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Hong H, Koo EJ, Park Y, Song G, Joo SY, Kim JA, Gee HY, Jung J, Park K, Han GC, Choie JY, Kim SH. Vestibular hair cells are more prone to damage by excessive acceleration insult in the mouse with KCNQ4 dysfunction. Sci Rep 2024; 14:15260. [PMID: 38956136 PMCID: PMC11219875 DOI: 10.1038/s41598-024-66115-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 06/27/2024] [Indexed: 07/04/2024] Open
Abstract
KCNQ4 is a voltage-gated K+ channel was reported to distribute over the basolateral surface of type 1 vestibular hair cell and/or inner surface of calyx and heminode of the vestibular nerve connected to the type 1 vestibular hair cells of the inner ear. However, the precise localization of KCNQ4 is still controversial and little is known about the vestibular phenotypes caused by KCNQ4 dysfunction or the specific role of KCNQ4 in the vestibular organs. To investigate the role of KCNQ4 in the vestibular organ, 6-g hypergravity stimulation for 24 h, which represents excessive mechanical stimulation of the sensory epithelium, was applied to p.W277S Kcnq4 transgenic mice. KCNQ4 was detected on the inner surface of calyx of the vestibular afferent in transmission electron microscope images with immunogold labelling. Vestibular function decrease was more severe in the Kcnq4p.W277S/p.W277S mice than in the Kcnq4+/+ and Kcnq4+/p.W277S mice after the stimulation. The vestibular function loss was resulted from the loss of type 1 vestibular hair cells, which was possibly caused by increased depolarization duration. Retigabine, a KCNQ activator, prevented hypergravity-induced vestibular dysfunction and hair cell loss. Patients with KCNQ4 mutations also showed abnormal clinical vestibular function tests. These findings suggest that KCNQ4 plays an essential role in calyx and afferent of type 1 vestibular hair cell preserving vestibular function against excessive mechanical stimulation.
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Affiliation(s)
- Hansol Hong
- Department of Otorhinolaryngology, Won-Sang Lee Institute for Hearing Loss, Yonsei University College of Medicine and Graduate School of Medicine, Seoul, Republic of Korea
| | - Eun Ji Koo
- Department of Otorhinolaryngology, Gachon University College of Medicine, Incheon, Republic of Korea
| | - Yesai Park
- Department of Otorhinolaryngology, Incheon St. Mary's Hospital, Catholic University College of Medicine, Incheon, Republic of Korea
| | - Gabae Song
- Department of Otorhinolaryngology, Won-Sang Lee Institute for Hearing Loss, Yonsei University College of Medicine and Graduate School of Medicine, Seoul, Republic of Korea
| | - Sun Young Joo
- Department of Pharmacology, Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jung Ah Kim
- Department of Pharmacology, Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Heon Yung Gee
- Department of Pharmacology, Graduate School of Medical Science, Brain Korea 21 Project, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Jinsei Jung
- Department of Otorhinolaryngology, Won-Sang Lee Institute for Hearing Loss, Yonsei University College of Medicine and Graduate School of Medicine, Seoul, Republic of Korea
| | - Kangyoon Park
- Department of Otorhinolaryngology, Won-Sang Lee Institute for Hearing Loss, Yonsei University College of Medicine and Graduate School of Medicine, Seoul, Republic of Korea
| | - Gyu Cheol Han
- Department of Otorhinolaryngology, Gachon University College of Medicine, Incheon, Republic of Korea.
| | - Jae Young Choie
- Department of Otorhinolaryngology, Won-Sang Lee Institute for Hearing Loss, Yonsei University College of Medicine and Graduate School of Medicine, Seoul, Republic of Korea.
| | - Sung Huhn Kim
- Department of Otorhinolaryngology, Won-Sang Lee Institute for Hearing Loss, Yonsei University College of Medicine and Graduate School of Medicine, Seoul, Republic of Korea.
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Singh J, Randle MR, Walters BJ, Cox BC. The transcription factor Pou4f3 is essential for the survival of postnatal and adult mouse cochlear hair cells and normal hearing. Front Cell Neurosci 2024; 18:1369282. [PMID: 38566840 PMCID: PMC10985149 DOI: 10.3389/fncel.2024.1369282] [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: 01/11/2024] [Accepted: 02/26/2024] [Indexed: 04/04/2024] Open
Abstract
Introduction Hair cells (HCs) of the cochlea are responsible for sound transduction and hearing perception in mammals. Genetic mutations in the transcription factor Pou4f3 cause non-syndromic autosomal dominant hearing loss in humans (DFNA15) which varies in the age of onset depending on the individual mutation. Mouse models with germline deletion or mutations in Pou4f3 have previously demonstrated its critical role in the maturation and survival of cochlear HCs during embryonic development. However, the role of Pou4f3 in auditory function and in the survival or maintenance of cochlear HCs after birth and during adulthood has not been studied. Methods Therefore, using the inducible CreER-loxP system, we deleted Pou4f3 from mouse cochlear HCs at different postnatal ages, relevant to specific stages of HC maturation and hearing function. Results and discussion Elevated auditory brainstem response thresholds and significant HC loss were detected in mice with Pou4f3 deletion compared to their control littermates, regardless of the age when Pou4f3 was deleted. However, HC loss occurred more rapidly when Pou4f3 was deleted from immature HCs. Additionally, HC loss caused by Pou4f3 deletion did not affect the number of cochlear supporting cells, but caused a delayed loss of spiral ganglion neurons at 4 months after the deletion. In conclusion, Pou4f3 is necessary for the survival of cochlear HCs and normal hearing at all postnatal ages regardless of their maturation state. Our data also suggest that Pou4f3 indirectly regulates the survival of spiral ganglion neurons.
