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Dulon D, de Monvel JB, Plion B, Mallet A, Petit C, Condamine S, Bouleau Y, Safieddine S. A free intravesicular C-terminal of otoferlin is essential for synaptic vesicle docking and fusion at auditory inner hair cell ribbon synapses. Prog Neurobiol 2024; 240:102658. [PMID: 39103114 DOI: 10.1016/j.pneurobio.2024.102658] [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: 03/21/2024] [Revised: 07/27/2024] [Accepted: 07/30/2024] [Indexed: 08/07/2024]
Abstract
Our understanding of how otoferlin, the major calcium sensor in inner hair cells (IHCs) synaptic transmission, contributes to the overall dynamics of synaptic vesicle (SV) trafficking remains limited. To address this question, we generated a knock-in mouse model expressing an otoferlin-GFP protein, where GFP was fused to its C-terminal transmembrane domain. Similar to the wild type protein, the GFP-tagged otoferlin showed normal expression and was associated with IHC SV. Surprisingly, while the heterozygote Otof+/GFP mice exhibited a normal hearing function, homozygote OtofGFP/GFP mice were profoundly deaf attributed to severe reduction in SV exocytosis. Fluorescence recovery after photobleaching revealed a markedly increased mobile fraction of the otof-GFP-associated SV in Otof GFP/GFP IHCs. Correspondingly, 3D-electron tomographic of the ribbon synapses indicated a reduced density of SV attached to the ribbon active zone. Collectively, these results indicate that otoferlin requires a free intravesicular C-terminal end for normal SV docking and fusion.
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Affiliation(s)
- Didier Dulon
- Institut Pasteur, Université Paris Cité, Inserm U06, Institut de l'Audition, Paris, France; Bordeaux Neurocampus, Université de Bordeaux, Bordeaux 33076, France.
| | | | - Baptiste Plion
- Institut Pasteur, Université Paris Cité, Inserm U06, Institut de l'Audition, Paris, France
| | - Adeline Mallet
- Institut Pasteur, Université Paris Cité, Inserm U06, Institut de l'Audition, Paris, France
| | - Christine Petit
- Institut Pasteur, Université Paris Cité, Inserm U06, Institut de l'Audition, Paris, France
| | - Steven Condamine
- Institut Pasteur, Université Paris Cité, Inserm U06, Institut de l'Audition, Paris, France; Bordeaux Neurocampus, Université de Bordeaux, Bordeaux 33076, France
| | - Yohan Bouleau
- Institut Pasteur, Université Paris Cité, Inserm U06, Institut de l'Audition, Paris, France; Bordeaux Neurocampus, Université de Bordeaux, Bordeaux 33076, France
| | - Saaid Safieddine
- Institut Pasteur, Université Paris Cité, Inserm U06, Institut de l'Audition, Paris, France; Centre National de la Recherche Scientifique, Paris, France.
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Leclère JC, Dulon D. Otoferlin as a multirole Ca 2+ signaling protein: from inner ear synapses to cancer pathways. Front Cell Neurosci 2023; 17:1197611. [PMID: 37538852 PMCID: PMC10394277 DOI: 10.3389/fncel.2023.1197611] [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: 03/31/2023] [Accepted: 06/28/2023] [Indexed: 08/05/2023] Open
Abstract
Humans have six members of the ferlin protein family: dysferlin, myoferlin, otoferlin, fer1L4, fer1L5, and fer1L6. These proteins share common features such as multiple Ca2+-binding C2 domains, FerA domains, and membrane anchoring through their single C-terminal transmembrane domain, and are believed to play a key role in calcium-triggered membrane fusion and vesicle trafficking. Otoferlin plays a crucial role in hearing and vestibular function. In this review, we will discuss how we see otoferlin working as a Ca2+-dependent mechanical sensor regulating synaptic vesicle fusion at the hair cell ribbon synapses. Although otoferlin is also present in the central nervous system, particularly in the cortex and amygdala, its role in brain tissues remains unknown. Mutations in the OTOF gene cause one of the most frequent genetic forms of congenital deafness, DFNB9. These mutations produce severe to profound hearing loss due to a defect in synaptic excitatory glutamatergic transmission between the inner hair cells and the nerve fibers of the auditory nerve. Gene therapy protocols that allow normal rescue expression of otoferlin in hair cells have just started and are currently in pre-clinical phase. In parallel, studies have linked ferlins to cancer through their effect on cell signaling and development, allowing tumors to form and cancer cells to adapt to a hostile environment. Modulation by mechanical forces and Ca2+ signaling are key determinants of the metastatic process. Although ferlins importance in cancer has not been extensively studied, data show that otoferlin expression is significantly associated with survival in specific cancer types, including clear cell and papillary cell renal carcinoma, and urothelial bladder cancer. These findings indicate a role for otoferlin in the carcinogenesis of these tumors, which requires further investigation to confirm and understand its exact role, particularly as it varies by tumor site. Targeting this protein may lead to new cancer therapies.
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Affiliation(s)
- Jean-Christophe Leclère
- Department of Head and Neck Surgery, Brest University Hospital, Brest, France
- Laboratory of Neurophysiologie de la Synapse Auditive, Université de Bordeaux, Bordeaux, France
| | - Didier Dulon
- Laboratory of Neurophysiologie de la Synapse Auditive, Université de Bordeaux, Bordeaux, France
- Institut de l’Audition, Institut Pasteur & INSERM UA06, Paris, France
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3
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Generation of innervated cochlear organoid recapitulates early development of auditory unit. Stem Cell Reports 2022; 18:319-336. [PMID: 36584686 PMCID: PMC9860115 DOI: 10.1016/j.stemcr.2022.11.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 11/28/2022] [Accepted: 11/30/2022] [Indexed: 12/30/2022] Open
Abstract
Functional cochlear hair cells (HCs) innervated by spiral ganglion neurons (SGNs) are essential for hearing, whereas robust models that recapitulate the peripheral auditory circuity are still lacking. Here, we developed cochlear organoids with functional peripheral auditory circuity in a staging three-dimensional (3D) co-culture system by initially reprogramming cochlear progenitor cells (CPCs) with increased proliferative potency that could be long-term expanded, then stepwise inducing the differentiation of cochlear HCs, as well as the outgrowth of neurites from SGNs. The function of HCs and synapses within organoids was confirmed by a series of morphological and electrophysiological evaluations. Single-cell mRNA sequencing revealed the differentiation trajectories of CPCs toward the major cochlear cell types and the dynamic gene expression during organoid HC development, which resembled the pattern of native HCs. We established the cochlear organoids with functional synapses for the first time, which provides a platform for deciphering the mechanisms of sensorineural hearing loss.
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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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Spaiardi P, Marcotti W, Masetto S, Johnson SL. Signal transmission in mature mammalian vestibular hair cells. Front Cell Neurosci 2022; 16:806913. [PMID: 35936492 PMCID: PMC9353129 DOI: 10.3389/fncel.2022.806913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 06/27/2022] [Indexed: 11/13/2022] Open
Abstract
The maintenance of balance and gaze relies on the faithful and rapid signaling of head movements to the brain. In mammals, vestibular organs contain two types of sensory hair cells, type-I and type-II, which convert the head motion-induced movement of their hair bundles into a graded receptor potential that drives action potential activity in their afferent fibers. While signal transmission in both hair cell types involves Ca2+-dependent quantal release of glutamate at ribbon synapses, type-I cells appear to also exhibit a non-quantal mechanism that is believed to increase transmission speed. However, the reliance of mature type-I hair cells on non-quantal transmission remains unknown. Here we investigated synaptic transmission in mammalian utricular hair cells using patch-clamp recording of Ca2+ currents and changes in membrane capacitance (ΔCm). We found that mature type-II hair cells showed robust exocytosis with a high-order dependence on Ca2+ entry. By contrast, exocytosis was approximately 10 times smaller in type-I hair cells. Synaptic vesicle exocytosis was largely absent in mature vestibular hair cells of CaV1.3 (CaV1.3−/−) and otoferlin (Otof−/−) knockout mice. Even though Ca2+-dependent exocytosis was small in type-I hair cells of wild-type mice, or absent in CaV1.3−/− and Otof−/−mice, these cells were able to drive action potential activity in the postsynaptic calyces. This supports a functional role for non-quantal synaptic transmission in type-I cells. The large vesicle pools in type-II cells would facilitate sustained transmission of tonic or low-frequency signals. In type-I cells, the restricted vesicle pool size, together with a rapid non-quantal mechanism, could allow them to sustain high-frequency phasic signal transmission at their specialized large calyceal synapses.
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Affiliation(s)
- Paolo Spaiardi
- Department of Brain and Behavioural Sciences, University of Pavia, Pavia, Italy
- Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
| | - Walter Marcotti
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom
- Sheffield Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Sergio Masetto
- Department of Brain and Behavioural Sciences, University of Pavia, Pavia, Italy
| | - Stuart L. Johnson
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom
- Sheffield Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
- *Correspondence: Stuart L. Johnson
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6
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Moglie MJ, Wengier DL, Elgoyhen AB, Goutman JD. Synaptic Contributions to Cochlear Outer Hair Cell Ca 2+ Dynamics. J Neurosci 2021; 41:6812-6821. [PMID: 34253627 PMCID: PMC8360681 DOI: 10.1523/jneurosci.3008-20.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 05/30/2021] [Accepted: 07/05/2021] [Indexed: 11/21/2022] Open
Abstract
For normal cochlear function, outer hair cells (OHCs) require a precise control of intracellular Ca2+ levels. In the absence of regulatory elements such as proteinaceous buffers or extrusion pumps, OHCs degenerate, leading to profound hearing impairment. Influx of Ca2+ occurs both at the stereocilia tips and the basolateral membrane. In this latter compartment, two different origins for Ca2+ influx have been poorly explored: voltage-gated L-type Ca2+ channels (VGCCs) at synapses with Type II afferent neurons, and α9α10 cholinergic nicotinic receptors at synapses with medio-olivochlear complex (MOC) neurons. Using functional imaging in mouse OHCs, we dissected Ca2+ influx individually through each of these sources, either by applying step depolarizations to activate VGCC, or stimulating MOC axons. Ca2+ ions originated in MOC synapses, but not by VGCC activation, was confined by Ca2+-ATPases most likely present in nearby synaptic cisterns. Although Ca2+ currents in OHCs are small, VGCC Ca2+ signals were comparable in size to those elicited by α9α10 receptors, and were potentiated by ryanodine receptors (RyRs). In contrast, no evidence of potentiation by RyRs was found for MOC Ca2+ signals over a wide range of presynaptic stimulation strengths. Our study shows that despite the fact that these two Ca2+ entry sites are closely positioned, they differ in their regulation by intracellular cisterns and/or organelles, suggesting the existence of well-tuned mechanisms to separate the two different OHC synaptic functions.SIGNIFICANCE STATEMENT Outer hair cells (OHCs) are sensory cells in the inner ear operating under very special constraints. Acoustic stimulation leads to fast changes both in membrane potential and in the intracellular concentration of metabolites such as Ca2+ Tight mechanisms for Ca2+ control in OHCs have been reported. Interestingly, Ca2+ is crucial for two important synaptic processes: inhibition by efferent cholinergic neurons, and glutamate release onto Type II afferent fibers. In the current study we functionally imaged Ca2+ at these two different synapses, showing close positioning within the basolateral compartment of OHCs. In addition, we show differential regulation of these two Ca2+ sources by synaptic cisterns and/or organelles, which could result crucial for functional segregation during normal hearing.
