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Li Y, Yu H, Zhou X, Jin L, Li W, Li GL, Shen X. Multiple Sevoflurane Exposures During the Neonatal Period Cause Hearing Impairment and Loss of Hair Cell Ribbon Synapses in Adult Mice. Front Neurosci 2022; 16:945277. [PMID: 35911996 PMCID: PMC9329801 DOI: 10.3389/fnins.2022.945277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 06/24/2022] [Indexed: 11/13/2022] Open
Abstract
Objectives This study aims to investigate the effects of multiple sevoflurane exposures in neonatal mice on hearing function in the later life and explores the underlying mechanisms and protective strategies. Materials and Methods Neonatal Kunming mice were exposed to sevoflurane for 3 days. Auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) tests, immunofluorescence, patch-clamp recording, and quantitative real-time PCR were performed to observe hearing function, hair cells, ribbon synapses, nerve fibers, spiral ganglion neurons, and oxidative stress. Results Compared to control group, multiple sevoflurane exposures during the neonatal time significantly elevated ABR thresholds at 8 kHz (35.42 ± 1.57 vs. 41.76 ± 1.97 dB, P = 0.0256), 16 kHz (23.33 ± 1.28 vs. 33.53 ± 2.523 dB, P = 0.0012), 24 kHz (30.00 ± 2.04 vs. 46.76 ± 3.93 dB, P = 0.0024), and 32 kHz (41.25 ± 2.31 vs. 54.41 ± 2.94 dB, P = 0.0028) on P30, caused ribbon synapse loss on P15 (13.10 ± 0.43 vs. 10.78 ± 0.52, P = 0.0039) and P30 (11.24 ± 0.56 vs. 8.50 ± 0.84, P = 0.0141), and degenerated spiral ganglion neuron (SGN) nerve fibers on P30 (110.40 ± 16.23 vs. 55.04 ± 8.13, P = 0.0073). In addition, the Vhalf of calcium current become more negative (−21.99 ± 0.70 vs. −27.17 ± 0.60 mV, P < 0.0001), exocytosis was reduced (105.40 ± 19.97 vs. 59.79 ± 10.60 fF, P < 0.0001), and Lpo was upregulated (P = 0.0219) in sevoflurane group than those in control group. N-acetylcysteine (NAC) reversed hearing impairment induced by sevoflurane. Conclusion The findings suggest that multiple sevoflurane exposures during neonatal time may cause hearing impairment in adult mice. The study also demonstrated that elevated oxidative stress led to ribbon synapses impairment and SGN nerve fibers degeneration, and the interventions of antioxidants alleviated the sevoflurane-induced hearing impairment.
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Affiliation(s)
- Yufeng Li
- Department of Anesthesiology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Huiqian Yu
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Xuehua Zhou
- Department of Anesthesiology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Lin Jin
- Department of Anesthesiology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Wen Li
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Geng-Lin Li
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
- *Correspondence: Geng-Lin Li,
| | - Xia Shen
- Department of Anesthesiology, Eye & ENT Hospital, Fudan University, Shanghai, China
- Xia Shen,
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2
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Hickox AE, Valero MD, McLaughlin JT, Robinson GS, Wellman JA, McKenna MJ, Sewell WF, Simons EJ. Genetic Medicine for Hearing Loss: OTOF as Exemplar. J Am Acad Audiol 2022; 32:646-653. [PMID: 35609591 DOI: 10.1055/s-0041-1730410] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Millions of people worldwide have disabling hearing loss because one of their genes generates an incorrect version of some specific protein the ear requires for hearing. In many of these cases, delivering the correct version of the gene to a specific target cell within the inner ear has the potential to restore cochlear function to enable high-acuity physiologic hearing. Purpose: In this review, we outline our strategy for the development of genetic medicines with the potential to treat hearing loss. We will use the example of otoferlin gene (OTOF)-mediated hearing loss, a sensorineural hearing loss due to autosomal recessive mutations of the OTOF gene.
