Will humans live to be 1000 years old? Many people would like to know how to prolong human lifespan, and so many well-funded labs are actively working on the biology of aging. One of the most interesting findings from this vast body of research is that aging is strongly correlated with DNA methylation. This work, pioneered by Steve Horvath, led to the creation of an “epigenetic clock” which predicts lifespan, and is correlated with many aspects of human health including obesity, Alzheimer’s disease, early menopause, Parkinson’s disease, and cognitive decline with age.
Studies on the biology of aging in humans must be correlational; most experimental studies use lab mice or rats to test, say, the effects of diet on lifespan or the mutations that make mice age at different rates. However, another fruitful approach to understand the biological causes of aging is an evolutionary one– studying the various mechanisms that natural selection has created for the lineages that evolved to age slowly.
Bats are exceptional among small mammals in how long they live and how slowly they age. For example, whereas a house mouse or Norway rat can live 4-5 years, I’ve met vampire bats that are 29 years old and there are other bat species that can live over 40 years. In a paper published today in Nature Communications entitled “DNA methylation predicts age and provides insight into exceptional longevity of bats“, a team of 34 biologists led by Jerry Wilkinson and Steve Horvath show that DNA methylation can be used to predict the age of bats. Many of us had DNA samples of bats of known age, so Wilkinson gathered all these samples together, and we (and by “we” I mean not me) tested an epigenetic clock for aging 712 bats from 26 species. It worked surprisingly well (at least, I was surprised). For example in six species of flying foxes (176 samples), the correlation between predicted and actual age was 0.97! For bat species used in the study, age can be estimated within a year! For bat species that were not included in the study, the correlation might be lower (about r=0.84), but that is still excellent!
Bat biologists can now take a DNA sample from a wild bat and then get an estimate of how old it is. This is a groundbreaking method for bat biologists, and it is also apparently the first study to show that an epigenetic clock can be used to accurately age wild animals. This method will almost certainly prove to be a useful tool for many future studies.
The paper also provides some general insights into how and why aging differs across species. For example, mapping the sites in the genome that were highly methylated and associated with longevity in bats, revealed many areas known to be involved in turning on or off the expression of other genes, some of which have known functions or associations with biological processes like immunity. In general, these genomic analyses suggested that bats might have extended longevity due to specific changes in their immune system and in the systems for suppression of cancer. The resulting data highlights certain gene networks for further study.
For a full ‘behind-the-paper’ story, check out this post by Danielle Adams: The epigenetics of aging in bats