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Affiliation(s)
- Marcelo J Moglie
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI) (Consejo Nacional de Investigaciones Científicas y Tecnológicas), Ciudad Autónoma de Buenos Aires 1428, Argentina
| | - Diego L Wengier
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI) (Consejo Nacional de Investigaciones Científicas y Tecnológicas), Ciudad Autónoma de Buenos Aires 1428, Argentina
| | - A Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI) (Consejo Nacional de Investigaciones Científicas y Tecnológicas), Ciudad Autónoma de Buenos Aires 1428, Argentina
| | - Juan D Goutman
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI) (Consejo Nacional de Investigaciones Científicas y Tecnológicas), Ciudad Autónoma de Buenos Aires 1428, Argentina
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7
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Kitcher SR, Pederson AM, Weisz CJC. Diverse identities and sites of action of cochlear neurotransmitters. Hear Res 2021; 419:108278. [PMID: 34108087 DOI: 10.1016/j.heares.2021.108278] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 04/30/2021] [Accepted: 05/18/2021] [Indexed: 11/18/2022]
Abstract
Accurate encoding of acoustic stimuli requires temporally precise responses to sound integrated with cellular mechanisms that encode the complexity of stimuli over varying timescales and orders of magnitude of intensity. Sound in mammals is initially encoded in the cochlea, the peripheral hearing organ, which contains functionally specialized cells (including hair cells, afferent and efferent neurons, and a multitude of supporting cells) to allow faithful acoustic perception. To accomplish the demanding physiological requirements of hearing, the cochlea has developed synaptic arrangements that operate over different timescales, with varied strengths, and with the ability to adjust function in dynamic hearing conditions. Multiple neurotransmitters interact to support the precision and complexity of hearing. Here, we review the location of release, action, and function of neurotransmitters in the mammalian cochlea with an emphasis on recent work describing the complexity of signaling.
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Affiliation(s)
- Siân R Kitcher
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Alia M Pederson
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States.
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Huang G, Eckrich S. Quantitative Fluorescent in situ Hybridization Reveals Differential Transcription Profile Sharpening of Endocytic Proteins in Cochlear Hair Cells Upon Maturation. Front Cell Neurosci 2021; 15:643517. [PMID: 33716676 PMCID: PMC7952526 DOI: 10.3389/fncel.2021.643517] [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: 12/18/2020] [Accepted: 02/09/2021] [Indexed: 12/04/2022] Open
Abstract
The organ of Corti (OC) comprises two types of sensory cells: outer hair cells (OHCs) and inner hair cells (IHCs). While both are mechanotransducers, OHCs serve as cochlear amplifiers, whereas IHCs transform sound into transmitter release. Reliable sound encoding is ensured by indefatigable exocytosis of synaptic vesicles associated with efficient replenishment of the vesicle pool. Vesicle reformation requires retrieval of vesicle membrane from the hair cell’s membrane via endocytosis. So far, the protein machinery for endocytosis in pre-mature and terminally differentiated hair cells has only partially been deciphered. Here, we studied three endocytic proteins, dynamin-1, dynamin-3, and endophilin-A1, by assessing their transcription profiles in pre-mature and mature mouse OCs. State-of-the-art RNAscope® fluorescent in situ hybridization (FISH) of whole-mount OCs was used for quantification of target mRNAs on single-cell level. We found that pre-mature IHCs contained more mRNA transcripts of dnm1 (encoding dynamin-1) and sh3gl2 (endophilin-A1), but less of dnm3 (dynamin-3) than OHCs. These differential transcription profiles between OHCs and IHCs were sharpened upon maturation. It is noteworthy that low but heterogeneous signal numbers were found between individual negative controls, which highlights the importance of corresponding analyses in RNAscope® assays. Complementary immunolabeling revealed strong expression of dynamin-1 in the soma of mature IHCs, which was much weaker in pre-mature IHCs. By contrast, dynamin-3 was predominantly found in the soma and at the border of the cuticular plates of pre-mature and mature OHCs. In summary, using quantitative RNAscope® FISH and immunohistochemistry on whole-mount tissue of both pre-mature and mature OCs, we disclosed the cellular upregulation of endocytic proteins at the level of transcription/translation during terminal differentiation of the OC. Dynamin-1 and endophilin-A1 likely contribute to the strengthening of the endocytic machinery in IHCs after the onset of hearing, whereas expression of dynamin-3 at the cuticular plate of pre-mature and mature OHCs suggests its possible involvement in activity-independent apical endocytosis.
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Affiliation(s)
- Guobin Huang
- Center for Integrative Physiology and Molecular Medicine, School of Medicine, Department of Biophysics, Saarland University, Homburg, Germany
| | - Stephanie Eckrich
- Center for Integrative Physiology and Molecular Medicine, School of Medicine, Department of Biophysics, Saarland University, Homburg, Germany
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9
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Vona B, Rad A, Reisinger E. The Many Faces of DFNB9: Relating OTOF Variants to Hearing Impairment. Genes (Basel) 2020; 11:genes11121411. [PMID: 33256196 PMCID: PMC7768390 DOI: 10.3390/genes11121411] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 11/23/2020] [Accepted: 11/25/2020] [Indexed: 01/05/2023] Open
Abstract
The OTOF gene encodes otoferlin, a critical protein at the synapse of auditory sensory cells, the inner hair cells (IHCs). In the absence of otoferlin, signal transmission of IHCs fails due to impaired release of synaptic vesicles at the IHC synapse. Biallelic pathogenic and likely pathogenic variants in OTOF predominantly cause autosomal recessive profound prelingual deafness, DFNB9. Due to the isolated defect of synaptic transmission and initially preserved otoacoustic emissions (OAEs), the clinical characteristics have been termed "auditory synaptopathy". We review the broad phenotypic spectrum reported in patients with variants in OTOF that includes milder hearing loss, as well as progressive and temperature-sensitive hearing loss. We highlight several challenges that must be addressed for rapid clinical and genetic diagnosis. Importantly, we call for changes in newborn hearing screening protocols, since OAE tests fail to diagnose deafness in this case. Continued research appears to be needed to complete otoferlin isoform expression characterization to enhance genetic diagnostics. This timely review is meant to sensitize the field to clinical characteristics of DFNB9 and current limitations in preparation for clinical trials for OTOF gene therapies that are projected to start in 2021.
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10
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Jovanovic S, Milenkovic I. Purinergic Modulation of Activity in the Developing Auditory Pathway. Neurosci Bull 2020; 36:1285-1298. [PMID: 33040238 DOI: 10.1007/s12264-020-00586-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 09/10/2020] [Indexed: 12/11/2022] Open
Abstract
Purinergic P2 receptors, activated by endogenous ATP, are prominently expressed on neuronal and non-neuronal cells during development of the auditory periphery and central auditory neurons. In the mature cochlea, extracellular ATP contributes to ion homeostasis, and has a protective function against noise exposure. Here, we focus on the modulation of activity by extracellular ATP during early postnatal development of the lower auditory pathway. In mammals, spontaneous patterned activity is conveyed along afferent auditory pathways before the onset of acoustically evoked signal processing. During this critical developmental period, inner hair cells fire bursts of action potentials that are believed to provide a developmental code for synaptic maturation and refinement of auditory circuits, thereby establishing a precise tonotopic organization. Endogenous ATP-release triggers such patterned activity by raising the extracellular K+ concentration and contributes to firing by increasing the excitability of auditory nerve fibers, spiral ganglion neurons, and specific neuron types within the auditory brainstem, through the activation of diverse P2 receptors. We review recent studies that provide new models on the contribution of purinergic signaling to early development of the afferent auditory pathway. Further, we discuss potential future directions of purinergic research in the auditory system.
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Affiliation(s)
- Sasa Jovanovic
- School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany
| | - Ivan Milenkovic
- School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany.
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11
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Jeng JY, Ceriani F, Hendry A, Johnson SL, Yen P, Simmons DD, Kros CJ, Marcotti W. Hair cell maturation is differentially regulated along the tonotopic axis of the mammalian cochlea. J Physiol 2019; 598:151-170. [PMID: 31661723 PMCID: PMC6972525 DOI: 10.1113/jp279012] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 10/24/2019] [Indexed: 12/15/2022] Open
Abstract
Key points Outer hair cells (OHCs) enhance the sensitivity and the frequency tuning of the mammalian cochlea. Similar to the primary sensory receptor, the inner hair cells (IHCs), the mature functional characteristics of OHCs are acquired before hearing onset. We found that OHCs, like IHCs, fire spontaneous Ca2+‐induced action potentials (APs) during immature stages of development, which are driven by CaV1.3 Ca2+ channels. We also showed that the development of low‐ and high‐frequency hair cells is differentially regulated during pre‐hearing stages, with the former cells being more strongly dependent on experience‐independent Ca2+ action potential activity.
Abstract Sound amplification within the mammalian cochlea depends upon specialized hair cells, the outer hair cells (OHCs), which possess both sensory and motile capabilities. In various altricial rodents, OHCs become functionally competent from around postnatal day 7 (P7), before the primary sensory inner hair cells (IHCs), which become competent at about the onset of hearing (P12). The mechanisms responsible for the maturation of OHCs and their synaptic specialization remain poorly understood. We report that spontaneous Ca2+ activity in the immature cochlea, which is generated by CaV1.3 Ca2+ channels, differentially regulates the maturation of hair cells along the cochlea. Under near‐physiological recording conditions we found that, similar to IHCs, immature OHCs elicited spontaneous Ca2+ action potentials (APs), but only during the first few postnatal days. Genetic ablation of these APs in vivo, using CaV1.3−/− mice, prevented the normal developmental acquisition of mature‐like basolateral membrane currents in low‐frequency (apical) hair cells, such as IK,n (carried by KCNQ4 channels), ISK2 and IACh (α9α10nAChRs) in OHCs and IK,n and IK,f (BK channels) in IHCs. Electromotility and prestin expression in OHCs were normal in CaV1.3−/− mice. The maturation of high‐frequency (basal) hair cells was also affected in CaV1.3−/− mice, but to a much lesser extent than apical cells. However, a characteristic feature in CaV1.3−/− mice was the reduced hair cell size irrespective of their cochlear location. We conclude that the development of low‐ and high‐frequency hair cells is differentially regulated during development, with apical cells being more strongly dependent on experience‐independent Ca2+ APs. Outer hair cells (OHCs) enhance the sensitivity and the frequency tuning of the mammalian cochlea. Similar to the primary sensory receptor, the inner hair cells (IHCs), the mature functional characteristics of OHCs are acquired before hearing onset. We found that OHCs, like IHCs, fire spontaneous Ca2+‐induced action potentials (APs) during immature stages of development, which are driven by CaV1.3 Ca2+ channels. We also showed that the development of low‐ and high‐frequency hair cells is differentially regulated during pre‐hearing stages, with the former cells being more strongly dependent on experience‐independent Ca2+ action potential activity.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Aenea Hendry
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Piece Yen
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | | | - Corné J Kros
- School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
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12
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Johnson SL, Safieddine S, Mustapha M, Marcotti W. Hair Cell Afferent Synapses: Function and Dysfunction. Cold Spring Harb Perspect Med 2019; 9:a033175. [PMID: 30617058 PMCID: PMC6886459 DOI: 10.1101/cshperspect.a033175] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To provide a meaningful representation of the auditory landscape, mammalian cochlear hair cells are optimized to detect sounds over an incredibly broad range of frequencies and intensities with unparalleled accuracy. This ability is largely conferred by specialized ribbon synapses that continuously transmit acoustic information with high fidelity and sub-millisecond precision to the afferent dendrites of the spiral ganglion neurons. To achieve this extraordinary task, ribbon synapses employ a unique combination of molecules and mechanisms that are tailored to sounds of different frequencies. Here we review the current understanding of how the hair cell's presynaptic machinery and its postsynaptic afferent connections are formed, how they mature, and how their function is adapted for an accurate perception of sound.
