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Karagulyan N, Moser T. Synaptic activity is not required for establishing heterogeneity of inner hair cell ribbon synapses. Front Mol Neurosci 2023; 16:1248941. [PMID: 37745283 PMCID: PMC10512025 DOI: 10.3389/fnmol.2023.1248941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 08/17/2023] [Indexed: 09/26/2023] Open
Abstract
Neural sound encoding in the mammalian cochlea faces the challenge of representing audible sound pressures that vary over six orders of magnitude. The cochlea meets this demand through the use of active micromechanics as well as the diversity and adaptation of afferent neurons and their synapses. Mechanisms underlying neural diversity likely include heterogeneous presynaptic input from inner hair cells (IHCs) to spiral ganglion neurons (SGNs) as well as differences in the molecular profile of SGNs and in their efferent control. Here, we tested whether glutamate release from IHCs, previously found to be critical for maintaining different molecular SGN profiles, is required for establishing heterogeneity of active zones (AZs) in IHCs. We analyzed structural and functional heterogeneity of IHC AZs in mouse mutants with disrupted glutamate release from IHCs due to lack of a vesicular glutamate transporter (Vglut3) or impaired exocytosis due to defective otoferlin. We found the variance of the voltage-dependence of presynaptic Ca2+ influx to be reduced in exocytosis-deficient IHCs of otoferlin mutants. Yet, the spatial gradients of maximal amplitude and voltage-dependence of Ca2+ influx along the pillar-modiolar IHC axis were maintained in both mutants. Further immunohistochemical analysis showed an intact spatial gradient of ribbon size in Vglut3-/- mice. These results indicate that IHC exocytosis and glutamate release are not strictly required for establishing the heterogeneity of IHC AZs.
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Affiliation(s)
- Nare Karagulyan
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience and Nanophysiology Group, Max Planck Institute of Multidisciplinary Sciences, Göttingen, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany
- Hertha Sponer College, Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience and Nanophysiology Group, Max Planck Institute of Multidisciplinary Sciences, Göttingen, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany
- Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
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2
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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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3
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Sharma K, Kang KW, Seo YW, Glowatzki E, Yi E. Low-voltage Activating K + Channels in Cochlear Afferent Nerve Fiber Dendrites. Exp Neurobiol 2022; 31:243-259. [PMID: 36050224 PMCID: PMC9471414 DOI: 10.5607/en22013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/18/2022] [Accepted: 07/29/2022] [Indexed: 11/19/2022] Open
Abstract
Cochlear afferent nerve fibers (ANF) are the first neurons in the ascending auditory pathway. We investigated the low-voltage activating K+ channels expressed in ANF dendrites using isolated rat cochlear segments. Whole cell patch clamp recordings were made from the dendritic terminals of ANFs. Outward currents activating at membrane potentials as low as -64 mV were observed in all dendrites studied. These currents were inhibited by 4-aminopyridine (4-AP), a blocker known to preferentially inhibit low-voltage activating K+ currents (IKL) in CNS auditory neurons and spiral ganglion neurons. When the dendritic IKL was blocked by 4-AP, the EPSP decay time was significantly prolonged, suggesting that dendritic IKL speeds up the decay of EPSPs and likely modulates action potentials of ANFs. To reveal molecular subtype of dendritic IKL, α-dendrotoxin (α-DTX), a selective inhibitor for Kv1.1, Kv1.2, and Kv1.6 containing channels, was tested. α-DTX inhibited 23±9% of dendritic IKL. To identify the α-DTXsensitive and α-DTX-insensitive components of IKL, immunofluorescence labeling was performed. Strong Kv1.1- and Kv1.2-immunoreactivity was found at unmyelinated dendritic segments, nodes of Ranvier, and cell bodies of most ANFs. A small fraction of ANF dendrites showed Kv7.2- immunoreactivity. These data suggest that dendritic IKL is conducted through Kv1.1and Kv1.2 channels, with a minor contribution from Kv7.2 and other as yet unidentified channels.
