Breakthrough Gene Technology Unveils How Humans Detect Trillions of Scents

Humans can distinguish up to a trillion different odors—yet this remarkable ability relies on only about 400 types of olfactory receptor proteins. Because these receptors are notoriously difficult to express in standard laboratory cells, studying how they work has long been a major challenge.

Now, researchers from the Swiss fragrance and flavor company Givaudan have reported a breakthrough in Current Biology: a genetic engineering method that enables efficient expression of human olfactory receptors in ordinary lab cells, opening new possibilities for decoding how we perceive smell.

By precisely modifying the C-terminal region of olfactory receptor proteins, the team succeeded in expressing all known 400 human receptors in human embryonic kidney cells. Using this system, they systematically tested the receptors' responses to hundreds of natural odor molecules, creating a powerful high-throughput screening platform. With it, they identified specific receptors responsible for the scents of ambergris, grapefruit, and cork taint.

Notably, the findings suggest that certain odor molecules can be detected by activating only one—or a very small number—of receptors. This challenges the long-standing "combinatorial coding" theory, which proposes that each smell is recognized through the combined activity of many receptors. The new results imply that some odors may be sensed with far greater receptor specificity than previously thought.

While expression efficiency for some receptors still needs improvement and a few well-known odors remain unassigned, scientists view this work as a major step forward. It complements, rather than overturns, the combinatorial model, and sets the stage for future studies to map the precise receptor activation patterns behind each distinct scent.