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Iijima Y, Miki R, Takasugi N, Fujimura M, Uehara T. Characterization of pathological changes in the olfactory system of mice exposed to methylmercury. Arch Toxicol 2024; 98:1163-1175. [PMID: 38367039 PMCID: PMC10944439 DOI: 10.1007/s00204-024-03682-w] [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: 11/07/2023] [Accepted: 01/15/2024] [Indexed: 02/19/2024]
Abstract
Methylmercury (MeHg) is a well-known environmental neurotoxicant that causes severe brain disorders such as Minamata disease. Although some patients with Minamata disease develop olfactory dysfunction, the underlying pathomechanism is largely unknown. We examined the effects of MeHg on the olfactory system using a model of MeHg poisoning in which mice were administered 30 ppm MeHg in drinking water for 8 weeks. Mice exposed to MeHg displayed significant mercury accumulation in the olfactory pathway, including the nasal mucosa, olfactory bulb, and olfactory cortex. The olfactory epithelium was partially atrophied, and olfactory sensory neurons were diminished. The olfactory bulb exhibited an increase in apoptotic cells, hypertrophic astrocytes, and amoeboid microglia, mainly in the granular cell layer. Neuronal cell death was observed in the olfactory cortex, particularly in the ventral tenia tecta. Neuronal cell death was also remarkable in higher-order areas such as the orbitofrontal cortex. Correlation analysis showed that neuronal loss in the olfactory cortex was strongly correlated with the plasma mercury concentration. Our results indicate that MeHg is an olfactory toxicant that damages the central regions involved in odor perception. The model described herein is useful for analyzing the mechanisms and treatments of olfactory dysfunction in MeHg-intoxicated patients.
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Affiliation(s)
- Yuta Iijima
- Department of Medicinal Pharmacology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700‑8530, Japan
| | - Ryohei Miki
- Department of Medicinal Pharmacology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700‑8530, Japan
| | - Nobumasa Takasugi
- Department of Medicinal Pharmacology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700‑8530, Japan
| | - Masatake Fujimura
- Department of Basic Medical Science, National Institute for Minamata Disease, Kumamoto, 867‑0008, Japan
| | - Takashi Uehara
- Department of Medicinal Pharmacology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, 700‑8530, Japan.
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Yuhan L, Khaleghi Ghadiri M, Gorji A. Impact of NQO1 dysregulation in CNS disorders. J Transl Med 2024; 22:4. [PMID: 38167027 PMCID: PMC10762857 DOI: 10.1186/s12967-023-04802-3] [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: 07/08/2023] [Accepted: 12/12/2023] [Indexed: 01/05/2024] Open
Abstract
NAD(P)H Quinone Dehydrogenase 1 (NQO1) plays a pivotal role in the regulation of neuronal function and synaptic plasticity, cellular adaptation to oxidative stress, neuroinflammatory and degenerative processes, and tumorigenesis in the central nervous system (CNS). Impairment of the NQO1 activity in the CNS can result in abnormal neurotransmitter release and clearance, increased oxidative stress, and aggravated cellular injury/death. Furthermore, it can cause disturbances in neural circuit function and synaptic neurotransmission. The abnormalities of NQO1 enzyme activity have been linked to the pathophysiological mechanisms of multiple neurological disorders, including Parkinson's disease, Alzheimer's disease, epilepsy, multiple sclerosis, cerebrovascular disease, traumatic brain injury, and brain malignancy. NQO1 contributes to various dimensions of tumorigenesis and treatment response in various brain tumors. The precise mechanisms through which abnormalities in NQO1 function contribute to these neurological disorders continue to be a subject of ongoing research. Building upon the existing knowledge, the present study reviews current investigations describing the role of NQO1 dysregulations in various neurological disorders. This study emphasizes the potential of NQO1 as a biomarker in diagnostic and prognostic approaches, as well as its suitability as a target for drug development strategies in neurological disorders.
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Affiliation(s)
- Li Yuhan
- Epilepsy Research Center, Münster University, Münster, Germany
- Department of Breast Surgery, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | | | - Ali Gorji
- Epilepsy Research Center, Münster University, Münster, Germany.
- Department of Neurosurgery, Münster University, Münster, Germany.
- Shefa Neuroscience Research Center, Khatam Alanbia Hospital, Tehran, Iran.
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
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3
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LaFever BJ, Imamura F. Effects of nasal inflammation on the olfactory bulb. J Neuroinflammation 2022; 19:294. [PMID: 36494744 PMCID: PMC9733073 DOI: 10.1186/s12974-022-02657-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 11/24/2022] [Indexed: 12/13/2022] Open
Abstract
Sinonasal diseases, such as rhinosinusitis, affect up to 12% of individuals each year which constitutes these diseases as some of the most common medical conditions in the world. Exposure to environmental pathogens and toxicants via the nasal cavity can result in a severe inflammatory state commonly observed in these conditions. It is well understood that the epithelial and neuronal cells lining the olfactory mucosa, including olfactory sensory neurons (OSNs), are significantly damaged in these diseases. Prolonged inflammation of the nasal cavity may also lead to hyposmia or anosmia. Although various environmental agents induce inflammation in different ways via distinct cellular and molecular interactions, nasal inflammation has similar consequences on the structure and homeostatic function of the olfactory bulb (OB) which is the first relay center for olfactory information in the brain. Atrophy of the OB occurs via thinning of the superficial OB layers including the olfactory nerve layer, glomerular layer, and superficial external plexiform layer. Intrabulbar circuits of the OB which include connectivity between OB projection neurons, OSNs, and interneurons become significantly dysregulated in which synaptic pruning and dendritic retraction take place. Furthermore, glial cells and other immune cells become hyperactivated and induce a state of inflammation in the OB which results in upregulated cytokine production. Moreover, many of these features of nasal inflammation are present in the case of SARS-CoV-2 infection. This review summarizes the impact of nasal inflammation on the morphological and physiological features of the rodent OB.
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Affiliation(s)
- Brandon J. LaFever
- grid.240473.60000 0004 0543 9901Department of Pharmacology, Penn State College of Medicine, 500 University Dr., Hershey, PA 17033 USA
| | - Fumiaki Imamura
- grid.240473.60000 0004 0543 9901Department of Pharmacology, Penn State College of Medicine, 500 University Dr., Hershey, PA 17033 USA
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Han B, Kikuta S, Kamogashira T, Kondo K, Yamasoba T. Sleep deprivation induces delayed regeneration of olfactory sensory neurons following injury. Front Neurosci 2022; 16:1029279. [DOI: 10.3389/fnins.2022.1029279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Accepted: 11/16/2022] [Indexed: 12/05/2022] Open
Abstract
The circadian system, which is essential for the alignment of sleep/wake cycles, modulates adult neurogenesis. The olfactory epithelium (OE) has the ability to generate new neurons throughout life. Loss of olfactory sensory neurons (OSNs) as a result of injury to the OE triggers the generation of new OSNs, which are incorporated into olfactory circuits to restore olfactory sensory perception. This regenerative potential means that it is likely that the OE is substantially affected by sleep deprivation (SD), although how this may occur remains unclear. The aim of this study is to address how SD affects the process of OSN regeneration following OE injury. Mice were subjected to SD for 2 weeks, which induced changes in circadian activity. This condition resulted in decreased activity during the night-time and increased activity during the daytime, and induced no histological changes in the OE. However, when subjected to SD during the regeneration process after OE injury, a significant decrease in the number of mature OSNs in the dorsomedial area of the OE, which is the only area containing neurons expressing NQO1 (quinone dehydrogenase 1), was observed compared to the NQO1-negative OE. Furthermore, a significant decrease in proliferating basal cells was observed in the NQO1-positive OE compared to the NQO1-negative OE, but no increase in apoptotic OSNs was observed. These results indicate that SD accompanied by disturbed circadian activity could induce structurally negative effects on OSN regeneration, preferentially in the dorsomedial area of the OE, and that this area-specific regeneration delay might involve the biological activity of NQO1.
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Ueha R, Ito T, Ueha S, Furukawa R, Kitabatake M, Ouji-Sageshima N, Uranaka T, Tanaka H, Nishijima H, Kondo K, Yamasoba T. Evidence for the spread of SARS-CoV-2 and olfactory cell lineage impairment in close-contact infection Syrian hamster models. Front Cell Infect Microbiol 2022; 12:1019723. [PMCID: PMC9634532 DOI: 10.3389/fcimb.2022.1019723] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 10/11/2022] [Indexed: 01/08/2023] Open
Abstract
Objectives Close contact with patients with COVID-19 is speculated to be the most common cause of viral transmission, but the pathogenesis of COVID-19 by close contact remains to be elucidated. In addition, despite olfactory impairment being a unique complication of COVID-19, the impact of SARS-CoV-2 on the olfactory cell lineage has not been fully validated. This study aimed to elucidate close-contact viral transmission to the nose and lungs and to investigate the temporal damage in the olfactory receptor neuron (ORN) lineage caused by SARS-CoV-2. Methods Syrian hamsters were orally administered SARS-CoV-2 nonvariant nCoV-19/JPN/TY/WK521/2020 as direct-infection models. On day 3 after inoculation, infected and uninfected hamsters were housed in the same cage for 30 minutes. These uninfected hamsters were subsequently assigned to a close-contact group. First, viral presence in the nose and lungs was verified in the infection and close-contact groups at several time points. Next, the impacts on the olfactory epithelium, including olfactory progenitors, immature ORNs, and mature ORNs were examined histologically. Then, the viral transmission status and chronological changes in tissue damage were compared between the direct-infection and close-contact groups. Results In the close-contact group, viral presence could not be detected in both the nose and lungs on day 3, and the virus was identified in both tissues on day 7. In the direct-infection group, the viral load was highest in the nose and lungs on day 3, decreased on day 7, and was no longer detectable on day 14. Histologically, in the direct-infection group, mature ORNs were most depleted on day 3 (p <0.001) and showed a recovery trend on day 14, with similar trends for olfactory progenitors and immature ORNs. In the close-contact group, there was no obvious tissue damage on day 3, but on day 7, the number of all ORN lineage cells significantly decreased (p <0.001). Conclusion SARS-CoV-2 was transmitted even after brief contact and subsequent olfactory epithelium and lung damage occurred more than 3 days after the trigger of infection. The present study also indicated that SARS-CoV-2 damages all ORN lineage cells, but this damage can begin to recover approximately 14 days post infection.
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Affiliation(s)
- Rumi Ueha
- Swallowing Center, The University of Tokyo Hospital, Tokyo, Japan
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
- *Correspondence: Rumi Ueha, ;
| | - Toshihiro Ito
- Department of Immunology, Nara Medical University, Nara, Japan
| | - Satoshi Ueha
- Division of Molecular Regulation of Inflammatory and Immune Diseases, Research Institute for Biomedical Sciences, Tokyo University of Science, Chiba, Japan
| | | | | | | | - Tsukasa Uranaka
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Hirotaka Tanaka
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
- Department of Otorhinolaryngology, The Jikei University School of Medicine, Tokyo, Japan
| | - Hironobu Nishijima
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kenji Kondo
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
| | - Tatsuya Yamasoba
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
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6
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Ueha R, Ito T, Furukawa R, Kitabatake M, Ouji-Sageshima N, Ueha S, Koyama M, Uranaka T, Kondo K, Yamasoba T. Oral SARS-CoV-2 Inoculation Causes Nasal Viral Infection Leading to Olfactory Bulb Infection: An Experimental Study. Front Cell Infect Microbiol 2022; 12:924725. [PMID: 35770069 PMCID: PMC9234459 DOI: 10.3389/fcimb.2022.924725] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 05/19/2022] [Indexed: 12/26/2022] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections can cause long-lasting anosmia, but the impact of SARS-CoV-2 infection, which can spread to the nasal cavity via the oral route, on the olfactory receptor neuron (ORN) lineage and olfactory bulb (OB) remains undetermined. Using Syrian hamsters, we explored whether oral SARS-CoV-2 inoculation can lead to nasal viral infection, examined how SARS-CoV-2 affects the ORN lineage by site, and investigated whether SARS-CoV-2 infection can spread to the OB and induce inflammation. On post-inoculation day 7, SARS-CoV-2 presence was confirmed in the lateral area (OCAM-positive) but not the nasal septum of NQO1-positive and OCAM-positive areas. The virus was observed partially infiltrating the olfactory epithelium, and ORN progenitor cells, immature ORNs, and mature ORNs were fewer than in controls. The virus was found in the olfactory nerve bundles to the OB, suggesting the nasal cavity as a route for SARS-CoV-2 brain infection. We demonstrated that transoral SARS-CoV-2 infection can spread from the nasal cavity to the central nervous system and the possibility of central olfactory dysfunction due to SARS-CoV-2 infection. The virus was localized at the infection site and could damage all ORN-lineage cells.
