"A study published in Cell has produced a detailed map of olfactory receptors in the mouse nose, revealing a structured spatial organization that contrasts with earlier models that described the system as broadly zonal and random."
A New Map of the Nose
Researchers mapped the spatial organization of approximately 1,100 olfactory receptors within the mouse nasal epithelium. The study involved the analysis of over 2.3 million olfactory sensory neurons from more than 300 mice, using single-cell sequencing and spatial transcriptomics.
The mapping found that receptors are arranged in horizontal stripes running from the top to the bottom of the nose. Each receptor is expressed in a stripe that overlaps with other receptor stripes, creating a pattern of thousands of overlapping bands.
The Mechanism of Organization
The research, led by neurobiologist Sandeep Datta, identified that the spatial mapping is controlled by a gradient of the molecule retinoic acid. This gradient guides gene activity and determines which receptor each neuron expresses.
"This is a 'transcriptional code' that organizes the receptor layout," the study states.
Experiments that adjusted retinoic acid levels altered receptor expression patterns, indicating its role in development.
Significance and Implications
The findings provide a foundational understanding of smell anatomy in mammals. Previous models described the olfactory epithelium as divided into broad zones with random receptor choice. This study offers a more detailed spatial map, suggesting a more structured arrangement.
The study also found that the arrangement of receptors in the nose aligns with the organization in the brain's olfactory bulb. A companion study provides an atlas of receptor expression and neural connections to the olfactory bulb.
Researchers suggest the findings may aid in understanding how to restore smell in humans who have lost it. The study notes that differences exist between mouse and human noses, though shared mammalian similarities allow for some extrapolation.