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Affiliation(s)
- Kushal Sharma
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kwon Woo Kang
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Young-Woo Seo
- KBSI Gwangju Center, Korea Basic Science Institute, Gwangju 61186, Korea
| | - Elisabeth Glowatzki
- Department of Otolaryngology-Head and Neck Surgery and Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
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4
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Altered neural networks and cognition in a hereditary colon cancer. IBRO Neurosci Rep 2021; 11:137-143. [PMID: 34693396 PMCID: PMC8517154 DOI: 10.1016/j.ibneur.2021.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/25/2021] [Accepted: 09/27/2021] [Indexed: 11/21/2022] Open
Abstract
Familial Adenomatous Polyposis (FAP) is an autosomal dominant disorder caused by mutation of the APC gene presenting with numerous colorectal adenomatous polyps and a near 100% risk of colon cancer. Preliminary research findings from our group indicate that FAP patients experience significant deficits across many cognitive domains. In the current study, fMRI brain metrics in a FAP population and matched controls were used to further the mechanistic understanding of reported cognitive deficits. This research identified and characterized any possible differences in resting brain networks and associations between neural network changes and cognition from 34 participants (18 FAP patients, 16 healthy controls). Functional connectivity analysis was performed using FSL with independent component analysis (ICA) to identify functional networks. Significant differences between cases and controls were observed in 8 well-established resting state networks. With the addition of an aggregate cognitive measure as a covariate, these differences were virtually non-existent, indicating a strong correlation between cognition and brain activity at the network level. The data indicate robust and pervasive effects on functional neural network activity among FAP patients and these effects are likely involved in cognitive deficits associated with this disease.
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5
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Chen X, Abad C, Chen ZY, Young JI, Gurumurthy CB, Walz K, Liu XZ. Generation and characterization of a P2rx2 V60L mouse model for DFNA41. Hum Mol Genet 2021; 30:985-995. [PMID: 33791800 DOI: 10.1093/hmg/ddab077] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 03/06/2021] [Accepted: 03/12/2021] [Indexed: 11/13/2022] Open
Abstract
P2RX2 encodes the P2X2 receptor, which is an adenosine triphosphate (ATP) gated (purinoreceptor) ion channel. P2RX2 c. 178G > T (p.V60L) mutation was previously identified in two unrelated Chinese families, as the cause of human DFNA41, a form of dominant, early-onset and progressive sensorineural hearing loss. We generated and characterized a knock-in mouse model based on human p.V60L mutation that recapitulates the human phenotype. Heterozygous KI mice started to exhibit hearing loss at 21-day-old and progressed to deafness by 6-month-old. Vestibular dysfunction was also observed in mutant mice. Abnormal morphology of the inner hair cells and ribbon synapses was progressively observed in KI animals suggesting that P2rx2 plays a role in the membrane spatial location of the ribbon synapses. These results suggest that P2rx2 is essential for acoustic information transfer, which can be the molecular mechanism related to hearing loss.
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Affiliation(s)
- Xiaoya Chen
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.,Department of Otolaryngology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Clemer Abad
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Zheng-Yi Chen
- Department of Otolaryngology and Program in Neuroscience, Harvard Medical School and Eaton Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, USA
| | - Juan I Young
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL 33136, USA.,Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Channabasavaiah B Gurumurthy
- Mouse Genome Engineering Core Facility, Vice Chancellor for Research Office, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Katherina Walz
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL 33136, USA.,Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Xue Zhong Liu
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.,Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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6
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Eckert P, Marchetta P, Manthey MK, Walter MH, Jovanovic S, Savitska D, Singer W, Jacob MH, Rüttiger L, Schimmang T, Milenkovic I, Pilz PKD, Knipper M. Deletion of BDNF in Pax2 Lineage-Derived Interneuron Precursors in the Hindbrain Hampers the Proportion of Excitation/Inhibition, Learning, and Behavior. Front Mol Neurosci 2021; 14:642679. [PMID: 33841098 PMCID: PMC8033028 DOI: 10.3389/fnmol.2021.642679] [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: 12/16/2020] [Accepted: 02/26/2021] [Indexed: 12/16/2022] Open
