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Kui L, Ma P, Zhao W, Yan B, Kuang X, Li B, Geng R, Zheng T, Zheng Q. Developmental cochlear defects are involved in early-onset hearing loss in A/J mice. Dev Dyn 2024. [PMID: 39291400 DOI: 10.1002/dvdy.741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2024] [Revised: 08/19/2024] [Accepted: 08/22/2024] [Indexed: 09/19/2024] Open
Abstract
BACKGROUND A/J mice exhibited a severe hearing loss (HL) at juvenile stage. Up-to-date, studies on HL in A/J mice have mostly focused on the damage or dysfunction of hair cells (HCs), spiral ganglion neurons (SGNs), and stereocilia. We examined A/J mice at the early postnatal stage and found that the damage and the loss of outer hair cells (OHCs) are not severe enough to explain the profound HL observed at this age, which suggests that other cochlear defects may be responsible for HL. To better understand the mechanisms of early-onset HLin A/J mice, we characterized the pathology of the cochlea from postnatal day 3 to day 21. RESULTS Our results showed defects in cochlear HC stereocilia and MET channel function as early as 3 days old. We also found abnormal localization and a significant reduction in the number of ribbon synapses in 2-week-old A/J mice. There are also abnormalities in the cochlear nerve innervation and terminal swellings in 3-week-old A/J mice. CONCLUSION All of the abnormalities of cochlear existed in the A/J mice were identified in the juvenile stage and occurred before HCs or auditory nerve loss and was the initial pathological change. Our results suggest that developmental defects and subsequent cochlear degeneration are responsible for early-onset hearing loss in A/J mice.
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Affiliation(s)
- Lihong Kui
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, Yantai, China
| | - Peng Ma
- Department of Medical Genetics and Cell Biology, Binzhou Medical University, Yantai, China
| | - Wenben Zhao
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, Yantai, China
| | - Bin Yan
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, Yantai, China
| | - Xiaojing Kuang
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, Yantai, China
| | - Bo Li
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, Yantai, China
| | - Ruishuang Geng
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, Yantai, China
| | - Tihua Zheng
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, Yantai, China
| | - Qingyin Zheng
- Hearing and Speech Rehabilitation Institute, College of Special Education and Rehabilitation, Binzhou Medical University, Yantai, China
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2
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Holt JR, Fettiplace R, Müller U. Sensory transduction in auditory hair cells-PIEZOs can't touch this. J Gen Physiol 2024; 156:e202413585. [PMID: 38727631 PMCID: PMC11090049 DOI: 10.1085/jgp.202413585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2024] Open
Abstract
In this Viewpoint, Holt, Fettiplace, and Müller weigh the evidence supporting a role for PIEZO and TMC channels in mechanosensory transduction in inner ear hair cells.
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Affiliation(s)
- Jeffrey R. Holt
- Departments of Otolaryngology and Neurology, Boston Children’s Hospital and Harvard Medical School, Boston, MA, USA
| | - Robert Fettiplace
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Ulrich Müller
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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3
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Maruyama A, Kawashima Y, Fukunaga Y, Makabe A, Nishio A, Tsutsumi T. Susceptibility of mouse cochlear hair cells to cisplatin ototoxicity largely depends on sensory mechanoelectrical transduction channels both Ex Vivo and In Vivo. Hear Res 2024; 447:109013. [PMID: 38718672 DOI: 10.1016/j.heares.2024.109013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 03/28/2024] [Accepted: 04/18/2024] [Indexed: 05/25/2024]
Abstract
Cisplatin, a highly effective chemotherapeutic drug for various human cancers, induces irreversible sensorineural hearing loss as a side effect. Currently there are no highly effective clinical strategies for the prevention of cisplatin-induced ototoxicity. Previous studies have indicated that short-term cisplatin ototoxicity primarily affects the outer hair cells of the cochlea. Therefore, preventing the entry of cisplatin into hair cells may be a promising strategy to prevent cisplatin ototoxicity. This study aimed to investigate the entry route of cisplatin into mouse cochlear hair cells. The competitive inhibitor of organic cation transporter 2 (OCT2), cimetidine, and the sensory mechanoelectrical transduction (MET) channel blocker benzamil, demonstrated a protective effect against cisplatin toxicity in hair cells in cochlear explants. Sensory MET-deficient hair cells explanted from Tmc1Δ;Tmc2Δ mice were resistant to cisplatin toxicity. Cimetidine showed an additive protective effect against cisplatin toxicity in sensory MET-deficient hair cells. However, in the apical turn, cimetidine, benzamil, or genetic ablation of sensory MET channels showed limited protective effects, implying the presence of other entry routes for cisplatin to enter the hair cells in the apical turn. Systemic administration of cimetidine failed to protect cochlear hair cells from ototoxicity caused by systemically administered cisplatin. Notably, outer hair cells in MET-deficient mice exhibited no apparent deterioration after systemic administration of cisplatin, whereas the outer hair cells in wild-type mice showed remarkable deterioration. The susceptibility of mouse cochlear hair cells to cisplatin ototoxicity largely depends on the sensory MET channel both ex vivo and in vivo. This result justifies the development of new pharmaceuticals, such as a specific antagonists for sensory MET channels or custom-designed cisplatin analogs which are impermeable to sensory MET channels.
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MESH Headings
- Cisplatin/toxicity
- Animals
- Ototoxicity/prevention & control
- Ototoxicity/metabolism
- Ototoxicity/physiopathology
- Mechanotransduction, Cellular/drug effects
- Organic Cation Transporter 2/metabolism
- Organic Cation Transporter 2/genetics
- Organic Cation Transporter 2/antagonists & inhibitors
- Cimetidine/pharmacology
- Antineoplastic Agents/toxicity
- Hair Cells, Auditory/drug effects
- Hair Cells, Auditory/metabolism
- Hair Cells, Auditory/pathology
- Hair Cells, Auditory, Outer/drug effects
- Hair Cells, Auditory, Outer/pathology
- Hair Cells, Auditory, Outer/metabolism
- Mice, Inbred C57BL
- Mice
- Membrane Proteins
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Affiliation(s)
- Ayako Maruyama
- Department of Otolaryngology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
| | - Yoshiyuki Kawashima
- Department of Otolaryngology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
| | - Yoko Fukunaga
- Department of Otolaryngology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan; Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, 54, Kawara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Ayane Makabe
- Department of Otolaryngology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
| | - Ayako Nishio
- Department of Otolaryngology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
| | - Takeshi Tsutsumi
- Department of Otolaryngology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
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4
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Nürnberg B, Beer-Hammer S, Reisinger E, Leiss V. Non-canonical G protein signaling. Pharmacol Ther 2024; 255:108589. [PMID: 38295906 DOI: 10.1016/j.pharmthera.2024.108589] [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: 07/03/2023] [Revised: 12/18/2023] [Accepted: 01/08/2024] [Indexed: 02/17/2024]
Abstract
The original paradigm of classical - also referred to as canonical - cellular signal transduction of heterotrimeric G proteins (G protein) is defined by a hierarchical, orthograde interaction of three players: the agonist-activated G protein-coupled receptor (GPCR), which activates the transducing G protein, that in turn regulates its intracellular effectors. This receptor-transducer-effector concept was extended by the identification of regulators and adapters such as the regulators of G protein signaling (RGS), receptor kinases like βARK, or GPCR-interacting arrestin adapters that are integrated into this canonical signaling process at different levels to enable fine-tuning. Finally, the identification of atypical signaling mechanisms of classical regulators, together with the discovery of novel modulators, added a new and fascinating dimension to the cellular G protein signal transduction. This heterogeneous group of accessory G protein modulators was coined "activators of G protein signaling" (AGS) proteins and plays distinct roles in canonical and non-canonical G protein signaling pathways. AGS proteins contribute to the control of essential cellular functions such as cell development and division, intracellular transport processes, secretion, autophagy or cell movements. As such, they are involved in numerous biological processes that are crucial for diseases, like diabetes mellitus, cancer, and stroke, which represent major health burdens. Although the identification of a large number of non-canonical G protein signaling pathways has broadened the spectrum of this cellular communication system, their underlying mechanisms, functions, and biological effects are poorly understood. In this review, we highlight and discuss atypical G protein-dependent signaling mechanisms with a focus on inhibitory G proteins (Gi) involved in canonical and non-canonical signal transduction, review recent developments and open questions, address the potential of new approaches for targeted pharmacological interventions.
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Affiliation(s)
- Bernd Nürnberg
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, D-72074 Tübingen, Germany.
| | - Sandra Beer-Hammer
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, D-72074 Tübingen, Germany
| | - Ellen Reisinger
- Gene Therapy for Hearing Impairment Group, Department of Otolaryngology - Head & Neck Surgery, University of Tübingen Medical Center, Elfriede-Aulhorn-Straße 5, D-72076 Tübingen, Germany
| | - Veronika Leiss
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, and ICePhA Mouse Clinic, University of Tübingen, Wilhelmstraße 56, D-72074 Tübingen, Germany
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5
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Yang Y, Murtha K, Climer LK, Ceriani F, Thompson P, Hornak AJ, Marcotti W, Simmons DD. Oncomodulin regulates spontaneous calcium signalling and maturation of afferent innervation in cochlear outer hair cells. J Physiol 2023; 601:4291-4308. [PMID: 37642186 PMCID: PMC10621907 DOI: 10.1113/jp284690] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 08/08/2023] [Indexed: 08/31/2023] Open
Abstract
Cochlear outer hair cells (OHCs) are responsible for the exquisite frequency selectivity and sensitivity of mammalian hearing. During development, the maturation of OHC afferent connectivity is refined by coordinated spontaneous Ca2+ activity in both sensory and non-sensory cells. Calcium signalling in neonatal OHCs can be modulated by oncomodulin (OCM, β-parvalbumin), an EF-hand calcium-binding protein. Here, we investigated whether OCM regulates OHC spontaneous Ca2+ activity and afferent connectivity during development. Using a genetically encoded Ca2+ sensor (GCaMP6s) expressed in OHCs in wild-type (Ocm+/+ ) and Ocm knockout (Ocm-/- ) littermates, we found increased spontaneous Ca2+ activity and upregulation of purinergic receptors in OHCs from Ocm-/- cochlea immediately following birth. The afferent synaptic maturation of OHCs was delayed in the absence of OCM, leading to an increased number of ribbon synapses and afferent fibres on Ocm-/- OHCs before hearing onset. We propose that OCM regulates the spontaneous Ca2+ signalling in the developing cochlea and the maturation of OHC afferent innervation. KEY POINTS: Cochlear outer hair cells (OHCs) exhibit spontaneous Ca2+ activity during a narrow period of neonatal development. OHC afferent maturation and connectivity requires spontaneous Ca2+ activity. Oncomodulin (OCM, β-parvalbumin), an EF-hand calcium-binding protein, modulates Ca2+ signals in immature OHCs. Using transgenic mice that endogenously expressed a Ca2+ sensor, GCaMP6s, we found increased spontaneous Ca2+ activity and upregulated purinergic receptors in Ocm-/- OHCs. The maturation of afferent synapses in Ocm-/- OHCs was also delayed, leading to an upregulation of ribbon synapses and afferent fibres in Ocm-/- OHCs before hearing onset. We propose that OCM plays an important role in modulating Ca2+ activity, expression of Ca2+ channels and afferent innervation in developing OHCs.
