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Sharma N, Narang V, Sood A, Midha V, Senapati S. Reduced expression of Ankyrin-G and E-cadherin in duodenal mucosal biopsy of subjects with celiac disease. Pathol Res Pract 2024; 255:155164. [PMID: 38324966 DOI: 10.1016/j.prp.2024.155164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/18/2024] [Accepted: 01/21/2024] [Indexed: 02/09/2024]
Abstract
Confirmatory diagnosis of celiac disease (CD) include histopathology of duodenal biopsy and tissue trans-glutaminase-IgA. Identification of tissue-specific histological markers is warranted to improve the diagnosis. A genetic study in CD identified the association of ankyrin-G that connects E-cadherin with β2-spectrin in epithelial cells of the duodenal tissue. We attempted to investigate the differential expression of ankyrin-G, E-cadherin and β2-spectrin in duodenal biopsy of CD subjects compared to non-CD controls. Duodenal tissue was collected from 83 study participants, of which 50 were CD, and 33 were non-CD controls. Whole RNA was isolated from 32 CD and 23 non-CD controls from available tissues, and differential mRNA expression was measured using real-time PCR. Tissue sections from 18 CD cases and 10 non-CD controls were immunostained using monoclonal antibodies. Tissue immunohistochemistry were evaluated for differential expression and pattern of expression. RT-PCR revealed significantly reduced expression of ankyrin-G (fold change=0.63; p=0.03) and E-cadherin (fold change=0.50; p=0.02) among CD subjects compared to non-CD controls. Tissue immunohistochemistry confirmed the reduced expression of ankyrin-G and E-cadherin in CD. Differential expression is grossly limited within the outer columnar epithelial cell layer. Expression fold change of E-cadherin was seen to partially correlate with the serum tTG level (r=0.4; p=0.04). In CD, reduced expression of two key cytoskeletal proteins (ankyrin-G and E-cadherin) in duodenum mucosa was observed, which indicates its implication in disease biology and could be tested as a tissue-specific biomarker for CD. Functional studies may unravel the specific contribution of these proteins in CD pathophysiology.
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Affiliation(s)
- Nidhi Sharma
- Immunogenomics Laboratory, Department of Human Genetics and Molecular Medicine, Central University of Punjab, Ghudda-151401, Bathinda, Punjab, India
| | - Vikram Narang
- Department of Pathology, Dayanand Medical College and Hospital, Ludhiana 141001, Punjab, India
| | - Ajit Sood
- Department of Gastroenterology, Dayanand Medical College and Hospital, Ludhiana 141001, Punjab, India
| | - Vandana Midha
- Department of Medicine, Dayanand Medical College and Hospital, Ludhiana 141001, Punjab, India
| | - Sabyasachi Senapati
- Immunogenomics Laboratory, Department of Human Genetics and Molecular Medicine, Central University of Punjab, Ghudda-151401, Bathinda, Punjab, India.
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Navarro-Martínez A, Vicente-García C, Carvajal JJ. NMJ-related diseases beyond the congenital myasthenic syndromes. Front Cell Dev Biol 2023; 11:1216726. [PMID: 37601107 PMCID: PMC10436495 DOI: 10.3389/fcell.2023.1216726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 07/21/2023] [Indexed: 08/22/2023] Open
Abstract
Neuromuscular junctions (NMJs) are a special type of chemical synapse that transmits electrical stimuli from motor neurons (MNs) to their innervating skeletal muscle to induce a motor response. They are an ideal model for the study of synapses, given their manageable size and easy accessibility. Alterations in their morphology or function lead to neuromuscular disorders, such as the congenital myasthenic syndromes, which are caused by mutations in proteins located in the NMJ. In this review, we highlight novel potential candidate genes that may cause or modify NMJs-related pathologies in humans by exploring the phenotypes of hundreds of mouse models available in the literature. We also underscore the fact that NMJs may differ between species, muscles or even sexes. Hence the importance of choosing a good model organism for the study of NMJ-related diseases: only taking into account the specific features of the mammalian NMJ, experimental results would be efficiently translated to the clinic.
