Elissa Hallem (PhD 2005, Neuroscience), assistant professor of microbiology, immunology, and molecular genetics at the University of California, Los Angeles, has been awarded one of this year’s twenty-three MacArthur Foundation “genius” grants. Hallem explores the physiology and behavioral consequences of odor detection – olfaction – in invertebrates and identifies interventions that may eventually reduce the scourge of parasitic infections in humans.
“Both free-living and parasitic animals are capable of detecting and responding to olfactory cues present in their environments,” she says, in describing the work of her lab. “We are interested in understanding the neural basis of these odor-driven behaviors. We are also interested in how olfactory neural circuits can evolve in species with different lifestyles and ecological niches to mediate species-specific behavioral requirements.” She studies these questions using the parasitic and the free-living nematode C. elegans as model systems.
Hallem’s graduate studies of olfaction in fruit flies revealed several important and unexpected insights. Starting with a mutant fly strain that lacked odorant receptors in a subset of olfactory neurons, she produced more than twenty different transgenic fruit fly lines, each expressing a single, known odorant receptor gene in these neurons. She then measured the flies’ electro-physiologic responses to a set of more than one hundred different odorants, demonstrating that some odorant receptor types were highly selective and others were more broadly tuned, with an unexpectedly high fraction of odorant/receptor combinations inhibiting (rather than increasing) the firing rates of neurons. As a postdoctoral fellow at the California Institute of Technology, she shifted her attention to the connection between chemoreception and behavior, using as a model system the nematode worm C. elegans. Parasitic nematodes infect more than 20 percent of people across the globe, particularly in tropical regions. Her research is identifying interventions, pharmacologic or behavioral, that may eventually reduce the scourge of parasitic infections in humans. Her scientific articles have appeared in such publications as Nature, Cell, Current Biology, and PNAS. (AP Photo/Courtesy of the John D. and Catherine T. MacArthur Foundation, Stephanie Diani)