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Kersbergen CJ, Bergles DE. Priming central sound processing circuits through induction of spontaneous activity in the cochlea before hearing onset. Trends Neurosci 2024:S0166-2236(24)00065-1. [PMID: 38782701 DOI: 10.1016/j.tins.2024.04.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 04/02/2024] [Accepted: 04/26/2024] [Indexed: 05/25/2024]
Abstract
Sensory systems experience a period of intrinsically generated neural activity before maturation is complete and sensory transduction occurs. Here we review evidence describing the mechanisms and functions of this 'spontaneous' activity in the auditory system. Both ex vivo and in vivo studies indicate that this correlated activity is initiated by non-sensory supporting cells within the developing cochlea, which induce depolarization and burst firing of groups of nearby hair cells in the sensory epithelium, activity that is conveyed to auditory neurons that will later process similar sound features. This stereotyped neural burst firing promotes cellular maturation, synaptic refinement, acoustic sensitivity, and establishment of sound-responsive domains in the brain. While sensitive to perturbation, the developing auditory system exhibits remarkable homeostatic mechanisms to preserve periodic burst firing in deaf mice. Preservation of this early spontaneous activity in the context of deafness may enhance the efficacy of later interventions to restore hearing.
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Affiliation(s)
- Calvin J Kersbergen
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
| | - Dwight E Bergles
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA; Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA; Department of Otolaryngology - Head and Neck Surgery, Johns Hopkins University, Baltimore, MD, USA; Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD, USA.
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2
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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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3
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Miyoshi T, Belyantseva IA, Sajeevadathan M, Friedman TB. Pathophysiology of human hearing loss associated with variants in myosins. Front Physiol 2024; 15:1374901. [PMID: 38562617 PMCID: PMC10982375 DOI: 10.3389/fphys.2024.1374901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 02/21/2024] [Indexed: 04/04/2024] Open
Abstract
Deleterious variants of more than one hundred genes are associated with hearing loss including MYO3A, MYO6, MYO7A and MYO15A and two conventional myosins MYH9 and MYH14. Variants of MYO7A also manifest as Usher syndrome associated with dysfunction of the retina and vestibule as well as hearing loss. While the functions of MYH9 and MYH14 in the inner ear are debated, MYO3A, MYO6, MYO7A and MYO15A are expressed in inner ear hair cells along with class-I myosin MYO1C and are essential for developing and maintaining functional stereocilia on the apical surface of hair cells. Stereocilia are large, cylindrical, actin-rich protrusions functioning as biological mechanosensors to detect sound, acceleration and posture. The rigidity of stereocilia is sustained by highly crosslinked unidirectionally-oriented F-actin, which also provides a scaffold for various proteins including unconventional myosins and their cargo. Typical myosin molecules consist of an ATPase head motor domain to transmit forces to F-actin, a neck containing IQ-motifs that bind regulatory light chains and a tail region with motifs recognizing partners. Instead of long coiled-coil domains characterizing conventional myosins, the tails of unconventional myosins have various motifs to anchor or transport proteins and phospholipids along the F-actin core of a stereocilium. For these myosins, decades of studies have elucidated their biochemical properties, interacting partners in hair cells and variants associated with hearing loss. However, less is known about how myosins traffic in a stereocilium using their motor function, and how each variant correlates with a clinical condition including the severity and onset of hearing loss, mode of inheritance and presence of symptoms other than hearing loss. Here, we cover the domain structures and functions of myosins associated with hearing loss together with advances, open questions about trafficking of myosins in stereocilia and correlations between hundreds of variants in myosins annotated in ClinVar and the corresponding deafness phenotypes.
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Affiliation(s)
- Takushi Miyoshi
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
- Division of Molecular and Integrative Physiology, Department of Biomedical Sciences, Southern Illinois University School of Medicine, Carbondale, IL, United States
| | - Inna A. Belyantseva
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Mrudhula Sajeevadathan
- Division of Molecular and Integrative Physiology, Department of Biomedical Sciences, Southern Illinois University School of Medicine, Carbondale, IL, United States
| | - Thomas B. Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
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4
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Hakizimana P. The sensitivity of mechanoelectrical transduction response phase to acoustic overstimulation is calcium-dependent. Pflugers Arch 2024; 476:271-282. [PMID: 37987805 DOI: 10.1007/s00424-023-02883-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 10/14/2023] [Accepted: 11/08/2023] [Indexed: 11/22/2023]
Abstract
The Mechanoelectrical transduction (MET) channels of the mammalian hair cells are essential for converting sound stimuli into electrical signals that enable hearing. However, the impact of acoustic overstimulation, a leading cause of hearing loss, on the MET channel function remains poorly understood. In this study, I investigated the effect of loud sound-induced temporary threshold shift (TTS) on the transduction response phase across a wide range of sound frequencies and amplitudes. The results demonstrated an increase in the transduction response phase following TTS, indicating altered transduction apparatus function. Further investigations involving the reduction of extracellular calcium, a known consequence of TTS, replicated the observed phase changes. Additionally, reduction of potassium entry confirmed the specific role of calcium in regulating the transduction response phase. These findings provide novel insights into the impact of loud sound exposure on hearing impairment at the transduction apparatus level and highlight the critical role of calcium in modulating sound transduction. Considering that over 1 billion teenagers and young adults globally are at risk of hearing loss due to unsafe music listening habits, these results could significantly enhance awareness about the damaging effects of loud sound exposure.
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Affiliation(s)
- Pierre Hakizimana
- Department of Biomedical and Clinical Sciences (BKV), Linköping University, 581 83, Linköping, Sweden.
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5
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Cho SH, Yun Y, Lee DH, Cha JH, Lee SM, Lee J, Suh MH, Lee JH, Oh SH, Park MK, Lee SY. Novel autosomal dominant TMC1 variants linked to hearing loss: insight into protein-lipid interactions. BMC Med Genomics 2023; 16:320. [PMID: 38066485 PMCID: PMC10704677 DOI: 10.1186/s12920-023-01766-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 12/05/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND TMC1, which encodes transmembrane channel-like protein 1, forms the mechanoelectrical transduction (MET) channel in auditory hair cells, necessary for auditory function. TMC1 variants are known to cause autosomal dominant (DFNA36) and autosomal recessive (DFNB7/11) non-syndromic hearing loss, but only a handful of TMC1 variants underlying DFNA36 have been reported, hampering analysis of genotype-phenotype correlations. METHODS In this study, we retrospectively reviewed 338 probands in an in-house database of genetic hearing loss, evaluating the clinical phenotypes and genotypes of novel TMC1 variants associated with DFNA36. To analyze the structural impact of these variants, we generated two structural models of human TMC1, utilizing the Cryo-EM structure of C. elegans TMC1 as a template and AlphaFold protein structure database. Specifically, the lipid bilayer-embedded protein database was used to construct membrane-embedded models of TMC1. We then examined the effect of TMC1 variants on intramolecular interactions and predicted their potential pathogenicity. RESULTS We identified two novel TMC1 variants related to DFNA36 (c.1256T > C:p.Phe419Ser and c.1444T > C:p.Trp482Arg). The affected subjects had bilateral, moderate, late-onset, progressive sensorineural hearing loss with a down-sloping configuration. The Phe419 residue located in the transmembrane domain 4 of TMC1 faces outward towards the channel pore and is in close proximity to the hydrophobic tail of the lipid bilayer. The non-polar-to-polar variant (p.Phe419Ser) alters the hydrophobicity in the membrane, compromising protein-lipid interactions. On the other hand, the Trp482 residue located in the extracellular linker region between transmembrane domains 5 and 6 is anchored to the membrane interfaces via its aromatic rings, mediating several molecular interactions that stabilize the structure of TMC1. This type of aromatic ring-based anchoring is also observed in homologous transmembrane proteins such as OSCA1.2. Conversely, the substitution of Trp with Arg (Trp482Arg) disrupts the cation-π interaction with phospholipids located in the outer leaflet of the phospholipid bilayer, destabilizing protein-lipid interactions. Additionally, Trp482Arg collapses the CH-π interaction between Trp482 and Pro511, possibly reducing the overall stability of the protein. In parallel with the molecular modeling, the two mutants degraded significantly faster compared to the wild-type protein, compromising protein stability. CONCLUSIONS This results expand the genetic spectrum of disease-causing TMC1 variants related to DFNA36 and provide insight into TMC1 transmembrane protein-lipid interactions.
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Affiliation(s)
- Sung Ho Cho
- Seoul National University College of Medicine, Seoul, South Korea
| | - Yejin Yun
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea
| | - Dae Hee Lee
- CTCELLS, Inc, 21, Yuseong-daero, 1205beon-gil, Yuseong-gu, Daejeon, Republic of Korea
| | - Joo Hyun Cha
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea
| | - So Min Lee
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea
| | - Jehyun Lee
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea
| | - Myung Hwan Suh
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea
| | - Jun Ho Lee
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea
| | - Seung-Ha Oh
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea
| | - Moo Kyun Park
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea.
- Sensory Organ Research Institute, Seoul National University Medical Research Center, Seoul, South Korea.
| | - Sang-Yeon Lee
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Jongno-Gu, Daehak-Ro, 101, Seoul, South Korea.
- Sensory Organ Research Institute, Seoul National University Medical Research Center, Seoul, South Korea.
- Department of Genomic Medicine, Precision Medicine & Rare Disease Center, Seoul, South Korea.
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Villasante CM, Deng X, Cohen JE, Hudspeth AJ. Nanomechanics of wild-type and mutant dimers of the tip-link protein protocadherin 15. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.17.562769. [PMID: 37905108 PMCID: PMC10614884 DOI: 10.1101/2023.10.17.562769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Mechanical force controls the opening and closing of mechanosensitive ion channels atop the hair bundles of the inner ear. The filamentous tip link connecting transduction channels to the tallest neighboring stereocilium modulates the force transmitted to the channels and thus changes their probability of opening. Each tip link comprises four molecules: a dimer of protocadherin 15 and a dimer of cadherin 23, all of which are stabilized by Ca2+ binding. Using a high-speed optical trap to examine dimeric PCDH15, we find that the protein's configuration is sensitive to Ca2+ and that the molecule exhibits limited unfolding at a physiological Ca2+ concentration. PCDH15 can therefore modulate its stiffness without undergoing large unfolding events in physiological Ca2+ conditions. The experimentally determined stiffness of PCDH15 accords with published values for the stiffness of the gating spring, the mechanical element that controls the opening of mechanotransduction channels. When PCDH15 has a point mutation, V507D, associated with non-syndromic hearing loss, unfolding events occur more frequently under tension and refolding events occur less often than in the wild-type protein. Our results suggest that the maintenance of appropriate tension in the gating spring is critical to the appropriate transmission of force to transduction channels, and hence to hearing.
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Affiliation(s)
- Camila M Villasante
- Laboratory of Sensory Neuroscience, The Rockefeller University, New York, NY 10065 USA
| | - Xinyue Deng
- Laboratory of Sensory Neuroscience, The Rockefeller University, New York, NY 10065 USA
| | - Joel E Cohen
- Laboratory of Populations, The Rockefeller University, New York, NY 10065 USA
- Earth Institute and Department of Statistics, Columbia University, New York, NY 10027 USA
- Department of Statistics, University of Chicago, Chicago, IL 60637 USA
| | - A J Hudspeth
- Laboratory of Sensory Neuroscience, The Rockefeller University, New York, NY 10065 USA
- Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065 USA
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7
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Guo J, Mei H, Zhang Y, Che C, Guo L, Zhang Y, Li H, Sun S. Glutamate-aspartate transporter dysfunction enhances aminoglycoside-induced cochlear hair cell death via NMDA receptor activation. Neurochem Int 2023; 169:105587. [PMID: 37495172 DOI: 10.1016/j.neuint.2023.105587] [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: 04/24/2023] [Revised: 07/02/2023] [Accepted: 07/23/2023] [Indexed: 07/28/2023]
Abstract
Glutamate is a crucial neurotransmitter for hearing transduction in the cochlea, but excess glutamate is detrimental to the survival of cochlear sensory cells. Glutamate-aspartate transporter (GLAST) is the major transporter for glutamate removal; however, its role in aminoglycoside-induced hair cell loss is not well studied. In the present study, we first investigated the localization and expression of GLAST over the course of development of the mouse cochlea, and we found that inhibition of GLAST increased hair cell death. However, when the glutamate receptor NMDAR was inhibited by D-AP5, hair cell death was no longer increased by the GLAST inhibitor. Our results indicate that GLAST inhibition aggravates damage to cochlear hair cells, which may occur via NMDAR, and this suggests new clinical strategies for ameliorating the ototoxicity associated with the dysfunction of glutamate metabolism.
