The Ultimate Summer Pest Gets Modified

As summer for many of you has already kicked off, you’re probably spending more time outside doing fun things; I know I am! However, perhaps like me, you’re adventures in nature include being munched on by mosquitoes. Ahh, the joys of summer!

After an escape into the woods by my house, I was covered in those annoying bites and sat down at my computer to catch up on the news. One article jumped out at me as I sat, scratching away. A team of HHMI researchers have just successfully genetically engineered mosquitoes by altering the way they respond to odors, like the smell of humans and the insect repellent DEET. These new findings pave the way to our understanding why the insect is so attracted to humans, and hopefully how to block that attraction so that they don’t bite us!

Yes, mosquito bites are annoying, so putting an end to the itchy welts would be great, but even more importantly, mosquitoes are disease-vector insects. Thus, in 2007, scientists began researching. They announced to the world later that year that they had completed the full genome sequence of Aedes aegypti, the mosquito that transmits dengue and yellow fever.

A year later, HHMI researchers took the sequence and shifted their focus from Drosophila flies to mosquitoes with the specific goal of genetically engineering the insects. They first looked toward something they found ten years previously in flies: a gene called the orco which affects how some insects interact with smell. They injected a genetic modification tool called zinc-finger nucleases into mosquito embryos, waited for them to mature, identified mutant individuals, and generated the newly mutant strains.

Amazingly enough, these new strains had significantly different reactions to smell! When regular mosquitoes were given a choice between a human and any other animal, they happily buzzed toward the human. But the mosquitoes with orco mutations showed hugely reduced preference for the smell of humans over guinea pigs, even in the presence of carbon dioxide, which is thought to help mosquitoes respond to human scent!

The next step was for the team to test whether the mosquitoes with orco mutations responded differently to DEET. When presented with two human arms (one covered in DEET and the other completely bare) the mosquitoes flew equally toward both arms, which suggested they couldn’t smell the DEET. However, once they landed on the arms, those on the DEET covered arm flew immediately away. This was unheard of data, and the team went back to work.

Today the HHMI team is still at work trying to provide insights into how existing repellants work against mosquiotes, then plan to start brainstorming ideas about what a next-generation, possibly genetic, repellant would look like. Until they figure this out however, we all will have to deal with the pesky insects and their bites.

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