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Affiliation(s)
| | - Cristina Vicente-García
- Centro Andaluz de Biología del Desarrollo, CSIC-UPO-JA, Universidad Pablo de Olavide, Sevilla, Spain
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Negro S, Pirazzini M, Rigoni M. Models and methods to study Schwann cells. J Anat 2022; 241:1235-1258. [PMID: 34988978 PMCID: PMC9558160 DOI: 10.1111/joa.13606] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 12/22/2022] Open
Abstract
Schwann cells (SCs) are fundamental components of the peripheral nervous system (PNS) of all vertebrates and play essential roles in development, maintenance, function, and regeneration of peripheral nerves. There are distinct populations of SCs including: (1) myelinating SCs that ensheath axons by a specialized plasma membrane, called myelin, which enhances the conduction of electric impulses; (2) non‐myelinating SCs, including Remak SCs, which wrap bundles of multiple axons of small caliber, and perysinaptic SCs (PSCs), associated with motor axon terminals at the neuromuscular junction (NMJ). All types of SCs contribute to PNS regeneration through striking morphological and functional changes in response to nerve injury, are affected in peripheral neuropathies and show abnormalities and a diminished plasticity during aging. Therefore, methodological approaches to study and manipulate SCs in physiological and pathophysiological conditions are crucial to expand the present knowledge on SC biology and to devise new therapeutic strategies to counteract neurodegenerative conditions and age‐derived denervation. We present here an updated overview of traditional and emerging methodologies for the study of SCs for scientists approaching this research field.
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Affiliation(s)
- Samuele Negro
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Marco Pirazzini
- Department of Biomedical Sciences, University of Padua, Padua, Italy.,CIR-Myo, Centro Interdipartimentale di Ricerca di Miologia, University of Padua, Padova, Italy
| | - Michela Rigoni
- Department of Biomedical Sciences, University of Padua, Padua, Italy.,CIR-Myo, Centro Interdipartimentale di Ricerca di Miologia, University of Padua, Padova, Italy
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Castro R, Taetzsch T, Vaughan SK, Godbe K, Chappell J, Settlage RE, Valdez G. Specific labeling of synaptic schwann cells reveals unique cellular and molecular features. eLife 2020; 9:e56935. [PMID: 32584256 PMCID: PMC7316509 DOI: 10.7554/elife.56935] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 06/08/2020] [Indexed: 12/14/2022] Open
Abstract
Perisynaptic Schwann cells (PSCs) are specialized, non-myelinating, synaptic glia of the neuromuscular junction (NMJ), that participate in synapse development, function, maintenance, and repair. The study of PSCs has relied on an anatomy-based approach, as the identities of cell-specific PSC molecular markers have remained elusive. This limited approach has precluded our ability to isolate and genetically manipulate PSCs in a cell specific manner. We have identified neuron-glia antigen 2 (NG2) as a unique molecular marker of S100β+ PSCs in skeletal muscle. NG2 is expressed in Schwann cells already associated with the NMJ, indicating that it is a marker of differentiated PSCs. Using a newly generated transgenic mouse in which PSCs are specifically labeled, we show that PSCs have a unique molecular signature that includes genes known to play critical roles in PSCs and synapses. These findings will serve as a springboard for revealing drivers of PSC differentiation and function.
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Affiliation(s)
- Ryan Castro
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown UniversityProvidenceUnited States
- Neuroscience Graduate Program, Brown UniversityProvidenceUnited States
| | - Thomas Taetzsch
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown UniversityProvidenceUnited States
| | - Sydney K Vaughan
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown UniversityProvidenceUnited States
| | - Kerilyn Godbe
- Fralin Biomedical Research Institute at Virginia Tech CarilionRoanokeUnited States
| | - John Chappell
- Fralin Biomedical Research Institute at Virginia Tech CarilionRoanokeUnited States
| | - Robert E Settlage
- Department of Advanced Research Computing, Virginia TechBlacksburgUnited States
| | - Gregorio Valdez
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown UniversityProvidenceUnited States
- Center for Translational Neuroscience, Robert J. and Nancy D. Carney Institute for Brain Science and Brown Institute for Translational Science, Brown UniversityProvidenceUnited States
- Department of Neurology, Warren Alpert Medical School of Brown UniversityProvidenceUnited States
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Neve A, Trüb J, Saxena S, Schümperli D. Central and peripheral defects in motor units of the diaphragm of spinal muscular atrophy mice. Mol Cell Neurosci 2016; 70:30-41. [PMID: 26621405 DOI: 10.1016/j.mcn.2015.11.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 10/30/2015] [Accepted: 11/23/2015] [Indexed: 01/08/2023] Open
Abstract
Spinal muscular atrophy (SMA) is characterized by motoneuron loss and muscle weakness. However, the structural and functional deficits that lead to the impairment of the neuromuscular system remain poorly defined. By electron microscopy, we previously found that neuromuscular junctions (NMJs) and muscle fibres of the diaphragm are among the earliest affected structures in the severe mouse SMA model. Because of certain anatomical features, i.e. its thinness and its innervation from the cervical segments of the spinal cord, the diaphragm is particularly suitable to characterize both central and peripheral events. Here we show by immunohistochemistry that, at postnatal day 3, the cervical motoneurons of SMA mice receive less stimulatory synaptic inputs. Moreover, their mitochondria become less elongated which might represent an early stage of degeneration. The NMJs of the diaphragm of SMA mice show a loss of synaptic vesicles and active zones. Moreover, the partly innervated endplates lack S100 positive perisynaptic Schwann cells (PSCs). We also demonstrate the feasibility of comparing the proteomic composition between diaphragm regions enriched and poor in NMJs. By this approach we have identified two proteins that are significantly upregulated only in the NMJ-specific regions of SMA mice. These are apoptosis inducing factor 1 (AIFM1), a mitochondrial flavoprotein that initiates apoptosis in a caspase-independent pathway, and four and a half Lim domain protein 1 (FHL1), a regulator of skeletal muscle mass that has been implicated in several myopathies.