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Affiliation(s)
- Jin Guo
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Honglin Mei
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Yanping Zhang
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Chenhao Che
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Luo Guo
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Yunzhong Zhang
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China
| | - Huawei Li
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; The Institutes of Brain Science and the Collaborative Innovation Center for Brain Science, Fudan University, Shanghai, 200032, China.
| | - Shan Sun
- ENT Institute and Otorhinolaryngology Department of Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, 200031, China.
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8
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Carlton AJ, Jeng J, Grandi FC, De Faveri F, Ceriani F, De Tomasi L, Underhill A, Johnson SL, Legan KP, Kros CJ, Richardson GP, Mustapha M, Marcotti W. A critical period of prehearing spontaneous Ca 2+ spiking is required for hair-bundle maintenance in inner hair cells. EMBO J 2023; 42:e112118. [PMID: 36594367 PMCID: PMC9929643 DOI: 10.15252/embj.2022112118] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Revised: 11/22/2022] [Accepted: 11/28/2022] [Indexed: 01/04/2023] Open
Abstract
Sensory-independent Ca2+ spiking regulates the development of mammalian sensory systems. In the immature cochlea, inner hair cells (IHCs) fire spontaneous Ca2+ action potentials (APs) that are generated either intrinsically or by intercellular Ca2+ waves in the nonsensory cells. The extent to which either or both of these Ca2+ signalling mechansims are required for IHC maturation is unknown. We find that intrinsic Ca2+ APs in IHCs, but not those elicited by Ca2+ waves, regulate the maturation and maintenance of the stereociliary hair bundles. Using a mouse model in which the potassium channel Kir2.1 is reversibly overexpressed in IHCs (Kir2.1-OE), we find that IHC membrane hyperpolarization prevents IHCs from generating intrinsic Ca2+ APs but not APs induced by Ca2+ waves. Absence of intrinsic Ca2+ APs leads to the loss of mechanoelectrical transduction in IHCs prior to hearing onset due to progressive loss or fusion of stereocilia. RNA-sequencing data show that pathways involved in morphogenesis, actin filament-based processes, and Rho-GTPase signaling are upregulated in Kir2.1-OE mice. By manipulating in vivo expression of Kir2.1 channels, we identify a "critical time period" during which intrinsic Ca2+ APs in IHCs regulate hair-bundle function.
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Affiliation(s)
| | - Jing‐Yi Jeng
- School of BiosciencesUniversity of SheffieldSheffieldUK
| | | | | | | | | | | | - Stuart L Johnson
- School of BiosciencesUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
| | - Kevin P Legan
- School of Life SciencesUniversity of Sussex, FalmerBrightonUK
| | - Corné J Kros
- School of Life SciencesUniversity of Sussex, FalmerBrightonUK
| | | | - Mirna Mustapha
- School of BiosciencesUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
| | - Walter Marcotti
- School of BiosciencesUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
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9
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Jeng JY, Carlton AJ, Goodyear RJ, Chinowsky C, Ceriani F, Johnson SL, Sung TC, Dayn Y, Richardson GP, Bowl MR, Brown SD, Manor U, Marcotti W. AAV-mediated rescue of Eps8 expression in vivo restores hair-cell function in a mouse model of recessive deafness. Mol Ther Methods Clin Dev 2022; 26:355-370. [PMID: 36034774 PMCID: PMC9382420 DOI: 10.1016/j.omtm.2022.07.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 07/15/2022] [Indexed: 11/24/2022]
Abstract
The transduction of acoustic information by hair cells depends upon mechanosensitive stereociliary bundles that project from their apical surface. Mutations or absence of the stereociliary protein EPS8 cause deafness in humans and mice, respectively. Eps8 knockout mice (Eps8 -/- ) have hair cells with immature stereocilia and fail to become sensory receptors. Here, we show that exogenous delivery of Eps8 using Anc80L65 in P1-P2 Eps8 -/- mice in vivo rescued the hair bundle structure of apical-coil hair cells. Rescued hair bundles correctly localize EPS8, WHIRLIN, MYO15, and BAIAP2L2, and generate normal mechanoelectrical transducer currents. Inner hair cells with normal-looking stereocilia re-expressed adult-like basolateral ion channels (BK and KCNQ4) and have normal exocytosis. The number of hair cells undergoing full recovery was not sufficient to rescue hearing in Eps8 -/- mice. Adeno-associated virus (AAV)-transduction of P3 apical-coil and P1-P2 basal-coil hair cells does not rescue hair cells, nor does Anc80L65-Eps8 delivery in adult Eps8 -/- mice. We propose that AAV-induced gene-base therapy is an efficient strategy to recover the complex hair-cell defects in Eps8 -/- mice. However, this therapeutic approach may need to be performed in utero since, at postnatal ages, Eps8 -/- hair cells appear to have matured or accumulated damage beyond the point of repair.
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Affiliation(s)
- Jing-Yi Jeng
- School of Bioscience, University of Sheffield, Sheffield S10 2TN, UK
| | - Adam J. Carlton
- School of Bioscience, University of Sheffield, Sheffield S10 2TN, UK
| | - Richard J. Goodyear
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
| | - Colbie Chinowsky
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Federico Ceriani
- School of Bioscience, University of Sheffield, Sheffield S10 2TN, UK
| | - Stuart L. Johnson
- School of Bioscience, University of Sheffield, Sheffield S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, UK
| | - Tsung-Chang Sung
- Transgenic Core, Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Yelena Dayn
- Transgenic Core, Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Guy P. Richardson
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
| | - Michael R. Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Campus, Oxfordshire OX11 0RD UK
| | - Steve D.M. Brown
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Campus, Oxfordshire OX11 0RD UK
| | - Uri Manor
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Walter Marcotti
- School of Bioscience, University of Sheffield, Sheffield S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield S10 2TN, UK
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10
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Grierson KE, Hickman TT, Liberman MC. Dopaminergic and cholinergic innervation in the mouse cochlea after noise-induced or age-related synaptopathy. Hear Res 2022; 422:108533. [PMID: 35671600 DOI: 10.1016/j.heares.2022.108533] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 04/11/2022] [Accepted: 05/20/2022] [Indexed: 11/17/2022]
Abstract
Cochlear synaptopathy, the loss of or damage to connections between auditory-nerve fibers (ANFs) and inner hair cells (IHCs), is a prominent pathology in noise-induced and age-related hearing loss. Here, we investigated if degeneration of the olivocochlear (OC) efferent innervation is also a major aspect of the synaptopathic ear, by quantifying the volume and spatial organization of its cholinergic and dopaminergic components, using antibodies to vesicular acetylcholine transporter (VAT) and tyrosine hydroxylase (TH), respectively. CBA/CaJ male mice were examined 1 day to 8 months after a synaptopathic noise exposure, and compared to unexposed age-matched controls and unexposed aged mice at 24-28 months. In normal ears, cholinergic lateral (L)OC terminals were denser in the apical half of the cochlea and on the modiolar side of the inner hair cells (IHCs), where ANFs of low-spontaneous rate are typically found, while dopaminergic terminals were more common in the basal third of the cochlea and, re the IHC axes, were offset towards the habenula with respect to cholinergic terminals. The noise had only small and transient effects on the density of LOC innervation, its spatial organization around the IHC axes, or the extent to which TH and VAT signal were colocalized. The synaptopathic noise also had relatively small and transient effects on cholinergic innervation density in the outer hair cell (OHC) area, which normally peaks in the 16 kHz region and falls monotonically towards higher and lower frequencies. In contrast, in the aged ears, there was massive degeneration of OHC efferents, especially in the apical half of the cochlea, where there was also significant loss of OHCs. In the IHC area, there was significant loss of cholinergic terminals in both apical and basal regions and of dopaminergic innervation in the basal half. Furthermore, the cholinergic terminals in the aged ears spread from their normal clustering near the IHC basolateral pole, where the ANF synapses are found, to positions up and down the IHC somata and regions of the neuropil closer to the habenula. This apparent migration was most striking in the apex, where the hair cell pathology was greatest, and may be a harbinger of impending hair cell death.
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Affiliation(s)
- Kiera E Grierson
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, 02114 USA; Dept of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, 02115 USA; Hearing Research Lab, Garvan Institute of Medical Research, Darlinghurst, NSW, 2010, AUS
| | - Tyler T Hickman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, 02114 USA; Dept of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, 02115 USA.
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, 02114 USA; Dept of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, MA, 02115 USA
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11
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Spaiardi P, Marcotti W, Masetto S, Johnson SL. Signal transmission in mature mammalian vestibular hair cells. Front Cell Neurosci 2022; 16:806913. [PMID: 35936492 PMCID: PMC9353129 DOI: 10.3389/fncel.2022.806913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 06/27/2022] [Indexed: 11/13/2022] Open
Abstract
The maintenance of balance and gaze relies on the faithful and rapid signaling of head movements to the brain. In mammals, vestibular organs contain two types of sensory hair cells, type-I and type-II, which convert the head motion-induced movement of their hair bundles into a graded receptor potential that drives action potential activity in their afferent fibers. While signal transmission in both hair cell types involves Ca2+-dependent quantal release of glutamate at ribbon synapses, type-I cells appear to also exhibit a non-quantal mechanism that is believed to increase transmission speed. However, the reliance of mature type-I hair cells on non-quantal transmission remains unknown. Here we investigated synaptic transmission in mammalian utricular hair cells using patch-clamp recording of Ca2+ currents and changes in membrane capacitance (ΔCm). We found that mature type-II hair cells showed robust exocytosis with a high-order dependence on Ca2+ entry. By contrast, exocytosis was approximately 10 times smaller in type-I hair cells. Synaptic vesicle exocytosis was largely absent in mature vestibular hair cells of CaV1.3 (CaV1.3−/−) and otoferlin (Otof−/−) knockout mice. Even though Ca2+-dependent exocytosis was small in type-I hair cells of wild-type mice, or absent in CaV1.3−/− and Otof−/−mice, these cells were able to drive action potential activity in the postsynaptic calyces. This supports a functional role for non-quantal synaptic transmission in type-I cells. The large vesicle pools in type-II cells would facilitate sustained transmission of tonic or low-frequency signals. In type-I cells, the restricted vesicle pool size, together with a rapid non-quantal mechanism, could allow them to sustain high-frequency phasic signal transmission at their specialized large calyceal synapses.
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Affiliation(s)
- Paolo Spaiardi
- Department of Brain and Behavioural Sciences, University of Pavia, Pavia, Italy
- Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
| | - Walter Marcotti
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom
- Sheffield Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Sergio Masetto
- Department of Brain and Behavioural Sciences, University of Pavia, Pavia, Italy
| | - Stuart L. Johnson
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom
- Sheffield Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
- *Correspondence: Stuart L. Johnson
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12
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Oncomodulin (OCM) uniquely regulates calcium signaling in neonatal cochlear outer hair cells. Cell Calcium 2022; 105:102613. [PMID: 35797824 PMCID: PMC9297295 DOI: 10.1016/j.ceca.2022.102613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 06/06/2022] [Accepted: 06/09/2022] [Indexed: 11/23/2022]
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13
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Zhang Q, Kindt KS. Using Light-Sheet Microscopy to Study Spontaneous Activity in the Developing Lateral-Line System. Front Cell Dev Biol 2022; 10:819612. [PMID: 35592245 PMCID: PMC9112283 DOI: 10.3389/fcell.2022.819612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Accepted: 01/18/2022] [Indexed: 11/13/2022] Open
Abstract
Hair cells are the sensory receptors in the auditory and vestibular systems of all vertebrates, and in the lateral-line system of aquatic vertebrates. The purpose of this work is to explore the zebrafish lateral-line system as a model to study and understand spontaneous activity in vivo. Our work applies genetically encoded calcium indicators along with light-sheet fluorescence microscopy to visualize spontaneous calcium activity in the developing lateral-line system. Consistent with our previous work, we show that spontaneous calcium activity is present in developing lateral-line hair cells. We now show that supporting cells that surround hair cells, and cholinergic efferent terminals that directly contact hair cells are also spontaneously active. Using two-color functional imaging we demonstrate that spontaneous activity in hair cells does not correlate with activity in either supporting cells or cholinergic terminals. We find that during lateral-line development, hair cells autonomously generate spontaneous events. Using localized calcium indicators, we show that within hair cells, spontaneous calcium activity occurs in two distinct domains—the mechanosensory bundle and the presynapse. Further, spontaneous activity in the mechanosensory bundle ultimately drives spontaneous calcium influx at the presynapse. Comprehensively, our results indicate that in developing lateral-line hair cells, autonomously generated spontaneous activity originates with spontaneous mechanosensory events.
