Odor-evoked gene regulation and visualization in olfactory receptor neurons

Odorant-evoked activity contributes to olfactory epithelium organization and axon targeting. We examined the consequences on gene expression of a genetic disruption of the channel responsible for olfactory transduction. Genes encoding calcium-binding EF-hand motifs, were among the most highly regulated transcripts consistent with the central role of Ca²⁺ influx in neuronal depolarization. Several genes encoding integral membrane proteins are also highly regulated. One gene, Lrrc3b, was regulated more than 10-fold by odorant activity. Changes in expression occur within thirty minutes and are maintained for several hours. In genetic disruptions of Lrrc3b, a Lrrc3b-promoter-driven reporter adopts the activity-regulated expression of the endogenous gene. Individual olfactory glomeruli have a wide spectrum of activity levels that can be modulated by altering odor exposure. The Lrrc3b reporter mouse permits direct assessment of activity in identified glomeruli. In stable odorant environments, activity-regulated proteins provide a characteristic signature that is correlated with the olfactory receptor they express.