First detailed ‘smell maps’ reveal how noses track odours
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A microscope cross-sectional image of a mouse nose, showing the anatomical structure of the nasal epithelium. Credit: Datta Lab
Olfactory receptors in the mouse nose have been mapped out in unprecedented detail — overturning researchers’ understanding of how noses build a sense of smell.
The research, published today in Cell1, shows how around 1,100 olfactory receptors expressed on sensory neurons are organized in tightly regulated spatial locations in the epithelial tissue that lines the nasal cavity. A second study2 provides a complementary atlas of olfactory receptor expression in the olfactory epithelium and their neural connections to the olfactory bulb in the brain.
“For 30 years, we’ve taught students that the mouse olfactory epithelium is divided into a handful of broad zones, within which receptor choice is essentially random,” says Johan Lundström, a psychologist and experimental neuroscientist at the Karolinska Institute in Stockholm.
“This is a landmark paper that overturns one of the foundational textbook models of olfactory organization,” he adds.
Smell stripes
In the study, researchers examined about five million neurons from hundreds of individual mice. They first used single-cell sequencing to identify which smell receptors were expressed by neurons in the nose, and then used spatial transcriptomics to map out where key genes were being expressed. This allowed them to pinpoint where the receptors are and show that they are always arranged in horizontal stripes running from the top of the nose to the bottom.
“Each receptor adopts a particular position in the nose. Since there are a thousand positions in the nose, each receptor is expressed basically in a stripe that overlaps with other receptor stripes, in a thousand overlapping stripes,” says study co-author Sandeep Robert Datta, a neurobiologist at Harvard Medical School in Boston, Massachusetts.
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