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Affiliation(s)
- Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Saaid Safieddine
- UMRS 1120, Institut Pasteur, Paris, France
- Sorbonne Universités, UPMC Université Paris 06, Complexité du Vivant, Paris, France
| | - Mirna Mustapha
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California 94035
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
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13
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Manchanda A, Chatterjee P, Bonventre JA, Haggard DE, Kindt KS, Tanguay RL, Johnson CP. Otoferlin Depletion Results in Abnormal Synaptic Ribbons and Altered Intracellular Calcium Levels in Zebrafish. Sci Rep 2019; 9:14273. [PMID: 31582816 PMCID: PMC6776657 DOI: 10.1038/s41598-019-50710-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 09/13/2019] [Indexed: 01/10/2023] Open
Abstract
The protein otoferlin plays an essential role at the sensory hair cell synapse. Mutations in otoferlin result in deafness and depending on the species, mild to strong vestibular deficits. While studies in mouse models suggest a role for otoferlin in synaptic vesicle exocytosis and endocytosis, it is unclear whether these functions are conserved across species. To address this question, we characterized the impact of otoferlin depletion in zebrafish larvae and found defects in synaptic vesicle recycling, abnormal synaptic ribbons, and higher resting calcium concentrations in hair cells. We also observed abnormal expression of the calcium binding hair cell genes s100s and parvalbumin, as well as the nogo related proteins rtn4rl2a and rtn4rl2b. Exogenous otoferlin partially restored expression of genes affected by endogenous otoferlin depletion. Our results suggest that in addition to vesicle recycling, depletion of otoferlin disrupts resting calcium levels, alters synaptic ribbon architecture, and perturbs transcription of hair cells specific genes during zebrafish development.
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Affiliation(s)
- Aayushi Manchanda
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, Oregon, USA
| | - Paroma Chatterjee
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, Oregon, USA
| | - Josephine A Bonventre
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon, USA
| | - Derik E Haggard
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon, USA
| | - Katie S Kindt
- National Institute of Deafness and Other Communication Disorders (NIDCD), NIH, Maryland, USA
| | - Robert L Tanguay
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, Oregon, USA
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon, USA
| | - Colin P Johnson
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, Oregon, USA.
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon, USA.
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14
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Al-Moyed H, Cepeda AP, Jung S, Moser T, Kügler S, Reisinger E. A dual-AAV approach restores fast exocytosis and partially rescues auditory function in deaf otoferlin knock-out mice. EMBO Mol Med 2019; 11:emmm.201809396. [PMID: 30509897 PMCID: PMC6328916 DOI: 10.15252/emmm.201809396] [Citation(s) in RCA: 115] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Normal hearing and synaptic transmission at afferent auditory inner hair cell (IHC) synapses require otoferlin. Deafness DFNB9, caused by mutations in the OTOF gene encoding otoferlin, might be treated by transferring wild‐type otoferlin cDNA into IHCs, which is difficult due to the large size of this transgene. In this study, we generated two adeno‐associated viruses (AAVs), each containing half of the otoferlin cDNA. Co‐injecting these dual‐AAV2/6 half‐vectors into the cochleae of 6‐ to 7‐day‐old otoferlin knock‐out (Otof−/−) mice led to the expression of full‐length otoferlin in up to 50% of IHCs. In the cochlea, otoferlin was selectively expressed in auditory hair cells. Dual‐AAV transduction of Otof−/−IHCs fully restored fast exocytosis, while otoferlin‐dependent vesicle replenishment reached 35–50% of wild‐type levels. The loss of 40% of synaptic ribbons in these IHCs could not be prevented, indicating a role of otoferlin in early synapse maturation. Acoustic clicks evoked auditory brainstem responses with thresholds of 40–60 dB. Therefore, we propose that gene delivery mediated by dual‐AAV vectors might be suitable to treat deafness forms caused by mutations in large genes such as OTOF.
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Affiliation(s)
- Hanan Al-Moyed
- Molecular Biology of Cochlear Neurotransmission Group, Department of Otorhinolaryngology, University Medical Center Göttingen, and Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Andreia P Cepeda
- Molecular Biology of Cochlear Neurotransmission Group, Department of Otorhinolaryngology, University Medical Center Göttingen, and Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - SangYong Jung
- Institute for Auditory Neurosciences and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Tobias Moser
- Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,Institute for Auditory Neurosciences and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Sebastian Kügler
- Center Nanoscale Microscopy and Physiology of the Brain (CNMPB), Department of Neurology, University Medical Center Göttingen, Göttingen, Germany
| | - 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
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15
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Phase Locking of Auditory-Nerve Fibers Reveals Stereotyped Distortions and an Exponential Transfer Function with a Level-Dependent Slope. J Neurosci 2019; 39:4077-4099. [PMID: 30867259 DOI: 10.1523/jneurosci.1801-18.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 02/28/2019] [Accepted: 03/07/2019] [Indexed: 12/16/2022] Open
Abstract
Phase locking of auditory-nerve-fiber (ANF) responses to the fine structure of acoustic stimuli is a hallmark of the auditory system's temporal precision and is important for many aspects of hearing. Period histograms from phase-locked ANF responses to low-frequency tones exhibit spike-rate and temporal asymmetries, but otherwise retain an approximately sinusoidal shape as stimulus level increases, even beyond the level at which the mean spike rate saturates. This is intriguing because apical cochlear mechanical vibrations show little compression, and mechanoelectrical transduction in the receptor cells is thought to obey a static sigmoidal nonlinearity, which might be expected to produce peak clipping at moderate and high stimulus levels. Here we analyze phase-locked responses of ANFs from cats of both sexes. We show that the lack of peak clipping is due neither to ANF refractoriness nor to spike-rate adaptation on time scales longer than the stimulus period. We demonstrate that the relationship between instantaneous pressure and instantaneous rate is well described by an exponential function whose slope decreases with increasing stimulus level. Relatively stereotyped harmonic distortions in the input to the exponential can account for the temporal asymmetry of the period histograms, including peak splitting. We show that the model accounts for published membrane-potential waveforms when assuming a power-of-three, but not a power-of-one, relationship to exocytosis. Finally, we demonstrate the relationship between the exponential transfer functions and the sigmoidal pseudotransducer functions obtained in the literature by plotting the maxima and minima of the voltage responses against the maxima and minima of the stimuli.SIGNIFICANCE STATEMENT Phase locking of auditory-nerve-fiber responses to the temporal fine structure of acoustic stimuli is important for many aspects of hearing, but the mechanisms underlying phase locking are not fully understood. Intriguingly, period histograms retain an approximately sinusoidal shape across sound levels, even when the mean rate has saturated. We find that neither refractoriness nor spike-rate adaptation is responsible for this behavior. Instead, the peripheral auditory system operates as though it contains an exponential transfer function whose slope changes with stimulus level. The underlying mechanism is distinct from the comparatively weak cochlear mechanical compression in the cochlear apex, and likely resides in the receptor cells.
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16
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Ceriani F, Hendry A, Jeng JY, Johnson SL, Stephani F, Olt J, Holley MC, Mammano F, Engel J, Kros CJ, Simmons DD, Marcotti W. Coordinated calcium signalling in cochlear sensory and non-sensory cells refines afferent innervation of outer hair cells. EMBO J 2019; 38:embj.201899839. [PMID: 30804003 PMCID: PMC6484507 DOI: 10.15252/embj.201899839] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 12/11/2018] [Accepted: 01/18/2019] [Indexed: 12/12/2022] Open
Abstract
Outer hair cells (OHCs) are highly specialized sensory cells conferring the fine‐tuning and high sensitivity of the mammalian cochlea to acoustic stimuli. Here, by genetically manipulating spontaneous Ca2+ signalling in mice in vivo, through a period of early postnatal development, we find that the refinement of OHC afferent innervation is regulated by complementary spontaneous Ca2+ signals originating in OHCs and non‐sensory cells. OHCs fire spontaneous Ca2+ action potentials during a narrow period of neonatal development. Simultaneously, waves of Ca2+ activity in the non‐sensory cells of the greater epithelial ridge cause, via ATP‐induced activation of P2X3 receptors, the increase and synchronization of the Ca2+ activity in nearby OHCs. This synchronization is required for the refinement of their immature afferent innervation. In the absence of connexin channels, Ca2+ waves are impaired, leading to a reduction in the number of ribbon synapses and afferent fibres on OHCs. We propose that the correct maturation of the afferent connectivity of OHCs requires experience‐independent Ca2+ signals from sensory and non‐sensory cells.
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Affiliation(s)
- Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Aenea Hendry
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Friederike Stephani
- Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Jennifer Olt
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Matthew C Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Fabio Mammano
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padova, Italy.,Department of Biomedical Sciences, Institute of Cell Biology and Neurobiology, Italian National Research Council, Monterotondo, Italy
| | - Jutta Engel
- Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Corné J Kros
- School of Life Sciences, University of Sussex, Brighton, UK
| | | | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
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17
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Bonventre JA, Holman C, Manchanda A, Codding SJ, Chau T, Huegel J, Barton C, Tanguay R, Johnson CP. Fer1l6 is essential for the development of vertebrate muscle tissue in zebrafish. Mol Biol Cell 2018; 30:293-301. [PMID: 30516436 PMCID: PMC6589578 DOI: 10.1091/mbc.e18-06-0401] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The precise spatial and temporal expression of genes is essential for proper organismal development. Despite their importance, however, many developmental genes have yet to be identified. We have determined that Fer1l6, a member of the ferlin family of genes, is a novel factor in zebrafish development. We find that Fer1l6 is expressed broadly in the trunk and head of zebrafish larvae and is more restricted to gills and female gonads in adult zebrafish. Using both genetic mutant and morpholino knockdown models, we found that loss of Fer1l6 led to deformation of striated muscle tissues, delayed development of the heart, and high morbidity. Further, expression of genes associated with muscle cell proliferation and differentiation were affected. Fer1l6 was also detected in the C2C12 cell line, and unlike other ferlin homologues, we found Fer1l6 expression was independent of the myoblast-to-myotube transition. Finally, analysis of cell and recombinant protein-based assays indicate that Fer1l6 colocalizes with syntaxin 4 and vinculin, and that the putative C2 domains interact with lipid membranes. We conclude that Fer1l6 has diverged from other vertebrate ferlins to play an essential role in zebrafish skeletal and cardiac muscle development.
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Affiliation(s)
- Josephine A Bonventre
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331
| | - Chelsea Holman
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331
| | - Aayushi Manchanda
- Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR 97331
| | - Sara J Codding
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331
| | - Trisha Chau
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331
| | - Jacob Huegel
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331
| | - Carrie Barton
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331
| | - Robert Tanguay
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331
| | - Colin P Johnson
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331.,Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR 97331
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18
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Voltage-Gated Calcium Influx Modifies Cholinergic Inhibition of Inner Hair Cells in the Immature Rat Cochlea. J Neurosci 2018; 38:5677-5687. [PMID: 29789373 DOI: 10.1523/jneurosci.0230-18.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 05/14/2018] [Accepted: 05/16/2018] [Indexed: 11/21/2022] Open
Abstract
Until postnatal day (P) 12, inner hair cells of the rat cochlea are invested with both afferent and efferent synaptic connections. With the onset of hearing at P12, the efferent synapses disappear, and afferent (ribbon) synapses operate with greater efficiency. This change coincides with increased expression of voltage-gated potassium channels, the loss of calcium-dependent electrogenesis, and the onset of graded receptor potentials driven by sound. The transient efferent synapses include near-membrane postsynaptic cisterns thought to regulate calcium influx through the hair cell's α9-containing and α10-containing nicotinic acetylcholine receptors. This influx activates small-conductance Ca2+-activated K+ (SK) channels. Serial-section electron microscopy of inner hair cells from two 9-d-old (male) rat pups revealed many postsynaptic efferent cisterns and presynaptic afferent ribbons whose average minimal separation in five cells ranged from 1.1 to 1.7 μm. Efferent synaptic function was studied in rat pups (age, 7-9 d) of either sex. The duration of these SK channel-mediated IPSCs was increased by enhanced calcium influx through L-type voltage-gated channels, combined with ryanodine-sensitive release from internal stores-presumably the near-membrane postsynaptic cistern. These data support the possibility that inner hair cell calcium electrogenesis modulates the efficacy of efferent inhibition during the maturation of inner hair cell synapses.SIGNIFICANCE STATEMENT Strict calcium buffering is essential for cellular function. This problem is especially acute for compact hair cells where increasing cytoplasmic calcium promotes the opposing functions of closely adjoining afferent and efferent synapses. The near-membrane postsynaptic cistern at efferent synapses segregates synaptic calcium signals by acting as a dynamic calcium store. The hair cell serves as an informative model for synapses with postsynaptic cisterns (C synapses) found in central neurons.