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Affiliation(s)
| | | | | | | | | | | | - William F Sewell
- Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts
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3
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Mukherjee D, Meng X, Kao JPY, Kanold PO. Impaired Hearing and Altered Subplate Circuits During the First and Second Postnatal Weeks of Otoferlin-Deficient Mice. Cereb Cortex 2021; 32:2816-2830. [PMID: 34849612 DOI: 10.1093/cercor/bhab383] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/23/2021] [Accepted: 09/25/2021] [Indexed: 02/01/2023] Open
Abstract
Sensory deprivation from the periphery impacts cortical development. Otoferlin deficiency leads to impaired cochlear synaptic transmission and is associated with progressive hearing loss in adults. However, it remains elusive how sensory deprivation due to otoferlin deficiency impacts the early development of the auditory cortex (ACX) especially before the onset of low threshold hearing. To test that, we performed in vivo imaging of the ACX in awake mice lacking otoferlin (Otof-/-) during the first and second postnatal weeks and found that spontaneous and sound-driven cortical activity were progressively impaired. We then characterized the effects on developing auditory cortical circuits by performing in vitro recordings from subplate neurons (SPN), the first primary targets of thalamocortical inputs. We found that in Otof-/- pups, SPNs received exuberant connections from excitatory and inhibitory neurons. Moreover, as a population, SPNs showed higher similarity with respect to their circuit topology in the absence of otoferlin. Together, our results show that otoferlin deficiency results in impaired hearing and has a powerful influence on cortical connections and spontaneous activity in early development even before complete deafness. Therefore, peripheral activity has the potential to sculpt cortical structures from the earliest ages, even before hearing impairment is diagnosed.
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Affiliation(s)
- Didhiti Mukherjee
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA.,Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Xiangying Meng
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA.,Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Joseph P Y Kao
- Center for Biomedical Engineering and Technology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Patrick O Kanold
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA.,Department of Biology, University of Maryland, College Park, MD 20742, USA.,Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD 21205, USA
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4
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Koleilat A, Dugdale JA, Christenson TA, Bellah JL, Lambert AM, Masino MA, Ekker SC, Schimmenti LA. L-type voltage-gated calcium channel agonists mitigate hearing loss and modify ribbon synapse morphology in the zebrafish model of Usher syndrome type 1. Dis Model Mech 2020; 13:13/11/dmm043885. [PMID: 33361086 PMCID: PMC7710014 DOI: 10.1242/dmm.043885] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 09/15/2020] [Indexed: 01/19/2023] Open
Abstract
The mariner (myo7aa−/−) mutant is a zebrafish model for Usher syndrome type 1 (USH1). To further characterize hair cell synaptic elements in myo7aa−/− mutants, we focused on the ribbon synapse and evaluated ultrastructure, number and distribution of immunolabeled ribbons, and postsynaptic densities. By transmission electron microscopy, we determined that myo7aa−/− zebrafish have fewer glutamatergic vesicles tethered to ribbon synapses, yet maintain a comparable ribbon area. In myo7aa−/− hair cells, immunolocalization of Ctbp2 showed fewer ribbon-containing cells in total and an altered distribution of Ctbp2 puncta compared to wild-type hair cells. myo7aa−/− mutants have fewer postsynaptic densities – as assessed by MAGUK immunolabeling – compared to wild-type zebrafish. We quantified the circular swimming behavior of myo7aa−/− mutant fish and measured a greater turning angle (absolute smooth orientation). It has previously been shown that L-type voltage-gated calcium channels are necessary for ribbon localization and occurrence of postsynaptic density; thus, we hypothesized and observed that L-type voltage-gated calcium channel agonists change behavioral and synaptic phenotypes in myo7aa−/− mutants in a drug-specific manner. Our results indicate that treatment with L-type voltage-gated calcium channel agonists alter hair cell synaptic elements and improve behavioral phenotypes of myo7aa−/− mutants. Our data support that L-type voltage-gated calcium channel agonists induce morphological changes at the ribbon synapse – in both the number of tethered vesicles and regarding the distribution of Ctbp2 puncta – shift swimming behavior and improve acoustic startle response. Summary: We quantified behavioral and synaptic morphology differences between wild-type zebrafish larvae and the mariner (myo7aa−/−) mutant, finding that these differences can be modified by L-type voltage-gated calcium channel agonists.
