In the dark, freezing depths of the Arctic Ocean, in waters near freezing temperatures, a slow-swimming creature glides that has witnessed the world change over centuries. The Greenland shark (Somniosus microcephalus) is the longest-living vertebrate known on Earth. Estimates based on carbon dating of the eye lens indicate a lifespan of 250 to 400 years, meaning a shark swimming today in the ocean may have been born before the Industrial Revolution.
For decades, the question remained open: How does a creature live so long and almost never get cancer? Now, the missing piece of the puzzle has arrived. An international team led by the University of Tokyo has deciphered the Greenland shark genome, published the findings in the prestigious scientific journal PNAS, and revealed for the first time the genetic clues behind its extreme longevity.
What is the Greenland shark and why is it so special?
The Greenland shark is no ordinary shark. It lives slowly, grows slowly, and holds records that are hard to grasp:
- Lifespan of 250-400 years, the longest-living vertebrate known to science.
- Sexual maturity around age 150, an age at which most mammals are long gone.
- Growth of only about one centimeter per year, an extremely slow growth rate.
- Lives in deep cold, at depths of up to 2.6 kilometers, in near-freezing temperatures.
- Almost never develops cancerous tumors, despite its large body and centuries of cell division.
This combination makes it an ideal model for aging research. When a creature holds trillions of cells and divides them over centuries, each division is an opportunity for mutation and cancer. Yet, the Greenland shark manages to avoid this, and that is precisely what attracts scientists' attention.
The Greenland shark genome: What exactly was deciphered
The team, led by researcher Shigeharu Kinoshita from the University of Tokyo and in a paper authored by Kaixiao Yang and colleagues, assembled the genome at the chromosome level. Here are the key numbers:
- Genome size: about 5.9 billion base pairs, nearly twice the size of the human genome (about 3.1 billion).
- Assembly completeness of 96.7 percent, meaning almost the entire genome is mapped and ordered.
- This is the first complete genome ever assembled for this species.
It is important to understand what deciphering a complete genome means. A genome is the full biological instruction book of a creature. When 96.7 percent of it is deciphered at a high level, it can be compared to the genomes of other sharks and other vertebrates, identifying which genes have been expanded, modified, or strengthened specifically in the Greenland shark. These differences are the clues to longevity.
The genetic clues: DNA repair, cancer resistance, and oxidative protection
Here begins the truly interesting part. The genetic analysis identified several mechanisms that align well with what we know about the biology of longevity. The three main ones are DNA repair, cancer resistance, and protection against oxidative damage.
1. Expansion in DNA repair gene families
One of the prominent findings is an expansion in gene families related to DNA repair. Aging largely results from the accumulation of DNA damage over time. Every day, the DNA in our cells absorbs thousands of hits from radiation, oxidation, and copying errors. The more efficient the repair system, the slower the damage accumulation, and with it, aging. A shark that maintains an enhanced repair system for 400 years is living proof of this principle.
2. Genes for cancer resistance
The analysis also identified an expansion in gene families related to cancer resistance and immune system function, including genes in the NF-kB signaling pathway, a central pathway regulating inflammation, immunity, and cell survival. Cancer resistance is a central topic in longevity research, and not by chance. The larger and longer a creature lives, the greater the risk that a single cell will accumulate enough mutations and become cancerous. Long-lived creatures like the bowhead whale and the Greenland shark have developed genetic defenses against this scenario.
3. Protection against oxidative damage: The FTH1b gene
A specific and fascinating finding is the dramatic expansion of the FTH1b gene, a gene related to iron storage within the cell. While other sharks carry a low number of copies of this gene, the Greenland shark was found to have about 59 copies of FTH1b. Why is this important?
- Free iron inside the cell is dangerous: it accelerates the production of free radicals that cause oxidative damage.
- Efficient iron storage reduces the amount of free iron, thereby protecting the cell from damage.
- The gene is also involved in regulating ferroptosis, a type of iron-dependent cell death linked to aging and diseases.
In other words, the Greenland shark has developed a highly sophisticated system to neutralize one of the main causes of cellular wear and tear over time.
