The great white shark is impressively terrifying (though not actually much of a threat to humans). But a new study shows that the animal is also an impressive feat of evolution. For the first time, scientists say they’ve fully unspooled the genome of the great white, a discovery that will help us better understand why sharks are so good at warding off cancer and other age-related diseases—information that could someday help people do the same.
The study, published Monday in the Proceedings of the National Academy of Sciences, was a collaboration between researchers at many institutions, including the Monterey Bay Aquarium, the Cornell University College of Veterinary Medicine, and the Nova Southeastern University (NSU) Save Our Seas Foundation 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 isn’t just gigantic physically (the larger female shark is around 4.57m long and weighs up to 5,000 pounds), but genetically, too: Its genome is about 50 per cent larger than ours. And nestled within it are genes that could explain why they’re so durable and resilient, according to the researchers.
For one, the great white has many genes that help it heal quickly. These genes help shark cells repair damage and speed up the growth of clots and new cells after a wound or injury.
The great white’s genes also seem to protect it from the sort of self-injury that causes cancer. Typically, animals that have longer lifespans (great whites can live over 70 years) or that are particularly big are more likely to develop harmful mutations in their cells over time, thanks to accumulating DNA damage. These mutations raise the risk of cancer and other age-related diseases. But the great white possesses highly active genes known to prevent cells from growing out of control—an attribute known as genetic stability.
That protection seems especially needed for the great white, since its genome is filled with a certain type of DNA known as a transposon, or jumping gene. Transposons are bits of DNA that can jump around the genome. While this DNA shuffle can promote healthy genetic diversity in a species over a long period of time, it can also lead to harmful, cancer-causing mutations in an individual animal. And because the great white shark has an unusually high number of transposons, particularly those called long interspersed nuclear elements (LINEs), the researchers believe they may have evolved ways to buffer themselves from this side-effect.
“These LINEs are known to cause genome instability by creating double stranded breaks in DNA,” study author Michael Stanhope, an evolutionary biologist at Cornell, said in a statement “It’s plausible that this proliferation of LINEs in the white shark genome could represent a strong selective agent for the evolution of efficient DNA repair mechanisms, and is reflected in the positive selection and enrichment of so many genome stability genes.”
Sharks, contrary to popular belief, aren’t entirely immune to cancer. But the findings do affirm that they’re exceptionally well-suited at preventing it and other age-related ailments. And by having the great white’s full genetic roadmap available, scientists should be better able to unravel just how exactly its genes protect the great white and other sharks from cancer. That knowledge, it’s hoped, could one day apply to humans as well.
“Genome instability is a very important issue in many serious human diseases; now we find that nature has developed clever strategies to maintain the stability of genomes in these large-bodied, long-lived sharks,” Mahmood Shivji, director of the NSU Save Our Seas Foundation Shark Research Center, said in a statement. “There’s still tons to be learned from these evolutionary marvels, including information that will potentially be useful to fight cancer and age-related diseases, and improve wound healing treatments in humans, as we uncover how these animals do it.”
This research, the authors said, should also help with conservation efforts for the great white, a slowly rebounding but still endangered species.