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Gather F, Ihrig-Biedert I, Kohlhas P, Krutenko T, Peitz M, Brüstle O, Pautz A, Kleinert H. A specific, non-immune system-related isoform of the human inducible nitric oxide synthase is expressed during differentiation of human stem cells into various cell types. Cell Commun Signal 2022; 20:47. [PMID: 35392923 PMCID: PMC8991583 DOI: 10.1186/s12964-022-00855-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 03/03/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND NOS2 expression is mostly found in bacteria-exposed or cytokine-treated tissues and is mostly connected to innate immune reactions. There are three isoforms of NOS2 (NOS2-1 to -3). In RNA-seq data sets, analyzing inflammatory gene expression, only expression of the NOS2-1 mRNA isoform is detected. However, the expression of NOS2 in differentiating human pluripotent stems (hPSCs) has not been analyzed yet. METHODS Public available RNA-seq databases were screened for data of hPSCs during differentiation to different target cells. An isoform specific algorithm was used to analyze NOS2 mRNA isoform expression. In addition, we differentiated four different human iPSC cell lines toward cortical neurons and analyzed NOS2 mRNA expression by qRT-PCR and 5'-RACE. The functionality of the NOS2-2 protein was analyzed by transient transfection of expression clones in human DLD1 cells and nitrate measurement in the supernatant of these cells. RESULTS In RNA-seq databases we detected a transient expression of the NOS2 mRNA during the differentiation of hPSCs to cardiomyocytes, chondrocytes, mesenchymal stromal cells, neurons, syncytiotrophoblast cells, and trophoblasts. NOS2 mRNA isoform specific analyses showed, that the transiently expressed NOS2 mRNA in differentiating hPSC (NOS2-2; "diff-iNOS") differ remarkably from the already described NOS2 transcript found in colon or induced islets (NOS2-1; "immuno-iNOS"). Also, analysis of the NOS2 mRNA- and protein expression during the differentiation of four different hiPSC lines towards cortical neurons showed a transient expression of the NOS2 mRNA and NOS2 protein on day 18 of the differentiation course. 5'-RACE experiments and isoform specific qRT-PCR analyses revealed that only the NOS2-2 mRNA isoform was expressed in these experiments. To analyze the functionality of the NOS2-2 protein, we transfected human DLD-1 cells with tetracycline inducible expression clones encoding the NOS2-1- or -2 coding sequence. After induction of the NOS2-1 or -2 mRNA expression by tetracycline a similar nitrate production was measured proofing the functionality of the NOS2-2 protein isoform. CONCLUSIONS Our data show that a differentiation specific NOS2 isoform (NOS2-2) is transiently expressed during differentiation of hPSC. Video Abstract.
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Affiliation(s)
- Fabian Gather
- Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany.,Department of Molecular Embryology, Institute for Anatomy and Cell Biology, Freiburg, Germany
| | - Irmgard Ihrig-Biedert
- Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany
| | - Paul Kohlhas
- Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany
| | - Tamara Krutenko
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Bonn, Germany
| | - Michael Peitz
- Cell Programming Core Facility, Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Bonn, Germany.,Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Bonn, Germany
| | - Oliver Brüstle
- Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Bonn, Germany
| | - Andrea Pautz
- Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany.
| | - Hartmut Kleinert
- Department of Pharmacology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131, Mainz, Germany.