4. Changes in the histone protein H1.0
Additionally, amino acid substitutions were found in the histone protein H1.0. Histones are the proteins around which DNA is wrapped for organization and protection. A change in histone H1.0 may affect chromatin stability, meaning how well the DNA is kept organized and protected. Chromatin stability is one of the hallmarks of aging, and the Greenland shark may have found a way to preserve it over centuries.
How does this fit into the big picture of aging?
The amazing thing about the findings is that they are not surprising. Every mechanism identified in the Greenland shark aligns with the list of hallmarks of aging that scientists have mapped over the past decade: genomic instability, epigenetic changes, loss of chromatin stability, and accumulated oxidative damage.
The Greenland shark is essentially a living evolutionary proof: nature, through millions of years of natural selection, has arrived at the same solutions that longevity scientists are trying to replicate in the lab. It has strengthened DNA repair, improved oxidative protection, and fortified cancer resistance. This is why studies on long-lived animals, from bats to naked mole rats, are a goldmine for aging research.
What can humans learn from this?
This is the question everyone asks, and caution is needed here. The Greenland shark genome is a compass, not a recipe. You cannot simply take its genes and paste them into humans. However, it points to valuable research directions:
- DNA repair as a therapeutic target: If we understand exactly which genes are amplified in the shark, we can look for ways to strengthen parallel pathways in humans.
- Iron management and oxidative damage: The FTH1b mechanism reinforces the importance of iron balance in the body, a topic already relevant to health and aging.
- Cancer resistance: Understanding the NF-kB pathway in the shark may contribute to future cancer prevention research.
Does this mean we will live 400 years?
No. And it is important to say this clearly. Deciphering a genome is a starting point, not a finish line. Between identifying an interesting gene in a shark and a safe, effective treatment for humans lies a long road of years, sometimes decades, of research. Here are the limitations to keep in mind:
- Genes operate within a complete system: A single gene in the shark works in the context of its entire unique biology, including the cold and slow metabolism. You cannot isolate one gene and expect the same result.
- Completely different metabolism: The Greenland shark lives in deep cold and at an extremely slow pace of life. Part of its longevity simply stems from this, and it is not something humans can or want to replicate.
- This is basic research: The goal of the paper was to map the genome and identify candidates, not to propose a treatment. It is a foundation for evolutionary research and future studies.
- There is no magic supplement here: If you encounter a product promising you the genes of the Greenland shark, it is marketing, not science.
What can we take from the research?
Even without future genetic therapy, there is a practical message here. The mechanisms that the Greenland shark naturally strengthens are exactly those we can support through lifestyle:
- Protection against oxidative damage: A diet rich in natural antioxidants from food (fruits, vegetables, legumes) supports cellular protection, the same principle that FTH1b expresses to an extreme.
- Maintaining iron balance: Excess iron is linked to oxidative damage. If you do not suffer from a diagnosed deficiency, there is no need to overload with iron supplements. Periodic blood tests are better than guessing.
- Supporting DNA repair: Quality sleep, avoiding smoking and excessive sun exposure, and physical activity all reduce the daily burden of DNA damage on the body.
- Preventing chronic inflammation: The NF-kB pathway identified in the shark is also linked to inflammation. Reducing chronic inflammation through diet and activity is one of the best investments in healthy longevity.
The broader perspective
The Greenland shark genome joins a series of exciting discoveries about long-lived animals: the bowhead whale, which lives over 200 years and almost never gets cancer; the naked mole rat, which is exceptionally resistant to tumors; and now the ancient shark of the Arctic. Each tells the same story from a different angle: aging is not a fixed biological decree, but a process that nature has learned to delay in various ways.
We will not become Greenland sharks. But the better we understand how nature solved the problem of aging in different creatures, the closer we get to understanding how we can add not just years to life, but life to years. The instruction book of the oldest creature on Earth is now open for reading, and this is only the beginning.
References:
PNAS - The Greenland shark genome: Insights into lifespan extremes
Live Science - First whole-genome sequence of a Greenland shark
💬 Comments (0)
Be the first to comment on the article.