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Affiliation(s)
- Jarnail Singh
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Michelle R. Randle
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Bradley J. Walters
- Department of Otolaryngology-Head and Neck Surgery, University of Mississippi Medical Center, Jackson, MS, United States
| | - Brandon C. Cox
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
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3
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Ramírez A, Monjaraz E, Manjarrez E, Moyaho A, Cebada J, Flores A. Pharmacological characterization and differential expression of NMDA receptor subunits in the chicken vestibular system during development. Synapse 2023; 77:e22252. [PMID: 36099479 DOI: 10.1002/syn.22252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 08/31/2022] [Accepted: 09/04/2022] [Indexed: 01/29/2023]
Abstract
Previous studies demonstrated that in vitro preparations of the isolated vestibular system of diverse animal species still exhibit stable resting electrical activity and mechanically evoked synaptic transmission between hair cells and primary afferent endings. However, there are no reports related to their neurodevelopment. Therefore, this research aimed to examine whether NMDA receptors mediate these electrical signals in an isolated preparation of the chicken vestibular system at three developmental stages, E15, E18, and E21. We found that the spontaneous and mechanically evoked discharges from primary afferents of the posterior semicircular canal were modulated by agonists NMDA and glycine, but not by the agonist d-serine applied near the synapses. Moreover, the individually applied by bath perfusion of three NMDA receptor antagonists (MK-801, ifenprodil, and 2-naphthoic acid) or high Mg2+ decreased the resting discharge rate, the NMDA response, and the discharge rate of mechanically evoked activity from these primary afferents. Furthermore, we found that the vestibular ganglion shows a stage-dependent increase in the expression of NMDA receptor subunits GluN1, GluN2 (A-C), and GluN3 (A-B), being greater at E21, except for GluN2D, which was inversely related to the developmental stage. However, in the crista ampullaris, the expression pattern remained constant throughout development. This could suggest the possible existence of presynaptic NMDA receptors. Our results highlight that although the NMDA receptors are functionally active at the early embryonic stages of the vestibular system, NMDA and glycine reach their mature functionality to increase NMDA responses close to hatching (E21).
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Affiliation(s)
- Ana Ramírez
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, México.,Facultad de Medicina, Benemérita Universidad Autónoma de Puebla, Puebla, México
| | - Eduardo Monjaraz
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, México
| | - Elías Manjarrez
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, México
| | - Alejandro Moyaho
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, México
| | - Jorge Cebada
- Facultad de Medicina, Benemérita Universidad Autónoma de Puebla, Puebla, México
| | - Amira Flores
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, México
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4
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Zhu S, Chen Z, Wang H, McDermott BM. Tmc Reliance Is Biased by the Hair Cell Subtype and Position Within the Ear. Front Cell Dev Biol 2021; 8:570486. [PMID: 33490059 PMCID: PMC7817542 DOI: 10.3389/fcell.2020.570486] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 10/21/2020] [Indexed: 12/04/2022] Open
Abstract
Hair cells are heterogenous, enabling varied roles in sensory systems. An emerging hypothesis is that the transmembrane channel-like (Tmc) proteins of the hair cell’s mechanotransduction apparatus vary within and between organs to permit encoding of different mechanical stimuli. Five anatomical variables that may coincide with different Tmc use by a hair cell within the ear are the containing organ, cell morphology, cell position within an organ, axis of best sensitivity for the cell, and the hair bundle’s orientation within this axis. Here, we test this hypothesis in the organs of the zebrafish ear using a suite of genetic mutations. Transgenesis and quantitative measurements demonstrate two morphologically distinct hair cell types in the central thickness of a vestibular organ, the lateral crista: short and tall. In contrast to what has been observed, we find that tall hair cells that lack Tmc1 generally have substantial reductions in mechanosensitivity. In short hair cells that lack Tmc2 isoforms, mechanotransduction is largely abated. However, hair cell Tmc dependencies are not absolute, and an exceptional class of short hair cell that depends on Tmc1 is present, termed a short hair cell erratic. To further test anatomical variables that may influence Tmc use, we map Tmc1 function in the saccule of mutant larvae that depend just on this Tmc protein to hear. We demonstrate that hair cells that use Tmc1 are found in the posterior region of the saccule, within a single axis of best sensitivity, and hair bundles with opposite orientations retain function. Overall, we determine that Tmc reliance in the ear is dependent on the organ, subtype of hair cell, position within the ear, and axis of best sensitivity.