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14
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Levic S. SK Current, Expressed During the Development and Regeneration of Chick Hair Cells, Contributes to the Patterning of Spontaneous Action Potentials. Front Cell Neurosci 2022; 15:766264. [PMID: 35069114 PMCID: PMC8770932 DOI: 10.3389/fncel.2021.766264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 11/29/2021] [Indexed: 11/30/2022] Open
Abstract
Chick hair cells display calcium (Ca2+)-sensitive spontaneous action potentials during development and regeneration. The role of this activity is unclear but thought to be involved in establishing proper synaptic connections and tonotopic maps, both of which are instrumental to normal hearing. Using an electrophysiological approach, this work investigated the functional expression of Ca2+-sensitive potassium [IK(Ca)] currents and their role in spontaneous electrical activity in the developing and regenerating hair cells (HCs) in the chick basilar papilla. The main IK(Ca) in developing and regenerating chick HCs is an SK current, based on its sensitivity to apamin. Analysis of the functional expression of SK current showed that most dramatic changes occurred between E8 and E16. Specifically, there is a developmental downregulation of the SK current after E16. The SK current gating was very sensitive to the availability of intracellular Ca2+ but showed very little sensitivity to T-type voltage-gated Ca2+ channels, which are one of the hallmarks of developing and regenerating hair cells. Additionally, apamin reduced the frequency of spontaneous electrical activity in HCs, suggesting that SK current participates in patterning the spontaneous electrical activity of HCs.
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Affiliation(s)
- Snezana Levic
- Center for Neuroscience, University of California, Davis, Davis, CA, United States
- Sensory Neuroscience Research Group, School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom
- Brighton and Sussex Medical School, University of Sussex, Brighton, United Kingdom
- *Correspondence: Snezana Levic,
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15
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Newton S, Kong F, Carlton AJ, Aguilar C, Parker A, Codner GF, Teboul L, Wells S, Brown SDM, Marcotti W, Bowl MR. Neuroplastin genetically interacts with Cadherin 23 and the encoded isoform Np55 is sufficient for cochlear hair cell function and hearing. PLoS Genet 2022; 18:e1009937. [PMID: 35100259 PMCID: PMC8830789 DOI: 10.1371/journal.pgen.1009937] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 02/10/2022] [Accepted: 01/13/2022] [Indexed: 11/25/2022] Open
Abstract
Mammalian hearing involves the mechanoelectrical transduction (MET) of sound-induced fluid waves in the cochlea. Essential to this process are the specialised sensory cochlear cells, the inner (IHCs) and outer hair cells (OHCs). While genetic hearing loss is highly heterogeneous, understanding the requirement of each gene will lead to a better understanding of the molecular basis of hearing and also to therapeutic opportunities for deafness. The Neuroplastin (Nptn) gene, which encodes two protein isoforms Np55 and Np65, is required for hearing, and homozygous loss-of-function mutations that affect both isoforms lead to profound deafness in mice. Here we have utilised several distinct mouse models to elaborate upon the spatial, temporal, and functional requirement of Nptn for hearing. While we demonstrate that both Np55 and Np65 are present in cochlear cells, characterisation of a Np65-specific mouse knockout shows normal hearing thresholds indicating that Np65 is functionally redundant for hearing. In contrast, we find that Nptn-knockout mice have significantly reduced maximal MET currents and MET channel open probabilities in mature OHCs, with both OHCs and IHCs also failing to develop fully mature basolateral currents. Furthermore, comparing the hearing thresholds and IHC synapse structure of Nptn-knockout mice with those of mice that lack Nptn only in IHCs and OHCs shows that the majority of the auditory deficit is explained by hair cell dysfunction, with abnormal afferent synapses contributing only a small proportion of the hearing loss. Finally, we show that continued expression of Neuroplastin in OHCs of adult mice is required for membrane localisation of Plasma Membrane Ca2+ ATPase 2 (PMCA2), which is essential for hearing function. Moreover, Nptn haploinsufficiency phenocopies Atp2b2 (encodes PMCA2) mutations, with heterozygous Nptn-knockout mice exhibiting hearing loss through genetic interaction with the Cdh23ahl allele. Together, our findings provide further insight to the functional requirement of Neuroplastin for mammalian hearing.
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Affiliation(s)
- Sherylanne Newton
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Fanbo Kong
- School of Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Adam J. Carlton
- School of Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Carlos Aguilar
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Andrew Parker
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Gemma F. Codner
- Mary Lyon Centre, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Lydia Teboul
- Mary Lyon Centre, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Sara Wells
- Mary Lyon Centre, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Steve D. M. Brown
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Walter Marcotti
- School of Sciences, University of Sheffield, Sheffield, United Kingdom
- Sheffield Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Michael R. Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
- UCL Ear Institute, University College London, London, United Kingdom
- * E-mail:
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16
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Miller KK, Atkinson P, Mendoza KR, Ó Maoiléidigh D, Grillet N. Dimensions of a Living Cochlear Hair Bundle. Front Cell Dev Biol 2021; 9:742529. [PMID: 34900993 PMCID: PMC8657763 DOI: 10.3389/fcell.2021.742529] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 10/13/2021] [Indexed: 11/23/2022] Open
Abstract
The hair bundle is the mechanosensory organelle of hair cells that detects mechanical stimuli caused by sounds, head motions, and fluid flows. Each hair bundle is an assembly of cellular-protrusions called stereocilia, which differ in height to form a staircase. Stereocilia have different heights, widths, and separations in different species, sensory organs, positions within an organ, hair-cell types, and even within a single hair bundle. The dimensions of the stereociliary assembly dictate how the hair bundle responds to stimuli. These hair-bundle properties have been measured previously only to a limited degree. In particular, mammalian data are either incomplete, lack control for age or position within an organ, or have artifacts owing to fixation or dehydration. Here, we provide a complete set of measurements for postnatal day (P) 11 C57BL/6J mouse apical inner hair cells (IHCs) obtained from living tissue, tissue mildly-fixed for fluorescent imaging, or tissue strongly fixed and dehydrated for scanning electronic microscopy (SEM). We found that hair bundles mildly-fixed for fluorescence had the same dimensions as living hair bundles, whereas SEM-prepared hair bundles shrank uniformly in stereociliary heights, widths, and separations. By determining the shrinkage factors, we imputed live dimensions from SEM that were too small to observe optically. Accordingly, we created the first complete blueprint of a living IHC hair bundle. We show that SEM-prepared measurements strongly affect calculations of a bundle’s mechanical properties – overestimating stereociliary deflection stiffness and underestimating the fluid coupling between stereocilia. The methods of measurement, the data, and the consequences we describe illustrate the high levels of accuracy and precision required to understand hair-bundle mechanotransduction.
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Affiliation(s)
- Katharine K Miller
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Stanford University, Stanford, CA, United States
| | - Patrick Atkinson
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Stanford University, Stanford, CA, United States
| | - Kyssia Ruth Mendoza
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Stanford University, Stanford, CA, United States
| | - Dáibhid Ó Maoiléidigh
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Stanford University, Stanford, CA, United States
| | - Nicolas Grillet
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Stanford University, Stanford, CA, United States
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17
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Lee J, Kawai K, Holt JR, Géléoc GSG. Sensory transduction is required for normal development and maturation of cochlear inner hair cell synapses. eLife 2021; 10:e69433. [PMID: 34734805 PMCID: PMC8598158 DOI: 10.7554/elife.69433] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 11/01/2021] [Indexed: 12/23/2022] Open
Abstract
Acoustic overexposure and aging can damage auditory synapses in the inner ear by a process known as synaptopathy. These insults may also damage hair bundles and the sensory transduction apparatus in auditory hair cells. However, a connection between sensory transduction and synaptopathy has not been established. To evaluate potential contributions of sensory transduction to synapse formation and development, we assessed inner hair cell synapses in several genetic models of dysfunctional sensory transduction, including mice lacking transmembrane channel-like (Tmc) 1, Tmc2, or both, in Beethoven mice which carry a dominant Tmc1 mutation and in Spinner mice which carry a recessive mutation in transmembrane inner ear (Tmie). Our analyses reveal loss of synapses in the absence of sensory transduction and preservation of synapses in Tmc1-null mice following restoration of sensory transduction via Tmc1 gene therapy. These results provide insight into the requirement of sensory transduction for hair cell synapse development and maturation.
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Affiliation(s)
- John Lee
- Speech and Hearing Bioscience & Technology Program, Division of Medical Sciences, Harvard UniversityBostonUnited States
- Department of Otolaryngology, Boston Children’s Hospital and Harvard Medical SchoolBostonUnited States
| | - Kosuke Kawai
- Department of Otolaryngology, Boston Children’s Hospital and Harvard Medical SchoolBostonUnited States
| | - Jeffrey R Holt
- Department of Otolaryngology, Boston Children’s Hospital and Harvard Medical SchoolBostonUnited States
- Department of Neurology, Boston Children’s Hospital and Harvard Medical SchoolBostonUnited States
| | - Gwenaëlle SG Géléoc
- Department of Otolaryngology, Boston Children’s Hospital and Harvard Medical SchoolBostonUnited States
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18
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Vicencio-Jimenez S, Weinberg MM, Bucci-Mansilla G, Lauer AM. Olivocochlear Changes Associated With Aging Predominantly Affect the Medial Olivocochlear System. Front Neurosci 2021; 15:704805. [PMID: 34539335 PMCID: PMC8446540 DOI: 10.3389/fnins.2021.704805] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 08/02/2021] [Indexed: 11/13/2022] Open
Abstract
Age-related hearing loss (ARHL) is a public health problem that has been associated with negative health outcomes ranging from increased frailty to an elevated risk of developing dementia. Significant gaps remain in our knowledge of the underlying central neural mechanisms, especially those related to the efferent auditory pathways. Thus, the aim of this study was to quantify and compare age-related alterations in the cholinergic olivocochlear efferent auditory neurons. We assessed, in young-adult and aged CBA mice, the number of cholinergic olivocochlear neurons, auditory brainstem response (ABR) thresholds in silence and in presence of background noise, and the expression of excitatory and inhibitory proteins in the ventral nucleus of the trapezoid body (VNTB) and in the lateral superior olive (LSO). In association with aging, we found a significant decrease in the number of medial olivocochlear (MOC) cholinergic neurons together with changes in the ratio of excitatory and inhibitory proteins in the VNTB. Furthermore, in old mice we identified a correlation between the number of MOC neurons and ABR thresholds in the presence of background noise. In contrast, the alterations observed in the lateral olivocochlear (LOC) system were less significant. The decrease in the number of LOC cells associated with aging was 2.7-fold lower than in MOC and in the absence of changes in the expression of excitatory and inhibitory proteins in the LSO. These differences suggest that aging alters the medial and lateral olivocochlear efferent pathways in a differential manner and that the changes observed may account for some of the symptoms seen in ARHL.
