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Biology

How Jaws Could Cure Cancer: The White Shark Genome and Its Influence on Human Health

When you hear the words “great white shark” what thoughts come to mind?  Awe, reverence, maybe even fear? I’m sure you don’t think of how great white sharks can impact the future of human medicine. However, a new study by the Save Our Seas Shark Research Center recently found links between great white sharks and humans that could have tremendous impacts on the way we view cancer, disease, and wound healing.

Carcharodon carcharias, the Great White Shark. Image taken in Isla Guadalupe in Mexico.

Collaborators from multiple universities worked together to sequence the first ever great white shark genome. What exactly does this mean? First, let’s take a step back and recall  the basics of DNA.

All living things have DNA, made up of a unique sequence of four bases (A, T, C, and G). Similar to how 26 letters can make millions of words, four bases can make millions of unique sequences.  These unique sequences are translated into RNA, which then codes for a protein, sort of like RNA is the recipe that must be followed to make the protein (for more information on how this works, watch this video). This protein can have a multitude of different functions, from tissue repair to brain function.  It’s safe to assume that if your body does something, there is a gene (or thousands of genes!) that encodes for that function. This isn’t just true for humans – all living things have genes that control their form and function.

A genome is a collection of all of the DNA in an individual. Genomes contain massive quantities of DNA; the human genome contains 3 billion pairs of bases! As you can imagine, sequencing a whole genome is no easy task. Up until this study, only two shark genomes had been published: the elephant shark genome and the whale shark genome (two more shark genomes have since been published, but were not included in this study).

After sequencing the great white shark’s genome, scientists were able to identify the genes that great white sharks have, and they made some exciting discoveries. Great white sharks were found to have genetic adaptations for wound healing and genome stability, which could explain why the sharks rarely get cancer or diseases, and why their wounds heal quickly and efficiently.

How did they do it?

First, DNA was collected from three white shark individuals. The first sample was collected from the heart tissue of a shark used in previous and studies. The second was a blood sample collected from a shark that was captured and released in Southern California. The third was a tissue sample from a free-swimming shark (meaning the shark was never captured).

            DNA was isolated from the samples and sequenced on a special machine that uses fluorescence, or light emissions, to read each base in the DNA sequence. The sequence was read in small chunks, and the whole genome was assembled by looking for overlapping areas in the small chunks and fitting them together like pieces of a puzzle.

After the genome was assembled, the next step was to determine which genes were present. To do this, researchers compared the white shark genome to the two other shark genomes (elephant shark and whale shark) as well as other vertebrate animals. While each individual has a unique genome, there are many parts of the genome that remain the same even across vastly different species. Therefore, researchers were able to use genomes that had already been published as a map to identify which genes were present in great white sharks.

Next, researchers ran tests to determine which genes were being positively selected for. Positive selection means that the gene codes for a trait that is important in the animal, and therefore the trait is selected to stick around. Scientists can tell which traits are being selected for, because the sequence of bases that make up the gene remain constant across individuals at rates that are not due to random chance. By identifying genes under selection, the researchers were able to identify which traits were important in sharks, and the results were very exciting!

 

What did they find?  

After sequencing and aligning the genome, the researchers were able to identify 24,520 genes. Of all the genomes they compared, they found that the white shark had the most genes under positive selection. Of these genes, a majority were involved in important functions that help maintain genome stability, such as DNA repair and damage response. DNA instability is a leading factor in human aging, because it leads to cancer, cell death, and loss of cellular function.

In addition to DNA response, genes involved in blood clotting were also found to be under positive selection, indicating that great white sharks might have superior wound healing abilities compared to the other genomes studied.

Why does it matter?

Sharks are one of the oldest animals on earth, evolving over 400 million years ago. Since we first began to study these mysterious creatures, humans have been perplexed by their health and longevity. For the first time, scientists have identified the genes that prevent sharks from ailments all too common in humans, such as cancer and other age-related conditions. Perhaps someday, we will be able to manipulate our own genes to reflect that of the great white shark. While we still have a long way to go, this study brings us one step closer to discovering a cure to some of humankind’s greatest nemeses: cancer and disease.

Not only is this study good news for humans; it’s good news for great white sharks, too! Great white sharks are some of the most misunderstood creatures on the planet, and their numbers have declined rapidly due to over fishing, shark finning, and other human impacts. Hopefully, this study will help people understand that sharks have a lot to offer us, so we should probably keep them around!

Reference Paper:

White shark genome reveals ancient elasmobranch adaptations associated with wound healing and the maintenance of genome stability

Nicholas J. MarraMichael J. StanhopeNathaniel K. JueMinghui WangQiSunPaulina Pavinski BitarVincent P. RichardsAleksey KomissarovMikeRaykoSergey KliverBryce J. StanhopeChuck WinklerStephen J. O’BrienAgostinho AntunesSalvador JorgensenMahmood S. Shivji

Discussion

One Response to “How Jaws Could Cure Cancer: The White Shark Genome and Its Influence on Human Health”

  1. Well written – good explanation the complicated aspects of genetic-based science

    Posted by Ray | March 9, 2019, 1:54 pm

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