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Affiliation(s)
- Shaoyuan Zhu
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Case Western Reserve University, Cleveland, OH, United States.,Department of Biology, Case Western Reserve University, Cleveland, OH, United States
| | - Zongwei Chen
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Case Western Reserve University, Cleveland, OH, United States.,Department of Biology, Case Western Reserve University, Cleveland, OH, United States
| | - Haoming Wang
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Case Western Reserve University, Cleveland, OH, United States.,Department of Biology, Case Western Reserve University, Cleveland, OH, United States
| | - Brian M McDermott
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Case Western Reserve University, Cleveland, OH, United States.,Department of Biology, Case Western Reserve University, Cleveland, OH, United States.,Department of Genetics and Genome Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH, United States.,Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, OH, United States
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5
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Lu J, Hu L, Ye B, Hu H, Tao Y, Shu Y, Hao Chiang, Borse V, Xiang M, Wu H, Edge ASB, Shi F. Increased Type I and Decreased Type II Hair Cells after Deletion of Sox2 in the Developing Mouse Utricle. Neuroscience 2019; 422:146-160. [PMID: 31678344 PMCID: PMC10858341 DOI: 10.1016/j.neuroscience.2019.09.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 09/21/2019] [Accepted: 09/23/2019] [Indexed: 12/13/2022]
Abstract
The vestibular system of the inner ear contains Type I and Type II hair cells (HCs) generated from sensory progenitor cells; however, little is known about how the HC subtypes are formed. Sox2 (encoding SRY-box 2) is expressed in Type II, but not in Type I, HCs. The present study aimed to investigate the role of SOX2 in cell fate determination in Type I vs. Type II HCs. First, we confirmed that Type I HCs developed from Sox2-expressing cells through lineage tracing of Sox2-positive cells using a CAG-tdTomato reporter mouse crossed with a Sox2-CreER mouse. Then, Sox2 loss of function was induced in HCs, using Sox2flox transgenic mice crossed with a Gfi1-Cre driver mouse. Knockout of Sox2 in HCs increased the number of Type I HCs and decreased the number of Type II HCs, while the total number of HCs and Sox2-positive supporting cells did not change. In addition, the effect of Sox2-knockout persisted into adulthood, resulting in an increased number of Type I HCs. These results demonstrate that SOX2 plays a critical role in the determination of Type II vs. Type I HC fate. The results suggested that Sox2 is a potential target for generating Type I HCs, which may be important for regenerative strategies for balance disorders.
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Affiliation(s)
- Jingrong Lu
- Department of Otolaryngology-Head & Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, China
| | - Lingxiang Hu
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, China; Department of Otolaryngology Head & Neck Surgery, Shanghai 9th People's Hospital/Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China
| | - Bin Ye
- Department of Otolaryngology-Head & Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, China
| | - Haixia Hu
- Department of Otolaryngology-Head & Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, China
| | - Yong Tao
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, China; Department of Otolaryngology Head & Neck Surgery, Shanghai 9th People's Hospital/Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China
| | - Yilai Shu
- ENT Institute and Otorhinolaryngology Department, Affiliated Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China; Key Laboratory of Hearing Medicine of National Health and Family Planning Commission (NHFPC), Shanghai, China
| | - Hao Chiang
- Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA; Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, MA 02114, USA
| | - Vikrant Borse
- Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA; Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, MA 02114, USA
| | - Mingliang Xiang
- Department of Otolaryngology-Head & Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, China
| | - Hao Wu
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, China; Department of Otolaryngology Head & Neck Surgery, Shanghai 9th People's Hospital/Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
| | - Albert S B Edge
- Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA; Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, MA 02114, USA
| | - Fuxin Shi
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China; Decibel Therapeutics, Boston, MA 02215, USA.
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6
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Perny M, Solyga M, Grandgirard D, Roccio M, Leib SL, Senn P. Streptococcus pneumoniae-induced ototoxicity in organ of Corti explant cultures. Hear Res 2017; 350:100-109. [PMID: 28460251 DOI: 10.1016/j.heares.2017.04.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 04/11/2017] [Accepted: 04/23/2017] [Indexed: 12/20/2022]
Abstract
Hearing loss remains the most common long-term complication of pneumococcal meningitis (PM) reported in up to 30% of survivors. Streptococcus pneumoniae have been shown to possess different ototoxic properties. Here we present a novel ex vivo experimental setup to examine in detail the pattern of hair cell loss upon exposure to different S. pneumoniae strains, therefore recapitulating pathogen derived aspects of PM-induced hearing loss. Our results show a higher susceptibility towards S. pneumoniae-induced cochlear damage for outer hair cells (OHC) compared to inner hair cells (IHC), which is consistent with in vivo data. S. pneumoniae-induced hair cell loss was both time and dose-dependent. Moreover, we have found significant differences in the level of cell damage between tissue from the basal and the apical turns. This shows that the higher vulnerability of hair cells located at high frequency regions observed in vivo cannot be explained solely by the spatial organisation and bacterial infiltration from the basal portion of the cochlea. Using a wild type D39 strain and a mutant defective for the pneumolysin (PLY) gene, we also have shown that the toxin PLY is an important factor involved in ototoxic damages. The obtained results indicate that PLY can cause both IHC and OHC loss. Finally, we are reporting here for the first time a higher vulnerability of HC located at the basal and middle cochlear region to pneumolysin-induced damage. The detailed description of the susceptibility of hair cells to Streptococcus pneumoniae provided in this report can in the future determine the choice and the development of novel otoprotective therapies during pneumococcal meningitis.