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Affiliation(s)
- Sergio Vicencio-Jimenez
- The Center for Hearing and Balance, Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Madison M Weinberg
- The Center for Hearing and Balance, Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Giuliana Bucci-Mansilla
- Laboratorio de Neurosistemas, Departamento de Neurociencia, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Amanda M Lauer
- The Center for Hearing and Balance, Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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19
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Liu C, Zhao B. Murine GRXCR1 Has a Different Function Than GRXCR2 in the Morphogenesis of Stereocilia. Front Cell Neurosci 2021; 15:714070. [PMID: 34366792 PMCID: PMC8333275 DOI: 10.3389/fncel.2021.714070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 06/25/2021] [Indexed: 11/13/2022] Open
Abstract
Mutations in human glutaredoxin domain-containing cysteine-rich protein 1 (GRXCR1) and its paralog GRXCR2 have been linked to hearing loss in humans. Although both GRXCR1 and GRXCR2 are required for the morphogenesis of stereocilia in cochlear hair cells, a fundamental question that remains unclear is whether GRXCR1 and GRXCR2 have similar functions in hair cells. Previously, we found that GRXCR2 is critical for the stereocilia morphogenesis by regulating taperin localization at the base of stereocilia. Reducing taperin expression level rescues the morphological defects of stereocilia and hearing loss in Grxcr2-deficient mice. So far, functions of GRXCR1 in mammalian hair cells are still unclear. Grxcr1-deficient hair cells have very thin stereocilia with less F-actin content inside, which is different from Grxcr2-deficient hair cells. In contrast to GRXCR2, which is concentrated at the base of stereocilia, GRXCR1 is diffusely distributed throughout the stereocilia. Notably, GRXCR1 interacts with GRXCR2. In Grxcr1-deficient hair cells, the expression level of GRXCR2 and taperin is reduced. Remarkably, different from that in Grxcr2-deficient mice, reducing taperin expression level does not rescue the morphological defects of stereocilia or hearing loss in Grxcr1-deficient mice. Thus, our findings suggest that GRXCR1 has different functions than GRXCR2 during the morphogenesis of stereocilia.
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Affiliation(s)
- Chang Liu
- Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Bo Zhao
- Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN, United States
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20
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Barravecchia I, Demontis GC. HCN1 channels: A versatile tool for signal processing by primary sensory neurons. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:133-146. [PMID: 34197835 DOI: 10.1016/j.pbiomolbio.2021.06.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 06/11/2021] [Accepted: 06/25/2021] [Indexed: 12/20/2022]
Abstract
Most primary sensory neurons (PSNs) generate a slowly-activating inward current in response to membrane hyperpolarization (Ih) and express HCN1 along with additional isoforms coding for hyperpolarization-activated channels (HCN). Changes in HCN expression may affect the excitability and firing patterns of PSNs, but retinal and inner ear PSNs do not fire action potentials, suggesting HCN channel roles may extend beyond excitability and cell firing control. In patients taking Ih blockers, photopsia triggered in response to abrupt changes in luminance correlates with impaired visual signal processing via parallel rod and cone pathways. Furthermore, in a mouse model of inherited retinal degeneration, HCN blockers or Hcn1 genetic ablation may worsen photoreceptors' demise. PSN's use of HCN channels to adjust either their firing rate or process signals generated by sensory transduction in non-spiking PSNs indicates HCN1 channels as a versatile tool with a novel role in sensory processing beyond firing control.
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Affiliation(s)
- Ivana Barravecchia
- Department of Pharmacy, Università di Pisa, Italy, Via Bonanno, 6, 56126, Pisa, Italy; Istitute of Life Science, Scuola Superiore Sant' Anna, 56127, Pisa, Italy.
| | - Gian Carlo Demontis
- Department of Pharmacy, Università di Pisa, Italy, Via Bonanno, 6, 56126, Pisa, Italy.
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21
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Tani T, Koike-Tani M, Tran MT, Shribak M, Levic S. Postnatal structural development of mammalian Basilar Membrane provides anatomical basis for the maturation of tonotopic maps and frequency tuning. Sci Rep 2021; 11:7581. [PMID: 33828185 PMCID: PMC8027603 DOI: 10.1038/s41598-021-87150-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 03/16/2021] [Indexed: 02/01/2023] Open
Abstract
The basilar membrane (BM) of the mammalian cochlea constitutes a spiraling acellular ribbon that is intimately attached to the organ of Corti. Its graded stiffness, increasing from apex to the base of the cochlea provides the mechanical basis for sound frequency analysis. Despite its central role in auditory signal transduction, virtually nothing is known about the BM's structural development. Using polarized light microscopy, the present study characterized the architectural transformations of freshly dissected BM at time points during postnatal development and maturation. The results indicate that the BM structural elements increase progressively in size, becoming radially aligned and more tightly packed with maturation and reach the adult structural signature by postnatal day 20 (P20). The findings provide insight into structural details and developmental changes of the mammalian BM, suggesting that BM is a dynamic structure that changes throughout the life of an animal.
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Affiliation(s)
- Tomomi Tani
- Marine Biological Laboratory, Eugene Bell Center, Woods Hole, MA, USA
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ikeda, Osaka, Japan
| | - Maki Koike-Tani
- Marine Biological Laboratory, Eugene Bell Center, Woods Hole, MA, USA
- Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University, Suita, Osaka, Japan
| | - Mai Thi Tran
- Marine Biological Laboratory, Eugene Bell Center, Woods Hole, MA, USA
- College of Engineering and Computer Science, VinUniversity, Gia Lam District, Hanoi, Vietnam
| | - Michael Shribak
- Marine Biological Laboratory, Eugene Bell Center, Woods Hole, MA, USA
| | - Snezana Levic
- Marine Biological Laboratory, Eugene Bell Center, Woods Hole, MA, USA.
- Sensory Neuroscience Research Group, School of Pharmacy and Biomolecular Sciences, University of Brighton, Huxley Building, Brighton, BN2 4GJ, UK.
- Brighton and Sussex Medical School, University of Sussex, Brighton, BN1 9PX, UK.
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22
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Jeng JY, Harasztosi C, Carlton A, Corns L, Marchetta P, Johnson SL, Goodyear RJ, Legan KP, Rüttiger L, Richardson GP, Marcotti W. MET currents and otoacoustic emissions from mice with a detached tectorial membrane indicate the extracellular matrix regulates Ca 2+ near stereocilia. J Physiol 2021; 599:2015-2036. [PMID: 33559882 PMCID: PMC7612128 DOI: 10.1113/jp280905] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 02/03/2021] [Indexed: 10/11/2023] Open
Abstract
KEY POINTS The aim was to determine whether detachment of the tectorial membrane (TM) from the organ of Corti in Tecta/Tectb-/- mice affects the biophysical properties of cochlear outer hair cells (OHCs). Tecta/Tectb-/- mice have highly elevated hearing thresholds, but OHCs mature normally. Mechanoelectrical transducer (MET) channel resting open probability (Po ) in mature OHC is ∼50% in endolymphatic [Ca2+ ], resulting in a large standing depolarizing MET current that would allow OHCs to act optimally as electromotile cochlear amplifiers. MET channel resting Po in vivo is also high in Tecta/Tectb-/- mice, indicating that the TM is unlikely to statically bias the hair bundles of OHCs. Distortion product otoacoustic emissions (DPOAEs), a readout of active, MET-dependent, non-linear cochlear amplification in OHCs, fail to exhibit long-lasting adaptation to repetitive stimulation in Tecta/Tectb-/- mice. We conclude that during prolonged, sound-induced stimulation of the cochlea the TM may determine the extracellular Ca2+ concentration near the OHC's MET channels. ABSTRACT The tectorial membrane (TM) is an acellular structure of the cochlea that is attached to the stereociliary bundles of the outer hair cells (OHCs), electromotile cells that amplify motion of the cochlear partition and sharpen its frequency selectivity. Although the TM is essential for hearing, its role is still not fully understood. In Tecta/Tectb-/- double knockout mice, in which the TM is not coupled to the OHC stereocilia, hearing sensitivity is considerably reduced compared with that of wild-type animals. In vivo, the OHC receptor potentials, assessed using cochlear microphonics, are symmetrical in both wild-type and Tecta/Tectb-/- mice, indicating that the TM does not bias the hair bundle resting position. The functional maturation of hair cells is also unaffected in Tecta/Tectb-/- mice, and the resting open probability of the mechanoelectrical transducer (MET) channel reaches values of ∼50% when the hair bundles of mature OHCs are bathed in an endolymphatic-like Ca2+ concentration (40 μM) in vitro. The resultant large MET current depolarizes OHCs to near -40 mV, a value that would allow optimal activation of the motor protein prestin and normal cochlear amplification. Although the set point of the OHC receptor potential transfer function in vivo may therefore be determined primarily by endolymphatic Ca2+ concentration, repetitive acoustic stimulation fails to produce adaptation of MET-dependent otoacoustic emissions in vivo in the Tecta/Tectb-/- mice. Therefore, the TM is likely to contribute to the regulation of Ca2+ levels around the stereocilia, and thus adaptation of the OHC MET channel during prolonged sound stimulation.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Csaba Harasztosi
- Department of Otolaryngology Head & Neck Surgery, THRC, University of Tübingen, 72076 Tübingen, Germany
| | - Adam Carlton
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Laura Corns
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Philine Marchetta
- Department of Otolaryngology Head & Neck Surgery, THRC, University of Tübingen, 72076 Tübingen, Germany
| | - Stuart L. Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | | | - Kevin P. Legan
- School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
| | - Lukas Rüttiger
- Department of Otolaryngology Head & Neck Surgery, THRC, University of Tübingen, 72076 Tübingen, Germany
| | - Guy P. Richardson
- School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
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23
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McGrath J, Tung CY, Liao X, Belyantseva IA, Roy P, Chakraborty O, Li J, Berbari NF, Faaborg-Andersen CC, Barzik M, Bird JE, Zhao B, Balakrishnan L, Friedman TB, Perrin BJ. Actin at stereocilia tips is regulated by mechanotransduction and ADF/cofilin. Curr Biol 2021; 31:1141-1153.e7. [PMID: 33400922 PMCID: PMC8793668 DOI: 10.1016/j.cub.2020.12.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 10/21/2020] [Accepted: 12/07/2020] [Indexed: 11/30/2022]
Abstract
Stereocilia on auditory sensory cells are actin-based protrusions that mechanotransduce sound into an electrical signal. These stereocilia are arranged into a bundle with three rows of increasing length to form a staircase-like morphology that is required for hearing. Stereocilia in the shorter rows, but not the tallest row, are mechanotransducing because they have force-sensitive channels localized at their tips. The onset of mechanotransduction during mouse postnatal development refines stereocilia length and width. However, it is unclear how actin is differentially regulated between stereocilia in the tallest row of the bundle and the shorter, mechanotransducing rows. Here, we show actin turnover is increased at the tips of mechanotransducing stereocilia during bundle maturation. Correspondingly, from birth to postnatal day 6, these stereocilia had increasing amounts of available actin barbed ends, where monomers can be added or lost readily, as compared with the non-mechanotransducing stereocilia in the tallest row. The increase in available barbed ends depended on both mechanotransduction and MYO15 or EPS8, which are required for the normal specification and elongation of the tallest row of stereocilia. We also found that loss of the F-actin-severing proteins ADF and cofilin-1 decreased barbed end availability at stereocilia tips. These proteins enriched at mechanotransducing stereocilia tips, and their localization was perturbed by the loss of mechanotransduction, MYO15, or EPS8. Finally, stereocilia lengths and widths were dysregulated in Adf and Cfl1 mutants. Together, these data show that actin is remodeled, likely by a severing mechanism, in response to mechanotransduction.
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Affiliation(s)
- Jamis McGrath
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Chun-Yu Tung
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Xiayi Liao
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Inna A Belyantseva
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Pallabi Roy
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Oisorjo Chakraborty
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Jinan Li
- Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, 1160 West Michigan Street, Indianapolis, IN 46202, USA
| | - Nicolas F Berbari
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Christian C Faaborg-Andersen
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Melanie Barzik
- Section on Sensory Cell Biology, National Institute on Deafness and Other Communication Disorders, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Jonathan E Bird
- Department of Pharmacology and Therapeutics, University of Florida, 1200 Newell Drive, Gainesville, FL 32610, USA
| | - Bo Zhao
- Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, 1160 West Michigan Street, Indianapolis, IN 46202, USA
| | - Lata Balakrishnan
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Thomas B Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Benjamin J Perrin
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA.
