LONDON, 8 October, 2019 − Grey whales are one of the longest-lived mammals in existence. The secret to their long lives? A resilience to stress, according to the first genetic sequencing of the animals.
The genes for stress resistance are also shared by other long-lived animals, like naked mole rats, which can outlive mice by 25 years, give or take, and humans. It is this stress resistance that protects most long-lived animals from cancer, says Dmitri Toren, now at the Romanian Academy in Bucharest.
Toren and his colleagues are investigating ageing and why some animals are able to live long lives. The team decided to study the grey whale because it can live into its 70s, and is considered to be the eighth longest-lived mammal.
In order to study cells taken from grey whales, a member of the team had to travel to Chukotka, an autonomous area of Russia, where annual whale hunts are regulated by the International Whaling Commission. “It was challenging to get a biopsy,” says Toren. “He had to fly there and wait for half a year.”
Once the team had liver and kidney tissue from two grey whales, the researchers looked at the genes that were switched on in each sample. They sorted expressed genes into categories based on their functions, and focused on those that had previously been linked to ageing. These included proteins that affect how well the body can get rid of faulty proteins and maintain and repair DNA, as well as others involved in the workings of the immune system.
Toren and his colleagues then compared the levels of gene expression to that of two other long-lived whales – the bowhead and minke whale – as well as the relatively short-lived mouse, the cow and the relatively long-lived human and naked mole rat. All of the animals were young adults.
It is difficult to compare individual genes across species, so instead, the team ranked the expression of genes based on their functions for each species. When they compared these rankings between species, they found that long-lived animals had higher levels of gene expression associated with the maintenance of DNA and immune cells, and the flushing out of damaged proteins. This may explain why whales are thought to be protected from cancer.
“Suggesting that stress resilience is important is a very plausible hypothesis,” says Lorna Harries at the University of Exeter, UK. “We know that your molecular stress response tends to decline with age… so it’s not surprising that’s one of the things that has been picked out.”
Harries points out that the researchers may have missed some differences between the animal species, and that, given the team were only able to study two grey whales, more research is needed to confirm their findings.