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Yusuf N, Monahan K. Epigenetic programming of stochastic olfactory receptor choice. Genesis 2024; 62:e23593. [PMID: 38562011 PMCID: PMC11003729 DOI: 10.1002/dvg.23593] [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: 11/27/2023] [Revised: 03/01/2024] [Accepted: 03/15/2024] [Indexed: 04/04/2024]
Abstract
The mammalian sense of smell relies upon a vast array of receptor proteins to detect odorant compounds present in the environment. The proper deployment of these receptor proteins in olfactory sensory neurons is orchestrated by a suite of epigenetic processes that remodel the olfactory genes in differentiating neuronal progenitors. The goal of this review is to elucidate the central role of gene regulatory processes acting in neuronal progenitors of olfactory sensory neurons that lead to a singular expression of an odorant receptor in mature olfactory sensory neurons. We begin by describing the principal features of odorant receptor gene expression in mature olfactory sensory neurons. Next, we delineate our current understanding of how these features emerge from multiple gene regulatory mechanisms acting in neuronal progenitors. Finally, we close by discussing the key gaps in our understanding of how these regulatory mechanisms work and how they interact with each other over the course of differentiation.
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Affiliation(s)
- Nusrath Yusuf
- Division of Life Sciences-Molecular Biology and Biochemistry Department, Rutgers University-New Brunswick, New Brunswick, New Jersey, USA
| | - Kevin Monahan
- Division of Life Sciences-Molecular Biology and Biochemistry Department, Rutgers University-New Brunswick, New Brunswick, New Jersey, USA
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2
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Pourmorady AD, Bashkirova EV, Chiariello AM, Belagzhal H, Kodra A, Duffié R, Kahiapo J, Monahan K, Pulupa J, Schieren I, Osterhoudt A, Dekker J, Nicodemi M, Lomvardas S. RNA-mediated symmetry breaking enables singular olfactory receptor choice. Nature 2024; 625:181-188. [PMID: 38123679 PMCID: PMC10765522 DOI: 10.1038/s41586-023-06845-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 11/07/2023] [Indexed: 12/23/2023]
Abstract
Olfactory receptor (OR) choice provides an extreme example of allelic competition for transcriptional dominance, where every olfactory neuron stably transcribes one of approximately 2,000 or more OR alleles1,2. OR gene choice is mediated by a multichromosomal enhancer hub that activates transcription at a single OR3,4, followed by OR-translation-dependent feedback that stabilizes this choice5,6. Here, using single-cell genomics, we show formation of many competing hubs with variable enhancer composition, only one of which retains euchromatic features and transcriptional competence. Furthermore, we provide evidence that OR transcription recruits enhancers and reinforces enhancer hub activity locally, whereas OR RNA inhibits transcription of competing ORs over distance, promoting transition to transcriptional singularity. Whereas OR transcription is sufficient to break the symmetry between equipotent enhancer hubs, OR translation stabilizes transcription at the prevailing hub, indicating that there may be sequential non-coding and coding mechanisms that are implemented by OR alleles for transcriptional prevalence. We propose that coding OR mRNAs possess non-coding functions that influence nuclear architecture, enhance their own transcription and inhibit transcription from their competitors, with generalizable implications for probabilistic cell fate decisions.
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Affiliation(s)
- Ariel D Pourmorady
- Vagelos College of Physicians and Surgeons, Columbia University New York, New York, NY, USA
- Department of Neuroscience, Columbia University, New York, NY, USA
- Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University New York, New York, NY, USA
| | - Elizaveta V Bashkirova
- Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University New York, New York, NY, USA
- Integrated Program in Cellular, Molecular and Biomedical Studies, Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Andrea M Chiariello
- Department of Physics 'Ettore Pancini', University of Naples, and INFN, Napoli, Italy
| | - Houda Belagzhal
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Albana Kodra
- Integrated Program in Cellular, Molecular and Biomedical Studies, Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Genetics and Development, Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Rachel Duffié
- Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University New York, New York, NY, USA
| | - Jerome Kahiapo
- Department of Molecular Biology & Biochemistry, Rutgers School of Arts and Sciences, Robert Wood Johnson Medical School, Piscataway, NJ, USA
| | - Kevin Monahan
- Department of Molecular Biology & Biochemistry, Rutgers School of Arts and Sciences, Robert Wood Johnson Medical School, Piscataway, NJ, USA
| | - Joan Pulupa
- Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University New York, New York, NY, USA
| | - Ira Schieren
- Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University New York, New York, NY, USA
| | - Alexa Osterhoudt
- Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University New York, New York, NY, USA
- Integrated Program in Cellular, Molecular and Biomedical Studies, Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Job Dekker
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Mario Nicodemi
- Department of Physics 'Ettore Pancini', University of Naples, and INFN, Napoli, Italy
| | - Stavros Lomvardas
- Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University New York, New York, NY, USA.
