Although it is not really a great threat to humans, the great white shark is a terrifying creature. A new genetic study has just revealed that the great target is also an impressive feat of evolution.
For the first time, scientists have fully unraveled the great white genome, a discovery that will help us better understand why sharks are so effective in preventing cancer and other age-related diseases. That information may one day save our lives, or lengthen it.
The study, published Monday in the Proceedings of the National Academy of Sciences, is a collaboration between researchers at many institutions, including the Monterey Bay Aquarium, the Faculty of Veterinary Medicine at Cornell University and the University of Cornell Research Center. sharks from the Nova Oureast Foundation of the Southeast (NSU). After deciphering the genome of the great white, they compared it to the genomes of other species that we already know in their entirety, including humans.
They discovered that the great white is not only physically gigantic (the largest female shark is around 4.6 meters long and weighs up to 2,267 kilograms), but also genetically. Its genome is approximately 50 percent larger than ours. And within it there are genes that could explain why it is such a durable and resistant species.
On the one hand, the great white has many genes that help it heal quickly. These genes help shark cells repair damage and accelerate the growth of clots and new cells after a wound or injury.
The great genes of whites also seem to protect it from the type of self-harm that causes cancer. In general, animals that have a longer lifespan (large whites can live more than 70 years) or that are particularly large are more likely to develop harmful mutations in their cells due to the progressive accumulation of DNA damage. These mutations increase the risk of cancer and other age-related diseases, but the large target has highly active genes known to prevent cells from growing out of control. That attribute is known as genetic stability.
That protection seems especially necessary for the great target, since its genome is full of a certain type of DNA known as transposon, or jumping gene. Transposons are fragments of DNA that can move around the genome. This random combination of DNA can promote a healthy genetic diversity in a species over a long period of time, but it can also cause harmful and cancer-causing mutations in an individual animal. The great white shark has an unusually high number of transposons, particularly the so-called long intercalated nuclear elements (LINE). The researchers believe that they may have developed genetic mechanisms to protect themselves from this side effect. Michael Stanhope, evolutionary biologist at Cornell and one of the authors of the study explains:
It is known that these LINEs cause instability in the genome by creating double-strand breaks in the DNA. It is plausible that this proliferation of LINE in the white shark genome may represent a selective agent for the evolution of efficient DNA repair mechanisms. This translates into the positive selection and enrichment of so many genes for genome stability.
Sharks, contrary to popular belief, are not completely immune to cancer. But the findings do confirm that they are exceptionally good at preventing tumors and other age-related diseases. By having available the complete genetic road map of the great target, scientists can find out how these genes exactly protect the great white and other cancer sharks. That knowledge could be applied to humans someday. Mahmood Shivji, director of the Shark Research Center at the NSU Save Our Seas Foundation adds:
Genome instability is a very important issue in many serious human diseases. We now know that nature has developed intelligent strategies to maintain the stability of genomes in these large, long-lived sharks. There is still much to be learned from these evolutionary wonders, including information that could be useful in combating cancer and age-related diseases, as well as improving wound healing treatments in humans, as we discover how these animals do.