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Affiliation(s)
- Anuja Neve
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, 3012 Bern, Switzerland
| | - Judith Trüb
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
| | - Smita Saxena
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
| | - Daniel Schümperli
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland.
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Ko CP, Robitaille R. Perisynaptic Schwann Cells at the Neuromuscular Synapse: Adaptable, Multitasking Glial Cells. Cold Spring Harb Perspect Biol 2015; 7:a020503. [PMID: 26430218 PMCID: PMC4588062 DOI: 10.1101/cshperspect.a020503] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The neuromuscular junction (NMJ) is engineered to be a highly reliable synapse to carry the control of the motor commands of the nervous system over the muscles. Its development, organization, and synaptic properties are highly structured and regulated to support such reliability and efficacy. Yet, the NMJ is also highly plastic, able to react to injury and adapt to changes. This balance between structural stability and synaptic efficacy on one hand and structural plasticity and repair on another hand is made possible by the intricate regulation of perisynaptic Schwann cells, glial cells at this synapse. They regulate both the efficacy and structural plasticity of the NMJ in a dynamic, bidirectional manner owing to their ability to decode synaptic transmission and by their interactions via trophic-related factors.
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Affiliation(s)
- Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520
| | - Richard Robitaille
- Département de Neurosciences, Université de Montréal, Montréal, Québec H3C 3J7, Canada Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec H3C 3J7, Canada
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Darabid H, Perez-Gonzalez AP, Robitaille R. Neuromuscular synaptogenesis: coordinating partners with multiple functions. Nat Rev Neurosci 2014; 15:630-1. [DOI: 10.1038/nrn3821] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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de Carlos F, Cobo J, Macías E, Feito J, Cobo T, Calavia M, García-Suárez O, Vega J. The Sensory Innervation of the Human Pharynx: Searching for Mechanoreceptors. Anat Rec (Hoboken) 2013; 296:1735-46. [DOI: 10.1002/ar.22792] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 07/16/2013] [Indexed: 12/30/2022]
Affiliation(s)
- F. de Carlos
- Departamento de Cirugía y Especialidades Médicos-Quirúrgicas; Universidad de Oviedo; Oviedo Spain
- Instituto Asturiano de Odontología; Oviedo Spain
| | - J. Cobo
- Departamento de Cirugía y Especialidades Médicos-Quirúrgicas; Universidad de Oviedo; Oviedo Spain
- Instituto Asturiano de Odontología; Oviedo Spain
| | - E. Macías
- Instituto Asturiano de Odontología; Oviedo Spain
| | - J. Feito
- Departamento de Morfología y Biología Celular; Universidad de Oviedo; Oviedo Spain
- Servicio de Anatomía Patológica; Hospital Universitario Central de Asturias; Oviedo Spain
| | - T. Cobo
- Instituto Asturiano de Odontología; Oviedo Spain
| | - M.G. Calavia
- Departamento de Morfología y Biología Celular; Universidad de Oviedo; Oviedo Spain
| | - O. García-Suárez
- Departamento de Morfología y Biología Celular; Universidad de Oviedo; Oviedo Spain
| | - J.A. Vega
- Departamento de Morfología y Biología Celular; Universidad de Oviedo; Oviedo Spain
