Featured Image Credit: Miramax Films
By Alice Morris
It’s all in the genes!
A new study published January 30th in the journal BMC Genomics provides the first evidence that sharks and rays possess unique immune abilities that give them a leg (ahem, fin) up in the animal kingdom. Researchers believe that certain genetic modifications, a result of hundreds of millions of years of evolutionary natural selection, could explain why shark wounds heal so quickly and why cancer is so uncommon amongst chondrichthyans.
The study, led by Michael Stanhope and Mahmood Shivji, identified two genes in particular that are associated with high cancer resistance in sharks and rays.
These genes, called the legumain and Bagl genes, also have counterparts in the human genome, so researchers hope that their findings may be applied to human medicine.
“The immune system of sharks and rays has been battle-tested and evolved over hundreds of millions of years,” said Shivji. “Using genomics approaches to understanding their immunity genesis is likely to produce many more existing discoveries, some of which could potentially translate into human medical benefit.”
The human Bagl gene codes for a protein involved in programmed cell death or apoptosis. When over-expressed, these genes prevent the body’s normal elimination of dysfunctional cells, an inhibition that can cause cancer.
Adaptations within the shark’s Bagl gene may reveal why it functions so differently in humans and in sharks.
The study also identified characteristics in the shark DNA sequence that could explain why open wounds heal so quickly, despite the high levels of bacteria present in seawater. Compared with bony fishes, the four species of sharks and rays involved in the study had a higher proportion of certain genes related to antibody-mediated immunity. This means that within hours of receiving an injury, sharks and rays begin producing new cells that grow over the wound at a faster rate than what mammals are capable of.
“This higher proportion of genes involved in adaptive [antibody] immunity function could be a key reason behind the infection-fighting and fast wound-healing abilities of sharks and rays,” says Stanhope. “Previous studies of the shark immune system have already yielded some surprise in terms of antibody structure, and these new genetic findings further add to the box of biological novelties in this highly successful vertebrate lineage.”
Shivji stresses that despite their remarkable immune properties, eating shark will not cure or prevent cancer and it can actually have damaging effects on the body due to high levels of mercury.
“Several studies have demonstrated anti-tumor properties of shark-derived compounds in lab studies,” said Shivji. “It’s intriguing that we are now seeing evidence of evolutionary adaptation in these specific shark immunity genes, which just happen also to be involved in promoting cancer in humans.”
Further research is needed to better understand how these findings can be applied to human medicine, but Shivji says that this research demonstrates the importance of shark conservation.
“Now we have another important reason to make sure we don’t lose these marvelous and ecologically critical animals to overfishing, as is currently occurring in many parts of the world. We’ve just scratched the surface in terms of learning what these ancient animals can teach us, as well as possibly provide us in terms of direct biomedical benefits.”
You can read more about the new study here.