1
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Vincent PFY, Young ED, Edge ASB, Glowatzki E. Auditory hair cells and spiral ganglion neurons regenerate synapses with refined release properties in vitro. Proc Natl Acad Sci U S A 2024; 121:e2315599121. [PMID: 39058581 PMCID: PMC11294990 DOI: 10.1073/pnas.2315599121] [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: 09/10/2023] [Accepted: 06/12/2024] [Indexed: 07/28/2024] Open
Abstract
Ribbon synapses between inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs) in the inner ear are damaged by noise trauma and with aging, causing "synaptopathy" and hearing loss. Cocultures of neonatal denervated organs of Corti and newly introduced SGNs have been developed to find strategies for improving IHC synapse regeneration, but evidence of the physiological normality of regenerated synapses is missing. This study utilizes IHC optogenetic stimulation and SGN recordings, showing that, when P3-5 denervated organs of Corti are cocultured with SGNs, newly formed IHC/SGN synapses are indeed functional, exhibiting glutamatergic excitatory postsynaptic currents. When using older organs of Corti at P10-11, synaptic activity probed by deconvolution showed more mature release properties, closer to the specialized mode of IHC synaptic transmission crucial for coding the sound signal. This functional assessment of newly formed IHC synapses developed here, provides a powerful tool for testing approaches to improve synapse regeneration.
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Affiliation(s)
- Philippe F. Y. Vincent
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, MD21205
| | - Eric D. Young
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, MD21205
| | - Albert S. B. Edge
- Department of Otolaryngology, Harvard Medical School, Boston, MA02115
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, MA02114
- Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA02115
- Harvard Stem Cell Institute, Cambridge, MA02139
| | - Elisabeth Glowatzki
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD21205
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2
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Früh S, Boudkkazi S, Koppensteiner P, Sereikaite V, Chen LY, Fernandez-Fernandez D, Rem PD, Ulrich D, Schwenk J, Chen Z, Le Monnier E, Fritzius T, Innocenti SM, Besseyrias V, Trovò L, Stawarski M, Argilli E, Sherr EH, van Bon B, Kamsteeg EJ, Iascone M, Pilotta A, Cutrì MR, Azamian MS, Hernández-García A, Lalani SR, Rosenfeld JA, Zhao X, Vogel TP, Ona H, Scott DA, Scheiffele P, Strømgaard K, Tafti M, Gassmann M, Fakler B, Shigemoto R, Bettler B. Monoallelic de novo AJAP1 loss-of-function variants disrupt trans-synaptic control of neurotransmitter release. SCIENCE ADVANCES 2024; 10:eadk5462. [PMID: 38985877 PMCID: PMC11235169 DOI: 10.1126/sciadv.adk5462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 06/04/2024] [Indexed: 07/12/2024]
Abstract
Adherens junction-associated protein 1 (AJAP1) has been implicated in brain diseases; however, a pathogenic mechanism has not been identified. AJAP1 is widely expressed in neurons and binds to γ-aminobutyric acid type B receptors (GBRs), which inhibit neurotransmitter release at most synapses in the brain. Here, we show that AJAP1 is selectively expressed in dendrites and trans-synaptically recruits GBRs to presynaptic sites of neurons expressing AJAP1. We have identified several monoallelic AJAP1 variants in individuals with epilepsy and/or neurodevelopmental disorders. Specifically, we show that the variant p.(W183C) lacks binding to GBRs, resulting in the inability to recruit them. Ultrastructural analysis revealed significantly decreased presynaptic GBR levels in Ajap1-/- and Ajap1W183C/+ mice. Consequently, these mice exhibited reduced GBR-mediated presynaptic inhibition at excitatory and inhibitory synapses, along with impaired synaptic plasticity. Our study reveals that AJAP1 enables the postsynaptic neuron to regulate the level of presynaptic GBR-mediated inhibition, supporting the clinical relevance of loss-of-function AJAP1 variants.
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Affiliation(s)
- Simon Früh
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Sami Boudkkazi
- Institute of Physiology II, University of Freiburg, Hermann-Herderstrasse 7, 79104 Freiburg, Germany
| | - Peter Koppensteiner
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | - Vita Sereikaite
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Li-Yuan Chen
- Department of Biomedical Sciences, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 7, 1005 Lausanne, Switzerland
| | - Diego Fernandez-Fernandez
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Pascal D. Rem
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Daniel Ulrich
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Jochen Schwenk
- Institute of Physiology II, University of Freiburg, Hermann-Herderstrasse 7, 79104 Freiburg, Germany
| | - Ziyang Chen
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Elodie Le Monnier
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | - Thorsten Fritzius
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | | | - Valérie Besseyrias
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Luca Trovò
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Michal Stawarski
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Emanuela Argilli
- Department of Neurology, University of California, San Francisco, San Francisco, CA 94158, USA
- Institute of Human Genetics and Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Elliott H. Sherr
- Department of Neurology, University of California, San Francisco, San Francisco, CA 94158, USA
- Institute of Human Genetics and Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Bregje van Bon
- Department of Human Genetics, Radboud University Medical Center, Nijmegen 6525, Netherlands
| | - Erik-Jan Kamsteeg
- Department of Human Genetics, Radboud University Medical Center, Nijmegen 6525, Netherlands
| | - Maria Iascone
- Laboratorio Genetica Medica, ASST Papa Giovanni XXIII, Bergamo, Italy
| | | | | | - Mahshid S. Azamian
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Andrés Hernández-García
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Seema R. Lalani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jill A. Rosenfeld
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xiaonan Zhao
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Baylor Genetics, Houston, TX 77021, USA
| | - Tiphanie P. Vogel
- Division of Rheumatology, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
- Center for Human Immunobiology, Texas Children's Hospital, Houston, TX 77030, USA
| | - Herda Ona
- Division of Rheumatology, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
- Center for Human Immunobiology, Texas Children's Hospital, Houston, TX 77030, USA
| | - Daryl A. Scott
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Peter Scheiffele
- Biocenter, University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Kristian Strømgaard
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Mehdi Tafti
- Department of Biomedical Sciences, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 7, 1005 Lausanne, Switzerland
| | - Martin Gassmann
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Bernd Fakler
- Institute of Physiology II, University of Freiburg, Hermann-Herderstrasse 7, 79104 Freiburg, Germany
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | - Bernhard Bettler
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
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3
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Carlton AJ, Jeng JY, Grandi FC, De Faveri F, Amariutei AE, De Tomasi L, O'Connor A, Johnson SL, Furness DN, Brown SDM, Ceriani F, Bowl MR, Mustapha M, Marcotti W. BAI1 localizes AMPA receptors at the cochlear afferent post-synaptic density and is essential for hearing. Cell Rep 2024; 43:114025. [PMID: 38564333 DOI: 10.1016/j.celrep.2024.114025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 01/25/2024] [Accepted: 03/15/2024] [Indexed: 04/04/2024] Open
Abstract
Type I spiral ganglion neurons (SGNs) convey sound information to the central auditory pathway by forming synapses with inner hair cells (IHCs) in the mammalian cochlea. The molecular mechanisms regulating the formation of the post-synaptic density (PSD) in the SGN afferent terminals are still unclear. Here, we demonstrate that brain-specific angiogenesis inhibitor 1 (BAI1) is required for the clustering of AMPA receptors GluR2-4 (glutamate receptors 2-4) at the PSD. Adult Bai1-deficient mice have functional IHCs but fail to transmit information to the SGNs, leading to highly raised hearing thresholds. Despite the almost complete absence of AMPA receptor subunits, the SGN fibers innervating the IHCs do not degenerate. Furthermore, we show that AMPA receptors are still expressed in the cochlea of Bai1-deficient mice, highlighting a role for BAI1 in trafficking or anchoring GluR2-4 to the PSDs. These findings identify molecular and functional mechanisms required for sound encoding at cochlear ribbon synapses.
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Affiliation(s)
- Adam J Carlton
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Jing-Yi Jeng
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Fiorella C Grandi
- Sorbonne Université, INSERM, Institute de Myologie, Centre de Recherche en Myologie, 75013 Paris, France
| | | | - Ana E Amariutei
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Lara De Tomasi
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Andrew O'Connor
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Stuart L Johnson
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK; Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, UK
| | - David N Furness
- School of Life Sciences, Keele University, Keele ST5 5BG, UK
| | - Steve D M Brown
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Campus, Oxfordshire OX11 0RD, UK
| | - Federico Ceriani
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Michael R Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Campus, Oxfordshire OX11 0RD, UK
| | - Mirna Mustapha
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK; Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, UK
| | - Walter Marcotti
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK; Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, UK.
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4
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Vincent PF, Young ED, Edge AS, Glowatzki E. Auditory Hair Cells and Spiral Ganglion Neurons Regenerate Synapses with Refined Release Properties In Vitro. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.05.561095. [PMID: 38076928 PMCID: PMC10705289 DOI: 10.1101/2023.10.05.561095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Ribbon synapses between inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs) in the inner ear are damaged by noise trauma and with aging, causing 'synaptopathy 'and hearing loss. Co-cultures of neonatal denervated organs of Corti and newly introduced SGNs have been developed to find strategies for improving IHC synapse regeneration, but evidence of the physiological normality of regenerated synapses is missing. This study utilizes IHC optogenetic stimulation and SGN recordings, showing that newly formed IHC synapses are indeed functional, exhibiting glutamatergic excitatory postsynaptic currents. When older organs of Corti were plated, synaptic activity probed by deconvolution, showed more mature release properties, closer to the highly specialized mode of IHC synaptic transmission that is crucial for coding the sound signal. This newly developed functional assessment of regenerated IHC synapses provides a powerful tool for testing approaches to improve synapse regeneration.
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Affiliation(s)
- Philippe F.Y. Vincent
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, Maryland
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Eric D. Young
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, Maryland
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, Maryland
- Department of Neuroscience, The Johns Hopkins School of Medicine, Baltimore, Maryland
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Albert S.B. Edge
- Department of Otolaryngology, Harvard Medical School, Boston, Massachusetts, USA
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, Massachusetts, USA
- Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, Massachusetts, USA
- Harvard Stem Cell Institute, Cambridge, Massachusetts, USA
| | - Elisabeth Glowatzki
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, Maryland
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, Maryland
- Department of Neuroscience, The Johns Hopkins School of Medicine, Baltimore, Maryland
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5
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Moser T, Karagulyan N, Neef J, Jaime Tobón LM. Diversity matters - extending sound intensity coding by inner hair cells via heterogeneous synapses. EMBO J 2023; 42:e114587. [PMID: 37800695 PMCID: PMC10690447 DOI: 10.15252/embj.2023114587] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 06/26/2023] [Accepted: 08/07/2023] [Indexed: 10/07/2023] Open
Abstract
Our sense of hearing enables the processing of stimuli that differ in sound pressure by more than six orders of magnitude. How to process a wide range of stimulus intensities with temporal precision is an enigmatic phenomenon of the auditory system. Downstream of dynamic range compression by active cochlear micromechanics, the inner hair cells (IHCs) cover the full intensity range of sound input. Yet, the firing rate in each of their postsynaptic spiral ganglion neurons (SGNs) encodes only a fraction of it. As a population, spiral ganglion neurons with their respective individual coding fractions cover the entire audible range. How such "dynamic range fractionation" arises is a topic of current research and the focus of this review. Here, we discuss mechanisms for generating the diverse functional properties of SGNs and formulate testable hypotheses. We postulate that an interplay of synaptic heterogeneity, molecularly distinct subtypes of SGNs, and efferent modulation serves the neural decomposition of sound information and thus contributes to a population code for sound intensity.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Cluster of Excellence “Multiscale Bioimaging of Excitable Cells”GöttingenGermany
| | - Nare Karagulyan
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Hertha Sponer CollegeCluster of Excellence “Multiscale Bioimaging of Excitable Cells” Cluster of ExcellenceGöttingenGermany
| | - Jakob Neef
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Lina María Jaime Tobón
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Hertha Sponer CollegeCluster of Excellence “Multiscale Bioimaging of Excitable Cells” Cluster of ExcellenceGöttingenGermany
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6
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Trigila AP, Castagna VC, Berasain L, Montini D, Rubinstein M, Gomez-Casati ME, Franchini LF. Accelerated Evolution Analysis Uncovers PKNOX2 as a Key Transcription Factor in the Mammalian Cochlea. Mol Biol Evol 2023; 40:msad128. [PMID: 37247388 PMCID: PMC10337857 DOI: 10.1093/molbev/msad128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 04/12/2023] [Accepted: 04/17/2023] [Indexed: 05/31/2023] Open
Abstract
The genetic bases underlying the evolution of morphological and functional innovations of the mammalian inner ear are poorly understood. Gene regulatory regions are thought to play an important role in the evolution of form and function. To uncover crucial hearing genes whose regulatory machinery evolved specifically in mammalian lineages, we mapped accelerated noncoding elements (ANCEs) in inner ear transcription factor (TF) genes and found that PKNOX2 harbors the largest number of ANCEs within its transcriptional unit. Using reporter gene expression assays in transgenic zebrafish, we determined that four PKNOX2-ANCEs drive differential expression patterns when compared with ortholog sequences from close outgroup species. Because the functional role of PKNOX2 in cochlear hair cells has not been previously investigated, we decided to study Pknox2 null mice generated by CRISPR/Cas9 technology. We found that Pknox2-/- mice exhibit reduced distortion product otoacoustic emissions (DPOAEs) and auditory brainstem response (ABR) thresholds at high frequencies together with an increase in peak 1 amplitude, consistent with a higher number of inner hair cells (IHCs)-auditory nerve synapsis observed at the cochlear basal region. A comparative cochlear transcriptomic analysis of Pknox2-/- and Pknox2+/+ mice revealed that key auditory genes are under Pknox2 control. Hence, we report that PKNOX2 plays a critical role in cochlear sensitivity at higher frequencies and that its transcriptional regulation underwent lineage-specific evolution in mammals. Our results provide novel insights about the contribution of PKNOX2 to normal auditory function and to the evolution of high-frequency hearing in mammals.