- Department of Biochemistry and Molecular Biophysics, Vagelos College of Physicians and Surgeons, New York, NY, USA.
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3
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Bashkirova EV, Klimpert N, Monahan K, Campbell CE, Osinski J, Tan L, Schieren I, Pourmorady A, Stecky B, Barnea G, Xie XS, Abdus-Saboor I, Shykind BM, Marlin BJ, Gronostajski RM, Fleischmann A, Lomvardas S. Opposing, spatially-determined epigenetic forces impose restrictions on stochastic olfactory receptor choice. eLife 2023; 12:RP87445. [PMID: 38108811 PMCID: PMC10727497 DOI: 10.7554/elife.87445] [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] [Indexed: 12/19/2023] Open
Abstract
Olfactory receptor (OR) choice represents an example of genetically hardwired stochasticity, where every olfactory neuron expresses one out of ~2000 OR alleles in the mouse genome in a probabilistic, yet stereotypic fashion. Here, we propose that topographic restrictions in OR expression are established in neuronal progenitors by two opposing forces: polygenic transcription and genomic silencing, both of which are influenced by dorsoventral gradients of transcription factors NFIA, B, and X. Polygenic transcription of OR genes may define spatially constrained OR repertoires, among which one OR allele is selected for singular expression later in development. Heterochromatin assembly and genomic compartmentalization of OR alleles also vary across the axes of the olfactory epithelium and may preferentially eliminate ectopically expressed ORs with more dorsal expression destinations from this 'privileged' repertoire. Our experiments identify early transcription as a potential 'epigenetic' contributor to future developmental patterning and reveal how two spatially responsive probabilistic processes may act in concert to establish deterministic, precise, and reproducible territories of stochastic gene expression.
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Affiliation(s)
- Elizaveta V Bashkirova
- Integrated Program in Cellular, Molecular and Biomedical Studies, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, Columbia UniversityNew YorkUnited States
- Zuckerman Mind, Brain, and Behavior Institute, Columbia UniversityNew YorkUnited States
| | - Nell Klimpert
- Department of Neuroscience, Division of Biology and Medicine and Robert J. and Nancy D. Carney Institute for Brain Science, Brown UniversityProvidenceUnited States
| | - Kevin Monahan
- Department of Biochemistry and Molecular Biology, Rutgers UniversityNewarkUnited States
| | - Christine E Campbell
- Department of Biochemistry, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life SciencesBuffaloUnited States
- Genetics, Genomics, and Bioinformatics Graduate Program, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life SciencesBuffaloUnited States
| | - Jason Osinski
- Department of Biochemistry, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life SciencesBuffaloUnited States
- Genetics, Genomics, and Bioinformatics Graduate Program, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life SciencesBuffaloUnited States
| | - Longzhi Tan
- Department of Bioengineering, Stanford UniversityStanfordUnited States
| | - Ira Schieren
- Zuckerman Mind, Brain, and Behavior Institute, Columbia UniversityNew YorkUnited States
| | - Ariel Pourmorady
- Integrated Program in Cellular, Molecular and Biomedical Studies, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, Columbia UniversityNew YorkUnited States
- Zuckerman Mind, Brain, and Behavior Institute, Columbia UniversityNew YorkUnited States
| | - Beka Stecky
- Zuckerman Mind, Brain, and Behavior Institute, Columbia UniversityNew YorkUnited States
| | - Gilad Barnea
- Department of Neuroscience, Division of Biology and Medicine and Robert J. and Nancy D. Carney Institute for Brain Science, Brown UniversityProvidenceUnited States
| | - Xiaoliang Sunney Xie
- Beijing Innovation Center for Genomics, Peking UniversityBeijingChina
- Biomedical Pioneering Innovation Center, Peking UniversityBeijingChina
| | - Ishmail Abdus-Saboor
- Zuckerman Mind, Brain, and Behavior Institute, Columbia UniversityNew YorkUnited States
| | - Benjamin M Shykind
- Prevail Therapeutics- a wholly-owned subsidiary of Eli Lilly and CompanyNew YorkUnited States
| | - Bianca J Marlin
- Zuckerman Mind, Brain, and Behavior Institute, Columbia UniversityNew YorkUnited States
| | - Richard M Gronostajski
- Department of Biochemistry, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life SciencesBuffaloUnited States
- Genetics, Genomics, and Bioinformatics Graduate Program, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life SciencesBuffaloUnited States