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Affiliation(s)
- Rumi Ueha
- Swallowing Center, the University of Tokyo Hospital, Tokyo, Japan
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, the University of Tokyo, Tokyo, Japan
- *Correspondence: Rumi Ueha, ;
| | - Toshihiro Ito
- Department of Immunology, Nara Medical University, Nara, Japan
| | | | | | | | - Satoshi Ueha
- Division of Molecular Regulation of Inflammatory and Immune Diseases, Research Institute for Biomedical Sciences, Tokyo University of Science, Chiba, Japan
| | - Misaki Koyama
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, the University of Tokyo, Tokyo, Japan
| | - Tsukasa Uranaka
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, the University of Tokyo, Tokyo, Japan
| | - Kenji Kondo
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, the University of Tokyo, Tokyo, Japan
| | - Tatsuya Yamasoba
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, the University of Tokyo, Tokyo, Japan
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7
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Dorrego-Rivas A, Grubb MS. Developing and maintaining a nose-to-brain map of odorant identity. Open Biol 2022; 12:220053. [PMID: 35765817 PMCID: PMC9240688 DOI: 10.1098/rsob.220053] [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: 02/16/2022] [Accepted: 05/24/2022] [Indexed: 01/04/2023] Open
Abstract
Olfactory sensory neurons (OSNs) in the olfactory epithelium of the nose transduce chemical odorant stimuli into electrical signals. These signals are then sent to the OSNs' target structure in the brain, the main olfactory bulb (OB), which performs the initial stages of sensory processing in olfaction. The projection of OSNs to the OB is highly organized in a chemospatial map, whereby axon terminals from OSNs expressing the same odorant receptor (OR) coalesce into individual spherical structures known as glomeruli. This nose-to-brain map of odorant identity is built from late embryonic development to early postnatal life, through a complex combination of genetically encoded, OR-dependent and activity-dependent mechanisms. It must then be actively maintained throughout adulthood as OSNs experience turnover due to external insult and ongoing neurogenesis. Our review describes and discusses these two distinct and crucial processes in olfaction, focusing on the known mechanisms that first establish and then maintain chemospatial order in the mammalian OSN-to-OB projection.
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Affiliation(s)
- Ana Dorrego-Rivas
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
| | - Matthew S. Grubb
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE1 1UL, UK
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Kishimoto-Urata M, Urata S, Kagoya R, Imamura F, Nagayama S, Reyna RA, Maruyama J, Yamasoba T, Kondo K, Hasegawa-Ishii S, Paessler S. Prolonged and extended impacts of SARS-CoV-2 on the olfactory neurocircuit. Sci Rep 2022; 12:5728. [PMID: 35388072 PMCID: PMC8987081 DOI: 10.1038/s41598-022-09731-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 03/21/2022] [Indexed: 12/27/2022] Open
Abstract
The impact of SARS-CoV-2 on the olfactory pathway was studied over several time points using Syrian golden hamsters. We found an incomplete recovery of the olfactory sensory neurons, prolonged activation of glial cells in the olfactory bulb, and a decrease in the density of dendritic spines within the hippocampus. These data may be useful for elucidating the mechanism underlying long-lasting olfactory dysfunction and cognitive impairment as a post-acute COVID-19 syndrome.
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Affiliation(s)
- Megumi Kishimoto-Urata
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, USA
- Department of Otolaryngology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Shinji Urata
- Department of Otolaryngology, University of Texas Medical Branch, Galveston, TX, USA
- Department of Otolaryngology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Ryoji Kagoya
- Department of Otolaryngology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Fumiaki Imamura
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA, USA
| | - Shin Nagayama
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Rachel A Reyna
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, USA
| | - Junki Maruyama
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, USA
| | - Tatsuya Yamasoba
- Department of Otolaryngology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Kenji Kondo
- Department of Otolaryngology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
| | | | - Slobodan Paessler
- Department of Otolaryngology, University of Texas Medical Branch, Galveston, TX, USA.
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Ruiz Tejada Segura ML, Abou Moussa E, Garabello E, Nakahara TS, Makhlouf M, Mathew LS, Wang L, Valle F, Huang SSY, Mainland JD, Caselle M, Osella M, Lorenz S, Reisert J, Logan DW, Malnic B, Scialdone A, Saraiva LR. A 3D transcriptomics atlas of the mouse nose sheds light on the anatomical logic of smell. Cell Rep 2022; 38:110547. [PMID: 35320714 PMCID: PMC8995392 DOI: 10.1016/j.celrep.2022.110547] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 01/26/2022] [Accepted: 03/01/2022] [Indexed: 12/26/2022] Open
Abstract
The sense of smell helps us navigate the environment, but its molecular architecture and underlying logic remain understudied. The spatial location of odorant receptor genes (Olfrs) in the nose is thought to be independent of the structural diversity of the odorants they detect. Using spatial transcriptomics, we create a genome-wide 3D atlas of the mouse olfactory mucosa (OM). Topographic maps of genes differentially expressed in space reveal that both Olfrs and non-Olfrs are distributed in a continuous and overlapping fashion over at least five broad zones in the OM. The spatial locations of Olfrs correlate with the mucus solubility of the odorants they recognize, providing direct evidence for the chromatographic theory of olfaction. This resource resolves the molecular architecture of the mouse OM and will inform future studies on mechanisms underlying Olfr gene choice, axonal pathfinding, patterning of the nervous system, and basic logic for the peripheral representation of smell.
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Affiliation(s)
- Mayra L Ruiz Tejada Segura
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Feodor-Lynen-Strasse 21, 81377 München, Germany; Institute of Functional Epigenetics, Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany; Institute of Computational Biology, Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | | | - Elisa Garabello
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Feodor-Lynen-Strasse 21, 81377 München, Germany; Physics Department, University of Turin and INFN, Via P. Giuria 1, 10125 Turin, Italy; Department of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Thiago S Nakahara
- Department of Biochemistry, University of São Paulo, São Paulo, Brazil
| | | | | | - Li Wang
- Sidra Medicine, P.O. Box 26999, Doha, Qatar
| | - Filippo Valle
- Physics Department, University of Turin and INFN, Via P. Giuria 1, 10125 Turin, Italy
| | | | - Joel D Mainland
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA; Department of Neuroscience, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Michele Caselle
- Physics Department, University of Turin and INFN, Via P. Giuria 1, 10125 Turin, Italy
| | - Matteo Osella
- Physics Department, University of Turin and INFN, Via P. Giuria 1, 10125 Turin, Italy
| | - Stephan Lorenz
- Sidra Medicine, P.O. Box 26999, Doha, Qatar; Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SD, UK
| | - Johannes Reisert
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Darren W Logan
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SD, UK
| | - Bettina Malnic
- Department of Biochemistry, University of São Paulo, São Paulo, Brazil
| | - Antonio Scialdone
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Feodor-Lynen-Strasse 21, 81377 München, Germany; Institute of Functional Epigenetics, Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany; Institute of Computational Biology, Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
| | - Luis R Saraiva
- Sidra Medicine, P.O. Box 26999, Doha, Qatar; Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA; College of Health and Life Sciences, Hamad Bin Khalifa University, P.O. Box 34110, Doha, Qatar.
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10
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Aoki M, Gamayun I, Wyatt A, Grünewald R, Simon-Thomas M, Philipp SE, Hummel O, Wagenpfeil S, Kattler K, Gasparoni G, Walter J, Qiao S, Grattan DR, Boehm U. Prolactin-sensitive olfactory sensory neurons regulate male preference in female mice by modulating responses to chemosensory cues. SCIENCE ADVANCES 2021; 7:eabg4074. [PMID: 34623921 PMCID: PMC8500514 DOI: 10.1126/sciadv.abg4074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 08/19/2021] [Indexed: 06/10/2023]
Abstract
Chemosensory cues detected in the nose need to be integrated with the hormonal status to trigger appropriate behaviors, but the neural circuits linking the olfactory and the endocrine system are insufficiently understood. Here, we characterize olfactory sensory neurons in the murine nose that respond to the pituitary hormone prolactin. Deletion of prolactin receptor in these cells results in impaired detection of social odors and blunts male preference in females. The prolactin-responsive olfactory sensory neurons exhibit a distinctive projection pattern to the brain that is similar across different individuals and express a limited subset of chemosensory receptors. Prolactin modulates the responses within these neurons to discrete chemosensory cues contained in male urine, providing a mechanism by which the hormonal status can be directly linked with distinct olfactory cues to generate appropriate behavioral responses.
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Affiliation(s)
- Mari Aoki
- Department of Pharmacology, Center for Molecular Signaling (PZMS), Saarland University School of Medicine, Homburg, Germany
| | - Igor Gamayun
- Department of Pharmacology, Center for Molecular Signaling (PZMS), Saarland University School of Medicine, Homburg, Germany
| | - Amanda Wyatt
- Department of Pharmacology, Center for Molecular Signaling (PZMS), Saarland University School of Medicine, Homburg, Germany
| | - Ramona Grünewald
- Department of Pharmacology, Center for Molecular Signaling (PZMS), Saarland University School of Medicine, Homburg, Germany
| | - Martin Simon-Thomas
- Department of Pharmacology, Center for Molecular Signaling (PZMS), Saarland University School of Medicine, Homburg, Germany
| | - Stephan E. Philipp
- Department of Pharmacology, Center for Molecular Signaling (PZMS), Saarland University School of Medicine, Homburg, Germany
| | - Oliver Hummel
- Faculty of Computer Science, Mannheim University of Applied Sciences, Mannheim, Germany
| | - Stefan Wagenpfeil
- Institute for Medical Biometry, Epidemiology and Medical Informatics, Saarland University School of Medicine, Homburg, Germany
| | - Kathrin Kattler
- Department of Genetics, Saarland University, Saarbrücken, Germany
| | - Gilles Gasparoni
- Department of Genetics, Saarland University, Saarbrücken, Germany
| | - Jörn Walter
- Department of Genetics, Saarland University, Saarbrücken, Germany
| | - Sen Qiao
- Department of Pharmacology, Center for Molecular Signaling (PZMS), Saarland University School of Medicine, Homburg, Germany
| | - David R. Grattan
- Centre for Neuroendocrinology and Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Ulrich Boehm
- Department of Pharmacology, Center for Molecular Signaling (PZMS), Saarland University School of Medicine, Homburg, Germany
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11
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Joseph KB, Awadallah N, Delay ER, Delay RJ. Transient Effects of Cyclophosphamide on Basal Cell Proliferation of Olfactory Epithelia. Chem Senses 2021; 45:549-561. [PMID: 32531016 DOI: 10.1093/chemse/bjaa039] [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] [Indexed: 02/06/2023] Open
Abstract
Cancer is often treated with broad-spectrum cytotoxic drugs that not only eradicate cancerous cells but also have detrimental side effects. One of these side effects, disruption of the olfactory system, impedes a patient's ability to smell, perceive flavor, and ultimately may interfere with their nutritional intake and recovery from cancer. Recent studies reported that the chemotherapy drug, cyclophosphamide (CYP), can damage gustatory epithelia and disrupt cell proliferation in olfactory epithelia. In this study, we asked if CYP altered globose and horizontal basal cell proliferation in the murine main olfactory epithelium (MOE) and vomeronasal organ (VNO). We used antibodies for Ki67, a marker strictly associated with cell proliferation, and Keratin 5, a marker for the cytoskeleton of horizontal basal cells. Our results revealed a significant CYP-induced decrease in the number of proliferative cells in both epithelia, especially globose basal cells in the MOE, within the first 1-2 days postinjection. Recovery of cell renewal was apparent 6 days after injection. The immunohistochemical markers showed significantly higher levels of globose and horizontal basal cell proliferation in CYP-injected mice at 14 and 30 days postinjection compared with control mice. The prolonged proliferative activation of globose and horizontal basal cells suggests that, besides altering proliferation of olfactory epithelia, the epithelial substrate needed for successful cell renewal may be adversely affected by CYP.