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Affiliation(s)
- Anabella P Trigila
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Valeria C Castagna
- Facultad de Medicina, Instituto de Farmacología, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Lara Berasain
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Dante Montini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | | | - Lucía F Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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7
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Hindley N, Sanchez Avila A, Henstridge C. Bringing synapses into focus: Recent advances in synaptic imaging and mass-spectrometry for studying synaptopathy. Front Synaptic Neurosci 2023; 15:1130198. [PMID: 37008679 PMCID: PMC10050382 DOI: 10.3389/fnsyn.2023.1130198] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 02/28/2023] [Indexed: 03/17/2023] Open
Abstract
Synapses are integral for healthy brain function and are becoming increasingly recognized as key structures in the early stages of brain disease. Understanding the pathological processes driving synaptic dysfunction will unlock new therapeutic opportunities for some of the most devastating diseases of our time. To achieve this we need a solid repertoire of imaging and molecular tools to interrogate synaptic biology at greater resolution. Synapses have historically been examined in small numbers, using highly technical imaging modalities, or in bulk, using crude molecular approaches. However, recent advances in imaging techniques are allowing us to analyze large numbers of synapses, at single-synapse resolution. Furthermore, multiplexing is now achievable with some of these approaches, meaning we can examine multiple proteins at individual synapses in intact tissue. New molecular techniques now allow accurate quantification of proteins from isolated synapses. The development of increasingly sensitive mass-spectrometry equipment means we can now scan the synaptic molecular landscape almost in totality and see how this changes in disease. As we embrace these new technical developments, synapses will be viewed with clearer focus, and the field of synaptopathy will become richer with insightful and high-quality data. Here, we will discuss some of the ways in which synaptic interrogation is being facilitated by methodological advances, focusing on imaging, and mass spectrometry.
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Affiliation(s)
- Nicole Hindley
- Division of Cellular and Systems Medicine, University of Dundee, Dundee, United Kingdom
| | - Anna Sanchez Avila
- Division of Cellular and Systems Medicine, University of Dundee, Dundee, United Kingdom
- Euan Macdonald Centre for Motor Neuron Disease, University of Edinburgh, Edinburgh, United Kingdom
| | - Christopher Henstridge
- Division of Cellular and Systems Medicine, University of Dundee, Dundee, United Kingdom
- Euan Macdonald Centre for Motor Neuron Disease, University of Edinburgh, Edinburgh, United Kingdom
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8
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Lozier NR, Muscio S, Pal I, Cai HM, Rubio ME. Sex differences in glutamate AMPA receptor subunits mRNA with fast gating kinetics in the mouse cochlea. Front Syst Neurosci 2023; 17:1100505. [PMID: 36936507 PMCID: PMC10017478 DOI: 10.3389/fnsys.2023.1100505] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 01/30/2023] [Indexed: 03/06/2023] Open
Abstract
Evidence shows that females have increased supra-threshold peripheral auditory processing compared to males. This is indicated by larger auditory brainstem responses (ABR) wave I amplitude, which measures afferent spiral ganglion neuron (SGN)-auditory nerve synchrony. However, the underlying molecular mechanisms of this sex difference are mostly unknown. We sought to elucidate sex differences in ABR wave I amplitude by examining molecular markers known to affect synaptic transmission kinetics. Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) mediate fast excitatory transmission in mature SGN afferent synapses. Each AMPAR channel is a tetramer composed of GluA2, 3, and 4 subunits (Gria2, 3, and 4 genes), and those lacking GluA2 subunits have larger currents, are calcium-permeable, and have faster gating kinetics. Moreover, alternatively spliced flip and flop isoforms of each AMPAR subunit affect channel kinetics, having faster kinetics those AMPARs containing Gria3 and Gria4 flop isoforms. We hypothesized that SGNs of females have more fast-gating AMPAR subunit mRNA than males, which could contribute to more temporally precise synaptic transmission and increased SGN synchrony. Our data show that the index of Gria3 relative to Gria2 transcripts on SGN was higher in females than males (females: 48%; males: 43%), suggesting that females have more SGNs with higher Gria3 mRNA relative to Gria2. Analysis of the relative abundance of the flip and flop alternatively spliced isoforms showed that females have a 2-fold increase in fast-gating Gria3 flop mRNA, while males have more slow-gating (2.5-fold) of the flip. We propose that Gria3 may in part mediate greater SGN synchrony in females. Significance Statement: Females of multiple vertebrate species, including fish and mammals, have been reported to have enhanced sound-evoked synchrony of afferents in the auditory nerve. However, the underlying molecular mediators of this physiologic sex difference are unknown. Elucidating potential molecular mechanisms related to sex differences in auditory processing is important for maintaining healthy ears and developing potential treatments for hearing loss in both sexes. This study found that females have a 2-fold increase in Gria3 flop mRNA, a fast-gating AMPA-type glutamate receptor subunit. This difference may contribute to greater neural synchrony in the auditory nerve of female mice compared to males, and this sex difference may be conserved in all vertebrates.
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Affiliation(s)
- Nicholas R. Lozier
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Steven Muscio
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Indra Pal
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Hou-Ming Cai
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, United States
| | - María E. Rubio
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, United States
- Department of Otolaryngology, University of Pittsburgh, Pittsburgh, PA, United States
- Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA, United States
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9
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Rutherford MA, Bhattacharyya A, Xiao M, Cai HM, Pal I, Rubio ME. GluA3 subunits are required for appropriate assembly of AMPAR GluA2 and GluA4 subunits on cochlear afferent synapses and for presynaptic ribbon modiolar-pillar morphology. eLife 2023; 12:e80950. [PMID: 36648432 PMCID: PMC9891727 DOI: 10.7554/elife.80950] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 01/16/2023] [Indexed: 01/18/2023] Open
Abstract
Cochlear sound encoding depends on α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs), but reliance on specific pore-forming subunits is unknown. With 5-week-old male C57BL/6J Gria3-knockout mice (i.e., subunit GluA3KO) we determined cochlear function, synapse ultrastructure, and AMPAR molecular anatomy at ribbon synapses between inner hair cells (IHCs) and spiral ganglion neurons. GluA3KO and wild-type (GluA3WT) mice reared in ambient sound pressure level (SPL) of 55-75 dB had similar auditory brainstem response (ABR) thresholds, wave-1 amplitudes, and latencies. Postsynaptic densities (PSDs), presynaptic ribbons, and synaptic vesicle sizes were all larger on the modiolar side of the IHCs from GluA3WT, but not GluA3KO, demonstrating GluA3 is required for modiolar-pillar synapse differentiation. Presynaptic ribbons juxtaposed with postsynaptic GluA2/4 subunits were similar in quantity, however, lone ribbons were more frequent in GluA3KO and GluA2-lacking synapses were observed only in GluA3KO. GluA2 and GluA4 immunofluorescence volumes were smaller on the pillar side than the modiolar side in GluA3KO, despite increased pillar-side PSD size. Overall, the fluorescent puncta volumes of GluA2 and GluA4 were smaller in GluA3KO than GluA3WT. However, GluA3KO contained less GluA2 and greater GluA4 immunofluorescence intensity relative to GluA3WT (threefold greater mean GluA4:GluA2 ratio). Thus, GluA3 is essential in development, as germline disruption of Gria3 caused anatomical synapse pathology before cochlear output became symptomatic by ABR. We propose the hearing loss in older male GluA3KO mice results from progressive synaptopathy evident in 5-week-old mice as decreased abundance of GluA2 subunits and an increase in GluA2-lacking, GluA4-monomeric Ca2+-permeable AMPARs.
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Affiliation(s)
- Mark A Rutherford
- Department of Otolaryngology, Washington University School of MedicineSt LouisUnited States
| | - Atri Bhattacharyya
- Department of Otolaryngology, Washington University School of MedicineSt LouisUnited States
| | - Maolei Xiao
- Department of Otolaryngology, Washington University School of MedicineSt LouisUnited States
| | - Hou-Ming Cai
- Department of Neurobiology, University of Pittsburgh School of MedicinePittsburghUnited States
| | - Indra Pal
- Department of Neurobiology, University of Pittsburgh School of MedicinePittsburghUnited States
| | - Maria Eulalia Rubio
- Department of Neurobiology, University of Pittsburgh School of MedicinePittsburghUnited States
- Department of Otolaryngology, University of Pittsburgh School of MedicinePittsburghUnited States
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10
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Nolan LS, Chen J, Gonçalves AC, Bullen A, Towers ER, Steel KP, Dawson SJ, Gale JE. Targeted deletion of the RNA-binding protein Caprin1 leads to progressive hearing loss and impairs recovery from noise exposure in mice. Sci Rep 2022; 12:2444. [PMID: 35165318 PMCID: PMC8844073 DOI: 10.1038/s41598-022-05657-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 01/12/2022] [Indexed: 11/25/2022] Open
Abstract
Cell cycle associated protein 1 (Caprin1) is an RNA-binding protein that can regulate the cellular post-transcriptional response to stress. It is a component of both stress granules and neuronal RNA granules and is implicated in neurodegenerative disease, synaptic plasticity and long-term memory formation. Our previous work suggested that Caprin1 also plays a role in the response of the cochlea to stress. Here, targeted inner ear-deletion of Caprin1 in mice leads to an early onset, progressive hearing loss. Auditory brainstem responses from Caprin1-deficient mice show reduced thresholds, with a significant reduction in wave-I amplitudes compared to wildtype. Whilst hair cell structure and numbers were normal, the inner hair cell-spiral ganglion neuron (IHC-SGN) synapse revealed abnormally large post-synaptic GluA2 receptor puncta, a defect consistent with the observed wave-I reduction. Unlike wildtype mice, mild-noise-induced hearing threshold shifts in Caprin1-deficient mice did not recover. Oxidative stress triggered TIA-1/HuR-positive stress granule formation in ex-vivo cochlear explants from Caprin1-deficient mice, showing that stress granules could still be induced. Taken together, these findings suggest that Caprin1 plays a key role in maintenance of auditory function, where it regulates the normal status of the IHC-SGN synapse.