| | - Alexander Fleischmann
- Department of Neuroscience, Division of Biology and Medicine and Robert J. and Nancy D. Carney Institute for Brain Science, Brown UniversityProvidenceUnited States
| | - Stavros Lomvardas
- Zuckerman Mind, Brain, and Behavior Institute, Columbia UniversityNew YorkUnited States
- Department of Biochemistry and Molecular Biophysics, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, Columbia UniversityNew YorkUnited States
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4
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Bashkirova EV, Klimpert N, Monahan K, Campbell CE, Osinski JM, Tan L, Schieren I, Pourmorady A, Stecky B, Barnea G, Xie XS, Abdus-Saboor I, Shykind B, Jones-Marlin B, Gronostajski RM, Fleischmann A, Lomvardas S. Opposing, spatially-determined epigenetic forces impose restrictions on stochastic olfactory receptor choice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.15.532726. [PMID: 36993168 PMCID: PMC10055043 DOI: 10.1101/2023.03.15.532726] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Olfactory receptor (OR) choice represents an example of genetically hardwired stochasticity, where every olfactory neuron expresses one out of ~2000 OR alleles in a probabilistic, yet stereotypic fashion. Here, we propose that topographic restrictions in OR expression are established in neuronal progenitors by two opposing forces: polygenic transcription and genomic silencing, both of which are influenced by dorsoventral gradients of transcription factors NFIA, B, and X. Polygenic transcription of OR genes may define spatially constrained OR repertoires, among which one OR allele is selected for singular expression later in development. Heterochromatin assembly and genomic compartmentalization of OR alleles also vary across the axes of the olfactory epithelium and may preferentially eliminate ectopically expressed ORs with more dorsal expression destinations from this "privileged" repertoire. Our experiments identify early transcription as a potential "epigenetic" contributor to future developmental patterning and reveal how two spatially responsive probabilistic processes may act in concert to establish deterministic, precise, and reproducible territories of stochastic gene expression.
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Affiliation(s)
- Elizaveta V Bashkirova
- Integrated Program in Cellular, Molecular and Biomedical Studies, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, Columbia University, New York, NY, 10032, USA
- Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY, 10027, USA
| | - Nell Klimpert
- Department of Neuroscience, Division of Biology and Medicine and Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, RI, USA
| | - Kevin Monahan
- Department of Biochemistry and Molecular Biology, Rutgers University, NJ, USA
| | - Christine E Campbell
- Department of Biochemistry, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, USA
- Genetics, Genomics, and Bioinformatics Graduate Program, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, USA
| | - Jason M Osinski
- Department of Biochemistry, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, USA
- Genetics, Genomics, and Bioinformatics Graduate Program, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, USA
| | - Longzhi Tan
- Department of Bioengineering, Stanford University, CA, USA
| | - Ira Schieren
- Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY, 10027, USA
| | - Ariel Pourmorady
- Integrated Program in Cellular, Molecular and Biomedical Studies, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, Columbia University, New York, NY, 10032, USA
- Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY, 10027, USA
| | - Beka Stecky
- Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY, 10027, USA
| | - Gilad Barnea
- Department of Neuroscience, Division of Biology and Medicine and Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, RI, USA
| | - X Sunnie Xie
- Beijing Innovation Center for Genomics, Peking University, Beijing, China
- Biomedical Pioneering Innovation Center, Peking University, Beijing, China
| | - Ishmail Abdus-Saboor
- Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY, 10027, USA
| | - Benjamin Shykind
- Department of Neuroscience, Division of Biology and Medicine and Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, RI, USA
| | - Bianca Jones-Marlin
- Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY, 10027, USA
| | - Richard M Gronostajski
- Department of Biochemistry, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, USA
- Genetics, Genomics, and Bioinformatics Graduate Program, University at Buffalo and New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, USA
| | - Alexander Fleischmann
