For more than 1,000 years, the Inupiaq people of Alaska have hunted bowhead whales in the Arctic Ocean. Over the centuries, they have been able to appreciate the long lives of these mammals, the longest on Earth, and generations of hunters could recognize the same individual in the sea. Inupiaq captains have told researchers that a bowhead whale lives two human lifetimes, but scientists suspect they can live even longer.
Some whales captured in the late 1900s had ancient harpoon points lodged in their blubber dating back to the mid-1800s. By measuring the molecular damage that accumulates in the whales’ eyes, ears and eggs, researchers have estimated that they live up to 268 years. And now, a study recently published in the journal Nature offers a clue to how animals manage to live so long: they are extraordinarily good at repairing damaged DNA.
The new study was led by Vera Gorbunova and Andrei Seluanov, a couple who work at the University of Rochester and study long-lived mammals such as bats, beavers, naked mole rats and bowhead whales. They and their colleagues are discovering many molecular adaptations that extend animal life, and according to the research, these species do so by increasing the levels of certain proteins and subtle changes in them. “We are not talking about new genes,” says Seluanov.
This finding raises the possibility that similar changes can be reproduced in humans to extend our own lives in a healthy way. “We need to tweak our system a bit to resemble what we found in naked mole rats or bowhead whales,” adds Dr.
Experiments with living samples
A bowhead whale can weigh more than 88 tons, about the same as three garbage trucks. For a single egg to give rise to a body of this size it must multiply many times, increasing the risk of a cell gaining a dangerous mutation that leads to cancer. “They are so large that they must be protected in some way, because statistically their probability of developing cancer is very high,” says Gorbunova.
All animals have some defenses against cancer, and one of them is for cells to control their own growth to prevent it from destroying itself. Scientists have long wondered whether larger animals have developed better defenses, and in 2015 evidence was found that this might be the case. Elephants have extra copies of a cancer-suppressing gene called p53, and this could help them kill cancer cells by causing them to self-destruct.
To find out if the same thing happens to whales, Gorbunova and Seluanov did something that had never been done before: they carried out experiments with cells from living specimens. Scientists who want to study the tissues of bowhead whales must make the long journey to Alaska’s North Slope, where Inupiaq whaling crews still hunt them. Scientists can ask for permission to bring whale tissue samples into their labs, but they couldn’t do it as is usually done. “If you freeze them, the cells die,” explains Seluanov.
The pair of scientists sent students to Alaska to wait for Inupiaq whalers to bring an animal ashore. A captain gave them permission to take skin and lung samples, and instead of freezing the tissue, they packed it in ice in a cooler and then flew back to Rochester as fast as they could. The cells survived.
The researchers grew populations of whale cells and did various experiments, including bombarding them with ultraviolet light, to see if the damage caused them to become cancerous. The cells proved to be resistant, but not in the same way as the elephant cells. When damaged, they do not self-destruct at high rates, but instead prevent damage from accumulating. In fact, they retrieved their DNA at a remarkably fast rate and far more accurately than other species.
Cold adaptation and cancer response
Scientists began looking for the molecules these animals used to repair their DNA and, to their surprise, discovered that whale cells produce large amounts of a protein called CIRBP. What it does is speed up the production of other proteins that protect against cold damage to cells.
Gorbunova and Seluanov also observed a large amount of CIRBP floating around the whale’s DNA. They found a single study, published in 2018, that suggests this protein might also help repair DNA. And when they inserted the bowhead whale CIRBP gene into human cells, the rate of DNA repair in those cells doubled. They also tested CIRBP in fruit flies, and found that they lived longer than those with the normal version of the gene.
The new study offers a clue as to why bowhead whales live so long: Having a large supply of CIRBP may have helped them adapt to the frigid Arctic Ocean, fight cancer and extend their longevity. The gene is found in many species, including humans, and has long been known to help us fight infections by detecting genetic material from pathogens that invade cells. Peter Sudmant, a geneticist at the University of California at Berkeley, who was not involved in the studies, argues that the results raise the possibility of finding ways to improve our own health: “Nature is a beautiful experiment from which we can get all these really fresh leads for new drugs and therapies.”
Copyright The New York Times