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Affiliation(s)
- Lisa S Nolan
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK
- Wolfson Centre for Age-Related Diseases, King's College London, Guy's Campus, London, SE1 1UL, UK
| | - Jing Chen
- Wolfson Centre for Age-Related Diseases, King's College London, Guy's Campus, London, SE1 1UL, UK
| | | | - Anwen Bullen
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK
| | - Emily R Towers
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK
| | - Karen P Steel
- Wolfson Centre for Age-Related Diseases, King's College London, Guy's Campus, London, SE1 1UL, UK
| | - Sally J Dawson
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.
| | - Jonathan E Gale
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.
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11
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Peineau T, Belleudy S, Pietropaolo S, Bouleau Y, Dulon D. Synaptic Release Potentiation at Aging Auditory Ribbon Synapses. Front Aging Neurosci 2021; 13:756449. [PMID: 34733152 PMCID: PMC8558230 DOI: 10.3389/fnagi.2021.756449] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 09/21/2021] [Indexed: 11/13/2022] Open
Abstract
Age-related hidden hearing loss is often described as a cochlear synaptopathy that results from a progressive degeneration of the inner hair cell (IHC) ribbon synapses. The functional changes occurring at these synapses during aging are not fully understood. Here, we characterized this aging process in IHCs of C57BL/6J mice, a strain which is known to carry a cadherin-23 mutation and experiences early hearing loss with age. These mice, while displaying a large increase in auditory brainstem thresholds due to 50% loss of IHC synaptic ribbons at middle age (postnatal day 365), paradoxically showed enhanced acoustic startle reflex suggesting a hyperacusis-like response. The auditory defect was associated with a large shrinkage of the IHCs' cell body and a drastic enlargement of their remaining presynaptic ribbons which were facing enlarged postsynaptic AMPAR clusters. Presynaptic Ca2+ microdomains and the capacity of IHCs to sustain high rates of exocytosis were largely increased, while on the contrary the expression of the fast-repolarizing BK channels, known to negatively control transmitter release, was decreased. This age-related synaptic plasticity in IHCs suggested a functional potentiation of synaptic transmission at the surviving synapses, a process that could partially compensate the decrease in synapse number and underlie hyperacusis.
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Affiliation(s)
- Thibault Peineau
- Neurophysiologie de la Synapse Auditive, INSERM UMRS 1120, Bordeaux Neurocampus, Université de Bordeaux, Bordeaux, France.,Institut de l'Audition, Centre Institut Pasteur/Inserm, Paris, France
| | - Séverin Belleudy
- Neurophysiologie de la Synapse Auditive, INSERM UMRS 1120, Bordeaux Neurocampus, Université de Bordeaux, Bordeaux, France
| | | | - Yohan Bouleau
- Neurophysiologie de la Synapse Auditive, INSERM UMRS 1120, Bordeaux Neurocampus, Université de Bordeaux, Bordeaux, France.,Institut de l'Audition, Centre Institut Pasteur/Inserm, Paris, France
| | - Didier Dulon
- Neurophysiologie de la Synapse Auditive, INSERM UMRS 1120, Bordeaux Neurocampus, Université de Bordeaux, Bordeaux, France.,Institut de l'Audition, Centre Institut Pasteur/Inserm, Paris, France
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12
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Boero LE, Payne S, Gómez-Casati ME, Rutherford MA, Goutman JD. Noise Exposure Potentiates Exocytosis From Cochlear Inner Hair Cells. Front Synaptic Neurosci 2021; 13:740368. [PMID: 34658832 PMCID: PMC8511412 DOI: 10.3389/fnsyn.2021.740368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 09/10/2021] [Indexed: 11/19/2022] Open
Abstract
Noise-induced hearing loss has gained relevance as one of the most common forms of hearing impairment. The anatomical correlates of hearing loss, principally cell damage and/or death, are relatively well-understood histologically. However, much less is known about the physiological aspects of damaged, surviving cells. Here we addressed the functional consequences of noise exposure on the capacity of inner hair cells (IHCs) to release synaptic vesicles at synapses with spiral ganglion neurons (SGNs). Mice of either sex at postnatal day (P) 15–16 were exposed to 1–12 kHz noise at 120 dB sound pressure level (SPL), for 1 h. Exocytosis was measured by tracking changes in membrane capacitance (ΔCm) from IHCs of the apical cochlea. Upon IHC depolarization to different membrane potentials, ΔCm showed the typical bell-shaped curve that mirrors the voltage dependence of Ca2+ influx, in both exposed and unexposed cells. Surprisingly, from IHCs at 1-day after exposure (d.a.e.), we found potentiation of exocytosis at the peak of the bell-shaped curve. The increase in exocytosis was not accompanied by changes in whole-cell Ca2+ influx, suggesting a modification in coupling between Ca2+ channels and synaptic vesicles. Consistent with this notion, noise exposure also changed the Ca2+-dependence of exocytosis from linear to supralinear. Noise exposure did not cause loss of IHCs, but did result in a small reduction in the number of IHC-SGN synapses at 1-d.a.e. which recovered by 14-d.a.e. In contrast, a strong reduction in auditory brainstem response wave-I amplitude (representing synchronous firing of SGNs) and distortion product otoacoustic emissions (reflecting outer hair cell function) indicated a profound hearing loss at 1- and 14-d.a.e. To determine the role of glutamate release in the noise-induced potentiation of exocytosis, we evaluated vesicular glutamate transporter-3 (Vglut3) knock-out (KO) mice. Unlike WT, IHCs from Vglut3KO mice showed a noise-induced reduction in ΔCm and Ca2+ influx with no change in the Ca2+-dependence of exocytosis. Together, these results indicate that traumatic noise exposure triggers changes of IHC synaptic function including a Vglut3-dependent potentiation of exocytosis.
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Affiliation(s)
- Luis E Boero
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Buenos Aires, Argentina.,Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Shelby Payne
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
| | | | - Mark A Rutherford
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
| | - Juan D Goutman
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Buenos Aires, Argentina
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13
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Petralia RS, Wang YX. Review of Post-embedding Immunogold Methods for the Study of Neuronal Structures. Front Neuroanat 2021; 15:763427. [PMID: 34720893 PMCID: PMC8551803 DOI: 10.3389/fnana.2021.763427] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 09/28/2021] [Indexed: 01/03/2023] Open
Abstract
The post-embedding immunogold (PI) technique for immunolabeling of neuronal tissues utilizing standard thin-section transmission electron microscopy (TEM) continues to be a prime method for understanding the functional localization of key proteins in neuronal function. Its main advantages over other immunolabeling methods for thin-section TEM are (1) fairly accurate and quantifiable localization of proteins in cells; (2) double-labeling of sections using two gold particle sizes; and (3) the ability to perform multiple labeling for different proteins by using adjacent sections. Here we first review in detail a common method for PI of neuronal tissues. This method has two major parts. First, we describe the freeze-substitution embedding method: cryoprotected tissue is frozen in liquid propane via plunge-freezing, and is placed in a freeze-substitution instrument in which the tissue is embedded in Lowicryl at low temperatures. We highlight important aspects of freeze-substitution embedding. Then we outline how thin sections of embedded tissue on grids are labeled with a primary antibody and a secondary gold particle-conjugated antibody, and the particular problems encountered in TEM of PI-labeled sections. In the Discussion, we compare our method both to earlier PI methods and to more recent PI methods used by other laboratories. We also compare TEM immunolabeling using PI vs. various pre-embedding immunolabeling methods, especially relating to neuronal tissue.
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Affiliation(s)
- Ronald S. Petralia
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
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14
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Presynaptic AMPA Receptors in Health and Disease. Cells 2021; 10:cells10092260. [PMID: 34571906 PMCID: PMC8470629 DOI: 10.3390/cells10092260] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/23/2021] [Accepted: 08/26/2021] [Indexed: 01/04/2023] Open
Abstract
AMPA receptors (AMPARs) are ionotropic glutamate receptors that play a major role in excitatory neurotransmission. AMPARs are located at both presynaptic and postsynaptic plasma membranes. A huge number of studies investigated the role of postsynaptic AMPARs in the normal and abnormal functioning of the mammalian central nervous system (CNS). These studies highlighted that changes in the functional properties or abundance of postsynaptic AMPARs are major mechanisms underlying synaptic plasticity phenomena, providing molecular explanations for the processes of learning and memory. Conversely, the role of AMPARs at presynaptic terminals is as yet poorly clarified. Accruing evidence demonstrates that presynaptic AMPARs can modulate the release of various neurotransmitters. Recent studies also suggest that presynaptic AMPARs may possess double ionotropic-metabotropic features and that they are involved in the local regulation of actin dynamics in both dendritic and axonal compartments. In addition, evidence suggests a key role of presynaptic AMPARs in axonal pathology, in regulation of pain transmission and in the physiology of the auditory system. Thus, it appears that presynaptic AMPARs play an important modulatory role in nerve terminal activity, making them attractive as novel pharmacological targets for a variety of pathological conditions.
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15
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Hickman TT, Hashimoto K, Liberman LD, Liberman MC. Cochlear Synaptic Degeneration and Regeneration After Noise: Effects of Age and Neuronal Subgroup. Front Cell Neurosci 2021; 15:684706. [PMID: 34434091 PMCID: PMC8380781 DOI: 10.3389/fncel.2021.684706] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 06/30/2021] [Indexed: 01/24/2023] Open
Abstract
In CBA/CaJ mice, confocal analysis has shown that acoustic overexposure can immediately destroy synapses between auditory-nerve fibers (ANFs) and their peripheral targets, the inner hair cells (IHCs), and that years later, a corresponding number of ANF cell bodies degenerate. In guinea pig, post-exposure disappearance of pre-synaptic ribbons can be equally dramatic, however, post-exposure recovery to near-baseline counts has been reported. Since confocal counts are confounded by thresholding issues, the fall and rise of synaptic ribbon counts could represent “regeneration,” i.e., terminal retraction, re-extension and synaptogenesis, or “recovery,” i.e., down- and subsequent up-regulation of synaptic markers. To clarify, we counted pre-synaptic ribbons, assessed their juxtaposition with post-synaptic receptors, measured the extension of ANF terminals, and quantified the spatial organization and size gradients of these synaptic elements around the hair cell. Present results in guinea pigs exposed as adults (14 months), along with prior results in juveniles (1 month), suggest there is post-exposure neural regeneration in the guinea pig, but not the CBA/CaJ mouse, and that this regenerative capacity extends into adulthood. The results also show, for the first time, that the acute synaptic loss is concentrated on the modiolar side of IHCs, consistent with a selective loss of the high-threshold ANFs with low spontaneous rates. The morphological similarities between the post-exposure neurite extension and synaptogenesis, seen spontaneously in the guinea pig, and in CBA/CaJ only with forced overexpression of neurotrophins, suggest that the key difference may be in the degree of sustained or injury-induced expression of these signaling molecules in the cochlea.
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Affiliation(s)
- Tyler T Hickman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, United States.,Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, United States
| | - Ken Hashimoto
- Department of Otolaryngology-Head and Neck Surgery, Tohoku University School of Medicine, Sendai, Japan
| | - Leslie D Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, United States
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, United States.,Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, United States
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16
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Seewald A, Schönherr S, Hörtnagl H, Ehrlich I, Schmuckermair C, Ferraguti F. Fear Memory Retrieval Is Associated With a Reduction in AMPA Receptor Density at Thalamic to Amygdala Intercalated Cell Synapses. Front Synaptic Neurosci 2021; 13:634558. [PMID: 34295235 PMCID: PMC8290482 DOI: 10.3389/fnsyn.2021.634558] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Accepted: 06/14/2021] [Indexed: 12/12/2022] Open
Abstract
The amygdala plays a crucial role in attaching emotional significance to environmental cues. Its intercalated cell masses (ITC) are tight clusters of GABAergic neurons, which are distributed around the basolateral amygdala complex. Distinct ITC clusters are involved in the acquisition and extinction of conditioned fear responses. Previously, we have shown that fear memory retrieval reduces the AMPA/NMDA ratio at thalamic afferents to ITC neurons within the dorsal medio-paracapsular cluster. Here, we investigate the molecular mechanisms underlying the fear-mediated reduction in the AMPA/NMDA ratio at these synapses and, in particular, whether specific changes in the synaptic density of AMPA receptors underlie the observed change. To this aim, we used a detergent-digested freeze-fracture replica immunolabeling technique (FRIL) approach that enables to visualize the spatial distribution of intrasynaptic AMPA receptors at high resolution. AMPA receptors were detected using an antibody raised against an epitope common to all AMPA subunits. To visualize thalamic inputs, we virally transduced the posterior thalamic complex with Channelrhodopsin 2-YFP, which is anterogradely transported along axons. Using face-matched replica, we confirmed that the postsynaptic elements were ITC neurons due to their prominent expression of μ-opioid receptors. With this approach, we show that, following auditory fear conditioning in mice, the formation and retrieval of fear memory is linked to a significant reduction in the density of AMPA receptors, particularly at spine synapses formed by inputs of the posterior intralaminar thalamic and medial geniculate nuclei onto identified ITC neurons. Our study is one of the few that has directly linked the regulation of AMPA receptor trafficking to memory processes in identified neuronal networks, by showing that fear-memory induced reduction in AMPA/NMDA ratio at thalamic-ITC synapses is associated with a reduced postsynaptic AMPA receptor density.