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Affiliation(s)
- Yang Yang
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Kaitlin Murtha
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Leslie K. Climer
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Federico Ceriani
- School of Biosciences, University of Sheffield, S10 2TN Sheffield, United Kingdom
| | - Pierce Thompson
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Aubrey J. Hornak
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Walter Marcotti
- School of Biosciences, University of Sheffield, S10 2TN Sheffield, United Kingdom
- Sheffield Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Dwayne D. Simmons
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
- School of Biosciences, University of Sheffield, S10 2TN Sheffield, United Kingdom
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA
- Department of Psychology and Neuroscience, Baylor University, Waco, TX
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6
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Cheng C, Ma J, Lu X, Zhang P, Wang X, Guo L, Li P, Wei Y, Li GL, Gao X, Zhang Y, Chai R, Li H, Sun S. P2X7 receptor is required for the ototoxicity caused by aminoglycoside in developing cochlear hair cells. Neurobiol Dis 2023:106176. [PMID: 37263384 DOI: 10.1016/j.nbd.2023.106176] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 05/27/2023] [Accepted: 05/27/2023] [Indexed: 06/03/2023] Open
Abstract
Aminoglycoside antibiotics (AGAs) are widely used in life-threatening infections, but they accumulate in cochlear hair cells (HCs) and result in hearing loss. Increases in adenosine triphosphate (ATP) concentrations and P2X7 receptor expression were observed after neomycin treatment. Here, we demonstrated that P2X7 receptor, which is a non-selective cation channel that is activated by high ATP concentrations, may participate in the process through which AGAs enter hair cells. Using transgenic knockout mice, we found that P2X7 receptor deficiency protects HCs against neomycin-induced injury in vitro and in vivo. Subsequently, we used fluorescent gentamicin-Fluor 594 to study the uptake of AGAs and found fluorescence labeling in wild-type mice but not in P2rx7-/- mice in vitro. In addition, knocking-out P2rx7 did not significantly alter the HC count and auditory signal transduction, but it did inhibit mitochondria-dependent oxidative stress and apoptosis in the cochlea after neomycin exposure. We thus conclude that the P2X7 receptor may be linked to the entry of AGAs into HCs and is likely to be a therapeutic target for auditory HC protection.
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Affiliation(s)
- Cheng Cheng
- Department of Otolaryngology Head and Neck Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Jiangsu Provincial Key Medical Discipline (Laboratory), No.321 Zhongshan Road,Nanjing 210008, China
| | - Jiaoyao Ma
- 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
| | - Xiaoling Lu
- 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
| | - Panpan Zhang
- State Key Laboratory of Digital Medical Engineering, Department of Otolaryngology Head and Neck Surgery, Zhongda Hospital, School of Life Sciences and Technology, Advanced Institute for Life and Health, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing 210096, China
| | - Xiaohan Wang
- State Key Laboratory of Digital Medical Engineering, Department of Otolaryngology Head and Neck Surgery, Zhongda Hospital, School of Life Sciences and Technology, Advanced Institute for Life and Health, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing 210096, 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
| | - Peifan 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
| | - Ying Wei
- Department of Integrative Medicine, Huashan Hospital, Fudan University, Shanghai, China; Institutes of Integrative Medicine, Fudan University, Shanghai, China
| | - Geng-Lin 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
| | - Xia Gao
- Department of Otolaryngology Head and Neck Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Jiangsu Provincial Key Medical Discipline (Laboratory), No.321 Zhongshan Road,Nanjing 210008, China
| | - Yuqiu Zhang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China.
| | - Renjie Chai
- State Key Laboratory of Digital Medical Engineering, Department of Otolaryngology Head and Neck Surgery, Zhongda Hospital, School of Life Sciences and Technology, Advanced Institute for Life and Health, Jiangsu Province High-Tech Key Laboratory for Bio-Medical Research, Southeast University, Nanjing 210096, China; Co-Innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China; Department of Otolaryngology Head and Neck Surgery, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China; Institute for Stem Cell and Regeneration, Chinese Academy of Science, Beijing, China; Beijing Key Laboratory of Neural Regeneration and Repair, Capital Medical University, 100069 Beijing, 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; Fudan University School of Basic Medical Sciences, NHC Key Laboratory of Hearing Medicine, Institutes of Biomedical Sciences, Shanghai, China; State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, 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.
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7
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Krey JF, Chatterjee P, Halford J, Cunningham CL, Perrin BJ, Barr-Gillespie PG. Control of stereocilia length during development of hair bundles. PLoS Biol 2023; 21:e3001964. [PMID: 37011103 PMCID: PMC10101650 DOI: 10.1371/journal.pbio.3001964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 04/13/2023] [Accepted: 03/14/2023] [Indexed: 04/05/2023] Open
Abstract
Assembly of the hair bundle, the sensory organelle of the inner ear, depends on differential growth of actin-based stereocilia. Separate rows of stereocilia, labeled 1 through 3 from tallest to shortest, lengthen or shorten during discrete time intervals during development. We used lattice structured illumination microscopy and surface rendering to measure dimensions of stereocilia from mouse apical inner hair cells during early postnatal development; these measurements revealed a sharp transition at postnatal day 8 between stage III (row 1 and 2 widening; row 2 shortening) and stage IV (final row 1 lengthening and widening). Tip proteins that determine row 1 lengthening did not accumulate simultaneously during stages III and IV; while the actin-bundling protein EPS8 peaked at the end of stage III, GNAI3 peaked several days later-in early stage IV-and GPSM2 peaked near the end of stage IV. To establish the contributions of key macromolecular assemblies to bundle structure, we examined mouse mutants that eliminated tip links (Cdh23v2J or Pcdh15av3J), transduction channels (TmieKO), or the row 1 tip complex (Myo15ash2). Cdh23v2J/v2J and Pcdh15av3J/av3J bundles had adjacent stereocilia in the same row that were not matched in length, revealing that a major role of these cadherins is to synchronize lengths of side-by-side stereocilia. Use of the tip-link mutants also allowed us to distinguish the role of transduction from effects of transduction proteins themselves. While levels of GNAI3 and GPSM2, which stimulate stereocilia elongation, were greatly attenuated at the tips of TmieKO/KO row 1 stereocilia, they accumulated normally in Cdh23v2J/v2J and Pcdh15av3J/av3J stereocilia. These results reinforced the suggestion that the transduction proteins themselves facilitate localization of proteins in the row 1 complex. By contrast, EPS8 concentrates at tips of all TmieKO/KO, Cdh23v2J/v2J, and Pcdh15av3J/av3J stereocilia, correlating with the less polarized distribution of stereocilia lengths in these bundles. These latter results indicated that in wild-type hair cells, the transduction complex prevents accumulation of EPS8 at the tips of shorter stereocilia, causing them to shrink (rows 2 and 3) or disappear (row 4 and microvilli). Reduced rhodamine-actin labeling at row 2 stereocilia tips of tip-link and transduction mutants suggests that transduction's role is to destabilize actin filaments there. These results suggest that regulation of stereocilia length occurs through EPS8 and that CDH23 and PCDH15 regulate stereocilia lengthening beyond their role in gating mechanotransduction channels.
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Affiliation(s)
- Jocelyn F. Krey
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Paroma Chatterjee
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Julia Halford
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Christopher L. Cunningham
- Pittsburgh Hearing Research Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Benjamin J. Perrin
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, United States of America
| | - Peter G. Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America
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Nuclear Translocation Triggered at the Onset of Hearing in Cochlear Inner Hair Cells of Rats and Mice. J Assoc Res Otolaryngol 2023:10.1007/s10162-023-00894-2. [PMID: 36932316 DOI: 10.1007/s10162-023-00894-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 02/21/2023] [Indexed: 03/19/2023] Open
Abstract
PURPOSE Nuclear position is precisely orchestrated during cell division, migration, and maturation of cells and tissues. Here we report a previously unrecognized, programmed movement of the nucleus in rat and mouse cochlear inner hair cells (IHCs) coinciding with the functional maturation of inner hair cells around the onset of hearing. METHODS We measured hair cell length and nuclear position from confocal scans of immunofluorescence-labeled hair cells from whole-mount cochlear preparations throughout post-natal development. RESULTS In early post-natal days, the IHC experiences a period of sustained growth, during which the nucleus sits at the very basal pole of the cell, far from the apically located mechano-transducing stereocilia, but close to where synapses with primary afferent and efferent neurons are forming. After IHCs reach their final length, the nucleus moves to occupy a new position half-way along the length of the cell. Nuclear translocation begins in the middle turn, completes throughout the cochlea within 2-3 days, and coincides with the emergence of endolymphatic potential, the acquisition of big-conductance potassium channels (BK), and the onset of acoustic hearing. IHCs cultured in-vitro without endolymphatic potential (EP) do not grow, do not express BK, and do not experience nuclear movement. IHCs cultured in high K+ solutions (to simulate EP) grow but do not experience nuclear movement or acquire BK channels. CONCLUSION Nuclear migration at the onset of hearing is a key step in the morphological maturation of IHCs. Whether this plays a role in functional maturation remains to be explored.
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Yang Y, Murtha K, Climer LK, Ceriani F, Thompson P, Hornak AJ, Marcotti W, Simmons DD. Oncomodulin Regulates Spontaneous Calcium Signaling and Maturation of Afferent Innervation in Cochlear Outer Hair Cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.01.529895. [PMID: 36909575 PMCID: PMC10002690 DOI: 10.1101/2023.03.01.529895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
Cochlear outer hair cells (OHCs) are responsible for the exquisite frequency selectivity and sensitivity of mammalian hearing. During development, the maturation of OHC afferent connectivity is refined by coordinated spontaneous Ca 2+ activity in both sensory and non-sensory cells. Calcium signaling in neonatal OHCs can be modulated by Oncomodulin (OCM, β-parvalbumin), an EF-hand calcium-binding protein. Here, we investigated whether OCM regulates OHC spontaneous Ca 2+ activity and afferent connectivity during development. Using a genetically encoded Ca 2+ sensor (GCaMP6s) expressed in OHCs in wild-type (Ocm +/+ ) and Ocm knockout (Ocm -/- ) littermates, we found increased spontaneous Ca 2+ activity and upregulation of purinergic receptors in OHCs from GCaMP6s Ocm -/- cochlea immediately following birth. The afferent synaptic maturation of OHCs was delayed in the absence of OCM, leading to an increased number of ribbon synapses and afferent fibers on GCaMP6s Ocm -/- OHCs before hearing onset. We propose that OCM regulates the spontaneous Ca 2+ signaling in the developing cochlea and the maturation of OHC afferent innervation.
