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A new genomic study of Greenland sharks has revealed how they have one of the longest lifespans among animals, spanning centuries, without developing any tumors.
The yet-to-be peer-reviewed findings may help find new treatments for cancer and therapies to boost lifespan in humans, scientists say.
Previous research has shown that the Greenland shark, which lives in the deep waters of the North Atlantic and Arctic Oceans, has a lifespan extending to nearly 400 years.
It is the largest extant shark species, reaching lengths greater than 6m (20ft), and weighing up to 1,400kg (3000lb).
Despite its extreme size, longevity, and slow metabolism, comprehensive genomic studies on the shark have been rare due to the large size of its genome.
One of the reasons for cancer is the accumulation of damage to DNA over an organism’s lifetime.
Long-lived animals face a higher cancer risk since they have more cells, and hence more chances for cell divisions to go wrong.
However, the cancer incidence of such long-living animals like elephants and Greenland sharks is not high as expected in what’s called Peto’s paradox.
In the latest study, an international team of scientists mapped the Greenland shark’s complex genome, revealing some clues to this paradox.
Scientists found that the Greenland shark has enhanced DNA damage response and repair mechanisms.
They looked specifically at a class of genes within the shark’s genome involved in the regulation of a key immune system protein.
These gene families, researchers say, are involved in the activation of the protein NF-kB that regulates inflammation, immunity, and cell survival – key mechanisms involved in suppressing tumours.
Scientists found that the Greenland shark had more copies of these genes compared to other short-lived shark species, keeping their genome more stable against damage.
They found that it has “robust immune defence” that potentially reduces their risk of infectious diseases and autoimmune issues.
Within the deep-sea shark’s genome, researchers also found clues to its successful adaptation to a slow life in the depths of the ocean.
The eye protein rhodopsin of the Greenland shark was found to have amino acid variations that made them more adept at processing blue-light wavelengths – a feature that is advantageous when living in the dim deep ocean waters.
“These genomic analyses offer new insights into the molecular basis of the exceptional longevity of the Greenland shark and highlight potential genetic mechanisms that could inform future research into longevity,” scientists wrote in the study.
Source: independent.co.uk