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Affiliation(s)
- Michael Perny
- Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Switzerland; Inner Ear Research Laboratory, Department of Otorhinolaryngology, Head& Neck Surgery, Inselspital Bern and Department of Clinical Research, University of Bern, Switzerland; Cluster for Regenerative Neuroscience, Department of Clinical Research, University of Bern, Switzerland
| | - Magdalena Solyga
- Inner Ear Research Laboratory, Department of Otorhinolaryngology, Head& Neck Surgery, Inselspital Bern and Department of Clinical Research, University of Bern, Switzerland; Cluster for Regenerative Neuroscience, Department of Clinical Research, University of Bern, Switzerland
| | - Denis Grandgirard
- Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Switzerland; Cluster for Regenerative Neuroscience, Department of Clinical Research, University of Bern, Switzerland
| | - Marta Roccio
- Inner Ear Research Laboratory, Department of Otorhinolaryngology, Head& Neck Surgery, Inselspital Bern and Department of Clinical Research, University of Bern, Switzerland; Cluster for Regenerative Neuroscience, Department of Clinical Research, University of Bern, Switzerland
| | - Stephen L Leib
- Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern, Switzerland; Cluster for Regenerative Neuroscience, Department of Clinical Research, University of Bern, Switzerland.
| | - Pascal Senn
- Inner Ear Research Laboratory, Department of Otorhinolaryngology, Head& Neck Surgery, Inselspital Bern and Department of Clinical Research, University of Bern, Switzerland; Department of Otorhinolaryngology, Head & Neck Surgery, University Hospital Geneva (HUG), Genève, Switzerland; Cluster for Regenerative Neuroscience, Department of Clinical Research, University of Bern, Switzerland.
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7
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McLean WJ, McLean DT, Eatock RA, Edge ASB. Distinct capacity for differentiation to inner ear cell types by progenitor cells of the cochlea and vestibular organs. Development 2016; 143:4381-4393. [PMID: 27789624 DOI: 10.1242/dev.139840] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 10/11/2016] [Indexed: 01/16/2023]
Abstract
Disorders of hearing and balance are most commonly associated with damage to cochlear and vestibular hair cells or neurons. Although these cells are not capable of spontaneous regeneration, progenitor cells in the hearing and balance organs of the neonatal mammalian inner ear have the capacity to generate new hair cells after damage. To investigate whether these cells are restricted in their differentiation capacity, we assessed the phenotypes of differentiated progenitor cells isolated from three compartments of the mouse inner ear - the vestibular and cochlear sensory epithelia and the spiral ganglion - by measuring electrophysiological properties and gene expression. Lgr5+ progenitor cells from the sensory epithelia gave rise to hair cell-like cells, but not neurons or glial cells. Newly created hair cell-like cells had hair bundle proteins, synaptic proteins and membrane proteins characteristic of the compartment of origin. PLP1+ glial cells from the spiral ganglion were identified as neural progenitors, which gave rise to neurons, astrocytes and oligodendrocytes, but not hair cells. Thus, distinct progenitor populations from the neonatal inner ear differentiate to cell types associated with their organ of origin.