Abstract
Numerous studies indicate that deficits in the proper integration or migration of specific GABAergic precursor cells from the subpallium to the cortex can lead to severe cognitive dysfunctions and neurodevelopmental pathogenesis linked to intellectual disabilities. A different set of GABAergic precursors cells that express Pax2 migrate to hindbrain regions, targeting, for example auditory or somatosensory brainstem regions. We demonstrate that the absence of BDNF in Pax2-lineage descendants of BdnfPax2KOs causes severe cognitive disabilities. In BdnfPax2KOs, a normal number of parvalbumin-positive interneurons (PV-INs) was found in the auditory cortex (AC) and hippocampal regions, which went hand in hand with reduced PV-labeling in neuropil domains and elevated activity-regulated cytoskeleton-associated protein (Arc/Arg3.1; here: Arc) levels in pyramidal neurons in these same regions. This immaturity in the inhibitory/excitatory balance of the AC and hippocampus was accompanied by elevated LTP, reduced (sound-induced) LTP/LTD adjustment, impaired learning, elevated anxiety, and deficits in social behavior, overall representing an autistic-like phenotype. Reduced tonic inhibitory strength and elevated spontaneous firing rates in dorsal cochlear nucleus (DCN) brainstem neurons in otherwise nearly normal hearing BdnfPax2KOs suggests that diminished fine-grained auditory-specific brainstem activity has hampered activity-driven integration of inhibitory networks of the AC in functional (hippocampal) circuits. This leads to an inability to scale hippocampal post-synapses during LTP/LTD plasticity. BDNF in Pax2-lineage descendants in lower brain regions should thus be considered as a novel candidate for contributing to the development of brain disorders, including autism.
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Affiliation(s)
- Philipp Eckert
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Philine Marchetta
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Marie K Manthey
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany.,Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, United States
| | - Michael H Walter
- Department for Animal Physiology, Institute of Neurobiology, University of Tübingen, Tübingen, Germany
| | - Sasa Jovanovic
- School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Daria Savitska
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Wibke Singer
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Michele H Jacob
- Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA, United States
| | - Lukas Rüttiger
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Thomas Schimmang
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, Valladolid, Spain
| | - Ivan Milenkovic
- School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Peter K D Pilz
- Department for Animal Physiology, Institute of Neurobiology, University of Tübingen, Tübingen, Germany
| | - Marlies Knipper
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
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7
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Cali RJ, Nephew BC, Moore CM, Chumachenko S, Sala AC, Cintron B, Luciano C, King JA, Hooper SR, Giardiello FM, Cruz-Correa M. Altered Resting State Brain Networks and Cognition in Familial Adenomatous Polyposis. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2020. [PMID: 33173924 DOI: 10.1101/2020.11.02.20224477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Familial Adenomatous Polyposis (FAP) is an autosomal dominant disorder caused by mutation of the APC gene presenting with numerous colorectal adenomatous polyps and a near 100% risk of colon cancer. Preliminary research findings from our group indicate that FAP patients experience significant deficits across many cognitive domains. In the current study, fMRI brain metrics in a FAP population and matched controls were used to further the mechanistic understanding of reported cognitive deficits. This research identified and characterized any possible differences in resting brain networks and associations between neural network changes and cognition from 34 participants (18 FAP patients, 16 healthy controls). Functional connectivity analysis was performed using FSL with independent component analysis (ICA) to identify functional networks. Significant differences between cases and controls were observed in 8 well-established resting state networks. With the addition of an aggregate cognitive measure as a covariate, these differences were virtually non-existent, indicating a strong correlation between cognition and brain activity at the network level. The data indicate robust and pervasive effects on functional neural network activity among FAP patients and these effects are likely involved in cognitive deficits associated with this disease.
