- By James Gallagher
- Health and Science Correspondent
According to a study, the useful life of animals is related to the rate of mutation in their genetic code.
Researchers have found that mammals, from tigers to humans, have about the same number of mutations when they die of old age.
But short-lived animals tend to deplete their allocation more quickly, according to the analysis of 16 species.
According to researchers, this discovery helps explain why we age and sheds light on one of the most complex mysteries of cancer.
Experts said the results, obtained by researchers at the Wellcome Sanger Institute, were “surprising” and “thought-provoking.”
Mutations are changes that are incorporated into the instruction manual for the construction and functioning of our body: our DNA.
These mutations have long been known to cause cancer, but it has been debated for decades whether they are important for aging. Sanger researchers claim to have produced “the first experimental evidence” to suggest that they are.
They analyzed the rate at which mutations occur in species with different life expectancies. They examined the DNA of a cat, a black and white colobus, a dog, a ferret, a giraffe, a horse, a human, a lion, a mouse, a naked mole rat, a rabbit, a rat, a ring . -tail tail lemur and a tiger.
The study, published in the journal Nature, shows that mice suffer from about 800 mutations a year during their short lifespan, which lasts just under four years.
The longer the animals live, the less mutations they undergo each year.
Dogs have about 249 mutations a year, 160 lions and 99 giraffes, compared to an average of 47 humans.
One of the researchers, Dr. Alex Cagan, calls this pattern “impressive” and that it is “really amazing and exciting” that all the animals studied have converged on “about 3,200” mutations in their lifetime.
If human DNA mutated at the same rate as mice, we would die with more than 50,000 genetic alterations.
“Despite having a different lifespan, at the end of their life mammals had the same number of mutations,” Dr Cagan told the BBC.
“It’s the number, but what does it mean? It’s a mystery to us,” the researcher continues.
It is possible that the cells in the body reach a critical number of mutations and then become extinct. There are also ideas that “a few [cellules] misbehaving ”begins to take over vital tissues, such as the heart, as we age, so that organs no longer function properly.
However, it is unlikely that aging is due to a single process within the cells of our body.
Telomere shortening and epigenetic changes are also thought to play a role. However, if mutations are involved, one wonders if there are ways to curb the genetic damage or even repair it.
Researchers want to see if this pattern applies to lifelong or only mammals. They plan to add fish to the analysis, including a Greenland shark, which can be over 400 years old and is the longest-lived vertebrate in the world.
The cancer paradox
In the field of oncology, there is an enigma known as the “Peto paradox”: why do large, long-lived animals not have very high cancer rates?
The more cells in your body and the longer you live, the more likely you are to get cancerous. This should be terrible news for elephants and whales.
“Whales have trillions more cells [que nous]. They shouldn’t exist because they have cancer before adulthood, “says Dr. Cagan.
Older animals tend to live longer, so their slower mutation rate could help explain the paradox, but researchers say it is far from the only explanation.
Naked mole rats and giraffes live at about the same age, with similar mutation rates, although giraffes are thousands of times larger.
“The giraffe’s mutation rate would be expected to be even lower, but it’s as if body size didn’t matter,” says Dr. Cagan.
Instead, researchers say, other methods of cancer suppression may have evolved, which could inspire new cancer treatments. For example, elephants have more copies of a DNA fragment that suppresses tumors.
Dr. Alexander Gorelick and Dr. Kamila Naxerova of Harvard Medical School say that the gap between 47 human mutations a year and 800 mouse mutations is huge.
“This difference is striking, given the broad general similarities between the human and mouse genomes.
“These results are worrisome.”
Dr Simon Spiro, a veterinarian for wildlife at the London Zoological Society, says: “Animals often live much longer in zoos than in nature, so our veterinarians often spend time managing conditions related to old age.
“The genetic changes identified in this study suggest that diseases of old age will be similar in a wide range of mammals, whether the age begins at seven months or 70.”