加齢：ハダカデバネズミの加齢を測定する

The naked mole rat — an exceptionally long-lived rodent that outwardly seems to defy ageing — does age on the molecular level, as measured by epigenetic changes, according to a new study in Nature Aging.

Naked mole rats (Heterocephalus glaber) have exceptional longevity for rodents of their size — with a maximum lifespan of 37 years — and are resistant to age-related diseases. Epigenetic changes — modifications that change gene expression but do not alter DNA itself — in naked mole rats have been linked to ageing. However, a robust epigenetic ‘clock’ of ageing based on these modifications has yet to be presented.

Steve Horvath and colleagues analysed almost 400 samples from 11 tissue types taken from naked mole rats aged between 0 and 26 years old to measure an epigenetic change known as methylation — a naturally occurring chemical modification of DNA. As levels of DNA methylation are associated with age in humans and other species, the team created naked mole rat-specific methylation ‘clocks’ across tissues, and found that methylation estimates of age correlate very well with chronological age. The authors compared the methylation ages of non-breeding females with those of the longer-lived, dominant breeding females (queens), observing that queens have slower methylation ageing than non-breeders.

The authors conclude that although observable characteristics of naked mole rats suggest that they are ‘non-ageing’ mammals, this species does age epigenetically — similarly to other mammals. The use of epigenetic clocks, they state, might not only allow the age of wild naked mole rats to be estimated, but also aid studies investigating their potential as a model organism for ageing, longevity and disease suppression.