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24
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Loxhd1 Mutations Cause Mechanotransduction Defects in Cochlear Hair Cells. J Neurosci 2021; 41:3331-3343. [PMID: 33707295 PMCID: PMC8051682 DOI: 10.1523/jneurosci.0975-20.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 02/22/2021] [Accepted: 03/02/2021] [Indexed: 12/27/2022] Open
Abstract
Sound detection happens in the inner ear via the mechanical deflection of the hair bundle of cochlear hair cells. The hair bundle is an apical specialization consisting of actin-filled membrane protrusions (called stereocilia) connected by tip links (TLs) that transfer the deflection force to gate the mechanotransduction channels. Here, we identified the hearing loss-associated Loxhd1/DFNB77 gene as being required for the mechanotransduction process. Sound detection happens in the inner ear via the mechanical deflection of the hair bundle of cochlear hair cells. The hair bundle is an apical specialization consisting of actin-filled membrane protrusions (called stereocilia) connected by tip links (TLs) that transfer the deflection force to gate the mechanotransduction channels. Here, we identified the hearing loss-associated Loxhd1/DFNB77 gene as being required for the mechanotransduction process. LOXHD1 consists of 15 polycystin lipoxygenase α-toxin (PLAT) repeats, which in other proteins can bind lipids and proteins. LOXHD1 was distributed along the length of the stereocilia. Two LOXHD1 mouse models with mutations in the 10th PLAT repeat exhibited mechanotransduction defects (in both sexes). While mechanotransduction currents in mutant inner hair cells (IHCs) were similar to wild-type levels in the first postnatal week, they were severely affected by postnatal day 11. The onset of the mechanotransduction phenotype was consistent with the temporal progression of postnatal LOXHD1 expression/localization in the hair bundle. The mechanotransduction defect observed in Loxhd1-mutant IHCs was not accompanied by a morphologic defect of the hair bundle or a reduction in TL number. Using immunolocalization, we found that two proteins of the upper and lower TL protein complexes (Harmonin and LHFPL5) were maintained in the mutants, suggesting that the mechanotransduction machinery was present but not activatable. This work identified a novel LOXHD1-dependent step in hair bundle development that is critical for mechanotransduction in mature hair cells as well as for normal hearing function in mice and humans. SIGNIFICANCE STATEMENT Hair cells detect sound-induced forces via the hair bundle, which consists of membrane protrusions connected by tip links. The mechanotransduction machinery forms protein complexes at the tip-link ends. The current study showed that LOXHD1, a multirepeat protein responsible for hearing loss in humans and mice when mutated, was required for hair-cell mechanotransduction, but only after the first postnatal week. Using immunochemistry, we demonstrated that this defect was not caused by the mislocalization of the tip-link complex proteins Harmonin or LHFPL5, suggesting that the mechanotransduction protein complexes were maintained. This work identified a new step in hair bundle development, which is critical for both hair-cell mechanotransduction and hearing.
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25
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Lv J, Fu X, Li Y, Hong G, Li P, Lin J, Xun Y, Fang L, Weng W, Yue R, Li GL, Guan B, Li H, Huang Y, Chai R. Deletion of Kcnj16 in Mice Does Not Alter Auditory Function. Front Cell Dev Biol 2021; 9:630361. [PMID: 33693002 PMCID: PMC7937937 DOI: 10.3389/fcell.2021.630361] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 01/26/2021] [Indexed: 01/13/2023] Open
Abstract
Endolymphatic potential (EP) is the main driving force behind the sensory transduction of hearing, and K+ is the main charge carrier. Kir5.1 is a K+ transporter that plays a significant role in maintaining EP homeostasis, but the expression pattern and role of Kir5.1 (which is encoded by the Kcnj16 gene) in the mouse auditory system has remained unclear. In this study, we found that Kir5.1 was expressed in the mouse cochlea. We checked the inner ear morphology and measured auditory function in Kcnj16–/– mice and found that loss of Kcnj16 did not appear to affect the development of hair cells. There was no significant difference in auditory function between Kcnj16–/– mice and wild-type littermates, although the expression of Kcnma1, Kcnq4, and Kcne1 were significantly decreased in the Kcnj16–/– mice. Additionally, no significant differences were found in the number or distribution of ribbon synapses between the Kcnj16–/– and wild-type mice. In summary, our results suggest that the Kcnj16 gene is not essential for auditory function in mice.
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Affiliation(s)
- Jun Lv
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Xiaolong Fu
- State Key Laboratory of Bioelectronics, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Yige Li
- State Key Laboratory of Bioelectronics, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Guodong Hong
- State Key Laboratory of Bioelectronics, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China
| | - Peipei Li
- School of Life Sciences and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
| | - Jing Lin
- Waksman Institute, Rutgers, The State University of New Jersey, Piscataway, NJ, United States
| | - Youfang Xun
- Department of Otolaryngology, Head and Neck Surgery, Xiangya School of Medicine, Central South University, Changsha, China.,Department of Otolaryngology, Head and Neck Surgery, Clinical Medical College of Yangzhou University, Yangzhou, China
| | - Lucheng Fang
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Weibin Weng
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Rongyu Yue
- Department of Otolaryngology-Head and Neck Surgery, Provincial Hospital Affiliated to Shandong University, Jinan, China
| | - Geng-Lin Li
- Department of Otorhinolaryngology and ENT Institute, Eye and ENT Hospital, Fudan University, Shanghai, China
| | - Bing Guan
- Department of Otolaryngology, Head and Neck Surgery, Clinical Medical College of Yangzhou University, Yangzhou, China
| | - He Li
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China
| | - Yideng Huang
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.,Department of Otolaryngology-Head and Neck Surgery, Hwa Mei Hospital, University of Chinese Academy of Sciences, Ningbo, China
| | - Renjie Chai
- Department of Otolaryngology-Head and Neck Surgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.,State Key Laboratory of Bioelectronics, School of Life Sciences and Technology, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing, China.,Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, China.,Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
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26
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Carlton AJ, Halford J, Underhill A, Jeng J, Avenarius MR, Gilbert ML, Ceriani F, Ebisine K, Brown SDM, Bowl MR, Barr‐Gillespie PG, Marcotti W. Loss of Baiap2l2 destabilizes the transducing stereocilia of cochlear hair cells and leads to deafness. J Physiol 2021; 599:1173-1198. [PMID: 33151556 PMCID: PMC7898316 DOI: 10.1113/jp280670] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 10/27/2020] [Indexed: 12/17/2022] Open
Abstract
KEY POINTS Mechanoelectrical transduction at auditory hair cells requires highly specialized stereociliary bundles that project from their apical surface, forming a characteristic graded 'staircase' structure. The morphogenesis and maintenance of these stereociliary bundles is a tightly regulated process requiring the involvement of several actin-binding proteins, many of which are still unidentified. We identify a new stereociliary protein, the I-BAR protein BAIAP2L2, which localizes to the tips of the shorter transducing stereocilia in both inner and outer hair cells (IHCs and OHCs). We find that Baiap2l2 deficient mice lose their second and third rows of stereocilia, their mechanoelectrical transducer current, and develop progressive hearing loss, becoming deaf by 8 months of age. We demonstrate that BAIAP2L2 localization to stereocilia tips is dependent on the motor protein MYO15A and its cargo EPS8. We propose that BAIAP2L2 is a new key protein required for the maintenance of the transducing stereocilia in mature cochlear hair cells. ABSTRACT The transduction of sound waves into electrical signals depends upon mechanosensitive stereociliary bundles that project from the apical surface of hair cells within the cochlea. The height and width of these actin-based stereocilia is tightly regulated throughout life to establish and maintain their characteristic staircase-like structure, which is essential for normal mechanoelectrical transduction. Here, we show that BAIAP2L2, a member of the I-BAR protein family, is a newly identified hair bundle protein that is localized to the tips of the shorter rows of transducing stereocilia in mouse cochlear hair cells. BAIAP2L2 was detected by immunohistochemistry from postnatal day 2.5 (P2.5) throughout adulthood. In Baiap2l2 deficient mice, outer hair cells (OHCs), but not inner hair cells (IHCs), began to lose their third row of stereocilia and showed a reduction in the size of the mechanoelectrical transducer current from just after P9. Over the following post-hearing weeks, the ordered staircase structure of the bundle progressively deteriorates, such that, by 8 months of age, both OHCs and IHCs of Baiap2l2 deficient mice have lost most of the second and third rows of stereocilia and become deaf. We also found that BAIAP2L2 interacts with other key stereociliary proteins involved in normal hair bundle morphogenesis, such as CDC42, RAC1, EPS8 and ESPNL. Furthermore, we show that BAIAP2L2 localization to the stereocilia tips depends on the motor protein MYO15A and its cargo EPS8. We propose that BAIAP2L2 is key to maintenance of the normal actin structure of the transducing stereocilia in mature mouse cochlear hair cells.
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Affiliation(s)
- Adam J. Carlton
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
| | - Julia Halford
- Oregon Hearing Research Center & Vollum InstituteOregon Health & Science UniversityPortlandORUSA
| | - Anna Underhill
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
| | - Jing‐Yi Jeng
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
| | - Matthew R. Avenarius
- Oregon Hearing Research Center & Vollum InstituteOregon Health & Science UniversityPortlandORUSA
- Present address: Department of Pathology Wexner Medical CenterThe Ohio State UniversityColumbusOHUSA
| | - Merle L. Gilbert
- Oregon Hearing Research Center & Vollum InstituteOregon Health & Science UniversityPortlandORUSA
- Present address: US Army Medical Department Activity‐KoreaCamp HumphreysRepublic of Korea
| | - Federico Ceriani
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
| | | | - Steve D. M. Brown
- Mammalian Genetics UnitMRC Harwell InstituteHarwell CampusOxfordshireUK
| | - Michael R. Bowl
- Mammalian Genetics UnitMRC Harwell InstituteHarwell CampusOxfordshireUK
- Present address: UCL Ear InstituteUniversity College LondonLondonUK
| | - Peter G. Barr‐Gillespie
- Oregon Hearing Research Center & Vollum InstituteOregon Health & Science UniversityPortlandORUSA
- Oregon Hearing Research CenterOregon Health & Science UniversityPortlandORUSA
| | - Walter Marcotti
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
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27
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Jeng JY, Carlton A, Johnson SL, Brown SDM, Holley MC, Bowl MR, Marcotti W. Biophysical and morphological changes in inner hair cells and their efferent innervation in the ageing mouse cochlea. J Physiol 2021; 599:269-287. [PMID: 33179774 PMCID: PMC7612127 DOI: 10.1113/jp280256] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 10/01/2020] [Indexed: 09/18/2023] Open
Abstract
KEY POINTS Age-related hearing loss is a progressive hearing loss involving environmental and genetic factors, leading to a decrease in hearing sensitivity, threshold and speech discrimination. We compared age-related changes in inner hair cells (IHCs) between four mouse strains with different levels of progressive hearing loss. The surface area of apical coil IHCs (9-12 kHz cochlear region) decreases by about 30-40% with age. The number of BK channels progressively decreases with age in the IHCs from most mouse strains, but the basolateral membrane current profile remains unchanged. The mechanoelectrical transducer current is smaller in mice harbouring the hypomorphic Cdh23 allele Cdh23ahl (C57BL/6J; C57BL/6NTac), but not in Cdh23-repaired mice (C57BL/6NTacCdh23+ ), indicating that it could contribute to the different progression of hearing loss among mouse strains. The degree of efferent rewiring onto aged IHCs, most likely coming from the lateral olivocochlea fibres, was correlated with hearing loss in the different mouse strains. ABSTRACT Inner hair cells (IHCs) are the primary sensory receptors of the mammalian cochlea, transducing acoustic information into electrical signals that are relayed to the afferent neurons. Functional changes in IHCs are a potential cause of age-related hearing loss. Here, we have investigated the functional characteristics of IHCs from early-onset hearing loss mice harbouring the allele Cdh23ahl (C57BL/6J and C57BL/6NTac), from late-onset hearing loss mice (C3H/HeJ), and from mice corrected for the Cdh23ahl mutation (C57BL/6NTacCdh23+ ) with an intermediate hearing phenotype. There was no significant loss of IHCs in the 9-12 kHz cochlear region up to at least 15 months of age, but their surface area decreased progressively by 30-40% starting from ∼6 months of age. Although the size of the BK current decreased with age, IHCs retained a normal KCNQ4 current and resting membrane potential. These basolateral membrane changes were most severe for C57BL/6J and C57BL/6NTac, less so for C57BL/6NTacCdh23+ and minimal or absent in C3H/HeJ mice. We also found that lateral olivocochlear (LOC) efferent fibres re-form functional axon-somatic connections with aged IHCs, but this was seen only sporadically in C3H/HeJ mice. The efferent post-synaptic SK2 channels appear prior to the establishment of the efferent contacts, suggesting that IHCs may play a direct role in re-establishing the LOC-IHC synapses. Finally, we showed that the size of the mechanoelectrical transducer (MET) current from IHCs decreased significantly with age in mice harbouring the Cdh23ahl allele but not in C57BL/6NTacCdh23+ mice, indicating that the MET apparatus directly contributes to the progression of age-related hearing loss.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Adam Carlton
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Stuart L. Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Steve D. M. Brown
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, OX11 0RD, UK
| | - Matthew C. Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Michael R. Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, OX11 0RD, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
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28
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29
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Martelletti E, Ingham NJ, Houston O, Pass JC, Chen J, Marcotti W, Steel KP. Synaptojanin2 Mutation Causes Progressive High-frequency Hearing Loss in Mice. Front Cell Neurosci 2020; 14:561857. [PMID: 33100973 PMCID: PMC7546894 DOI: 10.3389/fncel.2020.561857] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 08/14/2020] [Indexed: 12/04/2022] Open
Abstract
Progressive hearing loss is very common in the human population but we know little about the underlying molecular mechanisms. Synaptojanin2 (Synj2) has been reported to be involved, as a mouse mutation led to a progressive increase in auditory thresholds with age. Synaptojanin2 is a phosphatidylinositol (PI) phosphatase that removes the five-position phosphates from phosphoinositides, such as PIP2 and PIP3, and is a key enzyme in clathrin-mediated endocytosis. To investigate the mechanisms underlying progressive hearing loss, we have studied a different mutation of mouse Synj2 to look for any evidence of involvement of vesicle trafficking particularly affecting the synapses of sensory hair cells. Auditory brainstem responses (ABR) developed normally at first but started to decline between 3 and 4 weeks of age in Synj2tm1b mutants. At 6 weeks old, some evidence of outer hair cell (OHC) stereocilia fusion and degeneration was observed, but this was only seen in the extreme basal turn so cannot explain the raised ABR thresholds that correspond to more apical regions of the cochlear duct. We found no evidence of any defect in inner hair cell (IHC) exocytosis or endocytosis using single hair cell recordings, nor any sign of hair cell synaptic abnormalities. Endocochlear potentials (EP) were normal. The mechanism underlying progressive hearing loss in these mutants remains elusive, but our findings of raised distortion product otoacoustic emission (DPOAE) thresholds and signs of OHC degeneration both suggest an OHC origin for the hearing loss. Synaptojanin2 is not required for normal development of hearing but it is important for its maintenance.
