Great white shark genome decoded
In a major step toward understand the biology of the great white shark, its entire genome has now been decoded in detail.
The iconic predator – whose ancestry dates back more than 400 million years – is famous not just for its massive size (up to 20 feet or 6.1 meters) and fierceness, but also for its wound-healing abilities, long lifespan (70-odd years), and low rates of cancer.
The new study, published February 19, 2019, in the peer-reviewed journal Proceedings of the National Academy of Sciences, compared the great white’s genome to genomes from a variety of other vertebrates, including the giant whale shark and humans. It turns out that the great white’s genome is massive – they have 41 pairs of chromosomes compared to our 23 — and the researchers say that decoding their genome could help reveal the genetic changes behind the shark’s evolutionary success.
The researchers say this information could help with the conservation of great whites and other sharks – many of which have rapidly declining populations due to overfishing – and humans as well. Salvador Jorgensen, a senior research scientist at the Monterey Bay Aquarium, is a study co-author. He said in a statement:
Decoding the white shark genome is providing science with a new set of keys to unlock lingering mysteries about these feared and misunderstood predators – why sharks have thrived for some 500 million years, longer than almost any vertebrate on earth.
… striking occurrences of specific DNA sequence changes indicating molecular adaptation (also known as positive selection) in numerous genes with important roles in maintaining genome stability - the genetic defense mechanisms that counteract the accumulation of damage to a species’ DNA, thereby preserving the integrity of the genome.
These adaptive sequence changes were found in genes intimately tied to DNA repair, DNA damage response, and DNA damage tolerance, among other genes. The opposite phenomenon, genome instability, which results from accumulated DNA damage, is well known to predispose humans to numerous cancers and age-related diseases.
The new genome map reveals that not only do great white sharks have chunks of code for these genome-stabilizing DNA repair mechanisms, but they also have gene adaptations for for tumor suppression. Michael Stanhope, of Cornell University College of Veterinary Medicine, is a study co-author. Stanhope told Wired:
Understanding how these genes might be inoculating these animals from cancer could be a huge benefit to humans.
The shark genomes also revealed intriguing evolutionary adaptations in genes linked to wound healing pathways. Sharks are known for their impressively rapid wound healing. Stanhope said:
We found positive selection and gene content enrichments involving several genes tied to some of the most fundamental pathways in wound healing, including in a key blood clotting gene. These adaptations involving wound healing genes may underlie the vaunted ability of sharks to heal efficiently from even large wounds.
The researchers say they have just explored the “tip of the iceberg” with respect to the white shark genome. Mahmood Shivji is a study co-author and director of Nova Southeastern University’s Save Our Seas Foundation Shark Research Center. Shivji said:
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. 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.
Bottom line: Researchers have mapped the genome of the great white shark.