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Affiliation(s)
- Kyle B Joseph
- Department of Biology and Vermont Chemosensory Group, University of Vermont, Burlington, VT, USA.,Department of Bio-Medical Sciences, Philadelphia College of Osteopathic Medicine, Philadelphia, PA, USA
| | - Nora Awadallah
- Department of Biology and Vermont Chemosensory Group, University of Vermont, Burlington, VT, USA.,City University of New York (CUNY) Neuroscience Collaborative, CUNY Graduate Center, New York City, NY, USA.,Department of Molecular, Cellular and Biomedical Sciences, The CUNY School of Medicine, City College, The City University of New York, New York City, NY, USA
| | - Eugene R Delay
- Department of Biology and Vermont Chemosensory Group, University of Vermont, Burlington, VT, USA
| | - Rona J Delay
- Department of Biology and Vermont Chemosensory Group, University of Vermont, Burlington, VT, USA
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12
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Zapiec B, Mombaerts P. The Zonal Organization of Odorant Receptor Gene Choice in the Main Olfactory Epithelium of the Mouse. Cell Rep 2021; 30:4220-4234.e5. [PMID: 32209480 DOI: 10.1016/j.celrep.2020.02.110] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 01/16/2020] [Accepted: 02/27/2020] [Indexed: 12/15/2022] Open
Abstract
A mature olfactory sensory neuron (OSN) of the main olfactory epithelium (MOE) typically expresses one allele of one odorant receptor (OR) gene. It is widely thought that the great majority of the 1,141 intact mouse OR genes are expressed in one of four MOE zones (or bands or stripes), which are largely non-overlapping. Here, we develop a multiplex method to map, in 3D and MOE-wide, the expression areas of multiple OR genes in individual, non-genetically modified mice by three-color fluorescence in situ hybridization, semi-automated image segmentation, and 3D reconstruction. We classify the expression areas of 68 OR genes into 9 zones. These zones are highly overlapping and strikingly complex when viewed in 3D reconstructions. There could well be more zones. We propose that zones reflect distinct OSN types that are each restricted in their choice to a subset of the OR gene repertoire.
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Affiliation(s)
- Bolek Zapiec
- Max Planck Research Unit for Neurogenetics, Max-von-Laue-Strasse 4, 60438 Frankfurt, Germany
| | - Peter Mombaerts
- Max Planck Research Unit for Neurogenetics, Max-von-Laue-Strasse 4, 60438 Frankfurt, Germany.
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13
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Chen Y, Ding X, Wang S, Ding P, Xu Z, Li J, Wang M, Xiang R, Wang X, Wang H, Feng Q, Qiu J, Wang F, Huang Z, Zhang X, Tang G, Tang S. A single-cell atlas of mouse olfactory bulb chromatin accessibility. J Genet Genomics 2021; 48:147-162. [PMID: 33926839 DOI: 10.1016/j.jgg.2021.02.007] [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: 08/06/2020] [Revised: 01/26/2021] [Accepted: 02/01/2021] [Indexed: 10/21/2022]
Abstract
Olfaction, the sense of smell, is a fundamental trait crucial to many species. The olfactory bulb (OB) plays pivotal roles in processing and transmitting odor information from the environment to the brain. The cellular heterogeneity of the mouse OB has been studied using single-cell RNA sequencing. However, the epigenetic landscape of the mOB remains mostly unexplored. Herein, we apply single-cell assay for transposase-accessible chromatin sequencing to profile the genome-wide chromatin accessibility of 9,549 single cells from the mOB. Based on single-cell epigenetic signatures, mOB cells are classified into 21 clusters corresponding to 11 cell types. We identify distinct sets of putative regulatory elements specific to each cell cluster from which putative target genes and enriched potential functions are inferred. In addition, the transcription factor motifs enriched in each cell cluster are determined to indicate the developmental fate of each cell lineage. Our study provides a valuable epigenetic data set for the mOB at single-cell resolution, and the results can enhance our understanding of regulatory circuits and the therapeutic capacity of the OB at the single-cell level.
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Affiliation(s)
- Yin Chen
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Xiangning Ding
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Shiyou Wang
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Peiwen Ding
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Zaoxu Xu
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Jiankang Li
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China
| | - Mingyue Wang
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Rong Xiang
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Xiaoling Wang
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Haoyu Wang
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Qikai Feng
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Jiaying Qiu
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China
| | - Feiyue Wang
- BGI Education Center, University of Chinese Academy of Sciences, Shenzhen 518083, China; BGI-Shenzhen, Shenzhen 518083, China; School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, China
| | - Zhen Huang
- Southern Center for Biomedical Research and Fujian Key Laboratory of Developmental and Neural Biology, College of Life Sciences, Fujian Normal University, Fuzhou, Fujian 350117, China
| | - Xingliang Zhang
- Shenzhen Children's Hospital, Shenzhen 518083, China; Department of Pediatrics, the Affiliated Hospital of Guangdong Medical University, Zhanjiang 524000, China.
| | - Gen Tang
- Shenzhen Children's Hospital, Shenzhen 518083, China.
| | - Shengping Tang
- Shenzhen Children's Hospital, Shenzhen 518083, China; Zunyi Medical University, Zunyi, Guizhou 563099, China; China Medical University, Shenyang, Liaoning 110122, China.
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14
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Fodoulian L, Tuberosa J, Rossier D, Boillat M, Kan C, Pauli V, Egervari K, Lobrinus JA, Landis BN, Carleton A, Rodriguez I. SARS-CoV-2 Receptors and Entry Genes Are Expressed in the Human Olfactory Neuroepithelium and Brain. iScience 2020; 23:101839. [PMID: 33251489 PMCID: PMC7685946 DOI: 10.1016/j.isci.2020.101839] [Citation(s) in RCA: 120] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/25/2020] [Accepted: 11/18/2020] [Indexed: 12/21/2022] Open
Abstract
Reports indicate an association between COVID-19 and anosmia, as well as the presence of SARS-CoV-2 virions in the olfactory bulb. To test whether the olfactory neuroepithelium may represent a target of the virus, we generated RNA-seq libraries from human olfactory neuroepithelia, in which we found substantial expression of the genes coding for the virus receptor angiotensin-converting enzyme-2 (ACE2) and for the virus internalization enhancer TMPRSS2. We analyzed a human olfactory single-cell RNA-seq dataset and determined that sustentacular cells, which maintain the integrity of olfactory sensory neurons, express ACE2 and TMPRSS2. ACE2 protein was highly expressed in a subset of sustentacular cells in human and mouse olfactory tissues. Finally, we found ACE2 transcripts in specific brain cell types, both in mice and humans. Sustentacular cells thus represent a potential entry door for SARS-CoV-2 in a neuronal sensory system that is in direct connection with the brain.
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Affiliation(s)
- Leon Fodoulian
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
- Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva, Switzerland
| | - Joël Tuberosa
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Daniel Rossier
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Madlaina Boillat
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Chenda Kan
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Véronique Pauli
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Kristof Egervari
- Service of Clinical Pathology, Department of Genetic Medicine, Geneva University Hospitals, Geneva, Switzerland
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva, Switzerland
| | - Johannes A. Lobrinus
- Service of Clinical Pathology, Department of Genetic Medicine, Geneva University Hospitals, Geneva, Switzerland
| | - Basile N. Landis
- Rhinology-Olfactology Unit, Department of Otorhinolaryngology, Head and Neck Surgery, Geneva University Hospitals, Geneva, Switzerland
| | - Alan Carleton
- Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva, Switzerland
| | - Ivan Rodriguez
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
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15
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Fodoulian L, Tuberosa J, Rossier D, Boillat M, Kan C, Pauli V, Egervari K, Lobrinus JA, Landis BN, Carleton A, Rodriguez I. SARS-CoV-2 Receptors and Entry Genes Are Expressed in the Human Olfactory Neuroepithelium and Brain. iScience 2020; 23:101839. [PMID: 33251489 DOI: 10.1101/2020.03.31.013268] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/25/2020] [Accepted: 11/18/2020] [Indexed: 05/23/2023] Open
Abstract
Reports indicate an association between COVID-19 and anosmia, as well as the presence of SARS-CoV-2 virions in the olfactory bulb. To test whether the olfactory neuroepithelium may represent a target of the virus, we generated RNA-seq libraries from human olfactory neuroepithelia, in which we found substantial expression of the genes coding for the virus receptor angiotensin-converting enzyme-2 (ACE2) and for the virus internalization enhancer TMPRSS2. We analyzed a human olfactory single-cell RNA-seq dataset and determined that sustentacular cells, which maintain the integrity of olfactory sensory neurons, express ACE2 and TMPRSS2. ACE2 protein was highly expressed in a subset of sustentacular cells in human and mouse olfactory tissues. Finally, we found ACE2 transcripts in specific brain cell types, both in mice and humans. Sustentacular cells thus represent a potential entry door for SARS-CoV-2 in a neuronal sensory system that is in direct connection with the brain.
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Affiliation(s)
- Leon Fodoulian
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
- Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva, Switzerland
| | - Joël Tuberosa
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Daniel Rossier
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Madlaina Boillat
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Chenda Kan
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Véronique Pauli
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
| | - Kristof Egervari
- Service of Clinical Pathology, Department of Genetic Medicine, Geneva University Hospitals, Geneva, Switzerland
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva, Switzerland
| | - Johannes A Lobrinus
- Service of Clinical Pathology, Department of Genetic Medicine, Geneva University Hospitals, Geneva, Switzerland
| | - Basile N Landis
- Rhinology-Olfactology Unit, Department of Otorhinolaryngology, Head and Neck Surgery, Geneva University Hospitals, Geneva, Switzerland
| | - Alan Carleton
- Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva, Switzerland
| | - Ivan Rodriguez
- Department of Genetics and Evolution, Faculty of Sciences, University of Geneva, quai Ernest-Ansermet 30, 1211 Geneva, Switzerland
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16
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Tuerdi A, Kikuta S, Kinoshita M, Kamogashira T, Kondo K, Yamasoba T. Zone-specific damage of the olfactory epithelium under protein restriction. Sci Rep 2020; 10:22175. [PMID: 33335225 PMCID: PMC7746724 DOI: 10.1038/s41598-020-79249-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 12/03/2020] [Indexed: 12/11/2022] Open
Abstract
Oxidative stress causes tissue damage, affecting age-related pathologies. Protein restriction (PR) provides a powerful intervention strategy for reducing oxidative stress, which may have a positive effect on individual organs. However, it is unknown whether PR intervention influences the olfactory system. Here, we investigated how 10 months of PR could affect the cell dynamics of the olfactory epithelium (OE) in mice. We found that PR reduced age-related loss of outer hair cells in the cochlea, providing preventive effects against age-related hearing loss. In contrast, PR resulted in reduced mature olfactory sensory neurons (OSNs), increased proliferative basal cells, and increased apoptotic OSNs in zone 1 (the only area containing neurons expressing NQO1 [quinone dehydrogenase 1]) of the OE in comparison with animals given a control diet. Substantial oxidative stress occurred in NQO1-positive cells and induced apoptotic OSNs in zone 1. These results indicate that in contrast to the positive effect on the auditory system, PR induces oxidative stress and structurally and functionally negative effects on OSNs in zone 1, which is probably involved in the bioactivation of NQO1.
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Affiliation(s)
- Ayinuer Tuerdi
- Department of Otolaryngology and Head and Neck Surgery, The Second Xiangya Hospital, Central South University, 139 Renmin Road, Changsha, 410011, Hunan, China
| | - Shu Kikuta
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
| | - Makoto Kinoshita
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Teru Kamogashira
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Kenji Kondo
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Tatsuya Yamasoba
- Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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17
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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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18
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Cooper KW, Brann DH, Farruggia MC, Bhutani S, Pellegrino R, Tsukahara T, Weinreb C, Joseph PV, Larson ED, Parma V, Albers MW, Barlow LA, Datta SR, Di Pizio A. COVID-19 and the Chemical Senses: Supporting Players Take Center Stage. Neuron 2020; 107:219-233. [PMID: 32640192 PMCID: PMC7328585 DOI: 10.1016/j.neuron.2020.06.032] [Citation(s) in RCA: 223] [Impact Index Per Article: 55.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 06/24/2020] [Accepted: 06/25/2020] [Indexed: 12/11/2022]
Abstract
The main neurological manifestation of COVID-19 is loss of smell or taste. The high incidence of smell loss without significant rhinorrhea or nasal congestion suggests that SARS-CoV-2 targets the chemical senses through mechanisms distinct from those used by endemic coronaviruses or other common cold-causing agents. Here we review recently developed hypotheses about how SARS-CoV-2 might alter the cells and circuits involved in chemosensory processing and thereby change perception. Given our limited understanding of SARS-CoV-2 pathogenesis, we propose future experiments to elucidate disease mechanisms and highlight the relevance of this ongoing work to understanding how the virus might alter brain function more broadly.