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Affiliation(s)
- Elisa Martelletti
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Neil J Ingham
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Oliver Houston
- Department of Biomedical Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Johanna C Pass
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Jing Chen
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Walter Marcotti
- Department of Biomedical Sciences, University of Sheffield, Sheffield, United Kingdom.,Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Karen P Steel
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
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30
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Whatley M, Francis A, Ng ZY, Khoh XE, Atlas MD, Dilley RJ, Wong EYM. Usher Syndrome: Genetics and Molecular Links of Hearing Loss and Directions for Therapy. Front Genet 2020; 11:565216. [PMID: 33193648 PMCID: PMC7642844 DOI: 10.3389/fgene.2020.565216] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 09/21/2020] [Indexed: 12/19/2022] Open
Abstract
Usher syndrome (USH) is an autosomal recessive (AR) disorder that permanently and severely affects the senses of hearing, vision, and balance. Three clinically distinct types of USH have been identified, decreasing in severity from Type 1 to 3, with symptoms of sensorineural hearing loss (SNHL), retinitis pigmentosa (RP), and vestibular dysfunction. There are currently nine confirmed and two suspected USH-causative genes, and a further three candidate loci have been mapped. The proteins encoded by these genes form complexes that play critical roles in the development and maintenance of cellular structures within the inner ear and retina, which have minimal capacity for repair or regeneration. In the cochlea, stereocilia are located on the apical surface of inner ear hair cells (HC) and are responsible for transducing mechanical stimuli from sound pressure waves into chemical signals. These signals are then detected by the auditory nerve fibers, transmitted to the brain and interpreted as sound. Disease-causing mutations in USH genes can destabilize the tip links that bind the stereocilia to each other, and cause defects in protein trafficking and stereocilia bundle morphology, thereby inhibiting mechanosensory transduction. This review summarizes the current knowledge on Usher syndrome with a particular emphasis on mutations in USH genes, USH protein structures, and functional analyses in animal models. Currently, there is no cure for USH. However, the genetic therapies that are rapidly developing will benefit from this compilation of detailed genetic information to identify the most effective strategies for restoring functional USH proteins.
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Affiliation(s)
- Meg Whatley
- Ear Science Institute Australia, Nedlands, WA, Australia
| | - Abbie Francis
- Ear Science Institute Australia, Nedlands, WA, Australia
- Emergency Medicine, The University of Western Australia, Nedlands, WA, Australia
| | - Zi Ying Ng
- Ear Science Institute Australia, Nedlands, WA, Australia
| | - Xin Ee Khoh
- Ear Science Institute Australia, Nedlands, WA, Australia
- School of Human Sciences, The University of Western Australia, Nedlands, WA, Australia
| | - Marcus D. Atlas
- Ear Science Institute Australia, Nedlands, WA, Australia
- Ear Sciences Centre, The University of Western Australia, Nedlands, WA, Australia
| | - Rodney J. Dilley
- Ear Science Institute Australia, Nedlands, WA, Australia
- Ear Sciences Centre, The University of Western Australia, Nedlands, WA, Australia
- Centre for Cell Therapy and Regenerative Medicine, The University of Western Australia, Perth, WA, Australia
| | - Elaine Y. M. Wong
- Ear Science Institute Australia, Nedlands, WA, Australia
- Ear Sciences Centre, The University of Western Australia, Nedlands, WA, Australia
- School of Pharmacy and Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley, WA, Australia
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Jovanovic S, Milenkovic I. Purinergic Modulation of Activity in the Developing Auditory Pathway. Neurosci Bull 2020; 36:1285-1298. [PMID: 33040238 DOI: 10.1007/s12264-020-00586-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 09/10/2020] [Indexed: 12/11/2022] Open
Abstract
Purinergic P2 receptors, activated by endogenous ATP, are prominently expressed on neuronal and non-neuronal cells during development of the auditory periphery and central auditory neurons. In the mature cochlea, extracellular ATP contributes to ion homeostasis, and has a protective function against noise exposure. Here, we focus on the modulation of activity by extracellular ATP during early postnatal development of the lower auditory pathway. In mammals, spontaneous patterned activity is conveyed along afferent auditory pathways before the onset of acoustically evoked signal processing. During this critical developmental period, inner hair cells fire bursts of action potentials that are believed to provide a developmental code for synaptic maturation and refinement of auditory circuits, thereby establishing a precise tonotopic organization. Endogenous ATP-release triggers such patterned activity by raising the extracellular K+ concentration and contributes to firing by increasing the excitability of auditory nerve fibers, spiral ganglion neurons, and specific neuron types within the auditory brainstem, through the activation of diverse P2 receptors. We review recent studies that provide new models on the contribution of purinergic signaling to early development of the afferent auditory pathway. Further, we discuss potential future directions of purinergic research in the auditory system.
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Affiliation(s)
- Sasa Jovanovic
- School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany
| | - Ivan Milenkovic
- School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany.
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32
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Jeng JY, Johnson SL, Carlton AJ, DeTomasi L, Goodyear R, DeFaveri F, Furness DN, Wells S, Brown SDM, Holley MC, Richardson GP, Mustapha M, Bowl MR, Marcotti W. Age-related changes in the biophysical and morphological characteristics of mouse cochlear outer hair cells. J Physiol 2020; 598:3891-3910. [PMID: 32608086 PMCID: PMC7612122 DOI: 10.1113/jp279795] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 06/25/2020] [Indexed: 09/01/2023] Open
Abstract
KEY POINTS Age-related hearing loss (ARHL) is a very heterogeneous disease, resulting from cellular senescence, genetic predisposition and environmental factors (e.g. noise exposure). Currently, we know very little about age-related changes occurring in the auditory sensory cells, including those associated with the outer hair cells (OHCs). Using different mouse strains, we show that OHCs undergo several morphological and biophysical changes in the ageing cochlea. Ageing OHCs also exhibited the progressive loss of afferent and efferent synapses. We also provide evidence that the size of the mechanoelectrical transducer current is reduced in ageing OHCs, highlighting its possible contribution in cochlear ageing. ABSTRACT Outer hair cells (OHCs) are electromotile sensory receptors that provide sound amplification within the mammalian cochlea. Although OHCs appear susceptible to ageing, the progression of the pathophysiological changes in these cells is still poorly understood. By using mouse strains with a different progression of hearing loss (C57BL/6J, C57BL/6NTac, C57BL/6NTacCdh23+ , C3H/HeJ), we have identified morphological, physiological and molecular changes in ageing OHCs (9-12 kHz cochlear region). We show that by 6 months of age, OHCs from all strains underwent a reduction in surface area, which was not a sign of degeneration. Although the ageing OHCs retained a normal basolateral membrane protein profile, they showed a reduction in the size of the K+ current and non-linear capacitance, a readout of prestin-dependent electromotility. Despite these changes, OHCs have a normal Vm and retain the ability to amplify sound, as distortion product otoacoustic emission thresholds were not affected in aged, good-hearing mice (C3H/HeJ, C57BL/6NTacCdh23+ ). The loss of afferent synapses was present in all strains at 15 months. The number of efferent synapses per OHCs, defined as postsynaptic SK2 puncta, was reduced in aged OHCs of all strains apart from C3H mice. Several of the identified changes occurred in aged OHCs from all mouse strains, thus representing a general trait in the pathophysiological progression of age-related hearing loss, possibly aimed at preserving functionality. We have also shown that the mechanoelectrical transduction (MET) current from OHCs of mice harbouring the Cdh23ahl allele is reduced with age, highlighting the possibility that changes in the MET apparatus could play a role in cochlear ageing.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Stuart L. Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Adam J Carlton
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Lara DeTomasi
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Richard Goodyear
- School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
| | - Francesca DeFaveri
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | | | - Sara Wells
- Mary Lyon Centre, MRC Harwell Institute, Oxfordshire, UK
| | | | - Matthew C. Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Guy P. Richardson
- School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
| | - Mirna Mustapha
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Michael R. Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
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33
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Zhang Y, Glowatzki E, Roux I, Fuchs PA. Nicotine evoked efferent transmitter release onto immature cochlear inner hair cells. J Neurophysiol 2020; 124:1377-1387. [PMID: 32845208 DOI: 10.1152/jn.00097.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Olivocochlear neurons make temporary cholinergic synapses on inner hair cells of the rodent cochlea in the first 2 to 3 wk after birth. Repetitive stimulation of these efferent neurons causes facilitation of evoked release and increased spontaneous release that continues for seconds to minutes. Presynaptic nicotinic acetylcholine receptors (nAChRs) are known to modulate neurotransmitter release from brain neurons. The present study explores the hypothesis that presynaptic nAChRs help to increase spontaneous release from efferent terminals on cochlear hair cells. Direct application of nicotine (which does not activate the hair cells' α9α10-containing nAChRs) produces sustained efferent transmitter release, implicating presynaptic nAChRs in this response. The effect of nicotine was reduced by application of ryanodine that reduces release of calcium from intraterminal stores.NEW & NOTEWORTHY Sensory organs exhibit spontaneous activity before the onset of response to external stimuli. Such activity in the cochlea is subject to modulation by cholinergic efferent neurons that directly inhibit sensory hair cells (inner hair cells). Those efferent neurons are themselves subject to various modulatory mechanisms. One such mechanism is positive feedback by released acetylcholine onto presynaptic nicotinic acetylcholine receptors causing further release of acetylcholine.