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Affiliation(s)
- Anna Seewald
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck, Austria
| | - Sabine Schönherr
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck, Austria
| | - Heide Hörtnagl
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck, Austria
| | - Ingrid Ehrlich
- Center for Integrative Neuroscience, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,Department of Neurobiology, Institute of Biomaterials and Biomolecular Systems, University of Stuttgart, Stuttgart, Germany
| | | | - Francesco Ferraguti
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck, Austria
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17
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Walia A, Lee C, Hartsock J, Goodman SS, Dolle R, Salt AN, Lichtenhan JT, Rutherford MA. Reducing Auditory Nerve Excitability by Acute Antagonism of Ca 2+-Permeable AMPA Receptors. Front Synaptic Neurosci 2021; 13:680621. [PMID: 34290596 PMCID: PMC8287724 DOI: 10.3389/fnsyn.2021.680621] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/31/2021] [Indexed: 11/13/2022] Open
Abstract
Hearing depends on glutamatergic synaptic transmission mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). AMPARs are tetramers, where inclusion of the GluA2 subunit reduces overall channel conductance and Ca2+ permeability. Cochlear afferent synapses between inner hair cells (IHCs) and auditory nerve fibers (ANFs) contain the AMPAR subunits GluA2, 3, and 4. However, the tetrameric complement of cochlear AMPAR subunits is not known. It was recently shown in mice that chronic intracochlear delivery of IEM-1460, an antagonist selective for GluA2-lacking AMPARs [also known as Ca2+-permeable AMPARs (CP-AMPARs)], before, during, and after acoustic overexposure prevented both the trauma to ANF synapses and the ensuing reduction of cochlear nerve activity in response to sound. Surprisingly, baseline measurements of cochlear function before exposure were unaffected by chronic intracochlear delivery of IEM-1460. This suggested that cochlear afferent synapses contain GluA2-lacking CP-AMPARs alongside GluA2-containing Ca2+-impermeable AMPA receptors (CI-AMPARs), and that the former can be antagonized for protection while the latter remain conductive. Here, we investigated hearing function in the guinea pig during acute local or systemic delivery of CP-AMPAR antagonists. Acute intracochlear delivery of IEM-1460 or systemic delivery of IEM-1460 or IEM-1925 reduced the amplitude of the ANF compound action potential (CAP) significantly, for all tone levels and frequencies, by > 50% without affecting CAP thresholds or distortion product otoacoustic emissions (DPOAE). Following systemic dosing, IEM-1460 levels in cochlear perilymph were ~ 30% of blood levels, on average, consistent with pharmacokinetic properties predicting permeation of the compounds into the brain and ear. Both compounds were metabolically stable with half-lives >5 h in vitro, and elimination half-lives in vivo of 118 min (IEM-1460) and 68 min (IEM-1925). Heart rate monitoring and off-target binding assays suggest an enhanced safety profile for IEM-1925 over IEM-1460. Compound potency on CAP reduction (IC50 ~ 73 μM IEM-1460) was consistent with a mixture of GluA2-lacking and GluA2-containing AMPARs. These data strongly imply that cochlear afferent synapses of the guinea pig contain GluA2-lacking CP-AMPARs. We propose these CP-AMPARs may be acutely antagonized with systemic dosing, to protect from glutamate excitotoxicity, while transmission at GluA2-containing AMPARs persists to mediate hearing during the protection.
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Affiliation(s)
- Amit Walia
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Choongheon Lee
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Jared Hartsock
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, United States
| | - Roland Dolle
- Department of Biochemistry and Molecular Biophysics, Washington University Center for Drug Discovery, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Alec N Salt
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Jeffery T Lichtenhan
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
| | - Mark A Rutherford
- Department of Otolaryngology, Washington University in St. Louis School of Medicine, St. Louis, MO, United States
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18
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Holderith N, Heredi J, Kis V, Nusser Z. A High-Resolution Method for Quantitative Molecular Analysis of Functionally Characterized Individual Synapses. Cell Rep 2021; 32:107968. [PMID: 32726631 PMCID: PMC7408500 DOI: 10.1016/j.celrep.2020.107968] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 05/15/2020] [Accepted: 07/08/2020] [Indexed: 12/24/2022] Open
Abstract
Elucidating the molecular mechanisms underlying the functional diversity of synapses requires a high-resolution, sensitive, diffusion-free, quantitative localization method that allows the determination of many proteins in functionally characterized individual synapses. Array tomography permits the quantitative analysis of single synapses but has limited sensitivity, and its application to functionally characterized synapses is challenging. Here, we aim to overcome these limitations by searching the parameter space of different fixation, resin, embedding, etching, retrieval, and elution conditions. Our optimizations reveal that etching epoxy-resin-embedded ultrathin sections with Na-ethanolate and treating them with SDS dramatically increase the labeling efficiency of synaptic proteins. We also demonstrate that this method is ideal for the molecular characterization of individual synapses following paired recordings, two-photon [Ca2+] or glutamate-sensor (iGluSnFR) imaging. This method fills a missing gap in the toolbox of molecular and cellular neuroscience, helping us to reveal how molecular heterogeneity leads to diversity in function. Etching and antigen retrieval enhance immunoreactions in epoxy-resin-embedded tissue Biocytin-filled nerve cells can be visualized in epoxy-resin-embedded tissue Molecular composition of functionally characterized individual synapses is revealed Multiplexed, postembedding reactions are compatible with STED imaging
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Affiliation(s)
- Noemi Holderith
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary
| | - Judit Heredi
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary
| | - Viktor Kis
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary
| | - Zoltan Nusser
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary.
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19
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Zhao HB, Zhu Y, Liu LM. Excess extracellular K + causes inner hair cell ribbon synapse degeneration. Commun Biol 2021; 4:24. [PMID: 33398038 PMCID: PMC7782724 DOI: 10.1038/s42003-020-01532-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 11/30/2020] [Indexed: 11/16/2022] Open
Abstract
Inner hair cell (IHC) ribbon synapses are the first synapse in the auditory system and can be degenerated by noise and aging, thereby leading to hidden hearing loss (HHL) and other hearing disorders. However, the mechanism underlying this cochlear synaptopathy remains unclear. Here, we report that elevation of extracellular K+, which is a consequence of noise exposure, could cause IHC ribbon synapse degeneration and swelling. Like intensity dependence in noise-induced cochlear synaptopathy, the K+-induced degeneration was dose-dependent, and could be attenuated by BK channel blockers. However, application of glutamate receptor (GluR) agonists caused ribbon swelling but not degeneration. In addition, consistent with synaptopathy in HHL, both K+ and noise exposure only caused IHC but not outer hair cell ribbon synapse degeneration. These data reveal that K+ excitotoxicity can degenerate IHC ribbon synapses in HHL, and suggest that BK channel may be a potential target for prevention and treatment of HHL.
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Affiliation(s)
- Hong-Bo Zhao
- Dept. of Otolaryngology, University of Kentucky Medical School, 800 Rose Street, Lexington, KY, 40536, USA.
| | - Yan Zhu
- Dept. of Otolaryngology, University of Kentucky Medical School, 800 Rose Street, Lexington, KY, 40536, USA
| | - Li-Man Liu
- Dept. of Otolaryngology, University of Kentucky Medical School, 800 Rose Street, Lexington, KY, 40536, USA
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20
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Synaptic migration and reorganization after noise exposure suggests regeneration in a mature mammalian cochlea. Sci Rep 2020; 10:19945. [PMID: 33203940 PMCID: PMC7672098 DOI: 10.1038/s41598-020-76553-w] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 10/21/2020] [Indexed: 01/27/2023] Open
Abstract
Overexposure to intense noise can destroy the synapses between auditory nerve fibers and their hair cell targets without destroying the hair cells themselves. In adult mice, this synaptopathy is immediate and largely irreversible, whereas, in guinea pigs, counts of immunostained synaptic puncta can recover with increasing post-exposure survival. Here, we asked whether this recovery simply reflects changes in synaptic immunostaining, or whether there is actual retraction and extension of neurites and/or synaptogenesis. Analysis of the numbers, sizes and spatial distribution of pre- and post-synaptic markers on cochlear inner hair cells, in guinea pigs surviving from 1 day to 6 months after a synaptopathic exposure, shows dramatic synaptic re-organization during the recovery period in which synapse counts recover from 16 to 91% of normal in the most affected regions. Synaptic puncta move all over the hair cell membrane during recovery, translocating far from their normal positions at the basolateral pole, and auditory-nerve terminals extend towards the hair cell’s apical end to re-establish contact with them. These observations provide stronger evidence for spontaneous neural regeneration in a mature mammalian cochlea than can be inferred from synaptic counts alone.
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21
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Preventing presbycusis in mice with enhanced medial olivocochlear feedback. Proc Natl Acad Sci U S A 2020; 117:11811-11819. [PMID: 32393641 DOI: 10.1073/pnas.2000760117] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
"Growing old" is the most common cause of hearing loss. Age-related hearing loss (ARHL) (presbycusis) first affects the ability to understand speech in background noise, even when auditory thresholds in quiet are normal. It has been suggested that cochlear denervation ("synaptopathy") is an early contributor to age-related auditory decline. In the present work, we characterized age-related cochlear synaptic degeneration and hair cell loss in mice with enhanced α9α10 cholinergic nicotinic receptors gating kinetics ("gain of function" nAChRs). These mediate inhibitory olivocochlear feedback through the activation of associated calcium-gated potassium channels. Cochlear function was assessed via distortion product otoacoustic emissions and auditory brainstem responses. Cochlear structure was characterized in immunolabeled organ of Corti whole mounts using confocal microscopy to quantify hair cells, auditory neurons, presynaptic ribbons, and postsynaptic glutamate receptors. Aged wild-type mice had elevated acoustic thresholds and synaptic loss. Afferent synapses were lost from inner hair cells throughout the aged cochlea, together with some loss of outer hair cells. In contrast, cochlear structure and function were preserved in aged mice with gain-of-function nAChRs that provide enhanced olivocochlear inhibition, suggesting that efferent feedback is important for long-term maintenance of inner ear function. Our work provides evidence that olivocochlear-mediated resistance to presbycusis-ARHL occurs via the α9α10 nAChR complexes on outer hair cells. Thus, enhancement of the medial olivocochlear system could be a viable strategy to prevent age-related hearing loss.