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Tewari D, Sah AN, Bawari S, Nabavi SF, Dehpour AR, Shirooie S, Braidy N, Fiebich BL, Vacca RA, Nabavi SM. Role of Nitric Oxide in Neurodegeneration: Function, Regulation, and Inhibition. Curr Neuropharmacol 2020; 19:114-126. [PMID: 32348225 PMCID: PMC8033982 DOI: 10.2174/1570159x18666200429001549] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/17/2020] [Accepted: 04/24/2020] [Indexed: 12/14/2022] Open
Abstract
Reactive nitrogen species (RNS) and reactive oxygen species (ROS), collectively known as reactive oxygen and nitrogen species (RONS), are the products of normal cellular metabolism and interact with several vital biomolecules including nucleic acid, proteins, and membrane lipids and alter their function in an irreversible manner which can lead to cell death. There is an imperative role for oxidative stress in the pathogenesis of cognitive impairments and the development and progression of neural injury. Elevated production of higher amounts of nitric oxide (NO) takes place in numerous pathological conditions, such as neurodegenerative diseases, inflammation, and ischemia, which occur concurrently with elevated nitrosative/oxidative stress. The enzyme nitric oxide synthase (NOS) is responsible for the generation of NO in different cells by conversion of L-arginine (Arg) to L-citrulline. Therefore, the NO signaling pathway represents a viable therapeutic target. Naturally occurring polyphenols targeting the NO signaling pathway can be of major importance in the field of neurodegeneration and related complications. Here, we comprehensively review the importance of NO and its production in the human body and afterwards highlight the importance of various natural products along with their mechanisms against various neurodegenerative diseases involving their effect on NO production.
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Affiliation(s)
- Devesh Tewari
- Department of Pharmacognosy, School of Pharmaceutical Sciences, Lovely Professional University, Phagwara, Punjab, 144411, India
| | - Archana N Sah
- Department of Pharmaceutical Sciences, Faculty of Technology, Bhimtal Campus, Kumaun University, Nainital, Uttarakhand 263136, India
| | - Sweta Bawari
- School of Pharmacy, Sharda University, Knowledge Park-III, Greater Noida, Uttar Pradesh, 201310, India
| | - Seyed F Nabavi
- Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran 1435916471, Iran
| | - Ahmad R Dehpour
- Department of Pharmacology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Samira Shirooie
- Pharmaceutical Sciences Research Center, Health Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Nady Braidy
- Centre for Healthy Brain Ageing, School of Psychiatry, University of New South Wales, Australia
| | - Bernd L Fiebich
- Neuroimmunology and Neurochemistry Research Group, Department of Psychiatry and Psychotherapy, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Rosa A Vacca
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, National Council of Research, Bari, Italy
| | - Seyed M Nabavi
- Applied Biotechnology Research Center, Baqiyatallah University of Medical Sciences, Tehran 1435916471, Iran
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Santos AI, Lourenço AS, Simão S, Marques da Silva D, Santos DF, Onofre de Carvalho AP, Pereira AC, Izquierdo-Álvarez A, Ramos E, Morato E, Marina A, Martínez-Ruiz A, Araújo IM. Identification of new targets of S-nitrosylation in neural stem cells by thiol redox proteomics. Redox Biol 2020; 32:101457. [PMID: 32088623 PMCID: PMC7038503 DOI: 10.1016/j.redox.2020.101457] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/05/2020] [Accepted: 02/06/2020] [Indexed: 01/09/2023] Open
Abstract
Nitric oxide (NO) is well established as a regulator of neurogenesis. NO increases the proliferation of neural stem cells (NSC), and is essential for hippocampal injury-induced neurogenesis following an excitotoxic lesion. One of the mechanisms underlying non-classical NO cell signaling is protein S-nitrosylation. This post-translational modification consists in the formation of a nitrosothiol group (R-SNO) in cysteine residues, which can promote formation of other oxidative modifications in those cysteine residues. S-nitrosylation can regulate many physiological processes, including neuronal plasticity and neurogenesis. In this work, we aimed to identify S-nitrosylation targets of NO that could participate in neurogenesis. In NSC, we identified a group of proteins oxidatively modified using complementary techniques of thiol redox proteomics. S-nitrosylation of some of these proteins was confirmed and validated in a seizure mouse model of hippocampal injury and in cultured hippocampal stem cells. The identified S-nitrosylated proteins are involved in the ERK/MAPK pathway and may be important targets of NO to enhance the proliferation of NSC.
