Researchers find gene to convert female Aedes aegypti mosquitoes to non-biting males with implications for mosquito control

The Aedes aegypti mosquito has been identified as the primary vector for transmission of the Zika virus. (Texas A&M AgriLife Extension Service photo)

The Aedes aegypti mosquito has been identified as the primary vector for transmission of the Zika virus. (Texas A&M AgriLife Extension Service photo)

A collaboration between Virginia Tech and Texas A&M recently confirmed that a single gene can take the bite out of the prime carrier of viruses that cause dengue fever and Zika in humans.

Researchers from Dr. Zach Adelman’s and Dr. Zhijian Tu’s labs have found that a male-determining gene, called Nix, when inserted into a chromosomal region inherited by female Aedes aegypti mosquitoes can convert them into non-biting males.

The findings were recently published in the Proceedings of the National Academy of Sciences.

According to the paper, the presence of the male determining locus, or M locus, establishes the male sex in Aedes aegypti mosquitoes and is only inherited by the male offspring. They found that inserting the Nix gene into a chromosomal region into females can sufficiently convert females into fertile males.

Female Aedes aegypti mosquitoes require blood to produce eggs, which makes them prime carriers of the pathogens that cause Zika and dengue fever in humans. Male mosquitoes, on the other hand, are unable to bite and transmit the pathogens to humans.

These newly-inherited traits would help in creating new population control methods for Aedes aegypti.

“It may be possible to develop genetic approaches that improve ability to perform mass rearing and separation of males and females for sterile insect technique-based control,” Adelman said. “These results also indicate a potential pathway to developing self-sustaining transgenic approaches such as gene drive to suppress Aedes aegypti populations.”

The researchers generated and characterized multiple transgenic mosquito lines that expressed an extra copy of the Nix gene under the control of its own promoter. With the help of members of the Virginia Biocomplexity Institute and Initiative at the University of Virginia, they found that the Nix transgene alone, even with the M locus, was enough to convert females into males with male-specific sexually dimorphic features and male-like gene expression.

Researchers also found an additional gene in males called myo-sex that is needed for male flight and that the newly-converted males did not inherit this gene that is located within the M-locus. Although flight is needed for mating, the newly-converted males were still able to father viable sex-converted offspring when presented with cold anesthetized wild-type females, they said.

More research is needed, however, before potentially useful transgenic lines can be generated for initial testing in laboratory cages.

In the future, they are wishing to explore the mechanism by which the Nix gene activates male developmental pathway and are also interested in learning about how it evolves within the mosquito species of the same genus.

The researchers are hoping that their findings will inform future investigations into homomorphic sex chromosomes that are found in other insects, vertebrates, and plants.

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