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10
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Iyer AA, Hosamani I, Nguyen JD, Cai T, Singh S, McGovern MM, Beyer L, Zhang H, Jen HI, Yousaf R, Birol O, Sun JJ, Ray RS, Raphael Y, Segil N, Groves AK. Cellular reprogramming with ATOH1, GFI1, and POU4F3 implicate epigenetic changes and cell-cell signaling as obstacles to hair cell regeneration in mature mammals. eLife 2022; 11:e79712. [PMID: 36445327 PMCID: PMC9708077 DOI: 10.7554/elife.79712] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 11/16/2022] [Indexed: 11/30/2022] Open
Abstract
Reprogramming of the cochlea with hair-cell-specific transcription factors such as ATOH1 has been proposed as a potential therapeutic strategy for hearing loss. ATOH1 expression in the developing cochlea can efficiently induce hair cell regeneration but the efficiency of hair cell reprogramming declines rapidly as the cochlea matures. We developed Cre-inducible mice to compare hair cell reprogramming with ATOH1 alone or in combination with two other hair cell transcription factors, GFI1 and POU4F3. In newborn mice, all transcription factor combinations tested produced large numbers of cells with the morphology of hair cells and rudimentary mechanotransduction properties. However, 1 week later, only a combination of ATOH1, GFI1 and POU4F3 could reprogram non-sensory cells of the cochlea to a hair cell fate, and these new cells were less mature than cells generated by reprogramming 1 week earlier. We used scRNA-seq and combined scRNA-seq and ATAC-seq to suggest at least two impediments to hair cell reprogramming in older animals. First, hair cell gene loci become less epigenetically accessible in non-sensory cells of the cochlea with increasing age. Second, signaling from hair cells to supporting cells, including Notch signaling, can prevent reprogramming of many supporting cells to hair cells, even with three hair cell transcription factors. Our results shed light on the molecular barriers that must be overcome to promote hair cell regeneration in the adult cochlea.
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Affiliation(s)
- Amrita A Iyer
- Department of Molecular & Human Genetics, Baylor College of MedicineHoustonUnited States
| | - Ishwar Hosamani
- Department of Molecular & Human Genetics, Baylor College of MedicineHoustonUnited States
| | - John D Nguyen
- Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine of the University of Southern California, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Biology at USCLos AngelesUnited States
| | - Tiantian Cai
- Program in Developmental Biology, Baylor College of MedicineHoustonUnited States
| | - Sunita Singh
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
| | - Melissa M McGovern
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
| | - Lisa Beyer
- Department of Otolaryngology-Head and Neck Surgery, University of MichiganAnn ArborUnited States
| | - Hongyuan Zhang
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
| | - Hsin-I Jen
- Program in Developmental Biology, Baylor College of MedicineHoustonUnited States
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
| | - Rizwan Yousaf
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
| | - Onur Birol
- Program in Developmental Biology, Baylor College of MedicineHoustonUnited States
| | - Jenny J Sun
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
| | - Russell S Ray
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
| | - Yehoash Raphael
- Department of Otolaryngology-Head and Neck Surgery, University of MichiganAnn ArborUnited States
| | - Neil Segil
- Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine of the University of Southern California, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Biology at USCLos AngelesUnited States
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern CaliforniaLos AngelesUnited States
| | - Andrew K Groves
- Department of Molecular & Human Genetics, Baylor College of MedicineHoustonUnited States
- Program in Developmental Biology, Baylor College of MedicineHoustonUnited States
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
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11
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Qiu X, Müller U. Sensing sound: Cellular specializations and molecular force sensors. Neuron 2022; 110:3667-3687. [PMID: 36223766 PMCID: PMC9671866 DOI: 10.1016/j.neuron.2022.09.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/03/2022] [Accepted: 09/14/2022] [Indexed: 11/08/2022]
Abstract
Organisms of all phyla express mechanosensitive ion channels with a wide range of physiological functions. In recent years, several classes of mechanically gated ion channels have been identified. Some of these ion channels are intrinsically mechanosensitive. Others depend on accessory proteins to regulate their response to mechanical force. The mechanotransduction machinery of cochlear hair cells provides a particularly striking example of a complex force-sensing machine. This molecular ensemble is embedded into a specialized cellular compartment that is crucial for its function. Notably, mechanotransduction channels of cochlear hair cells are not only critical for auditory perception. They also shape their cellular environment and regulate the development of auditory circuitry. Here, we summarize recent discoveries that have shed light on the composition of the mechanotransduction machinery of cochlear hair cells and how this machinery contributes to the development and function of the auditory system.
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Affiliation(s)
- Xufeng Qiu
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ulrich Müller
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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12
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Chen J, Gao D, Sun L, Yang J. Kölliker’s organ-supporting cells and cochlear auditory development. Front Mol Neurosci 2022; 15:1031989. [PMID: 36304996 PMCID: PMC9592740 DOI: 10.3389/fnmol.2022.1031989] [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: 08/30/2022] [Accepted: 09/23/2022] [Indexed: 11/21/2022] Open
Abstract
The Kölliker’s organ is a transient cellular cluster structure in the development of the mammalian cochlea. It gradually degenerates from embryonic columnar cells to cuboidal cells in the internal sulcus at postnatal day 12 (P12)–P14, with the cochlea maturing when the degeneration of supporting cells in the Kölliker’s organ is complete, which is distinct from humans because it disappears at birth already. The supporting cells in the Kölliker’s organ play a key role during this critical period of auditory development. Spontaneous release of ATP induces an increase in intracellular Ca2+ levels in inner hair cells in a paracrine form via intercellular gap junction protein hemichannels. The Ca2+ further induces the release of the neurotransmitter glutamate from the synaptic vesicles of the inner hair cells, which subsequently excite afferent nerve fibers. In this way, the supporting cells in the Kölliker’s organ transmit temporal and spatial information relevant to cochlear development to the hair cells, promoting fine-tuned connections at the synapses in the auditory pathway, thus facilitating cochlear maturation and auditory acquisition. The Kölliker’s organ plays a crucial role in such a scenario. In this article, we review the morphological changes, biological functions, degeneration, possible trans-differentiation of cochlear hair cells, and potential molecular mechanisms of supporting cells in the Kölliker’s organ during the auditory development in mammals, as well as future research perspectives.
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Affiliation(s)
- Jianyong Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Institute of Ear Science, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Otolaryngology and Translational Medicine, Shanghai, China
| | - Dekun Gao
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Institute of Ear Science, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Otolaryngology and Translational Medicine, Shanghai, China
| | - Lianhua Sun
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Institute of Ear Science, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Otolaryngology and Translational Medicine, Shanghai, China
- *Correspondence: Lianhua Sun Jun Yang
| | - Jun Yang
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Institute of Ear Science, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Otolaryngology and Translational Medicine, Shanghai, China
- *Correspondence: Lianhua Sun Jun Yang
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13
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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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14
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Ballesteros A, Swartz KJ. Regulation of membrane homeostasis by TMC1 mechanoelectrical transduction channels is essential for hearing. SCIENCE ADVANCES 2022; 8:eabm5550. [PMID: 35921424 PMCID: PMC9348795 DOI: 10.1126/sciadv.abm5550] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The mechanoelectrical transduction (MET) channel in auditory hair cells converts sound into electrical signals, enabling hearing. Transmembrane-like channel 1 and 2 (TMC1 and TMC2) are implicated in forming the pore of the MET channel. Here, we demonstrate that inhibition of MET channels, breakage of the tip links required for MET, or buffering of intracellular Ca... induces pronounced phosphatidylserine externalization, membrane blebbing, and ectosome release at the hair cell sensory organelle, culminating in the loss of TMC1. Membrane homeostasis triggered by MET channel inhibition requires Tmc1 but not Tmc2, and three deafness-causing mutations in Tmc1 cause constitutive phosphatidylserine externalization that correlates with deafness phenotype. Our results suggest that, in addition to forming the pore of the MET channel, TMC1 is a critical regulator of membrane homeostasis in hair cells, and that Tmc1-related hearing loss may involve alterations in membrane homeostasis.
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15
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Abstract
It is well established that humans and other mammals are minimally regenerative compared with organisms such as zebrafish, salamander or amphibians. In recent years, however, the identification of regenerative potential in neonatal mouse tissues that normally heal poorly in adults has transformed our understanding of regenerative capacity in mammals. In this Review, we survey the mammalian tissues for which regenerative or improved neonatal healing has been established, including the heart, cochlear hair cells, the brain and spinal cord, and dense connective tissues. We also highlight common and/or tissue-specific mechanisms of neonatal regeneration, which involve cells, signaling pathways, extracellular matrix, immune cells and other factors. The identification of such common features across neonatal tissues may direct therapeutic strategies that will be broadly applicable to multiple adult tissues.
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Affiliation(s)
| | - Alice H. Huang
- Department of Orthopedic Surgery, Columbia University, New York, NY 10032, USA
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16
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Caprara GA, Peng AW. Mechanotransduction in mammalian sensory hair cells. Mol Cell Neurosci 2022; 120:103706. [PMID: 35218890 PMCID: PMC9177625 DOI: 10.1016/j.mcn.2022.103706] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 02/14/2022] [Accepted: 02/18/2022] [Indexed: 11/23/2022] Open
Abstract
In the inner ear, the auditory and vestibular systems detect and translate sensory information regarding sound and balance. The sensory cells that transform mechanical input into an electrical signal in these systems are called hair cells. A specialized organelle on the apical surface of hair cells called the hair bundle detects mechanical signals. Displacement of the hair bundle causes mechanotransduction channels to open. The morphology and organization of the hair bundle, as well as the properties and characteristics of the mechanotransduction process, differ between the different hair cell types in the auditory and vestibular systems. These differences likely contribute to maximizing the transduction of specific signals in each system. This review will discuss the molecules essential for mechanotransduction and the properties of the mechanotransduction process, focusing our attention on recent data and differences between the auditory and vestibular systems.
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Affiliation(s)
- Giusy A Caprara
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States of America
| | - Anthony W Peng
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States of America.