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Affiliation(s)
- Alaa Koleilat
- College of Continuing and Professional Studies, University of Minnesota, Minneapolis, MN 55108, USA.,Mayo Clinic Graduate School of Biomedical Sciences, Clinical and Translational Science Track, Rochester, MN 55905, USA.,Center for Clinical and Translational Science, Mayo Clinic, Rochester, MN 55905, USA
| | - Joseph A Dugdale
- Department of Otorhinolaryngology, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Jeffrey L Bellah
- Center for Clinical and Translational Science, Mayo Clinic, Rochester, MN 55905, USA.,Department of Genetics and Development, Columbia University, New York City, NY 10032, USA
| | - Aaron M Lambert
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.,Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Mark A Masino
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Stephen C Ekker
- Center for Clinical and Translational Science, Mayo Clinic, Rochester, MN 55905, USA.,Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Lisa A Schimmenti
- Department of Otorhinolaryngology, Mayo Clinic, Rochester, MN 55905, USA .,Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA.,Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455, USA.,Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA.,Department of Ophthalmology and Visual Neuroscience, University of Minnesota, Minneapolis, MN 55454, USA.,Department of Clinical Genomics, Mayo Clinic, Rochester, MN 55905, USA
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5
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Voorn RA, Vogl C. Molecular Assembly and Structural Plasticity of Sensory Ribbon Synapses-A Presynaptic Perspective. Int J Mol Sci 2020; 21:E8758. [PMID: 33228215 PMCID: PMC7699581 DOI: 10.3390/ijms21228758] [Citation(s) in RCA: 9] [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: 10/21/2020] [Revised: 11/16/2020] [Accepted: 11/17/2020] [Indexed: 12/13/2022] Open
Abstract
In the mammalian cochlea, specialized ribbon-type synapses between sensory inner hair cells (IHCs) and postsynaptic spiral ganglion neurons ensure the temporal precision and indefatigability of synaptic sound encoding. These high-through-put synapses are presynaptically characterized by an electron-dense projection-the synaptic ribbon-which provides structural scaffolding and tethers a large pool of synaptic vesicles. While advances have been made in recent years in deciphering the molecular anatomy and function of these specialized active zones, the developmental assembly of this presynaptic interaction hub remains largely elusive. In this review, we discuss the dynamic nature of IHC (pre-) synaptogenesis and highlight molecular key players as well as the transport pathways underlying this process. Since developmental assembly appears to be a highly dynamic process, we further ask if this structural plasticity might be maintained into adulthood, how this may influence the functional properties of a given IHC synapse and how such plasticity could be regulated on the molecular level. To do so, we take a closer look at other ribbon-bearing systems, such as retinal photoreceptors and pinealocytes and aim to infer conserved mechanisms that may mediate these phenomena.
