SACHA PFEIFFER, HOST:
Mosquitoes inject the parasite that causes malaria into more than 250 million people each year. New research in the journal Nature suggests a way to prevent that transfer, and it involves a tiny tweak to the mosquito's genes. NPR's Jonathan Lambert has more.
JONATHAN LAMBERT, BYLINE: To spread from one person to another, the parasite that causes malaria has to complete a complicated journey. First, a mosquito has to suck up the parasite from the blood of an infected individual. Then the parasite travels to the gut. There, it faces a big challenge. Here's Ethan Bier, a geneticist at the University of California San Diego.
ETHAN BIER: The most bottleneck step is getting out of the gut and then into the body cavity, where another form of it develops that swims to the salivary gland, where they can then infect the next poor human being that gets bitten.
LAMBERT: Bier explains that to make that important jump, the parasite relies on a protein made by the mosquito itself. But some mosquitoes have a variant of this protein that seems to disrupt that journey.
BIER: There are two variants of a protein in mosquitoes, one of which sustains very effective, efficient malaria transmission and infection. The other doesn't.
LAMBERT: In the lab, Bier and his colleagues used CRISPR gene editing technology to swap the malaria-resistant variant into a susceptible mosquito. One tiny change, altering just a single amino acid, turned out to be enough to keep most of the parasites from reaching their final destination in the mosquito.
BIER: That you can just change a single amino acid in a genome and make a mosquito not transmit malaria, to me, that's kind of cool.
LAMBERT: To spread this beneficial change through an entire population, the researchers want to use a gene drive. Gene drives are sequences of DNA that can be inserted into a genome and change the normal 50/50 rules of inheritance.
BIER: So now all the kids get the genetic element instead of just half of them.
LAMBERT: Gene drives are controversial and haven't yet been used outside of the lab. Critics worry there could be unintended consequences that would be hard to rein in. Here's Dana Perl (ph), a program manager at Friends of the Earth.
DANA PERLS: We don't know enough to understand the consequences of our actions of the genetic engineering.
LAMBERT: Researchers say it'll take several more years of research to even get to the point of field trials. But this study shows that in principle, a tiny tweak to the genome might someday render a whole mosquito population incapable of spreading this deadly disease.
Jonathan Lambert, NPR News. Transcript provided by NPR, Copyright NPR.
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