- Department of Neuroscience, Division of Biology and Medicine and Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, RI, USA
| | - Stavros Lomvardas
- Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY, 10027, USA
- Department of Biochemistry and Molecular Biophysics, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, Columbia University, New York, NY, 10032, USA
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5
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Jafari S, Henriksson J, Yan H, Alenius M. Stress and odorant receptor feedback during a critical period after hatching regulates olfactory sensory neuron differentiation in Drosophila. PLoS Biol 2021; 19:e3001101. [PMID: 33793547 PMCID: PMC8043390 DOI: 10.1371/journal.pbio.3001101] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 04/13/2021] [Accepted: 03/02/2021] [Indexed: 11/19/2022] Open
Abstract
Here, we reveal that the regulation of Drosophila odorant receptor (OR) expression during the pupal stage is permissive and imprecise. We found that directly after hatching an OR feedback mechanism both directs and refines OR expression. We demonstrate that, as in mice, dLsd1 and Su(var)3-9 balance heterochromatin formation to direct OR expression. We show that the expressed OR induces dLsd1 and Su(var)3-9 expression, linking OR level and possibly function to OR expression. OR expression refinement shows a restricted duration, suggesting that a gene regulatory critical period brings olfactory sensory neuron differentiation to an end. Consistent with a change in differentiation, stress during the critical period represses dLsd1 and Su(var)3-9 expression and makes the early permissive OR expression permanent. This induced permissive gene regulatory state makes OR expression resilient to stress later in life. Hence, during a critical period OR feedback, similar to in mouse OR selection, defines adult OR expression in Drosophila.
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Affiliation(s)
- Shadi Jafari
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
- Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Johan Henriksson
- Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Hua Yan
- Department of Biology, University of Florida, Gainesville, Florida, United States of America
| | - Mattias Alenius
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
- Department of Molecular Biology, Umeå University, Umeå, Sweden
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6
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Enomoto T, Wakui K, Hirota J. Bcl11b is required for proper odorant receptor expression in the mouse septal organ. Cell Tissue Res 2021; 384:643-653. [PMID: 33783611 DOI: 10.1007/s00441-021-03444-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 03/01/2021] [Indexed: 11/24/2022]
Abstract
Individual olfactory sensory neurons (OSNs) in the mouse main olfactory epithelium express a single odorant receptor (OR) gene from the repertoire of either class I or class II ORs. The transcription factor Bcl11b determines the OR class to be expressed in OSNs. The septal organ (SO), a small neuroepithelium located at the ventral base of the nasal septum, is considered as an olfactory subsystem because it expresses a specific subset of ORs. However, the mechanisms underlying the generation and differentiation of SO-OSN remain unknown. In the present study, we show that the generation and differentiation of SO-OSN employ the same genetic pathway as in the OSN lineage, which is initiated by the neuronal fate determinant factor Ascl1. Additionally, the key role of Bcl11b in the SO is demonstrated by the abnormal phenotypes of Bcl11b-deficient mice: significant reduction in the expression of OR genes and in the number of mature SO-OSNs. Although SO-OSNs are specified to express a subset of class II OR genes in wild-type mice, the Bcl11b deletion led to the expression of class I OR genes, while the expression of class II OR genes was significantly decreased, with one exception of Olfr15. These results indicate that Bcl11b is necessary for proper OR expression in SO-OSNs.
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Affiliation(s)
- Takayuki Enomoto
- Department of Life Science and Technology, Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan.,Center for Biological Resources and Informatics, Tokyo Institute of Technology, Yokohama, Japan
| | - Koji Wakui
- Department of Life Science and Technology, Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Junji Hirota
- Department of Life Science and Technology, Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan. .,Center for Biological Resources and Informatics, Tokyo Institute of Technology, Yokohama, Japan.
