Scientists Create First-Ever map of smell receptors in the nose

Amazing stuff!

"At a glance

• Scientists have created the first detailed map of smell receptors in the nose, catching up with similar achievements in sight, hearing, and touch.
• The map reveals that smell receptors are highly organized into tight bands based on type.
• The findings provide foundational knowledge needed to develop better therapies for loss of smell.

...

Yet from a scientific perspective, “olfaction is super-mysterious,” ... with basic biological understanding lagging behind that of vision, hearing, and touch. ...

Working in mice, ... team have now created the first detailed map of how the thousand-plus types of smell receptors in the nose are organized.

They discovered that unlike what scientists had long believed, the neurons expressing these receptors have a high degree of spatial organization: They form horizontal stripes based on receptor type from the top of the nose to the bottom. ..."

From the highlights and abstract:

"Highlights

• ∼1,100 olfactory receptors adopt stereotyped spatial distributions in the epithelium

• Epithelial space coherently regulates the graded expression of ∼250 genes

• Precursor spatial identities bias olfactory receptor choice

• Receptor positions in the nose are aligned with their axonal targets in the brain

Summary

Although topographical maps organize many peripheral sensory systems, mouse olfactory sensory neurons (OSNs) are thought to randomly choose which one of ∼1,100 possible olfactory receptors (ORs) to express, with spatial organization in the olfactory epithelium limited to a handful of broad anatomical “zones” that modestly restrict OR choice.

Here, we reveal that each OR is instead expressed at a unique mean dorsoventral position, thereby instantiating a stereotyped receptor map in the olfactory epithelium.

OSN dorsoventral identities are encoded by a coherent gene expression program, which includes key transcription factors and axon guidance molecules; use of this program reflects a dorsoventral gradient in retinoic acid signaling, translates each physical location into a spatially appropriate distribution of potential OR choices, and aligns receptor maps in the nose and brain.

Spatial order in the olfactory system, therefore, arises from a continuously varying transcriptional code that precisely organizes the many discrete channels responsible for smell."

Scientists Create First-Ever ‘Smell Map’ | Harvard Medical School "A detailed diagram of smell receptors in the nose fills in missing details of how olfaction works"

A spatial code governs olfactory receptor choice and aligns sensory maps in the nose and brain (open access)

Graphical abstract

Figure 2 Each OSN subtype occupies a unique region of the epithelium