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19
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Han KH, Oh DY, Lee S, Lee C, Han JH, Kim MY, Park HR, Park MK, Kim NKD, Lee J, Yi E, Kim JM, Kim JW, Chae JH, Oh SH, Park WY, Choi BY. ATP1A3 mutations can cause progressive auditory neuropathy: a new gene of auditory synaptopathy. Sci Rep 2017; 7:16504. [PMID: 29184165 PMCID: PMC5705773 DOI: 10.1038/s41598-017-16676-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 11/16/2017] [Indexed: 12/21/2022] Open
Abstract
The etiologies and prevalence of sporadic, postlingual-onset, progressive auditory neuropathy spectrum disorder (ANSD) have rarely been documented. Thus, we aimed to evaluate the prevalence and molecular etiologies of these cases. Three out of 106 sporadic progressive hearing losses turned out to manifest ANSD. Through whole exome sequencing and subsequent bioinformatics analysis, two out of the three were found to share a de novo variant, p.E818K of ATP1A3, which had been reported to cause exclusively CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss) syndrome. However, hearing loss induced by CAPOS has never been characterized to date. Interestingly, the first proband did not manifest any features of CAPOS, except subclinical areflexia; however, the phenotypes of second proband was compatible with that of CAPOS, making this the first reported CAPOS allele in Koreans. This ANSD phenotype was compatible with known expression of ATP1A3 mainly in the synapse between afferent nerve and inner hair cells. Based on this, cochlear implantation (CI) was performed in the first proband, leading to remarkable benefits. Collectively, the de novo ATP1A3 variant can cause postlingual-onset auditory synaptopathy, making this gene a significant contributor to sporadic progressive ANSD and a biomarker ensuring favorable short-term CI outcomes.
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Affiliation(s)
- Kyu-Hee Han
- Department of Otorhinolaryngology, National Medical Center, Seoul, Korea
| | - Doo-Yi Oh
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Seungmin Lee
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Chung Lee
- Samsung Genome Institute, Samsung Medical Center, Seoul, Korea.,Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul, Korea
| | - Jin Hee Han
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Min Young Kim
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Hye-Rim Park
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Moo Kyun Park
- Department of Otorhinolaryngology, Seoul National University Hospital, Seoul, Korea
| | - Nayoung K D Kim
- Samsung Genome Institute, Samsung Medical Center, Seoul, Korea
| | - Jaekwang Lee
- Division of Functional Food Research, Korea Food Research Institute (KFRI), Seongnam, Korea
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan, Korea
| | - Jong-Min Kim
- Department of Neurology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Jeong-Whun Kim
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Jong-Hee Chae
- Department of Pediatrics, Pediatric Clinical Neuroscience Center, Seoul National University Children's Hospital, Seoul, Korea
| | - Seung Ha Oh
- Department of Otorhinolaryngology, Seoul National University Hospital, Seoul, Korea
| | - Woong-Yang Park
- Samsung Genome Institute, Samsung Medical Center, Seoul, Korea.,Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul, Korea.,Department of Molecular Cell Biology, School of Medicine, Sungkyunkwan University, Seoul, Korea
| | - Byung Yoon Choi
- Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, Korea.
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20
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Al-Wardy NM, Al-Kindi MN, Al-Khabouri MJ, Tamimi Y, Van Camp G. A novel missense mutation in the C2C domain of otoferlin causes profound hearing impairment in an Omani family with auditory neuropathy. Saudi Med J 2017; 37:1068-75. [PMID: 27652356 PMCID: PMC5075369 DOI: 10.15537/smj.2016.10.14967] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVES To identify genetic defects in an Omani family diagnosed with deafness. METHODS A cross-sectional association study was conducted at the Department of Biochemistry, College of Medicine and Health Sciences, Sultan Qaboos University, Al-Khoud, Oman and the Centre of Medical Genetics, University of Antwerp, Antwerp, Belgium between August 2010 and September 2014. Microsatellites markers for nine non-syndromic genes were used to genotype the defective locus using the extracted DNA from family members. Sanger sequencing method was used to identify the disease causative mutation. Eazy linkage 5.05 was used to calculate the logarithm of odds score. Lasergene suite was used to detect the mutation position, and Phyre2, SMART, Rasmol, and GOR IV were used to predict the effects of the defect on protein structure and function. RESULTS The disease was linked to markers located on chromosome-2 and covering the OTOF (DFNB9) gene. A novel missense mutation that changed nucleotide C to G at position c.1469 and consequently the amino acid Proline to Arginine (P490R) on exon 15 was detected. Protein modeling analysis revealed the impact of the mutation on protein structure and the relevant C2C domain. The mutation seems to create a new protein isoform homologous to the complement component C1q. CONCLUSION These findings suggest that the mutation found in C2C domain of the OTOF gene is likely to cause deafness in the studied family reflecting the importance of C2 domains of otoferlin in hearing loss.
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Affiliation(s)
- Nadia M Al-Wardy
- Department of Biochemistry, College of Medicine & Health Sciences, Sultan Qaboos University, Al-Khoud, Oman. E-mail.
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21
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Kirk ME, Meredith FL, Benke TA, Rennie KJ. AMPA receptor-mediated rapid EPSCs in vestibular calyx afferents. J Neurophysiol 2017; 117:2312-2323. [PMID: 28298303 DOI: 10.1152/jn.00394.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 03/10/2017] [Accepted: 03/10/2017] [Indexed: 01/21/2023] Open
Abstract
In the vestibular periphery neurotransmission between hair cells and primary afferent nerves occurs via specialized ribbon synapses. Type I vestibular hair cells (HCIs) make synaptic contacts with calyx terminals, which enclose most of the HCI basolateral surface. To probe synaptic transmission, whole cell patch-clamp recordings were made from calyx afferent terminals isolated together with their mature HCIs from gerbil crista. Neurotransmitter release was measured as excitatory postsynaptic currents (EPSCs) in voltage clamp. Spontaneous EPSCs were classified as simple or complex. Simple events exhibited a rapid rise time and a fast monoexponential decay (time constant < 1 ms). The remaining events, constituting ~40% of EPSCs, showed more complex characteristics. Extracellular Sr2+ greatly increased EPSC frequency, and EPSCs were blocked by the AMPA receptor blocker NBQX. The role of presynaptic Ca2+ channels was assessed by application of the L-type Ca2+ channel blocker nifedipine (20 µM), which reduced EPSC frequency. In contrast, the L-type Ca2+ channel opener BAY K 8644 increased EPSC frequency. Cyclothiazide increased the decay time constant of averaged simple EPSCs by approximately twofold. The low-affinity AMPA receptor antagonist γ-d-glutamylglycine (2 mM) reduced the proportion of simple EPSCs relative to complex events, indicating glutamate accumulation in the restricted cleft between HCI and calyx. In crista slices EPSC frequency was greater in central compared with peripheral calyces, which may be due to greater numbers of presynaptic ribbons in central hair cells. Our data support a role for L-type Ca2+ channels in spontaneous release and demonstrate regional variations in AMPA-mediated quantal transmission at the calyx synapse.NEW & NOTEWORTHY In vestibular calyx terminals of mature cristae we find that the majority of excitatory postsynaptic currents (EPSCs) are rapid monophasic events mediated by AMPA receptors. Spontaneous EPSCs are reduced by an L-type Ca2+ channel blocker and notably enhanced in extracellular Sr2+ EPSC frequency is greater in central areas of the crista compared with peripheral areas and may be associated with more numerous presynaptic ribbons in central hair cells.
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Affiliation(s)
- Matthew E Kirk
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado
| | - Frances L Meredith
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado
| | - Timothy A Benke
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado.,Departments of Pediatrics, Neurology, and Pharmacology, University of Colorado School of Medicine, Aurora, Colorado
| | - Katherine J Rennie
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado; .,Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado; and
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22
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Fedick AM, Jalas C, Swaroop A, Smouha EE, Webb BD. Identification of a novel pathogenic OTOF variant causative of nonsyndromic hearing loss with high frequency in the Ashkenazi Jewish population. APPLICATION OF CLINICAL GENETICS 2016; 9:141-6. [PMID: 27621663 PMCID: PMC5012844 DOI: 10.2147/tacg.s113828] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Mutations in the OTOF gene have previously been shown to cause nonsyndromic prelingual deafness (DFNB9, OMIM 601071) as well as auditory neuropathy/dys-synchrony. In this study, the OTOF NM_194248.2 c.5332G>T, p.Val1778Phe variant was identified in a large Ashkenazi Jewish family as the causative variant in four siblings with hearing loss. Our analysis reveals a carrier frequency of the OTOF c.5332G>T, p.Val1778Phe variant of 1.27% in the Ashkenazi Jewish population, suggesting that this variant may be a significant contributor to nonsyndromic sensorineural hearing loss and should be considered for inclusion in targeted hearing loss panels for this population. Of note, the degree of hearing loss associated with this phenotype ranged from mild to moderately severe, with two of the four siblings not known to have hearing loss until they were genotyped and underwent pure tone audiometry and auditory brainstem response testing. The phenotypic variability along with the auditory neuropathy/dys-synchrony, which allows for the production of otoacoustic emissions, supports that nonsyndromic hearing loss caused by OTOF mutations may be much more common in the Ashkenazi Jewish population than currently appreciated due to a lack of diagnosis.
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Affiliation(s)
- Anastasia M Fedick
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Chaim Jalas
- Bonei Olam, Center for Rare Jewish Genetic Disorders, Brooklyn, NY, USA
| | - Ananya Swaroop
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Eric E Smouha
- Department of Otolaryngology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Bryn D Webb
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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Sundaresan S, Balasubbu S, Mustapha M. Thyroid hormone is required for the pruning of afferent type II spiral ganglion neurons in the mouse cochlea. Neuroscience 2015; 312:165-78. [PMID: 26592716 DOI: 10.1016/j.neuroscience.2015.11.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 11/09/2015] [Accepted: 11/10/2015] [Indexed: 12/13/2022]
Abstract
Afferent connections to the sensory inner (IHCs) and outer hair cells (OHCs) in the cochlea refine and functionally mature during the thyroid hormone (TH)-critical period of inner ear development that occurs perinatally in rodents. In this study, we investigated the effects of hypothyroidism on afferent type II innervation to outer hair cells using the Snell dwarf mouse (Pit1(dw)). Using a transgenic approach to specifically label type II spiral ganglion neurons (SGNs), we found that lack of TH causes persistence of excess type II SGN connections to the OHCs, as well as continued expression of the hair cell functional marker, otoferlin (OTOF), in the OHCs beyond the maturation period. We also observed a concurrent delay in efferent attachment to the OHCs. Supplementing with TH during the early postnatal period from postnatal day (P) 3 to P4 reversed the defect in type II SGN pruning but did not alter OTOF expression. Our results show that hypothyroidism causes a defect in the large-scale pruning of afferent type II SGNs in the cochlea, and a delay in efferent attachment and the maturation of OTOF expression. Our data suggest that the state of maturation of hair cells, as determined by OTOF expression, may not regulate the pruning of their afferent innervation.
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Affiliation(s)
- S Sundaresan
- Department of Otolaryngology-Head & Neck Surgery, 300 Pasteur Drive, Stanford University, Stanford, CA 94035, United States
| | - S Balasubbu
- Department of Otolaryngology-Head & Neck Surgery, 300 Pasteur Drive, Stanford University, Stanford, CA 94035, United States
| | - M Mustapha
- Department of Otolaryngology-Head & Neck Surgery, 300 Pasteur Drive, Stanford University, Stanford, CA 94035, United States.
