Exposure to environmental radionuclides associates with tissue-specific impacts on telomerase expression and telomere length

International audience; Telomeres, the protective structures at the ends of chromosomes, can be shortened when individuals are exposed to stress. In some species, the enzyme telomerase is expressed in adult somatic tissues, and potentially protects or lengthens telomeres. Telomeres can be damaged by ionizing radiation and oxidative stress, although the effect of chronic exposure to elevated levels of radiation on telomere maintenance is unknown for natural populations. We quantified telomerase expression and telomere length (TL) in different tissues of the bank vole Myodes glareolus, collected from the Chernobyl Exclusion Zone, an environment heterogeneously contaminated with radionuclides, and from uncontaminated control sites elsewhere in Ukraine. Inhabiting the Chernobyl Exclusion Zone was associated with reduced TL in the liver and testis, and upregulation of telomerase in brain and liver. Thus upregulation of telomerase does not appear to associate with longer telomeres but may reflect protective functions other than telomere maintenance or an attempt to maintain shorter telomeres in a stressful environment. Tissue specific differences in the rate of telomere attrition and apparent radiosensitivity weaken the intra-individual correlation in telomere length among tissues in voles exposed to radionuclides. Our data show that ionizing radiation alters telomere homeostasis in wild animal populations in tissue specific ways. Telomeres are nucleo-protein complexes that protect the ends of linear (i.e. eukaryotic) chromosomes, principally by preventing chromosome ends from fusing or being recognized as double strand DNA breaks 1. Almost all vertebrate telomere sequences are composed of the motif TTAGGG that is repeated as a long, tandem array. Telomere length (TL) is reduced with cell division due to incomplete end replication 1 , with cell senescence triggered at a critically short TL 2. As TL is widely correlated with longevity, health and fitness in humans and other animals, there is much interest in understanding the processes that impact TL dynamics. Stressors, such as psychological stress 3,4 , oxidative stress 5,6 and environmental pollution 7 , correlate with accelerated rate of telomere shortening in humans and animals. Telomere length homeostasis is more complex than the rate of shortening per se. A key mechanism by which telomeres may be repaired or extended is by the action of the enzyme telomerase 8. Telomerase expression varies among tissues and among species 9,10. Notably, small (~2 kg or less) rodents 9,11,12 and some birds 13 express telomerase in many somatic tissues as adults; conversely, many large long-lived mammals repress telomerase