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Affiliation(s)
- Y Zhang
- The Center for Hearing and Balance, Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - E Glowatzki
- The Center for Hearing and Balance, Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - I Roux
- The Center for Hearing and Balance, Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,Otolaryngology Branch, National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health, Porter Neuroscience Research Center, Bethesda, Maryland
| | - P A Fuchs
- The Center for Hearing and Balance, Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland
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Jeng JY, Ceriani F, Olt J, Brown SDM, Holley MC, Bowl MR, Johnson SL, Marcotti W. Pathophysiological changes in inner hair cell ribbon synapses in the ageing mammalian cochlea. J Physiol 2020; 598:4339-4355. [PMID: 32710572 DOI: 10.1113/jp280018] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 07/24/2020] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS Age-related hearing loss (ARHL) is associated with the loss of inner hair cell (IHC) ribbon synapses, lower hearing sensitivity and decreased ability to understand speech, especially in a noisy environment. Little is known about the age-related physiological and morphological changes that occur at ribbon synapses. We show that the differing degrees of ARHL in four selected mouse stains is correlated with the loss of ribbon synapses, being most severe for the strains C57BL/6NTac and C57BL/6J, less so for C57BL/6NTacCdh23+ -Repaired and lowest for C3H/HeJ. Despite the loss of ribbon synapses with age, the volume of the remaining ribbons increased and the size and kinetics of Ca2+ -dependent exocytosis in IHCs was unaffected, indicating the presence of a previously unknown degree of functional compensation at ribbon synapses. Although the age-related morphological changes at IHC ribbon synapses contribute to the different progression of ARHL, without the observed functional compensation hearing loss could be greater. ABSTRACT Mammalian cochlear inner hair cells (IHCs) are specialized sensory receptors able to provide dynamic coding of sound signals. This ability is largely conferred by their ribbon synapses, which tether a large number of vesicles at the IHC's presynaptic active zones, allowing high rates of sustained synaptic transmission onto the afferent fibres. How the physiological and morphological properties of ribbon synapses change with age remains largely unknown. Here, we have investigated the biophysical and morphological properties of IHC ribbon synapses in the ageing cochlea (9-12 kHz region) of four mouse strains commonly used in hearing research: early-onset progressive hearing loss (C57BL/6J and C57BL/6NTac) and 'good hearing' strains (C57BL/6NTacCdh23+ and C3H/HeJ). We found that with age, both modiolar and pillar sides of the IHC exhibited a loss of ribbons, but there was an increased volume of those that remained. These morphological changes, which only occurred after 6 months of age, were correlated with the level of hearing loss in the different mouse strains, being most severe for C57BL/6NTac and C57BL/6J, less so for C57BL/6NTacCdh23+ and absent for C3H/HeJ strains. Despite the age-related reduction in ribbon number in three of the four strains, the size and kinetics of Ca2+ -dependent exocytosis, as well as the replenishment of synaptic vesicles, in IHCs was not affected. The degree of vesicle release at the fewer, but larger, individual remaining ribbon synapses colocalized with the post-synaptic afferent terminals is likely to increase, indicating the presence of a previously unknown degree of functional compensation in the ageing mouse cochlea.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK.,Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK.,Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Jennifer Olt
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Steve D M Brown
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, UK
| | - Matthew C Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Michael R Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, UK
| | - Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK.,Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK.,Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
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35
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Li S, Mecca A, Kim J, Caprara GA, Wagner EL, Du TT, Petrov L, Xu W, Cui R, Rebustini IT, Kachar B, Peng AW, Shin JB. Myosin-VIIa is expressed in multiple isoforms and essential for tensioning the hair cell mechanotransduction complex. Nat Commun 2020; 11:2066. [PMID: 32350269 PMCID: PMC7190839 DOI: 10.1038/s41467-020-15936-z] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 04/01/2020] [Indexed: 11/09/2022] Open
Abstract
Mutations in myosin-VIIa (MYO7A) cause Usher syndrome type 1, characterized by combined deafness and blindness. MYO7A is proposed to function as a motor that tensions the hair cell mechanotransduction (MET) complex, but conclusive evidence is lacking. Here we report that multiple MYO7A isoforms are expressed in the mouse cochlea. In mice with a specific deletion of the canonical isoform (Myo7a-ΔC mouse), MYO7A is severely diminished in inner hair cells (IHCs), while expression in outer hair cells is affected tonotopically. IHCs of Myo7a-ΔC mice undergo normal development, but exhibit reduced resting open probability and slowed onset of MET currents, consistent with MYO7A's proposed role in tensioning the tip link. Mature IHCs of Myo7a-ΔC mice degenerate over time, giving rise to progressive hearing loss. Taken together, our study reveals an unexpected isoform diversity of MYO7A expression in the cochlea and highlights MYO7A's essential role in tensioning the hair cell MET complex.
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Affiliation(s)
- Sihan Li
- Department of Neuroscience, University of Virginia, Charlottesville, VA, USA.,Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA
| | - Andrew Mecca
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Jeewoo Kim
- Department of Neuroscience, University of Virginia, Charlottesville, VA, USA
| | - Giusy A Caprara
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Elizabeth L Wagner
- Department of Neuroscience, University of Virginia, Charlottesville, VA, USA.,Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA
| | - Ting-Ting Du
- Department of Neuroscience, University of Virginia, Charlottesville, VA, USA
| | - Leonid Petrov
- Department of Mathematics, University of Virginia, Charlottesville, VA, USA
| | - Wenhao Xu
- Genetically Engineered Murine Model (GEMM) Core, University of Virginia, Charlottesville, VA, USA
| | - Runjia Cui
- National Institute for Deafness and Communications Disorders, National Institute of Health, Bethesda, MD, USA
| | - Ivan T Rebustini
- National Institute for Deafness and Communications Disorders, National Institute of Health, Bethesda, MD, USA
| | - Bechara Kachar
- National Institute for Deafness and Communications Disorders, National Institute of Health, Bethesda, MD, USA
| | - Anthony W Peng
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
| | - Jung-Bum Shin
- Department of Neuroscience, University of Virginia, Charlottesville, VA, USA. .,Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA.
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36
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Friedman TB, Belyantseva IA, Frolenkov GI. Myosins and Hearing. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1239:317-330. [DOI: 10.1007/978-3-030-38062-5_13] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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37
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Jeng JY, Ceriani F, Hendry A, Johnson SL, Yen P, Simmons DD, Kros CJ, Marcotti W. Hair cell maturation is differentially regulated along the tonotopic axis of the mammalian cochlea. J Physiol 2019; 598:151-170. [PMID: 31661723 PMCID: PMC6972525 DOI: 10.1113/jp279012] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 10/24/2019] [Indexed: 12/15/2022] Open
Abstract
Key points Outer hair cells (OHCs) enhance the sensitivity and the frequency tuning of the mammalian cochlea. Similar to the primary sensory receptor, the inner hair cells (IHCs), the mature functional characteristics of OHCs are acquired before hearing onset. We found that OHCs, like IHCs, fire spontaneous Ca2+‐induced action potentials (APs) during immature stages of development, which are driven by CaV1.3 Ca2+ channels. We also showed that the development of low‐ and high‐frequency hair cells is differentially regulated during pre‐hearing stages, with the former cells being more strongly dependent on experience‐independent Ca2+ action potential activity.
Abstract Sound amplification within the mammalian cochlea depends upon specialized hair cells, the outer hair cells (OHCs), which possess both sensory and motile capabilities. In various altricial rodents, OHCs become functionally competent from around postnatal day 7 (P7), before the primary sensory inner hair cells (IHCs), which become competent at about the onset of hearing (P12). The mechanisms responsible for the maturation of OHCs and their synaptic specialization remain poorly understood. We report that spontaneous Ca2+ activity in the immature cochlea, which is generated by CaV1.3 Ca2+ channels, differentially regulates the maturation of hair cells along the cochlea. Under near‐physiological recording conditions we found that, similar to IHCs, immature OHCs elicited spontaneous Ca2+ action potentials (APs), but only during the first few postnatal days. Genetic ablation of these APs in vivo, using CaV1.3−/− mice, prevented the normal developmental acquisition of mature‐like basolateral membrane currents in low‐frequency (apical) hair cells, such as IK,n (carried by KCNQ4 channels), ISK2 and IACh (α9α10nAChRs) in OHCs and IK,n and IK,f (BK channels) in IHCs. Electromotility and prestin expression in OHCs were normal in CaV1.3−/− mice. The maturation of high‐frequency (basal) hair cells was also affected in CaV1.3−/− mice, but to a much lesser extent than apical cells. However, a characteristic feature in CaV1.3−/− mice was the reduced hair cell size irrespective of their cochlear location. We conclude that the development of low‐ and high‐frequency hair cells is differentially regulated during development, with apical cells being more strongly dependent on experience‐independent Ca2+ APs. Outer hair cells (OHCs) enhance the sensitivity and the frequency tuning of the mammalian cochlea. Similar to the primary sensory receptor, the inner hair cells (IHCs), the mature functional characteristics of OHCs are acquired before hearing onset. We found that OHCs, like IHCs, fire spontaneous Ca2+‐induced action potentials (APs) during immature stages of development, which are driven by CaV1.3 Ca2+ channels. We also showed that the development of low‐ and high‐frequency hair cells is differentially regulated during pre‐hearing stages, with the former cells being more strongly dependent on experience‐independent Ca2+ action potential activity.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Aenea Hendry
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Piece Yen
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | | | - Corné J Kros
- School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
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38
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Johnson SL, Safieddine S, Mustapha M, Marcotti W. Hair Cell Afferent Synapses: Function and Dysfunction. Cold Spring Harb Perspect Med 2019; 9:a033175. [PMID: 30617058 PMCID: PMC6886459 DOI: 10.1101/cshperspect.a033175] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To provide a meaningful representation of the auditory landscape, mammalian cochlear hair cells are optimized to detect sounds over an incredibly broad range of frequencies and intensities with unparalleled accuracy. This ability is largely conferred by specialized ribbon synapses that continuously transmit acoustic information with high fidelity and sub-millisecond precision to the afferent dendrites of the spiral ganglion neurons. To achieve this extraordinary task, ribbon synapses employ a unique combination of molecules and mechanisms that are tailored to sounds of different frequencies. Here we review the current understanding of how the hair cell's presynaptic machinery and its postsynaptic afferent connections are formed, how they mature, and how their function is adapted for an accurate perception of sound.
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Affiliation(s)
- Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Saaid Safieddine
- UMRS 1120, Institut Pasteur, Paris, France
- Sorbonne Universités, UPMC Université Paris 06, Complexité du Vivant, Paris, France
| | - Mirna Mustapha
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California 94035
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
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39
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The Development of Cooperative Channels Explains the Maturation of Hair Cell's Mechanotransduction. Biophys J 2019; 117:1536-1548. [PMID: 31585704 PMCID: PMC6817549 DOI: 10.1016/j.bpj.2019.08.042] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/20/2019] [Accepted: 08/28/2019] [Indexed: 11/29/2022] Open
Abstract
Hearing relies on the conversion of mechanical stimuli into electrical signals. In vertebrates, this process of mechanoelectrical transduction (MET) is performed by specialized receptors of the inner ear, the hair cells. Each hair cell is crowned by a hair bundle, a cluster of microvilli that pivot in response to sound vibrations, causing the opening and closing of mechanosensitive ion channels. Mechanical forces are projected onto the channels by molecular springs called tip links. Each tip link is thought to connect to a small number of MET channels that gate cooperatively and operate as a single transduction unit. Pushing the hair bundle in the excitatory direction opens the channels, after which they rapidly reclose in a process called fast adaptation. It has been experimentally observed that the hair cell’s biophysical properties mature gradually during postnatal development: the maximal transduction current increases, sensitivity sharpens, transduction occurs at smaller hair-bundle displacements, and adaptation becomes faster. Similar observations have been reported during tip-link regeneration after acoustic damage. Moreover, when measured at intermediate developmental stages, the kinetics of fast adaptation varies in a given cell, depending on the magnitude of the imposed displacement. The mechanisms underlying these seemingly disparate observations have so far remained elusive. Here, we show that these phenomena can all be explained by the progressive addition of MET channels of constant properties, which populate the hair bundle first as isolated entities and then progressively as clusters of more sensitive, cooperative MET channels. As the proposed mechanism relies on the difference in biophysical properties between isolated and clustered channels, this work highlights the importance of cooperative interactions between mechanosensitive ion channels for hearing.