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Affiliation(s)
- Keiland W Cooper
- Interdepartmental Neuroscience Program, University of California Irvine, Irvine, CA, USA
| | - David H Brann
- Harvard Medical School Department of Neurobiology, Boston, MA, USA
| | | | - Surabhi Bhutani
- School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA, USA
| | - Robert Pellegrino
- Department of Food Science, Institute of Agriculture, University of Tennessee, Knoxville, TN, USA; Smell & Taste Clinic, Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
| | | | - Caleb Weinreb
- Harvard Medical School Department of Neurobiology, Boston, MA, USA
| | - Paule V Joseph
- Division of Intramural Research, National Institute of Nursing Research (NINR) National Institutes of Health, Bethesda, MD, USA; National Institute on Alcohol Abuse and Alcoholism (NIAAA) National Institutes of Health, Bethesda, MD, USA
| | - Eric D Larson
- Department of Otolaryngology, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA and the Rocky Mountain Taste and Smell Center, Aurora, CO, USA
| | - Valentina Parma
- Department of Psychology, Temple University, Philadelphia, PA, USA
| | - Mark W Albers
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA
| | - Linda A Barlow
- Department of Cell and Developmental Biology, Graduate Program in Cell Biology, Stem Cells and Development and the Rocky Mountain Taste and Smell Center, University of Colorado, School Medicine, Anschutz Medical Campus, Aurora, CO, USA.
| | | | - Antonella Di Pizio
- Leibniz Institute for Food Systems Biology at the Technical University of Munich, Freising, Germany.
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19
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Increased Retinoic Acid Catabolism in Olfactory Sensory Neurons Activates Dormant Tissue-Specific Stem Cells and Accelerates Age-Related Metaplasia. J Neurosci 2020; 40:4116-4129. [PMID: 32385093 DOI: 10.1523/jneurosci.2468-19.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 04/03/2020] [Accepted: 04/25/2020] [Indexed: 12/28/2022] Open
Abstract
The cellular and molecular basis of metaplasia and declining neurogenesis in the aging olfactory epithelium (OE) remains unknown. The horizontal basal cell (HBC) is a dormant tissue-specific stem cell presumed to only be forced into self-renewal and differentiation by injury. Here we analyze male and female mice and show that HBCs also are activated with increasing age as well as non-cell-autonomously by increased expression of the retinoic acid-degrading enzyme CYP26B1. Activating stimuli induce HBCs throughout OE to acquire a rounded morphology and express IP3R3, which is an inositol-1,4,5-trisphosphate receptor constitutively expressed in stem cells of the adjacent respiratory epithelium. Odor/air stimulates CYP26B1 expression in olfactory sensory neurons mainly located in the dorsomedial OE, which is spatially inverse to ventrolateral constitutive expression of the retinoic acid-synthesizing enzyme (RALDH1) in supporting cells. In ventrolateral OE, HBCs express low p63 levels and preferentially differentiate instead of self-renewing when activated. When activated by chronic CYP26B1 expression, repeated injury, or old age, ventrolateral HBCs diminish in number and generate a novel type of metaplastic respiratory cell that is RALDH- and secretes a mucin-like mucus barrier protein (FcγBP). Conversely, in the dorsomedial OE, CYP26B1 inhibits injury-induced and age-related replacement of RALDH- supporting cells with RALDH1+ ciliated respiratory cells. Collectively, these results support the concept that inositol-1,4,5-trisphosphate type 3 receptor signaling in HBCs, together with altered retinoic acid metabolism within the niche, promote HBC lineage commitment toward two types of respiratory cells that will maintain epithelial barrier function once the capacity to regenerate OE cells ceases.SIGNIFICANCE STATEMENT Little is known about signals that activate dormant stem cells to self-renew and regenerate odor-detecting neurons and other olfactory cell types after loss due to injury, infection, or toxin exposure in the nose. It is also unknown why the stem cells do not prevent age-dependent decline of odor-detecting neurons. We show that (1) stem cells are kept inactive by the vitamin A derivative retinoic acid, which is synthesized and degraded locally by olfactory cells; (2) old age as well as repeated injuries activate the stem cells and exhaust their potential to produce olfactory cells; and (3) exhausted stem cells alter the local retinoic acid metabolism and maintain the epithelial tissue barrier by generating airway cells instead of olfactory cells.
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20
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Lemons K, Fu Z, Ogura T, Lin W. TRPM5-expressing Microvillous Cells Regulate Region-specific Cell Proliferation and Apoptosis During Chemical Exposure. Neuroscience 2020; 434:171-190. [PMID: 32224228 DOI: 10.1016/j.neuroscience.2020.03.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 03/19/2020] [Accepted: 03/20/2020] [Indexed: 12/23/2022]
Abstract
The mammalian main olfactory epithelium (MOE) is exposed to a wide spectrum of external chemicals during respiration and relies on adaptive plasticity to maintain its structural and functional integrity. We previously reported that the chemo-responsive and cholinergic transient receptor potential channel M5 (TRPM5)-expressing-microvillous cells (MCs) in the MOE are required for maintaining odor-evoked electrophysiological responses and olfactory-guided behavior during two-week exposure to an inhaled chemical mixture. Here, we investigated the underlying factors by assessing the potential modulatory effects of TRPM5-MCs on MOE morphology and cell proliferation and apoptosis, which are important for MOE maintenance. In the posterior MOE of TRPM5-GFP mice, we found that two-week chemical exposure induced a significant increase in Ki67-expressing proliferating basal stem cells without a significant reduction in the thickness of the whole epithelium or mature olfactory sensory neuron (OSN) layer. This adaptive increase in stem cell proliferation was missing in chemical-exposed transcription factor Skn-1a knockout (Skn-1a-/-) mice lacking TRPM5-MCs. In addition, a greater number of isolated OSNs from chemical-exposed Skn-1a-/- mice displayed unhealthily high levels of resting intracellular Ca2+. Intriguingly, in the anterior MOE where we found a higher density of TRPM5-MCs, chemical-exposed TRPM5-GFP mice exhibited a time-dependent increase in apoptosis and a loss of mature OSNs without a significant increase in proliferation or neurogenesis to compensate for OSN loss. Together, our data suggest that TRPM5-MC-dependent region-specific upregulation of cell proliferation in the majority of the MOE during chemical exposure contributes to the adaptive maintenance of OSNs and olfactory function.
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Affiliation(s)
- Kayla Lemons
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA
| | - Ziying Fu
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA
| | - Tatsuya Ogura
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA
| | - Weihong Lin
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA.
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21
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Awadallah N, Proctor K, Joseph KB, Delay ER, Delay RJ. Cyclophosphamide has Long-Term Effects on Proliferation in Olfactory Epithelia. Chem Senses 2020; 45:97-109. [PMID: 31844905 PMCID: PMC7446702 DOI: 10.1093/chemse/bjz075] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Chemotherapy patients often experience chemosensory changes during and after drug therapy. The chemotherapy drug, cyclophosphamide (CYP), has known cytotoxic effects on sensory and proliferating cells of the taste system. Like the taste system, cells in the olfactory epithelia undergo continuous renewal. Therefore, we asked if a single injection of 75 mg/kg CYP would affect cell proliferation in the anterior dorsomedial region of the main olfactory epithelium (MOE) and the vomeronasal organ (VNO) from 0 to 125 days after injection. Both epithelia showed a decrease in Ki67-labeled cells compared to controls at day 1 and no Ki67+ cells at day 2 postinjection. In the sensory layer of the MOE, cell proliferation began to recover 4 days after CYP injection and by 6 days, the rate of proliferation was significantly greater than controls. Ki67+ cells peaked 30 days postinjection, then declined to control levels at day 45. Similar temporal sequences of initial CYP-induced suppression of cell proliferation followed by elevated rates peaking 30-45 days postinjection were seen in the sustentacular layer of the MOE and all 3 areas (sensory, sustentacular, marginal) of the VNO. CYP affected proliferation in the sensory layer of the MOE more than the sustentacular layer and all 3 areas of the VNO. These findings suggest that chemotherapy involving CYP is capable of affecting cell renewal of the olfactory system and likely contributes to clinical loss of function during and after chemotherapy.
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Affiliation(s)
- Nora Awadallah
- Neuroscience Program, Marsh Life Science, University of Vermont, Burlington, USA
| | - Kara Proctor
- Department of Biomedical and Health Sciences, University of Vermont, Burlington, USA
| | - Kyle B Joseph
- Department of Biology, Marsh Life Science, University of Vermont, Burlington, USA
| | - Eugene R Delay
- Neuroscience Program, Marsh Life Science, University of Vermont, Burlington, USA
- Department of Biology, Marsh Life Science, University of Vermont, Burlington, USA
| | - Rona J Delay
- Neuroscience Program, Marsh Life Science, University of Vermont, Burlington, USA
- Department of Biology, Marsh Life Science, University of Vermont, Burlington, USA
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Coppola DM, Fitzwater E, Rygg AD, Craven BA. Tests of the chromatographic theory of olfaction with highly soluble odors: a combined electro-olfactogram and computational fluid dynamics study in the mouse. Biol Open 2019; 8:bio.047217. [PMID: 31649069 PMCID: PMC6826284 DOI: 10.1242/bio.047217] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The idea that the vertebrate nasal cavity operates like a gas chromatograph to separate and discriminate odors, referred to herein as the ‘chromatographic theory’ (CT), has a long and interesting history. Though the last decade has seen renewed interest in the notion, its validity remains in question. Here we examine a necessary condition of the theory: a correlation between nasal odor deposition patterns based on mucus solubility and the distribution of olfactory sensory neuron odotypes. Our recent work in the mouse failed to find such a relationship even across large sorption gradients within the olfactory epithelium (OE). However, these studies did not test extremely soluble odorants or low odor concentrations, factors that could explain our inability to find supporting evidence for the CT. The current study combined computational fluid dynamics (CFD) simulations of odor sorption patterns and electro-olfactogram (EOG) measurements of olfactory sensory neuron responses. The odorants tested were at the extremes of mucus solubility and at a range of concentrations. Results showed no relationship between local odor sorption patterns and EOG response maps. Together, results again failed to support a necessary condition of the CT casting further doubt on the viability of this classical odor coding mechanism. Summary: This paper casts doubt on the classical chromatographic theory of olfaction, showing there is no correlation between olfactory receptor spatial layout and odor solubility patterns, a necessary condition of the theory.
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Affiliation(s)
- David M Coppola
- Department of Biology, Randolph-Macon College, Ashland, VA 23005, USA
| | - Emily Fitzwater
- Department of Biology, Randolph-Macon College, Ashland, VA 23005, USA
| | - Alex D Rygg
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA 90095, USA
| | - Brent A Craven
- Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802, USA
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Sánchez-Guardado L, Lois C. Lineage does not regulate the sensory synaptic input of projection neurons in the mouse olfactory bulb. eLife 2019; 8:46675. [PMID: 31453803 PMCID: PMC6744224 DOI: 10.7554/elife.46675] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 08/26/2019] [Indexed: 12/14/2022] Open
Abstract
Lineage regulates the synaptic connections between neurons in some regions of the invertebrate nervous system. In mammals, recent experiments suggest that cell lineage determines the connectivity of pyramidal neurons in the neocortex, but the functional relevance of this phenomenon and whether it occurs in other neuronal types remains controversial. We investigated whether lineage plays a role in the connectivity of mitral and tufted cells, the projection neurons in the mouse olfactory bulb. We used transgenic mice to sparsely label neuronal progenitors and observed that clonally related neurons receive synaptic input from olfactory sensory neurons expressing different olfactory receptors. These results indicate that lineage does not determine the connectivity between olfactory sensory neurons and olfactory bulb projection neurons.