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Movahedi K, Grosmaitre X, Feinstein P. Odorant receptors can mediate axonal identity and gene choice via cAMP-independent mechanisms. Open Biol 2017; 6:rsob.160018. [PMID: 27466441 PMCID: PMC4967819 DOI: 10.1098/rsob.160018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 07/01/2016] [Indexed: 01/24/2023] Open
Abstract
Odorant receptors (ORs) control several aspects of cell fate in olfactory sensory neurons (OSNs), including singular gene choice and axonal identity. The mechanisms of OR-induced axon guidance have been suggested to principally rely on G-protein signalling. Here, we report that for a subset of OSNs, deleting G proteins or altering their levels of signalling does not affect axonal identity. Signalling-deficient ORs or surrogate receptors that are unable to couple to Gs/Golf still provide axons with distinct identities and the anterior–posterior targeting of axons does not correlate with the levels of cAMP produced by genetic modifications. In addition, we refine the models of negative feedback by showing that ectopic ORs can be robustly expressed without suppressing endogenous gene choice. In conclusion, our results uncover a new feature of ORs, showing that they can instruct axonal identity and regulate olfactory map formation independent of canonical G-protein signalling and cAMP production.
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Affiliation(s)
- Kiavash Movahedi
- Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt, Germany Myeloid Cell Immunology Laboratory, VIB Inflammation Research Center, Ghent, Belgium Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel, Brussels, Belgium
| | - Xavier Grosmaitre
- Centre des Sciences du Goût et de l'Alimentation, CNRS, INRA, Université Bourgogne Franche-Comté, 21000 Dijon, France
| | - Paul Feinstein
- Department of Biological Sciences, Hunter College and The Graduate Center Biochemistry, Biology and Biopsychology and Behavioral Neuroscience Programs, CUNY, New York, NY, USA
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8
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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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9
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Nagai MH, Armelin-Correa LM, Malnic B. Monogenic and Monoallelic Expression of Odorant Receptors. Mol Pharmacol 2016; 90:633-639. [PMID: 27587538 DOI: 10.1124/mol.116.104745] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 08/31/2016] [Indexed: 02/06/2023] Open
Abstract
Odorant receptors (ORs) belong to a large gene family of rhodopsin-like G protein-coupled receptors (GPCRs). The mouse OR gene family is composed of ∼1000 OR genes, and the human OR gene family is composed of ∼400 OR genes. The OR genes are spread throughout the genome, and can be found in clusters or as solitary genes in almost all chromosomes. These chemosensory GPCRs are expressed in highly specialized cells, the olfactory sensory neurons of the nose. Each one of these neurons expresses a single OR gene out of the complete repertoire of genes. In addition, only one of the two homologous alleles of the chosen OR gene, the maternal or the paternal, is expressed per neuron. Here we review recent findings that help to elucidate the mechanisms underlying monogenic and monoallelic expression of OR genes.
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Affiliation(s)
- Maíra H Nagai
- Department of Biochemistry, University of São Paulo, São Paulo, Brazil
| | | | - Bettina Malnic
- Department of Biochemistry, University of São Paulo, São Paulo, Brazil
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10
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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: 31] [Impact Index Per Article: 3.9] [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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11
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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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12
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Tan L, Li Q, Xie XS. Olfactory sensory neurons transiently express multiple olfactory receptors during development. Mol Syst Biol 2015; 11:844. [PMID: 26646940 PMCID: PMC4704490 DOI: 10.15252/msb.20156639] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In mammals, each olfactory sensory neuron randomly expresses one, and only one, olfactory receptor (OR)--a phenomenon called the "one-neuron-one-receptor" rule. Although extensively studied, this rule was never proven for all ~1,000 OR genes in one cell at once, and little is known about its dynamics. Here, we directly tested this rule by single-cell transcriptomic sequencing of 178 cells from the main olfactory epithelium of adult and newborn mice. To our surprise, a subset of cells expressed multiple ORs. Most of these cells were developmentally immature. Our results illustrated how the "one-neuron-one-receptor" rule may have been established: At first, a single neuron temporarily expressed multiple ORs--seemingly violating the rule--and then all but one OR were eliminated. This work provided experimental evidence that epigenetic regulation in the olfactory system selects a single OR by suppressing a few transiently expressed ORs in a single cell during development.
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Affiliation(s)
- Longzhi Tan
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
| | - Qian Li
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - X Sunney Xie
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
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13
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Abdus-Saboor I, Fleischmann A, Shykind B. Setting limits: maintaining order in a large gene family. Transcription 2015; 5:e28978. [PMID: 25764336 PMCID: PMC4215173 DOI: 10.4161/trns.28978] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Odorant receptor (OR) gene choice is a paradigmatic example of stochastic regulation in which olfactory neurons choose one OR from > 1,000 possibilities. Recent biochemical, mathematical, and in vivo findings have revealed key players, introduced new axes of control, and brought the core mechanisms of the process into sharper focus.