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22
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Pisciottano F, Cinalli AR, Stopiello JM, Castagna VC, Elgoyhen AB, Rubinstein M, Gómez-Casati ME, Franchini LF. Inner Ear Genes Underwent Positive Selection and Adaptation in the Mammalian Lineage. Mol Biol Evol 2020; 36:1653-1670. [PMID: 31137036 DOI: 10.1093/molbev/msz077] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The mammalian inner ear possesses functional and morphological innovations that contribute to its unique hearing capacities. The genetic bases underlying the evolution of this mammalian landmark are poorly understood. We propose that the emergence of morphological and functional innovations in the mammalian inner ear could have been driven by adaptive molecular evolution. In this work, we performed a meta-analysis of available inner ear gene expression data sets in order to identify genes that show signatures of adaptive evolution in the mammalian lineage. We analyzed ∼1,300 inner ear expressed genes and found that 13% show signatures of positive selection in the mammalian lineage. Several of these genes are known to play an important function in the inner ear. In addition, we identified that a significant proportion of genes showing signatures of adaptive evolution in mammals have not been previously reported to participate in inner ear development and/or physiology. We focused our analysis in two of these genes: STRIP2 and ABLIM2 by generating null mutant mice and analyzed their auditory function. We found that mice lacking Strip2 displayed a decrease in neural response amplitudes. In addition, we observed a reduction in the number of afferent synapses, suggesting a potential cochlear neuropathy. Thus, this study shows the usefulness of pursuing a high-throughput evolutionary approach followed by functional studies to track down genes that are important for inner ear function. Moreover, this approach sheds light on the genetic bases underlying the evolution of the mammalian inner ear.
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Affiliation(s)
- Francisco Pisciottano
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Alejandro R Cinalli
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Juan Matías Stopiello
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Valeria C Castagna
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires,Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires, Buenos Aires,Argentina
| | - María Eugenia Gómez-Casati
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires,Argentina
| | - Lucía F Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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23
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Luo Y, Qu T, Song Q, Qi Y, Yu S, Gong S, Liu K, Jiang X. Repeated Moderate Sound Exposure Causes Accumulated Trauma to Cochlear Ribbon Synapses in Mice. Neuroscience 2020; 429:173-184. [PMID: 31935490 DOI: 10.1016/j.neuroscience.2019.12.049] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 12/23/2019] [Accepted: 12/26/2019] [Indexed: 12/23/2022]
Abstract
Repeated induction of a temporary threshold shift (TTS) may result in a permanent threshold shift (PTS) and is thought to be associated with early onset of age-related hearing loss (ARHL). The possibility that a PTS might be induced by administration of repeated TTS-inducing noise exposures (NEs) over a short period during early adulthood has not been formally investigated. We aimed to investigate possible cumulative acoustic overstimulation effects that permanently shift the auditory threshold. Young adult C57BL/6J mice were exposed twice to moderate white noise in an experimental design that minimized the effects of aging. The first exposure resulted in a reversible noise-induced hearing loss (NIHL) measured as recoverable alterations in auditory brainstem response (ABR) thresholds, waveform amplitudes, and numbers of ribbon synapses. The second NE with the same parameters caused persistent threshold shifts, wave I amplitude reductions, wave IV/I ratio enhancements, and synaptic losses, even though recovery time sufficient for a TTS had been provided. The pattern of PTS resembled NIHL since the observed impairments tonotopically followed the power spectrum of the noise insult, rather than ARHL, which distributes at higher frequencies. No significant changes were observed in the control group as the mice aged. To conclude, our results demonstrate a cumulative effect of repetitive TTS-inducing NE on hearing function and synaptic plasticity that does not cause premature ARHL, thereby providing insight into the pathophysiological mechanisms underlying NIHL and ARHL.
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Affiliation(s)
- Yangtuo Luo
- Department of Otolaryngology, The First Affiliated Hospital of China Medical University, Shenyang 110001, China
| | - Tengfei Qu
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Qingling Song
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Yue Qi
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Shukui Yu
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Shusheng Gong
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Ke Liu
- Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China.
| | - Xuejun Jiang
- Department of Otolaryngology, The First Affiliated Hospital of China Medical University, Shenyang 110001, China.
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24
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Moser T, Grabner CP, Schmitz F. Sensory Processing at Ribbon Synapses in the Retina and the Cochlea. Physiol Rev 2020; 100:103-144. [DOI: 10.1152/physrev.00026.2018] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In recent years, sensory neuroscientists have made major efforts to dissect the structure and function of ribbon synapses which process sensory information in the eye and ear. This review aims to summarize our current understanding of two key aspects of ribbon synapses: 1) their mechanisms of exocytosis and endocytosis and 2) their molecular anatomy and physiology. Our comparison of ribbon synapses in the cochlea and the retina reveals convergent signaling mechanisms, as well as divergent strategies in different sensory systems.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Chad P. Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Frank Schmitz
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
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25
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Frye MD, Ryan AF, Kurabi A. Inflammation associated with noise-induced hearing loss. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:4020. [PMID: 31795714 PMCID: PMC7480080 DOI: 10.1121/1.5132545] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 06/17/2019] [Accepted: 06/20/2019] [Indexed: 05/22/2023]
Abstract
Inflammation is a complex biological response to harmful stimuli including infection, tissue damage, and toxins. Thus, it is not surprising that cochlear damage by noise includes an inflammatory component. One mechanism by which inflammation is generated by tissue damage is the activation of damage-associated molecular patterns (DAMPs). Many of the cellular receptors for DAMPS, including Toll-like receptors, NOD-like receptors, and DNA receptors, are also receptors for pathogens, and function in the innate immune system. DAMP receptors are known to be expressed by cochlear cells, and binding of molecules released by damaged cells to these receptors result in the activation of cell stress pathways. This leads to the generation of pro-inflammatory cytokines and chemokines that recruit pro-inflammatory leukocytes. Extensive evidence indicates pro-inflammatory cytokines including TNF alpha and interleukin 1 beta, and chemokines including CCL2, are induced in the cochlea after noise exposure. The recruitment of macrophages into the cochlea has also been demonstrated. These provide substrates for noise damage to be enhanced by inflammation. Evidence is provided by the effectiveness of anti-inflammatory drugs in ameliorating noise-induced hearing loss. Involvement of inflammation provides a wide variety of additional anti-inflammatory and pro-resolution agents as potential pharmacological interventions in noise-induced hearing loss.
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Affiliation(s)
- Mitchell D Frye
- Callier Center for Communication Disorders, School of Behavioral and Brain Sciences, The University of Texas at Dallas, Dallas, Texas 75080, USA
| | - Allen F Ryan
- Department of Surgery/Otolaryngology, University of California San Diego, School of Medicine, and Veterans Administration Medical Center, La Jolla, California 92093, USA
| | - Arwa Kurabi
- Department of Surgery/Otolaryngology, University of California San Diego, School of Medicine, and Veterans Administration Medical Center, La Jolla, California 92093, USA
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26
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Byczkowicz N, Eshra A, Montanaro J, Trevisiol A, Hirrlinger J, Kole MHP, Shigemoto R, Hallermann S. HCN channel-mediated neuromodulation can control action potential velocity and fidelity in central axons. eLife 2019; 8:e42766. [PMID: 31496517 PMCID: PMC6733576 DOI: 10.7554/elife.42766] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 08/13/2019] [Indexed: 12/31/2022] Open
Abstract
Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels control electrical rhythmicity and excitability in the heart and brain, but the function of HCN channels at the subcellular level in axons remains poorly understood. Here, we show that the action potential conduction velocity in both myelinated and unmyelinated central axons can be bidirectionally modulated by a HCN channel blocker, cyclic adenosine monophosphate (cAMP), and neuromodulators. Recordings from mouse cerebellar mossy fiber boutons show that HCN channels ensure reliable high-frequency firing and are strongly modulated by cAMP (EC50 40 µM; estimated endogenous cAMP concentration 13 µM). In addition, immunogold-electron microscopy revealed HCN2 as the dominating subunit in cerebellar mossy fibers. Computational modeling indicated that HCN2 channels control conduction velocity primarily by altering the resting membrane potential and are associated with significant metabolic costs. These results suggest that the cAMP-HCN pathway provides neuromodulators with an opportunity to finely tune energy consumption and temporal delays across axons in the brain.
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Affiliation(s)
- Niklas Byczkowicz
- Carl-Ludwig-Institute for Physiology, Medical FacultyUniversity LeipzigLeipzigGermany
| | - Abdelmoneim Eshra
- Carl-Ludwig-Institute for Physiology, Medical FacultyUniversity LeipzigLeipzigGermany
| | | | - Andrea Trevisiol
- Department of NeurogeneticsMax-Planck-Institute for Experimental MedicineGöttingenGermany
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Medical FacultyUniversity LeipzigLeipzigGermany
- Department of NeurogeneticsMax-Planck-Institute for Experimental MedicineGöttingenGermany
| | - Maarten HP Kole
- Department of Axonal Signaling, Netherlands Institute for NeuroscienceRoyal Netherlands Academy of Arts and SciencesAmsterdamNetherlands
- Cell Biology, Faculty of ScienceUniversity of UtrechtPadualaanNetherlands
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria (IST Austria)KlosterneuburgAustria
| | - Stefan Hallermann
- Carl-Ludwig-Institute for Physiology, Medical FacultyUniversity LeipzigLeipzigGermany
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27
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Parato J, Shen H, Smith SS. α4βδ GABA A Receptors Trigger Synaptic Pruning and Reduce Dendritic Length of Female Mouse CA3 Hippocampal Pyramidal Cells at Puberty. Neuroscience 2019; 398:23-36. [PMID: 30496825 PMCID: PMC6411036 DOI: 10.1016/j.neuroscience.2018.11.032] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Revised: 11/01/2018] [Accepted: 11/20/2018] [Indexed: 01/24/2023]
Abstract
Synaptic pruning during adolescence is critical for optimal cognition. The CA3 hippocampus contains unique spine types and plays a pivotal role in pattern separation and seizure generation, where sex differences exist, but adolescent pruning has only been studied in the male. Thus, for the present study we assessed pruning of specific spine types in the CA3 hippocampus during adolescence and investigated a possible mechanism in the female mouse. To this end, we used Golgi-impregnated brains from pubertal (∼PND 35, assessed by vaginal opening) and post-pubertal (PND 56) mice. Spine density was assessed from z-stack (0.1-μm steps) images taken using a Nikon DS-U3 camera through a Nikon Eclipse Ci-L microscope and analyzed with NIS Elements. Spine density decreased significantly (P < 0.05) during adolescence, with 50-60% decreases in mushroom and stubby spine-types (P < 0.05, ∼PND35 vs. PND56) in non-proestrous mice. This was associated with decreases in kalirin-7, a spine protein which stabilizes the cytoskeleton and is required for spine maintenance. Because our previous findings suggest that pubertal increases in α4βδ GABAA receptors (GABARs) trigger pruning in CA1, we investigated their role in CA3. α4 expression in CA3 hippocampus increased 4-fold at puberty (P < 0.05), assessed by immunostaining and verified electrophysiologically by an increased response to gaboxadol (100 nM), which is selective for α4βδ. Knock-out of α4 prevented the pubertal decrease in kalirin-7 and synaptic pruning and also increased the dendritic length, demonstrating a functional link. These data suggest that pubertal α4βδ GABARs alter dendritic morphology and trigger pruning in female CA3 hippocampus.
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Affiliation(s)
- Julie Parato
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY 11203, USA; Program in Neural and Behavioral Science, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY 11203, USA
| | - Hui Shen
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY 11203, USA; School of Biomedical Engineering, Tianjin Medical University, No. 22 Qixiangtai Road, Heping District, Tianjin 300070, China
| | - Sheryl S Smith
- Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY 11203, USA; The Robert F. Furchgott Center for Neural and Behavioral Science, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
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28
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Bullen A, Anderson L, Bakay W, Forge A. Localized disorganization of the cochlear inner hair cell synaptic region after noise exposure. Biol Open 2019; 8:bio.038547. [PMID: 30504133 PMCID: PMC6361218 DOI: 10.1242/bio.038547] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The prevalence and importance of hearing damage caused by noise levels not previously thought to cause permanent hearing impairment has become apparent in recent years. The damage to, and loss of, afferent terminals of auditory nerve fibres at the cochlear inner hair cell has been well established, but the effects of noise exposure and terminal loss on the inner hair cell are less known. Using three-dimensional structural studies in mice we have examined the consequences of afferent terminal damage on inner hair cell morphology and intracellular structure. We identified a structural phenotype in the pre-synaptic regions of these damaged hair cells that persists for four weeks after noise exposure, and demonstrates a specific dysregulation of the synaptic vesicle recycling pathway. We show evidence of a failure in regeneration of vesicles from small membrane cisterns in damaged terminals, resulting from a failure of separation of small vesicle buds from the larger cisternal membranes.