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Affiliation(s)
- Luis Sánchez-Guardado
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
| | - Carlos Lois
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States
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24
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Nguyen UP, Imamura F. Regional differences in mitral cell development in mouse olfactory bulb. J Comp Neurol 2019; 527:2233-2244. [PMID: 30864157 DOI: 10.1002/cne.24683] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 03/11/2019] [Accepted: 03/12/2019] [Indexed: 11/09/2022]
Abstract
Olfactory sensory neurons (OSNs) located in the dorsomedial and ventromedial regions of the olfactory epithelium (OE) are distinguished from one another based on their molecular expression patterns. This difference is reflected in the separation of the glomerular layer of the olfactory bulb (OB) into dorsomedial and ventrolateral regions. However, it is unclear whether a complementary separation is also evident in the projection neurons that innervate the OB glomeruli. In this study, we compared the development of the OB between different regions by focusing on the transcription factor, Tbx21, which is expressed by mitral and tufted cells in the mature OB. Examining the OB at different developmental ages, we found that Tbx21 expression commenced in the anteromedial region called the tongue-shaped area, followed by the dorsomedial and then ventrolateral areas. We also showed that the tongue-shaped area was innervated by the OSNs located in the most dorsomedial part of the ventrolateral OE, the V-zone:DM. Interestingly, the generation of OSNs occurred first in the dorsomedial zone including the V-zone:DM, suggesting a correlation between the time course of OSN generation in the OE and Tbx21 expression in their target region of the OB. In contrast, expression of vGluT1, which is also found in all mitral cells in the mature OB, was first detected in the ventrolateral region during development. Our findings demonstrate that the development of projection neurons occurs in a compartmentalized manner in the OB; tongue-shaped, dorsomedial, and ventrolateral areas, and that not all projection neurons follow the same developmental pathway.
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Affiliation(s)
- Uyen P Nguyen
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania
| | - Fumiaki Imamura
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pennsylvania
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25
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Spatial Determination of Neuronal Diversification in the Olfactory Epithelium. J Neurosci 2018; 39:814-832. [PMID: 30530861 DOI: 10.1523/jneurosci.3594-17.2018] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 11/21/2018] [Accepted: 11/23/2018] [Indexed: 01/31/2023] Open
Abstract
Neurons in the murine olfactory epithelium (OE) differ by the olfactory receptor they express as well as other molecular phenotypes that are regionally restricted. These patterns can be precisely regenerated following epithelial injury, suggesting that spatial cues within the tissue can direct neuronal diversification. Nonetheless, the permanency and mechanism of this spatial patterning remain subject to debate. Via transplantation of stem and progenitor cells from dorsal OE into ventral OE, we demonstrate that, in mice of both sexes, nonautonomous spatial cues can direct the spatially circumscribed differentiation of olfactory sensory neurons. The vast majority of dorsal transplant-derived neurons express the ventral marker OCAM (NCAM2) and lose expression of NQO1 to match their new location. Single-cell analysis also demonstrates that OSNs adopt a fate defined by their new position following progenitor cell transplant, such that a ventral olfactory receptor is expressed after stem and progenitor cell engraftment. Thus, spatially constrained differentiation of olfactory sensory neurons is plastic, and any bias toward an epigenetic memory of place can be overcome.SIGNIFICANCE STATEMENT Spatially restricted differentiation of olfactory sensory neurons is both key to normal olfactory function and a challenging example of biological specificity. That the stem cells of the olfactory epithelium reproduce the organization of the olfactory periphery to a very close approximation during lesion-induced regeneration begs the question of whether stem cell-autonomous genomic architecture or environmental cues are responsible. The plasticity demonstrated after transfer to a novel location suggests that cues external to the transplanted stem and progenitor cells confer neuronal identity. Thus, a necessary prerequisite is satisfied for using engraftment of olfactory stem and progenitor cells as a cellular therapeutic intervention to reinvigorate neurogenesis whose exhaustion contributes to the waning of olfaction with age.
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26
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Dorsal-zone-specific reduction of sensory neuron density in the olfactory epithelium following long-term exercise or caloric restriction. Sci Rep 2018; 8:17300. [PMID: 30470811 PMCID: PMC6251928 DOI: 10.1038/s41598-018-35607-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 11/08/2018] [Indexed: 01/09/2023] Open
Abstract
Exercise (Ex) and caloric restriction (CR) reduce oxidative stress and improve organ function. For instance, voluntary Ex or CR is known to reduce age-related cochlear damage in male C57BL/6J mice. However, the effect of Ex and CR on the olfactory system is unknown. In this study, we confirmed the positive effect of Ex and CR on age-related cochlear damage, but found that Ex and CR affected negatively cell dynamics in the olfactory epithelium (OE) by reducing the number of mature olfactory sensory neurons (OSNs) and increasing the number of proliferative basal cells and apoptotic OSNs in the dorsal zone of the olfactory epithelium (OE), which contains neurons expressing NADPH quinone oxido-reductase 1 (NQO1). In addition, these interventions resulted in lower odor-induced c-fos expression in areas of the olfactory bulb receiving projections from dorsal-zone OSNs than in areas receiving ventral-zone projections. Further, we observed substantial oxidative stress in NQO1-positive cells and apoptotic OSNs in the dorsal zone in Ex and CR animals. These results suggest that, in contrast to their positive effects in other organs, Ex and CR facilitate oxidative stress and negatively impact structure and function in dorsal-zone OSNs, probably in association with NQO1 bioactivation.
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27
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Hasegawa-Ishii S, Shimada A, Imamura F. Neuroplastic changes in the olfactory bulb associated with nasal inflammation in mice. J Allergy Clin Immunol 2018; 143:978-989.e3. [PMID: 30315829 DOI: 10.1016/j.jaci.2018.09.028] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 08/24/2018] [Accepted: 09/03/2018] [Indexed: 12/31/2022]
Abstract
BACKGROUND Rhinitis and rhinosinusitis are olfactory disorders caused by inflammation of the nasal passage and paranasal sinuses. Although patients with chronic rhinosinusitis have smaller olfactory bulbs (OBs), there is limited knowledge regarding the influence of chronic nasal inflammation on OB neurons. OBJECTIVE Repeated intranasal administration of LPS that induced persistent nasal inflammation in mice caused a loss of olfactory sensory neurons (OSNs) and gliosis and synaptic loss in the OBs within 3 weeks. The present study aimed to clarify the effects of long-term LPS treatment on the OB neurocircuit. METHODS LPS was repeatedly administered into a mouse nostril for up to 24 weeks. For the recovery analyses, the mice received LPS for 10 weeks and were subsequently maintained without additional treatment for another 10 weeks. The effects of these treatments on the OBs were examined histologically. Three or more mice were analyzed per group. RESULTS Long-term repeated LPS administration caused OB atrophy, particularly in the layers along which OSN axons travel and in the superficial external plexiform layer, in which tufted cells form synapses with interneurons. Interestingly, the OBs recovered from atrophy after cessation of LPS administration: OB volume and superficial external plexiform layer thickness returned to pretreatment levels after the nontreatment period. In contrast, OSN regeneration was incomplete. CONCLUSION These results suggest that chronic nasal inflammation induces structural changes in a specific OB circuit related to tufted cells, whereas tufted cells retain a high degree of plasticity that enables recovery from structural damages after inflammation subsides.
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Affiliation(s)
- Sanae Hasegawa-Ishii
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pa; Faculty of Health Sciences, Kyorin University, Tokyo, Japan
| | | | - Fumiaki Imamura
- Department of Pharmacology, Penn State College of Medicine, Hershey, Pa.
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28
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Tan L, Xie XS. A Near-Complete Spatial Map of Olfactory Receptors in the Mouse Main Olfactory Epithelium. Chem Senses 2018; 43:427-432. [PMID: 29796642 PMCID: PMC6454507 DOI: 10.1093/chemse/bjy030] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Different regions of the mammalian nose smell different odors. In the mouse olfactory system, spatially regulated expression of >1000 olfactory receptors (ORs) along the dorsomedial-ventrolateral (DV) axis forms a topological map in the main olfactory epithelium (MOE). However, the locations of most ORs along the DV axis are currently unknown. By sequencing mRNA of 12 isolated MOE pieces, we mapped out the DV locations-as quantified by "zone indices" on a scale of 1-5-of 1033 OR genes with an estimated error of 0.3 zone indices. Our map covered 81% of all intact OR genes and 99.4% of the total OR mRNA abundance. Spatial regulation tended to vary gradually along chromosomes. We further identified putative non-OR genes that may exhibit spatial expression along the DV axis.
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Affiliation(s)
- Longzhi Tan
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Systems Biology PhD Program, Harvard Medical School, Boston, MA, USA
| | - Xiaoliang Sunney Xie
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
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29
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Octura JER, Maeda KI, Wakabayashi Y. Structure and zonal expression of olfactory receptors in the olfactory epithelium of the goat, Capra hircus. J Vet Med Sci 2018; 80:913-920. [PMID: 29681556 PMCID: PMC6021871 DOI: 10.1292/jvms.17-0692] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mammalian olfactory system employs sophisticated mechanisms to detect and recognize an extensive range of smells. In rodents, the olfactory epithelium (OE), situated within the nasal cavity, mainly comprises four defined endoturbinates and several ectoturbinates. Olfactory receptors (ORs) belong to a large family, comprising over 1,000 genes in rodents, which are expressed in olfactory sensory neurons in the OE that detect odor molecules. The rodent OE is divided into four topographically distinct zones, defined by individual OR distribution. However, although the structural complexity and the zonal organization of mammalian OE may contribute to successfully interpreting olfactory information, it remains poorly understood. In this study, we investigated the nasal cavity structure and zonal organization of the OE in goats. Morphological observations revealed that the goat nasal cavity possessed well-developed endoturbinates and ectoturbinates and had a structure similar to that of rodents and sheep, previously reported in other studies. In situ hybridization was used to analyze the expression pattern of ORs, NADPH:quinone oxidoreductase 1, and olfactory cell adhesion molecules as markers of zonal organization in the goat OE. Based on the expression patterns of these genes, we concluded that the goat OE was divided into four zones. The well-developed structure of the nasal cavity and distribution of each OR in the OE were similar to those found in rodents, suggesting that these features were highly conserved between mammals and may have fundamental roles in discriminating among numerous odor molecules in the environment.
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Affiliation(s)
- Josh Elisha R Octura
- Department of Veterinary Medical Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.,Institute of Livestock and Grassland Science, National Agriculture and Food Research Organization (NARO), 2 Ikenodai, Tsukuba, Ibaraki 305-0901, Japan
| | - Kei-Ichiro Maeda
- Department of Veterinary Medical Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yoshihiro Wakabayashi
- Institute of Livestock and Grassland Science, National Agriculture and Food Research Organization (NARO), 2 Ikenodai, Tsukuba, Ibaraki 305-0901, Japan
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30
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Imamura F, Cooper TK, Hasegawa-Ishii S, Sonobe T, Haouzi P. Hydrogen Sulfide Specifically Alters NAD(P)H Quinone Dehydrogenase 1 (NQO1) Olfactory Neurons in the Rat. Neuroscience 2017; 366:105-112. [PMID: 29054567 DOI: 10.1016/j.neuroscience.2017.10.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 10/10/2017] [Accepted: 10/12/2017] [Indexed: 11/19/2022]
Abstract
The regions of the olfactory epithelium affected by hydrogen sulfide (H2S) toxicity in the rat present a striking similarity with the developmental olfactory zone 1 described in the mouse. This zone which is the only region containing neurons expressing NAD(P)H quinone dehydrogenase 1 (NQO1) is involved in complex behavioral responses in rodents, and other mammals, triggered by specific olfactory stimuli. We therefore sought to determine whether (1) olfactory neurons expressing NQO1 are located in the same regions in the rats and in the mice and (2) there is an overlap between olfactory neurons expressing this protein and those affected by the toxicity of H2S. Rats were exposed to H2S - 200 ppm during 3 h, three consecutive days- and displayed symmetric acute segmental necrosis of the neurons and sustentacular cells of the olfactory epithelium in the dorsomedial nasal cavity. We found that expression of NQO1 in Sprague-Dawley rats spatially recapitulated that of the mouse. The degree of agreement or overlap between these two populations of neurons (necrosis vs. NQO1 expression) reached 80.2%. Although the underlying mechanisms accounted for the high sensitivity for NQO1 neurons -or the relative protection of non NQO1 neurons- to sulfide toxicity remain to be established, this observation is offering an intriguing approach that could be used to acutely suppress the pool of neural cells in olfactory zone I and to understand the mechanisms of toxicity and protection of other populations of neurons exposed to sulfide.