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Affiliation(s)
- Ana Isabel Santos
- Centre for Biomedical Research, CBMR, University of Algarve, 8005-139, Faro, Portugal; Department of Biomedical Sciences and Medicine, University of Algarve, 8005-139, Faro, Portugal; Algarve Biomedical Center, University of Algarve, 8005-139, Faro, Portugal; Centre for Neuroscience and Cell Biology, University of Coimbra, 3004-527, Coimbra, Portugal
| | - Ana Sofia Lourenço
- Centre for Biomedical Research, CBMR, University of Algarve, 8005-139, Faro, Portugal; Department of Biomedical Sciences and Medicine, University of Algarve, 8005-139, Faro, Portugal; Algarve Biomedical Center, University of Algarve, 8005-139, Faro, Portugal; Centre for Neuroscience and Cell Biology, University of Coimbra, 3004-527, Coimbra, Portugal
| | - Sónia Simão
- Centre for Biomedical Research, CBMR, University of Algarve, 8005-139, Faro, Portugal; Department of Biomedical Sciences and Medicine, University of Algarve, 8005-139, Faro, Portugal; Algarve Biomedical Center, University of Algarve, 8005-139, Faro, Portugal
| | - Dorinda Marques da Silva
- Centre for Biomedical Research, CBMR, University of Algarve, 8005-139, Faro, Portugal; Algarve Biomedical Center, University of Algarve, 8005-139, Faro, Portugal
| | - Daniela Filipa Santos
- Centre for Biomedical Research, CBMR, University of Algarve, 8005-139, Faro, Portugal; Algarve Biomedical Center, University of Algarve, 8005-139, Faro, Portugal
| | | | - Ana Catarina Pereira
- Department of Biomedical Sciences and Medicine, University of Algarve, 8005-139, Faro, Portugal
| | - Alicia Izquierdo-Álvarez
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Princesa (IIS-IP), 28006, Madrid, Spain
| | - Elena Ramos
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Princesa (IIS-IP), 28006, Madrid, Spain
| | - Esperanza Morato
- Servicio de Proteómica, Centro de Biología Molecular Severo Ochoa (CBMSO), Universidad Autónoma de Madrid (UAM) & Consejo Superior de Investigaciones Científicas (CSIC), 28049, Madrid, Spain
| | - Anabel Marina
- Servicio de Proteómica, Centro de Biología Molecular Severo Ochoa (CBMSO), Universidad Autónoma de Madrid (UAM) & Consejo Superior de Investigaciones Científicas (CSIC), 28049, Madrid, Spain
| | - Antonio Martínez-Ruiz
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Princesa (IIS-IP), 28006, Madrid, Spain; Unidad de Investigación, Hospital Universitario Santa Cristina, Instituto de Investigación Sanitaria Princesa (IIS-IP), 28009, Madrid, Spain; Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad Complutense de Madrid, 28040, Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain.
| | - Inês Maria Araújo
- Centre for Biomedical Research, CBMR, University of Algarve, 8005-139, Faro, Portugal; Department of Biomedical Sciences and Medicine, University of Algarve, 8005-139, Faro, Portugal; Algarve Biomedical Center, University of Algarve, 8005-139, Faro, Portugal.
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Abstract
The olfactory system is one of a few areas in the nervous system which is capable of regeneration throughout the life. Olfactory sensory neurons reside in the nasal cavity are continuously replenished with new neurons arising from stem cells. Some factors such as aging, neurodegenerative diseases, head trauma, brain tumor extraction and infection cause olfactory dysfunction which significantly influences physical wellbeing, quality of life, mental health, nutritional status, memory processes, identifying danger and is associated with increased mortality. Therefore, finding a treatment to improve olfactory dysfunction is needed. Recent research efforts in the field have shown some very promising new approaches to treat olfactory dysfunction. This review explores the current studies that have addressed therapeutic approaches to improve olfactory neuron regeneration based on cell transplantation therapy, modulation of physiological olfactory dysfunction and drug treatments.
