Odor coding in the mammalian olfactory epithelium

Abstract

Noses are extremely sophisticated chemical detectors allowing animals to use scents to interpret and navigate their environments. Odor detection starts with the activation of odorant receptors (ORs), expressed in mature olfactory sensory neurons (OSNs) populating the olfactory mucosa. Different odorants, or different concentrations of the same odorant, activate unique ensembles of ORs. This mechanism of combinatorial receptor coding provided a possible explanation as to why different odorants are perceived as having distinct odors. Aided by new technologies, several recent studies have found that antagonist interactions also play an important role in the formation of the combinatorial receptor code. These findings mark the start of a new era in the study of odorant-receptor interactions and add a new level of complexity to odor coding in mammals.

A 3D transcriptomics atlas of the mouse olfactory mucosa

“…Past studies yielded inconclusive and sometimes contradictory views on the basic logic underlying the peripheral representation of smell, partly because the topographic distribution of OSN subtypes and their receptive fields still remained vastly uncharted, data on Olfr-ligand pairs was scarce, and the many pitfalls associated with electroolfactogram recordings used to study spatial patterns of odor recognition in the nose (26,71,72).…”

“…Thus, the logic underlying the peripheral representation of smell in the peripheral olfactory system still remains unknown, and it is subject of great controversy (23,26).…”

Editorial for the special issue "Olfactory Coding and Circuitries"

“…Also, some smaller rodent olfactory subsystems are introduced and reviewed. The contribution of Kurian et al (2021) reviews the current knowledge of how odors are coded in the OE, the first stage of the olfactory system. This review deals with the mechanism of combinatorial receptor coding and provides a possible explanation as to why different odorants evoke a distinct percept.…”

Bioinformatic Identification of Putative Enhancers in Mouse Odorant Receptor Loci

“…The molecular basis of mammalian olfaction is centered within cells called mature olfactory sensory neurons (mOSNs) which are each specialized for the detection of particular chemical odorants (Malnic et al, 1999;Kurian et al, 2021).…”

“…While ORs genes are readily identified through their encoding of conserved amino acid domains, each gene yields a different receptor which binds a subset of odorants with varying affinities (Nara et al, 2011;Jiang et al, 2015). The olfactory system is governed by a central logic in which each individual OSN expresses one and only one OR gene, thus constraining the set of environmental odorants that can stimulate a given mOSN (Nara et al, 2011;Kurian et al, 2021). Additional order is imposed on the system by a concerted morphological pattern within the MOE as mOSNs that express the same OR have their axons converge and terminate at the same glomerulus within the olfactory bulb regardless of where they spatially reside within the MOE (Ressler et al, 1994).…”