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17
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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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18
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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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19
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Tu H, Zhang A, Fu X, Xu S, Bai X, Wang H, Gao J. SMPX Deficiency Causes Stereocilia Degeneration and Progressive Hearing Loss in CBA/CaJ Mice. Front Cell Dev Biol 2021; 9:750023. [PMID: 34722533 PMCID: PMC8551870 DOI: 10.3389/fcell.2021.750023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/17/2021] [Indexed: 11/13/2022] Open
Abstract
The small muscle protein, x-linked (SMPX) encodes a small protein containing 88 amino acids. Malfunction of this protein can cause a sex-linked non-syndromic hearing loss, named X-linked deafness 4 (DFNX4). Herein, we reported a point mutation and a frameshift mutation in two Chinese families who developed gradual hearing loss with age. To explore the impaired sites in the hearing system and the mechanism of DFNX4, we established and validated an Smpx null mouse model using CRISPR-Cas9. By analyzing auditory brainstem response (ABR), male Smpx null mice showed a progressive hearing loss starting from high frequency at the 3rd month. Hearing loss in female mice was milder and occurred later compared to male mice, which was very similar to human beings. Through morphological analyses of mice cochleas, we found the hair cell bundles progressively degenerated from the shortest row. Cellular edema occurred at the end phase of stereocilia degeneration, followed by cell death. By transfecting exogenous fluorescent Smpx into living hair cells, Smpx was observed to be expressed in stereocilia. Through noise exposure, it was shown that Smpx might participate in maintaining hair cell bundles. This Smpx knock-out mouse might be used as a suitable model to explore the pathology of DFNX4.
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Affiliation(s)
- Hailong Tu
- School of Life Sciences, Shandong Provincial ENT Hospital, Shandong University, Jinan, China
| | - Aizhen Zhang
- School of Life Sciences, Shandong Provincial ENT Hospital, Shandong University, Jinan, China
| | - Xiaolong Fu
- School of Life Sciences, Shandong Provincial ENT Hospital, Shandong University, Jinan, China
| | - Shiqi Xu
- University of Edinburgh Institute, Zhejiang University School of Medicine, Zhejiang University, Haining, China
| | - Xiaohui Bai
- Otolaryngology-Head and Neck Surgery, Shandong Provincial ENT Hospital, Jinan, China
| | - Haibo Wang
- School of Life Sciences, Shandong Provincial ENT Hospital, Shandong University, Jinan, China.,Otolaryngology-Head and Neck Surgery, Shandong Provincial ENT Hospital, Jinan, China
| | - Jiangang Gao
- School of Life Sciences, Shandong Provincial ENT Hospital, Shandong University, Jinan, China
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20
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Abstract
PURPOSE OF REVIEW We review recent progress in the characterization of spiral ganglion neurons (SGNs), the afferent neurons that transmit sound information from mechanosensory hair cells in the inner ear to the central nervous system. RECENT FINDINGS Single-cell ribonucleic acid sequencing studies of murine SGNs have demonstrated that SGNs consist of molecularly distinct subtypes. The molecularly defined SGN subtypes likely correspond to SGN subtypes previously identified on the basis of physiological properties, although this has not been experimentally demonstrated. Subtype maturation is completed postnatally in an activity-dependent manner and is impaired in several models of hearing loss. SUMMARY The recent molecular studies open new avenues to rigorously test whether SGN subtypes are important for the encoding of different sound features and if they show differential vulnerability to genetic factors and environmental insults. This could have important implications for the development of therapeutic strategies to treat hearing loss.
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Affiliation(s)
- Shuohao Sun
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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21
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Liu S, Wang S, Zou L, Xiong W. Mechanisms in cochlear hair cell mechano-electrical transduction for acquisition of sound frequency and intensity. Cell Mol Life Sci 2021; 78:5083-5094. [PMID: 33871677 PMCID: PMC11072359 DOI: 10.1007/s00018-021-03840-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 03/30/2021] [Accepted: 04/09/2021] [Indexed: 10/21/2022]
Abstract
Sound signals are acquired and digitized in the cochlea by the hair cells that further transmit the coded information to the central auditory pathways. Any defect in hair cell function may induce problems in the auditory system and hearing-based brain function. In the past 2 decades, our understanding of auditory transduction has been substantially deepened because of advances in molecular, structural, and functional studies. Results from these experiments can be perfectly embedded in the previously established profile from anatomical, histological, genetic, and biophysical research. This review aims to summarize the progress on the molecular and cellular mechanisms of the mechano-electrical transduction (MET) channel in the cochlear hair cells, which is involved in the acquisition of sound frequency and intensity-the two major parameters of an acoustic cue. We also discuss recent studies on TMC1, the molecule likely to form the MET channel pore.
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Affiliation(s)
- Shuang Liu
- School of Life Sciences, Tsinghua University, 1 Qinghuayuan, Beijing, 100084, China
- IDG/McGovern Institute for Brain Research at Tsinghua University, Tsinghua University, 1 Qinghuayuan, Beijing, 100084, China
| | - Shufeng Wang
- School of Life Sciences, Tsinghua University, 1 Qinghuayuan, Beijing, 100084, China
- IDG/McGovern Institute for Brain Research at Tsinghua University, Tsinghua University, 1 Qinghuayuan, Beijing, 100084, China
| | - Linzhi Zou
- School of Life Sciences, Tsinghua University, 1 Qinghuayuan, Beijing, 100084, China
- IDG/McGovern Institute for Brain Research at Tsinghua University, Tsinghua University, 1 Qinghuayuan, Beijing, 100084, China
| | - Wei Xiong
- School of Life Sciences, Tsinghua University, 1 Qinghuayuan, Beijing, 100084, China.
- IDG/McGovern Institute for Brain Research at Tsinghua University, Tsinghua University, 1 Qinghuayuan, Beijing, 100084, China.
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22
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Abstract
Sound-induced mechanical stimuli are detected by elaborate mechanosensory transduction (MT) machinery in highly specialized hair cells of the inner ear. Genetic studies of inherited deafness in the past decades have uncovered several molecular constituents of the MT complex, and intense debate has surrounded the molecular identity of the pore-forming subunits. How the MT components function in concert in response to physical stimulation is not fully understood. In this review, we summarize and discuss multiple lines of evidence supporting the hypothesis that transmembrane channel-like 1 is a long-sought MT channel subunit. We also review specific roles of other components of the MT complex, including protocadherin 15, cadherin 23, lipoma HMGIC fusion partner-like 5, transmembrane inner ear, calcium and integrin-binding family member 2, and ankyrins. Based on these recent advances, we propose a unifying theory of hair cell MT that may reconcile most of the functional discoveries obtained to date. Finally, we discuss key questions that need to be addressed for a comprehensive understanding of hair cell MT at molecular and atomic levels.
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Affiliation(s)
- Wang Zheng
- Departments of Otolaryngology and Neurology, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA;
| | - Jeffrey R Holt
- Departments of Otolaryngology and Neurology, Boston Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA;
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23
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Wang S, Lee MP, Jones S, Liu J, Waldhaus J. Mapping the regulatory landscape of auditory hair cells from single-cell multi-omics data. Genome Res 2021; 31:1885-1899. [PMID: 33837132 DOI: 10.1101/gr.271080.120] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 03/23/2021] [Indexed: 11/25/2022]
Abstract
Auditory hair cells transduce sound to the brain and in mammals these cells reside together with supporting cells in the sensory epithelium of the cochlea, called the organ of Corti. To establish the organ's delicate function during development and differentiation, spatiotemporal gene expression is strictly controlled by chromatin accessibility and cell type-specific transcription factors, jointly representing the regulatory landscape. Bulk-sequencing technology and cellular heterogeneity obscured investigations on the interplay between transcription factors and chromatin accessibility in inner ear development. To study the formation of the regulatory landscape in hair cells, we collected single-cell chromatin accessibility profiles accompanied by single-cell RNA data from genetically labeled murine hair cells and supporting cells after birth. Using an integrative approach, we predicted cell type-specific activating and repressing functions of developmental transcription factors. Furthermore, by integrating gene expression and chromatin accessibility datasets, we reconstructed gene regulatory networks. Then, using a comparative approach, 20 hair cell-specific activators and repressors, including putative downstream target genes, were identified. Clustering of target genes resolved groups of related transcription factors and was utilized to infer their developmental functions. Finally, the heterogeneity in the single-cell data allowed us to spatially reconstruct transcriptional as well as chromatin accessibility trajectories, indicating that gradual changes in the chromatin accessibility landscape were lagging behind the transcriptional identity of hair cells along the organ's longitudinal axis. Overall, this study provides a strategy to spatially reconstruct the formation of a lineage specific regulatory landscape using a single-cell multi-omics approach.
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Affiliation(s)
- Shuze Wang
- University of Michigan, Kresge Hearing Research Institute
| | - Mary P Lee
- University of Michigan, Kresge Hearing Research Institute
| | - Scott Jones
- University of Michigan, Kresge Hearing Research Institute
| | | | - Joerg Waldhaus
- University of Michigan, Kresge Hearing Research Institute;
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24
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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: 12] [Impact Index Per Article: 4.0] [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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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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26
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Marcovich I, Holt JR. Evolution and function of Tmc genes in mammalian hearing. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2020.06.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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The Notch Ligand Jagged1 Is Required for the Formation, Maintenance, and Survival of Hensen's Cells in the Mouse Cochlea. J Neurosci 2020; 40:9401-9413. [PMID: 33127852 DOI: 10.1523/jneurosci.1192-20.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 10/16/2020] [Accepted: 10/23/2020] [Indexed: 01/09/2023] Open
Abstract
During cochlear development, the Notch ligand JAGGED 1 (JAG1) plays an important role in the specification of the prosensory region, which gives rise to sound-sensing hair cells and neighboring supporting cells (SCs). While JAG1's expression is maintained in SCs through adulthood, the function of JAG1 in SC development is unknown. Here, we demonstrate that JAG1 is essential for the formation and maintenance of Hensen's cells, a highly specialized SC subtype located at the edge of the auditory epithelium. Using Sox2 CreERT2/+::Jag1loxP/loxP mice of both genders, we show that Jag1 deletion at the onset of differentiation, at embryonic day 14.5, disrupted Hensen's cell formation. Similar loss of Hensen's cells was observed when Jag1 was deleted after Hensen's cell formation at postnatal day (P) 0/P1 and fate-mapping analysis revealed that in the absence of Jag1, some Hensen's cells die, but others convert into neighboring Claudius cells. In support of a role for JAG1 in cell survival, genes involved in mitochondrial function and protein synthesis were downregulated in the sensory epithelium of P0 cochlea lacking Jag1 Finally, using Fgfr3-iCreERT2 ::Jag1loxP/loxP mice to delete Jag1 at P0, we observed a similar loss of Hensen's cells and found that adult Jag1 mutant mice have hearing deficits at the low-frequency range.SIGNIFICANCE STATEMENT Hensen's cells play an essential role in the development and homeostasis of the cochlea. Defects in the biophysical or functional properties of Hensen's cells have been linked to auditory dysfunction and hearing loss. Despite their importance, surprisingly little is known about the molecular mechanisms that guide their development. Morphologic and fate-mapping analyses in our study revealed that, in the absence of the Notch ligand JAGGED1, Hensen's cells died or converted into Claudius cells, which are specialized epithelium-like cells outside the sensory epithelium. Confirming a link between JAGGED1 and cell survival, transcriptional profiling showed that JAGGED1 maintains genes critical for mitochondrial function and tissue homeostasis. Finally, auditory phenotyping revealed that JAGGED1's function in supporting cells is necessary for low-frequency hearing.