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24
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Chang MY, Kim AR, Kim NKD, Lee C, Park WY, Choi BY. Refinement of Molecular Diagnostic Protocol of Auditory Neuropathy Spectrum Disorder: Disclosure of Significant Level of Etiologic Homogeneity in Koreans and Its Clinical Implications. Medicine (Baltimore) 2015; 94:e1996. [PMID: 26632695 PMCID: PMC5058964 DOI: 10.1097/md.0000000000001996] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Auditory neuropathy spectrum disorder (ANSD) is a sensorineural hearing disorder caused by dysfunction of auditory neural conduction. ANSD has a heterogeneous etiology, including genetic factors; the response to cochlear implantation significantly varies depending on the etiology. The results of timely cochlear implantation for OTOF-related ANSD (DFNB9) have been reported to be good. Therefore, identifying the causative gene of ANSD, especially OTOF, is an important issue to rehabilitate these patients.Six sporadic ANSD subjects without anatomical abnormality of the cochlear nerve, including the 4 subjects that were previously reported to be without detectable OTOF mutation, were included. We performed targeted resequencing (TRS) of known deafness genes and multiphasic bioinformatics analyses of the data that ensured detection of capture failure and structural variations. Exclusion of SNP was also double checked. The TRS data previously obtained from 2 subjects were reanalyzed. Through this study, we detected 2 mutant alleles of OTOF from 5 (83.3%) of 6 ANSD subjects. All of the 5 subjects carried at least 1 mutant allele carrying p.R1939Q. This variant was categorized as a simple SNP (rs201326023) in the database and it resided in the exon with frequent capture failures, which previously led to exclusion of this variant from eligible candidacy mistakenly. In addition, we detected a structural variation within OTOF from a previously undiagnosed ANSD subject, which was the second structural variation reported in DFNB9 subjects to date.We identify a strong etiologic homogeneity of prelingual ANSD in case of the anatomically normal cochlear nerve in Koreans and now report DFNB9 as the single overwhelming cause. Multiphasic analysis of TRS data ensuring detection of capture failure and structural variations would be expected to reveal DFNB9 from a substantial portion of previously undiagnosed ANSD subjects in Koreans. Based on our results, we propose a novel strategy that incorporates imaging studies, prevalent mutation screening and multiphasic analysis of TRS data in a stepwise manner to correctly detect DFNB9 in Koreans.
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Affiliation(s)
- Mun Young Chang
- From the Department of Otorhinolaryngology, Seoul National University Hospital, Seoul National University College of Medicine (MYC, ARK); Samsung Genome Institute, Samsung Medical Center, Seoul (NKDK, CL, WYP); Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University (CL); Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon (WYP); and Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seongnam, Republic of Korea (BYC)
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25
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Fuchs PA, Glowatzki E. Synaptic studies inform the functional diversity of cochlear afferents. Hear Res 2015; 330:18-25. [PMID: 26403507 DOI: 10.1016/j.heares.2015.09.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 09/09/2015] [Accepted: 09/16/2015] [Indexed: 11/25/2022]
Abstract
Type I and type II cochlear afferents differ markedly in number, morphology and innervation pattern. The predominant type I afferents transmit the elemental features of acoustic information to the central nervous system. Excitation of these large diameter myelinated neurons occurs at a single ribbon synapse of a single inner hair cell. This solitary transmission point depends on efficient vesicular release that can produce large, rapid, suprathreshold excitatory postsynaptic potentials. In contrast, the many fewer, thinner, unmyelinated type II afferents cross the tunnel of Corti, turning basally for hundreds of microns to form contacts with ten or more outer hair cells. Although each type II afferent is postsynaptic to many outer hair cells, transmission from each occurs by the infrequent release of single vesicles, producing receptor potentials of only a few millivolts. Analysis of membrane properties and the site of spike initiation suggest that the type II afferent could be activated only if all its presynaptic outer hair cells were maximally stimulated. Thus, the details of synaptic transfer inform the functional distinctions between type I and type II afferents. High efficiency transmission across the inner hair cell's ribbon synapse supports detailed analyses of the acoustic world. The much sparser transfer from outer hair cells to type II afferents implies that these could respond only to the loudest, sustained sounds, consistent with previous reports from in vivo recordings. However, type II afferents could be excited additionally by ATP released during acoustic stress of cochlear tissues.
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Affiliation(s)
- P A Fuchs
- The Center for Hearing and Balance, Otolaryngology- Head and Neck Surgery and the Center for Sensory Biology, Institute for Basic Biomedical Sciences, the Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - E Glowatzki
- The Center for Hearing and Balance, Otolaryngology- Head and Neck Surgery and the Center for Sensory Biology, Institute for Basic Biomedical Sciences, the Johns Hopkins University School of Medicine, Baltimore, MD, USA
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26
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Wichmann C, Moser T. Relating structure and function of inner hair cell ribbon synapses. Cell Tissue Res 2015; 361:95-114. [PMID: 25874597 PMCID: PMC4487357 DOI: 10.1007/s00441-014-2102-7] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 12/18/2014] [Indexed: 01/28/2023]
Abstract
In the mammalian cochlea, sound is encoded at synapses between inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs). Each SGN receives input from a single IHC ribbon-type active zone (AZ) and yet SGNs indefatigably spike up to hundreds of Hz to encode acoustic stimuli with submillisecond precision. Accumulating evidence indicates a highly specialized molecular composition and structure of the presynapse, adapted to suit these high functional demands. However, we are only beginning to understand key features such as stimulus-secretion coupling, exocytosis mechanisms, exo-endocytosis coupling, modes of endocytosis and vesicle reformation, as well as replenishment of the readily releasable pool. Relating structure and function has become an important avenue in addressing these points and has been applied to normal and genetically manipulated hair cell synapses. Here, we review some of the exciting new insights gained from recent studies of the molecular anatomy and physiology of IHC ribbon synapses.
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Affiliation(s)
- C. Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Collaborative Research Center 889, University Medical Center Göttingen, Göttingen, Germany
| | - T. Moser
- Collaborative Research Center 889, University Medical Center Göttingen, Göttingen, Germany
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, Göttingen, Germany
- Bernstein Center for Computational Neuroscience, University of Göttingen, Göttingen, Germany
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27
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The emerging framework of mammalian auditory hindbrain development. Cell Tissue Res 2015; 361:33-48. [DOI: 10.1007/s00441-014-2110-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 12/22/2014] [Indexed: 02/06/2023]
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28
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Wright S, Hwang Y, Oertel D. Synaptic transmission between end bulbs of Held and bushy cells in the cochlear nucleus of mice with a mutation in Otoferlin. J Neurophysiol 2014; 112:3173-88. [PMID: 25253474 DOI: 10.1152/jn.00522.2014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Mice that carry a mutation in a calcium binding domain of Otoferlin, the putative calcium sensor at hair cell synapses, have normal distortion product otoacoustic emissions (DPOAEs), but auditory brain stem responses (ABRs) are absent. In mutant mice mechanotransduction is normal but transmission of acoustic information to the auditory pathway is blocked even before the onset of hearing. The cross-sectional area of the auditory nerve of mutant mice is reduced by 54%, and the volume of ventral cochlear nuclei is reduced by 46% relative to hearing control mice. While the tonotopic organization was not detectably changed in mutant mice, the axons to end bulbs of Held and the end bulbs themselves were smaller. In mutant mice bushy cells in the anteroventral cochlear nucleus (aVCN) have the electrophysiological hallmarks of control cells. Spontaneous miniature excitatory postsynaptic currents (EPSCs) occur with similar frequencies and have similar shapes in deaf as in hearing animals, but they are 24% larger in deaf mice. Bushy cells in deaf mutant mice are contacted by ∼2.6 auditory nerve fibers compared with ∼2.0 in hearing control mice. Furthermore, each fiber delivers more synaptic current, on average 4.8 nA compared with 3.4 nA, in deaf versus hearing control mice. The quantal content of evoked EPSCs is not different between mutant and control mice; the increase in synaptic current delivered in mutant mice is accounted for by the increased response to the size of the quanta. Although responses to shocks presented at long intervals are larger in mutant mice, they depress more rapidly than in hearing control mice.
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Affiliation(s)
- Samantha Wright
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin; and
| | - Youngdeok Hwang
- I.B.M. Thomas J. Watson Research Center, Yorktown Heights, New York
| | - Donata Oertel
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin; and
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Padmanarayana M, Hams N, Speight LC, Petersson EJ, Mehl RA, Johnson CP. Characterization of the lipid binding properties of Otoferlin reveals specific interactions between PI(4,5)P2 and the C2C and C2F domains. Biochemistry 2014; 53:5023-33. [PMID: 24999532 PMCID: PMC4144714 DOI: 10.1021/bi5004469] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
![]()
Otoferlin
is a transmembrane protein consisting of six C2 domains,
proposed to act as a calcium sensor for exocytosis. Although otoferlin
is believed to bind calcium and lipids, the lipid specificity and
identity of the calcium binding domains are controversial. Further,
it is currently unclear whether the calcium binding affinity of otoferlin
quantitatively matches the maximal intracellular presynaptic calcium
concentrations of ∼30–50 μM known to elicit exocytosis.
To characterize the calcium and lipid binding properties of otoferlin,
we used isothermal titration calorimetry (ITC), liposome sedimentation
assays, and fluorescence spectroscopy. Analysis of ITC data indicates
that with the exception of the C2A domain, the C2 domains of otoferlin
bind multiple calcium ions with moderate (Kd = 25–95 μM) and low affinities (Kd = 400–700 μM) in solution. However, in the presence
of liposomes, the calcium sensitivity of the domains increased by
up to 10-fold. It was also determined that calcium enhanced liposome
binding for domains C2B–C2E, whereas the C2F domain bound liposomes
in a calcium-independent manner. Mutations that abrogate calcium binding
in C2F do not disrupt liposome binding, supporting the conclusion
that the interaction of the C2F domain with phosphatidylserine is
calcium-independent. Further, domains C2C and C2F, not domains C2A,
C2B, C2D, and C2E, bound phosphatidylinositol 4,5-bisphosphate 1,2-dioleoyl-sn-glycero-3-phospho(1′-myoinositol-4′,5′-bisphosphate) [PI(4,5)P2], which preferentially
steered them toward liposomes harboring PI(4,5)P2. Remarkably, lysine
mutations L478A and L480A in C2C selectively weaken the PI(4,5)P2
interaction while leaving phosphatidylserine binding unaffected. Finally,
shifts in the emission spectra of an environmentally sensitive fluorescent
unnatural amino acid indicate that the calcium binding loops of the
C2F domain directly interact with the lipid bilayer of negatively
charged liposomes in a calcium-independent manner. On the basis of
these results, we propose that the C2F and C2C domains of otoferlin
preferentially bind PI(4,5)P2 and that PI(4,5)P2 may serve to target
otoferlin to the presynapse in a calcium-independent manner. This
positioning would facilitate fast calcium-dependent exocytosis at
the hair cell synapse.
