Axonal Odorant Receptors Mediate Axon Targeting

Abstract

Summary: In mammals, odorant receptors not only detect odors but also define the target in the olfactory bulb, where sensory neurons project to give rise to the sensory map. The odorant receptor is expressed at the cilia, where it binds odorants, and at the axon terminal. The mechanism of activation and function of the odorant receptor at the axon terminal is, however, still unknown. Here, we identify phosphatidylethanolamine-binding protein 1 as a putative ligand that activates the odorant receptor at the axon terminal and affects the turning behavior of sensory axons. Genetic ablation of phosphatidylethanolamine-binding protein 1 in mice results in a strongly disturbed olfactory sensory map. Our data suggest that the odorant receptor at the axon terminal of olfactory neurons acts as an axon guidance cue that responds to molecules originating in the olfactory bulb. The dual function of the odorant receptor links specificity of odor perception and axon targeting. : Odorant receptors play a critical role in the sensory map formation. Zamparo et al. find that axonal odorant receptors respond to cues expressed in the olfactory bulb. Among these, PEBP1 acts as a putative ligand of axonal receptors, and its genetic ablation results in a disrupted sensory map in vivo. Keywords: axon targeting, topographic map, olfactory bulb, axonal odorant receptors