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MESH Headings
- Alcohol Oxidoreductases/genetics
- Alcohol Oxidoreductases/metabolism
- Animals
- Co-Repressor Proteins/genetics
- Co-Repressor Proteins/metabolism
- Cytoskeletal Proteins/genetics
- Cytoskeletal Proteins/metabolism
- Cytoskeleton/metabolism
- Cytoskeleton/ultrastructure
- Gene Expression Regulation, Developmental
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/ultrastructure
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/ultrastructure
- Hair Cells, Vestibular/metabolism
- Hair Cells, Vestibular/ultrastructure
- Mechanotransduction, Cellular
- Mice
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neuronal Plasticity/genetics
- Neuropeptides/genetics
- Neuropeptides/metabolism
- Rats
- Synapses/metabolism
- Synapses/ultrastructure
- Synaptic Transmission/genetics
- Synaptic Vesicles/metabolism
- Synaptic Vesicles/ultrastructure
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Affiliation(s)
- Roos Anouk Voorn
- Presynaptogenesis and Intracellular Transport in Hair Cells Junior Research Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Goettingen, 37075 Goettingen, Germany;
- Göttingen Graduate Center for Neurosciences, Biophysics and Molecular Biosciences, 37075 Goettingen, Germany
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”, 37075 Goettingen, Germany
| | - Christian Vogl
- Presynaptogenesis and Intracellular Transport in Hair Cells Junior Research Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Goettingen, 37075 Goettingen, Germany;
- Collaborative Research Center 889 “Cellular Mechanisms of Sensory Processing”, 37075 Goettingen, Germany
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6
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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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7
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Liu H, Lu J, Wang Z, Song L, Wang X, Li GL, Wu H. Functional alteration of ribbon synapses in inner hair cells by noise exposure causing hidden hearing loss. Neurosci Lett 2019; 707:134268. [DOI: 10.1016/j.neulet.2019.05.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/23/2019] [Accepted: 05/13/2019] [Indexed: 01/30/2023]
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8
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Takago H, Oshima-Takago T, Moser T. Disruption of Otoferlin Alters the Mode of Exocytosis at the Mouse Inner Hair Cell Ribbon Synapse. Front Mol Neurosci 2019; 11:492. [PMID: 30687007 PMCID: PMC6338019 DOI: 10.3389/fnmol.2018.00492] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 12/19/2018] [Indexed: 11/24/2022] Open
Abstract
Sound encoding relies on Ca2+-mediated exocytosis at the ribbon synapse between cochlear inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs). Otoferlin, a multi-C2 domain protein, is proposed to regulate Ca2+-triggered exocytosis at this synapse, but the precise mechanisms of otoferlin function remain to be elucidated. Here, performing whole-cell voltage-clamp recordings of excitatory postsynaptic currents (EPSCs) from SGNs in otoferlin mutant mice, we investigated the impact of Otof disruption at individual synapses with single release event resolution. Otof deletion decreased the spontaneous release rate and abolished the stimulus-secretion coupling. This was evident from failure of potassium-induced IHC depolarization to stimulate release and supports the proposed role of otoferlin in Ca2+ sensing for fusion. A missense mutation in the Otof gene (pachanga), in which otoferlin level at the IHC plasma membrane was lowered without changing its Ca2+ binding, also reduced the spontaneous release rate but spared the stimulus-secretion coupling. The slowed stimulated release rate supports the hypothesis that a sufficient abundance of otoferlin at the plasma membrane is crucial for the vesicle supply. Large-sized monophasic EPSCs remained present upon Otof deletion despite the drastic reduction of the rate of exocytosis. However, EPSC amplitude, on average, was modestly decreased. Moreover, a reduced contribution of multiphasic EPSC was observed in both Otof mutants. We argue that the presence of large monophasic EPSCs despite the exocytic defect upon Otof deletion supports the uniquantal hypothesis of transmitter release at the IHC ribbon synapse. Based upon the reduced contribution of multiphasic EPSC, we propose a role of otoferlin in regulating the mode of exocytosis in IHCs.
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Affiliation(s)
- Hideki Takago
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Department of Rehabilitation for Sensory Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany
| | - Tomoko Oshima-Takago
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Department of Rehabilitation for Sensory Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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9
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Wang J, Yin S, Chen H, Shi L. Noise-Induced Cochlear Synaptopathy and Ribbon Synapse Regeneration: Repair Process and Therapeutic Target. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1130:37-57. [PMID: 30915700 DOI: 10.1007/978-981-13-6123-4_3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The synapse between the inner hair cells (IHCs) and the spiral ganglion neurons (SGNs) in mammalian cochleae is characterized as having presynaptic ribbons and therefore is called ribbon synapse. The special molecular organization is reviewed in this chapter in association with the functional feature of this synapse in signal processing. This is followed by the review on noise-induced damage to this synapse with a focus on recent reports in animal models in which the effect of brief noise exposures is observed without causing significant permanent threshold shift (PTS). In this regard, the potential mechanism of the synaptic damage by noise and the impact of this damage on hearing are summarized to clarify the concept of noise-induced hidden hearing loss, which is defined as the functional deficits in hearing without threshold elevation. A controversial issue is addressed in this review as whether the disrupted synapses can be regenerated. Moreover, the review summarizes the work of therapeutic research to protect the synapses or to promote the regeneration of the synapse after initial disruption. Lastly, several unresolved issues are raised for investigation in the future.
