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Decoding Longevity: Genetic Secrets of the Greenland Shark
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Scientists explore the genome of the world’s longest-living vertebrate to unlock insights into aging and cancer prevention.
The Enigmatic Greenland Shark: A Century-long Childhood
While human puberty typically begins in the teenage years, the Greenland shark experiences a remarkably extended adolescence, reaching maturity at around 100 years old. This extended juvenile phase is just one facet of thier exceptional lifespan, which can reach approximately 400 years, making them the longest-living vertebrates on Earth [[1]], [[3]].
Recent investigations into the Greenland shark’s genetic makeup have identified several factors potentially contributing to their exceptional longevity. These discoveries may hold clues to understanding how we, too, can promote healthier and longer lives.
Unlocking the Genetic Code: The Greenland Shark Genome Project
In 2021, Arne Sahm, a bioinformatician, initiated a project to decipher the genetic underpinnings of the Greenland shark’s extended lifespan.The goal extended beyond simply understanding the shark; Sahm aimed to identify potential parallels with other long-lived species, such as the naked mole rat, in the hope of uncovering worldwide mechanisms of longevity.
It is useful to investigate whether there are common evolutionary tricks that ensure that long-lived species live even longer.
Arne Sahm, Leibniz Institute for Gerontology – Fritz Lipmann Institute
Obtaining a complete genome required fresh samples from these elusive creatures, a considerable challenge given their size and deep-sea habitat. Greenland sharks inhabit the cold waters of the North Atlantic and Arctic Oceans [[2]], frequently enough diving to depths exceeding two kilometers.
The Grueling Task of Sample Collection
John Steffensen,a marine biologist with two decades of experience studying Greenland sharks,described the process of capturing these animals for research. “You confirm ten hooks on a long line,” steffensen explains,emphasizing the scale of the operation. “They hooks are huge – we call them shark hooks.”
The hooks are baited with “brugs,” a term for pungent,rotting meat. These baited hooks are then lowered into the depths using a combination of lifting straps and chains, often attracting one or more sharks. For Sahm’s research, sharks were caught in the southern fjords of Greenland, and brain tissue samples were sent for genomic analysis. The findings of this research were published in September 2024.
Jumping Genes and DNA Repair: Genomic Insights
Imagine the genome as a complete instruction manual, with DNA as the words and genes as the paragraphs. Sahm’s team successfully mapped the entire genome of the Greenland shark, revealing a “book” containing 22,634 genes and approximately 6.45 billion base pairs – roughly twice the size of the human genome.
Analysis of the genome revealed a high number of “jumping genes,” also known as transposons. These genes have the ability to duplicate themselves and insert into new locations within the genetic sequence.
Sahm illustrates this process by comparing it to copying and pasting a section of text into the middle of a sentence, potentially disrupting its meaning. While most organisms possess jumping genes, the Greenland shark appears to utilize them in a especially beneficial way. In these sharks, duplications frequently occur in genes associated with DNA repair. Instead of creating “nonsense,” these duplications may provide extra copies of useful genes, potentially slowing down the aging process.
DNA damage can lead to cellular dysfunction, including cancer. The prevailing theory suggests that the more effectively a genome is maintained, the longer an organism can live.
TP53: the Genome’s Guardian Against Cancer
Another gene of interest is TP53, frequently enough referred to as the “guardian of the genome.” This gene plays a crucial role in cancer prevention and is found in many animals, including humans, elephants, and whales. TP53 encodes the P53 protein, which suppresses tumor formation and facilitates DNA repair.
The P53 protein ensures that cells with damaged DNA either die or cease dividing until the damage is repaired, preventing uncontrolled cell growth and tumor development.
Intriguingly, the TP53 gene functions differently in Greenland sharks compared to other animals. Researchers hypothesize that this unique functionality may contribute to the shark’s remarkable longevity.Though,Sahm emphasizes the need for further research to fully understand these operational differences.