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Interaction of protocadherin-15 with the scaffold protein whirlin supports its anchoring of hair-bundle lateral links in cochlear hair cells. Sci Rep 2020; 10:16430. [PMID: 33009420 PMCID: PMC7532178 DOI: 10.1038/s41598-020-73158-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 09/07/2020] [Indexed: 11/26/2022] Open
Abstract
The hair bundle of cochlear hair cells is the site of auditory mechanoelectrical transduction. It is formed by three rows of stiff microvilli-like protrusions of graduated heights, the short, middle-sized, and tall stereocilia. In developing and mature sensory hair cells, stereocilia are connected to each other by various types of fibrous links. Two unconventional cadherins, protocadherin-15 (PCDH15) and cadherin-23 (CDH23), form the tip-links, whose tension gates the hair cell mechanoelectrical transduction channels. These proteins also form transient lateral links connecting neighboring stereocilia during hair bundle morphogenesis. The proteins involved in anchoring these diverse links to the stereocilia dense actin cytoskeleton remain largely unknown. We show that the long isoform of whirlin (L-whirlin), a PDZ domain-containing submembrane scaffold protein, is present at the tips of the tall stereocilia in mature hair cells, together with PCDH15 isoforms CD1 and CD2; L-whirlin localization to the ankle-link region in developing hair bundles moreover depends on the presence of PCDH15-CD1 also localizing there. We further demonstrate that L-whirlin binds to PCDH15 and CDH23 with moderate-to-high affinities in vitro. From these results, we suggest that L-whirlin is part of the molecular complexes bridging PCDH15-, and possibly CDH23-containing lateral links to the cytoskeleton in immature and mature stereocilia.
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29
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LIN28B/ let-7 control the ability of neonatal murine auditory supporting cells to generate hair cells through mTOR signaling. Proc Natl Acad Sci U S A 2020; 117:22225-22236. [PMID: 32826333 DOI: 10.1073/pnas.2000417117] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mechano-sensory hair cells within the inner ear cochlea are essential for the detection of sound. In mammals, cochlear hair cells are only produced during development and their loss, due to disease or trauma, is a leading cause of deafness. In the immature cochlea, prior to the onset of hearing, hair cell loss stimulates neighboring supporting cells to act as hair cell progenitors and produce new hair cells. However, for reasons unknown, such regenerative capacity (plasticity) is lost once supporting cells undergo maturation. Here, we demonstrate that the RNA binding protein LIN28B plays an important role in the production of hair cells by supporting cells and provide evidence that the developmental drop in supporting cell plasticity in the mammalian cochlea is, at least in part, a product of declining LIN28B-mammalian target of rapamycin (mTOR) activity. Employing murine cochlear organoid and explant cultures to model mitotic and nonmitotic mechanisms of hair cell generation, we show that loss of LIN28B function, due to its conditional deletion, or due to overexpression of the antagonistic miRNA let-7g, suppressed Akt-mTOR complex 1 (mTORC1) activity and renders young, immature supporting cells incapable of generating hair cells. Conversely, we found that LIN28B overexpression increased Akt-mTORC1 activity and allowed supporting cells that were undergoing maturation to de-differentiate into progenitor-like cells and to produce hair cells via mitotic and nonmitotic mechanisms. Finally, using the mTORC1 inhibitor rapamycin, we demonstrate that LIN28B promotes supporting cell plasticity in an mTORC1-dependent manner.
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Abstract
Mechanosensory bundles on auditory sensory cells are composed of stereocilia that grow in rows of decreasing height. This pattern depends on the specification of the eventual tallest row, then the assignment of distinct molecular identities to the shorter rows. Mechanotransduction refines and maintains row identity, thus instructing the form of the bundle.
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Affiliation(s)
- Jamis McGrath
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Benjamin J Perrin
- Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA.
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31
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Markowitz AL, Kalluri R. Gradients in the biophysical properties of neonatal auditory neurons align with synaptic contact position and the intensity coding map of inner hair cells. eLife 2020; 9:e55378. [PMID: 32639234 PMCID: PMC7343388 DOI: 10.7554/elife.55378] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 06/24/2020] [Indexed: 02/07/2023] Open
Abstract
Sound intensity is encoded by auditory neuron subgroups that differ in thresholds and spontaneous rates. Whether variations in neuronal biophysics contributes to this functional diversity is unknown. Because intensity thresholds correlate with synaptic position on sensory hair cells, we combined patch clamping with fiber labeling in semi-intact cochlear preparations in neonatal rats from both sexes. The biophysical properties of auditory neurons vary in a striking spatial gradient with synaptic position. Neurons with high thresholds to injected currents contact hair cells at synaptic positions where neurons with high thresholds to sound-intensity are found in vivo. Alignment between in vitro and in vivo thresholds suggests that biophysical variability contributes to intensity coding. Biophysical gradients were evident at all ages examined, indicating that cell diversity emerges in early post-natal development and persists even after continued maturation. This stability enabled a remarkably successful model for predicting synaptic position based solely on biophysical properties.
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Affiliation(s)
- Alexander L Markowitz
- Neuroscience Graduate Program, University of Southern CaliforniaLos AngelesUnited States
- Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
| | - Radha Kalluri
- Neuroscience Graduate Program, University of Southern CaliforniaLos AngelesUnited States
- Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
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32
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Menendez L, Trecek T, Gopalakrishnan S, Tao L, Markowitz AL, Yu HV, Wang X, Llamas J, Huang C, Lee J, Kalluri R, Ichida J, Segil N. Generation of inner ear hair cells by direct lineage conversion of primary somatic cells. eLife 2020; 9:e55249. [PMID: 32602462 PMCID: PMC7326493 DOI: 10.7554/elife.55249] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 05/27/2020] [Indexed: 02/06/2023] Open
Abstract
The mechanoreceptive sensory hair cells in the inner ear are selectively vulnerable to numerous genetic and environmental insults. In mammals, hair cells lack regenerative capacity, and their death leads to permanent hearing loss and vestibular dysfunction. Their paucity and inaccessibility has limited the search for otoprotective and regenerative strategies. Growing hair cells in vitro would provide a route to overcome this experimental bottleneck. We report a combination of four transcription factors (Six1, Atoh1, Pou4f3, and Gfi1) that can convert mouse embryonic fibroblasts, adult tail-tip fibroblasts and postnatal supporting cells into induced hair cell-like cells (iHCs). iHCs exhibit hair cell-like morphology, transcriptomic and epigenetic profiles, electrophysiological properties, mechanosensory channel expression, and vulnerability to ototoxin in a high-content phenotypic screening system. Thus, direct reprogramming provides a platform to identify causes and treatments for hair cell loss, and may help identify future gene therapy approaches for restoring hearing.
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Affiliation(s)
- Louise Menendez
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
| | - Talon Trecek
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | - Suhasni Gopalakrishnan
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
| | - Litao Tao
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | - Alexander L Markowitz
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
- USC Caruso Department of Otolaryngology – Head and Neck Surgery, University of Southern CaliforniaLos AngelesUnited States
| | - Haoze V Yu
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | - Xizi Wang
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | - Juan Llamas
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | | | - James Lee
- DRVision TechnologiesBellevueUnited States
| | - Radha Kalluri
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
- USC Caruso Department of Otolaryngology – Head and Neck Surgery, University of Southern CaliforniaLos AngelesUnited States
| | - Justin Ichida
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
| | - Neil Segil
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
- USC Caruso Department of Otolaryngology – Head and Neck Surgery, University of Southern CaliforniaLos AngelesUnited States
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Functional Postnatal Maturation of the Medial Olivocochlear Efferent-Outer Hair Cell Synapse. J Neurosci 2020; 40:4842-4857. [PMID: 32430293 DOI: 10.1523/jneurosci.2409-19.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 04/19/2020] [Accepted: 05/11/2020] [Indexed: 01/07/2023] Open
Abstract
The organ of Corti, the auditory mammalian sensory epithelium, contains two types of mechanotransducer cells, inner hair cells (IHCs) and outer hair cells (OHCs). IHCs are involved in conveying acoustic stimuli to the CNS, while OHCs are implicated in the fine tuning and amplification of sounds. OHCs are innervated by medial olivocochlear (MOC) cholinergic efferent fibers. The functional characteristics of the MOC-OHC synapse during maturation were assessed by electrophysiological and pharmacological methods in mouse organs of Corti at postnatal day 11 (P11)-P13, hearing onset in altricial rodents, and at P20-P22 when the OHCs are morphologically and functionally mature. Synaptic currents were recorded in whole-cell voltage-clamped OHCs while electrically stimulating the MOC fibers. A progressive increase in the number of functional MOC-OHC synapses, as well as in their strength and efficacy, was observed between P11-13 and P20-22. At hearing onset, the MOC-OHC synapse presented facilitation during MOC fibers high-frequency stimulation that disappeared at mature stages. In addition, important changes were found in the VGCC that are coupled to transmitter release. Ca2+ flowing in through L-type VGCCs contribute to trigger ACh release together with P/Q- and R-type VGCCs at P11-P13, but not at P20-P22. Interestingly, N-type VGCCs were found to be involved in this process at P20-P22, but not at hearing onset. Moreover, the degree of compartmentalization of calcium channels with respect to BK channels and presynaptic release components significantly increased from P11-P13 to P20-P22. These results suggest that the MOC-OHC synapse is immature at the onset of hearing.SIGNIFICANCE STATEMENT The functional expression of both VGCCs and BK channels, as well as their localization with respect to the presynaptic components involved in transmitter release, are key elements in determining synaptic efficacy. In this work, we show dynamic changes in the expression of VGCCs and Ca2+-dependent BK K+ channels coupled to ACh release at the MOC-OHC synapse and their shift in compartmentalization during postnatal maturation. These processes most likely set the short-term plasticity pattern and reliability of the MOC-OHC synapse on high-frequency activity.
