have a 20-year field mark and recapture study across two populations that allows us to examine a) how telomere length changes within and between individuals and b) how these individual level effects differ between populations. Individuals are tracked throughout life from birth enabling both cross-sectional and longitudinal analyses. We combined this longitudinal data with targeted experimental approaches that allow us to test the causality of some of the mechanisms that might underpin telomere dynamics. We also collaborate with Professor Mats Olsson’s lab group in Sweden, working on Sand lizards, Lacerta agilis.
If you want to know more:
Fitzpatrick, L.J., Olsson, M., Pauliny, A., While, G.M. and Wapstra, E., 2021. Individual telomere dynamics and their links to life history in a viviparous lizard. Proceedings of the Royal Society B, 288(1951), p.20210271.
Axelsson, J., Wapstra, E., Miller, E., Rollings, N. and Olsson, M., 2020. Contrasting seasonal patterns of telomere dynamics in response to environmental conditions in the ectothermic sand lizard, Lacerta agilis. Scientific reports, 10(1), pp.1-9.
Olsson, M., Geraghty, N.J., Wapstra, E. and Wilson, M., 2020. Telomere length varies substantially between blood cell types in a reptile. Royal Society open science, 7(6), p.192136.
Fitzpatrick, L.J., Olsson, M., Parsley, L.M., Pauliny, A., Pinfold, T.L., Pirtle, T., While, G.M. and Wapstra, E., 2019. Temperature and telomeres: thermal treatment influences telomere dynamics through a complex interplay of cellular processes in a cold-climate skink. Oecologia, 191(4), pp.767-776.
Fitzpatrick, L.J., Olsson, M., Parsley, L.M., Pauliny, A., While, G.M. and Wapstra, E., 2019. Tail loss and telomeres: consequences of large-scale tissue regeneration in a terrestrial ectotherm. Biology letters, 15(7), p.20190151.
Olsson, M., Wapstra, E. and Friesen, C.R., 2018. Evolutionary ecology of telomeres: a review. Annals of the New York Academy of Sciences, 1422(1), pp.5-28.
Olsson, M., Wapstra, E. and Friesen, C., 2018. Ectothermic telomeres: it’s time they came in from the cold. Philosophical Transactions of the Royal Society B: Biological Sciences, 373(1741), p.20160449.
Pauliny, A., Miller, E., Rollings, N., Wapstra, E., Blomqvist, D., Friesen, C.R. and Olsson, M., 2018. Effects of male telomeres on probability of paternity in sand lizards. Biology letters, 14(8), p.20180033.