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Affiliation(s)
- Jian Wang
- School of Communication Science and Disorders, Dalhousie University, Halifax, NS, Canada.
| | - Shankai Yin
- Otolaryngology Research Institute, 6th Affiliated Hospital, Shanghai Jiao-Tong University, Shanghai, China
| | - Hengchao Chen
- Otolaryngology Research Institute, 6th Affiliated Hospital, Shanghai Jiao-Tong University, Shanghai, China
| | - Lijuan Shi
- Department of Physiology, Medical College of Southeast University, Nanjing, China
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10
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Pangrsic T, Vogl C. Balancing presynaptic release and endocytic membrane retrieval at hair cell ribbon synapses. FEBS Lett 2018; 592:3633-3650. [PMID: 30251250 DOI: 10.1002/1873-3468.13258] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 09/18/2018] [Accepted: 09/19/2018] [Indexed: 11/07/2022]
Abstract
The timely and reliable processing of auditory and vestibular information within the inner ear requires highly sophisticated sensory transduction pathways. On a cellular level, these demands are met by hair cells, which respond to sound waves - or alterations in body positioning - by releasing glutamate-filled synaptic vesicles (SVs) from their presynaptic active zones with unprecedented speed and exquisite temporal fidelity, thereby initiating the auditory and vestibular pathways. In order to achieve this, hair cells have developed anatomical and molecular specializations, such as the characteristic and name-giving 'synaptic ribbons' - presynaptically anchored dense bodies that tether SVs prior to release - as well as other unique or unconventional synaptic proteins. The tightly orchestrated interplay between these molecular components enables not only ultrafast exocytosis, but similarly rapid and efficient compensatory endocytosis. So far, the knowledge of how endocytosis operates at hair cell ribbon synapses is limited. In this Review, we summarize recent advances in our understanding of the SV cycle and molecular anatomy of hair cell ribbon synapses, with a focus on cochlear inner hair cells.
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Affiliation(s)
- Tina Pangrsic
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, University Medical Center Göttingen, Germany
| | - Christian Vogl
- Presynaptogenesis and Intracellular Transport in Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, University Medical Center Göttingen, Germany
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11
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Moser T. [Molecular Understanding of Hearing - How Does This Matter to the Hearing Impaired?]. Laryngorhinootologie 2018; 97:S214-S230. [PMID: 29905358 PMCID: PMC6541096 DOI: 10.1055/s-0043-121595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
This review addresses the advances of our molecular understanding of hearing and how this benefits the hearing impaired. Classical biochemical methods usually fall short in contributing to the analysis of the molecular mechanisms of hearing e. g. in the cochlea, the auditory part of the inner ear, due to the scarcity of the cells of interest. Genetics, molecular cell biology, and physiology, on the other hand, have elucidated the intricate molecular and cellular mechanisms that bring about the outstanding performance of the auditory system. Many of those mechanisms are quite unique and specialized to serve the specific needs of hearing. Hence, their defects often spare other organs and lead to specific non-syndromic deafness. High throughput sequencing can reveal causes of sporadic deafness when combined with careful bioinformatics. Molecular approaches are also helpful for understanding more common forms of hearing impairment such as noise-induced hearing impairment. While molecular therapies are not yet clinically available, careful molecular genetic analysis helps to counsel the hearing impaired subjects.