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Affiliation(s)
- Murugesh Padmanarayana
- Department of Biochemistry and Biophysics, Oregon State University , Corvallis, Oregon 973331, United States
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30
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Jones SM, Jones TA. Genetics of peripheral vestibular dysfunction: lessons from mutant mouse strains. J Am Acad Audiol 2014; 25:289-301. [PMID: 25032973 PMCID: PMC4310552 DOI: 10.3766/jaaa.25.3.8] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND A considerable amount of research has been published about genetic hearing impairment. Fifty to sixty percent of hearing loss is thought to have a genetic cause. Genes may also play a significant role in acquired hearing loss due to aging, noise exposure, or ototoxic medications. Between 1995 and 2012, over 100 causative genes have been identified for syndromic and nonsyndromic forms of hereditary hearing loss. Mouse models have been extremely valuable in facilitating the discovery of hearing loss genes and in understanding inner ear pathology due to genetic mutations or elucidating fundamental mechanisms of inner ear development. PURPOSE Whereas much is being learned about hereditary hearing loss and the genetics of cochlear disorders, relatively little is known about the role genes may play in peripheral vestibular impairment. Here we review the literature with regard to genetics of vestibular dysfunction and discuss what we have learned from studies using mutant mouse models and direct measures of peripheral vestibular neural function. RESULTS Several genes are considered that when mutated lead to varying degrees of inner ear vestibular dysfunction due to deficits in otoconia, stereocilia, hair cells, or neurons. Behavior often does not reveal the inner ear deficit. Many of the examples presented are also known to cause human disorders. CONCLUSIONS Knowledge regarding the roles of particular genes in the operation of the vestibular sensory apparatus is growing, and it is clear that gene products co-expressed in the cochlea and vestibule may play different roles in the respective end organs. The discovery of new genes mediating critical inner ear vestibular function carries the promise of new strategies in diagnosing, treating, and managing patients as well as predicting the course and level of morbidity in human vestibular disease.
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Affiliation(s)
- Sherri M Jones
- Department of Special Education and Communication Disorders, University of Nebraska-Lincoln
| | - Timothy A Jones
- Department of Special Education and Communication Disorders, University of Nebraska-Lincoln
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31
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Ramakrishnan NA, Drescher MJ, Morley BJ, Kelley PM, Drescher DG. Calcium regulates molecular interactions of otoferlin with soluble NSF attachment protein receptor (SNARE) proteins required for hair cell exocytosis. J Biol Chem 2014; 289:8750-66. [PMID: 24478316 DOI: 10.1074/jbc.m113.480533] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mutations in otoferlin, a C2 domain-containing ferlin family protein, cause non-syndromic hearing loss in humans (DFNB9 deafness). Furthermore, transmitter secretion of cochlear inner hair cells is compromised in mice lacking otoferlin. In the present study, we show that the C2F domain of otoferlin directly binds calcium (KD = 267 μM) with diminished binding in a pachanga (D1767G) C2F mouse mutation. Calcium was found to differentially regulate binding of otoferlin C2 domains to target SNARE (t-SNARE) proteins and phospholipids. C2D-F domains interact with the syntaxin-1 t-SNARE motif with maximum binding within the range of 20-50 μM Ca(2+). At 20 μM Ca(2+), the dissociation rate was substantially lower, indicating increased binding (KD = ∼10(-9)) compared with 0 μM Ca(2+) (KD = ∼10(-8)), suggesting a calcium-mediated stabilization of the C2 domain·t-SNARE complex. C2A and C2B interactions with t-SNAREs were insensitive to calcium. The C2F domain directly binds the t-SNARE SNAP-25 maximally at 100 μM and with reduction at 0 μM Ca(2+), a pattern repeated for C2F domain interactions with phosphatidylinositol 4,5-bisphosphate. In contrast, C2F did not bind the vesicle SNARE protein synaptobrevin-1 (VAMP-1). Moreover, an antibody targeting otoferlin immunoprecipitated syntaxin-1 and SNAP-25 but not synaptobrevin-1. As opposed to an increase in binding with increased calcium, interactions between otoferlin C2F domain and intramolecular C2 domains occurred in the absence of calcium, consistent with intra-C2 domain interactions forming a "closed" tertiary structure at low calcium that "opens" as calcium increases. These results suggest a direct role for otoferlin in exocytosis and modulation of calcium-dependent membrane fusion.
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32
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Ephrin-A5/EphA4 signalling controls specific afferent targeting to cochlear hair cells. Nat Commun 2013; 4:1438. [DOI: 10.1038/ncomms2445] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 01/03/2013] [Indexed: 11/08/2022] Open
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Huang LC, Barclay M, Lee K, Peter S, Housley GD, Thorne PR, Montgomery JM. Synaptic profiles during neurite extension, refinement and retraction in the developing cochlea. Neural Dev 2012; 7:38. [PMID: 23217150 PMCID: PMC3545844 DOI: 10.1186/1749-8104-7-38] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 11/26/2012] [Indexed: 12/23/2022] Open
Abstract
Background During development, excess synapses form between the central and peripheral nervous systems that are then eliminated to achieve correct connectivity. In the peripheral auditory system, the developing type I spiral ganglion afferent fibres undergo a dramatic re-organisation, initially forming connections with both sensory inner hair cells (IHCs) and outer hair cells (OHCs). The OHC connections are then selectively eliminated, leaving sparse innervation by type II afferent fibres, whilst the type I afferent synapses with IHCs are consolidated. Results We examined the molecular makeup of the synaptic contacts formed onto the IHCs and OHCs during this period of afferent fibre remodelling. We observed that presynaptic ribbons initially form at all the afferent neurite contacts, i.e. not only at the expected developing IHC-type I fibre synapses but also at OHCs where type I fibres temporarily contact. Moreover, the transient contacts forming onto OHCs possess a broad set of pre- and postsynaptic proteins, suggesting that functional synaptic connections are formed prior to the removal of type I fibre innervation. AMPA-type glutamate receptor subunits were transiently observed at the base of the OHCs, with their downregulation occurring in parallel with the withdrawal of type I fibres, dispersal of presynaptic ribbons, and downregulation of the anchoring proteins Bassoon and Shank. Conversely, at developing type I afferent IHC synapses, the presence of pre- and postsynaptic scaffold proteins was maintained, with differential plasticity in AMPA receptor subunits observed and AMPA receptor subunit composition changing around hearing onset. Conclusions Overall our data show a differential balance in the patterns of synaptic proteins at developing afferent IHC versus OHC synapses that likely reflect their stable versus transient fates.
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Affiliation(s)
- Lin-Chien Huang
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
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34
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Kong JH, Zachary S, Rohmann KN, Fuchs PA. Retrograde facilitation of efferent synapses on cochlear hair cells. J Assoc Res Otolaryngol 2012. [PMID: 23183877 DOI: 10.1007/s10162-012-0361-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Cochlear inner hair cells (IHCs) are temporarily innervated by efferent cholinergic fibers prior to the onset of hearing. During low-frequency firing, these efferent synapses have a relatively low probability of transmitter release but facilitate strongly with repetitive stimulation. A retrograde signal from the hair cell to the efferent terminal contributes to this facilitation. When IHCs were treated with the ryanodine receptor agonist, cyclic adenosine phosphoribose (cADPR), release probability of the efferent terminal rose. This effect was quantified by computing the quantum content from a train of 100 suprathreshold stimuli to the efferent fibers. Quantum content was sevenfold higher when IHCs were treated with 100 μM cADPR (applied in the recording pipette). Since cADPR is membrane impermeant, this result implies that an extracellular messenger travels from the hair cell to the efferent terminal. cADPR is presumed to generate this messenger by increasing cytoplasmic calcium. Consistent with this presumption, voltage-gated calcium flux into the IHC also caused retrograde facilitation of efferent transmission. Retrograde facilitation was observed in IHCs of a vesicular glutamate transporter (VGlut3) null mouse and for wild-type rat hair cells subject to wide-spectrum glutamate receptor blockade, demonstrating that glutamate was unlikely to be the extracellular messenger. Rather, bath application of nitric oxide (NO) donors caused an increase in potassium-evoked efferent transmitter release while the NO scavenger carboxy-PTIO was able to prevent retrograde facilitation produced by cADPR or IHC depolarization. Thus, hair cell activity can drive retrograde facilitation of efferent input via calcium-dependent production of NO.
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MESH Headings
- Acoustic Stimulation
- Amino Acid Transport Systems, Acidic/deficiency
- Amino Acid Transport Systems, Acidic/genetics
- Amino Acid Transport Systems, Acidic/metabolism
- Animals
- Calcium/metabolism
- Calcium Channel Agonists/pharmacology
- Dose-Response Relationship, Drug
- Hair Cells, Auditory, Inner/drug effects
- Hair Cells, Auditory, Inner/physiology
- Mice
- Mice, Knockout
- Models, Animal
- Neurons, Efferent/drug effects
- Neurons, Efferent/physiology
- Nitric Oxide/metabolism
- Nitric Oxide Donors/pharmacology
- Rats
- Rats, Inbred Strains
- Synapses/drug effects
- Synapses/physiology
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
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Affiliation(s)
- Jee-Hyun Kong
- Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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35
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Otoferlin: a multi-C2 domain protein essential for hearing. Trends Neurosci 2012; 35:671-80. [DOI: 10.1016/j.tins.2012.08.002] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 07/25/2012] [Accepted: 08/13/2012] [Indexed: 12/21/2022]
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36
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Mammano F. ATP-dependent intercellular Ca2+ signaling in the developing cochlea: facts, fantasies and perspectives. Semin Cell Dev Biol 2012; 24:31-9. [PMID: 23022499 DOI: 10.1016/j.semcdb.2012.09.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 09/14/2012] [Indexed: 10/27/2022]
Abstract
Hearing relies on a sensitive mechanoelectrical transduction process in the cochlea of the inner ear. The cochlea contains sensory, secretory, neural, supporting and epithelial cells which are all essential to the sound transduction process. It is well known that a complex extracellular purinergic signaling system contributes to cochlear homeostasis, altering cochlear sensitivity and neural output via ATP-gated ion channels (P2X receptors) and G protein-coupled P2Y receptors. This review focuses on the emerging roles of ATP that are currently under investigation in the developing sensory epithelium, with particular emphasis on the link between ATP release, Ca(2+) signaling, the expression and function of gap junction proteins connexin26 and connexin30, and the acquisition of hearing.
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Affiliation(s)
- Fabio Mammano
- Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova, 35131 Padova, Italy.
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37
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Abstract
Type II cochlear afferents receive glutamatergic synaptic excitation from outer hair cells (OHCs) in the rat cochlea. However, it remains uncertain whether this connection is capable of providing auditory information to the brain. The functional efficacy of this connection depends in part on the number of presynaptic OHCs, their probability of transmitter release, and the effective electrical distance for spatial summation in the type II fiber. The present work addresses these questions using whole-cell recordings from the spiral process of type II afferents that run below OHCs in the apical turn of young (5-9 d postnatal) rat cochlea. A "high potassium puffer" was used to elicit calcium action potentials from individual OHCs and thereby show that the average probability of transmitter release was 0.26 (range 0.02-0.73). Electron microscopy showed relatively few vesicles tethered to ribbons in equivalent OHCs. A "receptive field" map for individual type II fibers was constructed by successively puffing onto OHCs along the cochlear spiral, up to 180 μm from the recording pipette. These revealed a conservative estimate of 7 presynaptic OHCs per type II fiber (range 1-11). EPSCs evoked from presynaptic OHCs separated by >100 μm did not differ in amplitude or waveform, implying that the type II fiber's length constant exceeded the length of the synaptic input zone. Together these data suggest that type II fibers could communicate centrally by maximal activation of their entire pool of presynaptic OHCs.
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38
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Bulankina AV, Moser T. Neural circuit development in the mammalian cochlea. Physiology (Bethesda) 2012; 27:100-12. [PMID: 22505666 DOI: 10.1152/physiol.00036.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The organ of Corti, the sensory epithelium of the mammalian auditory system, uses afferent and efferent synapses for encoding auditory signals and top-down modulation of cochlear function. During development, the final precisely ordered sensorineural circuit is established following excessive formation of afferent and efferent synapses and subsequent refinement. Here, we review the development of innervation of the mouse organ of Corti and its regulation.
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Affiliation(s)
- A V Bulankina
- InnerEarLab, Department of Otolaryngology, University of Goettingen School of Medicine, Goettingen, Germany
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39
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Ceriani F, Mammano F. Calcium signaling in the cochlea - Molecular mechanisms and physiopathological implications. Cell Commun Signal 2012; 10:20. [PMID: 22788415 PMCID: PMC3408374 DOI: 10.1186/1478-811x-10-20] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/12/2012] [Indexed: 12/20/2022] Open
Abstract
Calcium ions (Ca2+) regulate numerous and diverse aspects of cochlear and vestibular physiology. This review focuses on the Ca2+ control of mechanotransduction and synaptic transmission in sensory hair cells, as well as on Ca2+ signalling in non-sensory cells of the developing cochlea.