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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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35
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Systemic Fluorescent Gentamicin Enters Neonatal Mouse Hair Cells Predominantly Through Sensory Mechanoelectrical Transduction Channels. J Assoc Res Otolaryngol 2020; 21:137-149. [PMID: 32152768 DOI: 10.1007/s10162-020-00746-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Accepted: 02/10/2020] [Indexed: 01/25/2023] Open
Abstract
Systemically administered aminoglycoside antibiotics can enter inner ear hair cells and trigger apoptosis. However, the in vivo route(s) by which aminoglycoside antibiotics enter hair cells remains controversial. Aminoglycosides can enter mouse hair cells by endocytosis or by permeation through transmembrane ion channels such as sensory mechanoelectrical transduction (MET) channels, transient receptor potential (TRP) channels, P2X channels, Piezo2-containing ion channels, or a combination of these routes. Transmembrane channel-like 1 (TMC1) and TMC2 are essential for sensory MET and appear to be the pore-forming components of sensory MET channels. The present study tested the hypothesis that systemic fluorescent gentamicin enters mouse hair cells predominantly through sensory MET channels. We employed Tmc1Δ, Tmc2Δ, and Tmc1::mCherry mice. In Tmc1::mCherry mice, the transgene was integrated on the X chromosome, resulting in mosaic expression of TMC1-mCherry in the hair cells of female heterozygous mice. After systemic administration of gentamicin-conjugated Texas Red (GTTR) into Tmc1Δ;Tmc2Δ mice and wild-type mice at postnatal day 4 (P4), robust GTTR fluorescence was detected in wild-type hair cells, whereas little or no GTTR fluorescence was detected in Tmc1Δ;Tmc2Δ hair cells. When GTTR was injected into developing mice at P0, P2, P4, or P6, the GTTR fluorescent intensity gradually increased from P0 to P4 in wild-type hair cells, whereas the intensity was stably low from P0 through P6 in Tmc1Δ;Tmc2Δ hair cells. The increase in the GTTR intensity coincided with the spatio-temporal onset of sensory MET in wild-type hair cells. In Tmc1::mCherry cochleae, only hair cells that showed a significant uptake of systemic GTTR took up FM1-43. Transmission electron microscopy could detect no disruption of normal endocytosis at the apical surface of Tmc1Δ;Tmc2Δ hair cells in vitro. These results provide substantial novel evidence that in vivo gentamicin enters neonatal mouse hair cells predominantly through sensory MET channels and not via endocytosis.
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36
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Ballesteros A, Swartz KJ. Dextran Labeling and Uptake in Live and Functional Murine Cochlear Hair Cells. J Vis Exp 2020. [PMID: 32090986 PMCID: PMC11384666 DOI: 10.3791/60769] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The hair cell mechanotransduction (MET) channel plays an important role in hearing. However, the molecular identity and structural information of MET remain unknown. Electrophysiological studies of hair cells revealed that the MET channel has a large conductance and is permeable to relatively large fluorescent cationic molecules, including some styryl dyes and Texas Red-labeled aminoglycoside antibiotics. In this protocol, we describe a method to visualize and evaluate the uptake of fluorescent dextrans in hair cells of the organ of Corti explants that can be used to assay for functional MET channels. We found that 3 kDa Texas Red-labeled dextran specifically labels functional auditory hair cells after 1-2 h incubation. In particular, 3 kDa dextran labels the two shorter stereocilia rows and accumulates in the cell body in a diffuse pattern when functional MET channels are present. An additional vesicle-like pattern of labeling was observed in the cell body of hair cells and surrounding supporting cells. Our data suggest that 3 kDa Texas-Red dextran can be used to visualize and study two pathways for cellular dye uptake; a hair cell-specific entry route through functional MET channels and endocytosis, a pattern also available to larger dextran.
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Affiliation(s)
- Angela Ballesteros
- Molecular Physiology and Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health;
| | - Kenton J Swartz
- Molecular Physiology and Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health
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37
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Pisciottano F, Cinalli AR, Stopiello JM, Castagna VC, Elgoyhen AB, Rubinstein M, Gómez-Casati ME, Franchini LF. Inner Ear Genes Underwent Positive Selection and Adaptation in the Mammalian Lineage. Mol Biol Evol 2020; 36:1653-1670. [PMID: 31137036 DOI: 10.1093/molbev/msz077] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The mammalian inner ear possesses functional and morphological innovations that contribute to its unique hearing capacities. The genetic bases underlying the evolution of this mammalian landmark are poorly understood. We propose that the emergence of morphological and functional innovations in the mammalian inner ear could have been driven by adaptive molecular evolution. In this work, we performed a meta-analysis of available inner ear gene expression data sets in order to identify genes that show signatures of adaptive evolution in the mammalian lineage. We analyzed ∼1,300 inner ear expressed genes and found that 13% show signatures of positive selection in the mammalian lineage. Several of these genes are known to play an important function in the inner ear. In addition, we identified that a significant proportion of genes showing signatures of adaptive evolution in mammals have not been previously reported to participate in inner ear development and/or physiology. We focused our analysis in two of these genes: STRIP2 and ABLIM2 by generating null mutant mice and analyzed their auditory function. We found that mice lacking Strip2 displayed a decrease in neural response amplitudes. In addition, we observed a reduction in the number of afferent synapses, suggesting a potential cochlear neuropathy. Thus, this study shows the usefulness of pursuing a high-throughput evolutionary approach followed by functional studies to track down genes that are important for inner ear function. Moreover, this approach sheds light on the genetic bases underlying the evolution of the mammalian inner ear.
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Affiliation(s)
- Francisco Pisciottano
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Alejandro R Cinalli
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Juan Matías Stopiello
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Valeria C Castagna
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires,Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires, Buenos Aires,Argentina
| | - María Eugenia Gómez-Casati
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires,Argentina
| | - Lucía F Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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38
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Mechanotransduction-Dependent Control of Stereocilia Dimensions and Row Identity in Inner Hair Cells. Curr Biol 2020; 30:442-454.e7. [PMID: 31902726 DOI: 10.1016/j.cub.2019.11.076] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 11/08/2019] [Accepted: 11/26/2019] [Indexed: 02/07/2023]
Abstract
Actin-rich structures, like stereocilia and microvilli, are assembled with precise control of length, diameter, and relative spacing. By quantifying actin-core dimensions of stereocilia from phalloidin-labeled mouse cochleas, we demonstrated that inner hair cell stereocilia developed in specific stages, where a widening phase is sandwiched between two lengthening phases. Moreover, widening of the second-tallest stereocilia rank (row 2) occurred simultaneously with the appearance of mechanotransduction. Correspondingly, Tmc1KO/KO;Tmc2KO/KO or TmieKO/KO hair cells, which lack transduction, have significantly altered stereocilia lengths and diameters, including a narrowed row 2. EPS8 and the short splice isoform of MYO15A, identity markers for mature row 1 (the tallest row), lost their row exclusivity in transduction mutants. GNAI3, another member of the mature row 1 complex, accumulated at mutant row 1 tips at considerably lower levels than in wild-type bundles. Alterations in stereocilia dimensions and in EPS8 distribution seen in transduction mutants were mimicked by block of transduction channels of cochlear explants in culture. In addition, proteins normally concentrated at mature row 2 tips were also distributed differently in transduction mutants; the heterodimeric capping protein subunit CAPZB and its partner TWF2 never concentrated at row 2 tips like they do in wild-type bundles. The altered distribution of marker proteins in transduction mutants was accompanied by increased variability in stereocilia length. Transduction channels thus specify and maintain row identity, control addition of new actin filaments to increase stereocilia diameter, and coordinate stereocilia height within rows.
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39
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Yao Q, Wang L, Mittal R, Yan D, Richmond MT, Denyer S, Requena T, Liu K, Varshney GK, Lu Z, Liu XZ. Transcriptomic Analyses of Inner Ear Sensory Epithelia in Zebrafish. Anat Rec (Hoboken) 2019; 303:527-543. [PMID: 31883312 DOI: 10.1002/ar.24331] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 08/01/2019] [Accepted: 11/18/2019] [Indexed: 12/25/2022]
Abstract
Analysis of gene expression has the potential to assist in the understanding of multiple cellular processes including proliferation, cell-fate specification, senesence, and activity in both healthy and disease states. Zebrafish model has been increasingly used to understand the process of hearing and the development of the vertebrate auditory system. Within the zebrafish inner ear, there are three otolith organs, each containing a sensory macula of hair cells. The saccular macula is primarily involved in hearing, the utricular macula is primarily involved in balance and the function of the lagenar macula is not completely understood. The goal of this study is to understand the transcriptional differences in the sensory macula associated with different otolith organs with the intention of understanding the genetic mechanisms responsible for the distinct role each organ plays in sensory perception. The sensory maculae of the saccule, utricle, and lagena were dissected out of adult Et(krt4:GFP)sqet4 zebrafish expressing green fluorescent protein in hair cells for transcriptional analysis. The total RNAs of the maculae were isolated and analyzed by RNA GeneChip microarray. Several of the differentially expressed genes are known to be involved in deafness, otolith development and balance. Gene expression among these otolith organs was very well conserved with less than 10% of genes showing differential expression. Data from this study will help to elucidate which genes are involved in hearing and balance. Furthermore, the findings of this study will assist in the development of the zebrafish model for human hearing and balance disorders. Anat Rec, 303:527-543, 2020. © 2019 American Association for Anatomy.