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Affiliation(s)
- Will J McLean
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA.,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.,Program in Speech and Hearing Bioscience and Technology, Division of Health Sciences and Technology, Harvard & MIT, Cambridge, MA 02139, USA
| | - Dalton T McLean
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA.,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
| | - Ruth Anne Eatock
- Department of Neurobiology, University of Chicago, Chicago, IL 60637, USA
| | - Albert S B Edge
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA .,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.,Program in Speech and Hearing Bioscience and Technology, Division of Health Sciences and Technology, Harvard & MIT, Cambridge, MA 02139, USA.,Harvard Stem Cell Institute, Cambridge, MA 02138, USA
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8
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Channeling your inner ear potassium: K+ channels in vestibular hair cells. Hear Res 2016; 338:40-51. [DOI: 10.1016/j.heares.2016.01.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 01/22/2016] [Accepted: 01/25/2016] [Indexed: 01/05/2023]
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9
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Yu YF, Wu WY, Xiao GS, Ling HY, Pan C. Protection of the cochlear hair cells in adult C57BL/6J mice by T-type calcium channel blockers. Exp Ther Med 2016; 11:1039-1044. [PMID: 26998034 DOI: 10.3892/etm.2016.2970] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 10/29/2015] [Indexed: 12/15/2022] Open
Abstract
The aim of the present study was to investigate the protective effect of T-type calcium channel blockers against presbycusis, using a C57BL/6J mice model. The expression of three T-type calcium channel receptor subunits in the cochlea of 6-8-week-old C57BL/6J mice was evaluated using reverse transcription-quantitative polymerase chain reaction. The results confirmed that the three subunits were expressed in the cochlea. In addition, the capacity of T-type calcium channel blockers to protect the cochlear hair cells of 24-26-week-old C57BL/6J mice was investigated in mice treated with mibefradil, benidipine or saline for 4 weeks. Differences in hearing threshold were detected using auditory brainstem recording (ABR), while differences in amplitudes were measured using a distortion product otoacoustic emission (DPOAE) test. The ABR test results showed that the hearing threshold significantly decreased at 24 kHz in the mibefradil-treated and benidipine-treated groups compared with the saline-treated group. The DPOAE amplitudes in the mibefradil-treated group were increased compared with those in the saline-treated group at the F2 frequencies of 11.3 and 13.4 kHz. Furthermore, the DPOAE amplitudes in the benidipine-treated group were increased compared with those in the saline-treated group at an F2 frequency of 13.4 kHz. The loss of outer hair cells (OHCs) was not evident in the mibefradil-treated group; however, the stereocilia of the inner hair cells (IHCs) were disorganised and sparse. In summary, these results indicate that the administration of a T-type calcium channel blocker for four consecutive weeks may improve the hearing at 24 kHz of 24-26-week-old C57BL/6J mice. The function and morphology of the OHCs of the C57BL/6J mice were significantly altered by the administration of a T-type calcium channel blocker; however, the IHCs were unaffected.
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Affiliation(s)
- Ya-Feng Yu
- Department of Otolaryngology, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, P.R. China
| | - Wen-Ying Wu
- Department of Otolaryngology, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, P.R. China
| | - Gen-Sheng Xiao
- Department of Otolaryngology, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, P.R. China
| | - Hong-Yang Ling
- Department of Otolaryngology, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, P.R. China
| | - Chen Pan
- Department of Otolaryngology, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, P.R. China
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10
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Coding of envelopes by correlated but not single-neuron activity requires neural variability. Proc Natl Acad Sci U S A 2015; 112:4791-6. [PMID: 25825717 DOI: 10.1073/pnas.1418224112] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Understanding how the brain processes sensory information is often complicated by the fact that neurons exhibit trial-to-trial variability in their responses to stimuli. Indeed, the role of variability in sensory coding is still highly debated. Here, we examined how variability influences neural responses to naturalistic stimuli consisting of a fast time-varying waveform (i.e., carrier or first order) whose amplitude (i.e., envelope or second order) varies more slowly. Recordings were made from fish electrosensory and monkey vestibular sensory neurons. In both systems, we show that correlated but not single-neuron activity can provide detailed information about second-order stimulus features. Using a simple mathematical model, we made the strong prediction that such correlation-based coding of envelopes requires neural variability. Strikingly, the performance of correlated activity at predicting the envelope was similarly optimally tuned to a nonzero level of variability in both systems, thereby confirming this prediction. Finally, we show that second-order sensory information can only be decoded if one takes into account joint statistics when combining neural activities. Our results thus show that correlated but not single-neural activity can transmit information about the envelope, that such transmission requires neural variability, and that this information can be decoded. We suggest that envelope coding by correlated activity is a general feature of sensory processing that will be found across species and systems.
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11
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Regenerated synapses between postnatal hair cells and auditory neurons. J Assoc Res Otolaryngol 2013; 14:321-9. [PMID: 23423560 DOI: 10.1007/s10162-013-0374-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2012] [Accepted: 01/29/2013] [Indexed: 02/06/2023] Open
Abstract
Regeneration of synaptic connections between hair cells and spiral ganglion neurons would be required to restore hearing after neural loss. Here we demonstrate by immunohistochemistry the appearance of afferent-like cochlear synapses in vitro after co-culture of de-afferented organ of Corti with spiral ganglion neurons from newborn mice. The glutamatergic synaptic complexes at the ribbon synapse of the inner hair cell contain markers for presynaptic ribbons and postsynaptic densities. We found postsynaptic density protein PSD-95 at the contacts between hair cells and spiral ganglion neurons in newly formed synapses in vitro. The postsynaptic proteins were directly facing the CtBP2-positive presynaptic ribbons of the hair cells. BDNF and NT-3 promoted afferent synaptogenesis in vitro. Direct juxtaposition of the postsynaptic densities with the components of the preexisting ribbon synapse indicated that growing fibers recognized components of the presynaptic sites. Initiation of cochlear synaptogenesis appeared to be influenced by glutamate release from the hair cell ribbons at the presynaptic site since the synaptic regeneration was impaired in glutamate vesicular transporter 3 mutant mice. These insights into cochlear synaptogenesis could be relevant to regenerative approaches for neural loss in the cochlea.
