Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Olfactory Receptor Neurons”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2025

Evolutionary Process Underlying Receptor Gene Expansion and Cellular Divergence of Olfactory Sensory Neurons in Honeybees.

Olfaction is crucial for animals' survival and adaptation. Unlike the strict singular expression of odorant receptor (OR) genes in vertebrate olfactory sensory neurons (OSNs), insects exhibit complex OR gene expression patterns. In honeybees (Apis mellifera), a significant expansion of OR genes implies a selection preference for the olfactory demands of social insects. However, the mechanisms underlying receptor expression specificity and their contribution to OSN divergence remain unclear. In this study, we used single-nucleus multiomics profiling to investigate the transcriptional regulation of OR genes and the cellular identity of OSNs in A. mellifera. We identified three distinct OR expression patterns, singular OR expression, co-expression of multiple OR genes with a single active promoter, and co-expression of multiple OR genes with multiple active promoters. Notably, ∼50% of OSNs co-expressed multiple OR genes, driven by polycistronic transcription of tandemly duplicated OR genes via a single active promoter. In these OSNs, their identity was determined by the first transcribed receptor. The divergent activation of the promoter for duplicated OR genes ensures the coordinated increased divergence of OSN population. By integrating multiomics data with genomic architecture, we illustrate how fundamental genetic mechanisms drive OR gene expansion and influence flanking regulatory elements, ultimately contributing to the cellular divergence of OSNs. Our findings highlight the interplay between gene duplication and regulatory evolution in shaping OSN diversity, providing new insights into the evolution and adaptation of olfaction in social insects. This study also sheds light on how genetic innovations contribute to the evolution of complex traits.

Animals↗
PubMed2025

Genomic plasticity drives olfactory adaptation in a pest fly.

Preference shifts in insects are often driven by changes in the olfactory system, yet the underlying mechanisms remain unclear. The worldwide pest Drosophila suzukii, which oviposits in ripe rather than overripe fruits, provides a powerful model to study these mechanisms and their behavioral consequences. Here, we show that this shift is linked to functional remodeling in four olfactory receptor neurons: ab2B, ab3A, ab4B, and ab10A. While ab3A and ab10A exhibit tuning changes shared with the non-pest relative D. biarmipes, ab2B and ab4B display species-specific adaptations in D. suzukii. These changes result not only from receptor sequence divergence but also from novel innovations: receptor co-expression in ab3A and partitioned expression of Or67a paralogs in ab2B and ab10A. Together, these findings show how genomic plasticity in chemosensory gene families enables rapid sensory adaptation and niche transition.

Journal Article↗
PubMed2025

Determinants of odorant receptor transcription and gene choice.

The mammalian olfactory system enables the detection of a wide variety of chemical compounds via the expression of a repertoire of olfactory receptors comprising the largest gene family in the mammalian genome. Olfactory sensory neurons (OSNs) each express only 1 odorant receptor (OR) gene. In mice, this requires activation of 1 OR gene and repression of over 1,400 other OR genes. In this review, we describe the mechanisms that support the transcription of OR genes and how these mechanisms impact which OR is expressed in each neuron. First, we discuss what is currently known about the role of transcription in OR choice. We then describe the role of specific features of OR genes and enhancers in the regulation of OR transcription. Finally, we discuss characteristics of OSNs which specify transcription of some OR genes while restricting the transcription of others.

Receptors, Odorant↗
PubMed2025

Loss of responses to odorants and pheromones in mPRγ (paqr5b)-knockout zebrafish.

In our previous study, we generated a membrane-type progesterone receptor γ (paqr5b) knockout zebrafish line. Knocking out paqr5b by genome editing resulted in the loss of neurons in the olfactory rosette (OR). These findings indicated that Paqr5b plays an essential role in the formation of olfactory neurons. In this study, we investigated the extent to which paqr5b-/- fish lacking olfactory neurons retain their sense of smell. We used a reported tank for zebrafish olfactory analysis with a dividing plate in the middle. The tank was divided into three zones: the right zone, where test substances were added; the neutral zone; and the left zone. The fish were released into the neutral zone at the beginning of each test, the chemical was added to the corner of the right zone, and a 3-min video was taken to track the movements of the fish. The video was then played back, and the time spent in the three zones was counted manually. Both male and female paqr5b+/+ and paqr5b-/- zebrafish were separately analyzed for time spent in the three zones after exposure to ATP, cadaverine, and the pheromone 17α,20β-dihydroxy-4-pregnen-3-one (DHP). Both male and female paqr5b+/+ zebrafish were strongly attracted to ATP and stayed in the right zone for approximately 2 min (67%). In addition, paqr5b+/+ zebrafish avoided cadaverine and stayed longer in the left zone than in any other zone. In contrast, paqr5b-/- zebrafish stayed in all three zones for approximately the same amount of time, even after exposure to ATP and cadaverine. The paqr5b+/+ fish were attracted to DHP and stayed in the right zone longer. Paqr5b-/- zebrafish of either sex were not reactive to DHP exposure. These results showed that paqr5b-/- zebrafish lacking olfactory neurons lost responsiveness to odorants and pheromones.

Animals↗
PubMed2025

Transcriptional interference gates monogenic odorant receptor expression in ants.

Communication is crucial to social life, and in ants, it is mediated primarily through olfaction. Ants have more odorant receptor (OR) genes than any other group of insects, generated through tandem duplications that produce large genomic arrays of related genes. The mechanism by which olfactory sensory neurons (OSNs) produce a single functional OR from these arrays remains unclear. In ant OSNs, only mRNA from one OR in an array is exported into the cytoplasm, while upstream genes are silent and transcripts from downstream genes remain nuclear. Here, we show that readthrough transcription in the downstream direction generates non-translated transcripts. We also find that OR promoters are bidirectional, producing antisense long non-coding RNAs. We suspect that neither readthrough nor antisense transcription produces functional RNA but that bidirectional transcription alone is critical to suppressing the expression of all other OR genes in a tandem array. Finally, we present evidence that this regulatory architecture is conserved across ants and bees, suggesting that this mechanism for functionally monogenic OR expression is widespread in insects with expanded OR repertoires.

Animals↗
PubMed1979

Development of the olfactory organ in the rainbow fish Nematocentris maccullochi (Atheriniformes, Melanotaeniidae).

The development of the olfactory organ in the rainbow fish, Nematocentris maccullochi, was studied using scanning and transmission electron microscopy; it was compared with the developmental process in other teleosts, especially in the closely related atherinids and cyprinodonts. The formation of the nares parallels that in atherinids, salmonids, cyprinids and heterosomats, but differs from that found in cyprinodonts. Another ontogenetic feature in which the olfactory organs of the rainbow fish and also of atherinids differ from those of cyprinodonts, is the occurrence of transitory kinociliary cells which disappear during the postlarval period. The divergent evolutionary pathways are discussed with reference to experimental investigations. During development, ciliated and microvillous receptor cell types occur. At the primary larval stage ciliated receptor neurons are exclusively present. At a later stage the microvillous type develops and becomes equal in frequency. Thus, the microvillous receptor represents a separate type of olfactory neuron and is not a progenitor of the ciliated receptor cell.

Animals↗
PubMed1978

Scanning electron microscopy of the channel catfish olfactory lamellae.

The olfactory lamellae of the channel catfish (Ictalurus punctatus) are composed of sensory and indifferent (non-sensory) epithelia organized into two distinct regions on both surfaces of each lamella. The smaller sensory region located adjacent to the midline raphe has fewer cilia per unit surface area than the indifferent epithelium and contains the olfactory neurons whose ciliated dendritic terminals occur at the epithelial surface. The indifferent epithelium, comprising the greater surface area of the olfactory lamella, is covered with a dense mat of non-sensory cilia. Fractured carbon dioxide critical point dried lamellar tissue revealed the underlying cellular structure. The lamellae are composed of two layers of epithelium enclosing a thin stromal layer. Olfactory receptors were observed in the fractured tissue only within the sensory epithelium.

Animals↗
PubMed1978

Physiological roles of adenosine derivatives which are released during neurotransmission in mammalian brain.

1. Experiments using synaptosome beds suggested that ATP was released from presynaptic sites and degraded to adenosine in the synaptic cleft and that the resulting adenosine was taken up again into nerve endings where it was re-phosphorylated to ATP. 2. Adenosine derivatives in the synaptic cleft inhibited the postsynaptic potentials in olfactory cortex slices in vitro, presumably by the inhibition of Ca2+ influx into nerve endings which resulted in the reduction of transmitter release. 3. The adenosine derivatives also increased the level of cyclic AMP in the slices under the same conditions as above. 4. Although the nature of the "adenosine receptors" for both functions was remarkably similar, the increase of cyclic AMP did not mediate the inhibitory action, but the presynaptic increase of cyclic AMP induced by adenosine derivatives might mediate the facilitation observed in the olfactory cortex. 5. Possible physiological roles of extracellular adenosine derivatives in mammalian brain were classified, at different sites of action around the synapses, with different time courses and modes of action, directly or via the increase of intracellular cyclic AMP.

Adenine Nucleotides↗
PubMed2024

NAD activates olfactory receptor 1386 to regulate type I interferon responses in Plasmodium yoelii YM infection.

Olfactory receptors (Olfr) are G protein-coupled receptors that are normally expressed on olfactory sensory neurons to detect volatile chemicals or odorants. Interestingly, many Olfrs are also expressed in diverse tissues and function in cell-cell recognition, migration, and proliferation as well as immune responses and disease processes. Here, we showed that many Olfr genes were expressed in the mouse spleen, linked to Plasmodium yoelii genetic loci significantly, and/or had genome-wide patterns of LOD scores (GPLSs) similar to those of host Toll-like receptor genes. Expression of specific Olfr genes such as Olfr1386 in HEK293T cells significantly increased luciferase signals driven by IFN-β and NF-κB promoters, with elevated levels of phosphorylated TBK1, IRF3, P38, and JNK. Mice without Olfr1386 were generated using the CRISPR/Cas9 method, and the Olfr1386-/- mice showed significantly lower IFN-α/β levels and longer survival than wild-type (WT) littermates after infection with P. yoelii YM parasites. Inhibition of G protein signaling and P38 activity could affect cyclic AMP-responsive element promoter-driven luciferase signals and IFN-β mRNA levels in HEK293T cells expressing the Olfr1386 gene, respectively. Screening of malaria parasite metabolites identified nicotinamide adenine dinucleotide (NAD) as a potential ligand for Olfr1386, and NAD could stimulate IFN-β responses and phosphorylation of TBK1 and STAT1/2 in RAW264.7 cells. Additionally, parasite RNA (pRNA) could significantly increase Olfr1386 mRNA levels. This study links multiple Olfrs to host immune response pathways, identifies a candidate ligand for Olfr1386, and demonstrates the important roles of Olfr1386 in regulating type I interferon (IFN-I) responses during malaria parasite infections.

Animals↗
PubMed1975

[Ultrastructure of the olfactory epithelium of the rat: polymorphism of the receptors].

The olfactory epithelium of the Rat is studied by transmission electron microscopy. Two types of bipolar sensory cells are described. One (A type) is homologous to the receptors already described in vertebrates. The other (B type) is less frequently found and shows different morphological characteristics. Another peculiar epithelial cell-type (C type) was occasionally observed.

Animals↗
PubMed2025

An integrated anatomical, functional and evolutionary view of the Drosophila olfactory system.

The Drosophila melanogaster olfactory system is one of the most intensively studied parts of the nervous system in any animal. Composed of ~60 independent olfactory neuron classes, with several associated hygrosensory and thermosensory pathways, it has been subject to diverse types of experimental analyses. However, synthesizing the available data is limited by the incompleteness and inconsistent nomenclature found in the literature. In this work, we first "complete" the peripheral sensory map through the identification of a previously uncharacterized antennal sensory neuron population expressing Or46aB, and the definition of an exceptional "hybrid" olfactory neuron class comprising functional Or and Ir receptors. Second, we survey developmental, anatomical, connectomic, functional and evolutionary studies to generate an integrated dataset of these sensory neuron pathways - and associated visualizations - creating an unprecedented comprehensive resource. Third, we illustrate the utility of the dataset to reveal relationships between different organizational properties of this sensory system, and the new questions these stimulate. These examples emphasize the power of this resource to promote further understanding of the construction, function and evolution of these neural circuits.

Journal Article↗
PubMed1978

Replacement of receptor neurones after section of the vomeronasal nerves in the adult mouse.

