Genetic engineering could eventually be used to control invasive mouse populations, according to Australian researchers who have developed the first gene drive proof of concept in a mammal.
In research published in the Proceedings of the National Academy of Sciences, scientists have demonstrated for the first time that a gene drive can be used to induce female infertility in the common house mouse (Mus musculus), an invasive species in Australia.
The study’s lead researcher, Prof Paul Thomas of the University of Adelaide, said the team’s initial focus was potentially to use the technology on small islands, which would provide natural geographic barriers, and where invasive rodents were a threat to nesting seabirds.
Their computer modelling suggested it could take about 20 years for 250 genetically engineered mice to eradicate an island population of 200,000 mice.
Gene drives have been proposed as mechanisms to suppress the population of certain organisms, such as invasive species and disease vectors, but are yet to be implemented in practice.
In most animals, a single gene copy has a 50% chance of being passed down to organism’s offspring, in a pattern known as Mendelian inheritance. But gene drives rely on naturally occurring or synthetic “selfish genetic elements”, which are inherited at much higher rates.
The team created the gene drive proof of concept in laboratory mice, using the DNA-editing tool Crispr. They used a naturally occurring gene carried by male mice, which is transmitted to 95% of offspring.
“What we did … is to tweak that so-called selfish genetic element so it also creates a female infertility DNA change,” Thomas said.
“What would happen in an island scenario is if you put just a small number of these gene-drive mice on the island … you’ll also get spread of this infertility gene change,” he said. “Once this change has gone through the population, individuals that carry it will start to breed with each other” – resulting in a population crash.
Thomas said the use of the gene drive in a field release was at least five years away, and would only go ahead if further testing showed it could be safely implemented without unintended impacts. The gene drive should not affect native rodent populations because it would not be transmitted across species, he said.
“It’s really important that we only develop versions of the drive that have some sort of in-built safety switch, so that we don’t have any prospect of it ending up in non-target native populations,” Thomas said. The researchers have been developing the gene drive since 2017.
The research received funding from the South Australian and New South Wales governments. South Australia’s deputy premier, Susan Close, said in a statement: “These promising findings demonstrate how gene drive technology may be a game changer in managing the impacts of mice on our environment, community, and agricultural sector.”
Steve Henry, a researcher and mouse expert at the CSIRO, described the gene drive technology as an additional avenue in a portfolio of efforts to control mouse populations. “It’s at the cutting edge of tech and so the timeline to application is potentially long.”
More research would be needed to understand whether it could be applied in the agricultural setting, Henry said. “The issue we have with mice in cropping systems now is that there is only one tool to control them, and that’s zinc phosphide on grain. Because of that, we have to be very careful about the way we use it.”
The development of gene drives is controversial, with some scientists arguing that global frameworks are needed to regulate a transformative technology with potentially dangerous unforeseen effects.
A report published by the CSIRO in June surveyed nearly 4,000 Australians on their attitudes to gene drive technology. Two thirds of respondents were supportive or strongly supportive of their development for pest control, it found, and people were more likely to be supportive if they felt feral cats were a problem in their local area.
Gene drives have also been proposed in insects, for example, to target Anopheles mosquitoes, which are vectors of malaria.