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Mann SE, Johnson M, Meredith FL, Rennie KJ. Inhibition of K+ Currents in Type I Vestibular Hair Cells by Gentamicin and Neomycin. ACTA ACUST UNITED AC 2013; 18:317-26. [DOI: 10.1159/000354056] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 06/24/2013] [Indexed: 11/19/2022]
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13
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Travo C, Gaboyard-Niay S, Chabbert C. Plasticity of Scarpa's Ganglion Neurons as a Possible Basis for Functional Restoration within Vestibular Endorgans. Front Neurol 2012; 3:91. [PMID: 22685444 PMCID: PMC3368229 DOI: 10.3389/fneur.2012.00091] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 05/19/2012] [Indexed: 12/21/2022] Open
Abstract
In a previous study, we observed spontaneous restoration of vestibular function in young adult rodents following excitotoxic injury of the neuronal connections within vestibular endorgans. The functional restoration was supported by a repair of synaptic contacts between hair cells and primary vestibular neurons. This process was observed in 2/3 of the animals studied and occurred within 5 days following the synaptic damage. To assess whether repair capacity is a fundamental trait of vestibular endorgans and to decipher the cellular mechanisms supporting such a repair process, we studied the neuronal regeneration and synaptogenesis in co-cultures of vestibular epithelia and Scarpa's ganglion from young and adult rodents. We demonstrate that, under specific culture conditions, primary vestibular neurons from young mice or rats exhibit robust ability to regenerate nervous processes. When co-cultured with vestibular epithelia, primary vestibular neurons were able to establish de novo contacts with hair cells. Under the present paradigm, these contacts displayed morphological features of immature synaptic contacts. Preliminary observations using co-cultures of adult rodents suggest that this reparative capacity remained in older mice although to a lesser extent. Identifying the basic mechanisms underlying the repair process may provide a basis for novel therapeutic strategies to restore mature and functional vestibular synaptic contacts following damage or loss.
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Affiliation(s)
- Cécile Travo
- INSERM U1051, Institute for Neurosciences Montpellier, France
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14
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Functional features of trans-differentiated hair cells mediated by Atoh1 reveals a primordial mechanism. J Neurosci 2012; 32:3712-25. [PMID: 22423092 DOI: 10.1523/jneurosci.6093-11.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Evolution has transformed a simple ear with few vestibular maculae into a complex three-dimensional structure consisting of nine distinct endorgans. It is debatable whether the sensory epithelia underwent progressive segregation or emerged from distinct sensory patches. To address these uncertainties we examined the morphological and functional phenotype of trans-differentiated rat hair cells to reveal their primitive or endorgan-specific origins. Additionally, it is uncertain how Atoh1-mediated trans-differentiated hair cells trigger the processes that establish their neural ranking from the vestibulocochlear ganglia. We have demonstrated that the morphology and functional expression of ionic currents in trans-differentiated hair cells resemble those of "ancestral" hair cells, even at the lesser epithelia ridge aspects of the cochlea. The structures of stereociliary bundles of trans-differentiated hair cells were in keeping with cells in the vestibule. Functionally, the transient expression of Na⁺ and I(h) currents initiates and promotes evoked spikes. Additionally, Ca²⁺ current was expressed and underwent developmental changes. These events correlate well with the innervation of ectopic hair cells. New "born" hair cells at the abneural aspects of the cochlea are innervated by spiral ganglion neurons, presumably under the tropic influence of chemoattractants. The disappearance of inward currents coincides well with the attenuation of evoked electrical activity, remarkably recapitulating the development of hair cells. Ectopic hair cells underwent stepwise changes in the magnitude and kinetics of transducer currents. We propose that Atoh1 mediates trans-differentiation of morphological and functional "ancestral" hair cells that are likely to undergo diversification in an endorgan-specific manner.
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15
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Meredith FL, Li GQ, Rennie KJ. Postnatal expression of an apamin-sensitive k(ca) current in vestibular calyx terminals. J Membr Biol 2011; 244:81-91. [PMID: 22057903 DOI: 10.1007/s00232-011-9400-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 10/15/2011] [Indexed: 11/25/2022]
Abstract
Afferent innervation patterns in the vestibular periphery are complex, and vestibular afferents show a large variation in their regularity of firing. Calyx fibers terminate on type I vestibular hair cells and have firing characteristics distinct from the bouton fibers that innervate type II hair cells. Whole-cell patch clamp was used to investigate ionic currents that could influence firing patterns in calyx terminals. Underlying K(Ca) conductances have been described in vestibular ganglion cells, but their presence in afferent terminals has not been investigated previously. Apamin, a selective blocker of SK-type calcium-activated K(+) channels, was tested on calyx afferent terminals isolated from gerbil semicircular canals during postnatal days 1-50. Lowering extracellular calcium or application of apamin (20-500 nM) reduced slowly activating outward currents in voltage clamp. Apamin also reduced the action potential afterhyperpolarization (AHP) in whole-cell current clamp, but only after the first two postnatal weeks. K(+) channel expression increased during the first postnatal month, and SK channels were found to contribute to the AHP, which may in turn influence discharge regularity in calyx vestibular afferents.
