TORONTO -- The potential for humans and other mammals to evolve to become venomous lies within our genomes, a new study suggests.
Published by the Okinawa Institute of Science and Technology Graduate University (OIST) and the Australian National University in the journal PNAS, the study found that the genetic foundation for oral venom to evolve is present in both reptiles and mammals.
The study also provides the first 鈥渃oncrete evidence鈥� of an underlying molecular link between venom glands in snakes and the salivary glands found in mammals, .
鈥淰enoms are a cocktail of proteins that animals weaponized to immobilize and kill prey, as well as for self-defence,鈥� said study author and PhD student at OIST Agneesh Barua in the release. 鈥淲hat鈥檚 interesting about venom is that it has arisen in so many different animals: jellyfish, spiders, scorpions, snakes and even some mammals.鈥�
Barua went on to explain that while those animals evolved in different ways to deliver said venom, 鈥渁n oral system 鈥� where venom is injected through a bite 鈥� is one of the most common and well-studied.鈥�
But researchers had yet to discover the origin of oral venom, something the new research revealed in its latest study into snakes.
Previous research focused on the genes that code the proteins that make up venom, but 鈥渕any toxins currently found in venom were incorporated after the oral venoms system was already established,鈥� Barua said.
The researchers needed to look at the genes that allowed and enabled the rise of venom systems and were present before venom capabilities originated, Barua sad.
The study searched for genes that work with and interact strongly with the venom genes and used venom glands collected from the Habu snake of Taiwan, a type of pit viper found in Asia.
Researchers identified approximately 3,000 鈥渃ooperating genes鈥� and found that they played critical roles in protecting cells from the stress of producing large amounts of proteins 鈥� the same cooperating genes that are key in regulating protein modification and folding.
When making proteins, the way the chains of amino acids are folded together is critical and specific 鈥� similar to the concept that one wrong fold in an origami project can ruin it, the release said. One 鈥渕isfold鈥� can prevent the protein from becoming the shape it needs to function 鈥� and misfolded proteins can accumulate and cause damage to cells.
"The role of these genes in the unfolded protein response pathway makes a lot of sense as venoms are complex mixtures of proteins. So to ensure you can manufacture all these proteins, you need a robust system in place to make sure the proteins are folded correctly so they can function effectively," explained Barua.
When researchers examined genomes and salivary gland tissues in other animals, including mammals like dogs, humans and chimpanzees, they found that they contained their own version of the 鈥渃ooperating genes,鈥� stating they had similar patterns of activity to those seen in snake venom glands.
This gave rise to the researcher鈥檚 beliefs that salivary glands in mammals and venom glands in snakes share an ancient functional core that has been maintained since the two lineages split hundreds of millions of years ago, the release states.
鈥淭his is the first real solid evidence for the theory that venom glands evolved from early salivary glands," said Barua. "And while snakes then went crazy, incorporating many different toxins into their venom and increasing the number of genes involved in producing venom, mammals like shrews produce simpler venom that has a high similarity to saliva."
The findings show the ease with which the function of salivary glands can be repurposed to venom, with Barua citing experiments done in the 1980s on rats and mice, where they showed the saliva compounds of male mice were highly toxic when injected into rats.
鈥淚f under certain ecological conditions, mice that produce more toxic proteins in their saliva have better reproductive success, then in a few thousand years, we might encounter venomous mice," Barua said, adding that although very unlikely, if the right conditions existed 鈥� humans could also become venomous.
鈥淚t definitely gives a whole new meaning to a toxic person.鈥�
