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Raja R, Dumontier E, Phen A, Cloutier JF. Insertion of a neomycin selection cassette in the Amigo1 locus alters gene expression in the olfactory epithelium leading to region-specific defects in olfactory receptor neuron development. Genesis 2024; 62:e23594. [PMID: 38590146 DOI: 10.1002/dvg.23594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 03/08/2024] [Accepted: 03/18/2024] [Indexed: 04/10/2024]
Abstract
During development of the nervous system, neurons connect to one another in a precisely organized manner. Sensory systems provide a good example of this organization, whereby the composition of the outside world is represented in the brain by neuronal maps. Establishing correct patterns of neural circuitry is crucial, as inaccurate map formation can lead to severe disruptions in sensory processing. In rodents, olfactory stimuli modulate a wide variety of behaviors essential for survival. The formation of the olfactory glomerular map is dependent on molecular cues that guide olfactory receptor neuron axons to broad regions of the olfactory bulb and on cell adhesion molecules that promote axonal sorting into specific synaptic units in this structure. Here, we demonstrate that the cell adhesion molecule Amigo1 is expressed in a subpopulation of olfactory receptor neurons, and we investigate its role in the precise targeting of olfactory receptor neuron axons to the olfactory bulb using a genetic loss-of-function approach in mice. While ablation of Amigo1 did not lead to alterations in olfactory sensory neuron axonal targeting, our experiments revealed that the presence of a neomycin resistance selection cassette in the Amigo1 locus can lead to off-target effects that are not due to loss of Amigo1 expression, including unexpected altered gene expression in olfactory receptor neurons and reduced glomerular size in the ventral region of the olfactory bulb. Our results demonstrate that insertion of a neomycin selection cassette into the mouse genome can have specific deleterious effects on the development of the olfactory system and highlight the importance of removing antibiotic resistance cassettes from genetic loss-of-function mouse models when studying olfactory system development.
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Affiliation(s)
- Reesha Raja
- The Neuro (Montreal Neurological Institute-Hospital), Montréal, Québec, Canada
- Integrated Program in Neuroscience, McGill University, Montréal, Québec, Canada
| | - Emilie Dumontier
- The Neuro (Montreal Neurological Institute-Hospital), Montréal, Québec, Canada
| | - Alina Phen
- The Neuro (Montreal Neurological Institute-Hospital), Montréal, Québec, Canada
| | - Jean-François Cloutier
- The Neuro (Montreal Neurological Institute-Hospital), Montréal, Québec, Canada
- Integrated Program in Neuroscience, McGill University, Montréal, Québec, Canada
- Department of Neurology and Neurosurgery, McGill University, Montréal, Québec, Canada
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2
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Hirota J. Molecular mechanisms of differentiation and class choice of olfactory sensory neurons. Genesis 2024; 62:e23587. [PMID: 38454646 DOI: 10.1002/dvg.23587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 01/10/2024] [Accepted: 01/29/2024] [Indexed: 03/09/2024]
Abstract
The sense of smell is intricately linked to essential animal behaviors necessary for individual survival and species preservation. During vertebrate evolution, odorant receptors (ORs), responsible for detecting odor molecules, have evolved to adapt to changing environments, transitioning from aquatic to terrestrial habitats and accommodating increasing complex chemical environments. These evolutionary pressures have given rise to the largest gene family in vertebrate genomes. Vertebrate ORs are phylogenetically divided into two major classes; class I and class II. Class I OR genes, initially identified in fish and frog, have persisted across vertebrate species. On the other hand, class II OR genes are unique to terrestrial animals, accounting for ~90% of mammalian OR genes. In mice, each olfactory sensory neuron (OSN) expresses a single functional allele of a single OR gene from either the class I or class II OR repertoire. This one neuron-one receptor rule is established through two sequential steps: specification of OR class and subsequent exclusive OR expression from the corresponding OR class. Consequently, OSNs acquire diverse neuronal identities during the process of OSN differentiation, enabling animals to detect a wide array of odor molecules. This review provides an overview of the OSN differentiation process through which OSN diversity is achieved, primarily using the mouse as a model animal.
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Affiliation(s)
- Junji Hirota
- Department of Life Science and Technology, Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
- Center for Integrative Biosciences, Tokyo Institute of Technology, Yokohama, Japan
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3
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Hossain K, Smith M, Santoro SW. In mice, discrete odors can selectively promote the neurogenesis of sensory neuron subtypes that they stimulate. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.10.579748. [PMID: 38405728 PMCID: PMC10888860 DOI: 10.1101/2024.02.10.579748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
In mammals, olfactory sensory neurons (OSNs) are born throughout life, presumably solely to replace neurons lost via turnover or injury. This assumption follows from the hypothesis that olfactory neurogenesis is strictly stochastic with respect to neuron subtype, as defined by the single odorant receptor allele that each neural precursor stochastically chooses out of hundreds of possibilities. This hypothesis is challenged by recent findings that the birthrates of a fraction of subtypes are selectively diminished by olfactory deprivation. These findings raise questions about how, and why, olfactory stimuli are required to promote the neurogenesis of some OSN subtypes, including whether the stimuli are generic (e.g., broadly activating odors or mechanical stimuli) or specific (e.g., discrete odorants). Based on RNA-seq and scRNA-seq analyses, we hypothesized that the neurogenic stimuli are specific odorants that selectively activate the same OSN subtypes whose birthrates are accelerated. In support of this, we have found, using subtype-specific OSN birthdating, that exposure to male and musk odors can accelerate the birthrates of responsive OSNs. Collectively, our findings reveal that certain odor experiences can selectively "amplify" specific OSN subtypes, and that persistent OSN neurogenesis may serve, in part, an adaptive function.
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Affiliation(s)
- Kawsar Hossain
- Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Madeline Smith
- Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Stephen W Santoro
- Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
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4
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Hossain K, Smith M, Santoro SW. A histological protocol for quantifying the birthrates of specific subtypes of olfactory sensory neurons in mice. STAR Protoc 2023; 4:102432. [PMID: 37436902 PMCID: PMC10511921 DOI: 10.1016/j.xpro.2023.102432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/16/2023] [Accepted: 06/12/2023] [Indexed: 07/14/2023] Open
Abstract
Mammals typically have hundreds of distinct olfactory sensory neuron subtypes, each defined by expression of a specific odorant receptor gene, which undergo neurogenesis throughout life at rates that can depend on olfactory experience. Here, we present a protocol to quantify the birthrates of specific neuron subtypes via the simultaneous detection of corresponding receptor mRNAs and 5-ethynyl-2'-deoxyuridine. For preparation prior to beginning the protocol, we detail procedures for generating odorant receptor-specific riboprobes and experimental mouse olfactory epithelial tissue sections. For complete details on the use and execution of this protocol, please refer to van der Linden et al. (2020).1.
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Affiliation(s)
- Kawsar Hossain
- Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA; Molecular and Cellular Life Sciences Program, University of Wyoming, Laramie, WY 82071, USA
| | - Madeline Smith
- Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Stephen W Santoro
- Department of Pediatrics, Section of Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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5
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Breau MA, Trembleau A. Chemical and mechanical control of axon fasciculation and defasciculation. Semin Cell Dev Biol 2023; 140:72-81. [PMID: 35810068 DOI: 10.1016/j.semcdb.2022.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 06/14/2022] [Accepted: 06/21/2022] [Indexed: 01/28/2023]
Abstract
Neural networks are constructed through the development of robust axonal projections from individual neurons, which ultimately establish connections with their targets. In most animals, developing axons assemble in bundles to navigate collectively across various areas within the central nervous system or the periphery, before they separate from these bundles in order to find their specific targets. These processes, called fasciculation and defasciculation respectively, were thought for many years to be controlled chemically: while guidance cues may attract or repulse axonal growth cones, adhesion molecules expressed at the surface of axons mediate their fasciculation. Recently, an additional non-chemical parameter, the mechanical longitudinal tension of axons, turned out to play a role in axon fasciculation and defasciculation, through zippering and unzippering of axon shafts. In this review, we present an integrated view of the currently known chemical and mechanical control of axon:axon dynamic interactions. We highlight the facts that the decision to cross or not to cross another axon depends on a combination of chemical, mechanical and geometrical parameters, and that the decision to fasciculate/defasciculate through zippering/unzippering relies on the balance between axon:axon adhesion and their mechanical tension. Finally, we speculate about possible functional implications of zippering-dependent axon shaft fasciculation, in the collective migration of axons, and in the sorting of subpopulations of axons.
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Affiliation(s)
- Marie Anne Breau
- Sorbonne Université, Centre National de la Recherche Scientifique (CNRS UMR 7622), Institut de Biologie Paris Seine (IBPS), Developmental Biology Laboratory, Paris, France
| | - Alain Trembleau
- Sorbonne Université, Centre National de la Recherche Scientifique (CNRS UMR8246), Inserm U1130, Institut de Biologie Paris Seine (IBPS), Neuroscience Paris Seine (NPS), Paris, France.
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6
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Fukuda N, Fukuda T, Percipalle P, Oda K, Takei N, Czaplinski K, Touhara K, Yoshihara Y, Sasaoka T. Axonal mRNA binding of hnRNP A/B is crucial for axon targeting and maturation of olfactory sensory neurons. Cell Rep 2023; 42:112398. [PMID: 37083330 DOI: 10.1016/j.celrep.2023.112398] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 01/26/2023] [Accepted: 03/29/2023] [Indexed: 04/22/2023] Open
Abstract
Spatiotemporal control of gene expression is important for neural development and function. Here, we show that heterogeneous nuclear ribonucleoprotein (hnRNP) A/B is highly expressed in developing olfactory sensory neurons (OSNs), and its knockout results in reduction in mature OSNs and aberrant targeting of OSN axons to the olfactory bulb. RNA immunoprecipitation analysis reveals that hnRNP A/B binds to a group of mRNAs that are highly related to axon projections and synapse assembly. Approximately 11% of the identified hnRNP A/B targets, including Pcdha and Ncam2, encode cell adhesion molecules. In Hnrnpab knockout mice, PCDHA and NCAM2 levels are significantly reduced at the axon terminals of OSNs. Furthermore, deletion of the hnRNP A/B-recognition motif in the 3' UTR of Pcdha leads to impaired PCDHA expression at the OSN axon terminals. Therefore, we propose that hnRNP A/B facilitates OSN maturation and axon projection by regulating the local expression of its target genes at axon terminals.
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Affiliation(s)
- Nanaho Fukuda
- Brain Research Institute, Niigata University, Niigata 951-8585, Japan; Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma 630-0192, Japan.
| | - Tomoyuki Fukuda
- Niigata University Graduate School of Medical and Dental Science, Niigata 951-8510, Japan
| | - Piergiorgio Percipalle
- Science Division, Biology Program, New York University Abu Dhabi, Abu Dhabi 129188, UAE; Department of Molecular Bioscience, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden
| | - Kanako Oda
- Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Nobuyuki Takei
- Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | | | - Kazushige Touhara
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | | | - Toshikuni Sasaoka
- Brain Research Institute, Niigata University, Niigata 951-8585, Japan
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7
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Habif JC, Xie C, de Celis C, Ukhanov K, Green WW, Moretta JC, Zhang L, Campbell RJ, Martens JR. The role of a ciliary GTPase in the regulation of neuronal maturation of olfactory sensory neurons. Development 2023; 150:286702. [PMID: 36661357 PMCID: PMC10110495 DOI: 10.1242/dev.201116] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 12/19/2022] [Indexed: 01/20/2023]
Abstract
Olfactory sensory neurons (OSNs) form embryonically and mature perinatally, innervating glomeruli and extending dendrites with multiple cilia. This process and its timing are crucial for odor detection and perception and continues throughout life. In the olfactory epithelium (OE), differentiated OSNs proceed from an immature (iOSN) to a mature (mOSN) state through well-defined sequential morphological and molecular transitions, but the precise mechanisms controlling OSN maturation remain largely unknown. We have identified that a GTPase, ARL13B, has a transient and maturation state-dependent expression in OSNs marking the emergence of a primary cilium. Utilizing an iOSN-specific Arl13b-null murine model, we examined the role of ARL13B in the maturation of OSNs. The loss of Arl13b in iOSNs caused a profound dysregulation of the cellular homeostasis and development of the OE. Importantly, Arl13b null OSNs demonstrated a delay in the timing of their maturation. Finally, the loss of Arl13b resulted in severe deformation in the structure and innervation of glomeruli. Our findings demonstrate a previously unknown role of ARL13B in the maturation of OSNs and development of the OE.
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Affiliation(s)
- Julien C Habif
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
| | - Chao Xie
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
| | - Carlos de Celis
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
| | - Kirill Ukhanov
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
| | - Warren W Green
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
| | - Jordan C Moretta
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
| | - Lian Zhang
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
| | - Robert J Campbell
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
| | - Jeffrey R Martens
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA
- University of Florida Center for Smell and Taste, Gainesville, FL 32610, USA
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8
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Huang JS, Kunkhyen T, Rangel AN, Brechbill TR, Gregory JD, Winson-Bushby ED, Liu B, Avon JT, Muggleton RJ, Cheetham CEJ. Immature olfactory sensory neurons provide behaviourally relevant sensory input to the olfactory bulb. Nat Commun 2022; 13:6194. [PMID: 36261441 PMCID: PMC9582225 DOI: 10.1038/s41467-022-33967-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 10/07/2022] [Indexed: 01/12/2023] Open
Abstract
Postnatal neurogenesis provides an opportunity to understand how newborn neurons integrate into circuits to restore function. Newborn olfactory sensory neurons (OSNs) wire into highly organized olfactory bulb (OB) circuits throughout life, enabling lifelong plasticity and regeneration. Immature OSNs form functional synapses capable of evoking firing in OB projection neurons but what contribution, if any, they make to odor processing is unknown. Here, we show that immature OSNs provide odor input to the mouse OB, where they form monosynaptic connections with excitatory neurons. Importantly, immature OSNs respond as selectively to odorants as mature OSNs and exhibit graded responses across a wider range of odorant concentrations than mature OSNs, suggesting that immature and mature OSNs provide distinct odor input streams. Furthermore, mice can successfully perform odor detection and discrimination tasks using sensory input from immature OSNs alone. Together, our findings suggest that immature OSNs play a previously unappreciated role in olfactory-guided behavior.
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Affiliation(s)
- Jane S Huang
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
| | - Tenzin Kunkhyen
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
| | - Alexander N Rangel
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
| | - Taryn R Brechbill
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
| | - Jordan D Gregory
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
| | - Emily D Winson-Bushby
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
| | - Beichen Liu
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
- Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA, 15213, USA
| | - Jonathan T Avon
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
| | - Ryan J Muggleton
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA
- Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA, 15213, USA
| | - Claire E J Cheetham
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA, 15232, USA.
- Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA, 15213, USA.
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9
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Gaun V, Martens JR, Schwob JE. Lifespan of mature olfactory sensory neurons varies with location in the mouse olfactory epithelium and age of the animal. J Comp Neurol 2022; 530:2238-2251. [PMID: 35434783 PMCID: PMC9233066 DOI: 10.1002/cne.25330] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 03/23/2022] [Accepted: 03/28/2022] [Indexed: 08/03/2023]
Abstract
The olfactory sensory neurons (OSNs) of the olfactory epithelium (OE) exhibit a remarkable regenerative capability, which protects the population against environmental insult and enables adjustment to new odors. The lifespan of OSNs is still open to question, with estimates ranging from 1 month to at least 1 year. However, the estimates come with some caveats, including low labeling efficiency and a focus solely on newborn neurons. We revisited the issue via the use of OMP-tTA; TetO-Cre; Rosa26-fl(stop)-Tdtomato (OMP-tTA;TdT) mice, which allowed us to selectively label ∼95% of the OMP(+) OSN population that reach maturity by a given time and, by switching to doxycycline chow, to "chase" this preexisting OSN population. Two loading protocols were used: conception to 2 months old and conception to 4.5 months old. Surviving OSNs were common up to 6 months chase time in both groups, but more neurons survived when loading for 4.5 months as compared with 2 months. A spatial difference was evident: higher percentages of OSNs survived in the dorsomedial OE as compared with ventrolateral and in posterior versus anterior OE regions. Finally, proliferation rates anticorrelated with the spatial differences in OSN survival; higher proliferation rates were observed ventrally. Together, these results demonstrate spatial and temporal differences in OSN survival, highlighting it as a dynamic system that can be studied for factors affecting neuronal survival.
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Affiliation(s)
- Vera Gaun
- Program in Cellular, Molecular and Developmental Biology, Graduate School of Biomedical Sciences and Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA
| | - Jeffrey R. Martens
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine and Center for Smell and Taste, University of Florida College of Medicine, Gainesville, FL
| | - James E. Schwob
- Program in Cellular, Molecular and Developmental Biology, Graduate School of Biomedical Sciences and Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA
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10
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When is a neuron like an epithelial cell. Dev Biol 2022; 489:161-164. [DOI: 10.1016/j.ydbio.2022.06.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 06/18/2022] [Indexed: 11/30/2022]
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11
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Ching K, Wang JT, Stearns T. Long-range migration of centrioles to the apical surface of the olfactory epithelium. eLife 2022; 11:e74399. [PMID: 35420544 PMCID: PMC9064291 DOI: 10.7554/elife.74399] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 04/13/2022] [Indexed: 02/07/2023] Open
Abstract
Olfactory sensory neurons (OSNs) in vertebrates detect odorants using multiple cilia, which protrude from the end of the dendrite and require centrioles for their formation. In mouse olfactory epithelium, the centrioles originate in progenitor cells near the basal lamina, often 50-100 μm from the apical surface. It is unknown how centrioles traverse this distance or mature to form cilia. Using high-resolution expansion microscopy, we found that centrioles migrate together, with multiple centrioles per group and multiple groups per OSN, during dendrite outgrowth. Centrioles were found by live imaging to migrate slowly, with a maximum rate of 0.18 µm/minute. Centrioles in migrating groups were associated with microtubule nucleation factors, but acquired rootletin and appendages only in mature OSNs. The parental centriole had preexisting appendages, formed a single cilium before other centrioles, and retained its unique appendage configuration in the mature OSN. We developed an air-liquid interface explant culture system for OSNs and used it to show that centriole migration can be perturbed ex vivo by stabilizing microtubules. We consider these results in the context of a comprehensive model for centriole formation, migration, and maturation in this important sensory cell type.
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Affiliation(s)
- Kaitlin Ching
- Department of Biology, Stanford UniversityStanfordUnited States
| | - Jennifer T Wang
- Department of Biology, Stanford UniversityStanfordUnited States
| | - Tim Stearns
- Department of Biology, Stanford UniversityStanfordUnited States
- Department of Genetics, Stanford University School of MedicineStanfordUnited States
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12
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Hu B, Zhang J, Gong M, Deng Y, Cao Y, Xiang Y, Ye D. Research Progress of Olfactory Nerve Regeneration Mechanism and Olfactory Training. Ther Clin Risk Manag 2022; 18:185-195. [PMID: 35281777 PMCID: PMC8906848 DOI: 10.2147/tcrm.s354695] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 02/28/2022] [Indexed: 11/24/2022] Open
Abstract
The olfactory nerve (ON) is the only cranial nerve exposed to the external environment. Hence, it is susceptible to damage from head trauma, viral infection, inflammatory stimulation, and chemical toxins, which can lead to olfactory dysfunction. However, compared with all other cranial nerves, the ON is unique due to its inherent ability to regenerate. This characteristic provides a theoretical basis for treatment of olfactory dysfunction. Olfactory training (OT) is one of the main treatments for olfactory dysfunction. It is easy to apply and has few side-effects, and has been shown to be efficacious for patients with olfactory dysfunction of various causes. To further understand the application value of ON regeneration and OT on olfactory dysfunction, we review the research progress on the mechanism of ON regeneration and OT.
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Affiliation(s)
- Bian Hu
- Department of Otorhinolaryngology-Head and Neck Surgery, Lihuili Hospital of Ningbo University, Ningbo, 315040, Zhejiang, People’s Republic of China
- Department of Otorhinolaryngology-Head and Neck Surgery, Ninghai First Hospital, Ningbo, 315699, Zhejiang, People’s Republic of China
| | - Jingyu Zhang
- Shanghai Jiao Tong University, Shanghai, 200030, People’s Republic of China
| | - Mengdan Gong
- Department of Otorhinolaryngology-Head and Neck Surgery, Lihuili Hospital of Ningbo University, Ningbo, 315040, Zhejiang, People’s Republic of China
| | - Yongqin Deng
- Department of Otorhinolaryngology-Head and Neck Surgery, Lihuili Hospital of Ningbo University, Ningbo, 315040, Zhejiang, People’s Republic of China
| | - Yujie Cao
- Department of Otorhinolaryngology-Head and Neck Surgery, Lihuili Hospital of Ningbo University, Ningbo, 315040, Zhejiang, People’s Republic of China
| | - Yizhen Xiang
- Department of Otorhinolaryngology-Head and Neck Surgery, Lihuili Hospital of Ningbo University, Ningbo, 315040, Zhejiang, People’s Republic of China
| | - Dong Ye
- Department of Otorhinolaryngology-Head and Neck Surgery, Lihuili Hospital of Ningbo University, Ningbo, 315040, Zhejiang, People’s Republic of China
- Correspondence: Dong Ye, Department of Otorhinolaryngology-Head and Neck Surgery, Lihuili Hospital of Ningbo University, Ningbo, 315040, Zhejiang, People’s Republic of China, Tel +86 13819861213, Fax +86 574-87392232, Email
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13
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Wang J, Vaddadi N, Pak JS, Park Y, Quilez S, Roman CA, Dumontier E, Thornton JW, Cloutier JF, Özkan E. Molecular and structural basis of olfactory sensory neuron axon coalescence by Kirrel receptors. Cell Rep 2021; 37:109940. [PMID: 34731636 PMCID: PMC8628261 DOI: 10.1016/j.celrep.2021.109940] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 07/30/2021] [Accepted: 10/13/2021] [Indexed: 01/21/2023] Open
Abstract
Projections from sensory neurons of olfactory systems coalesce into glomeruli in the brain. The Kirrel receptors are believed to homodimerize via their ectodomains and help separate sensory neuron axons into Kirrel2- or Kirrel3-expressing glomeruli. Here, we present the crystal structures of homodimeric Kirrel receptors and show that the closely related Kirrel2 and Kirrel3 have evolved specific sets of polar and hydrophobic interactions, respectively, disallowing heterodimerization while preserving homodimerization, likely resulting in proper segregation and coalescence of Kirrel-expressing axons into glomeruli. We show that the dimerization interface at the N-terminal immunoglobulin (IG) domains is necessary and sufficient to create homodimers and fail to find evidence for a secondary interaction site in Kirrel ectodomains. Furthermore, we show that abolishing dimerization of Kirrel3 in vivo leads to improper formation of glomeruli in the mouse accessory olfactory bulb as observed in Kirrel3-/- animals. Our results provide evidence for Kirrel3 homodimerization controlling axonal coalescence.
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Affiliation(s)
- Jing Wang
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Neelima Vaddadi
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada
| | - Joseph S Pak
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Yeonwoo Park
- Committee on Genetics, Genomics and Systems Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Sabrina Quilez
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada
| | - Christina A Roman
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Emilie Dumontier
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Joseph W Thornton
- Committee on Genetics, Genomics and Systems Biology, The University of Chicago, Chicago, IL 60637, USA; Department of Human Genetics, The University of Chicago, Chicago, IL 60637, USA; Department of Ecology and Evolution, The University of Chicago, Chicago, IL 60637, USA
| | - Jean-François Cloutier
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada; Department of Anatomy and Cell Biology, McGill University, Montréal, QC H3A 0C7, Canada.
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA.
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14
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AlMatrouk A, Lemons K, Ogura T, Lin W. Modification of the Peripheral Olfactory System by Electronic Cigarettes. Compr Physiol 2021; 11:2621-2644. [PMID: 34661289 DOI: 10.1002/cphy.c210007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Electronic cigarettes (e-cigs) are used by millions of adolescents and adults worldwide. Commercial e-liquids typically contain flavorants, propylene glycol, and vegetable glycerin with or without nicotine. These chemical constituents are detected and evaluated by chemosensory systems to guide and modulate vaping behavior and product choices of e-cig users. The flavorants in e-liquids are marketing tools. They evoke sensory percepts of appealing flavors through activation of chemical sensory systems to promote the initiation and sustained use of e-cigs. The vast majority of flavorants in e-liquids are volatile odorants, and as such, the olfactory system plays a dominant role in perceiving these molecules that enter the nasal cavity either orthonasally or retronasally during vaping. In addition to flavorants, e-cig aerosol contains a variety of by-products generated through heating the e-liquids, including odorous irritants, toxicants, and heavy metals. These harmful substances can directly and adversely impact the main olfactory epithelium (MOE). In this article, we first discuss the olfactory contribution to e-cig flavor perception. We then provide information on MOE cell types and their major functions in olfaction and epithelial maintenance. Olfactory detection of flavorants, nicotine, and odorous irritants and toxicants are also discussed. Finally, we discuss the cumulated data on modification of the MOE by flavorant exposure and toxicological impacts of formaldehyde, acrolein, and heavy metals. Together, the information presented in this overview may provide insight into how e-cig exposure may modify the olfactory system and adversely impact human health through the alteration of the chemosensory factor driving e-cig use behavior and product selections. © 2021 American Physiological Society. Compr Physiol 11:2621-2644, 2021.
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Affiliation(s)
- Abdullah AlMatrouk
- General Department of Criminal Evidence, Forensic Laboratories, Ministry of Interior, Farwaniyah, Kuwait.,Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland, USA
| | - Kayla Lemons
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, North Carolina, USA.,Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland, USA
| | - Tatsuya Ogura
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland, USA
| | - Weihong Lin
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland, USA
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15
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Olfactory Stimulation Regulates the Birth of Neurons That Express Specific Odorant Receptors. Cell Rep 2021; 33:108210. [PMID: 33027656 PMCID: PMC7569022 DOI: 10.1016/j.celrep.2020.108210] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 07/03/2020] [Accepted: 09/09/2020] [Indexed: 12/18/2022] Open
Abstract
In mammals, olfactory sensory neurons (OSNs) are born throughout life, ostensibly solely to replace damaged OSNs. During differentiation, each OSN precursor “chooses,” out of hundreds of possibilities, a single odorant receptor (OR) gene, which defines the identity of the mature OSN. The relative neurogenesis rates of the hundreds of distinct OSN “subtypes” are thought to be constant, as they are determined by a stochastic process in which each OR is chosen with a fixed probability. Here, using histological, single-cell, and targeted affinity purification approaches, we show that closing one nostril in mice selectively reduces the number of newly generated OSNs of specific subtypes. Moreover, these reductions depend on an animal’s age and/or environment. Stimulation-dependent changes in the number of new OSNs are not attributable to altered rates of cell survival but rather production. Our findings indicate that the relative birth rates of distinct OSN subtypes depend on olfactory experience. In mammals, the odorant receptor identities of newly generated olfactory sensory neurons are thought to be determined by each progenitor cell’s random choice of a single receptor. Here, van der Linden et al. show that, in mice, the birth rates of neurons expressing a subset of receptors depend on olfactory stimulation.
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16
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Bloom ML, Johnston LB, Datta SR. Renewal and Differentiation of GCD Necklace Olfactory Sensory Neurons. Chem Senses 2021; 45:333-346. [PMID: 32333759 DOI: 10.1093/chemse/bjaa027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Both canonical olfactory sensory neurons (OSNs) and sensory neurons belonging to the guanylate cyclase D (GCD) "necklace" subsystem are housed in the main olfactory epithelium, which is continuously bombarded by toxins, pathogens, and debris from the outside world. Canonical OSNs address this challenge, in part, by undergoing renewal through neurogenesis; however, it is not clear whether GCD OSNs also continuously regenerate and, if so, whether newborn GCD precursors follow a similar developmental trajectory to that taken by canonical OSNs. Here, we demonstrate that GCD OSNs are born throughout adulthood and can persist in the epithelium for several months. Phosphodiesterase 2A is upregulated early in the differentiation process, followed by the sequential downregulation of β-tubulin and the upregulation of CART protein. The GCD and MS4A receptors that confer sensory responses upon GCD neurons are initially expressed midway through this process but become most highly expressed once CART levels are maximal late in GCD OSN development. GCD OSN maturation is accompanied by a horizontal migration of neurons toward the central, curved portions of the cul-de-sac regions where necklace cells are concentrated. These findings demonstrate that-like their canonical counterparts-GCD OSNs undergo continuous renewal and define a GCD-specific developmental trajectory linking neurogenesis, maturation, and migration.
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17
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Kuboki A, Kikuta S, Otori N, Kojima H, Matsumoto I, Reisert J, Yamasoba T. Insulin-Dependent Maturation of Newly Generated Olfactory Sensory Neurons after Injury. eNeuro 2021; 8:ENEURO.0168-21.2021. [PMID: 33906971 PMCID: PMC8143024 DOI: 10.1523/eneuro.0168-21.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 04/20/2021] [Indexed: 12/24/2022] Open
Abstract
Loss of olfactory sensory neurons (OSNs) after injury to the olfactory epithelium (OE) triggers the generation of OSNs that are incorporated into olfactory circuits to restore olfactory sensory perception. This study addresses how insulin receptor-mediated signaling affects the functional recovery of OSNs after OE injury. Insulin levels were reduced in mice by ablating the pancreatic β cells via streptozotocin (STZ) injections. These STZ-induced diabetic and control mice were then intraperitoneally injected with the olfactotoxic drug methimazole to selectively ablate OSNs. The OE of diabetic and control mice regenerated similarly until day 14 after injury. Thereafter, the OE of diabetic mice contained fewer mature and more apoptotic OSNs than control mice. Functionally, diabetic mice showed reduced electro-olfactogram (EOG) responses and their olfactory bulbs (OBs) had fewer c-Fos-active cells following odor stimulation, as well as performed worse in an odor-guided task compared with control mice. Insulin administered intranasally during days 8-13 after injury was sufficient to rescue recovery of OSNs in diabetic mice compared with control levels, while insulin administration between days 1 and 6 did not. During this critical time window on days 8-13 after injury, insulin receptors are highly expressed and intranasal application of an insulin receptor antagonist inhibits regeneration. Furthermore, an insulin-enriched environment could facilitate regeneration even in non-diabetic mice. These results indicate that insulin facilitates the regeneration of OSNs after injury and suggest a critical stage during recovery (8-13 d after injury) during which the maturation of newly generated OSNs is highly dependent on and promoted by insulin.
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Affiliation(s)
- Akihito Kuboki
- Department of Otolaryngology, Jikei University School of Medicine, Tokyo 105-8461, Japan
- Monell Chemical Senses Center, Philadelphia, PA 19104
| | - Shu Kikuta
- Department of Otolaryngology, Graduate School of Medicine, University of Tokyo, Tokyo 113-8655, Japan
| | - Nobuyoshi Otori
- Department of Otolaryngology, Jikei University School of Medicine, Tokyo 105-8461, Japan
| | - Hiromi Kojima
- Department of Otolaryngology, Jikei University School of Medicine, Tokyo 105-8461, Japan
| | | | | | - Tatsuya Yamasoba
- Department of Otolaryngology, Graduate School of Medicine, University of Tokyo, Tokyo 113-8655, Japan
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18
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Shepherd GM, Rowe TB, Greer CA. An Evolutionary Microcircuit Approach to the Neural Basis of High Dimensional Sensory Processing in Olfaction. Front Cell Neurosci 2021; 15:658480. [PMID: 33994949 PMCID: PMC8120314 DOI: 10.3389/fncel.2021.658480] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 03/30/2021] [Indexed: 11/16/2022] Open
Abstract
Odor stimuli consist of thousands of possible molecules, each molecule with many different properties, each property a dimension of the stimulus. Processing these high dimensional stimuli would appear to require many stages in the brain to reach odor perception, yet, in mammals, after the sensory receptors this is accomplished through only two regions, the olfactory bulb and olfactory cortex. We take a first step toward a fundamental understanding by identifying the sequence of local operations carried out by microcircuits in the pathway. Parallel research provided strong evidence that processed odor information is spatial representations of odor molecules that constitute odor images in the olfactory bulb and odor objects in olfactory cortex. Paleontology provides a unique advantage with evolutionary insights providing evidence that the basic architecture of the olfactory pathway almost from the start ∼330 million years ago (mya) has included an overwhelming input from olfactory sensory neurons combined with a large olfactory bulb and olfactory cortex to process that input, driven by olfactory receptor gene duplications. We identify a sequence of over 20 microcircuits that are involved, and expand on results of research on several microcircuits that give the best insights thus far into the nature of the high dimensional processing.
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Affiliation(s)
- Gordon M. Shepherd
- Department of Neuroscience, Yale School of Medicine, New Haven, CT, United States
| | - Timothy B. Rowe
- Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX, United States
| | - Charles A. Greer
- Department of Neuroscience, Yale School of Medicine, New Haven, CT, United States
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19
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Dibattista M, Al Koborssy D, Genovese F, Reisert J. The functional relevance of olfactory marker protein in the vertebrate olfactory system: a never-ending story. Cell Tissue Res 2021; 383:409-427. [PMID: 33447880 DOI: 10.1007/s00441-020-03349-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 11/13/2020] [Indexed: 12/12/2022]
Abstract
Olfactory marker protein (OMP) was first described as a protein expressed in olfactory receptor neurons (ORNs) in the nasal cavity. In particular, OMP, a small cytoplasmic protein, marks mature ORNs and is also expressed in the neurons of other nasal chemosensory systems: the vomeronasal organ, the septal organ of Masera, and the Grueneberg ganglion. While its expression pattern was more easily established, OMP's function remained relatively vague. To date, most of the work to understand OMP's role has been done using mice lacking OMP. This mostly phenomenological work has shown that OMP is involved in sharpening the odorant response profile and in quickening odorant response kinetics of ORNs and that it contributes to targeting of ORN axons to the olfactory bulb to refine the glomerular response map. Increasing evidence shows that OMP acts at the early stages of olfactory transduction by modulating the kinetics of cAMP, the second messenger of olfactory transduction. However, how this occurs at a mechanistic level is not understood, and it might also not be the only mechanism underlying all the changes observed in mice lacking OMP. Recently, OMP has been detected outside the nose, including the brain and other organs. Although no obvious logic has become apparent regarding the underlying commonality between nasal and extranasal expression of OMP, a broader approach to diverse cellular systems might help unravel OMP's functions and mechanisms of action inside and outside the nose.
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Affiliation(s)
- Michele Dibattista
- Department of Basic Medical Sciences, Neuroscience and Sensory Organs, University of Bari "A. Moro", Bari, Italy
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20
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Kurian SM, Naressi RG, Manoel D, Barwich AS, Malnic B, Saraiva LR. Odor coding in the mammalian olfactory epithelium. Cell Tissue Res 2021; 383:445-456. [PMID: 33409650 PMCID: PMC7873010 DOI: 10.1007/s00441-020-03327-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 10/27/2020] [Indexed: 12/31/2022]
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.
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Affiliation(s)
| | | | | | | | - Bettina Malnic
- Department of Biochemistry, University of São Paulo, São Paulo, Brazil.
| | - Luis R Saraiva
- Sidra Medicine, Doha, Qatar.
- Monell Chemical Senses Center, Philadelphia, USA.
- College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar.
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21
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Abstract
Olfactory sensory neurons (OSNs) are bipolar neurons, unusual because they turn over continuously and have a multiciliated dendrite. The extensive changes in gene expression accompanying OSN differentiation in mice are largely known, especially the transcriptional regulators responsible for altering gene expression, revealing much about how differentiation proceeds. Basal progenitor cells of the olfactory epithelium transition into nascent OSNs marked by Cxcr4 expression and the initial extension of basal and apical neurites. Nascent OSNs become immature OSNs within 24-48 h. Immature OSN differentiation requires about a week and at least 2 stages. Early-stage immature OSNs initiate expression of genes encoding key transcriptional regulators and structural proteins necessary for further neuritogenesis. Late-stage immature OSNs begin expressing genes encoding proteins important for energy production and neuronal homeostasis that carry over into mature OSNs. The transition to maturity depends on massive expression of one allele of one odorant receptor gene, and this results in expression of the last 8% of genes expressed by mature OSNs. Many of these genes encode proteins necessary for mature function of axons and synapses or for completing the elaboration of non-motile cilia, which began extending from the newly formed dendritic knobs of immature OSNs. The cilia from adjoining OSNs form a meshwork in the olfactory mucus and are the site of olfactory transduction. Immature OSNs also have a primary cilium, but its role is unknown, unlike the critical role in proliferation and differentiation played by the primary cilium of the olfactory epithelium's horizontal basal cell.
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Affiliation(s)
- Timothy S McClintock
- Department of Physiology, University of Kentucky, Lexington, KY, USA
- Correspondence to be sent to: Timothy S. McClintock, Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY 40536-0298, USA. e-mail:
| | - Naazneen Khan
- Department of Physiology, University of Kentucky, Lexington, KY, USA
| | - Chao Xie
- Department of Pharmacology and Therapeutics, and Center for Smell and Taste, University of Florida College of Medicine, Gainesville, FL, USA
| | - Jeffrey R Martens
- Department of Pharmacology and Therapeutics, and Center for Smell and Taste, University of Florida College of Medicine, Gainesville, FL, USA
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22
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Jia C, Oliver J, Gilmer D, Lovins C, Rodriguez-Gil DJ, Hagg T. Inhibition of focal adhesion kinase increases adult olfactory stem cell self-renewal and neuroregeneration through ciliary neurotrophic factor. Stem Cell Res 2020; 49:102061. [PMID: 33130470 PMCID: PMC7903807 DOI: 10.1016/j.scr.2020.102061] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 10/12/2020] [Accepted: 10/20/2020] [Indexed: 02/08/2023] Open
Abstract
Constant neuroregeneration in adult olfactory epithelium maintains olfactory function by basal stem cell proliferation and differentiation to replace lost olfactory sensory neurons (OSNs). Understanding the mechanisms regulating this process could reveal potential therapeutic targets for stimulating adult olfactory neurogenesis under pathological conditions and aging. Ciliary neurotrophic factor (CNTF) in astrocytes promotes forebrain neurogenesis but its function in the olfactory system is unknown. Here, we show in mouse olfactory epithelium that CNTF is expressed in horizontal basal cells, olfactory ensheathing cells (OECs) and a small subpopulation of OSNs. CNTF receptor alpha was expressed in Mash1-positive globose basal cells (GBCs) and OECs. Thus, CNTF may affect GBCs in a paracrine manner. CNTF−/− mice did not display altered GBC proliferation or olfactory function, suggesting that CNTF is not involved in basal olfactory renewal or that they developed compensatory mechanisms. Therefore, we tested the effect of increased CNTF in wild type mice. Intranasal instillation of a focal adhesion kinase (FAK) inhibitor, FAK14, upregulated CNTF expression. FAK14 also promoted GBC proliferation, neuronal differentiation and basal stem cell self-renewal but had no effective in CNTF−/− mice, suggesting that FAK inhibition promotes olfactory neuroregeneration through CNTF, making them potential targets to treat sensorineural anosmia due to OSN loss.
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Affiliation(s)
- Cuihong Jia
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States.
| | - Joe Oliver
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States
| | - Dustin Gilmer
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States
| | - Chiharu Lovins
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States
| | - Diego J Rodriguez-Gil
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States
| | - Theo Hagg
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States
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23
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Imamura F, Ito A, LaFever BJ. Subpopulations of Projection Neurons in the Olfactory Bulb. Front Neural Circuits 2020; 14:561822. [PMID: 32982699 PMCID: PMC7485133 DOI: 10.3389/fncir.2020.561822] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 08/12/2020] [Indexed: 12/17/2022] Open
Abstract
Generation of neuronal diversity is a biological strategy widely used in the brain to process complex information. The olfactory bulb is the first relay station of olfactory information in the vertebrate central nervous system. In the olfactory bulb, axons of the olfactory sensory neurons form synapses with dendrites of projection neurons that transmit the olfactory information to the olfactory cortex. Historically, the olfactory bulb projection neurons have been classified into two populations, mitral cells and tufted cells. The somata of these cells are distinctly segregated within the layers of the olfactory bulb; the mitral cells are located in the mitral cell layer while the tufted cells are found in the external plexiform layer. Although mitral and tufted cells share many morphological, biophysical, and molecular characteristics, they differ in soma size, projection patterns of their dendrites and axons, and odor responses. In addition, tufted cells are further subclassified based on the relative depth of their somata location in the external plexiform layer. Evidence suggests that different types of tufted cells have distinct cellular properties and play different roles in olfactory information processing. Therefore, mitral and different types of tufted cells are considered as starting points for parallel pathways of olfactory information processing in the brain. Moreover, recent studies suggest that mitral cells also consist of heterogeneous subpopulations with different cellular properties despite the fact that the mitral cell layer is a single-cell layer. In this review, we first compare the morphology of projection neurons in the olfactory bulb of different vertebrate species. Next, we explore the similarities and differences among subpopulations of projection neurons in the rodent olfactory bulb. We also discuss the timing of neurogenesis as a factor for the generation of projection neuron heterogeneity in the olfactory bulb. Knowledge about the subpopulations of olfactory bulb projection neurons will contribute to a better understanding of the complex olfactory information processing in higher brain regions.
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Affiliation(s)
- Fumiaki Imamura
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, United States
| | - Ayako Ito
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, United States
| | - Brandon J LaFever
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, United States
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24
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Liu MT, Na M, Li Y, Biscoe MR, Ryan K. Conformational Sensing by a Mammalian Olfactory Receptor. Chemistry 2020; 26:11462-11469. [PMID: 32691933 DOI: 10.1002/chem.202001390] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 05/22/2020] [Indexed: 01/08/2023]
Abstract
To identify odors, the mammalian nose deploys hundreds of olfactory receptors (ORs) from the rhodopsin-like class of the G protein-coupled receptor superfamily. Odorants having multiple rotatable bonds present a problem for the stereochemical shape-based matching process assumed to govern the sense of smell through OR-odorant recognition. We conformationally restricted the carbon chain of the odorant octanal to ask whether an OR can respond differently to different odorant conformations. By using calcium imaging to monitor signal transduction in sensory neurons expressing the mouse aldehyde OR, Olfr2, we found that the spatial position of the C7 and C8 carbon atoms of octanal, in relation to its -CHO group, determines whether an aliphatic aldehyde functions as an agonist, partial agonist or antagonist. Our experiments provide evidence that an odorant can manipulate an OR through its intrinsic conformational repertoire, in unexpected analogy to the photon-controlled aldehyde manipulation observed in rhodopsin.
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Affiliation(s)
- Min Ting Liu
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY, 10031, USA.,Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Mihwa Na
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY, 10031, USA.,Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Yadi Li
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY, 10031, USA.,Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Mark R Biscoe
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY, 10031, USA.,Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Kevin Ryan
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY, 10031, USA.,Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA.,Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
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25
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LINE-1 specific nuclear organization in mice olfactory sensory neurons. Mol Cell Neurosci 2020; 105:103494. [PMID: 32387751 DOI: 10.1016/j.mcn.2020.103494] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 03/31/2020] [Accepted: 04/05/2020] [Indexed: 12/21/2022] Open
Abstract
Long interspersed nuclear elements-1 (LINE-1) are mobile DNA elements that comprise the majority of interspersed repeats in the mammalian genome. During the last decade, these transposable sequences have been described as controlling elements involved in transcriptional regulation and genome plasticity. Recently, LINE-1 have been implicated in neurogenesis, but to date little is known about their nuclear organization in neurons. The olfactory epithelium is a site of continuous neurogenesis, and loci of olfactory receptor genes are enriched in LINE-1 copies. Olfactory neurons have a unique inverted nuclear architecture and constitutive heterochromatin forms a block in the center of the nuclei. Our DNA FISH images show that, even though LINE-1 copies are dispersed throughout the mice genome, they are clustered forming a cap around the central heterochromatin block and frequently occupy the same position as facultative heterochromatin in olfactory neurons nuclei. This specific LINE-1 organization could not be observed in other olfactory epithelium cell types. Analyses of H3K27me3 and H3K9me3 ChIP-seq data from olfactory epithelium revealed that LINE-1 copies located at OR gene loci show different enrichment for these heterochromatin marks. We also found that LINE-1 are transcribed in mouse olfactory epithelium. These results suggest that LINE-1 play a role in the olfactory neurons' nuclear architecture. SIGNIFICANCE STATEMENT: LINE-1 are mobile DNA elements and comprise almost 20% of mice and human genomes. These retrotransposons have been implicated in neurogenesis. We show for the first time that LINE-1 retrotransposons have a specific nuclear organization in olfactory neurons, forming aggregates concentric to the heterochromatin block and frequently occupying the same region as facultative heterochromatin. We found that LINE-1 at olfactory receptor gene loci are differently enriched for H3K9me3 and H3K27me3, but LINE-1 transcripts could be detected in the olfactory epithelium. We speculate that these retrotransposons play an active role in olfactory neurons' nuclear architecture.
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26
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A Group of Olfactory Receptor Alleles that Encode Full Length Proteins are Down-Regulated as Olfactory Sensory Neurons Mature. Sci Rep 2020; 10:1781. [PMID: 32020011 PMCID: PMC7000733 DOI: 10.1038/s41598-020-58779-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 01/21/2020] [Indexed: 11/08/2022] Open
Abstract
The family of olfactory receptors (ORs) subserves the sense of smell and includes both functional alleles and pseudogenes, the latter identified by mutations resulting in frame shift or premature truncation. During neuronal differentiation, nonfunctional ORs are expressed initially but then are switched out, and/or the olfactory sensory neurons (OSNs) expressing them die. We carried out a transcriptomic analysis of FACS-isolated cells from ΔSox2-eGFP, Neurog1-eGFP BAC and ΔOMP-eGFP strains of uninjured and olfactory bulbectomized transgenic mice that correspond to distinct stages in the progression from globose basal cell stem cells to fully mature OSNs. We analyzed the expression pattern of 1094 unique receptors across this progression and found that the vast majority were characterized by a typical and expected pattern of expression; i.e., levels of OR mRNA peaking in mature OSNs. However, 43 ORs, including several known pseudogenes, were different, such that mRNA expression declined in the mature OSNs relative to earlier stages. Protein and promoter sequence analysis of the atypical group did not uncover any obvious differences between them and more typical ORs. Nonetheless, the pattern of expression suggests that atypical ORs may be non-functional despite the lack of any obvious abnormality in the sequence analyses.
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27
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Wang YZ, Fan H, Ji Y, Reynolds K, Gu R, Gan Q, Yamagami T, Zhao T, Hamad S, Bizen N, Takebayashi H, Chen Y, Wu S, Pleasure D, Lam K, Zhou CJ. Olig2 regulates terminal differentiation and maturation of peripheral olfactory sensory neurons. Cell Mol Life Sci 2019; 77:3597-3609. [PMID: 31758234 DOI: 10.1007/s00018-019-03385-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 11/08/2019] [Accepted: 11/12/2019] [Indexed: 01/20/2023]
Abstract
The bHLH transcription factor Olig2 is required for sequential cell fate determination of both motor neurons and oligodendrocytes and for progenitor proliferation in the central nervous system. However, the role of Olig2 in peripheral sensory neurogenesis remains unknown. We report that Olig2 is transiently expressed in the newly differentiated olfactory sensory neurons (OSNs) and is down-regulated in the mature OSNs in mice from early gestation to adulthood. Genetic fate mapping demonstrates that Olig2-expressing cells solely give rise to OSNs in the peripheral olfactory system. Olig2 depletion does not affect the proliferation of peripheral olfactory progenitors and the fate determination of OSNs, sustentacular cells, and the olfactory ensheathing cells. However, the terminal differentiation and maturation of OSNs are compromised in either Olig2 single or Olig1/Olig2 double knockout mice, associated with significantly diminished expression of multiple OSN maturation and odorant signaling genes, including Omp, Gnal, Adcy3, and Olfr15. We further demonstrate that Olig2 binds to the E-box in the Omp promoter region to regulate its expression. Taken together, our results reveal a distinctly novel function of Olig2 in the periphery nervous system to regulate the terminal differentiation and maturation of olfactory sensory neurons.
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Affiliation(s)
- Ya-Zhou Wang
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, 169 Chang Le Xi Road, Xi'an, 710032, Shaanxi, China.,Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Hong Fan
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, 169 Chang Le Xi Road, Xi'an, 710032, Shaanxi, China
| | - Yu Ji
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA.,Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Kurt Reynolds
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA.,Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Ran Gu
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA.,Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Qini Gan
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Takashi Yamagami
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Tianyu Zhao
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Salaheddin Hamad
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Norihisa Bizen
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Asahimachi, Chuo-ku, Niigata, 951-8510, Japan
| | - Hirohide Takebayashi
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Asahimachi, Chuo-ku, Niigata, 951-8510, Japan
| | - YiPing Chen
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA, 70118, USA
| | - Shengxi Wu
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, 169 Chang Le Xi Road, Xi'an, 710032, Shaanxi, China
| | - David Pleasure
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Kit Lam
- Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA
| | - Chengji J Zhou
- Institute for Pediatric Regenerative Medicine of Shriners Hospitals for Children, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA. .,Department of Biochemistry and Molecular Medicine, University of California at Davis, School of Medicine, 2425 Stockton Blvd., Sacramento, CA, 95817, USA.
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Sequential Maturation of Olfactory Sensory Neurons in the Mature Olfactory Epithelium. eNeuro 2019; 6:ENEURO.0266-19.2019. [PMID: 31554664 PMCID: PMC6795559 DOI: 10.1523/eneuro.0266-19.2019] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 09/10/2019] [Accepted: 09/18/2019] [Indexed: 12/20/2022] Open
Abstract
The formation of the olfactory nerve and olfactory bulb (OB) glomeruli begins embryonically in mice. However, the development of the olfactory system continues throughout life with the addition of new olfactory sensory neurons (OSNs) in the olfactory epithelium (OE). Much attention has been given to the perinatal innervation of the OB by OSN axons, but in the young adult the process of OSN maturation and axon targeting to the OB remains controversial. To address this gap in understanding, we used BrdU to label late-born OSNs in young adult mice at postnatal day 25 (P25-born OSNs) and timed their molecular maturation following basal cell division. We show that OSNs in young adults undergo a sequential molecular development with the expression of GAP 43 (growth-associated protein 43) > AC3 (adenylyl cyclase 3) > OMP (olfactory marker protein), consecutively, in a time frame of ∼8 d. To assess OSN axon development, we implemented an in vivo fate-mapping strategy to label P25-born OSNs with ZsGreen. Using sampling intervals of 24 h, we demonstrate the progressive extension of OSN axons in the OE, through the foramen of the cribriform plate, and onto the surface of the OB. OSN axons reached the OB and began to target and robustly innervate specific glomeruli ∼10 d following basal cell division, a time point at which OMP expression becomes evident. Our data demonstrate a sequential process of correlated axon extension and molecular maturation that is similar to that seen in the neonate, but on a slightly longer timescale and with regional differences in the OE.
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29
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Abstract
The formation of the olfactory nerve and olfactory bulb (OB) glomeruli begins embryonically in mice. However, the development of the olfactory system continues throughout life with the addition of new olfactory sensory neurons (OSNs) in the olfactory epithelium (OE). Much attention has been given to the perinatal innervation of the OB by OSN axons, but in the young adult the process of OSN maturation and axon targeting to the OB remains controversial. To address this gap in understanding, we used BrdU to label late-born OSNs in young adult mice at postnatal day 25 (P25-born OSNs) and timed their molecular maturation following basal cell division. We show that OSNs in young adults undergo a sequential molecular development with the expression of GAP 43 (growth-associated protein 43) > AC3 (adenylyl cyclase 3) > OMP (olfactory marker protein), consecutively, in a time frame of ∼8 d. To assess OSN axon development, we implemented an in vivo fate-mapping strategy to label P25-born OSNs with ZsGreen. Using sampling intervals of 24 h, we demonstrate the progressive extension of OSN axons in the OE, through the foramen of the cribriform plate, and onto the surface of the OB. OSN axons reached the OB and began to target and robustly innervate specific glomeruli ∼10 d following basal cell division, a time point at which OMP expression becomes evident. Our data demonstrate a sequential process of correlated axon extension and molecular maturation that is similar to that seen in the neonate, but on a slightly longer timescale and with regional differences in the OE.
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30
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Doulazmi M, Cros C, Dusart I, Trembleau A, Dubacq C. Alternative polyadenylation produces multiple 3' untranslated regions of odorant receptor mRNAs in mouse olfactory sensory neurons. BMC Genomics 2019; 20:577. [PMID: 31299892 PMCID: PMC6624953 DOI: 10.1186/s12864-019-5927-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 06/23/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Odorant receptor genes constitute the largest gene family in mammalian genomes and this family has been extensively studied in several species, but to date far less attention has been paid to the characterization of their mRNA 3' untranslated regions (3'UTRs). Given the increasing importance of UTRs in the understanding of RNA metabolism, and the growing interest in alternative polyadenylation especially in the nervous system, we aimed at identifying the alternative isoforms of odorant receptor mRNAs generated through 3'UTR variation. RESULTS We implemented a dedicated pipeline using IsoSCM instead of Cufflinks to analyze RNA-Seq data from whole olfactory mucosa of adult mice and obtained an extensive description of the 3'UTR isoforms of odorant receptor mRNAs. To validate our bioinformatics approach, we exhaustively analyzed the 3'UTR isoforms produced from 2 pilot genes, using molecular approaches including northern blot and RNA ligation mediated polyadenylation test. Comparison between datasets further validated the pipeline and confirmed the alternative polyadenylation patterns of odorant receptors. Qualitative and quantitative analyses of the annotated 3' regions demonstrate that 1) Odorant receptor 3'UTRs are longer than previously described in the literature; 2) More than 77% of odorant receptor mRNAs are subject to alternative polyadenylation, hence generating at least 2 detectable 3'UTR isoforms; 3) Splicing events in 3'UTRs are restricted to a limited subset of odorant receptor genes; and 4) Comparison between male and female data shows no sex-specific differences in odorant receptor 3'UTR isoforms. CONCLUSIONS We demonstrated for the first time that odorant receptor genes are extensively subject to alternative polyadenylation. This ground-breaking change to the landscape of 3'UTR isoforms of Olfr mRNAs opens new avenues for investigating their respective functions, especially during the differentiation of olfactory sensory neurons.
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Affiliation(s)
- Mohamed Doulazmi
- CNRS, Institut de Biologie Paris Seine, Biological adaptation and ageing, B2A, Sorbonne Université, F-75005 Paris, France
| | - Cyril Cros
- CNRS, INSERM, Institut de Biologie Paris Seine, Neuroscience Paris Seine, NPS, Sorbonne Université, F-75005 Paris, France
- Present Address: Columbia University, New York, NY 10027 USA
| | - Isabelle Dusart
- CNRS, INSERM, Institut de Biologie Paris Seine, Neuroscience Paris Seine, NPS, Sorbonne Université, F-75005 Paris, France
| | - Alain Trembleau
- CNRS, INSERM, Institut de Biologie Paris Seine, Neuroscience Paris Seine, NPS, Sorbonne Université, F-75005 Paris, France
| | - Caroline Dubacq
- CNRS, INSERM, Institut de Biologie Paris Seine, Neuroscience Paris Seine, NPS, Sorbonne Université, F-75005 Paris, France
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31
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Vaddadi N, Iversen K, Raja R, Phen A, Brignall A, Dumontier E, Cloutier JF. Kirrel2 is differentially required in populations of olfactory sensory neurons for the targeting of axons in the olfactory bulb. Development 2019; 146:dev.173310. [PMID: 31142543 DOI: 10.1242/dev.173310] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 05/15/2019] [Indexed: 01/25/2023]
Abstract
The formation of olfactory maps in the olfactory bulb (OB) is crucial for the control of innate and learned mouse behaviors. Olfactory sensory neurons (OSNs) expressing a specific odorant receptor project axons into spatially conserved glomeruli within the OB and synapse onto mitral cell dendrites. Combinatorial expression of members of the Kirrel family of cell adhesion molecules has been proposed to regulate OSN axonal coalescence; however, loss-of-function experiments have yet to establish their requirement in this process. We examined projections of several OSN populations in mice that lacked either Kirrel2 alone, or both Kirrel2 and Kirrel3. Our results show that Kirrel2 and Kirrel3 are dispensable for the coalescence of MOR1-3-expressing OSN axons to the most dorsal region (DI) of the OB. In contrast, loss of Kirrel2 caused MOR174-9- and M72-expressing OSN axons, projecting to the DII region, to target ectopic glomeruli. Our loss-of-function approach demonstrates that Kirrel2 is required for axonal coalescence in subsets of OSNs that project axons to the DII region and reveals that Kirrel2/3-independent mechanisms also control OSN axonal coalescence in certain regions of the OB.
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Affiliation(s)
- Neelima Vaddadi
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3A 2B4, Canada
| | - Katrine Iversen
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3A 2B4, Canada
| | - Reesha Raja
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3A 2B4, Canada
| | - Alina Phen
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada
| | - Alexandra Brignall
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada
| | - Emilie Dumontier
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada
| | - Jean-François Cloutier
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada .,Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3A 2B4, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada
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32
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Na M, Liu MT, Nguyen MQ, Ryan K. Single-Neuron Comparison of the Olfactory Receptor Response to Deuterated and Nondeuterated Odorants. ACS Chem Neurosci 2019; 10:552-562. [PMID: 30343564 DOI: 10.1021/acschemneuro.8b00416] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The mammalian olfactory receptors (ORs) constitute a large subfamily of the Class A G-protein coupled receptors (GPCRs). The molecular details of how these receptors convert odorant chemical information into neural signal are unknown, but are predicted by analogy to other GPCRs to involve stabilization of the activated form of the OR by the odorant. An alternative hypothesis maintains that the vibrational modes of an odorant's bonds constitute the main determinant for OR activation, and that odorants containing deuterium in place of hydrogen should activate different sets of OR family members. Experiments using heterologously expressed ORs have failed to show different responses for deuterated odorants, but experiments in the sensory neuron environment have been lacking. We tested the response to deuterated and nondeuterated versions of p-cymene, 1-octanol, 1-undecanol, and octanal in dissociated mouse olfactory receptor neurons (ORNs) by calcium imaging. In all, we tested 23 812 cells, including a subset expressing recombinant mouse olfactory receptor 2 ( Olfr2/OR-I7 ), and found that nearly all of the 1610 odorant-responding neurons were unable to distinguish the D- and H-odorants. These results support the conclusion that if mammals can perceive deuterated odorants differently, the difference arises from the receptor-independent steps of olfaction. Nevertheless, 0.81% of the responding ORNs responded differently to D- and H-odorants, and those in the octanal experiments responded selectively to H-octanal at concentrations from 3 to 100 μM. The few ORs responding differently to H and D may be hypersensitive to one of the several H/D physicochemical differences, such as the difference in H/D hydrophobicity.
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Affiliation(s)
- Mihwa Na
- Department of Chemistry and Biochemistry, The City College of New York, 160 Convent Avenue, New York, New York 10031, United States
| | - Min Ting Liu
- Department of Chemistry and Biochemistry, The City College of New York, 160 Convent Avenue, New York, New York 10031, United States
| | - Minh Q. Nguyen
- Taste and Smell Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Kevin Ryan
- Department of Chemistry and Biochemistry, The City College of New York, 160 Convent Avenue, New York, New York 10031, United States
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33
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Wu Y, Ma L, Duyck K, Long CC, Moran A, Scheerer H, Blanck J, Peak A, Box A, Perera A, Yu CR. A Population of Navigator Neurons Is Essential for Olfactory Map Formation during the Critical Period. Neuron 2018; 100:1066-1082.e6. [PMID: 30482691 DOI: 10.1016/j.neuron.2018.09.051] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 08/10/2018] [Accepted: 09/27/2018] [Indexed: 11/29/2022]
Abstract
In the developing brain, heightened plasticity during the critical period enables the proper formation of neural circuits. Here, we identify the "navigator" neurons, a group of perinatally born olfactory sensory neurons, as playing an essential role in establishing the olfactory map during the critical period. The navigator axons project circuitously in the olfactory bulb and traverse multiple glomeruli before terminating in perspective glomeruli. These neurons undergo a phase of exuberant axon growth and exhibit a shortened lifespan. Single-cell transcriptome analyses reveal distinct molecular signatures for the navigators. Extending their lifespan prolongs the period of exuberant growth and perturbs axon convergence. Conversely, a genetic ablation experiment indicates that, despite postnatal neurogenesis, only the navigators are endowed with the ability to establish a convergent map. The presence and the proper removal of the navigator neurons are both required to establish tight axon convergence into the glomeruli.
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Affiliation(s)
- Yunming Wu
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Limei Ma
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Kyle Duyck
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Carter C Long
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Andrea Moran
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Hayley Scheerer
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Jillian Blanck
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Allison Peak
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Andrew Box
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - Anoja Perera
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
| | - C Ron Yu
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA; Department of Anatomy and Cell Biology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA.
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34
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Savya SP, Kunkhyen T, Cheetham CEJ. Low survival rate of young adult-born olfactory sensory neurons in the undamaged mouse olfactory epithelium. J Bioenerg Biomembr 2018; 51:41-51. [PMID: 30302619 DOI: 10.1007/s10863-018-9774-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 10/02/2018] [Indexed: 01/24/2023]
Abstract
Olfactory sensory neurons (OSNs) are generated throughout life from progenitor cells in the olfactory epithelium. OSN axons project in an odorant receptor-specific manner to the olfactory bulb (OB), forming an ordered array of glomeruli where they provide sensory input to OB neurons. The tetracycline transactivator (tTA) system permits developmental stage-specific expression of reporter genes in OSNs and has been widely used for structural and functional studies of the development and plasticity of the mouse olfactory system. However, the cellular ages at which OSNs stop expressing reporters driven by the immature OSN-specific Gγ8-tTA driver line and begin to express reporters driven by the mature OSN-specific OMP-tTA driver line have not been directly determined. We pulse-labeled terminally dividing cells in the olfactory epithelium of 28-day-old (P28) mice with EdU and analyzed EdU labeling in OSNs expressing fluorescent reporter proteins under control of either the Gγ8-tTA or OMP-tTA driver line 5-14 days later. Expression of OMP-tTA-driven reporters began in 6-day-old OSNs, while the vast majority of newborn OSNs did not express Gγ8-tTA-driven fluorescent proteins beyond 8 days of cellular age. Surprisingly, we also found a low survival rate for P28-born OSNs, very few of which survived for more than 14 days. We propose that OSN survival requires the formation of stable synaptic connections and hence may be dependent on organismal age.
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Affiliation(s)
- Sajishnu P Savya
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St., BST E1456, Pittsburgh, PA, 15213, USA.,Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Tenzin Kunkhyen
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St., BST E1456, Pittsburgh, PA, 15213, USA
| | - Claire E J Cheetham
- Department of Neurobiology, University of Pittsburgh, 200 Lothrop St., BST E1456, Pittsburgh, PA, 15213, USA. .,Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USA.
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35
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Noble JC, Meredith D, Lane RP. Frequent and biased odorant receptor (OR) re-selection in an olfactory placode-derived cell line. PLoS One 2018; 13:e0204604. [PMID: 30256852 PMCID: PMC6157871 DOI: 10.1371/journal.pone.0204604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 09/11/2018] [Indexed: 11/18/2022] Open
Abstract
We previously characterized a clonal olfactory placode-derived cell line (OP6) as a model system for studying odorant receptor (OR) choice, where individual OP6 cells, similar to olfactory sensory neurons in vivo, transcribe one allele ("monoallelic") of one OR gene ("monogenic"). The OP6 cell line provides a unique opportunity to investigate intrinsic properties of OR regulation that cannot easily be investigated in vivo. First, whereas OR-expressing cells in vivo are post-mitotic, OP6 cells are immortalized, raising interesting questions about the stability of epigenetic states associated with OR selection/silencing as OP6 cells progress through the cell cycle. Second, OP6 cells have been isolated away from extrinsic developmental cues, and therefore, any long-term OR selection biases are likely to arise from intrinsic epigenetic states that persist in the absence of developmental context. In this study, we investigated OR re-selection frequency and selection biases within clonal OP6 cell populations. We found no evidence of OR stability through the cell cycle: our results were most consistent with OR re-selection events transpiring at least once per cell division, suggesting that chromatin states associated with OR selection in this system might not be maintained in the subsequent generation. In contrast, we found strong evidence for OR selection biases maintained over prolonged culturing across a diverse set of OP6 cell lineages, suggesting the persistence of intrinsic epigenetic states that advantage some OR loci over others. Together, our data suggest that in the absence of instructive cues, intrinsic epigenetic states influencing OR eligibility, but not those determining OR choice, might persist through the cell cycle.
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Affiliation(s)
- J. C. Noble
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut, United States of America
| | - Diane Meredith
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut, United States of America
| | - Robert P. Lane
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut, United States of America
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36
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Sinakevitch I, Bjorklund GR, Newbern JM, Gerkin RC, Smith BH. Comparative study of chemical neuroanatomy of the olfactory neuropil in mouse, honey bee, and human. BIOLOGICAL CYBERNETICS 2018; 112:127-140. [PMID: 28852854 PMCID: PMC5832527 DOI: 10.1007/s00422-017-0728-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Accepted: 08/14/2017] [Indexed: 06/07/2023]
Abstract
Despite divergent evolutionary origins, the organization of olfactory systems is remarkably similar across phyla. In both insects and mammals, sensory input from receptor cells is initially processed in synaptically dense regions of neuropil called glomeruli, where neural activity is shaped by local inhibition and centrifugal neuromodulation prior to being sent to higher-order brain areas by projection neurons. Here we review both similarities and several key differences in the neuroanatomy of the olfactory system in honey bees, mice, and humans, using a combination of literature review and new primary data. We have focused on the chemical identity and the innervation patterns of neuromodulatory inputs in the primary olfactory system. Our findings show that serotonergic fibers are similarly distributed across glomeruli in all three species. Octopaminergic/tyraminergic fibers in the honey bee also have a similar distribution, and possibly a similar function, to noradrenergic fibers in the mammalian OBs. However, preliminary evidence suggests that human OB may be relatively less organized than its counterparts in honey bee and mouse.
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Affiliation(s)
- Irina Sinakevitch
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ, 85287-4501, USA.
| | - George R Bjorklund
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ, 85287-4501, USA
| | - Jason M Newbern
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ, 85287-4501, USA
| | - Richard C Gerkin
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ, 85287-4501, USA
| | - Brian H Smith
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ, 85287-4501, USA.
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37
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Powell MA, Black RT, Smith TL, Reeves TM, Phillips LL. Mild Fluid Percussion Injury Induces Diffuse Axonal Damage and Reactive Synaptic Plasticity in the Mouse Olfactory Bulb. Neuroscience 2018; 371:106-118. [PMID: 29203228 PMCID: PMC5809206 DOI: 10.1016/j.neuroscience.2017.11.045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 11/21/2017] [Accepted: 11/27/2017] [Indexed: 12/21/2022]
Abstract
Despite the regenerative capacity of the olfactory bulb (OB), head trauma causes olfactory disturbances in up to 30% of patients. While models of olfactory nerve transection, olfactory receptor neuron (ORN) ablation, or direct OB impact have been used to examine OB recovery, these models are severe and not ideal for study of OB synaptic repair. We posited that a mild fluid percussion brain injury (mFPI), delivered over mid-dorsal cortex, would produce diffuse OB deafferentation without confounding pathology. Wild type FVB/NJ mice were subjected to mFPI and OB probed for ORN axon degeneration and onset of reactive synaptogenesis. OB extracts revealed 3 d postinjury elevation of calpain-cleaved 150-kDa αII-spectrin, an indicator of axon damage, in tandem with reduced olfactory marker protein (OMP), a protein specific to intact ORN axons. Moreover, mFPI also produced a 3-d peak in GFAP+ astrocyte and IBA1+ microglial reactivity, consistent with postinjury inflammation. OB glomeruli showed disorganized ORN axons, presynaptic degeneration, and glial phagocytosis at 3 and 7 d postinjury, all indicative of deafferentation. At 21 d after mFPI, normal synaptic structure re-emerged along with OMP recovery, supporting ORN afferent reinnervation. Robust 21 d postinjury upregulation of GAP-43 was consistent with the time course of ORN axon sprouting and synapse regeneration reported after more severe olfactory insult. Together, these findings define a cycle of synaptic degeneration and recovery at a site remote to non-contusive brain injury. We show that mFPI models diffuse ORN axon damage, useful for the study of time-dependent reactive synaptogenesis in the deafferented OB.
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Affiliation(s)
- Melissa A Powell
- Department of Anatomy and Neurobiology, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298, United States.
| | - Raiford T Black
- Department of Anatomy and Neurobiology, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298, United States.
| | - Terry L Smith
- Department of Anatomy and Neurobiology, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298, United States.
| | - Thomas M Reeves
- Department of Anatomy and Neurobiology, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298, United States.
| | - Linda L Phillips
- Department of Anatomy and Neurobiology, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298, United States.
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38
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Holl AM. Survival of mature mouse olfactory sensory neurons labeled genetically perinatally. Mol Cell Neurosci 2018; 88:258-269. [PMID: 29427775 DOI: 10.1016/j.mcn.2018.02.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 05/02/2017] [Accepted: 02/06/2018] [Indexed: 12/15/2022] Open
Abstract
The main olfactory epithelium (MOE) of an adult mouse harbors a few million mature olfactory sensory neurons (OSNs), which are traditionally defined as mature by their expression of the olfactory marker protein (OMP). Mature OSNs differentiate in situ from stem cells at the base of the MOE. The consensus view is that mature OSNs have a defined lifespan and then undergo programmed cell death, and that the adult MOE maintains homeostasis by generating new mature OSNs from stem cells. But there is also evidence for mature OSNs that are long-lived. Thus far modern genetic tools have not been applied to quantify survival of a population of OSNs that are mature at a given point in time. Here, a genetic strategy was developed to label irreversibly OMP-expressing OSNs in mice. A gene-targeted OMP-CreERT2 strain was generated in which mature OSNs express an enzymatically inactive version of the Cre recombinase. The fusion protein CreERT2 becomes transiently active when exposed to tamoxifen, and in the presence of a Cre reporter in the genome such as tdRFP, CreERT2-expressing cells become irreversibly labeled. A cohort of mice was generated with the same day of birth by in vitro fertilization and embryo transfer, and injected tamoxifen in their mothers at E18.5 of gestation. I counted RFP immunoreactive cells in the MOE and vomeronasal organ of 36 tamoxifen-exposed OMP-CreERT2 × tdRFP mice from 7 age groups: postnatal day (PD)1.5, PD3.5, PD6.5, 3 weeks, 9 weeks, 6 months, and 12 months. Approximately 7.8% of perinatally labeled cells remain at 12 months, confirming that some mature OSNs are indeed long-lived. The survival curve of the population of perinatally labeled MOE cells can be modeled with a mean half-life of 26 days for the population as a whole, excluding the long-lived cells.
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Affiliation(s)
- Anna-Maria Holl
- Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt, Germany.
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39
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Conditional Deletion of Ric-8b in Olfactory Sensory Neurons Leads to Olfactory Impairment. J Neurosci 2017; 37:12202-12213. [PMID: 29118104 DOI: 10.1523/jneurosci.0943-17.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 10/25/2017] [Accepted: 10/29/2017] [Indexed: 11/21/2022] Open
Abstract
The olfactory system can discriminate a vast number of odorants. This ability derives from the existence of a large family of odorant receptors expressed in the cilia of the olfactory sensory neurons. Odorant receptors signal through the olfactory-specific G-protein subunit, Gαolf. Ric-8b, a guanine nucleotide exchange factor, interacts with Gαolf and can amplify odorant receptor signal transduction in vitro To explore the function of Ric-8b in vivo, we generated a tissue specific knock-out mouse by crossing OMP-Cre transgenic mice to Ric-8b floxed mice. We found that olfactory-specific Ric-8b knock-out mice of mixed sex do not express the Gαolf protein in the olfactory epithelium. We also found that in these mice, the mature olfactory sensory neuron layer is reduced, and that olfactory sensory neurons show increased rate of cell death compared with wild-type mice. Finally, behavioral tests showed that the olfactory-specific Ric-8b knock-out mice show an impaired sense of smell, even though their motivation and mobility behaviors remain normal.SIGNIFICANCE STATEMENT Ric-8b is a guanine nucleotide exchange factor (GEF) expressed in the olfactory epithelium and in the striatum. Ric-8b interacts with the olfactory Gαolf subunit, and can amplify odorant signaling through odorant receptors in vitro However, the functional significance of this GEF in the olfactory neurons in vivo remains unknown. We report that deletion of Ric-8b in olfactory sensory neurons prevents stable expression of Gαolf. In addition, we demonstrate that olfactory neurons lacking Ric-8b (and consequently Gαolf) are more susceptible to cell death. Ric-8b conditional knock-out mice display impaired olfactory guided behavior. Our results reveal that Ric-8b is essential for olfactory function, and suggest that it may also be essential for Gαolf-dependent functions in the brain.
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40
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Coleman JH, Lin B, Schwob JE. Dissecting LSD1-Dependent Neuronal Maturation in the Olfactory Epithelium. J Comp Neurol 2017; 525:3391-3413. [PMID: 28597915 DOI: 10.1002/cne.24259] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 05/19/2017] [Accepted: 06/02/2017] [Indexed: 12/21/2022]
Abstract
Neurons in the olfactory epithelium (OE) each express a single dominant olfactory receptor (OR) allele from among roughly 1,000 different OR genes. While monogenic and monoallelic OR expression has been appreciated for over two decades, regulators of this process are still being described; most recently, epigenetic modifiers have been of high interest as silent OR genes are decorated with transcriptionally repressive trimethylated histone 3 lysine 9 (H3K9me3) whereas active OR genes are decorated with transcriptionally activating trimethylated histone 3 lysine 4 (H3K4me3). The lysine specific demethylase 1 (LSD1) demethylates at both of these lysine residues and has been shown to disrupt neuronal maturation and OR expression in the developing embryonic OE. Despite the growing literature on LSD1 expression in the OE, a complete characterization of the timing of LSD1 expression relative to neuronal maturation and of the function of LSD1 in the adult OE have yet to be reported. To fill this gap, the present study determined that LSD1 (1) is expressed in early dividing cells before OR expression and neuronal maturation and decreases at the time of OR stabilization; (2) colocalizes with the repressor CoREST (also known as RCOR1) and histone deacetylase 2 in these early dividing cells; and (3) is required for neuronal maturation during a distinct time window between activating reserve stem cells (horizontal basal cells) and Neurogenin1 (+) immediate neuronal precursors. Thus, this study clarifies the role of LSD1 in olfactory neuronal maturation.
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Affiliation(s)
- Julie H Coleman
- Department of Developmental, Molecular & Chemical Biology, School of Medicine, Tufts University, Boston, Massachusetts.,Program in Neuroscience, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts
| | - Brian Lin
- Department of Developmental, Molecular & Chemical Biology, School of Medicine, Tufts University, Boston, Massachusetts.,Program in Cell, Molecular & Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts
| | - James E Schwob
- Department of Developmental, Molecular & Chemical Biology, School of Medicine, Tufts University, Boston, Massachusetts
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41
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Mountoufaris G, Chen WV, Hirabayashi Y, O'Keeffe S, Chevee M, Nwakeze CL, Polleux F, Maniatis T. Multicluster Pcdh diversity is required for mouse olfactory neural circuit assembly. Science 2017; 356:411-414. [PMID: 28450637 PMCID: PMC5529182 DOI: 10.1126/science.aai8801] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 02/16/2017] [Indexed: 11/02/2022]
Abstract
The vertebrate clustered protocadherin (Pcdh) cell surface proteins are encoded by three closely linked gene clusters (Pcdhα, Pcdhβ, and Pcdhγ). Here, we show that all three gene clusters functionally cooperate to provide individual mouse olfactory sensory neurons (OSNs) with the cell surface diversity required for their assembly into distinct glomeruli in the olfactory bulb. Although deletion of individual Pcdh clusters had subtle phenotypic consequences, the loss of all three clusters (tricluster deletion) led to a severe axonal arborization defect and loss of self-avoidance. By contrast, when endogenous Pcdh diversity is overridden by the expression of a single-tricluster gene repertoire (α and β and γ), OSN axons fail to converge to form glomeruli, likely owing to contact-mediated repulsion between axons expressing identical combinations of Pcdh isoforms.
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Affiliation(s)
- George Mountoufaris
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Weisheng V Chen
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Yusuke Hirabayashi
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
- Department of Neuroscience, Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA
| | - Sean O'Keeffe
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Maxime Chevee
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Chiamaka L Nwakeze
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Franck Polleux
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
- Department of Neuroscience, Kavli Institute for Brain Science, Columbia University, New York, NY 10032, USA
| | - Tom Maniatis
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
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42
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Šmít D, Fouquet C, Pincet F, Zapotocky M, Trembleau A. Axon tension regulates fasciculation/defasciculation through the control of axon shaft zippering. eLife 2017; 6:19907. [PMID: 28422009 PMCID: PMC5478281 DOI: 10.7554/elife.19907] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 04/04/2017] [Indexed: 01/16/2023] Open
Abstract
While axon fasciculation plays a key role in the development of neural networks, very little is known about its dynamics and the underlying biophysical mechanisms. In a model system composed of neurons grown ex vivo from explants of embryonic mouse olfactory epithelia, we observed that axons dynamically interact with each other through their shafts, leading to zippering and unzippering behavior that regulates their fasciculation. Taking advantage of this new preparation suitable for studying such interactions, we carried out a detailed biophysical analysis of zippering, occurring either spontaneously or induced by micromanipulations and pharmacological treatments. We show that zippering arises from the competition of axon-axon adhesion and mechanical tension in the axons, and provide the first quantification of the force of axon-axon adhesion. Furthermore, we introduce a biophysical model of the zippering dynamics, and we quantitatively relate the individual zipper properties to global characteristics of the developing axon network. Our study uncovers a new role of mechanical tension in neural development: the regulation of axon fasciculation.
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Affiliation(s)
- Daniel Šmít
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Coralie Fouquet
- Neuroscience Paris Seine - Institute of Biology Paris Seine, Sorbonne Université, UPMC Univ Paris 06, INSERM, CNRS, Paris, France
| | - Frédéric Pincet
- Laboratoire de Physique Statistique, Ecole Normale Superieure, PSL Research University, Paris, France
| | - Martin Zapotocky
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Alain Trembleau
- Neuroscience Paris Seine - Institute of Biology Paris Seine, Sorbonne Université, UPMC Univ Paris 06, INSERM, CNRS, Paris, France
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43
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Bolz F, Kasper S, Bufe B, Zufall F, Pyrski M. Organization and Plasticity of Sodium Channel Expression in the Mouse Olfactory and Vomeronasal Epithelia. Front Neuroanat 2017; 11:28. [PMID: 28420967 PMCID: PMC5376585 DOI: 10.3389/fnana.2017.00028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/20/2017] [Indexed: 12/15/2022] Open
Abstract
To understand the molecular basis of neuronal excitation in the mammalian olfactory system, we conducted a systematic analysis of the organization of voltage-gated sodium (Nav) channel subunits in the main olfactory epithelium (MOE) and vomeronasal organ (VNO) of adult mice. We also analyzed changes in Nav channel expression during development in these two systems and during regeneration of the MOE. Quantitative PCR shows that Nav1.7 is the predominant isoform in both adult MOE and VNO. We detected pronounced immunoreactivity for Nav1.7 and Nav1.3 in axons of olfactory and vomeronasal sensory neurons (VSNs). Analysis of Nav1.2 and Nav1.6 revealed an unexpected subsystem-specific distribution. In the MOE, these Nav channels are absent from olfactory sensory neurons (OSNs) but present in non-neuronal olfactory cell types. In the VNO, Nav1.2 and Nav1.6 are confined to VSNs, with Nav1.2-immunoreactive somata solely present in the basal layer of the VNO. The subcellular localization of Nav1.3 and Nav1.7 in OSNs can change dramatically during periods of heightened plasticity in the MOE. During the first weeks of development and during regeneration of the olfactory epithelium following chemical lesion, expression of Nav1.3 and Nav1.7 is transiently enhanced in the somata of mature OSNs. Our results demonstrate a highly complex organization of Nav channel expression in the mouse olfactory system, with specific commonalities but also differences between the MOE and the VNO. On the basis of their subcellular localization, Nav1.3 and Nav1.7 should play major roles in action potential propagation in both MOE and VNO, whereas Nav1.2 and Nav1.6 are specific to the function of VSNs. The plasticity of Nav channel expression in OSNs during early development and recovery from injury could reflect important physiological requirements in a variety of activity-dependent mechanisms.
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Affiliation(s)
- Florian Bolz
- Center for Integrative Physiology and Molecular Medicine, Saarland UniversityHomburg, Germany
| | - Stephanie Kasper
- Center for Integrative Physiology and Molecular Medicine, Saarland UniversityHomburg, Germany
| | - Bernd Bufe
- Center for Integrative Physiology and Molecular Medicine, Saarland UniversityHomburg, Germany
| | - Frank Zufall
- Center for Integrative Physiology and Molecular Medicine, Saarland UniversityHomburg, Germany
| | - Martina Pyrski
- Center for Integrative Physiology and Molecular Medicine, Saarland UniversityHomburg, Germany
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44
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Finger TE, Bartel DL, Shultz N, Goodson NB, Greer CA. 5HTR3A-driven GFP labels immature olfactory sensory neurons. J Comp Neurol 2017; 525:1743-1755. [PMID: 28152579 DOI: 10.1002/cne.24180] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 01/25/2017] [Accepted: 01/26/2017] [Indexed: 12/12/2022]
Abstract
The ionotropic serotonin receptor, 5-HT3 , is expressed by many developing neurons within the central nervous system. Since the olfactory epithelium continues to generate new olfactory sensory neurons (OSNs) throughout life, we investigated the possibility that 5-HT3 is expressed in the adult epithelium. Using a transgenic mouse in which the promoter for the 5-HT3a subunit drives expression of green fluorescent protein (GFP), we assessed the expression of this marker in the olfactory epithelium of adult mice. Both the native 5-HT3a mRNA and GFP are expressed within globose basal cells of the olfactory and vomeronasal epithelium in adult mice. Whereas the 5-HT3a mRNA disappears relatively quickly after final cell division, the GFP label persists for about 5 days, thereby labeling immature OSNs in both the main olfactory system and vomeronasal organ. The GFP-labeled cells include both proliferative globose basal cells as well as immature OSNs exhibiting the hallmarks of ongoing differentiation including GAP43, PGP9.5, but the absence of olfactory marker protein. Some of the GFP-labeled OSNs show characteristics of more mature yet still developing OSNs including the presence of cilia extending from the apical knob and expression of NaV1.5, a component of the transduction cascade. These findings suggest that 5-HT3a is indicative of a proliferative or developmental state, regardless of age, and that the 5-HT3A GFP mice may prove useful for future studies of neurogenesis in the olfactory epithelium. J. Comp. Neurol. 525:1743-1755, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Thomas E Finger
- Department of Cell and Developmental Biology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado.,Program in Neuroscience, University of Colorado School of Medicine, Aurora, Colorado
| | - Dianna L Bartel
- Department of Cell and Developmental Biology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado.,Program in Neuroscience, University of Colorado School of Medicine, Aurora, Colorado.,Departments of Neurosurgery and Neuroscience, Yale University School of Medicine, New Haven, Connecticut
| | - Nicole Shultz
- Department of Cell and Developmental Biology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado
| | - Noah B Goodson
- Department of Cell and Developmental Biology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado.,Program in Neuroscience, University of Colorado School of Medicine, Aurora, Colorado
| | - Charles A Greer
- Departments of Neurosurgery and Neuroscience, Yale University School of Medicine, New Haven, Connecticut.,Interdepartmental Neuroscience Graduate Program, Yale University, New Haven, Connecticut
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45
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Zhang Z, Yang D, Zhang M, Zhu N, Zhou Y, Storm DR, Wang Z. Deletion of Type 3 Adenylyl Cyclase Perturbs the Postnatal Maturation of Olfactory Sensory Neurons and Olfactory Cilium Ultrastructure in Mice. Front Cell Neurosci 2017; 11:1. [PMID: 28154525 PMCID: PMC5243839 DOI: 10.3389/fncel.2017.00001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 01/04/2017] [Indexed: 01/08/2023] Open
Abstract
Type 3 adenylyl cyclase (Adcy3) is localized to the cilia of olfactory sensory neurons (OSNs) and is an essential component of the olfactory cyclic adenosine monophosphate (cAMP) signaling pathway. Although the role of this enzyme in odor detection and axonal projection in OSNs was previously characterized, researchers will still have to determine its function in the maturation of postnatal OSNs and olfactory cilium ultrastructure. Previous studies on newborns showed that the anatomic structure of the main olfactory epithelium (MOE) of Adcy3 knockout mice (Adcy3-/-) is indistinguishable from that of their wild-type littermates (Adcy3+/+), whereas the architecture and associated composition of MOE are relatively underdeveloped at this early age. The full effects of sensory deprivation on OSNs may not also be exhibited in such age. In the present study, following a comparison of postnatal OSNs in seven-, 30-, and 90-day-old Adcy3-/- mice and wild-type controls (Adcy3+/+), we observed that the absence of Adcy3 leads to cumulative defects in the maturation of OSNs. Upon aging, Adcy3-/- OSNs exhibited increase in immature cells and reduction in mature cells along with elevated apoptosis levels. The density and ultrastructure of Adcy3-/- cilia were also disrupted in mice upon aging. Collectively, our results reveal an indispensable role of Adcy3 in postnatal maturation of OSNs and maintenance of olfactory cilium ultrastructure in mice through adulthood.
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Affiliation(s)
- Zhe Zhang
- College of Life Science, Hebei UniversityBaoding, China; Medical College, Hebei UniversityBaoding, China
| | - Dong Yang
- College of Life Science, Hebei University Baoding, China
| | - Mengdi Zhang
- College of Life Science, Hebei University Baoding, China
| | - Ning Zhu
- Department of Cardiology, Baoding First Center Hospital Baoding, China
| | - Yanfen Zhou
- College of Life Science, Hebei University Baoding, China
| | - Daniel R Storm
- Department of Pharmacology, University of Washington, Seattle WA, USA
| | - Zhenshan Wang
- College of Life Science, Hebei University Baoding, China
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46
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Schwob JE, Jang W, Holbrook EH, Lin B, Herrick DB, Peterson JN, Hewitt Coleman J. Stem and progenitor cells of the mammalian olfactory epithelium: Taking poietic license. J Comp Neurol 2016; 525:1034-1054. [PMID: 27560601 DOI: 10.1002/cne.24105] [Citation(s) in RCA: 163] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 08/17/2016] [Accepted: 08/19/2016] [Indexed: 12/15/2022]
Abstract
The capacity of the olfactory epithelium (OE) for lifelong neurogenesis and regeneration depends on the persistence of neurocompetent stem cells, which self-renew as well as generating all of the cell types found within the nasal epithelium. This Review focuses on the types of stem and progenitor cells in the epithelium and their regulation. Both horizontal basal cells (HBCs) and some among the population of globose basal cells (GBCs) are stem cells, but the two types plays vastly different roles. The GBC population includes the basal cells that proliferate in the uninjured OE and is heterogeneous with respect to transcription factor expression. From upstream in the hierarchy to downstream, GBCs encompass 1) Sox2+ /Pax6+ stem-like cells that are totipotent and self-renew over the long term, 2) Ascl1+ transit-amplifying progenitors with a limited capacity for expansive proliferation, and 3) Neurog1+ /NeuroD1+ immediate precursor cells that make neurons directly. In contrast, the normally quiescent HBCs are activated to multipotency and proliferate when sustentacular cells are killed, but not when only OSNs die, indicating that HBCs are reserve stem cells that respond to severe epithelial injury. The master regulator of HBC activation is the ΔN isoform of the transcription factor p63; eliminating ΔNp63 unleashes HBC multipotency. Notch signaling, via Jagged1 ligand on Sus cells and Notch1 and Notch2 receptors on HBCs, is likely to play a major role in setting the level of p63 expression. Thus, ΔNp63 becomes a potential therapeutic target for reversing the neurogenic exhaustion characteristic of the aged OE. J. Comp. Neurol. 525:1034-1054, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- James E Schwob
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, 02132
| | - Woochan Jang
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, 02132
| | - Eric H Holbrook
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, 02132
| | - Brian Lin
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, 02132
| | - Daniel B Herrick
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, 02132
| | - Jesse N Peterson
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, 02132
| | - Julie Hewitt Coleman
- Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, 02132
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47
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Assens A, Dal Col JA, Njoku A, Dietschi Q, Kan C, Feinstein P, Carleton A, Rodriguez I. Alteration of Nrp1 signaling at different stages of olfactory neuron maturation promotes glomerular shifts along distinct axes in the olfactory bulb. Development 2016; 143:3817-3825. [PMID: 27578798 DOI: 10.1242/dev.138941] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 08/23/2016] [Indexed: 12/25/2022]
Abstract
Building the topographic map in the mammalian olfactory bulb is explained by a model based on two axes along which sensory neurons are guided: one dorsoventral and one anteroposterior. This latter axis relies on specific expression levels of Nrp1. To evaluate the role of this receptor in this process, we used an in vivo genetic approach to decrease or suppress Nrp1 in specific neuronal populations and at different time points during axonal targeting. We observed, in neurons that express the M71 or M72 odorant receptors, that Nrp1 inactivation leads to two distinct wiring alterations, depending on the time at which Nrp1 expression is altered: first, a surprising dorsal shift of the M71 and M72 glomeruli, which often fuse with their contralateral counterparts, and second the formation of anteriorized glomeruli. The two phenotypes are partly recapitulated in mice lacking the Nrp1 ligand Sema3A and in mice whose sensory neurons express an Nrp1 mutant unable to bind Sema3A. Using a mosaic conditional approach, we show that M71 axonal fibers can bypass the Nrp1 signals that define their target area, since they are hijacked and coalesce with Nrp1-deficient M71-expressing axons that target elsewhere. Together, these findings show drastically different axonal targeting outcomes dependent on the timing at which Nrp1/Sema3A signaling is altered.
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Affiliation(s)
- Alexis Assens
- Department of Genetics and Evolution, University of Geneva, Geneva 1205, Switzerland.,Geneva Neuroscience Center, University of Geneva, Geneva 1205, Switzerland
| | - Julien A Dal Col
- Department of Genetics and Evolution, University of Geneva, Geneva 1205, Switzerland.,Geneva Neuroscience Center, University of Geneva, Geneva 1205, Switzerland
| | - Anthony Njoku
- Department of Genetics and Evolution, University of Geneva, Geneva 1205, Switzerland.,Geneva Neuroscience Center, University of Geneva, Geneva 1205, Switzerland
| | - Quentin Dietschi
- Department of Genetics and Evolution, University of Geneva, Geneva 1205, Switzerland.,Geneva Neuroscience Center, University of Geneva, Geneva 1205, Switzerland
| | - Chenda Kan
- Department of Genetics and Evolution, University of Geneva, Geneva 1205, Switzerland.,Geneva Neuroscience Center, University of Geneva, Geneva 1205, Switzerland
| | - Paul Feinstein
- Department of Biological Sciences, Hunter College and The Graduate Center Biochemistry, Biology and Biopsychology and Behavioral Neuroscience Programs, CUNY, New York, NY10065, USA
| | - Alan Carleton
- Geneva Neuroscience Center, University of Geneva, Geneva 1205, Switzerland .,Department of Basic Neurosciences, School of Medicine, University of Geneva, Geneva 1205, Switzerland
| | - Ivan Rodriguez
- Department of Genetics and Evolution, University of Geneva, Geneva 1205, Switzerland .,Geneva Neuroscience Center, University of Geneva, Geneva 1205, Switzerland
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Regeneration and rewiring of rodent olfactory sensory neurons. Exp Neurol 2016; 287:395-408. [PMID: 27264358 DOI: 10.1016/j.expneurol.2016.06.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 05/27/2016] [Accepted: 06/01/2016] [Indexed: 12/24/2022]
Abstract
The olfactory sensory neurons are the only neurons in the mammalian nervous system that not only regenerate naturally and in response to injury, but also project to specific targets in the brain. The stem cells in the olfactory epithelium commit to both neuronal and non-neuronal lineages depending on the environmental conditions. They provide a continuous supply of new neurons. A newly generated neuron must express a specific odorant receptor gene and project to a central target consist of axons expressing the same receptor type. Recent studies have provided insights into this highly regulated, complex process. However, the molecular mechanisms that determine the regenerative capacity of stem cells, and the ability of newly generated neurons in directing their axons toward specific targets, remain elusive. Here we review progresses and controversies in the field and offer testable models.
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Shepard BD, Pluznick JL. How does your kidney smell? Emerging roles for olfactory receptors in renal function. Pediatr Nephrol 2016; 31:715-23. [PMID: 26264790 PMCID: PMC4752438 DOI: 10.1007/s00467-015-3181-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 06/24/2015] [Accepted: 07/22/2015] [Indexed: 12/12/2022]
Abstract
Olfactory receptors (ORs) are chemosensors that are responsible for one's sense of smell. In addition to this specialized role in the nose, recent evidence suggests that ORs are also found in a variety of additional tissues including the kidney. As this list of renal ORs continues to expand, it is becoming clear that they play important roles in renal and whole-body physiology, including a novel role in blood pressure regulation. In this review, we highlight important considerations that are crucial when studying ORs and present the current literature on renal ORs and their emerging relevance in maintaining renal function.
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Abdus-Saboor I, Al Nufal MJ, Agha MV, Ruinart de Brimont M, Fleischmann A, Shykind BM. An Expression Refinement Process Ensures Singular Odorant Receptor Gene Choice. Curr Biol 2016; 26:1083-90. [PMID: 27040780 DOI: 10.1016/j.cub.2016.02.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 12/25/2015] [Accepted: 02/12/2016] [Indexed: 12/11/2022]
Abstract
Odorant receptor (OR) gene choice in mammals is a paradigmatic example of monogenic and monoallelic transcriptional selection, in which each olfactory sensory neuron (OSN) chooses to express one OR allele from over 1,000 encoded in the genome [1-3]. This process, critical for generation of the circuit from nose to brain [4-6], is thought to occur in two steps: a slow initial phase that randomly activates a single OR allele, followed by a rapid feedback that halts subsequent expression [7-14]. Inherent in this model is a finite failure rate wherein multiple OR alleles may be activated prior to feedback suppression [15, 16]. Confronted with more than one receptor, the neuron would need to activate a refinement mechanism to eliminate multigenic OR expression and resolve unique neuronal identity [16], critical to the generation of the circuit from nose to olfactory bulb. Here we used a genetic approach in mice to reveal a new facet of OR regulation that corrects adventitious activation of multiple OR alleles, restoring monogenic OR expression and unique neuronal identity. Using the tetM71tg model system, in which the M71 OR is expressed in >95% of mature OSNs and potently suppresses the expression of the endogenous OR repertoire [10], we provide clear evidence of a post-selection refinement (PSR) process that winnows down the number of ORs. We further demonstrate that PSR efficiency is linked to OR expression level, suggesting an underlying competitive process and shedding light on OR gene switching and the fundamental mechanism of singular OR choice.
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Affiliation(s)
- Ishmail Abdus-Saboor
- Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar
| | - Mohammed J Al Nufal
- Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar
| | - Maha V Agha
- Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar
| | - Marion Ruinart de Brimont
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS UMR 7241, and INSERM U1050, Paris 75005, France
| | - Alexander Fleischmann
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS UMR 7241, and INSERM U1050, Paris 75005, France
| | - Benjamin M Shykind
- Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar.
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