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Affiliation(s)
- Ishmail Abdus-Saboor
- a Weill Cornell Medical College in Qatar; Qatar Foundation-Education City; Doha, Qatar
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14
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Abstract
The sense of smell collects vital information about the environment by detecting a multitude of chemical odorants. Breadth and sensitivity are provided by a huge number of chemosensory receptor proteins, including more than 1,400 olfactory receptors (ORs). Organizing the sensory information generated by these receptors so that it can be processed and evaluated by the central nervous system is a major challenge. This challenge is overcome by monogenic and monoallelic expression of OR genes. The single OR expressed by each olfactory sensory neuron determines the neuron's odor sensitivity and the axonal connections it will make to downstream neurons in the olfactory bulb. The expression of a single OR per neuron is accomplished by coupling a slow chromatin-mediated activation process to a fast negative-feedback signal that prevents activation of additional ORs. Singular OR activation is likely orchestrated by a network of interchromosomal enhancer interactions and large-scale changes in nuclear architecture.
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Affiliation(s)
- Kevin Monahan
- Department of Biochemistry and Molecular Biophysics, Department of Neuroscience, and Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY 10032; ,
| | - Stavros Lomvardas
- Department of Biochemistry and Molecular Biophysics, Department of Neuroscience, and Mortimer B. Zuckerman Mind, Brain, and Behavior Institute, Columbia University, New York, NY 10032; ,
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15
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Armelin-Correa LM, Nagai MH, Leme Silva AG, Malnic B. Nuclear architecture and gene silencing in olfactory sensory neurons. BIOARCHITECTURE 2015; 4:160-3. [PMID: 25714005 DOI: 10.4161/19490992.2014.982934] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Odorants are discriminated by hundreds of odorant receptor (OR) genes, which are dispersed throughout the mammalian genome. The OR genes are expressed in a highly specialized type of cell, the olfactory sensory neuron. Each one of these neurons expresses one of the 2 alleles from one single OR gene type. The mechanisms underlying OR gene expression are unclear. Here we describe recent work demonstrating that the olfactory sensory neuron shows a particular nuclear architecture, and that the genomic OR loci are colocalized in silencing heterochromatin compartments within the nucleus. These discoveries highlight the important role played by epigenetic modifications and nuclear genome organization in the regulation of OR gene expression.
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16
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Odorant receptors regulate the final glomerular coalescence of olfactory sensory neuron axons. Proc Natl Acad Sci U S A 2015; 112:5821-6. [PMID: 25902488 DOI: 10.1073/pnas.1417955112] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Odorant receptors (OR) are strongly implicated in coalescence of olfactory sensory neuron (OSN) axons and the formation of olfactory bulb (OB) glomeruli. However, when ORs are first expressed relative to basal cell division and OSN axon extension is unknown. We developed an in vivo fate-mapping strategy that enabled us to follow OSN maturation and axon extension beginning at basal cell division. In parallel, we mapped the molecular development of OSNs beginning at basal cell division, including the onset of OR expression. Our data show that ORs are first expressed around 4 d following basal cell division, 24 h after OSN axons have reached the OB. Over the next 6+ days the OSN axons navigate the OB nerve layer and ultimately coalesce in glomeruli. These data provide a previously unidentified perspective on the role of ORs in homophilic OSN axon adhesion and lead us to propose a new model dividing axon extension into two phases. Phase I is OR-independent and accounts for up to 50% of the time during which axons approach the OB and begin navigating the olfactory nerve layer. Phase II is OR-dependent and concludes as OSN axons coalesce in glomeruli.
