The term “genetically modified” rings alarm bells for many, but like the premise or not, the technique is doing good in the world. Engineered mosquitoes are offering us hope of stamping out dengue fever, and now a similar approach could be used to tackle an even bigger problem: malaria.
Published in the Proceedings of the National Academy of Sciences, scientists have used the increasingly popular gene-editing tool CRISPR to create a line of antimalarial mosquitoes that pass on the newly added defensive gene to 99.5 percent of offspring. While the researchers have only trialed this technique on one species of mosquito so far, and further tweaking is required, the scientists say this is a “significant first step” towards larger field trials.
“This opens up the real promise that this technique can be adapted for eliminating malaria,” lead researcher Anthony James from the University of California, Irvine, said in a statement.
The species targeted in this proof-of-concept study is called Anopheles stephensi, which is responsible for about 12 percent of malaria transmission in India. To turn these vectors of disease into weapons against it, the researchers used a system derived from bacteria – CRISPR – to modify their genomes. You’ve probably heard of this before – it was used to make micropigs and muscly beagles in China recently. It basically uses a pair of guided “molecular scissors” to snip a piece of target DNA so that genes can be removed, inserted, or replaced.
This time round, the researchers used the highly precise and efficient tool to add in an “anti-parasite” gene that targets two important proteins produced by the malaria agent, Plasmodium falciparum. To make sure it spreads to offspring, the researchers directed the scissors towards a specific region on the mosquito’s “germ line,” meaning its sex cells (egg and sperm).
After injecting the designer system into mosquito embryos, the researchers found that close to 100 percent of their offspring possessed the desired modification. They were able to determine this because they also slipped in a gene that makes the mosquitoes’ eyes glow red, so by looking at the numbers of fluorescent insects, they could work out how successful the technique was.
While a significant achievement, the scientists have a long way to go before this can be applied to the field. “We know the gene works,” said James. “The mosquitoes we created are not the final brand, but we know this technology allows us to efficiently create large populations.”
Importantly, the scientists need to examine how stable these genes are in different strains of mosquito and environmental conditions. But with the malaria parasite becoming increasingly resistant to both drugs and insecticides, it’s good that scientists are attempting wildly different solutions to this global burden, which kills hundreds of thousands of people each year.