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Affiliation(s)
- Qi Yao
- Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, Florida.,Department of Biology, University of Miami, Miami, Florida
| | - Lingyu Wang
- Department of Biology, University of Miami, Miami, Florida
| | - Rahul Mittal
- Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, Florida
| | - Denise Yan
- Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, Florida
| | | | - Steven Denyer
- Department of Biology, University of Miami, Miami, Florida
| | - Teresa Requena
- Genes & Human Disease Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma
| | - Kaili Liu
- Genes & Human Disease Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma
| | - Gaurav K Varshney
- Genes & Human Disease Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma
| | - Zhongmin Lu
- Department of Biology, University of Miami, Miami, Florida
| | - Xue Zhong Liu
- Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, Florida.,Department of Otolaryngology, Xiangya Hospital, Central South University, Changsha, Hunan, China
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40
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Goldring AC, Beurg M, Fettiplace R. The contribution of TMC1 to adaptation of mechanoelectrical transduction channels in cochlear outer hair cells. J Physiol 2019; 597:5949-5961. [PMID: 31633194 PMCID: PMC6910908 DOI: 10.1113/jp278799] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 10/17/2019] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS Hair cell mechanoelectrical transducer channels are opened by deflections of the hair bundle about a resting position set by incompletely understood adaptation mechanisms. We used three characteristics to define adaptation in hair cell mutants of transmembrane channel-like proteins, TMC1 and TMC2, which are considered to be channel constituents. The results obtained demonstrate that the three characteristics are not equivalent, and raise doubts about simple models in which intracellular Ca2+ regulates adaptation. Adaptation is faster and more effective in TMC1-containing than in TMC2-containing transducer channels. This result ties adaptation to the channel complex, and suggests that TMC1 is a better isoform for use in cochlear hair cells. We describe a TMC1 point mutation, D569N, that reduces the resting open probability and Ca2+ permeability of the transducer channels, comprising properties that may contribute to the deafness phenotype. ABSTRACT Recordings of mechanoelectrical transducer (MET) currents in cochlear hair cells were made in mice with mutations of transmembrane channel-like (TMC) protein to examine the effects on fast transducer adaptation. Adaptation was faster and more complete in Tmc2-/- than in Tmc1-/- , although this disparity was not explained by differences in Ca2+ permeability or Ca2+ influx between the two isoforms, with TMC2 having the larger permeability. We made a mouse mutation, Tmc1 p.D569N, homologous to a human DFNA36 deafness mutation, which also had MET channels with lower Ca2+ -permeability but showed better fast adaptation than wild-type Tmc1+/+ channels. Consistent with the more effective adaptation in Tmc1 p.D569N, the resting probability of MET channel opening was smaller. The three TMC variants studied have comparable single-channel conductances, although the lack of correlation between channel Ca2+ permeability and adaptation opposes the hypothesis that adaptation is controlled simply by Ca2+ influx through the channels. During the first postnatal week of mouse development, the MET currents amplitude grew, and transducer adaptation became faster and more effective. We attribute changes in adaptation partly to a developmental switch from TMC2- to TMC1- containing channels and partly to an increase in channel expression. More complete and faster adaptation, coupled with larger MET currents, may account for the sole use of TMC1 in the adult cochlear hair cells.
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Affiliation(s)
- Adam C Goldring
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Maryline Beurg
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Robert Fettiplace
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
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41
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Berekméri E, Fekete Á, Köles L, Zelles T. Postnatal Development of the Subcellular Structures and Purinergic Signaling of Deiters' Cells along the Tonotopic Axis of the Cochlea. Cells 2019; 8:cells8101266. [PMID: 31627326 PMCID: PMC6830339 DOI: 10.3390/cells8101266] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 10/03/2019] [Accepted: 10/15/2019] [Indexed: 01/04/2023] Open
Abstract
Exploring the development of the hearing organ helps in the understanding of hearing and hearing impairments and it promotes the development of the regenerative approaches-based therapeutic efforts. The role of supporting cells in the development of the organ of Corti is much less elucidated than that of the cochlear sensory receptor cells. The use of our recently published method of single-cell electroporation loading of a fluorescent Ca2+ probe in the mouse hemicochlea preparation provided an appropriate means to investigate the Deiters’ cells at the subcellular level in two different cochlear turns (apical, middle). Deiters’ cell’s soma and process elongated, and the process became slimmer by maturation without tonotopic preference. The tonotopically heterogeneous spontaneous Ca2+ activity less frequently occurred by maturation and implied subcellular difference. The exogenous ATP- and UTP-evoked Ca2+ responses were maturation-dependent and showed P2Y receptor dominance in the apical turn. By monitoring the basic structural dimensions of this supporting cell type as well as its spontaneous and evoked purinergic Ca2+ signaling in the hemicochlea preparation in different stages in the critical postnatal P5-25 developmental period for the first time, we showed that the soma and the phalangeal process of the Deiters’ cells go through age- and tonotopy-dependent changes in the morphometric parameters and purinergic signaling.
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Affiliation(s)
- Eszter Berekméri
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvárad tér 4., 1089 Budapest, Hungary.
- Department of Ecology, University of Veterinary Medicine, Rottenbiller u. 50., 1077 Budapest, Hungary.
| | - Ádám Fekete
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, 555 University Ave, Toronto, ON M5G 1X8, Canada.
| | - László Köles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvárad tér 4., 1089 Budapest, Hungary.
| | - Tibor Zelles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvárad tér 4., 1089 Budapest, Hungary.
- Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony u. 43., 1083 Budapest, Hungary.
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42
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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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43
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Cunningham CL, Müller U. Molecular Structure of the Hair Cell Mechanoelectrical Transduction Complex. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a033167. [PMID: 30082452 DOI: 10.1101/cshperspect.a033167] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cochlear hair cells employ mechanically gated ion channels located in stereocilia that open in response to sound wave-induced motion of the basilar membrane, converting mechanical stimulation to graded changes in hair cell membrane potential. Membrane potential changes in hair cells cause neurotransmitter release from hair cells that initiate electrical signals in the nerve terminals of afferent fibers from spiral ganglion neurons. These signals are then propagated within the central nervous system (CNS) to mediate the sensation of hearing. Recent studies show that the mechanoelectrical transduction (MET) machinery of hair cells is formed by an ensemble of proteins. Candidate components forming the MET channel have been identified, but none alone fulfills all criteria necessary to define them as pore-forming subunits of the MET channel. We will review here recent findings on the identification and function of proteins that are components of the MET machinery in hair cells and consider remaining open questions.
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Affiliation(s)
- Christopher L Cunningham
- The Solomon Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland 21205
| | - Ulrich Müller
- The Solomon Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland 21205
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44
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OHC-TRECK: A Novel System Using a Mouse Model for Investigation of the Molecular Mechanisms Associated with Outer Hair Cell Death in the Inner Ear. Sci Rep 2019; 9:5285. [PMID: 30918314 PMCID: PMC6437180 DOI: 10.1038/s41598-019-41711-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 03/15/2019] [Indexed: 12/20/2022] Open
Abstract
Outer hair cells (OHCs) are responsible for the amplification of sound, and the death of these cells leads to hearing loss. Although the mechanisms for sound amplification and OHC death have been well investigated, the effects on the cochlea after OHC death are poorly understood. To study the consequences of OHC death, we established an OHC knockout system using a novel mouse model, Prestin-hDTR, which uses the prestin promoter to express the human diphtheria toxin (DT) receptor gene (hDTR). Administration of DT to adult Prestin-hDTR mice results in the depletion of almost all OHCs without significant damage to other cochlear and vestibular cells, suggesting that this system is an effective tool for the analysis of how other cells in the cochlea and vestibula are affected after OHC death. To evaluate the changes in the cochlea after OHC death, we performed differential gene expression analysis between the untreated and DT-treated groups of wild-type and Prestin-hDTR mice. This analysis revealed that genes associated with inflammatory/immune responses were significantly upregulated. Moreover, we found that several genes linked to hearing loss were strongly downregulated by OHC death. Together, these results suggest that this OHC knockout system is a useful tool to identify biomarkers associated with OHC death.
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45
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Vélez-Ortega AC, Frolenkov GI. Building and repairing the stereocilia cytoskeleton in mammalian auditory hair cells. Hear Res 2019; 376:47-57. [PMID: 30638948 DOI: 10.1016/j.heares.2018.12.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/19/2018] [Accepted: 12/28/2018] [Indexed: 10/27/2022]
Abstract
Despite all recent achievements in identification of the molecules that are essential for the structure and mechanosensory function of stereocilia bundles in the auditory hair cells of mammalian species, we still have only a rudimentary understanding of the mechanisms of stereocilia formation, maintenance, and repair. Important molecular differences distinguishing mammalian auditory hair cells from hair cells of other types and species have been recently revealed. In addition, we are beginning to solve the puzzle of the apparent life-long stability of the stereocilia bundles in these cells. New data link the stability of the cytoskeleton in the mammalian auditory stereocilia with the normal activity of mechanotransduction channels. These data suggest new ideas on how a terminally-differentiated non-regenerating hair cell in the mammalian cochlea may repair and tune its stereocilia bundle throughout the life span of the organism.
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Affiliation(s)
- A Catalina Vélez-Ortega
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY, 40536-0298, USA.
| | - Gregory I Frolenkov
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY, 40536-0298, USA.
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46
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Berekméri E, Deák O, Téglás T, Sághy É, Horváth T, Aller M, Fekete Á, Köles L, Zelles T. Targeted single-cell electroporation loading of Ca 2+ indicators in the mature hemicochlea preparation. Hear Res 2018; 371:75-86. [PMID: 30504093 DOI: 10.1016/j.heares.2018.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 10/30/2018] [Accepted: 11/07/2018] [Indexed: 10/27/2022]
Abstract
Ca2+ is an important intracellular messenger and regulator in both physiological and pathophysiological mechanisms in the hearing organ. Investigation of cellular Ca2+ homeostasis in the mature cochlea is hampered by the special anatomy and high vulnerability of the organ. A quick, straightforward and reliable Ca2+ imaging method with high spatial and temporal resolution in the mature organ of Corti is missing. Cell cultures or isolated cells do not preserve the special microenvironment and intercellular communication, while cochlear explants are excised from only a restricted portion of the organ of Corti and usually from neonatal pre-hearing murines. The hemicochlea, prepared from hearing mice allows tonotopic experimental approach on the radial perspective in the basal, middle and apical turns of the organ. We used the preparation recently for functional imaging in supporting cells of the organ of Corti after bulk loading of the Ca2+ indicator. However, bulk loading takes long time, is variable and non-selective, and causes the accumulation of the indicator in the extracellular space. In this study we show the improved labeling of supporting cells of the organ of Corti by targeted single-cell electroporation in mature mouse hemicochlea. Single-cell electroporation proved to be a reliable way of reducing the duration and variability of loading and allowed subcellular Ca2+ imaging by increasing the signal-to-noise ratio, while cell viability was retained during the experiments. We demonstrated the applicability of the method by measuring the effect of purinergic, TRPA1, TRPV1 and ACh receptor stimulation on intracellular Ca2+ concentration at the cellular and subcellular level. In agreement with previous results, ATP evoked reversible and repeatable Ca2+ transients in Deiters', Hensen's and Claudius' cells. TRPA1 and TRPV1 stimulation by AITC and capsaicin, respectively, failed to induce any Ca2+ response in the supporting cells, except in a single Hensen's cell in which AITC evoked transients with smaller amplitude. AITC also caused the displacement of the tissue. Carbachol, agonist of ACh receptors induced Ca2+ transients in about a third of Deiters' and fifth of Hensen's cells. Here we have presented a fast and cell-specific indicator loading method allowing subcellular functional Ca2+ imaging in supporting cells of the organ of Corti in the mature hemicochlea preparation, thus providing a straightforward tool for deciphering the poorly understood regulation of Ca2+ homeostasis in these cells.