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Affiliation(s)
- Fumiaki Imamura
- Department of Pharmacology, Pennsylvania State University, College of Medicine, Hershey, PA, USA
| | - Timothy K Cooper
- Department of Pathology, Pennsylvania State University, College of Medicine, Hershey, PA, USA; Department of Comparative Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, USA
| | - Sanae Hasegawa-Ishii
- Department of Pharmacology, Pennsylvania State University, College of Medicine, Hershey, PA, USA
| | - Takashi Sonobe
- Division of Pulmonary and Critical Care Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, USA
| | - Philippe Haouzi
- Division of Pulmonary and Critical Care Medicine, Pennsylvania State University, College of Medicine, Hershey, PA, USA.
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31
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Hasegawa-Ishii S, Shimada A, Imamura F. Lipopolysaccharide-initiated persistent rhinitis causes gliosis and synaptic loss in the olfactory bulb. Sci Rep 2017; 7:11605. [PMID: 28912588 PMCID: PMC5599676 DOI: 10.1038/s41598-017-10229-w] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 08/07/2017] [Indexed: 12/12/2022] Open
Abstract
The olfactory mucosa (OM) is exposed to environmental agents and therefore vulnerable to inflammation. To examine the effects of environmental toxin-initiated OM inflammation on the olfactory bulb (OB), we induced persistent rhinitis in mice and analyzed the spatial and temporal patterns of histopathological changes in the OM and OB. Mice received unilateral intranasal administration of lipopolysaccharide (LPS) or saline three times per week, and were immunohistologically analyzed at 1, 3, 7, 14 and 21 days after the first administration. LPS administration induced an inflammatory response in the OM, including the infiltration of Ly-6G-, CD11b-, Iba-1- and CD3-positive cells, the production of interleukin-1β by CD11b- and Iba-1-positive cells, and loss of olfactory sensory neurons (OSNs). In the OB, we observed activation of microglia and astrocytes and decreased expression of tyrosine hydroxylase in periglomerular cells, vesicular glutamate transporter 1, a presynaptic protein, in mitral and tufted projection neurons, and 5T4 in granule cells. Thus, the OM inflammation exerted a detrimental effect, not only on OSNs, but also on OB neurons, which might lead to neurodegeneration.
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Affiliation(s)
- Sanae Hasegawa-Ishii
- Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, 17033, USA
| | - Atsuyoshi Shimada
- Faculty of Health Sciences, Kyorin University, 5-4-1 Shimorenjaku, Mitaka, Tokyo, 181-8612, Japan
| | - Fumiaki Imamura
- Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA, 17033, USA.
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32
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Ravi N, Sanchez-Guardado L, Lois C, Kelsch W. Determination of the connectivity of newborn neurons in mammalian olfactory circuits. Cell Mol Life Sci 2017; 74:849-867. [PMID: 27695873 PMCID: PMC11107630 DOI: 10.1007/s00018-016-2367-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Revised: 08/24/2016] [Accepted: 09/13/2016] [Indexed: 12/24/2022]
Abstract
The mammalian olfactory bulb is a forebrain structure just one synapse downstream from the olfactory sensory neurons and performs the complex computations of sensory inputs. The formation of this sensory circuit is shaped through activity-dependent and cell-intrinsic mechanisms. Recent studies have revealed that cell-type specific connectivity and the organization of synapses in dendritic compartments are determined through cell-intrinsic programs already preset in progenitor cells. These progenitor programs give rise to subpopulations within a neuron type that have distinct synaptic organizations. The intrinsically determined formation of distinct synaptic organizations requires factors from contacting cells that match the cell-intrinsic programs. While certain genes control wiring within the newly generated neurons, other regulatory genes provide intercellular signals and are only expressed in neurons that will form contacts with the newly generated cells. Here, the olfactory system has provided a useful model circuit to reveal the factors regulating assembly of the highly structured connectivity in mammals.
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Affiliation(s)
- Namasivayam Ravi
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159, Mannheim, Germany
| | - Luis Sanchez-Guardado
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA, 91125, USA
| | - Carlos Lois
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA, 91125, USA.
| | - Wolfgang Kelsch
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159, Mannheim, Germany.
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33
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Eerdunfu, Ihara N, Ligao B, Ikegaya Y, Takeuchi H. Differential timing of neurogenesis underlies dorsal-ventral topographic projection of olfactory sensory neurons. Neural Dev 2017; 12:2. [PMID: 28193234 PMCID: PMC5307877 DOI: 10.1186/s13064-017-0079-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 02/06/2017] [Indexed: 11/25/2022] Open
Abstract
Background The mammalian primary olfactory system has a spatially-ordered projection in which olfactory sensory neurons (OSNs) located in the dorsomedial (DM) and ventrolateral (VL) region of the olfactory epithelium (OE) send their axons to the dorsal and ventral region of the olfactory bulb (OB), respectively. We previously found that OSN axonal projections occur sequentially, from the DM to the VL region of the OE. The differential timing of axonal projections is important for olfactory map formation because early-arriving OSN axons secrete guidance cues at the OB to help navigate late-arriving OSN axons. We hypothesized that the differential timing of axonal projections is regulated by the timing of OSN neurogenesis. To test this idea, we investigated spatiotemporal patterns of OSN neurogenesis during olfactory development. Methods and results To determine the time of OSN origin, we used two thymidine analogs, BrdU and EdU, which can be incorporated into cells in the S-phase of the cell-cycle. We injected these two analogs at different developmental time points and analyzed distribution patterns of labeled OSNs. We found that OSNs with different dates of origin were differentially distributed in the OE. The majority of OSNs generated at the early stage of development were located in the DM region of the OE, whereas OSNs generated at the later stage of development were preferentially located in the VL region of the OE. Conclusions These results indicate that the number of OSNs is sequentially increased from the DM to the VL axis of the OE. Moreover, the temporal sequence of OSN proliferation correlates with that of axonal extension and emergence of glomerular structures in the OB. Thus, we propose that the timing of OSN neurogenesis regulates that of OSN axonal projection and thereby helps preserve the topographic order of the olfactory glomerular map along the dorsal–ventral axis of the OB. Electronic supplementary material The online version of this article (doi:10.1186/s13064-017-0079-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Eerdunfu
- Division of Innate Immunity, Department of Microbiology and Immunology, the Institute of Medical Science, the University of Tokyo, Tokyo, 108-8639, Japan
| | - Naoki Ihara
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, the University of Tokyo, Tokyo, 113-0033, Japan
| | - Bao Ligao
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, the University of Tokyo, Tokyo, 113-0033, Japan
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, the University of Tokyo, Tokyo, 113-0033, Japan.,Center for Information and Neural Networks, National Institute of Information and Communications Technology, Suita City, Osaka, 565-0871, Japan
| | - Haruki Takeuchi
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, the University of Tokyo, Tokyo, 113-0033, Japan. .,Japan Science and Technology Agency (JST), PRESTO, 4-1-8 Honcho Kawaguchi, Saitama, 332-0012, Japan.
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34
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Imamura F, Hasegawa-Ishii S. Environmental Toxicants-Induced Immune Responses in the Olfactory Mucosa. Front Immunol 2016; 7:475. [PMID: 27867383 PMCID: PMC5095454 DOI: 10.3389/fimmu.2016.00475] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/19/2016] [Indexed: 01/02/2023] Open
Abstract
Olfactory sensory neurons (OSNs) are the receptor cells for the sense of smell. Although cell bodies are located in the olfactory mucosa (OM) of the nasal cavity, OSN axons directly project to the olfactory bulb (OB) that is a component of the central nervous system (CNS). Because of this direct and short connection from this peripheral tissue to the CNS, the olfactory system has attracted attention as a port-of-entry for environmental toxicants that may cause neurological dysfunction. Selected viruses can enter the OB via the OM and directly affect the CNS. On the other hand, environmental toxicants may induce inflammatory responses in the OM, including infiltration of immune cells and production of inflammatory cytokines. In addition, these inflammatory responses cause the loss of OSNs that are then replaced with newly generated OSNs that re-connect to the OB after inflammation has subsided. It is now known that immune cells and cytokines in the OM play important roles in both degeneration and regeneration of OSNs. Thus, the olfactory system is a unique neuroimmune interface where interaction between nervous and immune systems in the periphery significantly affects the structure, neuronal circuitry, and immunological status of the CNS. The mechanisms by which immune cells regulate OSN loss and the generation of new OSNs are, however, largely unknown. To help develop a better understanding of the mechanisms involved, we have provided a review of key research that has investigated how the immune response in the OM affects the pathophysiology of OSNs.
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Affiliation(s)
- Fumiaki Imamura
- Department of Pharmacology, Penn State College of Medicine , Hershey, PA , USA
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35
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Parrilla M, Chang I, Degl'Innocenti A, Omura M. Expression of homeobox genes in the mouse olfactory epithelium. J Comp Neurol 2016; 524:2713-39. [PMID: 27243442 DOI: 10.1002/cne.24051] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 12/16/2015] [Accepted: 05/25/2016] [Indexed: 01/22/2023]
Abstract
Homeobox genes constitute a large family of genes widely studied because of their role in the establishment of the body pattern. However, they are also involved in many other events during development and adulthood. The main olfactory epithelium (MOE) is an excellent model to study neurogenesis in the adult nervous system. Analyses of homeobox genes during development show that some of these genes are involved in the formation and establishment of cell diversity in the MOE. Moreover, the mechanisms of expression of odorant receptors (ORs) constitute one of the biggest enigmas in the field. Analyses of OR promoters revealed the presence of homeodomain binding sites in their sequences. Here we characterize the expression patterns of a set of 49 homeobox genes in the MOE with in situ hybridization. We found that seven of them (Dlx3, Dlx5, Dlx6, Msx1, Meis1, Isl1, and Pitx1) are zonally expressed. The homeobox gene Emx1 is expressed in three guanylate cyclase(+) populations, two located in the MOE and the third one in an olfactory subsystem known as Grüneberg ganglion located at the entrance of the nasal cavity. The homeobox gene Tshz1 is expressed in a unique patchy pattern across the MOE. Our findings provide new insights to guide functional studies that aim to understand the complexity of transcription factor expression and gene regulation in the MOE. J. Comp. Neurol. 524:2713-2739, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Marta Parrilla
- Max Planck Institut für Biophysik, Frankfurt am Main, Germany
| | - Isabelle Chang
- Max Planck Institut für Biophysik, Frankfurt am Main, Germany
| | - Andrea Degl'Innocenti
- Max Planck Institut für Biophysik, Frankfurt am Main, Germany.,Unità di Biologia Cellulare e dello Sviluppo, Dipartimento di Biologia, Università di Pisa, Pisa, Italy
| | - Masayo Omura
- Max Planck Institut für Biophysik, Frankfurt am Main, Germany
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The Stimulus-Dependent Gradient of Cyp26B1+ Olfactory Sensory Neurons Is Necessary for the Functional Integrity of the Olfactory Sensory Map. J Neurosci 2016; 35:13807-18. [PMID: 26446231 DOI: 10.1523/jneurosci.2247-15.2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Stimulus-dependent expression of the retinoic acid-inactivating enzyme Cyp26B1 in olfactory sensory neurons (OSNs) forms a dorsomedial (DM)-ventrolateral (VL) gradient in the mouse olfactory epithelium. The gradient correlates spatially with different rates of OSN turnover, as well as the functional organization of the olfactory sensory map, into overlapping zones of OSNs that express different odorant receptors (ORs). Here, we analyze transgenic mice that, instead of a stimulus-dependent Cyp26B1 gradient, have constitutive Cyp26B1 levels in all OSNs. Starting postnatally, OSN differentiation is decreased and progenitor proliferation is increased. Initially, these effects are selective to the VL-most zone and correlate with reduced ATF5 expression and accumulation of OSNs that do not express ORs. Transcription factor ATF5 is known to stabilize OR gene choice via onset of the stimulus-transducing enzyme adenylyl cyclase type 3. During further postnatal development of Cyp26B1 mice, an anomalous DM(high)-VL(low) expression gradient of adenylyl cyclase type 3 appears, which coincides with altered OR frequencies and OR zones. All OR zones expand ventrolaterally except for the VL-most zone, which contracts. The expansion results in an increased zonal overlap that is also evident in the innervation pattern of OSN axon terminals in olfactory bulbs. These findings together identify a mechanism by which postnatal sensory-stimulated vitamin A metabolism modifies the generation of spatially specified neurons and their precise topographic connectivity. The distributed patterns of vitamin A-metabolizing enzymes in the nervous system suggest the possibility that the mechanism may also regulate neuroplasticity in circuits other than the olfactory sensory map. SIGNIFICANCE STATEMENT The mouse olfactory sensory map is functionally wired according to precise axonal projections of spatially organized classes of olfactory sensory neurons in the nose. The genetically controlled mechanisms that regulate the development of the olfactory sensory map are beginning to be elucidated. Little is known about mechanisms by which sensory stimuli shape the organization of the map after birth. We show that a stimulus-dependent gradient of a retinoic acid-inactivating enzyme Cyp26B1 modifies the composition, localization, and axonal projections of olfactory sensory neuron classes. The mechanism is novel and suggests the interesting possibility that local vitamin A metabolism could also be a mediator of stimulus-dependent modifications of precise spatial connectivity in other parts of the nervous system.
