McGlothlin Research Explores the Evolution of Toxin Resistance in Snakes
November 17, 2014
The rough-skinned newt is easily one of the most toxic animals on the planet, yet the common garter snake routinely eats it. How does a newt which produces enough toxin to kill several grown humans manage to become prey in the food chain?
The answer comes in the form of an evolutionary arms race that pits the toxin of the newt, tetrodotoxin or TTX, against the voltage-gated sodium channels of the snake. The newt’s toxin typically blocks sodium channels, which are found in excitable tissue including muscles, nerves, brain, and heart, but garter snakes seem immune to its effects.
Joel McGlothlin, assistant professor of biological sciences in the College of Science at Virginia Tech with a team of scientists that included his former postdoctoral advisor Edmund Brodie III of the University of Virginia, looked for clues to the evolution of TTX resistance in the DNA sequences of garter snake sodium channels.
“There are nine different sodium channels in reptiles, found in different tissues of the body,” McGlothlin said. “We knew when we started that muscle channels had evolved resistance to TTX in garter snakes, and we predicted that many of the others should have too. If you’re going to eat poison, you not only need to have muscles that work, the nerves that control them have to work too.”
McGlothlin sequenced the DNA of five previously undescribed garter snake sodium channels and examined them for signatures of TTX resistance. Of these, three are found primarily in the brain and two are found in motor and sensory nerves outside the brain. The brain channels had not evolved resistance to TTX at all.
The paper, published in the journal Molecular Biology and Evolution, shows that at least three sodium channels contribute to resistance to TTX: NaV1.4 in muscle, NaV1.6 in rapid-firing neurons, and NaV1.7 in sensory neurons involved with smell and pain sensation.
Read the full story by Rosaire Bushey at VT News.