Mosquito attraction to humans hinges on a distinctive blend of body odors that people emit. These odors waft through the air and stimulate receptors on the mosquitoes’ antennae. Scientists have attempted to disable these receptors to render humans less detectable to mosquitoes.
Even after removing a set of odor-sensing receptors from the mosquito genome, the insects still manage to bite. A group of researchers reported in the journal Cell on August 18 that mosquitoes have evolved redundant safeguards in their olfactory networks, ensuring they can always detect human scents.
“Mosquitoes are bending the rules about how animals sense smells,” explained Margo Herre, a scientist at Rockefeller University and a principal author of the study.
In most organisms, a single olfactory neuron responds to one odor. “If a human loses a single receptor, the neurons tied to that receptor lose the ability to detect that odor,” notes Leslie Vosshall, a professor and lead author affiliated with the Howard Hughes Medical Institute at Rockefeller University. Yet the new findings show this is not the case for mosquitoes.
“You have to intensify efforts to stop mosquitoes because removing one receptor does not diminish their pull,” Vosshall observes. “Any future strategy to control bites with repellents must account for how resilient human smells are to these insects.”
Meg Younger, a professor at Boston University and a lead author on the paper, recalls that the project began unexpectedly while studying how human scent is encoded in the mosquito brain.
a complex mechanism
Researchers found that neurons activated by the human odor compound 1-octen-3-ol also respond to amines, another class of chemicals mosquitoes use to home in on people. This cross-activation is unusual because traditional models suggest odor-encoding neurons are narrowly tuned to specific cues, implying 1-octen-3-ol neurons should not detect amines.
“Surprisingly, neurons linked to human sensing via 1-octen-3-ol and amine receptors were not separate,” Younger explains. This overlap could allow a broad range of human-related scents to trigger the “human sensing” region of the mosquito brain, acting as a safeguard even if some receptors are lost.
The team also employed single-nucleus RNA sequencing to identify which receptors individual mosquito olfactory neurons express. Olivia Goldman, another lead author, stated that the results offered a wide view of how often receptor co-expression occurs in mosquitoes.
Vosshall suggests that similar receptor co-expression patterns may be present in other insects. Christopher Potter’s group at Johns Hopkins University has reported comparable receptor expression in fruit flies, hinting at a broader strategy among insects that rely heavily on smell.
Looking ahead, Younger’s team plans to investigate the functional significance of co-expression across diverse olfactory receptors and how this arrangement shapes mosquito behavior around humans.
Reference: Cell journal, 2022 study on olfactory receptor co-expression in mosquitoes (attribution: Cell; authors include Younger, Vosshall, Herre, Goldman, and colleagues).
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