Mosquitoes are one of humanity’s greatest nemeses, estimated to spread infections to nearly 700 million people per year and cause more than one million deaths.

UC Santa Barbara Distinguished Professor Craig Montell has made a breakthrough in one technique for controlling populations of Aedes aegypti, a mosquito that transmits dengue, yellow fever, Zika and other viruses. The study, published in the Proceedings of the National Academy of Sciences, documents the first use of CRISPER/Cas9 gene editing to target a specific gene tied to fertility in male mosquitoes. The researchers were then able to discern how this mutation can suppress the fertility of female mosquitoes.

Montell and his coauthors were working to improve a vector-control practice called the sterile insect technique (SIT). To manage populations, scientists raise a lot of sterile male insects. They then release these males in numbers that overwhelm their wild counterparts. The idea is that females that mate with sterile males before finding a fertile one are themselves rendered infertile, thereby decreasing the size of the next generation. Repeating this technique several times has the potential to crash the population. What’s more, because each generation is smaller than the last, releasing a similar number of sterile males has a stronger effect over time.

SIT has proven effective in managing a number of agricultural pests, including the medfly (Mediterranean fruit fly), a major pest in California. It has also been attempted with A. aegypti mosquitoes, which originated in Africa, but have since become invasive across many parts of the world, due in no small part to climate change and global travel.

In the past, scientists used chemicals or radiation to sterilize male A. aegypti. «There are enough genes that affect fertility that just a random approach of blasting a large number of genes will cause the males to be infertile,» said Montell, the Duggan Professor of Molecular, Cellular, and Developmental Biology. However, the chemicals or radiation impacted the animals’ health to such an extent that they were less successful in mating with females, which undercuts the effectiveness of the sterile insect technique.

Montell figured there had to be a more targeted approach with less collateral damage. He and his colleagues, including co-first authors Jieyan Chen and Junjie Luo, set out to mutate a gene in mosquitoes that specifically caused male sterility without otherwise impacting the insects’ health. The best candidate they found was b2-tubulin (B2t); mutation of the related B2t gene in fruit flies is known to caused male sterility.

Story Source:
Materials provided by University of California — Santa Barbara. Original written by Harrison Tasoff. Note: Content may be edited for style and length.