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Affiliation(s)
- Federico Ceriani
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, 35131, Padova, Italy.
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Leung C, Shaheen F, Bernatchez P, Hackett TL. Expression of myoferlin in human airway epithelium and its role in cell adhesion and zonula occludens-1 expression. PLoS One 2012; 7:e40478. [PMID: 22808170 PMCID: PMC3393691 DOI: 10.1371/journal.pone.0040478] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 06/08/2012] [Indexed: 11/18/2022] Open
Abstract
Background Normal airway epithelial barrier function is maintained by cell-cell contacts which require the translocation of adhesion proteins at the cell surface, through membrane vesicle trafficking and fusion events. Myoferlin and dysferlin, members of the multiple-C2-domain Ferlin superfamily, have been implicated in membrane fusion processes through the induction of membrane curvature. The objectives of this study were to examine the expression of dysferlin and myoferlin within the human airway and determine the roles of these proteins in airway epithelial homeostasis. Methods The expression of dysferlin and myoferlin were evaluated in normal human airway sections by immunohistochemistry, and primary human airway epithelial cells and fibroblasts by immuno blot. Localization of dysferlin and myoferlin in epithelial cells were determined using confocal microscopy. Functional outcomes analyzed included cell adhesion, protein expression, and cell detachment following dysferlin and myoferlin siRNA knock-down, using the human bronchial epithelial cell line, 16HBE. Results Primary human airway epithelial cells express both dysferlin and myoferlin whereas fibroblasts isolated from bronchi and the parenchyma only express myoferlin. Expression of dysferlin and myoferlin was further localized within the Golgi, cell cytoplasm and plasma membrane of 16HBE cells using confocal micrscopy. Treatment of 16HBE cells with myoferlin siRNA, but not dysferlin siRNA, resulted in a rounded cell morphology and loss of cell adhesion. This cell shedding following myoferlin knockdown was associated with decreased expression of tight junction molecule, zonula occludens-1 (ZO-1) and increased number of cells positive for apoptotic markers Annexin V and propidium iodide. Cell shedding was not associated with release of the innate inflammatory cytokines IL-6 and IL-8. Conclusions/Significance This study demonstrates the heterogeneous expression of myoferlin within epithelial cells and fibroblasts of the respiratory airway. The effect of myoferlin on the expression of ZO-1 in airway epithelial cells indicates its role in membrane fusion events that regulate cell detachment and apoptosis within the airway epithelium.
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Affiliation(s)
- Cleo Leung
- The James Hogg Research Centre, Institute for Heart + Lung Health, St Paul’s Hospital, Vancouver, British Columbia, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Furquan Shaheen
- The James Hogg Research Centre, Institute for Heart + Lung Health, St Paul’s Hospital, Vancouver, British Columbia, Canada
| | - Pascal Bernatchez
- The James Hogg Research Centre, Institute for Heart + Lung Health, St Paul’s Hospital, Vancouver, British Columbia, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tillie-Louise Hackett
- The James Hogg Research Centre, Institute for Heart + Lung Health, St Paul’s Hospital, Vancouver, British Columbia, Canada
- Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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Cho S, von Gersdorff H. Ca(2+) influx and neurotransmitter release at ribbon synapses. Cell Calcium 2012; 52:208-16. [PMID: 22776680 DOI: 10.1016/j.ceca.2012.06.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Revised: 06/10/2012] [Accepted: 06/13/2012] [Indexed: 12/11/2022]
Abstract
Ca(2+) influx through voltage-gated Ca(2+) channels triggers the release of neurotransmitters at presynaptic terminals. Some sensory receptor cells in the peripheral auditory and visual systems have specialized synapses that express an electron-dense organelle called a synaptic ribbon. Like conventional synapses, ribbon synapses exhibit SNARE-mediated exocytosis, clathrin-mediated endocytosis, and short-term plasticity. However, unlike non-ribbon synapses, voltage-gated L-type Ca(2+) channel opening at ribbon synapses triggers a form of multiquantal release that can be highly synchronous. Furthermore, ribbon synapses appear to be specialized for fast and high throughput exocytosis controlled by graded membrane potential changes. Here we will discuss some of the basic aspects of synaptic transmission at different types of ribbon synapses, and we will emphasize recent evidence that auditory and retinal ribbon synapses have marked differences. This will lead us to suggest that ribbon synapses are specialized for particular operating ranges and frequencies of stimulation. We propose that different types of ribbon synapses transfer diverse rates of sensory information by expressing a particular repertoire of critical components, and by placing them at precise and strategic locations, so that a continuous supply of primed vesicles and Ca(2+) influx leads to fast, accurate, and ongoing exocytosis.
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Affiliation(s)
- Soyoun Cho
- The Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
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Chen Q, Mahendrasingam S, Tickle JA, Hackney CM, Furness DN, Fettiplace R. The development, distribution and density of the plasma membrane calcium ATPase 2 calcium pump in rat cochlear hair cells. Eur J Neurosci 2012; 36:2302-10. [PMID: 22672315 DOI: 10.1111/j.1460-9568.2012.08159.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Calcium is tightly regulated in cochlear outer hair cells (OHCs). It enters mainly via mechanotransducer (MT) channels and is extruded by the plasma membrane calcium ATPase (PMCA)2 isoform of the PMCA, mutations in which cause hearing loss. To assess how pump expression matches the demands of Ca(2+) homeostasis, the distribution of PMCA2 at different cochlear locations during development was quantified using immunofluorescence and post-embedding immunogold labeling. The PMCA2 isoform was confined to stereociliary bundles, first appearing at the base of the cochlea around post-natal day (P)0 followed by the middle and then the apex by P3, and was unchanged after P8. The developmental appearance matched the maturation of the MT channels in rat OHCs. High-resolution immunogold labeling in adult rats showed that PMCA2 was distributed along the membranes of all three rows of OHC stereocilia at similar densities and at about a quarter of the density in inner hair cell stereocilia. The difference between OHCs and inner hair cells was similar to the ratio of their MT channel resting open probabilities. Gold particle counts revealed no difference in PMCA2 density between low- and high-frequency OHC bundles despite larger MT currents in high-frequency OHCs. The PMCA2 density in OHC stereocilia was determined in low- and high-frequency regions from calibration of immunogold particle counts as 2200/μm(2) from which an extrusion rate of ∼200 ions/s per pump was inferred. The limited ability of PMCA2 to extrude the Ca(2+) load through MT channels may constitute a major cause of OHC vulnerability and high-frequency hearing loss.
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Affiliation(s)
- Qingguo Chen
- Department of Otolaryngology - Head and Neck Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Kennedy HJ. New developments in understanding the mechanisms and function of spontaneous electrical activity in the developing mammalian auditory system. J Assoc Res Otolaryngol 2012; 13:437-45. [PMID: 22526733 DOI: 10.1007/s10162-012-0325-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 03/25/2012] [Indexed: 01/12/2023] Open
Abstract
In the mature mammalian auditory system, inner hair cells are responsible for converting sound-evoked vibrations into graded electrical responses, resulting in release of neurotransmitter and neuronal transmission via the VIIIth cranial nerve to auditory centres in the central nervous system. Before the cochlea can reliably respond to sound, inner hair cells are not merely immature quiescent pre-hearing cells, but instead are capable of generating 'spontaneous' calcium-based action potentials. The resulting calcium signal promotes transmitter release that drives action potential firing in developing spiral ganglion neurones. These early signalling events that occur before sound-evoked activity are thought to be important in guiding and refining the initial phases of development of the auditory circuits. This review will summarise our current knowledge of the mechanisms that underlie spontaneous action potentials in developing inner hair cells and how these events are triggered and regulated.
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Affiliation(s)
- Helen J Kennedy
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK.
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Fang Q, Giordimaina AM, Dolan DF, Camper SA, Mustapha M. Genetic background of Prop1(df) mutants provides remarkable protection against hypothyroidism-induced hearing impairment. J Assoc Res Otolaryngol 2011; 13:173-184. [PMID: 22143287 PMCID: PMC3298611 DOI: 10.1007/s10162-011-0302-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 11/03/2011] [Indexed: 12/30/2022] Open
Abstract
Hypothyroidism is a cause of genetic and environmentally induced deafness. The sensitivity of cochlear development and function to thyroid hormone (TH) mandates understanding TH action in this sensory organ. Prop1(df) and Pou1f1(dw) mutant mice carry mutations in different pituitary transcription factors, each resulting in pituitary thyrotropin deficiency. Despite the same lack of detectable serum TH, these mutants have very different hearing abilities: Prop1(df) mutants are mildly affected, while Pou1f1(dw) mutants are completely deaf. Genetic studies show that this difference is attributable to the genetic backgrounds. Using embryo transfer, we discovered that factors intrinsic to the fetus are the major contributor to this difference, not maternal effects. We analyzed Prop1(df) mutants to identify processes in cochlear development that are disrupted in other hypothyroid animal models but protected in Prop1(df) mutants by the genetic background. The development of outer hair cell (OHC) function is delayed, but Prestin and KCNQ4 immunostaining appear normal in mature Prop1(df) mutants. The endocochlear potential and KCNJ10 immunostaining in the stria vascularis are indistinguishable from wild type, and no differences in neurofilament or synaptophysin staining are evident in Prop1(df) mutants. The synaptic vesicle protein otoferlin normally shifts expression from OHC to IHC as temporary afferent fibers beneath the OHC regress postnatally. Prop1(df) mutants exhibit persistent, abnormal expression of otoferlin in apical OHC, suggesting delayed maturation of synaptic function. Thus, the genetic background of Prop1(df) mutants is remarkably protective for most functions affected in other hypothyroid mice. The Prop1(df) mutant is an attractive model for identifying the genes that protect against deafness.
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Affiliation(s)
- Qing Fang
- Department of Human Genetics, University of Michigan, 4945 Buhl, 1241 E Catherine St., Ann Arbor, MI, 48109-5618, USA
| | - Alicia M Giordimaina
- Health Behavior & Health Education Department, School of Public Health, University of Michigan, Ann Arbor, MI, 48109, USA
| | - David F Dolan
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Sally A Camper
- Department of Human Genetics, University of Michigan, 4945 Buhl, 1241 E Catherine St., Ann Arbor, MI, 48109-5618, USA.
| | - Mirna Mustapha
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, CA, 94305, USA
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Dysferlin forms a dimer mediated by the C2 domains and the transmembrane domain in vitro and in living cells. PLoS One 2011; 6:e27884. [PMID: 22110769 PMCID: PMC3215728 DOI: 10.1371/journal.pone.0027884] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 10/27/2011] [Indexed: 11/19/2022] Open
Abstract
Dysferlin was previously identified as a key player in muscle membrane repair and its deficiency leads to the development of muscular dystrophy and cardiomyopathy. However, little is known about the oligomerization of this protein in the plasma membrane. Here we report for the first time that dysferlin forms a dimer in vitro and in living adult skeletal muscle fibers isolated from mice. Endogenous dysferlin from rabbit skeletal muscle exists primarily as a ∼460 kDa species in detergent-solubilized muscle homogenate, as shown by sucrose gradient fractionation, gel filtration and cross-linking assays. Fluorescent protein (YFP) labeled human dysferlin forms a dimer in vitro, as demonstrated by fluorescence correlation spectroscopy (FCS) and photon counting histogram (PCH) analyses. Dysferlin also dimerizes in living cells, as probed by fluorescence resonance energy transfer (FRET). Domain mapping FRET experiments showed that dysferlin dimerization is mediated by its transmembrane domain and by multiple C2 domains. However, C2A did not significantly contribute to dimerization; notably, this is the only C2 domain in dysferlin known to engage in a Ca-dependent interaction with cell membranes. Taken together, the data suggest that Ca-insensitive C2 domains mediate high affinity self-association of dysferlin in a parallel homodimer, leaving the Ca-sensitive C2A domain free to interact with membranes.