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Affiliation(s)
- Kate Beecher
- School of Biomedical Science, Queensland University of Technology; Institute of Health and Biomedical Innovation, Queensland University of Technology; Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Brisbane, Queensland, Australia
| | - James A St John
- Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery; Menzies Health Institute Queensland, Griffith University, Brisbane, Queensland, Australia
| | - Fatemeh Chehrehasa
- School of Biomedical Science, Queensland University of Technology; Institute of Health and Biomedical Innovation, Queensland University of Technology; Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith Institute for Drug Discovery, Griffith University, Brisbane, Queensland, Australia
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Roles of Nitric Oxide Synthase Isoforms in Neurogenesis. Mol Neurobiol 2017; 55:2645-2652. [PMID: 28421538 DOI: 10.1007/s12035-017-0513-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 04/04/2017] [Indexed: 10/19/2022]
Abstract
Nitric oxide (NO), a free radical gas, acts as a neurotransmitter or neuromodulator in the central nervous system (CNS). It has been widely explored as a mediator of neuroinflammation, neuronal damages, and neurodegeneration at its pathological levels. Recently, increasing evidence suggests that NO plays key roles in mediating adult neurogenesis, the process of neural stem cells (NSCs) to generate newborn neurons for replacing damaged neurons or maintaining the function of the brain. NO synthase (NOS) is a major enzyme catalyzing the generation of NO in the brain. Recent studies indicate that three homologous NOS isoforms are involved in the proliferation of NSCs and neurogenesis. Therefore, the impact of NOS isoforms on NSC functions needs to be elucidated. Here, we summarize the studies on the role of NO and NOS with different isoforms in NSC proliferation and neurogenesis with the focus on introducing action mechanisms involved in the regulation of NSC function. This growing research area provides the new insight into controlling NSC function via regulating NO microenvironment in the brain. It also provides the evidence on targeting NOS for the treatment of brain diseases.
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Barton MJ, John JS, Clarke M, Wright A, Ekberg J. The Glia Response after Peripheral Nerve Injury: A Comparison between Schwann Cells and Olfactory Ensheathing Cells and Their Uses for Neural Regenerative Therapies. Int J Mol Sci 2017; 18:E287. [PMID: 28146061 PMCID: PMC5343823 DOI: 10.3390/ijms18020287] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Revised: 01/14/2017] [Accepted: 01/17/2017] [Indexed: 01/04/2023] Open
Abstract
The peripheral nervous system (PNS) exhibits a much larger capacity for regeneration than the central nervous system (CNS). One reason for this difference is the difference in glial cell types between the two systems. PNS glia respond rapidly to nerve injury by clearing debris from the injury site, supplying essential growth factors and providing structural support; all of which enhances neuronal regeneration. Thus, transplantation of glial cells from the PNS is a very promising therapy for injuries to both the PNS and the CNS. There are two key types of PNS glia: olfactory ensheathing cells (OECs), which populate the olfactory nerve, and Schwann cells (SCs), which are present in the rest of the PNS. These two glial types share many similar morphological and functional characteristics but also exhibit key differences. The olfactory nerve is constantly turning over throughout life, which means OECs are continuously stimulating neural regeneration, whilst SCs only promote regeneration after direct injury to the PNS. This review presents a comparison between these two PNS systems in respect to normal physiology, developmental anatomy, glial functions and their responses to injury. A thorough understanding of the mechanisms and differences between the two systems is crucial for the development of future therapies using transplantation of peripheral glia to treat neural injuries and/or disease.
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Affiliation(s)
- Matthew J Barton
- Menzies Health Institute Queensland, Griffith University, Nathan QLD 4111, Australia.
- Clem Jones Centre for Neurobiology & Stem Cell Research, Griffith University, Nathan QLD 4111, Australia.
| | - James St John
- Menzies Health Institute Queensland, Griffith University, Nathan QLD 4111, Australia.
