The great white shark is one of the most recognized marine creatures on Earth, generating widespread public fascination and media attention, including spawning one of the most successful movies in Hollywood history. This shark possesses notable features, including its massive size (up to 20 feet and 7,000 pounds) and diving to nearly 4,000 feet deep. Great whites are also a big conservation concern given their relatively low numbers in the world's oceans.
In a major scientific step to understand the biology of this iconic apex predator and hawks in general, the whole genome of white hairs has now been decoded in detail.
A team led by scientists from the Nova Southeastern University (NSU), Save Our Seas Foundation, Shark Research Center and the Guy Harvey Research Institute (GHRI), Cornell University College of Veterinary Medicine, and the Monterey Bay Aquarium, completed the white Shark genome and compare it to genomes from a variety of other vertebrates, including the giant whale shark and humans.
The findings are reported in the 'Latest Articles' section of the journal Proceedings of the National Academy of Sciences .
Decoding the white shark's genome reveals not only its huge size ̵
The researchers found 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's DNA, thus preserving the integrity of the genome.
These adaptive sequence changes were found in genes closely related 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.
"Not only were there a surprisingly high number of genome stability genes that contained these adaptive changes , but there was also an enrichment of several of these genes, highlighting the importance of this genetic fine tuning in the white shark, "said Mahmoud Shivji, Ph.D., director of NSU's Save Our Seas Foundation Shark Research Center and GHRI. Shivji co-led the study with Michael Stanhope, Ph.D., of the Cornell University College of Veterinary Medicine.
It was also notable that the white shark genome contained a very high number of "jumping genes" or transposons, and in this case a specific type, known as LINEs. "These Lines are known to cause genome instability by creating double stranded breaks in DNA," said Stanhope. "It is believed that this proliferation of LINs in the white shark genome could represent a strong selective agent for the development of effective DNA repair mechanisms, and it is reflected in the positive selection and enrichment of so many genome stability genes."
The international The research team, which also included scientists from California State University, Monterey Bay, Clemson University, University of Porto, Portugal, and the Theodosius Dobzhansky Center for Genome Bioinformatics, Russia, also found that many of the same genome stability genes in the white shark were
The discovery that the whale shark also had these key genome stability adjustments was significant because theoretically, the risk of developing a cancer should increase with both the number of cells (large bodies) and an organism's lifespan – there is statistic support for a positive relationship of body size and cancer risk within a species. Interestingly, this does not tend to hold across species.
Contrary to expectations, very large-bodied animals do not get cancer more often than humans, suggesting that they have developed superior superiority to cancer-protective abilities. The genetic innovations discovered in the genome of the stability genes in the white and whale shark could be adaptations facilitating the evolution of their large bodies and long lifespans
"Decoding the white shark genome is providing a science with a new set of keys to unlock the lingering mysteries about these feared and misunderstood predators – why the sharks have thrived for some 500 million years, longer than almost any vertebrate on earth "said Dr. Salvador Jorgensen, a Senior Research Scientist at the Monterey Bay Aquarium, who co-authored the study.
But the innovations did not end there.
The shark genomes revealed other intriguing evolutionary adaptations in genes linked to wound healing pathways. "We found a positive selection and enrichment of the gene content, involving several genes associated with some of the most fundamental pathways in the wound healing, including in key blood clotting genes," said Stanhope. "These adaptations involving wound healing genes may underlie the vaunted ability of sharks to heal effectively from even large wounds."
The researchers say they have just explored the "tip of the iceberg" with respect to the white shark genome. [19659003"Genomeinstabilityisaveryimportantissueinmanyserioushumandiseases;nowwefindthatnaturehasdevelopedcleverstrategiestomaintainthestabilityofgenomesintheselarge-bodiedlong-livedhawks"saidShivji"Therearestilltonstobelearnedfromtheseevolutionarymarvelsincludinginformationthatcanpotentiallybeusefulincombatingcancerandage-relatedillnessesandimprovethetreatmentofthewoundhealinginhumansaswerevealhowtheseanimalsdoit"
Decoding The white shark genome will also assist in the conservation of this and related aurors, many of which have a rapidly declining population due to overfishing, "said Steven O'Brien, conservation conservative geneticist at NSU, who co-developed this study." The genome The data will be a great asset for understanding the white shark population dynamics to better preserve this amazing species that has captured the imagination of so many. "
This research was funded by NSU Save Our Seas Foundation, the Guy Harvey Ocean Foundation, Hai Stiftung / Shark Foundation, the Monterey Bay Aquarium, and in-kind support from Illumina, Inc., and Dovetail Genomics.