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Affiliation(s)
- Frances L Meredith
- Department of Otolaryngology, University of Colorado at Anschutz Medical Campus, Aurora, CO 80045, USA
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16
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Eatock RA, Songer JE. Vestibular hair cells and afferents: two channels for head motion signals. Annu Rev Neurosci 2011; 34:501-34. [PMID: 21469959 DOI: 10.1146/annurev-neuro-061010-113710] [Citation(s) in RCA: 158] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Vestibular epithelia of the inner ear detect head motions over a wide range of amplitudes and frequencies. In mammals, afferent nerve fibers from central and peripheral zones of vestibular epithelia form distinct populations with different response dynamics and spike timing. Central-zone afferents are large, fast conduits for phasic signals encoded in irregular spike trains. The finer afferents from peripheral zones conduct more slowly and encode more tonic, linear signals in highly regular spike trains. The hair cells are also of two types, I and II, but the two types do not correspond directly to the two afferent populations. Zonal differences in afferent response dynamics may arise at multiple stages, including mechanoelectrical transduction, voltage-gated channels in hair cells and afferents, afferent transmission at calyceal and bouton synapses, and spike generation in regular and irregular afferents. In contrast, zonal differences in spike timing may depend more simply on the selective expression of low-voltage-activated ion channels by irregular afferents.
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Affiliation(s)
- Ruth Anne Eatock
- Department of Otology and Laryngology, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02114, USA.
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17
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Scheffer D, Sage C, Plazas PV, Huang M, Wedemeyer C, Zhang DS, Chen ZY, Elgoyhen AB, Corey DP, Pingault V. The α1 subunit of nicotinic acetylcholine receptors in the inner ear: transcriptional regulation by ATOH1 and co-expression with the γ subunit in hair cells. J Neurochem 2011; 103:2651-64. [PMID: 17961150 DOI: 10.1111/j.1471-4159.2007.04980.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Acetylcholine is a key neurotransmitter of the inner ear efferent system. In this study, we identify two novel nAChR subunits in the inner ear: α1 and γ, encoded by Chrna1 and Chrng, respectively. In situ hybridization shows that the messages of these two subunits are present in vestibular and cochlear hair cells during early development. Chrna1 and Chrng expression begin at embryonic stage E13.5 in the vestibular system and E17.5 in the organ of Corti. Chrna1 message continues through P7, whereas Chrng is undetectable at post-natal stage P6. The α1 and γ subunits are known as muscle-type nAChR subunits and are surprisingly expressed in hair cells which are sensory-neural cells. We also show that ATOH1/MATH1, a transcription factor essential for hair cell development, directly activates CHRNA1 transcription. Electrophoretic mobility-shift assays and supershift assays showed that ATOH1/E47 heterodimers selectively bind on two E boxes located in the proximal promoter of CHRNA1. Thus, Chrna1 could be the first transcriptional target of ATOH1 in the inner ear. Co-expression in Xenopus oocytes of the α1 subunit does not change the electrophysiological properties of the α9α10 receptor. We suggest that hair cells transiently express α1γ-containing nAChRs in addition to α9α10, and that these may have a role during development of the inner ear innervation.
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18
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Abstract
Ca(2+) acts as a fundamental signal transduction element in inner ear, delivering information about sound, acceleration and gravity through a small number of mechanotransduction channels in the hair cell stereocilia and voltage activated Ca(2+) channels at the ribbon synapse, where it drives neurotransmission. The mechanotransduction process relies on the endocochlear potential, an electrical potential difference between endolymph and perilymph, the two fluids bathing respectively the apical and basolateral membrane of the cells in the organ of Corti. In mouse models, deafness and lack or reduction of the endocochlear potential correlate with ablation of connexin (Cx) 26 or 30. These Cxs form heteromeric channels assembled in a network of gap junction plaques connecting the supporting and epithelial cells of the organ of Corti presumably for K(+) recycle and transfer of key metabolites, for example, the Ca(2+) -mobilizing second messenger IP(3) . Ca(2+) signaling in these cells could play a crucial role in regulating Cx expression and function. Another district where Ca(2+) signaling alterations link to hearing loss is hair cell apex, where ablation or missense mutations of the PMCA2 Ca(2+) -pump of the stereocilia cause deafness and loss of balance. If less Ca(2+) is exported from the stereocilia, as in the PMCA2 mouse mutants, Ca(2+) concentration in endolymph is expected to fall causing an alteration of the mechanotransduction process. This may provide a clue as to why, in some cases, PMCA2 mutations potentiated the deafness phenotype induced by coexisting mutations of cadherin-23 (Usher syndrome type 1D), a single pass membrane Ca(2+) binding protein that is abundantly expressed in the stereocilia.
