The Junction

Gene Drives could eradicate invasive species – but is the risk too great?

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Imagine being able to wipe out mosquitos carrying malaria, rid areas of environmentally harmful cane toads, and possibly save endangered species by simply editing the DNA of a few toads and releasing them back into the wild. Years ago, this possibility would’ve been off the table, but now – the technology has caught up and these strategies may be possible.

For years, governments have been testing ways to deal with invasive species that threaten biodiversity through methods like quarantine regions and biological control or introducing natural predators to the problematic species that pose no environmental harm. Now, scientists may have found a cheaper, more effective solution to the problem: gene drives.

HOW WOULD GENE DRIVES WORK?

Though the science behind gene drives is a bit complicated, the concept is relatively simple. “Gene drives are designed to force a particular genetically engineered trait to spread through an entire wild population. The intent is to change the genes of entire species or even cause deliberate extinctions,” says Louise Sales of Friends of Earth Australia.

One approach involves using CRISPR, a gene editing tool which allows scientists to edit an organism’s DNA. CRISPR gives scientists the ability to program specific bits of DNA and modify genomes, allowing them to manipulate natural selection. This could be the solution to eradicating a number of invasive species from environments in need of protection; however, there’s growing controversy regarding its safety and questions around whether scientists’ can control the spread of the genetically modified creatures.

Paul Thomas, professor of biochemistry and researcher at the University of Adelaide, says gene drives first sparked his interest back in 2015 after he came across a publication showing that CRISPR gene drives could potentially modify entire populations of flies. For a number of years now, he has been using CRISPR technology in his lab to test mammalian genes, modifying the mouse genome and creating mouse models of human disease.

“We’re pretty close now to working out whether gene drives are going to be able to work in mice,” he says. He claims that mastering this technique will deliver an important breakthrough in areas like pest control.

“One reason we wanted to embark on this is that we could see that there would potentially be applications in basic pest population control for many different vertebrate pests that are problems around the world, particularly in Australia where we have lots of introduced species that cause havoc.”

POTENTIAL ENVIRONMENTAL RISKS

Thomas says one of the most challenging things about studying these genetically modified mice is making sure it’s being done safely – since any mice escaping from the lab and integrating into the wild population would pose a huge problem.

This problem still arises when introducing modified mice to isolated locations, such as islands. “If we went and wiped out a mice population on an island that’s all well and good, but if mice escape from that island and get back to the mainland to places like Europe and Asia then it could cause havoc in a place where you wouldn’t want to wipe out the population,” he explains.

Cane toads, a fast-spreading pest commonly found in northern Australia are a prime example of this.

“People are interested in getting rid of cane toads which sounds like a great idea, but if we use a gene drive for that and some of those cane toads were somehow transported back to South America where they’re native, that could cause havoc in their native population.”

Dr. Kevin Esvelt of MIT, who first proposed the idea of using CRISPR technology as a solution to pest species, said in an interview with the New York Times that the risk of modified creatures spreading is an “unacceptable risk.”

On top of this, there’s no solid way to predict what type of impact removing a species will have on an ecosystem. For example, Thomas says that while removing pest mice from an area might be very good for grain farms, there may be “unintended, unforeseen consequences,” such as impacts on the food chain. Since mice provide a source of food for scavengers like feral cats, taking mice out of the ecosystem could increase the possibility that these cats will start feeding on native species.

TECHNICAL ISSUES: GENE DRIVES STILL WORTH INVESTING IN?

One of the biggest obstacles at the moment to effective gene drives are populations developing resistance alleles – defences which could make a chromosome permanently resistant to the gene drive activity. Thomas says that one possible solution, still in its infancy, is using a multiplex gene drive which at the most basic level entails cutting the DNA in several spots instead of one, lowering the likelihood of resistance. This approach is currently still exploratory, requiring further research.

Another risk is that the modified genes could spread to genetically similar species. For example, editing pest mice could result in the gene “jumping species” into the native mouse population through mating, which would cause irreversible harm to the ecosystem.

So, with further research into the management of altered species – are gene drives still a plausible solution to the pest problem or a dangerous territory that should be left uncharted?

Sales says that all of these potentially devastating issues raise the question of whether it is a good idea to “invest millions of dollars in this risky new technology with no guarantee that it’ll actually work, as opposed to investing in proven strategies to control invasive species.”

Friends of the Earth Australia has flagged a proposal by CSIRO scientists to release genetically-altered mice that will only have male babies, wiping out the population on selected islands off the WA coast, as of big concern, she says.

She says that Friends of the Earth Australia is calling for a larger conversation on gene drives, saying that the industry shouldn’t be the ones writing the rules when there’s so much at stake.

As opposed to protecting a population, “gene drives could also be released into agricultural fields to attack a country’s food production. And gene drive mosquitos and other insects could be engineered to spread lethal toxins in their bite,” Sales says.

“In any conversation about gene drives,” says Sales, “we must understand the potential risks we are creating and our capacity to control them.”

MOVING FORWARD

Thomas says that the area has a lot of potential, but agrees that there is much to be considered before putting the technology to use outside of labs.

“Before we can even begin to explore whether as a society it’s something that we want to deploy, we need to have some basic understanding of whether the system is going to work or not. First of all, we need to see if it works [in mammals], and if it does work, what are the questions that we need to address before we could ever deploy it as a society?”

For example, Thomas says that the technology would need to be tightly regulated and that lots of further testing would be needed before even reaching a point where the technology could be used outside of a laboratory setting.

“It would only be after a mock stage development process that would start off in a laboratory setting possibly with some limited field testing, then an island-type setting, and the mainland would be the last step. You’d want to make sure that at each stage you are fully aware of the consequences. You’re looking at ten or twenty years down the track if we can show that these technologies are successful,” he says.

Gene drives, with further tweaking and testing, could be a solution to the problem of feral pests; however, it will take years of careful testing before we can be sure it is safe to release any of these genetically modified creatures into the wild.

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University student journalism from Australia and the Pacific
Gene Drives could eradicate invasive species – but is the risk too great?