Using Genetics to Make a Life-saving Perfume

A Gene Mosquitoes Use to Detect Human Sweat

Raji et al. (2019) discovered an antennal co-receptor, Ir8a, that mosquitoes need in order to detect odors in human sweat. Without this gene, Aedes aegypti mosquitoes have reduced attraction to human hosts. This video summarizes the key findings of the study and presents the diverse group of scientists assembled by Dr. Matthew DeGennaro that made this publication possible.

Towards a molecular understanding of mosquito host detection

Mosquitoes obtain blood-meals from vertebrate hosts to enable egg production. Blood is not the only source of nourishment for mosquitoes. Both male and female mosquitoes seek nectar sources from plant hosts. Since males male do not bite, nectar is their principle energy source.  Mosquitoes gain access to these nutrients by sensing volatile chemicals in their environment. Olfactory cues such as body odor, carbon dioxide, and nectar volatiles are sufficient to enable mosquito attraction. Understanding how mosquitoes sense their hosts is the focus of the DeGennaro lab. Using a molecular genetic analysis of mosquito behavior, we seek to identify the odors and olfactory receptors that are necessary for mosquito host detection.

Aedes aegypti  female feeding on a human host.

Aedes aegypti female feeding on a human host.

Mutant Mosquitoes Hold the Key to a Life-saving Perfume

Previous work

My post-doctoral research in Leslie Vosshall's laboratory at Rockefeller University established techniques to edit the genome of mosquitoes. Using this approach, I demonstrated that the mosquitoes use the OR/ORCO olfactory receptor pathway to respond to human odors and the insect repellent, DEET, as well as nectar volatiles. My work implicated the Ionotropic Receptor (IR) family of olfactory receptors in mosquito host-seeking. In addition, I showed that DEET repels mosquitoes in two distinct ways: through ORCO-dependent olfaction and a yet to be identified taste receptor. My laboratory at Florida International University is expanding on this work in three main areas presented below.


Current Projects

Testing the response of female  Aedes aegypti  to a human host using an olfactometer.

Testing the response of female Aedes aegypti to a human host using an olfactometer.

Identifying the mosquito receptors for human odor

          The goal of this project is to identify olfactory receptors that enable the zika and dengue fever mosquito, Aedes aegypti, to be attracted to humans. The proposed research promises to (1) provide insight into the genetic basis of mosquito attraction to humans and (2) provide specific information useful for preventing the spread of human disease by mosquitoes. Our hypothesis is that the ionotropic receptor (IR) pathway that is retained in orco mutants is essential for mosquito attraction to humans. By combining loss-of-function behavioral studies with an IR expression map, we will identify IRs that are candidate human odor receptors. These candidate odor-selective IRs and their cognate IRCOs will be screened using human odor components. Identifying behaviorally relevant mosquito receptors and the human odors that activate them will provide molecular insights that can be used to make mosquito behavior less harmful.


Aedes albopictus  male caught in the act of nectar-seeking.

Aedes albopictus male caught in the act of nectar-seeking.

Genetic analysis of mosquito nectar-seeking

          Identifying the receptors that enable mosquito nectar-seeking behavior is one of our interests. We know that the olfactory receptor co-receptor, ORCO is necessary for both male and female mosquitoes to respond to nectar volatiles. The ORs that provide the odor-ligand specificity are unknown. In this project, we seek to identify receptors using a combination of loss-of-function behavioral studies and cell-based assays. In addition, the first meal a female mosquito ingests consists of nectar not blood. We are interested in learning more about the molecular basis of this switch from nectar-seeking to human host-seeking behavior. This research could set the stage for a novel approach to lock female mosquitoes in a behavioral state where they never become interested in human hosts.

Female  Aedes aegypti  in a 2-port olfactometer-based choice assay

Female Aedes aegypti in a 2-port olfactometer-based choice assay

Vector ecology of Aedes aegypti in South Florida

          Our lab is located in a region where Aedes aegypti is prevalent and local transmission of the zika virus is occurring. We are developing projects to understand the vector ecology of mosquito host interactions in south Florida. Our work is supported by the Centers for Disease Control as part of the statewide "Southeastern Regional Center of Excellence in Vector-Borne Diseases: The Gateway Program" and the Florida Department of Agriculture and Consumer Services.  In particular, we are interested in zika prevalence in wild populations and the behavior of Aedes aegypti in urban environments. We are currently testing a new mosquito trap in the field to improve mosquito surveillance and reduce mosquito populations.

Cnidarian Genetics

          Our lab is working with the Rodriquez-Lanetty laboratory at FIU in an NSF-funded collaborative grant to develop a laboratory model system to study the genetics of coral symbiosis, immunity, and chemosensation using Aiptasia and Cassiopea as well as their photosynthetic symbionts, Symbiodiniaceae (formerly Symbiodinium spp.). Our collaborative group at FIU is working with laboratories at Stanford University, Oregon State University, and the Carnegie Institute to achieve our goals.

 Cassiopea collected in the Florida Keys

The DeGennaro lab (Fall 2018)

The DeGennaro lab (Fall 2018)

We are looking for a graduate students interested in coral genetics, mosquito genetics, or vector ecology to apply for Fall 2020 admission. Please email me if you are interested.

Here is a link to the FIU Biology Ph.D. application requirements.

Header mosquito photo by Alex Wild.