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29
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Wang J, Yin S, Chen H, Shi L. Noise-Induced Cochlear Synaptopathy and Ribbon Synapse Regeneration: Repair Process and Therapeutic Target. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1130:37-57. [PMID: 30915700 DOI: 10.1007/978-981-13-6123-4_3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The synapse between the inner hair cells (IHCs) and the spiral ganglion neurons (SGNs) in mammalian cochleae is characterized as having presynaptic ribbons and therefore is called ribbon synapse. The special molecular organization is reviewed in this chapter in association with the functional feature of this synapse in signal processing. This is followed by the review on noise-induced damage to this synapse with a focus on recent reports in animal models in which the effect of brief noise exposures is observed without causing significant permanent threshold shift (PTS). In this regard, the potential mechanism of the synaptic damage by noise and the impact of this damage on hearing are summarized to clarify the concept of noise-induced hidden hearing loss, which is defined as the functional deficits in hearing without threshold elevation. A controversial issue is addressed in this review as whether the disrupted synapses can be regenerated. Moreover, the review summarizes the work of therapeutic research to protect the synapses or to promote the regeneration of the synapse after initial disruption. Lastly, several unresolved issues are raised for investigation in the future.
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Affiliation(s)
- Jian Wang
- School of Communication Science and Disorders, Dalhousie University, Halifax, NS, Canada.
| | - Shankai Yin
- Otolaryngology Research Institute, 6th Affiliated Hospital, Shanghai Jiao-Tong University, Shanghai, China
| | - Hengchao Chen
- Otolaryngology Research Institute, 6th Affiliated Hospital, Shanghai Jiao-Tong University, Shanghai, China
| | - Lijuan Shi
- Department of Physiology, Medical College of Southeast University, Nanjing, China
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30
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Patriarchi T, Buonarati OR, Hell JW. Postsynaptic localization and regulation of AMPA receptors and Cav1.2 by β2 adrenergic receptor/PKA and Ca 2+/CaMKII signaling. EMBO J 2018; 37:e99771. [PMID: 30249603 PMCID: PMC6187224 DOI: 10.15252/embj.201899771] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 07/25/2018] [Accepted: 08/17/2018] [Indexed: 11/09/2022] Open
Abstract
The synapse transmits, processes, and stores data within its tiny space. Effective and specific signaling requires precise alignment of the relevant components. This review examines current insights into mechanisms of AMPAR and NMDAR localization by PSD-95 and their spatial distribution at postsynaptic sites to illuminate the structural and functional framework of postsynaptic signaling. It subsequently delineates how β2 adrenergic receptor (β2 AR) signaling via adenylyl cyclase and the cAMP-dependent protein kinase PKA is organized within nanodomains. Here, we discuss targeting of β2 AR, adenylyl cyclase, and PKA to defined signaling complexes at postsynaptic sites, i.e., AMPARs and the L-type Ca2+ channel Cav1.2, and other subcellular surface localizations, the role of A kinase anchor proteins, the physiological relevance of the spatial restriction of corresponding signaling, and their interplay with signal transduction by the Ca2+- and calmodulin-dependent kinase CaMKII How localized and specific signaling by cAMP occurs is a central cellular question. The dendritic spine constitutes an ideal paradigm for elucidating the dimensions of spatially restricted signaling because of their small size and defined protein composition.
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MESH Headings
- Animals
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Calcium Signaling/physiology
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/genetics
- Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism
- Cyclic AMP-Dependent Protein Kinases/genetics
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Humans
- Receptors, AMPA/genetics
- Receptors, AMPA/metabolism
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Receptors, N-Methyl-D-Aspartate/genetics
- Receptors, N-Methyl-D-Aspartate/metabolism
- Synapses/genetics
- Synapses/metabolism
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Affiliation(s)
- Tommaso Patriarchi
- Department of Pharmacology, University of California, Davis, CA, USA
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA, USA
| | | | - Johannes W Hell
- Department of Pharmacology, University of California, Davis, CA, USA
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31
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Chen J, Hong F, Zhang C, Li L, Wang C, Shi H, Fu Y, Wang J. Differentiation and transplantation of human induced pluripotent stem cell-derived otic epithelial progenitors in mouse cochlea. Stem Cell Res Ther 2018; 9:230. [PMID: 30157937 PMCID: PMC6116394 DOI: 10.1186/s13287-018-0967-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 07/12/2018] [Accepted: 08/01/2018] [Indexed: 12/24/2022] Open
Abstract
Background Inner ear hair cells as mechanoreceptors are extremely important for hearing. Defects in hair cells are a major cause of deafness. Induced pluripotent stem cells (iPSCs) are promising for regenerating inner ear hair cells and treating hearing loss. Here, we investigated migration, differentiation, and synaptic connections of transplanted otic epithelial progenitors (OEPs) derived from human iPSCs in mouse cochlea. Methods Human urinary cells isolated from a healthy donor were reprogramed to form iPSCs that were induced to differentiate into OEPs and hair cell-like cells. Immunocytochemistry, electrophysiological examination, and scanning electron microscopy were used to examine characteristics of induced hair cell-like cells. OEP-derived hair cell-like cells were cocultured with spiral ganglion neurons (SGNs), and the markers of synaptic connections were detected using immunocytochemistry and transmission electron microscope. In vivo, OEPs derived from iPSCs were transplanted into the cochlea of mice by injection through the round window. Migration, differentiation, and synaptic connections of transplanted cells were also examined by thin cochlear sectioning and immunohistochemistry. Results The induced hair cell-like cells displayed typical morphological characteristics and electrophysiological properties specific to inner hair cells. In vitro, OEP-derived hair cell-like cells formed synaptic connections with SGNs in coculture. In vivo, some of the transplanted cells migrated to the site of the resident hair cells in the organ of Corti, differentiated into hair cell-like cells, and formed synaptic connections with native SGNs. Conclusions We conclude that the transplantation of OEPs is feasible for the regeneration of hair cells. These results present a substantial reference for a cell-based therapy for the loss of hair cells.
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Affiliation(s)
- Jianling Chen
- Institute of Cell and Development, College of Life Sciences, Zi-Jin-Gang Campus of Zhejiang University, Room 307, No.866, Yuhangtang Road, Hangzhou, 310058, Zhejiang, China
| | - Fanfan Hong
- Institute of Cell and Development, College of Life Sciences, Zi-Jin-Gang Campus of Zhejiang University, Room 307, No.866, Yuhangtang Road, Hangzhou, 310058, Zhejiang, China
| | - Cui Zhang
- Institute of Cell and Development, College of Life Sciences, Zi-Jin-Gang Campus of Zhejiang University, Room 307, No.866, Yuhangtang Road, Hangzhou, 310058, Zhejiang, China
| | - Liang Li
- Institute of Cell and Development, College of Life Sciences, Zi-Jin-Gang Campus of Zhejiang University, Room 307, No.866, Yuhangtang Road, Hangzhou, 310058, Zhejiang, China
| | - Cuicui Wang
- Institute of Cell and Development, College of Life Sciences, Zi-Jin-Gang Campus of Zhejiang University, Room 307, No.866, Yuhangtang Road, Hangzhou, 310058, Zhejiang, China
| | - Haosong Shi
- Department of Otorhinolaryngology, the Sixth People's Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, China
| | - Yong Fu
- Department of ENT, Head and Neck Surgery, the Children's Hospital, Zhejiang University School of Medicine, Zhejiang, China. .,Department of Otolaryngology, the Children Hospital, School of Medicine, Bin-Jiang Campus of Zhejiang University, No. 3333, Binsheng Road, Hangzhou, 310051, Zhejiang, China.
| | - Jinfu Wang
- Institute of Cell and Development, College of Life Sciences, Zi-Jin-Gang Campus of Zhejiang University, Room 307, No.866, Yuhangtang Road, Hangzhou, 310058, Zhejiang, China.
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32
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Pre- and postsynaptic ionotropic glutamate receptors in the auditory system of mammals. Hear Res 2018; 362:1-13. [DOI: 10.1016/j.heares.2018.02.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 02/16/2018] [Accepted: 02/21/2018] [Indexed: 01/22/2023]
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Bae JY, Lee JS, Ko SJ, Cho YS, Rah JC, Cho HJ, Park MJ, Bae YC. Extrasynaptic homomeric glycine receptors in neurons of the rat trigeminal mesencephalic nucleus. Brain Struct Funct 2018; 223:2259-2268. [PMID: 29460053 DOI: 10.1007/s00429-018-1607-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 11/29/2017] [Indexed: 12/19/2022]
Abstract
The neurons in the trigeminal mesencephalic nucleus (Vmes) innervate jaw-closing muscle spindles and periodontal ligaments, and play a crucial role in the regulation of jaw movements. Recently, it was shown that many boutons that form synapses on them are immunopositive for glycine (Gly+), suggesting that these neurons receive glycinergic input. Information about the glycine receptors that mediate this input is needed to help understand the role of glycine in controlling Vmes neuron excitability. For this, we investigated the expression of glycine receptor subunit alpha 3 (GlyRα3) and gephyrin in neurons in Vmes and the trigeminal motor nucleus (Vmo), and the Gly+ boutons that contact them by light- and electron-microscopic immunocytochemistry and quantitative ultrastructural analysis. The somata of the Vmes neurons were immunostained for GlyRα3, but not gephyrin, indicating expression of homomeric GlyR. The immunostaining for GlyRα3 was localized away from the synapses in the Vmes neuron somata, in contrast to the Vmo neurons, where the staining for GlyRα3 and gephyrin were localized at the subsynaptic zones in somata and dendrites. Additionally, the ultrastructural determinants of synaptic strength, bouton volume, mitochondrial volume, and active zone area, were significantly smaller in Gly+ boutons on the Vmes neurons than in those on the Vmo neurons. These findings support the notion that the Vmes neurons receive glycinergic input via putative extrasynaptic homomeric glycine receptors, likely mediating a slow, tonic modulation of the Vmes neuron excitability.
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Affiliation(s)
- Jin Young Bae
- Department of Anatomy and Neurobiology, School of Medicine and Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Jae Sik Lee
- Department of Anatomy and Neurobiology, School of Medicine and Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Sang Jin Ko
- Department of Anatomy and Neurobiology, School of Medicine and Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Yi Sul Cho
- Department of Anatomy and Neurobiology, School of Medicine and Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Jong-Cheol Rah
- Korea Brian Research Institute, 61 Cheomdan-ro, Dong-gu, Daegu, 701-300, South Korea
| | - Hee Jung Cho
- Department of Anatomy and Neurobiology, School of Medicine and Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Mae Ja Park
- Department of Anatomy and Neurobiology, School of Medicine and Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Medicine and Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea.
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Cai R, Montgomery SC, Graves KA, Caspary DM, Cox BC. The FBN rat model of aging: investigation of ABR waveforms and ribbon synapse changes. Neurobiol Aging 2018; 62:53-63. [PMID: 29107847 PMCID: PMC5743589 DOI: 10.1016/j.neurobiolaging.2017.09.034] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 09/22/2017] [Accepted: 09/30/2017] [Indexed: 01/25/2023]
Abstract
Age-related hearing loss is experienced by one-third of individuals aged 65 years and older and can be socially debilitating. Historically, there has been poor correlation between age-related threshold changes, loss of speech understanding, and loss of cochlear hair cells. We examined changes in ribbon synapse number at four different ages in Fisher Brown Norway rats, an extensively studied rat model of aging. In contrast to previous work in mice/Wistar rats, we found minimal ribbon synapse loss before 20 months, with significant differences in 24- and 28-month-old rats at 4 kHz. Significant outer HC loss was observed at 24 and 28 months in low- to mid-frequency regions. Age-related reductions in auditory brainstem response wave I amplitude and increases in threshold were strongly correlated with ribbon synapse loss. Wave V/I ratios increased across age for click, 2, 4, and 24 kHz. Together, we find that ribbon synapses in the Fisher Brown Norway rat cochlea show resistance to aging until ∼60% of their life span, suggesting species/strain differences may underpin decreased peripheral input into the aging central processor.