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8
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Nadar-Ponniah PT, Taiber S, Caspi M, Koffler-Brill T, Dror AA, Siman-Tov R, Rubinstein M, Padmanabhan K, Luxenburg C, Lang RA, Avraham KB, Rosin-Arbesfeld R. Striatin Is Required for Hearing and Affects Inner Hair Cells and Ribbon Synapses. Front Cell Dev Biol 2020; 8:615. [PMID: 32766247 PMCID: PMC7381154 DOI: 10.3389/fcell.2020.00615] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 06/22/2020] [Indexed: 12/22/2022] Open
Abstract
Striatin, a subunit of the serine/threonine phosphatase PP2A, is a core member of the conserved striatin-interacting phosphatase and kinase (STRIPAK) complexes. The protein is expressed in the cell junctions between epithelial cells, which play a role in maintaining cell-cell adhesion. Since the cell junctions are crucial for the function of the mammalian inner ear, we examined the localization and function of striatin in the mouse cochlea. Our results show that in neonatal mice, striatin is specifically expressed in the cell-cell junctions of the inner hair cells, the receptor cells in the mammalian cochlea. Auditory brainstem response measurements of striatin-deficient mice indicated a progressive, high-frequency hearing loss, suggesting that striatin is essential for normal hearing. Moreover, scanning electron micrographs of the organ of Corti revealed a moderate degeneration of the outer hair cells in the middle and basal regions, concordant with the high-frequency hearing loss. Additionally, striatin-deficient mice show aberrant ribbon synapse maturation. Loss of the outer hair cells, combined with the aberrant ribbon synapse distribution, may lead to the observed auditory impairment. Together, these results suggest a novel function for striatin in the mammalian auditory system.
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Affiliation(s)
- Prathamesh T. Nadar-Ponniah
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Shahar Taiber
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Michal Caspi
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Tal Koffler-Brill
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Amiel A. Dror
- Department of Otolaryngology, Head and Neck Surgery, Galilee Medical Center, Nahariya, Israel
- Azrieli Faculty of Medicine, Bar-Ilan University, Safed, Israel
| | - Ronen Siman-Tov
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Moran Rubinstein
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
- Goldschleger Eye Research Institute, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Krishnanand Padmanabhan
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Chen Luxenburg
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Richard A. Lang
- Visual Systems Group, Abrahamson Pediatric Eye Institute, Division of Pediatric Ophthalmology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
| | - Karen B. Avraham
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Rina Rosin-Arbesfeld
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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9
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Hashimoto K, Hickman TT, Suzuki J, Ji L, Kohrman DC, Corfas G, Liberman MC. Protection from noise-induced cochlear synaptopathy by virally mediated overexpression of NT3. Sci Rep 2019; 9:15362. [PMID: 31653916 PMCID: PMC6814859 DOI: 10.1038/s41598-019-51724-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 09/26/2019] [Indexed: 12/23/2022] Open
Abstract
Noise exposures causing only transient threshold shifts can destroy auditory-nerve synapses without damaging hair cells. Here, we asked whether virally mediated neurotrophin3 (NT3) overexpression can repair this damage. CBA/CaJ mice at 6 wks were injected unilaterally with adeno-associated virus (AAV) containing either NT3 or GFP genes, via the posterior semicircular canal, 3 wks prior to, or 5 hrs after, noise exposure. Controls included exposed animals receiving vehicle only, and unexposed animals receiving virus. Thresholds were measured 2 wks post-exposure, just before cochleas were harvested for histological analysis. In separate virus-injected animals, unexposed cochleas were extracted for qRT-PCR. The GFP reporter showed that inner hair cells (IHCs) were transfected throughout the cochlea, and outer hair cells mainly in the apex. qRT-PCR showed 4- to 10-fold overexpression of NT3 from 1–21 days post-injection, and 1.7-fold overexpression at 40 days. AAV-NT3 delivered prior to noise exposure produced a dose-dependent reduction of synaptopathy, with nearly complete rescue at some cochlear locations. In unexposed ears, NT3 overexpression did not affect thresholds, however GFP overexpression caused IHC loss. In exposed ears, NT3 overexpression increased permanent threshold shifts. Thus, although NT3 overexpression can minimize noise-induced synaptic damage, the forced overexpression may be harmful to hair cells themselves during cochlear overstimulation.
