Mutant mosquitoes don't smell

Kat -   And finally, I just wanted to wrap up with a completely different story which is about mutant mosquitoes and the headline being, mutant mosquitoes don't smell.  What's this story about?

Matt -   OK, so this is a research that was covered by Leslie Vosshall who's a Neurobiologist at Rockefeller University in New York.  Her lab a few years ago was studying Drosophila.

Kat -   These are little fruit flies.

Matt -   These are little fruit flies which have been the standard lab tool for geneticists for a good century and they're really easy to study genetically and to modify, and to look at how genetic modifications change their behaviour.  They were able to genetically modify some fruit flies that lost their sense of smell and they did this by mutating a single gene that makes a protein that forms a complex with all the smell receptors in the Drosophila's antennae, their version of their nose.  Without this co-receptor, the smell receptors don't form a functioning protein.  Now, they've been able to translate this research into mosquitoes, into the mosquito Aedes aegypti which is the mosquito that carries dengue and yellow fever.  They showed that they were able to genetically modify this protein in the mosquito as well.  The interesting thing then was that the mutant mosquitoes weren't able to discriminate between humans and guinea pigs which normally mosquitoes will be able to do.

Kat -   Bad news for the guinea pigs.

Matt - Absolutely, so as to feel the guinea pigs' pain, there's also a human experiment in which Professor Vosshall volunteered herself to take part in this, which was to offer the mutant mosquitoes a normal human arm, and one that's been slathered in DEET which is the component of many insect repellents, what was interesting was the mutant mosquitoes weren't repelled by DEET, which is what normal mosquitoes would be.

Kat -   It was interesting as well because they couldn't tell the difference between an arm that smelled of DEET and one that didn't, but when they got onto the arm, they really didn't like it and they went away.  So, maybe DEET is having another effect that's not just smell too.

Matt - Yes, so rather than carrying on and feeding, and they did - they were eventually repulsed when they were actually in direct contact.  So, perhaps to do the taste pathway, this is building her body of knowledge and it could really help with some new generation of insect repellents, and it's worth pointing out that this protein is present called Orco which is the co-receptor, it's found in all insects as well, so it could be transferred to other disease carrying insects.  I just think it's a great example of how playing about with fruit flies and studying their genes, and perhaps that's seen as something that doesn't have much of an endpoint.  It can be translated and now, we're really seeing the fruits of that fundamental knowledge.