This new tech could spell end for mouse plagues
Invasive mice populations could be a thing of the past, thanks to a new genetic tool developed by a team of Australian scientists.
Researchers at the University of Adelaide have developed t-CRISPR, which uses gene editing technology to alter the fertility gene in laboratory mice to make females infertile.
“This is the first time that a new genetic tool has been identified to suppress invasive mouse populations by inducing female infertility,” said lead researcher Professor Paul Thomas.
“The t-CRISPR approach uses cutting-edge DNA editing technology to make alterations to a female fertility gene. Once the population is saturated with the genetic modification, all the females that are generated will be infertile.
“We are also developing new versions of t-CRISPR technology that are designed to target specific pest populations to prevent unwanted spread of the gene drive.”
The new tool is based on an existing technology, CRISPR-Cas9 gene editing, which has largely been applied to limiting the spread of malaria by making male mosquitoes infertile.
CRISPR 101
Since it was unveiled in 2012, the CRISPR method has been used to edit pieces of DNA inside the cells of organisms, primarily insects.
“Up until now, this technology has been aimed at insects to try and limit the spread of malaria, which causes up to 500,000 deaths worldwide per year,” Luke Gierus, a post-graduate student and the paper’s co-first author, said.
The technology relies on the Cas9 protein found in bacteria, which scientists can program to find and bind to almost any 20-letter sequence of DNA in a gene with the help of a piece of RNA that matches the target DNA sequence.
When it finds the target, standard CRISPR cuts the DNA, and the process of repairing the DNA introduces mutations that can disable the gene.
Other variations of CRISPR can also replace faulty genes, turn genes on or off, or change one letter of the DNA code to another.
In this study, the team simulated what would happen when an edited version of a fertility gene on chromosome 17, which affects the ability of sperm to swim, was introduced to populations of mice.
Males who carry one copy of this gene are infertile, while females are still fertile but only have one functioning version of the gene and can pass on either the functioning or non-functioning version to their offspring.
In females that had a second edited chromosome that affected their fertility, they found that male offspring would all be infertile, while only 50 percent of female offspring would be fertile.
They found that 250 mice with modified genes could eradicate a population of 200,000 mice on an island in around 20 years.
“The use of t-CRISPR technology provides a humane approach to controlling invasive mice without the release of toxins into the environment. We are also working on strategies to prevent failed eradication due to the emergence of gene drive resistance in the target population,” Gierus said.
While t-CRISPR has been developed to specifically target mice, CSIRO Group Leader for Environmental Mitigation and Resilience Dr Owain Edwards said it could be developed to use on other invasive animals.
The researchers, who collaborated with CSIRO, the Centre for Invasive Species Solutions, the Genetic Biocontrol for Invasive Rodents (GBIRd) consortium and the US Department of Agriculture, were supported by both the South Australian and NSW governments.
“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,” South Australian Deputy Premier Dr Susan Close said.
“This cutting-edge research also highlights the global leadership of the South Australian research sector, in finding solutions to social, environmental and economic challenges.
“The South Australian Government is proud to have supported this proof-of-concept, having granted the University of Adelaide $1 million through the Research and Innovation Fund.”
They published their findings in the journal Proceedings of the National Academy of Sciences.
Image: ABC News