From Lab Fruit Flies to Mosquito Extermination in 30 Years

Louis Pasteur famously compared science and its application to a tree and it’s fruit. The path from a fundamental discovery to application can be a long and winding one, but rewarding none the less.

Mosquito

Discoveries in basic genetics have now enabled scientists to wipe out lab populations of the malaria mosquito, Anopheles gambiae. (Anthony Cornel)

Professor Ken Burtis, faculty advisor to the Chancellor and Provost, recently came across an exciting example. Burtis was looking for a study for his first year seminar class when he found a paper from Andrea Crisanti’s lab at Imperial College London. Crisanti’s team was able to wipe out a lab population of Anopheles gambiae mosquitoes by introducing a disrupted gene for sex determination and using CRISPR “gene drive” technology to spread it through the population. Within eight generations, there were no female mosquitoes left for breeding.

Anopheles gambiae is one of the most important vectors of malaria. There’s a great deal of interest in using gene drives or a similar approach with Wolbachia bacteria to control mosquitoes and therefore mosquito-borne diseases such as malaria and dengue fever.

Sex determination in Anopheles mosquitoes is controlled by a gene called doublesex, which can produce two different products depending on splicing of the RNA transcript: one for male and the other, female. Kyros Kyrou, Crisanti and colleagues created a CRISPR gene drive construct that blocked formation of the female version of the gene, causing what would have been female mosquitoes to be sterile.

Burtis, a geneticist who has worked with Drosophila flies, was familiar with doublesex: He discovered the alternative splicing mechanism of this gene almost 30 years ago as a postdoctoral student, working with Bruce Baker at Stanford University.

“It made a perfect example for my class of how basic curiosity-driven research can lead much later to things that will potentially impact human health, and made me happy to see something new come from the work I did so long ago,” Burtis said.

Sadly, Baker died earlier this year. Burtis described him as “one of the world’s great geneticists.” His work showed how genes could be linked to behavior in fruit flies.

“Bruce was a remarkable mentor; very hard to get to know, but very interesting once you earned his confidence. I was lucky to be with him his first three years at Stanford,” Burtis said.

More information

A CRISPR–Cas9 gene drive targeting doublesex causes complete population suppression in caged Anopheles gambiae mosquitoes (Nature)

Scientists just showed how to drive malaria mosquitoes to extinction (Technology Review)

UC Davis Joins Initiative to Fight Malaria in Africa (Egghead)

Control of Dengue Fever With Bacteria-Infected Mosquitoes (Egghead)

Professor’s fly question may hold answer to mosquito-borne fever (UC Davis News)

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