Analysis: new research into the great white shark could aid the development of new life-enhancing human treatments
Sharks have been roaming the oceans for an estimated 400 million years so they even predate dinosaurs by around 150 million years. There are over 400 different species in the shark family, though we still know very little about them.
Peter Benchley's 1974 novel Jaws and Steven Spielberg's 1975 blockbuster film of the same name catapulted the great white shark from near obscurity to one of the most recognisable creatures on Earth. The great white Shark is the world’s largest predatory fish and has been an apex predator in the world’s oceans for around 16 million years. Great whites can grow in excess of six metres long and can reach a maximum weight of around three tonnes.
But as a recent study shows, it's not just the shark’s size which is huge. The genome of the great white is estimated to be 4.63 billion "base pairs" (base pairs being the rungs of the DNA ladder). By comparison, the human genome is 3.2 billion base pairs. Experts believe it is critical to gain further understanding of the great white’s genome and the fish’s genomic stability. It could shed light on age-related disease resistance and therefore could lead to new life-preserving medical treatments.
LiveScience report on the findings of the new study mapping the genome of the great white shark
There are around 25,000 genes in the great white shark genome, which is around 5,000-6,000 genes more than humans have. Furthermore, hosts of genetic mutations have been uncovered linked to blood clotting and wound recovery. This could explain why sharks are able to recover from the kind of serious injuries which would probably prove fatal for many other animals.
Additionally, this study decoded many genes that could play a role in the shark’s resistance to cancer and other age-related diseases. A popular widely-believed myth is the misconception that sharks cannot get cancer which stems from how sharks get cancer at much lower rates than most other animals.
The great white genome showed the highest concentration of transposons, or "jumping genes", discovered so far in any vertebrate. Study co-author Dr Michael Stanhope explains that the transposons are associated with genome instability, but the abundance of these genes could have resulted in enrichment of genome stability genes. When the whale shark’s (Rhincodon typus) genome was decoded, similar genes and mutations were found, which are key to the shark’s genome stability.
Theoretically, the longer an organism lives and the bigger body size it has, the higher the risk of developing cancer the organism has. However, larger animals do not get cancer at increased rates when compared to humans, indicating that larger animals have superior resistance against cancer. The fine-tuning of larger shark’s genomes could be an adaption to facilitate the evolution of their large size and increased longevity.
Furthermore, a natural compound produced by sharks called "squalamine" could play a role in their cancer resistance. Squalamine aids the immune system of the shark as it possesses anit-viral properties, and may be linked to preventing degradation of molecular code (DNA). It is also thought to prevent the onset of age-related illnesses in sharks.
Sharks also have very stable DNA, much more stable than our own, and the new study has highlighted this. "We find that nature has developed clever strategies to maintain the stability of genomes in these large-bodied, long-lived sharks", explains study co-author Dr Mahmood Shivji
From RTÉ Radio 1's Mooney Goes Wild, marine biologist Li Ling Hamady on why sharks live so long
When compared to sharks, the human genome has a much higher rate of instability due to accumulated DNA damage which increases the likelihood of cancer and other age-related diseases. Sharks have a distinct advantage as they have regions of DNA that help repair and control DNA damage. This leads to resistance against age-related disease and results in higher longevity.
"There’s still tons to be learned from these evolutionary marvels", says Dr Shivji, "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."
The importance of sharks in the oceans cannot be understated. They control the food chain and are a fundamental part of the ecosystem. Shark studies have even played a role in understanding climate change. Now, sharks could even reveal answers to tackle diseases causing pain and suffering to millions. Studies like this will hopefully help improve public image of sharks and help bring awareness to just how vital it is to preserve these animals.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