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Affiliation(s)
- Tobias Moser
- Institut für Auditorische Neurowissenschaften, Universitätsmedizin Göttingen
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12
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Jean P, Lopez de la Morena D, Michanski S, Jaime Tobón LM, Chakrabarti R, Picher MM, Neef J, Jung S, Gültas M, Maxeiner S, Neef A, Wichmann C, Strenzke N, Grabner C, Moser T. The synaptic ribbon is critical for sound encoding at high rates and with temporal precision. eLife 2018; 7:29275. [PMID: 29328020 PMCID: PMC5794258 DOI: 10.7554/elife.29275] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 12/19/2017] [Indexed: 11/30/2022] Open
Abstract
We studied the role of the synaptic ribbon for sound encoding at the synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) in mice lacking RIBEYE (RBEKO/KO). Electron and immunofluorescence microscopy revealed a lack of synaptic ribbons and an assembly of several small active zones (AZs) at each synaptic contact. Spontaneous and sound-evoked firing rates of SGNs and their compound action potential were reduced, indicating impaired transmission at ribbonless IHC-SGN synapses. The temporal precision of sound encoding was impaired and the recovery of SGN-firing from adaptation indicated slowed synaptic vesicle (SV) replenishment. Activation of Ca2+-channels was shifted to more depolarized potentials and exocytosis was reduced for weak depolarizations. Presynaptic Ca2+-signals showed a broader spread, compatible with the altered Ca2+-channel clustering observed by super-resolution immunofluorescence microscopy. We postulate that RIBEYE disruption is partially compensated by multi-AZ organization. The remaining synaptic deficit indicates ribbon function in SV-replenishment and Ca2+-channel regulation. Our sense of hearing relies on our ears quickly and tirelessly processing information in a precise manner. Sounds cause vibrations in a part of the inner ear called the cochlea. Inside the cochlea, the vibrations move hair-like structures on sensory cells that translate these movements into electrical signals. These hair cells are connected to specialized nerve cells that relay the signals to the brain, which then interprets them as sounds. Hair cells communicate with the specialized nerve cells via connections known as chemical synapses. This means that the electrical signals in the hair cell activate channel proteins that allow calcium ions to flow in. This in turn triggers membrane-bound packages called vesicles inside the hair cell to fuse with its surface membrane and release their contents to the outside. The contents, namely chemicals called neurotransmitters, then travels across the space between the cells, relaying the signal to the nerve cell. The junctions between the hair cells and the nerve cells are more specifically known as ribbon synapses. This is because they have a ribbon-like structure that appears to tether a halo of vesicles close to the active zone where neurotransmitters are released. However, the exact role of this synaptic ribbon has remained mysterious despite decades of study. The ribbon is mainly composed of a protein called Ribeye, and now Jean, Lopez de la Morena, Michanski, Jaime Tobón et al. show that mutant mice that lack this protein do not have any ribbons at their “ribbon synapses”. Hair cells without synaptic ribbons are less able to timely and reliably send signals to the nerve cells, most likely because they cannot replenish the vesicles at the synapse quickly enough. Further analysis showed that the synaptic ribbon also helps to regulate the calcium channels at the synapse, which is important for linking the electrical signals in the hair cell to the release of the neurotransmitters. Jean et al. also saw that hair cells without ribbons reorganize their synapses to form multiple active zones that could transfer neurotransmitter to the nerve cells. This could partially compensate for the loss of the ribbons, meaning the impact of their loss may have been underestimated. Future studies could explore this by eliminating the Ribeye protein only after the ribbon synapses are fully formed. These findings may help scientists to better understand deafness and other hearing disorders in humans. They will also be of interest to neuroscientists who research synapses, hearing and other sensory processes.