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40
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Dunbar LA, Patni P, Aguilar C, Mburu P, Corns L, Wells HRR, Delmaghani S, Parker A, Johnson S, Williams D, Esapa CT, Simon MM, Chessum L, Newton S, Dorning J, Jeyarajan P, Morse S, Lelli A, Codner GF, Peineau T, Gopal SR, Alagramam KN, Hertzano R, Dulon D, Wells S, Williams FM, Petit C, Dawson SJ, Brown SDM, Marcotti W, El‐Amraoui A, Bowl MR. Clarin-2 is essential for hearing by maintaining stereocilia integrity and function. EMBO Mol Med 2019; 11:e10288. [PMID: 31448880 PMCID: PMC6728604 DOI: 10.15252/emmm.201910288] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 07/23/2019] [Accepted: 07/26/2019] [Indexed: 11/21/2022] Open
Abstract
Hearing relies on mechanically gated ion channels present in the actin-rich stereocilia bundles at the apical surface of cochlear hair cells. Our knowledge of the mechanisms underlying the formation and maintenance of the sound-receptive structure is limited. Utilizing a large-scale forward genetic screen in mice, genome mapping and gene complementation tests, we identified Clrn2 as a new deafness gene. The Clrn2clarinet/clarinet mice (p.Trp4* mutation) exhibit a progressive, early-onset hearing loss, with no overt retinal deficits. Utilizing data from the UK Biobank study, we could show that CLRN2 is involved in human non-syndromic progressive hearing loss. Our in-depth morphological, molecular and functional investigations establish that while it is not required for initial formation of cochlear sensory hair cell stereocilia bundles, clarin-2 is critical for maintaining normal bundle integrity and functioning. In the differentiating hair bundles, lack of clarin-2 leads to loss of mechano-electrical transduction, followed by selective progressive loss of the transducing stereocilia. Together, our findings demonstrate a key role for clarin-2 in mammalian hearing, providing insights into the interplay between mechano-electrical transduction and stereocilia maintenance.
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Affiliation(s)
- Lucy A Dunbar
- Mammalian Genetics UnitMRC Harwell InstituteHarwellUK
| | - Pranav Patni
- Déficits Sensoriels ProgressifsInstitut PasteurINSERM UMR‐S 1120Sorbonne UniversitésParisFrance
| | | | | | - Laura Corns
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
| | - Helena RR Wells
- Department of Twin Research & Genetic EpidemiologyKing's College LondonLondonUK
| | - Sedigheh Delmaghani
- Déficits Sensoriels ProgressifsInstitut PasteurINSERM UMR‐S 1120Sorbonne UniversitésParisFrance
| | - Andrew Parker
- Mammalian Genetics UnitMRC Harwell InstituteHarwellUK
| | - Stuart Johnson
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
| | | | | | | | | | | | | | | | - Susan Morse
- Mammalian Genetics UnitMRC Harwell InstituteHarwellUK
| | - Andrea Lelli
- Génétique et Physiologie de l'AuditionInstitut PasteurINSERM UMR‐S 1120Collège de FranceSorbonne UniversitésParisFrance
| | | | - Thibault Peineau
- Laboratoire de Neurophysiologie de la Synapse AuditiveUniversité de BordeauxBordeauxFrance
| | - Suhasini R Gopal
- Department of Otolaryngology – Head and Neck SurgeryUniversity Hospitals Cleveland Medical CenterCase Western Reserve UniversityClevelandOHUSA
| | - Kumar N Alagramam
- Department of Otolaryngology – Head and Neck SurgeryUniversity Hospitals Cleveland Medical CenterCase Western Reserve UniversityClevelandOHUSA
| | - Ronna Hertzano
- Department of Otorhinolaryngology Head and Neck Surgery, Anatomy and Neurobiology and Institute for Genome SciencesUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - Didier Dulon
- Laboratoire de Neurophysiologie de la Synapse AuditiveUniversité de BordeauxBordeauxFrance
| | - Sara Wells
- Mary Lyon CentreMRC Harwell InstituteHarwellUK
| | - Frances M Williams
- Department of Twin Research & Genetic EpidemiologyKing's College LondonLondonUK
| | - Christine Petit
- Génétique et Physiologie de l'AuditionInstitut PasteurINSERM UMR‐S 1120Collège de FranceSorbonne UniversitésParisFrance
| | | | | | - Walter Marcotti
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
| | - Aziz El‐Amraoui
- Déficits Sensoriels ProgressifsInstitut PasteurINSERM UMR‐S 1120Sorbonne UniversitésParisFrance
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41
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Bardhan T, Jeng J, Waldmann M, Ceriani F, Johnson SL, Olt J, Rüttiger L, Marcotti W, Holley MC. Gata3 is required for the functional maturation of inner hair cells and their innervation in the mouse cochlea. J Physiol 2019; 597:3389-3406. [PMID: 31069810 PMCID: PMC6636704 DOI: 10.1113/jp277997] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 05/07/2019] [Indexed: 01/14/2023] Open
Abstract
KEY POINTS The physiological maturation of auditory hair cells and their innervation requires precise temporal and spatial control of cell differentiation. The transcription factor gata3 is essential for the earliest stages of auditory system development and for survival and synaptogenesis in auditory sensory afferent neurons. We show that during postnatal development in the mouse inner ear gata3 is required for the biophysical maturation, growth and innervation of inner hair cells; in contrast, it is required only for the survival of outer hair cells. Loss of gata3 in inner hair cells causes progressive hearing loss and accounts for at least some of the deafness associated with the human hypoparathyroidism, deafness and renal anomaly (HDR) syndrome. The results show that gata3 is critical for later stages of mammalian auditory system development where it plays distinct, complementary roles in the coordinated maturation of sensory hair cells and their innervation. ABSTRACT The zinc finger transcription factor gata3 regulates inner ear development from the formation of the embryonic otic placode. Throughout development, gata3 is expressed dynamically in all the major cochlear cell types. Its role in afferent formation is well established but its possible involvement in hair cell maturation remains unknown. Here, we find that in heterozygous gata3 null mice (gata3+/- ) outer hair cells (OHCs) differentiate normally but their numbers are significantly lower. In contrast, inner hair cells (IHCs) survive normally but they fail to acquire adult basolateral membrane currents, retain pre-hearing current and efferent innervation profiles and have fewer ribbon synapses. Targeted deletion of gata3 driven by otoferlin-cre recombinase (gata3fl/fl otof-cre+/- ) in IHCs does not affect OHCs or the number of IHC afferent synapses but it leads to a failure in IHC maturation comparable to that observed in gata3+/- mice. Auditory brainstem responses in gata3fl/fl otof-cre+/- mice reveal progressive hearing loss that becomes profound by 6-7 months, whilst distortion product otoacoustic emissions are no different to control animals up to this age. Our results, alongside existing data, indicate that gata3 has specific, complementary functions in different cell types during inner ear development and that its continued expression in the sensory epithelium orchestrates critical aspects of physiological development and neural connectivity. Furthermore, our work indicates that hearing loss in human hypoparathyroidism, deafness and renal anomaly (HDR) syndrome arises from functional deficits in IHCs as well as loss of function from OHCs and both afferent and efferent neurons.
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MESH Headings
- Animals
- Cell Differentiation/physiology
- Cochlea/metabolism
- Cochlea/physiology
- GATA3 Transcription Factor/metabolism
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/physiology
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/physiology
- Hair Cells, Vestibular/metabolism
- Hair Cells, Vestibular/physiology
- Hearing/physiology
- Hearing Loss/metabolism
- Hearing Loss/physiopathology
- Membrane Proteins/metabolism
- Mice, Knockout
- Mice, Transgenic
- Sensory Receptor Cells/metabolism
- Sensory Receptor Cells/physiology
- Synapses/metabolism
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Affiliation(s)
- Tanaya Bardhan
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
| | - Jing‐Yi Jeng
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
| | - Marco Waldmann
- Department of OtolaryngologyTübingen Hearing Research CenterSection of Physiological Acoustics and CommunicationUniversity of Tübingen72076TübingenGermany
| | - Federico Ceriani
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
| | | | - Jennifer Olt
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
| | - Lukas Rüttiger
- Department of OtolaryngologyTübingen Hearing Research CenterSection of Physiological Acoustics and CommunicationUniversity of Tübingen72076TübingenGermany
| | - Walter Marcotti
- Department of Biomedical ScienceUniversity of SheffieldSheffieldUK
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42
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Wagner EL, Shin JB. Mechanisms of Hair Cell Damage and Repair. Trends Neurosci 2019; 42:414-424. [PMID: 30992136 DOI: 10.1016/j.tins.2019.03.006] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 03/04/2019] [Accepted: 03/13/2019] [Indexed: 01/22/2023]
Abstract
Sensory hair cells of the inner ear are exposed to continuous mechanical stress, causing damage over time. The maintenance of hair cells is further challenged by damage from a variety of other ototoxic factors, including loud noise, aging, genetic defects, and ototoxic drugs. This damage can manifest in many forms, from dysfunction of the hair cell mechanotransduction complex to loss of specialized ribbon synapses, and may even result in hair cell death. Given that mammalian hair cells do not regenerate, the repair of hair cell damage is important for continued auditory function throughout life. Here, we discuss how several key hair cell structures can be damaged, and what is known about how they are repaired.
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Affiliation(s)
- Elizabeth L Wagner
- Department of Neuroscience, University of Virginia-School of Medicine, Charlottesville, VA 22908, USA; Department of Biochemistry and Molecular Genetics, University of Virginia-School of Medicine, Charlottesville, VA 22908, USA
| | - Jung-Bum Shin
- Department of Neuroscience, University of Virginia-School of Medicine, Charlottesville, VA 22908, USA.
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43
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Ceriani F, Hendry A, Jeng JY, Johnson SL, Stephani F, Olt J, Holley MC, Mammano F, Engel J, Kros CJ, Simmons DD, Marcotti W. Coordinated calcium signalling in cochlear sensory and non-sensory cells refines afferent innervation of outer hair cells. EMBO J 2019; 38:embj.201899839. [PMID: 30804003 PMCID: PMC6484507 DOI: 10.15252/embj.201899839] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 12/11/2018] [Accepted: 01/18/2019] [Indexed: 12/12/2022] Open
Abstract
Outer hair cells (OHCs) are highly specialized sensory cells conferring the fine‐tuning and high sensitivity of the mammalian cochlea to acoustic stimuli. Here, by genetically manipulating spontaneous Ca2+ signalling in mice in vivo, through a period of early postnatal development, we find that the refinement of OHC afferent innervation is regulated by complementary spontaneous Ca2+ signals originating in OHCs and non‐sensory cells. OHCs fire spontaneous Ca2+ action potentials during a narrow period of neonatal development. Simultaneously, waves of Ca2+ activity in the non‐sensory cells of the greater epithelial ridge cause, via ATP‐induced activation of P2X3 receptors, the increase and synchronization of the Ca2+ activity in nearby OHCs. This synchronization is required for the refinement of their immature afferent innervation. In the absence of connexin channels, Ca2+ waves are impaired, leading to a reduction in the number of ribbon synapses and afferent fibres on OHCs. We propose that the correct maturation of the afferent connectivity of OHCs requires experience‐independent Ca2+ signals from sensory and non‐sensory cells.
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Affiliation(s)
- Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Aenea Hendry
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Friederike Stephani
- Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Jennifer Olt
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Matthew C Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Fabio Mammano
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padova, Italy.,Department of Biomedical Sciences, Institute of Cell Biology and Neurobiology, Italian National Research Council, Monterotondo, Italy
| | - Jutta Engel
- Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Corné J Kros
- School of Life Sciences, University of Sussex, Brighton, UK
| | | | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
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