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17
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Persuy MA, Sanz G, Tromelin A, Thomas-Danguin T, Gibrat JF, Pajot-Augy E. Mammalian olfactory receptors: molecular mechanisms of odorant detection, 3D-modeling, and structure-activity relationships. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 130:1-36. [PMID: 25623335 DOI: 10.1016/bs.pmbts.2014.11.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This chapter describes the main characteristics of olfactory receptor (OR) genes of vertebrates, including generation of this large multigenic family and pseudogenization. OR genes are compared in relation to evolution and among species. OR gene structure and selection of a given gene for expression in an olfactory sensory neuron (OSN) are tackled. The specificities of OR proteins, their expression, and their function are presented. The expression of OR proteins in locations other than the nasal cavity is regulated by different mechanisms, and ORs display various additional functions. A conventional olfactory signal transduction cascade is observed in OSNs, but individual ORs can also mediate different signaling pathways, through the involvement of other molecular partners and depending on the odorant ligand encountered. ORs are engaged in constitutive dimers. Ligand binding induces conformational changes in the ORs that regulate their level of activity depending on odorant dose. When present, odorant binding proteins induce an allosteric modulation of OR activity. Since no 3D structure of an OR has been yet resolved, modeling has to be performed using the closest G-protein-coupled receptor 3D structures available, to facilitate virtual ligand screening using the models. The study of odorant binding modes and affinities may infer best-bet OR ligands, to be subsequently checked experimentally. The relationship between spatial and steric features of odorants and their activity in terms of perceived odor quality are also fields of research that development of computing tools may enhance.
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Affiliation(s)
- Marie-Annick Persuy
- INRA UR 1197 NeuroBiologie de l'Olfaction, Domaine de Vilvert, Jouy-en-Josas, France
| | - Guenhaël Sanz
- INRA UR 1197 NeuroBiologie de l'Olfaction, Domaine de Vilvert, Jouy-en-Josas, France
| | - Anne Tromelin
- INRA UMR 1129 Flaveur, Vision et Comportement du Consommateur, Dijon, France
| | | | - Jean-François Gibrat
- INRA UR1077 Mathématique Informatique et Génome, Domaine de Vilvert, Jouy-en-Josas, France
| | - Edith Pajot-Augy
- INRA UR 1197 NeuroBiologie de l'Olfaction, Domaine de Vilvert, Jouy-en-Josas, France.
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18
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Abstract
Odorants are detected by odorant receptors, which are located on olfactory sensory neurons of the nose. Each olfactory sensory neuron expresses one single odorant receptor gene allele from a large family of odorant receptor genes. To gain insight into the mechanisms underlying this monogenic and monoallelic expression, we examined the 3D nuclear organization of olfactory sensory neurons and determined the positions of homologous odorant receptor gene alleles in relation to different nuclear compartments. Our results show that olfactory neurons exhibit a singular nuclear architecture that is characterized by a large centrally localized constitutive heterochromatin block and by the presence of prominent facultative heterochromatin domains that are localized around this constitutive heterochromatin block. We also found that the two homologous alleles of a given odorant receptor gene are frequently segregated to separate compartments in the nucleus, with one of the alleles localized to the constitutive heterochromatin block and the other one localized to the more plastic facultative heterochromatin, or next to it. Our findings suggest that this nuclear compartmentalization may play a critical role in the expression of odorant receptor genes.
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Dalton RP, Lyons DB, Lomvardas S. Co-opting the unfolded protein response to elicit olfactory receptor feedback. Cell 2013; 155:321-32. [PMID: 24120133 DOI: 10.1016/j.cell.2013.09.033] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 09/10/2013] [Accepted: 09/19/2013] [Indexed: 11/19/2022]
Abstract
Olfactory receptor (OR) expression requires the transcriptional activation of 1 out of 1,000s of OR alleles and a feedback signal that preserves this transcriptional choice. The mechanism by which olfactory sensory neurons (OSNs) detect ORs to signal to the nucleus remains elusive. Here, we show that OR proteins generate this feedback by activating the unfolded protein response (UPR). OR expression induces Perk-mediated phosphorylation of the translation initiation factor eif2α causing selective translation of activating transcription factor 5 (ATF5). ATF5 induces the transcription of adenylyl cyclase 3 (Adcy3), which relieves the UPR. Our data provide a role for the UPR in defining neuronal identity and cell fate commitment and support a two-step model for the feedback signal: (1) OR protein, as a stress stimulus, alters the translational landscape of the OSN and induces Adcy3 expression; (2), Adcy3 relieves that stress, restores global translation, and makes OR choice permanent.
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Affiliation(s)
- Ryan P Dalton
- Department of Anatomy, University of California San Francisco, San Francisco, CA 94158, USA; Neuroscience Graduate Program, University of California San Francisco, San Francisco, CA 94158, USA
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