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Affiliation(s)
- Eszter Berekméri
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Orsolya Deák
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Tímea Téglás
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Éva Sághy
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Tamás Horváth
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Máté Aller
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Ádám Fekete
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, ON, Canada
| | - László Köles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
| | - Tibor Zelles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary.
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47
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Zhang LW, Cang XH, Chen Y, Guan MX. In vitro culture of mammalian inner ear hair cells. J Zhejiang Univ Sci B 2018; 20:170-179. [PMID: 30187712 DOI: 10.1631/jzus.b1700613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Auditory function in vertebrates depends on the transduction of sound vibrations into electrical signals by inner ear hair cells. In general, hearing loss resulting from hair cell damage is irreversible because the human ear has been considered to be incapable of regenerating or repairing these sensory elements following severe injury. Therefore, regeneration and protection of inner ear hair cells have become an exciting, rapidly evolving field of research during the last decade. However, mammalian auditory hair cells are few in number, experimentally inaccessible, and barely proliferate postnatally in vitro. Various in vitro primary culture systems of inner ear hair cells have been established by different groups, although many challenges remain unresolved. Here, we briefly explain the structure of the inner ear, summarize the published methods of in vitro hair cell cultures, and propose a feasible protocol for culturing these cells, which gave satisfactory results in our study. A better understanding of in vitro hair cell cultures will substantially facilitate research involving auditory functions, drug development, and the isolation of critical molecules involved in hair cell biology.
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Affiliation(s)
- Lu-Wen Zhang
- Division of Medical Genetics and Genomics, the Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China.,Institute of Genetics, Zhejiang University and Department of Genetics, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Xiao-Hui Cang
- Division of Medical Genetics and Genomics, the Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China.,Institute of Genetics, Zhejiang University and Department of Genetics, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Ye Chen
- Division of Medical Genetics and Genomics, the Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China.,Institute of Genetics, Zhejiang University and Department of Genetics, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Min-Xin Guan
- Division of Medical Genetics and Genomics, the Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China.,Institute of Genetics, Zhejiang University and Department of Genetics, Zhejiang University School of Medicine, Hangzhou 310058, China
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48
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Men Y, Li X, Tu H, Zhang A, Fu X, Wang Z, Jin Y, Hou C, Zhang T, Zhang S, Zhou Y, Li B, Li J, Sun X, Wang H, Gao J. Tprn is essential for the integrity of stereociliary rootlet in cochlear hair cells in mice. Front Med 2018; 13:690-704. [PMID: 30159668 DOI: 10.1007/s11684-018-0638-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Accepted: 01/27/2018] [Indexed: 11/24/2022]
Abstract
Tprn encodes the taperin protein, which is concentrated in the tapered region of hair cell stereocilia in the inner ear. In humans, TPRN mutations cause autosomal recessive nonsyndromic deafness (DFNB79) by an unknown mechanism. To determine the role of Tprn in hearing, we generated Tprn-null mice by clustered regularly interspaced short palindromic repeat/Cas9 genome-editing technology from a CBA/CaJ background. We observed significant hearing loss and progressive degeneration of stereocilia in the outer hair cells of Tprn-null mice starting from postnatal day 30. Transmission electron microscopy images of stereociliary bundles in the mutant mice showed some stereociliary rootlets with curved shafts. The central cores of the stereociliary rootlets possessed hollow structures with surrounding loose peripheral dense rings. Radixin, a protein expressed at stereocilia tapering, was abnormally dispersed along the stereocilia shafts in Tprn-null mice. The expression levels of radixin and β-actin significantly decreased.We propose that Tprn is critical to the retention of the integrity of the stereociliary rootlet. Loss of Tprn in Tprn-null mice caused the disruption of the stereociliary rootlet, which resulted in damage to stereociliary bundles and hearing impairments. The generated Tprn-null mice are ideal models of human hereditary deafness DFNB79.
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Affiliation(s)
- Yuqin Men
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Xiujuan Li
- Rizhao Polytechnic, Rizhao, 276826, China
| | - Hailong Tu
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Aizhen Zhang
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Xiaolong Fu
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Zhishuo Wang
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Yecheng Jin
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Congzhe Hou
- The Second Hospital of Shandong University, Jinan, 250033, China
| | - Tingting Zhang
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Sen Zhang
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Yichen Zhou
- School of Life Science, Shandong University, Jinan, 250100, China
| | - Boqin Li
- Electron Microscopy Laboratory, Shandong Institute of Otolaryngology, Jinan, 250022, China.,Laboratory of Electron Microscopy, Jinan WEI-YA Biotech Company, Jinan, 250100, China
| | - Jianfeng Li
- Department of Otolaryngology-Head and Neck Surgery, Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China
| | - Xiaoyang Sun
- School of Life Science, Shandong University, Jinan, 250100, China.
| | - Haibo Wang
- Department of Otolaryngology-Head and Neck Surgery, Provincial Hospital Affiliated to Shandong University, Jinan, 250021, China.
| | - Jiangang Gao
- School of Life Science, Shandong University, Jinan, 250100, China.
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49
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Avenarius MR, Jung JY, Askew C, Jones SM, Hunker KL, Azaiez H, Rehman AU, Schraders M, Najmabadi H, Kremer H, Smith RJH, Géléoc GSG, Dolan DF, Raphael Y, Kohrman DC. Grxcr2 is required for stereocilia morphogenesis in the cochlea. PLoS One 2018; 13:e0201713. [PMID: 30157177 PMCID: PMC6114524 DOI: 10.1371/journal.pone.0201713] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 07/22/2018] [Indexed: 11/18/2022] Open
Abstract
Hearing and balance depend upon the precise morphogenesis and mechanosensory function of stereocilia, the specialized structures on the apical surface of sensory hair cells in the inner ear. Previous studies of Grxcr1 mutant mice indicated a critical role for this gene in control of stereocilia dimensions during development. In this study, we analyzed expression of the paralog Grxcr2 in the mouse and evaluated auditory and vestibular function of strains carrying targeted mutations of the gene. Peak expression of Grxcr2 occurs during early postnatal development of the inner ear and GRXCR2 is localized to stereocilia in both the cochlea and in vestibular organs. Homozygous Grxcr2 deletion mutants exhibit significant hearing loss by 3 weeks of age that is associated with developmental defects in stereocilia bundle orientation and organization. Despite these bundle defects, the mechanotransduction apparatus assembles in relatively normal fashion as determined by whole cell electrophysiological evaluation and FM1-43 uptake. Although Grxcr2 mutants do not exhibit overt vestibular dysfunction, evaluation of vestibular evoked potentials revealed subtle defects of the mutants in response to linear accelerations. In addition, reduced Grxcr2 expression in a hypomorphic mutant strain is associated with progressive hearing loss and bundle defects. The stereocilia localization of GRXCR2, together with the bundle pathologies observed in the mutants, indicate that GRXCR2 plays an intrinsic role in bundle orientation, organization, and sensory function in the inner ear during development and at maturity.
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Affiliation(s)
- Matthew R. Avenarius
- Department of Otolaryngology/Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Jae-Yun Jung
- Department of Otolaryngology/Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Charles Askew
- Neuroscience Graduate Program, University of Virginia, Charlottesville, Virginia, United States of America
- Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Sherri M. Jones
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, North Carolina, United States of America
| | - Kristina L. Hunker
- Department of Otolaryngology/Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Hela Azaiez
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Atteeq U. Rehman
- Section on Human Genetics, Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, Maryland, United States of America
| | - Margit Schraders
- Hearing & Genes Division, Department of Otorhinolaryngology, Radboud University Medical Center, Nijmegen, The Netherlands
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Hossein Najmabadi
- Genetics Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Hannie Kremer
- Hearing & Genes Division, Department of Otorhinolaryngology, Radboud University Medical Center, Nijmegen, The Netherlands
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Richard J. H. Smith
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Gwenaëlle S. G. Géléoc
- Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - David F. Dolan
- Department of Otolaryngology/Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Yehoash Raphael
- Department of Otolaryngology/Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - David C. Kohrman
- Department of Otolaryngology/Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
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50
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Sun S, Babola T, Pregernig G, So KS, Nguyen M, Su SSM, Palermo AT, Bergles DE, Burns JC, Müller U. Hair Cell Mechanotransduction Regulates Spontaneous Activity and Spiral Ganglion Subtype Specification in the Auditory System. Cell 2018; 174:1247-1263.e15. [PMID: 30078710 PMCID: PMC6429032 DOI: 10.1016/j.cell.2018.07.008] [Citation(s) in RCA: 190] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 04/23/2018] [Accepted: 07/02/2018] [Indexed: 01/06/2023]
Abstract
Type I spiral ganglion neurons (SGNs) transmit sound information from cochlear hair cells to the CNS. Using transcriptome analysis of thousands of single neurons, we demonstrate that murine type I SGNs consist of subclasses that are defined by the expression of subsets of transcription factors, cell adhesion molecules, ion channels, and neurotransmitter receptors. Subtype specification is initiated prior to the onset of hearing during the time period when auditory circuits mature. Gene mutations linked to deafness that disrupt hair cell mechanotransduction or glutamatergic signaling perturb the firing behavior of SGNs prior to hearing onset and disrupt SGN subtype specification. We thus conclude that an intact hair cell mechanotransduction machinery is critical during the pre-hearing period to regulate the firing behavior of SGNs and their segregation into subtypes. Because deafness is frequently caused by defects in hair cells, our findings have significant ramifications for the etiology of hearing loss and its treatment.
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Affiliation(s)
- Shuohao Sun
- The Solomon Snyder Department of Neuroscience and Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
| | - Travis Babola
- The Solomon Snyder Department of Neuroscience and Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
| | - Gabriela Pregernig
- Decibel Therapeutics, 1325 Boylston Street, Suite 500, Boston, MA 02215, USA
| | - Kathy S So
- Decibel Therapeutics, 1325 Boylston Street, Suite 500, Boston, MA 02215, USA
| | - Matthew Nguyen
- Decibel Therapeutics, 1325 Boylston Street, Suite 500, Boston, MA 02215, USA
| | - Shin-San M Su
- Decibel Therapeutics, 1325 Boylston Street, Suite 500, Boston, MA 02215, USA
| | - Adam T Palermo
- Decibel Therapeutics, 1325 Boylston Street, Suite 500, Boston, MA 02215, USA
| | - Dwight E Bergles
- The Solomon Snyder Department of Neuroscience and Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
| | - Joseph C Burns
- Decibel Therapeutics, 1325 Boylston Street, Suite 500, Boston, MA 02215, USA.
| | - Ulrich Müller
- The Solomon Snyder Department of Neuroscience and Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA.
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