The recently decoded white shark genome suggests why they are so indestructible



The great white shark is terribly terrifying (although it does not really pose a threat to humans). But a new study shows that the animal is also an impressive feat of evolution. For the first time, scientists claim to have totally unveiled the genome of the big white. A discovery that will help us better understand why sharks are so effective at fighting cancer and other age-related diseases – information that might one day help people do it. the same.

The study, published Monday in the Proceedings of the National Academy of Sciences, is a collaboration between researchers from many institutions, including the Monterey Bay Aquarium, the College of Veterinary Medicine of the United States. Cornell University and the Save Our Seas Foundation of Nova Southeastern University (NSU). Shark Research Center. After decoding the genome of the great white, they compared it to the genomes of a variety of other animals, including humans.

They found that the Great White was not just physically gigantic (the larger female shark is about 15 feet long and weighs up to 5,000 pounds), but also genetically: its genome is about 50% more great than ours. And within it are genes that could explain why they are so durable and resilient, according to the researchers.

On the one hand, the big white has many genes that allow him to heal quickly. These genes help shark cells repair damage and accelerate the growth of clots and new cells after a wound or injury.

The big white genes also seem to protect him from the type of self-harm that causes cancer. In general, animals with a longer lifespan (the tall whites can live over 70 years) or especially larger animals are more likely to develop harmful mutations in their cells over time, thanks to the accumulation of damage in the DNA. These mutations increase the risk of cancer and other age-related diseases. But the big white has very active genes known to prevent cells from growing in an uncontrollable way – an attribute known as genetic stability.

This protection seems particularly necessary for the large white, because its genome is filled with a certain type of DNA called transposon gene, or gene jumping. Transposons are fragments of DNA that can jump around the genome. Although this DNA shuffling can promote healthy genetic diversity within a species over a long period of time, it can also result in harmful, carcinogenic mutations in a given animal. And since the great white shark has an unusually high number of transposons, especially those called Long Intercalated Nuclear Elements (LINE), the researchers believe that they may have developed ways to protect themselves from this side effect.

"These LINEs are known to cause genome instability by creating double-strand breaks in DNA," said statement author Michael Stanhope, a biologist, in a statement. of evolution at Cornell, "It is plausible that this proliferation of LINE in the white shark selective agent genome for the evolution of effective mechanisms of DNA repair and is reflected in the positive selection and enrichment of so many genome stability genes. "

Sharks, contrary to popular belief, are not fully immune to cancer. But the results show that they are exceptionally well suited to preventing illness and other age-related ailments. And by having the Great White's complete genetic roadmap, scientists should be able to better understand how its genes are exactly protecting the cancer of the great white shark and other sharks. It is hoped that this knowledge will one day also apply to humans.

"Genome instability is a very important problem in many serious human diseases; We now find that nature has developed smart strategies to maintain genome stability in these large and long-lived sharks, "said Mahmood Shivji, director of the Shark Research Center of the Save Our Seas Foundation of the United States. NSU, ​​in a statement. "There is still much to learn from these wonders of evolution, including potentially useful information for fighting cancer and age-related diseases, and for improving wound healing treatments at home." as we discover how these animals do it. "

According to the authors, this research should also contribute to the conservation efforts of the large white, a recovering species that is recovering slowly but remains at risk.

[PNAS via NSU]

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