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A new way to edit genomes of mosquitoes carrying diseases might help suppress them on a continental scale.

Scientists from the University of California Berkeley and the University of California Riverside have used CRISPR/Cas9 gene-editing technology to insert and spread genes aimed at suppressing wild insects, while also avoiding the resistance to efforts that evolution would typically favor.

The researchers focused on fruit flies in the study, but believe the technique could be used in mosquitoes to fight malaria and other mosquito-borne diseases.

“What we showed is that, if you disrupt a gene required for fertility in female mosquitoes at multiple sites all at once, it becomes much harder for the population to evolve around that disruption,” John Marshall, the study's lead author and an assistant professor of biostatistics and epidemiology at the UC Berkeley School of Public Health, said in a statement. “As a result, you can suppress a much larger population. It's much the same as combination drug therapy; but for CRISPR-based gene drive.”

The researchers focused on a technique called gene drive system, where they manipulated how genetic traits are inherited from parent to offspring. Gene drives are used to bias genetic inheritance in favor of rapidly spreading, self-destructive genes.

This technique could be a cost-effective and environmentally friendly option to suppress populations of disease-spreading insects.

The researchers based their calculations on a gene drive that past research showed could result in up to 99 percent of offspring inheriting the inserted gene.

However, the few offspring that don’t inherit the gene become problematic because a fraction of the offspring become immune to gene drive, resulting in a rapid rebound of those that are gene drive immune.

In the new study, the researchers found resistance would have a major impact on attempts to eliminate a mosquito species on a continent-wide scale but a new technique called multiplexing, which involves using one of the components of the CRISPR system—a guide RNA—to target multiple locations in a gene at once could be effective.

Computer modeling also suggests that the size of the population that could be suppressed increases exponentially with the number of guide RNA’s utilized and that with four or five multiplexed guide RNA’s a mosquito species could be suppressed on a continental scale.

“Knowing that we can potentially overcome the issues of resistance through careful engineering and multiplexing is huge,” co-corresponding author Omar Akbari, an assistant professor of entomology at UC Riverside, said in a statement.

 The study was published in Scientific Reports.

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