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Caillol G, Vacher H, Musarella M, Bellouze S, Dargent B, Autillo-Touati A. Motor endplate disease affects neuromuscular junction maturation. Eur J Neurosci 2012; 36:2400-8. [DOI: 10.1111/j.1460-9568.2012.08164.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Chen EI, McClatchy D, Park SK, Yates JR. Comparisons of mass spectrometry compatible surfactants for global analysis of the mammalian brain proteome. Anal Chem 2008; 80:8694-701. [PMID: 18937422 DOI: 10.1021/ac800606w] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Methods for the global analysis of protein expression offer an approach to study the molecular basis of disease. Studies of protein expression in tissue, such as brain, are complicated by the need for efficient and unbiased digestion of proteins that permit identification of peptides by shotgun proteomic methods. In particular, identification and characterization of less abundant membrane proteins has been of great interest for studies of brain physiology, but often proteins of interest are of low abundance or exist in multiple isoforms. Parsing protein isoforms as a function of disease will be essential. In this study, we develop a digestion scheme using detergents compatible with mass spectrometry that improves membrane protein identification from brain tissue. We show the modified procedure yields close to 5,000 protein identifications from 1.8 mg of rat brain homogenate with an average of 25% protein sequence coverage. This procedure achieves a remarkable reduction in the amount of starting material required to observe a broad spectrum of membrane proteins. Among the proteins identified from a mammalian brain homogenate, 1897 (35%) proteins are annotated by Gene Ontology as membrane proteins, and 1225 (22.6%) proteins are predicted to contain at least one transmembrane domain. Membrane proteins identified included neurotransmitter receptors and ion channels implicated in important physiological functions and disease.
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Affiliation(s)
- Emily I Chen
- Department of Chemical Physiology, The Scripps Research Institute, California 92037, USA
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12
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Feng Z, Ko CP. The Role of Glial Cells in the Formation and Maintenance of the Neuromuscular Junction. Ann N Y Acad Sci 2008; 1132:19-28. [DOI: 10.1196/annals.1405.016] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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13
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Fiedler B, Zhang MM, Buczek O, Azam L, Bulaj G, Norton RS, Olivera BM, Yoshikami D. Specificity, affinity and efficacy of iota-conotoxin RXIA, an agonist of voltage-gated sodium channels Na(V)1.2, 1.6 and 1.7. Biochem Pharmacol 2008; 75:2334-44. [PMID: 18486102 DOI: 10.1016/j.bcp.2008.03.019] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Revised: 03/28/2008] [Accepted: 03/31/2008] [Indexed: 12/19/2022]
Abstract
The excitotoxic conopeptide iota-RXIA induces repetitive action potentials in frog motor axons and seizures upon intracranial injection into mice. We recently discovered that iota-RXIA shifts the voltage-dependence of activation of voltage-gated sodium channel Na(V)1.6 to a more hyperpolarized level. Here, we performed voltage-clamp experiments to examine its activity against rodent Na(V)1.1 through Na(V)1.7 co-expressed with the beta1 subunit in Xenopus oocytes and Na(V)1.8 in dissociated mouse DRG neurons. The order of sensitivity to iota-RXIA was Na(V)1.6 > 1.2 > 1.7, and the remaining subtypes were insensitive. The time course of iota-RXIA-activity on Na(V)1.6 during exposure to different peptide concentrations were well fit by single-exponential curves that provided k(obs). The plot of k(obs)versus [iota-RXIA] was linear, consistent with a bimolecular reaction with a K(d) of approximately 3 microM, close to the steady-state EC(50) of approximately 2 microM. iota-RXIA has an unusual residue, D-Phe, and the analog with an L-Phe instead, iota-RXIA[L-Phe44], had a two-fold lower affinity and two-fold faster off-rate than iota-RXIA on Na(V)1.6 and furthermore was inactive on Na(V)1.2. iota-RXIA induced repetitive action potentials in mouse sciatic nerve with conduction velocities of both A- and C-fibers, consistent with the presence of Na(V)1.6 at nodes of Ranvier as well as in unmyelinated axons. Sixteen peptides homologous to iota-RXIA have been identified from a single species of Conus, so these peptides represent a rich family of novel sodium channel-targeting ligands.
