Researchers have edited-out a mosquito gene that could stop the transmission of malaria.

Using the CRISPR/Cas9 gene-editing technology, scientists have shown that inactivating the mosquito gene FREP1 reduces their susceptibility to infection with Plasmodium - a genus of parasites that causes malaria in humans. 

Inside certain types of mosquito, Plasmodium undergoes a series of infection steps before reaching the mosquito’s salivary gland, from which it spreads to bitten humans.

This infection cycle relies on the activity of several mosquito proteins.

Researcher George Dimopoulos and his team at Johns Hopkins University previously identified and examined several mosquito proteins involved in Plasmodium infection, including fibrinogen-related protein 1 (FREP1).

They then used CRISPR/Cas9 to inactivate the FREP1 gene in Anopheles gambiae mosquitos and explore the effects on malaria parasite infection.

The team found that FREP1 inactivation via CRISPR/Cas9 significantly suppressed infection of the mosquitos with both human and rodent Plasmodium parasites.

They say it is possible that the technology could be used to alter the genomes of wild mosquito populations to prevent the spread of malaria, which kills nearly 500,000 people worldwide every year.

However, the permanent inactivation of FREP1 in all mosquito stages and tissues also resulted in fitness costs for the mosquitos, including reduced blood-feeding ability, lower fertility, a lower egg hatching rate, slowed development, and reduced longevity after feeding on blood.

This raises concerns that mosquitos with permanently inactivated FREP1 would not be able to compete with non-mutant mosquitos in the wild effectively enough to block malaria transmission.

The investigators are now exploring ways to inactivate FREP1 in the gut of adult female mosquitoes only, with the hope to reduce the fitness cost while retaining resistance to the malaria parasite.

The study is accessible here.