But looks aside, the species has a surprising capacity: It can live for as long as about 400 years. Now, an international team of scientists from Europe and the United States has mapped the genome of the Greenland shark, offering scientists an opportunity to glean the secret to the shark’s outstanding longevity.
“Any research into the mechanisms of how this animal is able to live for such a long time will at some point need the genome sequence,” said Steve Hoffmann, a computational biologist at the Leibniz Institute on Aging and the Friedrich Schiller University Jena, in Germany, who led the research.
The findings, published as a preprint in bioRxiv, provide a comprehensive assembly of the shark’s genetic makeup. It also provides initial insights into the specific genes and biological mechanisms, including a network of duplicated genes involved in DNA repair, that may be responsible for the shark’s exceptional life span.
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A key finding identified a network of 81 genes that were found only in Greenland sharks and that played a role in DNA repair.
The researchers hypothesized that regular DNA repair genes had evolved to exploit the machinery of jumping genes in order to copy and paste more of themselves. That process may have helped them to both counteract the accumulated damage caused by jumping genes and improve the shark’s DNA repair abilities.
At the center of this network was a well-known gene, called TP53, that has been implicated in DNA repair and tumor suppression*.* A study published in 2016 showed that elephants carried 20 copies of this gene, and scientists believe that the gene may account for the animal’s strong resistance to cancer.
The Greenland shark (Somniosus microcephalus ) is the longest-lived vertebrate known, with an estimated lifespan of ∼ 400 years. Here, we present a chromosome-level assembly of the 6.45 Gb Greenland shark, rendering it one of the largest non-tetrapod genomes sequenced so far. Expansion of the genome is mostly accounted for by a substantial expansion of transposable elements. Using public shark genomes as a comparison, we found that genes specifically duplicated in the Greenland shark form a functionally connected network enriched for DNA repair function. Furthermore, we identified a unique insertion in the conserved C-terminal region of the key tumor suppressor p53. We also provide a public browser to explore its genome.
Genes that code for proteins in DNA repair, such as the p53 gene or the Greenland shark gene, need to be modified, such as adding or removing some DNA bases, which can be done very easily with the crispr cas9 gene cutting and adding technique.
Eyes and hearts of these deep-dwelling sharks use biological tricks to keep functioning
Scientists estimate that Greenland sharks (Somniosus microcephalus) may survive for upward of four hundred years. “They’re these huge, ancient grandpa sharks,” Fogg says. But it’s unclear how exactly their bodies keep on cruising decade after decade.
Fogg’s team studied the animals’ eyeballs. No one knew if the sharks had much vision, let alone if that vision degraded over time. The common thinking was that the sharks were either severely visually impaired or completely blind, Fogg says. She and her colleagues examined eye tissue from 10 Greenland sharks, some up to about 150 years old. The animals had all the cellular and molecular tools in place for seeing in the deep sea’s dim light, the team reported January 5 in Nature Communications.
The tissue also looked like it had avoided the typical wear and tear of aging. That may be due to dialed-up activity of DNA repair machinery in the eyes, Fogg says. This machinery fixes damage that can lead to cell death and tissue degeneration. An earlier investigation of the Greenland shark’s genome also pointed to enhanced DNA repair function, reported physiologist Alessandro Cellerino and his colleagues.
The antiaging strategy at work in the eyeballs may not occur in all the Greenland shark’s organs, however. Researchers studying the animal’s heart found that it appears to collect the typical scars and stresses that time tattoos on our tissues, scientists reported December 23 on bioRxiv.org. “We were expecting the opposite,” says Cellerino, of the Scuola Normale Superiore in Pisa, Italy.