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Affiliation(s)
- Philippe Jean
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany
| | - David Lopez de la Morena
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany
| | - Susann Michanski
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany.,Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Lina María Jaime Tobón
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Rituparna Chakrabarti
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany.,Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Maria Magdalena Picher
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany
| | - Jakob Neef
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - SangYong Jung
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Neuro Modulation and Neuro Circuitry Group, Singapore Bioimaging Consortium (SBIC), Biomedical Sciences Institutes, Singapore, Singapore
| | - Mehmet Gültas
- Department of Breeding Informatics, Georg-August-University Göttingen, Göttingen, Germany
| | - Stephan Maxeiner
- Institute for Anatomy and Cell Biology, University of the Saarland, Homburg, Germany
| | - Andreas Neef
- Bernstein Group Biophysics of Neural Computation, Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany
| | - Carolin Wichmann
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen, Germany.,Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Nicola Strenzke
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Auditory Systems Physiology Group, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany
| | - Chad Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
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13
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Krinner S, Butola T, Jung S, Wichmann C, Moser T. RIM-Binding Protein 2 Promotes a Large Number of Ca V1.3 Ca 2+-Channels and Contributes to Fast Synaptic Vesicle Replenishment at Hair Cell Active Zones. Front Cell Neurosci 2017; 11:334. [PMID: 29163046 PMCID: PMC5673845 DOI: 10.3389/fncel.2017.00334] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 10/11/2017] [Indexed: 12/20/2022] Open
Abstract
Ribbon synapses of inner hair cells (IHCs) mediate high rates of synchronous exocytosis to indefatigably track the stimulating sound with sub-millisecond precision. The sophisticated molecular machinery of the inner hair cell active zone realizes this impressive performance by enabling a large number of synaptic voltage-gated CaV1.3 Ca2+-channels, their tight coupling to synaptic vesicles (SVs) and fast replenishment of fusion competent SVs. Here we studied the role of RIM-binding protein 2 (RIM-BP2)—a multidomain cytomatrix protein known to directly interact with Rab3 interacting molecules (RIMs), bassoon and CaV1.3—that is present at the inner hair cell active zones. We combined confocal and stimulated emission depletion (STED) immunofluorescence microscopy, electron tomography, patch-clamp and confocal Ca2+-imaging, as well as auditory systems physiology to explore the morphological and functional effects of genetic RIM-BP2 disruption in constitutive RIM-BP2 knockout mice. We found that RIM-BP2 (1) positively regulates the number of synaptic CaV1.3 channels and thereby facilitates synaptic vesicle release and (2) supports fast synaptic vesicle recruitment after readily releasable pool (RRP) depletion. However, Ca2+-influx—exocytosis coupling seemed unaltered for readily releasable SVs. Recordings of auditory brainstem responses (ABR) and of single auditory nerve fiber firing showed that RIM-BP2 disruption results in a mild deficit of synaptic sound encoding.
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Affiliation(s)
- Stefanie Krinner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,IMPRS Molecular Biology, Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Tanvi Butola
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,IMPRS Neuroscience, Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - SangYong Jung
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,DFG-Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, Göttingen, Germany.,Neuromodulation and Neurocircuitry Group, Singapore Bioimaging Consortium (SBIC), Biomedical Sciences Institutes (BMSI), Agency for Science Technology and Research (A∗STAR), Singapore, Singapore
| | - Carolin Wichmann
- Collaborative Research Center, University of Göttingen, Göttingen, Germany.,Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center, University of Göttingen, Göttingen, Germany.,IMPRS Molecular Biology, Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,DFG-Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, Göttingen, Germany
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14
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Neurosecretion: what can we learn from chromaffin cells. Pflugers Arch 2017; 470:7-11. [PMID: 28801866 PMCID: PMC5748399 DOI: 10.1007/s00424-017-2051-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 07/31/2017] [Accepted: 08/01/2017] [Indexed: 12/16/2022]
Abstract
Many of the molecular players in the stimulus-secretion chain are similarly active in neurosecretion and catecholamine release. Therefore, studying chromaffin cells uncovered many details of the processes of docking, priming, and exocytosis of vesicles. However, morphological specializations at synapses, called active zones (AZs), confer extra speed of response and another layer of control to the fast release of vesicles by action potentials. Work at the Calyx of Held, a glutamatergic nerve terminal, has shown that in addition to such rapidly released vesicles, there is a pool of “Slow Vesicles,” which are held to be perfectly release-competent, but lack a final step of tight interaction with the AZ. It is argued here that such “Slow Vesicles” have many properties in common with chromaffin granules. The added complexity in the AZ-dependent regulation of “Fast Vesicles” can lead to misinterpretation of data on neurosecretion. Therefore, the study of Slow Vesicles and of chromaffin granules may provide a clearer picture of the early steps in the highly regulated process of neurosecretion.
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15
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Affiliation(s)
- Karen B Avraham
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
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