Eight days after vomeronasal nerve section or removal of the accessory olfactory bulb, the majority of receptor cells of the vomeronasal neuroepithelium degenerate and disappear, leaving a regular framework consisting of supporting cells and their radial processes. The cell clusters at the boundaries of the epithelial sheet (which have been shown to be actively dividing in the normal, unoperated adult mouse) are also spared. The epithelium is subsequently repopulated by receptor cells appearing first in the basal part of the receptor cell layer and later occupying the full width of the receptor layer. These cells are anatomically fully differentiated receptor cells with normal sensory dendrites. Their axons form conspicuous intraepithelial neuromatous masses. Administration of [3H]thymidine on days 10-20 postoperatively labels some clusters of supporting cells and virtually all of the receptor cells, indicating that the repopulation of the epithelium is due to new formation of receptor cells.

Animals↗
PubMed1978

Unitary recordings of near threshold responses of receptor cells in the olfactory mucosa of the frog.

1. Receptor cell activity in the frog's eminentia olfactoria was recorded using metal-filled micro-electrodes. 2. Several units discharged spontaneously with a mean frequency lower than 0.2 spikes per sec, or were silent in periods of up to 5 min. The other units displayed spontaneous activities between 0.2 and 1.05 spikes per sec; their activity could be modelled with a Poisson process. 3. Near-threshold responses to odour stimulation were investigated, considering several stimulations within a small concentration range. Low concentration stimulations were sometimes followed by a response, sometimes not. The concept of response probability is introduced to describe this incertitude. 4. The distribution of the number of spikes in several odour trials at low concentrations showed a reasonable agreement with two types of Poisson distribution. 5. The findings are discussed in connexion with receptor cell sensitivity and the excitation of second order neurones in the bulb.

Action Potentials↗
PubMed1977

Mesolimbic dopamine neurons: effects of 6-hydroxydopamine-induced destruction and receptor blockade on drug-induced rotation of rats.

Bilateral injections of 6-hydroxydopamine (6-OHDA) into the nucleus accumbens greatly reduced the dopamine content of this nucleus and the olfactory tubercle and blocked the ipsilateral rotation induced by amphetamine and methamphetamine in rats with unilateral 6-OHDA lesions of the caudate nucleus. In contrast, apomorphine-induced contralateral rotation was enhanced. Similar results were obtained when the destruction of forebrain noradrenergic neurons, normally produced by the nucleus accumbens 6-OHDA lesion, was prevented by desipramine (DMI) pretreatment. Microinjections of the dopamine receptor antagonist heloperidol into the nucleus accumbens did not spread to the olfactory tubercle, as assessed by the distribution of 3H-haloperidol, and blocked circling induced by amphetamine and apomorphine. Amphetamine-induced circling was less effectively blocked by haloperidol injected into the olfactory tubercle. These results suggest that activity at nucleus accumbens dopamine receptors can greatly affect circling behavior, perhaps by amplifying asymmetries of nigrostriatal activity.

Amphetamine↗
PubMed1976

Spatial patterning of response to odors in the peripheral olfactory system.

The low odor specificities of the olfactory receptors suggest that odor recognition depends on the simultaneous activity in an ensemble of receptor neurons. This ensemble could conceivably code quality without reference to the point of origin of each input on the receptor sheet. However, the nose-to-bulb projection appears sufficiently precise to provide the bulb with a topographical map of the receptor sheet although it is poorly delineated in the anteroposterior plane. (It is also known that the morphological changes that follow prolonged exposure to odors are more differentiated in the coronal than in the anteroposterior plane.) Furthermore, it is clear from work at both epithelial and bulbar levels that a spatiotemporal pattern of excitation is generated by odor stimulation of the receptor sheet and that this pattern differs for different odors. This evidence, then, supports the view that there is a spatial component to odor quality coding. This spatial pattern has two elements. One is imposed and depends (at least in part) on differences in the retentivity of different odorants by the mucous sheet, which has powerful sorptive properties. It effectiveness seems particularly weak for odorants with relatively long retention times. The second component is inherent and depends on the tendency of receptors with similar peak odor specificities to aggregate in the same region (or regions) of the epithelium. Different odors or groups of odors maximally excite different regions, which may overlap. The imposed component could not, in itself, provide an adequate mechanism for odor recognition, partly because many compounds have comparable or even identical mean retention times (e.g., enantiomeric isomers). The inherent component, on the other hand, possesses this potential. However, either or both forms of patterning may cooperate with a third nonspatial mechanism (based on differential responsiveness of receptors to different odors) in coding odor quality.

Animals↗