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Kim JM, Ren D, Reverter A, Roura E. A regulatory gene network related to the porcine umami taste receptor (TAS1R1/TAS1R3). Anim Genet 2015; 47:114-9. [PMID: 26554867 DOI: 10.1111/age.12374] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2015] [Indexed: 11/28/2022]
Abstract
Taste perception plays an important role in the mediation of food choices in mammals. The first porcine taste receptor genes identified, sequenced and characterized, TAS1R1 and TAS1R3, were related to the dimeric receptor for umami taste. However, little is known about their regulatory network. The objective of this study was to unfold the genetic network involved in porcine umami taste perception. We performed a meta-analysis of 20 gene expression studies spanning 480 porcine microarray chips and screened 328 taste-related genes by selective mining steps among the available 12,320 genes. A porcine umami taste-specific regulatory network was constructed based on the normalized coexpression data of the 328 genes across 27 tissues. From the network, we revealed the 'taste module' and identified a coexpression cluster for the umami taste according to the first connector with the TAS1R1/TAS1R3 genes. Our findings identify several taste-related regulatory genes and extend previous genetic background of porcine umami taste.
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Affiliation(s)
- J M Kim
- Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation Hartley Teakle 83, The University of Queensland, St Lucia, Queensland, 4072, Australia
| | - D Ren
- Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation Hartley Teakle 83, The University of Queensland, St Lucia, Queensland, 4072, Australia
| | - A Reverter
- CSIRO Agriculture Flagship, Queensland Bioscience Precinct, 306 Carmody Road, St Lucia, Queensland, 4067, Australia
| | - E Roura
- Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation Hartley Teakle 83, The University of Queensland, St Lucia, Queensland, 4072, Australia
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Suzuki J, Sakurai K, Yamazaki M, Abe M, Inada H, Sakimura K, Katori Y, Osumi N. Horizontal Basal Cell-Specific Deletion of Pax6 Impedes Recovery of the Olfactory Neuroepithelium Following Severe Injury. Stem Cells Dev 2015; 24:1923-33. [PMID: 25808240 DOI: 10.1089/scd.2015.0011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
In the mammalian olfactory epithelium (OE), olfactory receptor neurons (ORNs) are continuously regenerated throughout the animal's lifetime. Horizontal basal cells (HBCs) in the OE express the epithelial marker keratin 5 (K5) and the stem cell marker Pax6 and are considered relatively quiescent tissue stem cells in the OE. Pax6 is a key regulator of several developmental processes in the central nervous system and in sensory organs. Although Pax6 is expressed in the OE, its precise role remains unknown, particularly with respect to stem cell-like HBCs. To investigate the function of Pax6 in the developmental and regenerative processes in the OE, we generated conditional Pax6-knockout mice carrying a loxP-floxed Pax6 gene. Homozygous Pax6-floxed mice were crossed with K5-Cre transgenic mice to generate HBC-specific Pax6-knockout (Pax6-cKO) mice. We confirmed that the deletion of Pax6 expression in HBCs was sufficiently achieved in zone 1 of the OE in Pax6-cKO mice 3 days after methimazole-induced severe damage. In this condition, regeneration of the OE was dramatically impaired; both OE thickness and the number of ORNs were significantly decreased in the regenerated OE of Pax6-cKO mice. These results suggest that Pax6 expression is essential for HBCs to differentiate into neuronal cells during the regeneration process following severe injury.
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Affiliation(s)
- Jun Suzuki
- 1 Department of Developmental Neuroscience, Centers for Neuroscience, Tohoku University Graduate School of Medicine , Sendai, Miyagi, Japan .,2 Department of Otorhinolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine , Sendai, Miyagi, Japan
| | - Katsuyasu Sakurai
- 3 Department of Neurobiology, Duke University Medical Center , Durham, North Carolina
| | - Maya Yamazaki
- 4 Department of Cellular Neurobiology, Brain Research Institute, Niigata University , Niigata, Japan
| | - Manabu Abe
- 4 Department of Cellular Neurobiology, Brain Research Institute, Niigata University , Niigata, Japan
| | - Hitoshi Inada
- 1 Department of Developmental Neuroscience, Centers for Neuroscience, Tohoku University Graduate School of Medicine , Sendai, Miyagi, Japan
| | - Kenji Sakimura
- 4 Department of Cellular Neurobiology, Brain Research Institute, Niigata University , Niigata, Japan
| | - Yukio Katori
- 2 Department of Otorhinolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine , Sendai, Miyagi, Japan
| | - Noriko Osumi
- 1 Department of Developmental Neuroscience, Centers for Neuroscience, Tohoku University Graduate School of Medicine , Sendai, Miyagi, Japan
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Olfactory receptor genes expressed in distinct lineages are sequestered in different nuclear compartments. Proc Natl Acad Sci U S A 2015; 112:E2403-9. [PMID: 25897022 DOI: 10.1073/pnas.1506058112] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The olfactory system translates a vast array of volatile chemicals into diverse odor perceptions and innate behaviors. Odor detection in the mouse nose is mediated by 1,000 different odorant receptors (ORs) and 14 trace amine-associated receptors (TAARs). ORs are used in a combinatorial manner to encode the unique identities of myriad odorants. However, some TAARs appear to be linked to innate responses, raising questions about regulatory mechanisms that might segregate OR and TAAR expression in appropriate subsets of olfactory sensory neurons (OSNs). Here, we report that OSNs that express TAARs comprise at least two subsets that are biased to express TAARs rather than ORs. The two subsets are further biased in Taar gene choice and their distribution within the sensory epithelium, with each subset preferentially expressing a subgroup of Taar genes within a particular spatial domain in the epithelium. Our studies reveal one mechanism that may regulate the segregation of Olfr (OR) and Taar expression in different OSNs: the sequestration of Olfr and Taar genes in different nuclear compartments. Although most Olfr genes colocalize near large central heterochromatin aggregates in the OSN nucleus, Taar genes are located primarily at the nuclear periphery, coincident with a thin rim of heterochromatin. Taar-expressing OSNs show a shift of one Taar allele away from the nuclear periphery. Furthermore, examination of hemizygous mice with a single Taar allele suggests that the activation of a Taar gene is accompanied by an escape from the peripheral repressive heterochromatin environment to a more permissive interior chromatin environment.
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Kishida T, Thewissen JGM, Hayakawa T, Imai H, Agata K. Aquatic adaptation and the evolution of smell and taste in whales. ZOOLOGICAL LETTERS 2015; 1:9. [PMID: 26605054 PMCID: PMC4604112 DOI: 10.1186/s40851-014-0002-z] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 10/23/2014] [Indexed: 06/05/2023]
Abstract
INTRODUCTION While olfaction is one of the most important senses in most terrestrial mammals, it is absent in modern toothed whales (Odontoceti, Cetacea). Furthermore, behavioral evidence suggests that gustation is very limited. In contrast, their aquatic sistergroup, baleen whales (Mysticeti) retain small but functional olfactory organs, and nothing is known about their gustation. It is difficult to investigate mysticete chemosensory abilities because experiments in a controlled setting are impossible. RESULTS Here, we use the functional regionalization of the olfactory bulb (OB) to identify the loss of specific olfactory functions in mysticetes. We provide the whole-genome sequence of a mysticete and show that mysticetes lack the dorsal domain of the OB, an area known to induce innate avoidance behavior against odors of predators and spoiled foods. Genomic and fossil data suggest that mysticetes lost the dorsal domain of the OB before the Odontoceti-Mysticeti split. Furthermore, we found that all modern cetaceans are revealed to have lost the functional taste receptors. CONCLUSION These results strongly indicate that profound changes in the chemosensory capabilities had occurred in the cetacean lineage during the period when ancestral whales migrated from land to water.
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Affiliation(s)
- Takushi Kishida
- />Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo, Kyoto 606-8502 Japan
- />Present affiliation: Wildlife Research Center, Kyoto University, 2-24 Tanaka Sekiden-cho, Sakyo, Kyoto 606-8203 Japan
| | - JGM Thewissen
- />Department of Anatomy and Neurobiology, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH 44272 USA
| | - Takashi Hayakawa
- />Primate Research Institute, Kyoto University, Kanrin, Inuyama, Aichi 484-8506 Japan
- />Japan Society for the Promotion of Science, Kojimachi, Chiyoda, Tokyo 102-0083 Japan
| | - Hiroo Imai
- />Primate Research Institute, Kyoto University, Kanrin, Inuyama, Aichi 484-8506 Japan
| | - Kiyokazu Agata
- />Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo, Kyoto 606-8502 Japan
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Abstract
The mammalian olfactory system detects a plethora of environmental chemicals that are perceived as odors or stimulate instinctive behaviors. Studies using odorant receptor (OR) genes have provided insight into the molecular and organizational strategies underlying olfaction in mice. One important unanswered question, however, is whether these strategies are conserved in primates. To explore this question, we examined the macaque, a higher primate phylogenetically close to humans. Here we report that the organization of sensory inputs in the macaque nose resembles that in mouse in some respects, but not others. As in mouse, neurons with different ORs are interspersed in the macaque nose, and there are spatial zones that differ in their complement of ORs and extend axons to different domains in the olfactory bulb of the brain. However, whereas the mouse has multiple discrete band-like zones, the macaque appears to have only two broad zones. It is unclear whether the organization of OR inputs in a rodent/primate common ancestor degenerated in primates or, alternatively became more sophisticated in rodents. The mouse nose has an additional small family of chemosensory receptors, called trace amine-associated receptors (TAARs), which may detect social cues. Here we find that TAARs are also expressed in the macaque nose, suggesting that TAARs may also play a role in human olfactory perception. We further find that one human TAAR responds to rotten fish, suggesting a possible role as a sentinel to discourage ingestion of food harboring pathogenic microorganisms.
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Login H, Butowt R, Bohm S. Activity-dependent and graded BACE1 expression in the olfactory epithelium is mediated by the retinoic acid metabolizing enzyme CYP26B1. Brain Struct Funct 2014; 220:2143-57. [PMID: 24797530 DOI: 10.1007/s00429-014-0783-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 04/17/2014] [Indexed: 11/24/2022]
Abstract
It is well established that environmental influences play a key role in sculpting neuronal connectivity in the brain. One example is the olfactory sensory map of topographic axonal connectivity. While intrinsic odorant receptor signaling in olfactory sensory neurons (OSN) determines anterior-posterior counter gradients of the axonal guidance receptors Neuropilin-1 and Plexin-A1, little is known about stimulus-dependent gradients of protein expression, which correlates with the functional organization of the olfactory sensory map along its dorsomedial (DM)-ventrolateral (VL) axis. Deficiency of the Alzheimer's β-secretase BACE1, which is expressed in a DM(low)-VL(high) gradient, results in OSN axon targeting errors in a DM > VL and gene dose-dependent manner. We show that expression of BACE1 and the all-trans retinoic acid (RA)-degrading enzyme Cyp26B1 form DM-VL counter gradients in the olfactory epithelium. Analyses of mRNA and protein levels in OSNs after naris occlusion, in mice deficient in the olfactory cyclic nucleotide-gated channel and in relation to onset of respiration, show that BACE1 and Cyp26B1 expression in OSNs inversely depend on neuronal activity. Overexpression of a Cyp26B1 or presence of a dominant negative RA receptor transgene selectively in OSNs, inhibit BACE1 expression while leaving the DM(low)-VL(high) gradient of the axonal guidance protein Neuropilin-2 intact. We conclude that stimulus-dependent neuronal activity can control the expression of the RA catabolic enzyme Cyp26B1 and downstream genes such as BACE1. This result is pertinent to an understanding of the mechanisms by which a topographic pattern of connectivity is achieved and modified as a consequence of graded gene expression and sensory experience.