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Affiliation(s)
- Ken Hashimoto
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, USA.,Eaton-Peabody Laboratories, Massachusetts Eye & Ear, Boston, MA, USA.,Department of Otorhinolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Tyler T Hickman
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, USA. .,Eaton-Peabody Laboratories, Massachusetts Eye & Ear, Boston, MA, USA.
| | - Jun Suzuki
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, USA.,Eaton-Peabody Laboratories, Massachusetts Eye & Ear, Boston, MA, USA.,Department of Otorhinolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Lingchao Ji
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA.,Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - David C Kohrman
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA.,Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Gabriel Corfas
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, USA.,Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - M Charles Liberman
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, USA.,Eaton-Peabody Laboratories, Massachusetts Eye & Ear, Boston, MA, USA
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10
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Frank MM, Goodrich LV. Talking back: Development of the olivocochlear efferent system. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2018; 7:e324. [PMID: 29944783 PMCID: PMC6185769 DOI: 10.1002/wdev.324] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/27/2018] [Accepted: 05/17/2018] [Indexed: 02/02/2023]
Abstract
Developing sensory systems must coordinate the growth of neural circuitry spanning from receptors in the peripheral nervous system (PNS) to multilayered networks within the central nervous system (CNS). This breadth presents particular challenges, as nascent processes must navigate across the CNS-PNS boundary and coalesce into a tightly intermingled wiring pattern, thereby enabling reliable integration from the PNS to the CNS and back. In the auditory system, feedforward spiral ganglion neurons (SGNs) from the periphery collect sound information via tonotopically organized connections in the cochlea and transmit this information to the brainstem for processing via the VIII cranial nerve. In turn, feedback olivocochlear neurons (OCNs) housed in the auditory brainstem send projections into the periphery, also through the VIII nerve. OCNs are motor neuron-like efferent cells that influence auditory processing within the cochlea and protect against noise damage in adult animals. These aligned feedforward and feedback systems develop in parallel, with SGN central axons reaching the developing auditory brainstem around the same time that the OCN axons extend out toward the developing inner ear. Recent findings have begun to unravel the genetic and molecular mechanisms that guide OCN development, from their origins in a generic pool of motor neuron precursors to their specialized roles as modulators of cochlear activity. One recurrent theme is the importance of efferent-afferent interactions, as afferent SGNs guide OCNs to their final locations within the sensory epithelium, and efferent OCNs shape the activity of the developing auditory system. This article is categorized under: Nervous System Development > Vertebrates: Regional Development.
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11
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Meese S, Cepeda AP, Gahlen F, Adams CM, Ficner R, Ricci AJ, Heller S, Reisinger E, Herget M. Activity-Dependent Phosphorylation by CaMKIIδ Alters the Ca 2+ Affinity of the Multi-C 2-Domain Protein Otoferlin. Front Synaptic Neurosci 2017; 9:13. [PMID: 29046633 PMCID: PMC5632675 DOI: 10.3389/fnsyn.2017.00013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 09/11/2017] [Indexed: 01/20/2023] Open
Abstract
Otoferlin is essential for fast Ca2+-triggered transmitter release from auditory inner hair cells (IHCs), playing key roles in synaptic vesicle release, replenishment and retrieval. Dysfunction of otoferlin results in profound prelingual deafness. Despite its crucial role in cochlear synaptic processes, mechanisms regulating otoferlin activity have not been studied to date. Here, we identified Ca2+/calmodulin-dependent serine/threonine kinase II delta (CaMKIIδ) as an otoferlin binding partner by pull-downs from chicken utricles and reassured interaction by a co-immunoprecipitation with heterologously expressed proteins in HEK cells. We confirmed the expression of CaMKIIδ in rodent IHCs by immunohistochemistry and real-time PCR. A proximity ligation assay indicates close proximity of the two proteins in rat IHCs, suggesting that otoferlin and CaMKIIδ also interact in mammalian IHCs. In vitro phosphorylation of otoferlin by CaMKIIδ revealed ten phosphorylation sites, five of which are located within C2-domains. Exchange of serines/threonines at phosphorylated sites into phosphomimetic aspartates reduces the Ca2+ affinity of the recombinant C2F domain 10-fold, and increases the Ca2+ affinity of the C2C domain. Concordantly, we show that phosphorylation of otoferlin and/or its interaction partners are enhanced upon hair cell depolarization and blocked by pharmacological CaMKII inhibition. We therefore propose that otoferlin activity is regulated by CaMKIIδ in IHCs.