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Affiliation(s)
- Rui Cai
- Division of Otolaryngology, Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA
| | - Scott C Montgomery
- Division of Otolaryngology, Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA; Division of Otolaryngology, Department of Surgery, Southern Illinois University School of Medicine, Springfield, IL, USA
| | - Kaley A Graves
- Division of Otolaryngology, Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA
| | - Donald M Caspary
- Division of Otolaryngology, Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA; Division of Otolaryngology, Department of Surgery, Southern Illinois University School of Medicine, Springfield, IL, USA.
| | - Brandon C Cox
- Division of Otolaryngology, Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA; Division of Otolaryngology, Department of Surgery, Southern Illinois University School of Medicine, Springfield, IL, USA.
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35
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Szoboszlay M, Kirizs T, Nusser Z. Objective quantification of nanoscale protein distributions. Sci Rep 2017; 7:15240. [PMID: 29127366 PMCID: PMC5681686 DOI: 10.1038/s41598-017-15695-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 11/01/2017] [Indexed: 01/13/2023] Open
Abstract
Nanoscale distribution of molecules within small subcellular compartments of neurons critically influences their functional roles. Although, numerous ways of analyzing the spatial arrangement of proteins have been described, a thorough comparison of their effectiveness is missing. Here we present an open source software, GoldExt, with a plethora of measures for quantification of the nanoscale distribution of proteins in subcellular compartments (e.g. synapses) of nerve cells. First, we compared the ability of five different measures to distinguish artificial uniform and clustered patterns from random point patterns. Then, the performance of a set of clustering algorithms was evaluated on simulated datasets with predefined number of clusters. Finally, we applied the best performing methods to experimental data, and analyzed the nanoscale distribution of different pre- and postsynaptic proteins, revealing random, uniform and clustered sub-synaptic distribution patterns. Our results reveal that application of a single measure is sufficient to distinguish between different distributions.
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Affiliation(s)
- Miklos Szoboszlay
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Tekla Kirizs
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.,János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Zoltan Nusser
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.
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36
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The number and distribution of AMPA receptor channels containing fast kinetic GluA3 and GluA4 subunits at auditory nerve synapses depend on the target cells. Brain Struct Funct 2017; 222:3375-3393. [PMID: 28397107 PMCID: PMC5676837 DOI: 10.1007/s00429-017-1408-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 03/20/2017] [Indexed: 02/07/2023]
Abstract
The neurotransmitter receptor subtype, number, density, and distribution relative to the location of transmitter release sites are key determinants of signal transmission. AMPA-type ionotropic glutamate receptors (AMPARs) containing GluA3 and GluA4 subunits are prominently expressed in subsets of neurons capable of firing action potentials at high frequencies, such as auditory relay neurons. The auditory nerve (AN) forms glutamatergic synapses on two types of relay neurons, bushy cells (BCs) and fusiform cells (FCs) of the cochlear nucleus. AN-BC and AN-FC synapses have distinct kinetics; thus, we investigated whether the number, density, and localization of GluA3 and GluA4 subunits in these synapses are differentially organized using quantitative freeze-fracture replica immunogold labeling. We identify a positive correlation between the number of AMPARs and the size of AN-BC and AN-FC synapses. Both types of AN synapses have similar numbers of AMPARs; however, the AN-BC have a higher density of AMPARs than AN-FC synapses, because the AN-BC synapses are smaller. A higher number and density of GluA3 subunits are observed at AN-BC synapses, whereas a higher number and density of GluA4 subunits are observed at AN-FC synapses. The intrasynaptic distribution of immunogold labeling revealed that AMPAR subunits, particularly GluA3, are concentrated at the center of the AN-BC synapses. The central distribution of AMPARs is absent in GluA3-knockout mice, and gold particles are evenly distributed along the postsynaptic density. GluA4 gold labeling was homogenously distributed along both synapse types. Thus, GluA3 and GluA4 subunits are distributed at AN synapses in a target-cell-dependent manner.
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37
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Cservenák M, Kis V, Keller D, Dimén D, Menyhárt L, Oláh S, Szabó ÉR, Barna J, Renner É, Usdin TB, Dobolyi A. Maternally involved galanin neurons in the preoptic area of the rat. Brain Struct Funct 2017; 222:781-798. [PMID: 27300187 PMCID: PMC5156581 DOI: 10.1007/s00429-016-1246-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 05/30/2016] [Indexed: 10/21/2022]
Abstract
Recent selective stimulation and ablation of galanin neurons in the preoptic area of the hypothalamus established their critical role in control of maternal behaviors. Here, we identified a group of galanin neurons in the anterior commissural nucleus (ACN), and a distinct group in the medial preoptic area (MPA). Galanin neurons in ACN but not the MPA co-expressed oxytocin. We used immunodetection of phosphorylated STAT5 (pSTAT5), involved in prolactin receptor signal transduction, to evaluate the effects of suckling-induced prolactin release and found that 76 % of galanin cells in ACN, but only 12 % in MPA were prolactin responsive. Nerve terminals containing tuberoinfundibular peptide 39 (TIP39), a neuropeptide that mediates effects of suckling on maternal motivation, were abundant around galanin neurons in both preoptic regions. In the ACN and MPA, 89 and 82 % of galanin neurons received close somatic appositions, with an average of 2.9 and 2.6 per cell, respectively. We observed perisomatic innervation of galanin neurons using correlated light and electron microscopy. The connection was excitatory based on the glutamate content of TIP39 terminals demonstrated by post-embedding immunogold electron microscopy. Injection of the anterograde tracer biotinylated dextran amine into the TIP39-expressing posterior intralaminar complex of the thalamus (PIL) demonstrated that preoptic TIP39 fibers originate in the PIL, which is activated by suckling. Thus, galanin neurons in the preoptic area of mother rats are innervated by an excitatory neuronal pathway that conveys suckling-related information. In turn, they can be topographically and neurochemically divided into two distinct cell groups, of which only one is affected by prolactin.
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Affiliation(s)
- Melinda Cservenák
- MTA-ELTE NAP B Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary
- Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, 1094, Budapest, Hungary
| | - Viktor Kis
- MTA-ELTE NAP B Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary
- Department of Anatomy, Cell and Developmental Biology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | - Dávid Keller
- MTA-ELTE NAP B Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary
- Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, 1094, Budapest, Hungary
| | - Diána Dimén
- MTA-ELTE NAP B Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary
- Department of Anatomy, Cell and Developmental Biology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | - Lilla Menyhárt
- Department of Anatomy, Cell and Developmental Biology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | - Szilvia Oláh
- MTA-ELTE NAP B Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary
| | - Éva R Szabó
- MTA-ELTE NAP B Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary
- Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, 1094, Budapest, Hungary
| | - János Barna
- Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, 1094, Budapest, Hungary
| | - Éva Renner
- Human Brain Tissue Bank, Semmelweis University, Budapest, Hungary
- MTA-SE NAP Human Brain Tissue Bank Microdissection Laboratory, Semmelweis University, Budapest, Hungary
| | - Ted B Usdin
- Section on Fundamental Neuroscience, National Institute of Mental Health, Bethesda, USA
| | - Arpád Dobolyi
- MTA-ELTE NAP B Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences and Eötvös Loránd University, Budapest, Hungary.
- Laboratory of Neuromorphology, Department of Anatomy, Histology and Embryology, Semmelweis University, 1094, Budapest, Hungary.
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38
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Excessive activation of ionotropic glutamate receptors induces apoptotic hair-cell death independent of afferent and efferent innervation. Sci Rep 2017; 7:41102. [PMID: 28112265 PMCID: PMC5255535 DOI: 10.1038/srep41102] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 12/15/2016] [Indexed: 02/07/2023] Open
Abstract
Accumulation of excess glutamate plays a central role in eliciting the pathological events that follow intensely loud noise exposures and ischemia-reperfusion injury. Glutamate excitotoxicity has been characterized in cochlear nerve terminals, but much less is known about whether excess glutamate signaling also contributes to pathological changes in sensory hair cells. I therefore examined whether glutamate excitotoxicity damages hair cells in zebrafish larvae exposed to drugs that mimic excitotoxic trauma. Exposure to ionotropic glutamate receptor (iGluR) agonists, kainic acid (KA) or N-methyl-D-aspartate (NMDA), contributed to significant, progressive hair cell loss in zebrafish lateral-line organs. To examine whether hair-cell loss was a secondary effect of excitotoxic damage to innervating neurons, I exposed neurog1a morphants-fish whose hair-cell organs are devoid of afferent and efferent innervation-to KA or NMDA. Significant, dose-dependent hair-cell loss occurred in neurog1a morphants exposed to either agonist, and the loss was comparable to wild-type siblings. A survey of iGluR gene expression revealed AMPA-, Kainate-, and NMDA-type subunits are expressed in zebrafish hair cells. Finally, hair cells exposed to KA or NMDA appear to undergo apoptotic cell death. Cumulatively, these data reveal that excess glutamate signaling through iGluRs induces hair-cell death independent of damage to postsynaptic terminals.
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39
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Photobiomodulation by laser therapy rescued auditory neuropathy induced by ouabain. Neurosci Lett 2016; 633:165-173. [DOI: 10.1016/j.neulet.2016.09.039] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/14/2016] [Accepted: 09/22/2016] [Indexed: 12/18/2022]
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40
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Kerti-Szigeti K, Nusser Z. Similar GABAA receptor subunit composition in somatic and axon initial segment synapses of hippocampal pyramidal cells. eLife 2016; 5. [PMID: 27537197 PMCID: PMC4990423 DOI: 10.7554/elife.18426] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 08/08/2016] [Indexed: 11/24/2022] Open
Abstract
Hippocampal pyramidal cells (PCs) express many GABAAR subunit types and receive GABAergic inputs from distinct interneurons. Previous experiments revealed input-specific differences in α1 and α2 subunit densities in perisomatic synapses, suggesting distinct IPSC decay kinetics. However, IPSC decays evoked by axo-axonic, parvalbumin- or cholecystokinin-expressing basket cells were found to be similar. Using replica immunogold labeling, here we show that all CA1 PC somatic and AIS synapses contain the α1, α2, β1, β2, β3 and γ2 subunits. In CA3 PCs, 90% of the perisomatic synapses are immunopositive for the α1 subunit and all synapses are positive for the remaining five subunits. Somatic synapses form unimodal distributions based on their immunoreactivity for these subunits. The α2 subunit densities in somatic synapses facing Cav2.1 (i.e. parvalbumin) or Cav2.2 (cholecystokinin) positive presynaptic active zones are comparable. We conclude that perisomatic synapses made by three distinct interneuron types have similar GABAA receptor subunit content. DOI:http://dx.doi.org/10.7554/eLife.18426.001
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Affiliation(s)
- Katalin Kerti-Szigeti
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zoltan Nusser
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
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41
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Kwan KY. Single-Cell Transcriptome Analysis of Developing and Regenerating Spiral Ganglion Neurons. ACTA ACUST UNITED AC 2016; 2:211-220. [PMID: 28758056 DOI: 10.1007/s40495-016-0064-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The spiral ganglion neurons (SGNs) of the cochlea are essential for our ability to hear. SGN loss after exposure to ototoxic drugs or loud noise results in hearing loss. Pluripotent stem cell-derived and endogenous progenitor cell types have the potential to become SGNs and are cellular foundations for replacement therapies. Repurposing transcriptional regulatory networks to promote SGN differentiation from progenitor cells is a strategy for regeneration. Advances in the Fludigm C1 workflow or Drop-seq allow sequencing of single cell transcriptomes to reveal variability between cells. During differentiation, the individual transcriptomes obtained from single-cell RNA-seq can be exploited to identify different cellular states. Pseudotemporal ordering of transcriptomes describes the differentiation trajectory, allows monitoring of transcriptional changes and determines molecular barriers that prevent the progression of progenitors into SGNs. Analysis of single cell transcriptomes will help develop novel strategies for guiding efficient SGN regeneration.
