Abstract
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.
Highlights
Telomeres are nucleo-protein complexes that protect the ends of linear chromosomes, principally by preventing chromosome ends from fusing or being recognized as double strand DNA breaks[1]
We hypothesized that exposure to environmental radionuclides within the Chernobyl Exclusion Zone (CEZ) is likely to impact telomere homeostasis as telomeres present a specific target for damaging effects of ionizing radiation (IR) because G-rich regions of the genome are expected to be radiosensitive
Relative telomere lengths were estimated in liver, brain, heart, testis and ovary tissue from bank voles within the CEZ and control animals from Ukraine which were not exposed to increased levels of ambient background radiation in their environment
Summary
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]. Diverse genomic impacts have been reported in wildlife inhabiting the areas surrounding Chernobyl[25], including elevated levels of DNA damage[28] and mutations[27]. IR induced increase in cellular reactive oxygen species (ROS) and oxidative stress can disrupt telomere maintenance, as telomeres are sensitive to oxidative damage[5,19,29] Both TL and telomerase expression are linked with radiosensitivity in vitro: cell lines with short telomeres show increased radiosensitivity when they lack a functioning telomerase[19] ( in vivo in mice[30]). Other cell lines show a reduction in telomere length and an increase in telomerase expression after exposure to ionizing radiation[31], and radiosensitive cells have accelerated telomere shortening and telomere dysfunction[32,33]. The extent to which wildlife experiencing a chronic, low dose exposure of ionizing radiation parallel these studies of cell lines exposed to acute, high doses of radiation (e.g. for clinical context) is unknown
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