The Greenland shark has the recipe for longevity, living to be over 400 yrs old
14. 07. 2023
Born in the time of William Shakespeare and still swimming in the depths of the cold ocean. The Greenland shark or grey shark (Somniosus microcephalus) is a unique creature, living to be over an incredible 400 years old. What's its secret? What's hidden in its genetic information? Let's take a closer look – on Shark Awareness Day, which falls on 14 July.
It is not often that a team of Czech molecular biologists and bioinformaticians finds itself attempting to capture a shark. In fact, it paints a rather strange picture. Nevertheless, it is the real story of last year’s fortnight-long expedition off the Icelandic island of Heimaey. The aim was to obtain at least a small DNA sample of the Greenland (or grey) shark, as its genetic information holds the secret to the animal’s longest known lifespan of all vertebrates.
“We’re more lab rats that don’t normally get to be in the field like this. For me personally, the expedition to Iceland was the first experience of this kind,” recalls Václav Brázda from the Institute of Biophysics of the CAS after more than half a year. He is not a zoologist that researches ocean animals; the Greenland shark won him over purely because of its singular genetic make-up.
The scientist’s long-standing research focus is the p53 protein, nicknamed “the guardian of the genome”. It functions within the cell as a sensor of DNA damage and regulates the process of gene expression that can control cell growth and ageing. It was expected then that it would be the form of this protein that would distinguish the Greenland shark from other animals.
Not exactly clear sailing
The genetic sequence database, which is updated by researchers from all over the world, contains information about the DNA of many organisms. But so far, data on the Greenland shark has been missing from it. The only way to find out more about it was to obtain a sample for analysis at the location where it can be found. The Neuron Fund supported the daring expedition to Icelandic waters.
In August 2022, a team of five researchers from the Czech cities of Brno and Ostrava set off on their “shark hunt”. Václav Brázda became the nominal captain of the ship and expedition coordinator. Martin Bartas from the University of Ostrava was in charge of bioinformatic data analysis and his colleagues from the same institution, Adriana Volná and Jiří Červeň, were in charge of nucleic acid isolation. The team was joined by Michaela Dobrovolná from the Brno University of Technology, who kept the expedition records and organised the activities.
Everything turned out a little differently than the team initially planned, and the end of the expedition also took a different turn. “The first night after we arrived, a magnitude five earthquake occurred. I woke up and there was a crack in the wall. Three days later, a volcano erupted. It complicated our schedule quite a bit and we didn’t get to spend as much time on the ship as we needed to,” Václav Brázda recalls.
Václav Brázda on the expedition boat, dangling shark bait.
Homeward bound without a shark of their own
The meat of the Greenland shark is toxic and can only be eaten after being treated for weeks or months. It therefore hasn’t been fished in Iceland for several decades. The first steps of the Czech expedition team therefore led to the small fishing village of Bjarnarhöfn, where there is a museum devoted to Greenland shark fishing. They were shown around by a man whose grandfather is said to have been the last active hunter of this gigantic cold-water species.
Provided with some valuable advice, then, the researchers set off for the island of Heimaey which, incidentally, is also the largest breeding ground of the Atlantic puffin. At the local harbour they received basic boat-handling training and prepared bait, hooks, and nets before setting sail. Apparently, they were the first boat in 100 years to go out on the ocean with the express intention of finding and capturing a Greenland shark! The advantage of a freshly caught animal is the quality of the sample from which DNA and RNA can be isolated. Unfortunately, despite repeated attempts, the goal of the expedition failed, as they were unsuccessful in luring the shark.
Still, the researchers didn’t come away from this completely empty-handed. “Fortunately for us, some Greenland sharks occasionally get caught in the big fishing nets of the fishing companies, so we managed to obtain at least some samples suitable for nucleic acid analysis – in this roundabout way,” Brázda remarks. In addition, they have established cooperation with local researchers, who have promised to let them know as soon as a shark will be caught in the fishing nets again.
A jumbo old-timer
The Greenland shark (Somniosus microcephalus) is no munchkin. It can grow to over six metres in length and weigh around one tonne. It lives in the deep, cold waters of the ocean, which is perhaps why the shark has been a rather neglected subject of research. Which is surprising, given its unique traits. Based on the data collected so far, it’s probably the longest-living vertebrate on the planet.
