Finding the target: How timing is critical in establishing an olfactory wiring map

The human nose expresses nearly 400 odorant receptors, which allow us to distinguish a large number of scents.

Each olfactory neuron displays only a single type of receptor and all neurons with the same receptors connect to the same spot in the brain. This wiring pattern is often described as an olfactory map and serves as an important code book that allows the brain to distinguish between food odors and the scent of a predator, for example.

Unlike other types of sensory cells, which cannot be replaced once damaged, olfactory neurons have a unique regenerative capacity. More remarkably, the regenerated neurons must dispatch their axons on a path through the nasal epithelium to the brain through a distance a thousand times the length of the cell in order to make the proper connections. If regenerated neurons are wired to the wrong location, odor perception would be altered.

Investigator C. Ron Yu, PhD, and his team have identified a developmental window during which olfactory neurons of newborn mice can form a proper wiring map. They have shown that if incorrect neuronal connections are maintained after this window is closed, then regenerated cells will also be mis-wired

This work has potential implications for understanding the regeneration of other types of cells as well, such as for newly generated neurons that repair the brain or spinal cord.

“To repair a damaged spinal cord, you will need to ensure that newly generated motor neurons target the right muscle,” says Yu. “The next goal is to identify the molecular cues that enable correct projections to be established.”

The study was published in the April 11, 2014, issue of the journal Science.