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Levic S, Bouleau Y, Dulon D. Developmental acquisition of a rapid calcium-regulated vesicle supply allows sustained high rates of exocytosis in auditory hair cells. PLoS One 2011; 6:e25714. [PMID: 21998683 PMCID: PMC3188563 DOI: 10.1371/journal.pone.0025714] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 09/08/2011] [Indexed: 11/19/2022] Open
Abstract
Auditory hair cells (HCs) have the remarkable property to indefinitely sustain high rates of synaptic vesicle release during ongoing sound stimulation. The mechanisms of vesicle supply that allow such indefatigable exocytosis at the ribbon active zone remain largely unknown. To address this issue, we characterized the kinetics of vesicle recruitment and release in developing chick auditory HCs. Experiments were done using the intact chick basilar papilla from E10 (embryonic day 10) to P2 (two days post-hatch) by monitoring changes in membrane capacitance and Ca(2+) currents during various voltage stimulations. Compared to immature pre-hearing HCs (E10-E12), mature post-hearing HCs (E18-P2) can steadily mobilize a larger readily releasable pool (RRP) of vesicles with faster kinetics and higher Ca(2+) efficiency. As assessed by varying the inter-pulse interval of a 100 ms paired-pulse depolarization protocol, the kinetics of RRP replenishment were found much faster in mature HCs. Unlike mature HCs, exocytosis in immature HCs showed large depression during repetitive stimulations. Remarkably, when the intracellular concentration of EGTA was raised from 0.5 to 2 mM, the paired-pulse depression level remained unchanged in immature HCs but was drastically increased in mature HCs, indicating that the Ca(2+) sensitivity of the vesicle replenishment process increases during maturation. Concomitantly, the immunoreactivity of the calcium sensor otoferlin and the number of ribbons at the HC plasma membrane largely increased, reaching a maximum level at E18-P2. Our results suggest that the efficient Ca(2+)-dependent vesicle release and supply in mature HCs essentially rely on the concomitant engagement of synaptic ribbons and otoferlin at the plasma membrane.
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Affiliation(s)
- Snezana Levic
- Equipe Neurophysiologie de la Synapse Auditive, Unité Mixte de Recherche, Inserm U587 et Université Victor Segalen, Institut des Neurosciences de Bordeaux, Centre Hospitalier Universitaire Pellegrin, Bordeaux, France
- * E-mail: (SL) (SL); (DD) (DD)
| | - Yohan Bouleau
- Equipe Neurophysiologie de la Synapse Auditive, Unité Mixte de Recherche, Inserm U587 et Université Victor Segalen, Institut des Neurosciences de Bordeaux, Centre Hospitalier Universitaire Pellegrin, Bordeaux, France
| | - Didier Dulon
- Equipe Neurophysiologie de la Synapse Auditive, Unité Mixte de Recherche, Inserm U587 et Université Victor Segalen, Institut des Neurosciences de Bordeaux, Centre Hospitalier Universitaire Pellegrin, Bordeaux, France
- * E-mail: (SL) (SL); (DD) (DD)
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Jian W, Ying-ying F, Shu-juan W, Peng-Fei L, Jin-ling W, Jian-hua Q. Variants of OTOF and PJVK genes in Chinese patients with auditory neuropathy spectrum disorder. PLoS One 2011; 6:e24000. [PMID: 21935370 PMCID: PMC3174136 DOI: 10.1371/journal.pone.0024000] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 07/27/2011] [Indexed: 12/21/2022] Open
Abstract
Background Mutations in OTOF and PJVK genes cause DFNB9 and DFNB59 types of hearing loss, respectively. The patients carrying pathogenic mutations in either of these genes may show the typical phenotype of auditory neuropathy spectrum disorder (ANSD). The aim of the present study was to identify OTOF and PJVK mutations in sporadic ANSD patients. Methods and Findings A total of 76 unrelated Chinese non-syndromic ANSD patients were sequenced on the gene OTOF and PJVK exon by exon. Variants were valued in 105 controls with normal hearing to verify the carrying rate. We identified one pathogenic mutation (c.1194T>A) and three novel, possibly pathogenic, variants (c.3570+2T>C, c.4023+1 G>A, and c.1102G>A) in the OTOF gene, and one novel, possibly pathogenic, variant (c.548G>A) in PJVK. Moreover, we found three novel missense mutations within the exons of OTOF. Conclusions As we identified 4 and 1 possible pathogenic variants of the OTOF gene and the PJVK gene, respectively, we believe that screening in these genes are important in sporadic ANSD patients. The pathogenicity of these novel mutations needs further study because of their single heterozygous nature. Knowledge on the mutation spectra of these genes in Chinese would be beneficial in understanding the genetic character of this worldwide disease.
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Affiliation(s)
- Wang Jian
- Deafness Gene Diagnosis, PLA Otolaryngology-Head and Neck Surgery Center, Xijing Hospital, Fourth Military Medical University, Xi'an, Shannxi, China
| | - Fan Ying-ying
- Department of Anesthesiology, Stomatological College, Fourth Military Medical University, Xi'an, Shannxi, China
| | - Wang Shu-juan
- Deafness Gene Diagnosis, PLA Otolaryngology-Head and Neck Surgery Center, Xijing Hospital, Fourth Military Medical University, Xi'an, Shannxi, China
| | - Liang Peng-Fei
- Deafness Gene Diagnosis, PLA Otolaryngology-Head and Neck Surgery Center, Xijing Hospital, Fourth Military Medical University, Xi'an, Shannxi, China
| | - Wang Jin-ling
- PLA Otolaryngology-Head and Neck Surgery Center, Xijing Hospital, Fourth Military Medical University, Xi'an, Shannxi, China
| | - Qiu Jian-hua
- Deafness Gene Diagnosis, PLA Otolaryngology-Head and Neck Surgery Center, Xijing Hospital, Fourth Military Medical University, Xi'an, Shannxi, China
- PLA Otolaryngology-Head and Neck Surgery Center, Xijing Hospital, Fourth Military Medical University, Xi'an, Shannxi, China
- * E-mail:
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Zampini V, Rüttiger L, Johnson SL, Franz C, Furness DN, Waldhaus J, Xiong H, Hackney CM, Holley MC, Offenhauser N, Di Fiore PP, Knipper M, Masetto S, Marcotti W. Eps8 regulates hair bundle length and functional maturation of mammalian auditory hair cells. PLoS Biol 2011; 9:e1001048. [PMID: 21526224 PMCID: PMC3079587 DOI: 10.1371/journal.pbio.1001048] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 03/09/2011] [Indexed: 12/20/2022] Open
Abstract
Hair cells of the mammalian cochlea are specialized for the dynamic coding of sound stimuli. The transduction of sound waves into electrical signals depends upon mechanosensitive hair bundles that project from the cell's apical surface. Each stereocilium within a hair bundle is composed of uniformly polarized and tightly packed actin filaments. Several stereociliary proteins have been shown to be associated with hair bundle development and function and are known to cause deafness in mice and humans when mutated. The growth of the stereociliar actin core is dynamically regulated at the actin filament barbed ends in the stereociliary tip. We show that Eps8, a protein with actin binding, bundling, and barbed-end capping activities in other systems, is a novel component of the hair bundle. Eps8 is localized predominantly at the tip of the stereocilia and is essential for their normal elongation and function. Moreover, we have found that Eps8 knockout mice are profoundly deaf and that IHCs, but not OHCs, fail to mature into fully functional sensory receptors. We propose that Eps8 directly regulates stereocilia growth in hair cells and also plays a crucial role in the physiological maturation of mammalian cochlear IHCs. Together, our results indicate that Eps8 is critical in coordinating the development and functionality of mammalian auditory hair cells.
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Affiliation(s)
- Valeria Zampini
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- Department of Physiology, University of Pavia, Pavia, Italy
| | - Lukas Rüttiger
- Department of Otolaryngology, THR, University of Tübingen, Tübingen, Germany
| | - Stuart L. Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Christoph Franz
- Department of Otolaryngology, THR, University of Tübingen, Tübingen, Germany
| | - David N. Furness
- Institute for Science and Technology in Medicine, Keele University, Keele, United Kingdom
| | - Jörg Waldhaus
- Department of Otolaryngology, THR, University of Tübingen, Tübingen, Germany
| | - Hao Xiong
- Department of Otolaryngology, THR, University of Tübingen, Tübingen, Germany
- Department of Otolaryngology-Head & Neck Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China
| | - Carole M. Hackney
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Matthew C. Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Nina Offenhauser
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milan, Italy
| | - Pier Paolo Di Fiore
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milan, Italy
- Istituto Europeo di Oncologia, Milan, Italy
- Dipartimento di Medicina, Chirurgia e Odontoiatria, Università degli Studi di Milano, Milan, Italy
| | - Marlies Knipper
- Department of Otolaryngology, THR, University of Tübingen, Tübingen, Germany
| | - Sergio Masetto
- Department of Physiology, University of Pavia, Pavia, Italy
- * E-mail: (WM); (SM)
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- * E-mail: (WM); (SM)
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miR-96 regulates the progression of differentiation in mammalian cochlear inner and outer hair cells. Proc Natl Acad Sci U S A 2011; 108:2355-60. [PMID: 21245307 DOI: 10.1073/pnas.1016646108] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
MicroRNAs (miRNAs) are small noncoding RNAs able to regulate a broad range of protein-coding genes involved in many biological processes. miR-96 is a sensory organ-specific miRNA expressed in the mammalian cochlea during development. Mutations in miR-96 cause nonsyndromic progressive hearing loss in humans and mice. The mouse mutant diminuendo has a single base change in the seed region of the Mir96 gene leading to widespread changes in the expression of many genes. We have used this mutant to explore the role of miR-96 in the maturation of the auditory organ. We found that the physiological development of mutant sensory hair cells is arrested at around the day of birth, before their biophysical differentiation into inner and outer hair cells. Moreover, maturation of the hair cell stereocilia bundle and remodelling of auditory nerve connections within the cochlea fail to occur in miR-96 mutants. We conclude that miR-96 regulates the progression of the physiological and morphological differentiation of cochlear hair cells and, as such, coordinates one of the most distinctive functional refinements of the mammalian auditory system.
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Heil P, Neubauer H. Summing Across Different Active Zones can Explain the Quasi-Linear Ca-Dependencies of Exocytosis by Receptor Cells. Front Synaptic Neurosci 2010; 2:148. [PMID: 21423534 PMCID: PMC3059696 DOI: 10.3389/fnsyn.2010.00148] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 11/03/2010] [Indexed: 12/15/2022] Open
Abstract
Several recent studies of mature auditory and vestibular hair cells (HCs), and of visual and olfactory receptor cells, have observed nearly linear dependencies of the rate of neurotransmitter release events, or related measures, on the magnitude of Ca2+-entry into the cell. These relationships contrast with the highly supralinear, third to fourth power, Ca2+-dependencies observed in most preparations, from neuromuscular junctions to central synapses, and also in HCs from immature and various mutant animals. They also contrast with the intrinsic, biochemical, Ca2+-cooperativity of the ubiquitous Ca2+-sensors involved in fast exocytosis (synaptotagmins I and II). Here, we propose that the quasi-linear dependencies result from measuring the sum of several supralinear, but saturating, dependencies with different sensitivities at individual active zones of the same cell. We show that published experimental data can be accurately accounted for by this summation model, without the need to assume altered Ca2+-cooperativity or nanodomain control of release. We provide support for the proposal that the best power is 3, and we discuss the large body of evidence for our summation model. Overall, our idea provides a parsimonious and attractive reconciliation of the seemingly discrepant experimental findings in different preparations.
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Affiliation(s)
- Peter Heil
- Auditory Learning and Speech, Leibniz Institute for Neurobiology Magdeburg, Germany
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