Patterns of telomere length with age in African mole-rats : new insights from quantitative fluorescence in situ hybridisation (qFISH)

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Authors

Leonida, Stephanie R.L.
Bennett, Nigel Charles
Leitch, Andrew R.
Faulkes, Christopher G.

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PeerJ

Abstract

Naked mole-rats Heterocephalus glaber (NMRs) are the longest-lived rodent and also resist the normal signs of senescence. In a number of species, cellular ageing has been correlated with a reduction in telomere length, yet relatively little is known about telomeres and their age-related dynamics in NMRs and other African mole-rats. Here, we apply fluorescence in situ hybridisation (FISH) to quantify telomeric repeat sequences in the NMR, the Damaraland mole-rat, Fukomys damarensis (DMR) and the Mahali mole-rat, Cryptomys hottentotus mahali (MMR). Both terminal and non-terminal telomeric sequences were identified in chromosomes of the NMR and DMR, whilst the MMR displayed only terminal telomeric repeats. Measurements of tooth wear and eruption patterns in wild caught DMRs and MMRs, and known ages in captive bred NMRs, were used to place individuals into relative age classes and compared with a quantitative measure of telomeric fluorescence (as a proxy for telomere size). While NMRs and MMRs failed to show an age-related decline in telomeric fluorescence, the DMR had a significant decrease in fluorescence with age, suggesting a decrease in telomere size in older animals. Our results suggest that among African mole-rats there is variation between species with respect to the role of telomere shortening in ageing, and the replicative theory of cellular senescence.

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Additional File 1: Complete metaphase spread of Cryptomys hottentotus mahali (male 12.3) chromosomes. DNA is stained blue (with DAPI) and telomeres in red (with Cy3 PNA probe). 2n=53, as reported for males in other Cryptomys species (2n=54 for females due to a Y-chromosome-autosome translocation in males; Deuve et al., 2007). DOI: 10.7717/peerj.10498/supp-1
Additional File 2: Telomere size variation with age in naked mole-rats. Scatter plot of mean ± SEM telomere size variation (expressed as volume of telomere fluorescence) with age for the naked mole-rats show in Figure 2. Points correspond to an individual animal (n=50 cells counted in each). DOI: 10.7717/peerj.10498/supp-2
Additional File 3: qFISH telomere fluorescence measurements. Each value is the fluorescence measurement per cell together with individual identity and age class for each species (separate tabs) as follows: Damaraland mole-rat, DMR; Mahali mole-rat, MMR; and naked mole-rat, NMR. DOI: 10.7717/peerj.10498/supp-3
Additional File 4: Details of Damaraland mole-rat Fukomys damarensis (DMR), Mahali mole-rat Cryptomy hottentotus mahali (MMR) and Heterocephalus glaber (NMR) samples. Age class based on molar tooth eruption and wear for DMR and MMR (Bennett, Jarvis & Wallace, 1990), or absolute age in years for NMR. Age category as described in methods. Shaded rows correspond to NMR samples with too few cells to count, not included in the final analysis. DOI: 10.7717/peerj.10498/supp-4

Keywords

Non-terminal telomeric repeats, Heterocephalidae, Telomere length, Cellular senescence, Fukomys, Heterocephalus, Cryptomys, African mole-rats (Bathyergidae), Fluorescence in situ hybridisation (FISH), Damaraland mole-rat (Fukomys damarensis), Mahali mole-rat (Cryptomys hottentotus mahali )

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Citation

Leonida, S.R., Bennett, N.C., Leitch, A.R. et al. 2020. Patterns of telomere length with age in African mole-rats: New insights from quantitative fluorescence in situ hybridisation (qFISH). PeerJ 8:e10498 DOI 10.7717/peerj.10498.