By Liam Mannix
Melbourne scientists are trying to genetically engineer native northern quolls to make them resistant to cane toad toxin.
Quoll numbers across Australia are being decimated by the poisonous toads and Australia’s bushfire crisis, which has destroyed the homes of many endangered species, has sharpened the need to act.
A northern quoll, being held by quoll breeder Trish Mason.Credit: Glen Campbell
Sporting white spots, long tails and a row of sharp teeth, northern quolls are native marsupial carnivores. They eat possums, insects, birds eggs and – since they were introduced from South America in 1935 – cane toads.
But cane toads carry a powerful toxin. Eat them and you die.
The creature’s native predators in South America have evolved genetic resistance to the toxin, but Australia’s animals have never had the chance.
Dr Stephen Frankenberg, the University of Melbourne geneticist leading the project, wants to give evolution a kick along.
Dr Stephen Frankenberg holds a dunnart, the lab creature he is working with as a precursor to the quoll.Credit: Paul Jeffers
The DNA tweak needed to make quolls resistant to the toxin is tiny: changing just two letters of a quoll’s DNA would do the trick.
But it’s never been done in a marsupial. And in the story of genetic engineering, the failures far outweigh the successes.
“It’s just a tiny tweak,” says Dr Frankenberg. “It’s done routinely in lab animals all the time.”
Cane toad toxin kills by sticking to a tiny piece of machinery cells use to balance their salt levels. With the machine gummed up, the cell loses its salt balance and dies.
If you change a single letter in the gene that is responsible for that bit of machinery, you change the shape of the machine. The toxin cannot stick any more.
“It’s just a tiny tweak,” says Dr Frankenberg. “It’s done routinely in lab animals all the time.”Credit: Paul Jeffers
“Over thousands of years, maybe some Australian species will gradually evolve that resistance. But the risk is they would be more likely to go extinct first,” Dr Frankenberg says.
His team already taken several key steps towards his goal.
Working with Museums Victoria, they have sequenced the entire DNA of the quoll and worked out the genetic edits needed.
They have grown stem cells from dunnarts – a native mouse-like marsupial closely related to quolls, chosen because they are easy to work with in the lab – in a dish. And they have been able to edit the cell’s DNA to add toxin resistance.
Credit: Paul Jeffers
“But that’s easy,” says Professor Merlin Crossley, a genetic engineering expert and deputy vice-chancellor at the University of NSW.
“It’s getting from there into embryos, and then getting that into a womb, and then getting a living offspring, and then getting quolls to take care of these genetically engineered offspring ... that’s the real challenge.”
Gene editing has had its successes. Australian scientists have modified sheep to grow bigger, faster, and make more wool. In America, the authorities just approved AquAdvantage salmon – genetically modified to grow twice as fast – for sale to the public.
Some aquariums even sell GloFish, a zebrafish genetically modified to fluoresce under blue light.
But the vast majority of attempts to genetically edit animals have failed. “Look at Dolly the cloned sheep – that was in the '90s. How many cloned sheep have you seen since then?” Professor Crossley says.
Still, editing a quoll is a marvellous idea, he adds.
“I think it’s brilliant. I’m excited by this. I’m very supportive. It’s smart and it builds on the existing science.”
“What are the negatives? One would be cautious about releasing anything genetically modified into the wild, but I believe we could do it.”
Professor Crossley is not involved in the research, which is funded by the Hermon Slade Foundation.