Groundbreaking research into the odor-sensing neurons of mice reveals intricate stripes within the nasal structure, challenging longstanding beliefs about the wiring of the sense of smell.
“The sense of smell is vital for our daily experiences,” says Sandeep (Robert) Dutta, a Harvard Medical School professor.
“It informs us about our environment, alerts us to danger, enhances taste, and triggers emotions and memories.”
“However, from a scientific standpoint, the mechanics of smell remain shrouded in mystery.”
In a pioneering study utilizing mice, Dutta and his team found that the neurons responsible for odor receptors exhibit remarkable spatial organization, forming horizontal stripes that extend from the top to the bottom of the nose based on receptor type.
Their findings indicate that the receptor map in the nose is mirrored by an odor map in the brain’s olfactory bulb, shedding light on how scent information is transmitted from the nose to the brain.
“While the discovery of the odor map is groundbreaking, it also lays essential groundwork for developing treatments for olfactory loss, which currently lack effective solutions,” Professor Dutta explains.
“Understanding the fundamental workings of smell is crucial for any modifications to this sense.”
Maps detailing the organization of receptors in the eyes, ears, and skin have been established for a long time, showing how these correspond to maps in the brain.
“The sense of smell, however, has remained a largely unexplored territory,” he notes.
In their comprehensive study, researchers employed advanced techniques like single-cell sequencing and spatial transcriptomics to analyze approximately 5.5 million neurons across over 300 individual mice.
The first technique helped identify the odor receptors expressed by neurons in the nose, while the second enabled localization of these receptors.
“This is likely the most extensively sequenced neural tissue to date, but we required this extensive data to understand the system,” Professor Dutta elaborates.
The team discovered that neurons are structured into dense, overlapping horizontal stripes from the top to the base of the nose, aligned by the type of olfactory receptors expressed.
This well-organized receptor map was consistently observed across different mice, mirroring the olfactory maps in the brain akin to those noted in visual, auditory, and tactile systems.
The researchers further examined how the nose’s odor map is formed, identifying retinoic acid—a molecule crucial for regulating gene activity—as a key player.
The findings revealed that a gradient of retinoic acid in the nose directs each neuron to express the appropriate type of odor receptor based on its spatial positioning.
Altering retinoic acid levels effectively shifts the receptor map vertically.
“We’ve demonstrated that during development, it’s feasible to organize over a thousand distinct odorant receptors into a remarkably precise map that is consistent across various species,” Professor Dutta points out.
A comprehensive paper detailing these findings has been published in Cell.
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David H. Brann et al. Spatial codes control olfactory receptor selection and coordinate sensory maps in the nose and brain. Cell, published online April 28, 2026. doi: 10.1016/j.cell.2026.03.051
Source: www.sci.news
