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Gene Drives: Just 100 Infertile Mice Can Eradicate an Island Population

University of Adelaide researchers have shown that it may be possible to eradicate populations of invasive pest animals through the inheritance of a negative gene – a technique known as a “gene drive”.

The deliberate spreading of deleterious genes, such as genes causing sterility, through pest populations using gene drives is viewed as a potential “silver bullet” for conservation science and agriculture (AS, July/August 2017 issue). The technology could also be applied to public health efforts to control the spread of diseases by animals such as mosquitoes.

The researchers developed a realistic mathematical model to predict whether gene drives could be used to eradicate populations of invasive mice from islands, which would be the most likely testing grounds for gene drives in order to minimise the risk of them spreading to non-target populations.

Published in Proceedings of the Royal Society B, the researchers showed by computer simulation that a single introduction of 100 mice carrying a gene drive that caused sterility could eradicate an island mouse population of 50,000 individuals within 4–5 years.

“If viable, this technology offers a humane, targeted solution for invasive species control,” says lead author and mathematical ecologist Dr Thomas Prowse. “This could complement or even replace traditional control methods such as culling, trapping and poison baiting, as well as more advanced biocontrols such as rabbit haemorrhagic disease.

“Our paper indicates that controlling invasive pest populations using gene drives may be feasible, but certainly the hype around this new technology is still some way ahead of the science.”

Gene drives work by overcoming the laws of natural selection, which would typically remove detrimental genes such as infertility from a population. “New CRISPR/Cas9 gene-editing technology enables the gene drive to replicate itself during egg and sperm production,” explains Prof Paul Thomas. “This ensures that it is passed onto the next generation, and ultimately results in spread through the entire population. Our results indicate that placing the gene drive in a fertility or viability gene will eventually cause the population to crash.”

While evolution can upset this process by producing resistant genes that don’t accept the gene drive, the researchers showed that a technique allowing “multiple shots on goal” overcame this problem.

“The next necessary step will be the development of gene drives in laboratory mice under secure conditions to enable improved modelling of this potential for pest eradication,” Thomas says. “This will provide the critical data needed to debate the important questions that remain around biosecurity, regulation and ethics.”