A major study on the Greenland shark was published in Science in 2016. Using the method of radiocarbon dating, they were able to pinpoint its maximum possible age. Analysis of eye lens samples from 28 female specimens revealed that they reach sexual maturity at approximately 150 years of age, and the age range of the animals examined was more than 270 years. The largest female specimen, which measured over five metres long, was estimated by the researchers to be between 272 to 512 years old.
In addition to their exceptional lifespan, another striking fact is their excellent condition – they are able to avoid almost all types of neurodegenerative and cancer diseases. “With a bit of hyperbole, we can say that unlike humans, the Greenland shark does not need any hospitals or nursing care to take care of individuals with advanced age in order to live longer. They are still active, despite being hundreds of years old,” Brázda says.
Greenland sharks stand out not only in the world of vertebrates in general, but also in their own group of relatives. Most other shark species have a ten times shorter lifespan and different lifestyle. We usually think of sharks as vicious, dangerous predators, but the Greenland shark does not pursue its prey. Instead, it leisurely waits for carrion to cross its path, and it may seldom attack sleeping pinnipeds (seals). Why bother with sudden movements, when easy does it?
A jigsaw puzzle with a billion pieces
Václav Brázda and his colleagues from the Faculty of Science at the University of Ostrava had previously discovered specific sequences of the p53 protein in long-living organisms. They were therefore very curious to find similar anomalies, or even additional ones, in the Greenland shark.
They had a small field lab set up in Iceland, where they processed a piece of donated shark muscle tissue and isolated a piece of DNA suitable for later sequencing. The main part of the work, though, was to come after arriving in the Czech Republic. “We managed to sequence all the DNA in several months, but this is hundreds of billions of letters of genetic information. We try to arrange the pieces in a way that makes sense. It’s similar to assembling a jigsaw puzzle, but in this case, you’re missing the picture template,” Brázda explains.
However, the first partial results are already available and they involve, for instance, the aforementioned p53 protein – the guardian of the genome, which is linked to the ageing of organisms. When comparing p53 in the Greenland shark and other organisms, it turned out that they differ specifically in the area of the so-called L2 loop, by which the protein binds to DNA.
But there are additional proteins found in the bodies of animals that can influence the ageing process. “Curiously, the sequences of some of the proteins are very similar in both sharks and humans. Others are unexpectedly disparate to a large degree. This is evident, for instance, in one of the proteins responsible for ageing – the H2AX protein,” Brázda explains. The H2AX proteins of the shortfin mako shark and humans are relatively similar, while the Greenland shark differs from them both.
Since the genome of the Greenland shark has never been studied in such detail before, the work of Brázda’s team is yielding unique and innovative results. The researcher plans to write these up in the form of a scientific paper and have it published. At the same time, he intends to return to Iceland to try to obtain a fresh DNA sample of the Greenland shark. Together with colleagues from the Faculty of Science at the University of Ostrava, he is now preparing an application for a larger international project with this objective.
The results of the analysis of the “longevity proteins” are beneficial not only for solving the mystery of the Greenland shark’s extraordinary genome, but prospectively also for human medicine. It would be tempting to discover the “elixir of life” that guarantees an essentially flawless long lifespan.
Last summer, an earthquake struck in Iceland at the start of the Czech expedition. Will the results of the analysis of the shark samples the team took there also one day cause a small earthquake in the scientific community? Should the genetic riddle of the Greenland shark be deciphered and made use of in tens or hundreds of years, we will no longer be there to see it. However, the shark in question will.
Prof. Mgr. Brázda Václav, Ph.D.
He holds a degree in molecular biology and genetics from the Faculty of Science of Masaryk University in Brno. In 2005–2006 he completed a postdoctoral fellowship at the University Health Network at the Ontario Cancer Institute in Toronto, Canada. He teaches gene technology and bioinformatics at the Faculty of Chemistry, Brno University of Technology. His research interests include bioinformatics analyses of nucleic acids, the relationship between DNA structure and function, and p53 protein–DNA interactions. In his free time, he writes poetry and sings in the vocal group DNA – Dej Nám Akord.
The article was originally published (in Czech) in the 1/2023 issue of the CAS Magazine A / Věda a výzkum.
Author: Leona Matušková, Division of External Relations, CAO of the CAS
Translated by: Tereza Novická, Division of External Relations, CAO of the CAS
Photo: Shutterstock; Nadační fond Neuron; Jana Plavec, Division of External Relations, CAO of the CAS
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