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Affiliation(s)
- Kelvin Y Kwan
- Department of Cell Biology & Neuroscience, Rutgers University, Piscataway, NJ 08854, USA.,Stem Cell Research Center and Keck Center for Collaborative Neuroscience, Rutgers University, Piscataway, NJ 08854, USA
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42
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Danbolt NC, Zhou Y, Furness DN, Holmseth S. Strategies for immunohistochemical protein localization using antibodies: What did we learn from neurotransmitter transporters in glial cells and neurons. Glia 2016; 64:2045-2064. [PMID: 27458697 DOI: 10.1002/glia.23027] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 06/19/2016] [Accepted: 06/21/2016] [Indexed: 12/11/2022]
Abstract
Immunocytochemistry and Western blotting are still major methods for protein localization, but they rely on the specificity of the antibodies. Validation of antibody specificity remains challenging mostly because ideal negative controls are often unavailable. Further, immunochemical labeling patterns are also influenced by a number of other factors such as postmortem changes, fixation procedures and blocking agents as well as the general assay conditions (e.g., buffers, temperature, etc.). Western blotting similarly depends on tissue collection and sample preparation as well as the electrophoretic separation, transfer to blotting membranes and the immunochemical probing of immobilized molecules. Publication of inaccurate information on protein distribution has downstream consequences for other researchers because the interpretation of physiological and pharmacological observations depends on information on where ion channels, receptors, enzymes or transporters are located. Despite numerous reports, some of which are strongly worded, erroneous localization data are being published. Here we describe the extent of the problem and illustrate the nature of the pitfalls with examples from studies of neurotransmitter transporters. We explain the importance of supplementing immunochemical observations with other measurements (e.g., mRNA levels and distribution, protein activity, mass spectrometry, electrophysiological recordings, etc.) and why quantitative considerations are integral parts of the quality control. Further, we propose a practical strategy for researchers who plan to embark on a localization study. We also share our thoughts about guidelines for quality control. GLIA 2016;64:2045-2064.
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Affiliation(s)
- Niels Christian Danbolt
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
| | - Yun Zhou
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - David N Furness
- School of Life Sciences, Keele University, Keele, Staffs, United Kingdom
| | - Silvia Holmseth
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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43
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Kurioka T, Lee MY, Heeringa AN, Beyer LA, Swiderski DL, Kanicki AC, Kabara LL, Dolan DF, Shore SE, Raphael Y. Selective hair cell ablation and noise exposure lead to different patterns of changes in the cochlea and the cochlear nucleus. Neuroscience 2016; 332:242-57. [PMID: 27403879 DOI: 10.1016/j.neuroscience.2016.07.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 06/14/2016] [Accepted: 07/01/2016] [Indexed: 01/21/2023]
Abstract
In experimental animal models of auditory hair cell (HC) loss, insults such as noise or ototoxic drugs often lead to secondary changes or degeneration in non-sensory cells and neural components, including reduced density of spiral ganglion neurons, demyelination of auditory nerve fibers and altered cell numbers and innervation patterns in the cochlear nucleus (CN). However, it is not clear whether loss of HCs alone leads to secondary degeneration in these neural components of the auditory pathway. To elucidate this issue, we investigated changes of central components after cochlear insults specific to HCs using diphtheria toxin receptor (DTR) mice expressing DTR only in HCs and exhibiting complete HC loss when injected with diphtheria toxin (DT). We showed that DT-induced HC ablation has no significant impacts on the survival of auditory neurons, central synaptic terminals, and myelin, despite complete HC loss and profound deafness. In contrast, noise exposure induced significant changes in synapses, myelin and CN organization even without loss of inner HCs. We observed a decrease of neuronal size in the auditory pathway, including peripheral axons, spiral ganglion neurons, and CN neurons, likely due to loss of input from the cochlea. Taken together, selective HC ablation and noise exposure showed different patterns of pathology in the auditory pathway and the presence of HCs is not essential for the maintenance of central synaptic connectivity and myelination.
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Affiliation(s)
- Takaomi Kurioka
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Otorhinolaryngology-Head and Neck Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Min Young Lee
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Amarins N Heeringa
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Lisa A Beyer
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Donald L Swiderski
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Ariane C Kanicki
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Lisa L Kabara
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - David F Dolan
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Susan E Shore
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA.
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44
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Reijntjes DO, Pyott SJ. The afferent signaling complex: Regulation of type I spiral ganglion neuron responses in the auditory periphery. Hear Res 2016; 336:1-16. [DOI: 10.1016/j.heares.2016.03.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 02/12/2016] [Accepted: 03/07/2016] [Indexed: 12/19/2022]
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45
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Maison SF, Yin Y, Liberman LD, Liberman MC. Perinatal thiamine deficiency causes cochlear innervation abnormalities in mice. Hear Res 2016; 335:94-104. [PMID: 26944177 DOI: 10.1016/j.heares.2016.02.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 02/03/2016] [Accepted: 02/12/2016] [Indexed: 01/19/2023]
Abstract
Neonatal thiamine deficiency can cause auditory neuropathy in humans. To probe the underlying cochlear pathology, mice were maintained on a thiamine-free or low-thiamine diet during fetal development or early postnatal life. At postnatal ages from 18 days to 22 wks, cochlear function was tested and cochlear histopathology analyzed by plastic sections and cochlear epithelial whole-mounts immunostained for neuronal and synaptic markers. Although none of the thiamine-deprivation protocols resulted in any loss of hair cells or any obvious abnormalities in the non-sensory structures of the cochlear duct, all the experimental groups showed significant anomalies in the afferent or efferent innervation. Afferent synaptic counts in the inner and outer hair cell areas were reduced, as was the efferent innervation density in both the outer and inner hair cell areas. As expected for primary neural degeneration, the thresholds for distortion product otoacoustic emissions were not affected, and as expected for subtotal hair cell de-afferentation, the suprathreshold amplitudes of auditory brainstem responses were more affected than the response thresholds. We conclude that the auditory neuropathy from thiamine deprivation could be produced by loss of inner hair cell synapses.
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Affiliation(s)
- Stéphane F Maison
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston MA, USA; Harvard Program in Speech and Hearing Bioscience and Technology, Boston MA, USA.
| | - Yanbo Yin
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston MA, USA
| | - Leslie D Liberman
- Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston MA, USA
| | - M Charles Liberman
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston MA, USA; Harvard Program in Speech and Hearing Bioscience and Technology, Boston MA, USA
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Li S, Hang L, Ma Y. FGF22 protects hearing function from gentamycin ototoxicity by maintaining ribbon synapse number. Hear Res 2016; 332:39-45. [DOI: 10.1016/j.heares.2015.11.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 10/13/2015] [Accepted: 11/23/2015] [Indexed: 01/16/2023]
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Expression of glycine receptor alpha 3 in the rat trigeminal neurons and central boutons in the brainstem. Brain Struct Funct 2016; 221:4601-4613. [PMID: 26832918 DOI: 10.1007/s00429-016-1190-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 01/14/2016] [Indexed: 10/22/2022]
Abstract
Increasing evidence shows that the homomeric glycine receptor is expressed in axon terminals and is involved in the presynaptic modulation of transmitter release. However, little is known about the expression of the glycine receptor, implicated in the presynaptic modulation of sensory transmission in the primary somatosensory neurons and their central boutons. To address this, we investigated the expression of glycine receptor subunit alpha 3 (GlyRα3) in the neurons in the trigeminal ganglion and axon terminals in the 1st relay nucleus of the brainstem by light- and electron-microscopic immunohistochemistry. Trigeminal primary sensory neurons were GlyRα3-immunopositive/gephyrin-immunonegative (indicating homomeric GlyR), whereas GlyRα3/gephyrin immunoreactivity (indicating heteromeric GlyR) was observed in dendrites. GlyRα3 immunoreactivity was also found in the central boutons of primary afferents but far from the presynaptic site and in dendrites at subsynaptic sites. Boutons expressing GlyRα3 contained small round vesicles, formed asymmetric synapses with dendrites and were immunoreactive for glutamate. These findings suggest that trigeminal primary afferent boutons receive presynaptic modulation via homomeric, extrasynaptic GlyRα3, and that different subtypes of GlyR may be involved in pre- and postsynaptic inhibition.
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Noise-Induced Hearing Loss: Permanent Versus Temporary Threshold Shifts and the Effects of Hair Cell Versus Neuronal Degeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 875:1-7. [DOI: 10.1007/978-1-4939-2981-8_1] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Kujawa SG, Liberman MC. Synaptopathy in the noise-exposed and aging cochlea: Primary neural degeneration in acquired sensorineural hearing loss. Hear Res 2015; 330:191-9. [PMID: 25769437 PMCID: PMC4567542 DOI: 10.1016/j.heares.2015.02.009] [Citation(s) in RCA: 497] [Impact Index Per Article: 55.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 01/26/2015] [Accepted: 02/25/2015] [Indexed: 12/24/2022]
Abstract
The classic view of sensorineural hearing loss (SNHL) is that the "primary" targets are hair cells, and that cochlear-nerve loss is "secondary" to hair cell degeneration. Our recent work in mouse and guinea pig has challenged that view. In noise-induced hearing loss, exposures causing only reversible threshold shifts (and no hair cell loss) nevertheless cause permanent loss of >50% of cochlear-nerve/hair-cell synapses. Similarly, in age-related hearing loss, degeneration of cochlear synapses precedes both hair cell loss and threshold elevation. This primary neural degeneration has remained hidden for three reasons: 1) the spiral ganglion cells, the cochlear neural elements commonly assessed in studies of SNHL, survive for years despite loss of synaptic connection with hair cells, 2) the synaptic terminals of cochlear nerve fibers are unmyelinated and difficult to see in the light microscope, and 3) the degeneration is selective for cochlear-nerve fibers with high thresholds. Although not required for threshold detection in quiet (e.g. threshold audiometry or auditory brainstem response threshold), these high-threshold fibers are critical for hearing in noisy environments. Our research suggests that 1) primary neural degeneration is an important contributor to the perceptual handicap in SNHL, and 2) in cases where the hair cells survive, neurotrophin therapies can elicit neurite outgrowth from spiral ganglion neurons and re-establishment of their peripheral synapses. This article is part of a Special Issue entitled .
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Affiliation(s)
- Sharon G Kujawa
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA, USA; Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston, MA, USA; Department of Audiology, Massachusetts Eye and Ear, Boston, MA, USA
| | - M Charles Liberman
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA, USA; Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston, MA, USA.
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Goutman JD, Elgoyhen AB, Gómez-Casati ME. Cochlear hair cells: The sound-sensing machines. FEBS Lett 2015; 589:3354-61. [PMID: 26335749 PMCID: PMC4641020 DOI: 10.1016/j.febslet.2015.08.030] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 08/18/2015] [Accepted: 08/19/2015] [Indexed: 12/20/2022]
Abstract
The sensory epithelium of the mammalian inner ear contains two types of mechanosensory cells: inner (IHC) and outer hair cells (OHC). They both transduce mechanical force generated by sound waves into electrical signals. In their apical end, these cells possess a set of stereocilia representing the mechanosensing organelles. IHC are responsible for detecting sounds and transmitting the acoustic information to the brain by converting graded depolarization into trains of action potentials in auditory nerve fibers. OHC are responsible for the active mechanical amplification process that leads to the fine tuning and high sensitivity of the mammalian inner ear. This active amplification is the consequence of the ability of OHC to alter their cell length in response to changes in membrane potential, and is controlled by an efferent inhibitory innervation. Medial olivocochlear efferent fibers, originating in the brainstem, synapse directly at the base of OHC and release acetylcholine. A very special type of nicotinic receptor, assembled by α9α10 subunits, participates in this synapse. Here we review recent knowledge and the role of both afferent and efferent synapse in the inner ear.
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Affiliation(s)
- Juan D Goutman
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, "Dr. Héctor N Torres" (CONICET-UBA), Vuelta de Obligado 2490, Buenos Aires, Argentina.
| | - A Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, "Dr. Héctor N Torres" (CONICET-UBA), Vuelta de Obligado 2490, Buenos Aires, Argentina; Tercera Cátedra de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, Buenos Aires, Argentina
| | - María Eugenia Gómez-Casati
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, "Dr. Héctor N Torres" (CONICET-UBA), Vuelta de Obligado 2490, Buenos Aires, Argentina; Tercera Cátedra de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, Buenos Aires, Argentina.
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