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UGA Researchers Receive NSF Grant to Study Hormone Regulation in Mosquitoes

Donna Huber on September 6, 2017

mosquito

Athens, GA–Mosquitoes transmit diseases such as Zika virus, dengue, and malaria to people and other vertebrates worldwide. In a newly funded National Science Foundation (NSF) project, Michael Strand and Mark Brown, both professors in the Department of Entomology and members of the Center for Tropical and Emerging Global Diseases, hope to gain new insights into how hormones coordinate immune responses with reproduction.

The immune and reproductive systems of all animals, including mosquitoes, require large amounts of energy but how these energetic demands are regulated at the molecular level are poorly understood. How immune defenses are regulated relative to other functions like reproduction is of long-standing interest and the main goal of this project is to answer this question.

Strand and BrownMosquitoes provide an interesting system for addressing these issues because almost all species must feed on blood from a vertebrate host, such as humans or another animal, to reproduce.  However, blood feeding exposes mosquitoes to microorganisms that cause disease in mosquitoes, the vertebrate hosts mosquitoes feed upon, or both.  Background studies by Strand and Brown have shown that certain hormones co-regulate reproduction and immune defense.

“What we hope to characterize in this project are the biochemical pathways these hormones interact with, and how these pathways affect the ability of mosquitoes to defend themselves from infection,” said Strand. “We also will learn whether these pathways function similarly or dissimilarly between species.”

The fundamental questions about reproduction and immunity that this project is designed to answer apply not only to mosquitoes but to all animals. “The information we generate will also potentially provide information that can be applied toward reducing mosquito reproduction and transmission of pathogens that cause human disease,” said Strand.

NSF requires grant recipients to engage in activities that have broader impacts that enhance STEM education and improve science literacy in the general public. “The public at-large generally knows that mosquitoes can transmit human diseases, but people often do not understand how disease transmission occurs or why some mosquito species are disease vectors but most are not,” said Strand. In conjunction with Georgia 4-H and the Cooperative Extension Program at UGA, teaching materials for middle and high school students will be developed that explain disease transmission, the mosquito life cycle, and strategies for controlling vector populations.

National Science Foundation Award #1656236 “Endocrine regulation of immunity and reproduction in mosquitoes”

Writer: Donna Huber

Contact: Michael Strand, Mark Brown

UGA researchers find hormone receptor that allows mosquitoes to reproduce

Donna Huber on April 8, 2015

Mark Brown mosquito
Dr. Mark Brown’s mosquito lab in Athens. September 2010

Athens, Ga. – University of Georgia entomologists have unlocked one of the hormonal mechanisms that allow mosquitoes to produce eggs.

The results provide insight into how reproduction is regulated in female mosquitoes, which transmit agents that cause malaria and other diseases in humans and domestic animals. Their work was published in the April edition of the Proceedings of the National Academy of Sciences.

The model for this research is the yellow fever mosquito, Aedes aegypti. Females have to consume a blood meal before they are able to produce a batch of eggs. The blood meal triggers the mosquito’s brain to release two hormones, an insulin-like peptide known as ILP and an ovary ecdysteroid-ogenic hormone known as OEH, which activate processes in the female mosquito that result in mature eggs.

Many hormones, including OEH and ILP, act through receptors on the surface of cells. In 2008, study co-authors Mark Brown, a professor of entomology, and Michael Strand, a Regent’s Professor, characterized the receptor for ILP in mosquitoes, which helped reveal many details about its role in egg formation. OEH plays an equally important role in female reproduction, but its receptor was more difficult to identify.

“From previous work, we knew that the fruit fly Drosophila melanogaster does not produce OEH. A different group of fruit flies, including Drosophila mojavensis—as well as all mosquitoes we had genomes for—do have OEH,” said the study’s lead author Kevin Vogel, a postdoctoral fellow also in the College of Agricultural and Environmental Sciences’ entomology department.

“Most hormones bind a single receptor, so we hypothesized that an OEH receptor should be found in mosquito genomes as well as Drosophila mojavensis, but not in the genome of Drosophila melanogaster.”

By identifying and comparing the sequences of more than 400 receptors in the genomes of two fruit flies and three mosquito species, they identified a single gene for a receptor with an unknown function within the species distribution they expected.

By targeting the gene encoding the receptor, the authors found that disabling its expression inhibited the mosquitoes’ ability to produce eggs after a blood meal.

“This receptor fills a major gap in our understanding of the regulation of mosquito reproduction,” Strand said. “Going forward, we are well positioned to better characterize the steps leading to egg production and potentially identify points at which we can disrupt reproduction and control mosquito populations.”

The study is available online at www.pnas.org/content/early/2015/04/02/1501814112. Research reported in this release was supported by the National Institutes of Health under grant numbers R01AI033108 to Brown and Strand and F32GM109750 to Vogel.

For more information on the UGA department of entomology, see www.ent.uga.edu.

Writer: J. Merritt Melancon Mark Brown
Contact:Kevin Vogel Michael Strand