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Affiliation(s)
- Hande Login
- Department of Molecular Biology, Umeå University, 901 87, Umeå, Sweden
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43
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Single cell RT-PCR identification of odorant receptors expressed by olfactory neurons. Methods Mol Biol 2013. [PMID: 23585038 DOI: 10.1007/978-1-62703-377-0_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Mammals have between 400 and 1,300 functional odorant receptor (OR) genes in their genomes. Each olfactory sensory neuron in the nose expresses only one single type of OR out of this vast repertoire. The OR expressed by an olfactory sensory neuron determines its functional activity and wiring to the olfactory bulb. Therefore, the identification of the OR type expressed by individual neurons contributes to the understanding of the mechanisms of odorant perception. Here we describe the protocol that combines single cell RT-PCR and degenerate PCR to identify the OR expressed by single olfactory neurons. In a primary PCR reaction, cDNAs corresponding to all mRNAs present in a single neuron are synthesized. In a secondary PCR reaction, the cDNAs corresponding to the OR expressed by this neuron are amplified using degenerate primers that match OR sequences.
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James G, Key B, Beverdam A. The E3 ubiquitin ligase Mycbp2 genetically interacts with Robo2 to modulate axon guidance in the mouse olfactory system. Brain Struct Funct 2013; 219:861-74. [PMID: 23525682 DOI: 10.1007/s00429-013-0540-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 03/09/2013] [Indexed: 11/24/2022]
Abstract
The E3 ubiquitin ligase Mycbp2 and it homologues play an important role in axon guidance and synaptogenesis in Drosophila, Caenorhabditis elegans, zebrafish and mouse. Despite this conserved function, the molecular and cellular basis of Mycbp2-dependent axon guidance remains largely unclear. We have examined here the effect of the loss-of-MYCBP2 function on the topography of the olfactory sensory neuron projection from the nasal cavity to the olfactory bulb in mice. A subpopulation of olfactory sensory axons failed to project to the dorsal surface of the olfactory bulb causing abnormal topography in this neural pathway. These defects were similar to the olfactory bulb phenotype in loss-of-ROBO2 function mice. While mice heterozygous for either Mycbp2 or Robo2 were normal, mice double heterozygous for these two genes produced severe defects in the olfactory system. Therefore, Mycbp2 and Robo2 were found to cooperate within a genetic network that has profound effects on axon guidance. The Mycbp2 phenotype could be partly explained by aberrant patterning of olfactory sensory neurons residing in the dorsal compartment of the nasal cavity. Some of these neurons fail to appropriately express Robo2 which is consistent with their aberrant projection to the ventral olfactory bulb. These results provide the first evidence linking an ubiquitin ligase to an axon guidance receptor during pathfinding in the developing mammalian nervous system.
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Affiliation(s)
- G James
- Brain Growth and Regeneration Lab, School of Biomedical Sciences, University of Queensland, Brisbane, 4072, Australia
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Dishevelled proteins are associated with olfactory sensory neuron presynaptic terminals. PLoS One 2013; 8:e56561. [PMID: 23437169 PMCID: PMC3577874 DOI: 10.1371/journal.pone.0056561] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 01/11/2013] [Indexed: 11/28/2022] Open
Abstract
Olfactory sensory neurons (OSNs) project their axons from the olfactory epithelium toward the olfactory bulb (OB) in a heterogeneous and unsorted arrangement. However, as the axons approach the glomerular layer of the OB, axons from OSNs expressing the same odorant receptor (OR) sort and converge to form molecularly homogeneous glomeruli. Axon guidance cues, cell adhesion molecules, and OR induced activity have been implicated in the final targeting of OSN axons to specific glomeruli. Less understood, and often controversial, are the mechanisms used by OSN axons to initially navigate from the OE toward the OB. We previously demonstrated a role for Wnt and Frizzled (Fz) molecules in OSN axon extension and organization within the olfactory nerve. Building on that we now turned our attention to the downstream signaling cascades from Wnt-Fz interactions. Dishevelled (Dvl) is a key molecule downstream of Fz receptors. Three isoforms of Dvl with specific as well as overlapping functions are found in mammals. Here, we show that Dvl-1 expression is restricted to OSNs in the dorsal recess of the nasal cavity, and labels a unique subpopulation of glomeruli. Dvl-2 and Dvl-3 have a widespread distribution in both the OE and OB. Both Dvl-1 and Dvl-2 are associated with intra-glomerular pre-synaptic OSN terminals, suggesting a role in synapse formation/stabilization. Moreover, because Dvl proteins were observed in all OSN axons, we hypothesize that they are important determinants of OSN cell differentiation and axon extension.
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Suzuki J, Yoshizaki K, Kobayashi T, Osumi N. Neural crest-derived horizontal basal cells as tissue stem cells in the adult olfactory epithelium. Neurosci Res 2012; 75:112-20. [PMID: 23228673 DOI: 10.1016/j.neures.2012.11.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2012] [Revised: 10/26/2012] [Accepted: 11/07/2012] [Indexed: 01/04/2023]
Abstract
Horizontal basal cells (HBCs) have garnered attention as tissue stem cells of the olfactory epithelium (OE); however, these cells' exact lineage and their contributions to OE regeneration remain unknown. Neural crest-derived cells (NCDCs) have been shown to possess stem cell properties and to participate in the normal development of the OE. However, the contributions of NCDCs to both normal and regenerating adult OE remain unclear. In this study, we investigated the contribution of NCDCs to the OE, focusing particularly on HBCs. Using immunohistochemistry, we observed the OE of P0-Cre/EGFP mice expressing EGFP-tagged NCDCs at several stages of normal development along with regenerated OE following methimazole treatment. We observed EGFP expression in the HBCs, sustentacular cells (SUSs), Bowman's glands, olfactory receptor neurons (ORNs), and olfactory ensheathing cells of 6-week-old mice. No ectopic Cre expression was identified. Although HBCs at late embryonic stages were placode-derived (i.e., EGFP-negative), we found that EGFP+ HBCs alternatively increased with the decrease of placode-derived HBCs during maturation. In regenerated OE, the percentages of neural crest-derived ORNs and SUSs significantly increased compared with normal OE. These results suggest that NCDCs contribute greatly to the adult HBC population and that they are important for the maintenance of the OE.
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Affiliation(s)
- Jun Suzuki
- Division of Developmental Neuroscience, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, 2-1, Seiryo-Machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
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Tbr2 deficiency in mitral and tufted cells disrupts excitatory-inhibitory balance of neural circuitry in the mouse olfactory bulb. J Neurosci 2012; 32:8831-44. [PMID: 22745484 DOI: 10.1523/jneurosci.5746-11.2012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The olfactory bulb (OB) is the first relay station in the brain where odor information from the olfactory epithelium is integrated, processed through its intrinsic neural circuitry, and conveyed to higher olfactory centers. Compared with profound mechanistic insights into olfactory axon wiring from the nose to the OB, little is known about the molecular mechanisms underlying the formation of functional neural circuitry among various types of neurons inside the OB. T-box transcription factor Tbr2 is expressed in various types of glutamatergic excitatory neurons in the brain including the OB projection neurons, mitral and tufted cells. Here we generated conditional knockout mice in which the Tbr2 gene is inactivated specifically in mitral and tufted cells from late embryonic stages. Tbr2 deficiency caused cell-autonomous changes in molecular expression including a compensatory increase of another T-box member, Tbr1, and a concomitant shift of vesicular glutamate transporter (VGluT) subtypes from VGluT1 to VGluT2. Tbr2-deficient mitral and tufted cells also exhibited anatomical abnormalities in their dendritic morphology and projection patterns. Additionally, several non-cell-autonomous phenotypes were observed in parvalbumin-, calbindin-, and 5T4-positive GABAergic interneurons. Furthermore, the number of dendrodendritic reciprocal synapses between mitral/tufted cells and GABAergic interneurons was significantly reduced. Upon stimulation with odorants, larger numbers of mitral and tufted cells were activated in Tbr2 conditional knockout mice. These results suggest that Tbr2 is required for not only the proper differentiation of mitral and tufted cells, but also for the establishment of functional neuronal circuitry in the OB and maintenance of excitatory-inhibitory balance crucial for odor information processing.
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Abstract
Odor signals received by odorant receptors (ORs) expressed by olfactory sensory neurons (OSNs) in the olfactory epithelium (OE) are represented as an odor map in the olfactory bulb (OB). In the mouse, there are ~1,000 different OR species, and each OSN expresses only one functional OR gene in a monoallelic manner. Furthermore, OSN axons expressing the same type of OR converge on a specific target site in the OB, forming a glomerular structure. Because each glomerulus represents a single OR species, and a single odorant can interact with multiple OR species, odor signals received in the OE are converted into a topographic map of multiple glomeruli activated with varying magnitudes. Here we review recent progress in the study of the mammalian olfactory system, focusing on the formation of the olfactory map and the transmission of topographical information in the OB to the olfactory cortex to elicit various behaviors.
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Affiliation(s)
- Kensaku Mori
- Department of Physiology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan.
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Abaffy T, Defazio AR. The location of olfactory receptors within olfactory epithelium is independent of odorant volatility and solubility. BMC Res Notes 2011; 4:137. [PMID: 21548958 PMCID: PMC3118157 DOI: 10.1186/1756-0500-4-137] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 05/06/2011] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Our objective was to study the pattern of olfactory receptor expression within the dorsal and ventral regions of the mouse olfactory epithelium. We hypothesized that olfactory receptors were distributed based on the chemical properties of their ligands: e.g. receptors for polar, hydrophilic and weakly volatile odorants would be present in the dorsal region of olfactory epithelium; while receptors for non-polar, more volatile odorants would be distributed to the ventral region. To test our hypothesis, we used micro-transplantation of cilia-enriched plasma membranes derived from dorsal or ventral regions of the olfactory epithelium into Xenopus oocytes for electrophysiological characterization against a panel of 100 odorants. FINDINGS Odorants detected by ORs from the dorsal and ventral regions showed overlap in volatility and water solubility. We did not find evidence for a correlation between the solubility and volatility of odorants and the functional expression of olfactory receptors in the dorsal or ventral region of the olfactory epithelia. CONCLUSIONS No simple clustering or relationship between chemical properties of odorants could be associated with the different regions of the olfactory epithelium. These results suggest that the location of ORs within the epithelium is not organized based on the physico-chemical properties of their ligands.
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Affiliation(s)
- Tatjana Abaffy
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, 1600 NW 10thAve, Miami, 33136, Fl, USA.
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50
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Hyperpolarization-activated cyclic nucleotide-gated channels in olfactory sensory neurons regulate axon extension and glomerular formation. J Neurosci 2011; 30:16498-508. [PMID: 21147989 DOI: 10.1523/jneurosci.4225-10.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mechanisms influencing the development of olfactory bulb glomeruli are poorly understood. While odor receptors (ORs) play an important role in olfactory sensory neuron (OSN) axon targeting/coalescence (Mombaerts et al., 1996; Wang et al., 1998; Feinstein and Mombaerts, 2004), recent work showed that G protein activation alone is sufficient to induce OSN axon coalescence (Imai et al., 2006; Chesler et al., 2007), suggesting an activity-dependent mechanism in glomerular development. Consistent with these data, OSN axon projections and convergence are perturbed in mice deficient for adenylyl cyclase III, which is downstream from the OR and catalyzes the conversion of ATP to cAMP. However, in cyclic nucleotide-gated (CNG) channel knock-out mice OSN axons are only transiently perturbed (Lin et al., 2000), suggesting that the CNG channel may not be the sole target of cAMP. This prompted us to investigate an alternative channel, the hyperpolarization-activated, cyclic nucleotide-gated cation channel (HCN), as a potential developmental target of cAMP in OSNs. Here, we demonstrate that HCN channels are developmentally precocious in OSNs and therefore are plausible candidates for affecting OSN axon development. Inhibition of HCN channels in dissociated OSNs significantly reduced neurite outgrowth. Moreover, in HCN1 knock-out mice the formation of glomeruli was delayed in parallel with perturbations of axon organization in the olfactory nerve. These data support the hypothesis that the outgrowth and coalescence of OSN axons is, at least in part, subject to activity-dependent mechanisms mediated via HCN channels.
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