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Affiliation(s)
- Sandra Meese
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, and Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences, Göttingen, Germany
| | - Andreia P Cepeda
- Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences, Göttingen, Germany.,Molecular Biology of Cochlear Neurotransmission Group, Department of Otorhinolaryngology, University Medical Center Göttingen, and Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
| | - Felix Gahlen
- Department of Otorhinolaryngology, Head and Neck Surgery, Ruhr-University Bochum, Bochum, Germany
| | - Christopher M Adams
- Stanford University Mass Spectrometry, Stanford University, Stanford, CA, United States
| | - Ralf Ficner
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, and Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
| | - Anthony J Ricci
- Department of Otolaryngology, Head and Neck Surgery, Stanford School of Medicine, Stanford, CA, United States
| | - Stefan Heller
- Department of Otolaryngology, Head and Neck Surgery, Stanford School of Medicine, Stanford, CA, United States
| | - Ellen Reisinger
- Molecular Biology of Cochlear Neurotransmission Group, Department of Otorhinolaryngology, University Medical Center Göttingen, and Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
| | - Meike Herget
- Department of Otolaryngology, Head and Neck Surgery, Stanford School of Medicine, Stanford, CA, United States
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12
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Shetty GA, Hattiangady B, Upadhya D, Bates A, Attaluri S, Shuai B, Kodali M, Shetty AK. Chronic Oxidative Stress, Mitochondrial Dysfunction, Nrf2 Activation and Inflammation in the Hippocampus Accompany Heightened Systemic Inflammation and Oxidative Stress in an Animal Model of Gulf War Illness. Front Mol Neurosci 2017; 10:182. [PMID: 28659758 PMCID: PMC5469946 DOI: 10.3389/fnmol.2017.00182] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 05/26/2017] [Indexed: 01/21/2023] Open
Abstract
Memory and mood dysfunction are the key symptoms of Gulf war illness (GWI), a lingering multi-symptom ailment afflicting >200,000 veterans who served in the Persian Gulf War-1. Research probing the source of the disease has demonstrated that concomitant exposures to anti-nerve gas agent pyridostigmine bromide (PB), pesticides, and war-related stress are among the chief causes of GWI. Indeed, exposures to GWI-related chemicals (GWIR-Cs) and mild stress in animal models cause memory and mood impairments alongside reduced neurogenesis and chronic low-level inflammation in the hippocampus. In the current study, we examined whether exposure to GWIR-Cs and stress causes chronic changes in the expression of genes related to increased oxidative stress, mitochondrial dysfunction, and inflammation in the hippocampus. We also investigated whether GWI is linked with chronically increased activation of Nrf2 (a master regulator of antioxidant response) in the hippocampus, and inflammation and enhanced oxidative stress at the systemic level. Adult male rats were exposed daily to low-doses of PB and pesticides (DEET and permethrin), in combination with 5 min of restraint stress for 4 weeks. Analysis of the hippocampus performed 6 months after the exposure revealed increased expression of many genes related to oxidative stress response and/or antioxidant activity (Hmox1, Sepp1, and Srxn1), reactive oxygen species metabolism (Fmo2, Sod2, and Ucp2) and oxygen transport (Ift172 and Slc38a1). Furthermore, multiple genes relevant to mitochondrial respiration (Atp6a1, Cox6a1, Cox7a2L, Ndufs7, Ndufv1, Lhpp, Slc25a10, and Ucp1) and neuroinflammation (Nfkb1, Bcl6, Csf2, IL6, Mapk1, Mapk3, Ngf, N-pac, and Prkaca) were up-regulated, alongside 73–88% reduction in the expression of anti-inflammatory genes IL4 and IL10, and nuclear translocation and increased expression of Nrf2 protein. These hippocampal changes were associated with elevated levels of pro-inflammatory cytokines and chemokines (Tnfa, IL1b, IL1a, Tgfb, and Fgf2) and lipid peroxidation byproduct malondialdehyde in the serum, suggesting the presence of an incessant systemic inflammation and elevated oxidative stress. These results imply that chronic oxidative stress, inflammation, and mitochondrial dysfunction in the hippocampus, and heightened systemic inflammation and oxidative stress likely underlie the persistent memory and mood dysfunction observed in GWI.