- Clem Jones Centre for Neurobiology & Stem Cell Research, Griffith University, Nathan QLD 4111, Australia.
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111, Australia.
| | - Mary Clarke
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111, Australia.
| | - Alison Wright
- Faculty of Health and Medical Science, Bond University, Robina, QLD 4226, Australia.
| | - Jenny Ekberg
- Clem Jones Centre for Neurobiology & Stem Cell Research, Griffith University, Nathan QLD 4111, Australia.
- Faculty of Health and Medical Science, Bond University, Robina, QLD 4226, Australia.
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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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Li Y, Zang D. The neuron regrowth is associated with the proliferation of neural precursor cells after leukemia inhibitory factor administration following spinal cord injury in mice. PLoS One 2014; 9:e116031. [PMID: 25542011 PMCID: PMC4277544 DOI: 10.1371/journal.pone.0116031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 11/29/2014] [Indexed: 11/28/2022] Open
Abstract
Objectives To explore whether LIF could promote the proliferation of neural precursor cells (NPCs) and to analyze the correlation between increased NPCs and FluoroGold (FG) labeled neurons in mice after spinal cord injury (SCI). Methods Motor behavior was assessed using Rotarod and Platform Hang tests; neurons in the corticospinal and rubrospinal systems were labeled with FG, NPCs were immustained with nestin-FITC conjugate. The numbers of FG-labeled neurons and NPCs were estimated, and the correlation between FG-labeled neurons and NPCs was assessed. Results Mice in the SCI group showed negligible recovery of locomotor behavior; in contrast, mice in the LIF group showed a statically significant improvement. Both FG-labeled neurons and NPCs were significantly increased in the LIF group compared to the SCI group, and this increase in FG-labeled neurons and NPCs showed a clear association above the lesion level. Conclusions LIF could promote locomotive behaviors in mice post-SCI by encouraging the proliferation of NPCs; LIF may in fact be a potential cytokine for the induction of NPCs post-SCI.
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Affiliation(s)
- Yubo Li
- Capital Medical University, Beijing, 100069, China
| | - Dawei Zang
- Department of Neurology, Tianjin First Center Hospital, Tianjin Medical University, Tianjin, 300192, China
- * E-mail:
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Cellular and molecular mechanisms regulating embryonic neurogenesis in the rodent olfactory epithelium. Int J Dev Neurosci 2014; 37:76-86. [PMID: 25003986 DOI: 10.1016/j.ijdevneu.2014.06.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 06/27/2014] [Accepted: 06/28/2014] [Indexed: 02/08/2023] Open
Abstract
Mechanisms that regulate cellular differentiation in developing embryos are maintained across multiple physiological systems, including the nervous system where neurons and glia are generated. The olfactory epithelium, which arises from the olfactory pit, is a stratified tissue in which the stepwise generation of neurons and support cells can easily be assessed and followed during embryogenesis and throughout adulthood. During olfactory epithelium morphogenesis, progenitor cells respond to factors that control their proliferation, survival, and differentiation in order to generate olfactory receptor neurons that detect odorants in the environment and glia-like sustentacular cells. The tight temporal regulation of expression of proneural genes in dividing progenitor cells, including Mash-1, Neurogenin-1, and NeuroD1, plays a central role in the production of olfactory receptor neurons. Multiple factors that either positively or negatively affect the generation of olfactory receptor neurons have been identified and shown to impinge on the transcriptional regulatory network in dividing progenitor cells. Several growth factors, such as FGF-8, act to promote neurogenesis by ensuring survival of progenitor cells that will give rise to olfactory receptor neurons. In contrast, other molecules, including members of the large TGF-β family of proteins, have negative impacts on neurogenesis by restricting progenitor cell proliferation and stalling their differentiation. Since recent reviews have focused on neurogenesis in the regenerating adult olfactory epithelium, this review describes neurogenesis at embryonic stages of olfactory epithelium development and summarizes our current understanding of how both cell intrinsic and extrinsic factors control this process.
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