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Affiliation(s)
- Brian Fiedler
- Department of Biology, University of Utah, Salt Lake City, Utah 84112, USA
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Rosker C, Lohberger B, Hofer D, Steinecker B, Quasthoff S, Schreibmayer W. The TTX metabolite 4,9-anhydro-TTX is a highly specific blocker of the Nav1.6 voltage-dependent sodium channel. Am J Physiol Cell Physiol 2007; 293:C783-9. [PMID: 17522141 DOI: 10.1152/ajpcell.00070.2007] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The blocking efficacy of 4,9-anhydro-TTX (4,9-ah-TTX) and TTX on several isoforms of voltage-dependent sodium channels, expressed in Xenopus laevis oocytes, was tested (Nav1.2, Nav1.3, Nav1.4, Nav1.5, Nav1.6, Nav1.7, and Nav1.8). Generally, TTX was 40–231 times more effective, when compared with 4,9-ah-TTX, on a given isoform. An exception was Nav1.6, where 4,9-ah-TTX in nanomole per liter concentrations sufficed to result in substantial block, indicating that 4,9-ah-TTX acts specifically at this peculiar isoform. The IC50 values for TTX/4,9-ah-TTX were as follows (in nmol/l): 7.8 ± 1.3/1,260 ± 121 (Nav1.2), 2.8 ± 2.3/341 ± 36 (Nav1.3), 4.5 ± 1.0/988 ± 62 (Nav1.4), 1,970 ± 565/78,500 ± 11,600 (Nav1.5), 3.8 ± 1.5/7.8 ± 2.3 (Nav1.6), 5.5 ± 1.4/1,270 ± 251 (Nav1.7), and 1,330 ± 459/>30,000 (Nav1.8). Analysis of approximal half-maximal doses of both compounds revealed minor effects on voltage-dependent activation only, whereas steady-state inactivation was shifted to more negative potentials by both TTX and 4,9-ah-TTX in the case of the Nav1.6 subunit, but not in the case of other TTX-sensitive ones. TTX shifted steady-state inactivation also to more negative potentials in case of the TTX-insensitive Nav1.5 subunit, where it also exerted profound effects on the time course of recovery from inactivation. Isoform-specific interaction of toxins with ion channels is frequently observed in the case of proteinaceous toxins. Although the sensitivity of Nav1.1 to 4,9-ah-TTX is not known, here we report evidence on a highly isoform-specific TTX analog that may well turn out to be an invaluable tool in research for the identification of Nav1.6-mediated function, but also for therapeutic intervention.
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Affiliation(s)
- Christian Rosker
- Institute for Biophysics, Center for Physiological Medicine, Medical University of Graz, Harrachgasse 21/4, Graz, Austria
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Sage D, Salin P, Alcaraz G, Castets F, Giraud P, Crest M, Mazet B, Clerc N. Nav1.7 and Nav1.3 are the only tetrodotoxin-sensitive sodium channels expressed by the adult guinea pig enteric nervous system. J Comp Neurol 2007; 504:363-78. [PMID: 17663442 DOI: 10.1002/cne.21450] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The types of sodium channels that are expressed by neurons shape the rising phase of action potentials and influence patterns of action potential discharge. With regard to the enteric nervous system (ENS), there is uncertainty about which channels are expressed, and in particular it is unknown whether Na(v)1.7 is present. We designed specific probes for the guinea pig Na(v)1.7 alpha subunit as well as for the other tetrodotoxin (TTX)-sensitive alpha subunits (Na(v)1.1, Na(v)1.2, Na(v)1.3, and Na(v)1.6) in order to perform in situ hybridization (ISH) histochemistry on guinea pig myenteric ganglia. We established that only Na(v)1.7 mRNA and Na(v)1.3 mRNA are expressed in these ganglia. The ISH signal for Na(v)1.7 transcripts was found in seemingly all the myenteric neurons. The expression of the Na(v)1.3 alpha subunit was confirmed by immunohistochemistry in a large proportion (62%) of the myenteric neuron population. This population included enteric sensory neurons. Na(v)1.6 immunoreactivity, absent from myenteric neurons, was detected in glial cells only when a high anti-Na(v)1.6 antibody concentration was used. This suggests that the Na(v)1.6 alpha subunit and mRNA are present only at low levels, which is consistent with the fact that no Na(v)1.6 mRNA could be detected in the ENS by ISH. The fact that adult myenteric neurons are endowed with only two TTX-sensitive alpha subunits, namely, Na(v)1.3 and Na(v)1.7, emphasizes the singularity of the ENS. Both these subunits, known to have slow-inactivation kinetics, are well adapted for generating action potentials from slow excitatory postsynaptic potentials, a mode of synaptic transmission that applies to all ENS neuron types.
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Affiliation(s)
- D Sage
- Laboratoire Neurophysiologie Cellulaire, UMR 6150 Centre National de la Recherche Scientifique (CNRS)/Université de la Méditerranée, Institut Fédératif de Recherche Jean Roche, Faculté de Médecine, 13916 Marseille, France
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