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Affiliation(s)
- Geetha A Shetty
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, TempleTX, United States.,Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine, Temple and College StationTX, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College StationTX, United States
| | - Bharathi Hattiangady
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, TempleTX, United States.,Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine, Temple and College StationTX, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College StationTX, United States
| | - Dinesh Upadhya
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, TempleTX, United States.,Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine, Temple and College StationTX, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College StationTX, United States
| | - Adrian Bates
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, TempleTX, United States.,Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine, Temple and College StationTX, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College StationTX, United States
| | - Sahithi Attaluri
- Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine, Temple and College StationTX, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College StationTX, United States
| | - Bing Shuai
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, TempleTX, United States.,Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine, Temple and College StationTX, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College StationTX, United States
| | - Maheedhar Kodali
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, TempleTX, United States.,Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine, Temple and College StationTX, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College StationTX, United States
| | - Ashok K Shetty
- Research Service, Olin E. Teague Veterans' Medical Center, Central Texas Veterans Health Care System, TempleTX, United States.,Institute for Regenerative Medicine, Texas A&M Health Science Center College of Medicine, Temple and College StationTX, United States.,Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College StationTX, United States
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13
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Lauer AM. Minimal Effects of Age and Exposure to a Noisy Environment on Hearing in Alpha9 Nicotinic Receptor Knockout Mice. Front Neurosci 2017. [PMID: 28626386 PMCID: PMC5454393 DOI: 10.3389/fnins.2017.00304] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Studies have suggested a role of weakened medial olivocochlear (OC) efferent feedback in accelerated hearing loss and increased susceptibility to noise. The present study investigated the progression of hearing loss with age and exposure to a noisy environment in medial OC-deficient mice. Alpha9 nicotinic acetylcholine receptor knockout (α9KO) and wild types were screened for hearing loss using auditory brainstem responses. α9KO mice housed in a quiet environment did not show increased hearing loss compared to wild types in young adulthood and middle age. Challenging the medial OC system by housing in a noisy environment did not increase hearing loss in α9KO mice compared to wild types. ABR wave 1 amplitudes also did not show differences between α9KO mice and wild types. These data suggest that deficient medial OC feedback does not result in early onset of hearing loss.
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Affiliation(s)
- Amanda M Lauer
- Department of Otolaryngology-HNS, Center for Hearing and Balance, Johns Hopkins University School of MedicineBaltimore, MD, United States
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14
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Spatial Gradients in the Size of Inner Hair Cell Ribbons Emerge Before the Onset of Hearing in Rats. J Assoc Res Otolaryngol 2017; 18:399-413. [PMID: 28361374 DOI: 10.1007/s10162-017-0620-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 03/02/2017] [Indexed: 01/02/2023] Open
Abstract
The size and locations of pre-synaptic ribbons and glutamate receptors within and around inner hair cells are correlated with auditory afferent response features such as the spontaneous discharge rate (SR), threshold, and dynamic range of sound intensity representation (the so-called SR-groups). To test if the development of these spatial gradients requires experience with sound intensity, we quantified the size and spatial distribution of synaptic ribbons from the inner hair cells of neonatal rats before and after the onset of hearing (from post-natal day (P) 3 to P33). To quantify ribbon size, we used high resolution fluorescence confocal microscopy and 3-D reconstructions of immunolabeled ribbons. The size, density, and spatial distribution of ribbons changed during development. At P3, ribbons were densely clustered near the basal/modiolar face of the hair cell where low SR-groups preferentially contact adult hair cells. By P12, the disparity in ribbon count was less striking and ribbons were equally likely to occupy both faces. At all ages before P12, ribbons were larger on the modiolar face than on the pillar face. These differences initially grew larger with age but collapsed around the onset of hearing. Between P12 and P33, the spatial gradients remained small and began to re-emerge around P33. Even by P12, we did not find spatial gradients in the size of the post-synaptic glutamate receptors as is found on afferent terminals contacting adult inner hair cells. These results suggest that spatial gradients in ribbon size develop in the absence of sensory experience.
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