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Affiliation(s)
- Fabio Mammano
- Department of Physics "G. Galilei," University of Padova, Italy.
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19
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Chou SW, Hwang P, Gomez G, Fernando CA, West MC, Pollock LM, Lin-Jones J, Burnside B, McDermott BM. Fascin 2b is a component of stereocilia that lengthens actin-based protrusions. PLoS One 2011; 6:e14807. [PMID: 21625653 PMCID: PMC3082522 DOI: 10.1371/journal.pone.0014807] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2010] [Accepted: 07/22/2010] [Indexed: 02/04/2023] Open
Abstract
Stereocilia are actin-filled protrusions that permit mechanotransduction in the
internal ear. To identify proteins that organize the cytoskeleton of
stereocilia, we scrutinized the hair-cell transcriptome of zebrafish. One
promising candidate encodes fascin 2b, a filamentous actin-bundling protein
found in retinal photoreceptors. Immunolabeling of zebrafish hair cells and the
use of transgenic zebrafish that expressed fascin 2b fused to green fluorescent
protein demonstrated that fascin 2b localized to stereocilia specifically. When
filamentous actin and recombinant fusion protein containing fascin 2b were
combined in vitro to determine their dissociation constant, a
Kd≈0.37 µM was observed. Electron
microscopy showed that fascin 2b-actin filament complexes formed parallel actin
bundles in vitro. We demonstrated that expression of fascin 2b
or espin, another actin-bundling protein, in COS-7 cells induced the formation
of long filopodia. Coexpression showed synergism between these proteins through
the formation of extra-long protrusions. Using phosphomutant fascin 2b proteins,
which mimicked either a phosphorylated or a nonphosphorylated state, in COS-7
cells and in transgenic hair cells, we showed that both formation of long
filopodia and localization of fascin 2b to stereocilia were dependent on serine
38. Overexpression of wild-type fascin 2b in hair cells was correlated with
increased stereociliary length relative to controls. These findings indicate
that fascin 2b plays a key role in shaping stereocilia.
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Affiliation(s)
- Shih-Wei Chou
- Department of Otolaryngology–Head and
Neck Surgery, Case Western Reserve University School of Medicine, Cleveland,
Ohio, United States of America
- Department of Biology, Case Western Reserve
University, Cleveland, Ohio, United States of America
| | - Philsang Hwang
- Department of Otolaryngology–Head and
Neck Surgery, Case Western Reserve University School of Medicine, Cleveland,
Ohio, United States of America
- Department of Biology, Case Western Reserve
University, Cleveland, Ohio, United States of America
| | - Gustavo Gomez
- Department of Otolaryngology–Head and
Neck Surgery, Case Western Reserve University School of Medicine, Cleveland,
Ohio, United States of America
| | - Carol A. Fernando
- Department of Otolaryngology–Head and
Neck Surgery, Case Western Reserve University School of Medicine, Cleveland,
Ohio, United States of America
| | - Megan C. West
- Department of Otolaryngology–Head and
Neck Surgery, Case Western Reserve University School of Medicine, Cleveland,
Ohio, United States of America
- Department of Biology, Case Western Reserve
University, Cleveland, Ohio, United States of America
| | - Lana M. Pollock
- Department of Otolaryngology–Head and
Neck Surgery, Case Western Reserve University School of Medicine, Cleveland,
Ohio, United States of America
- Department of Genetics, Case Western Reserve
University School of Medicine, Cleveland, Ohio, United States of
America
| | - Jennifer Lin-Jones
- Department of Molecular and Cell Biology,
University of California, Berkeley, California, United States of
America
| | - Beth Burnside
- Department of Molecular and Cell Biology,
University of California, Berkeley, California, United States of
America
| | - Brian M. McDermott
- Department of Otolaryngology–Head and
Neck Surgery, Case Western Reserve University School of Medicine, Cleveland,
Ohio, United States of America
- Department of Biology, Case Western Reserve
University, Cleveland, Ohio, United States of America
- Department of Genetics, Case Western Reserve
University School of Medicine, Cleveland, Ohio, United States of
America
- Department of Neurosciences, Case Western
Reserve University School of Medicine, Cleveland, Ohio, United States of
America
- * E-mail:
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20
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Weston MD, Pierce ML, Jensen-Smith HC, Fritzsch B, Rocha-Sanchez S, Beisel KW, Soukup GA. MicroRNA-183 family expression in hair cell development and requirement of microRNAs for hair cell maintenance and survival. Dev Dyn 2011; 240:808-19. [PMID: 21360794 DOI: 10.1002/dvdy.22591] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/25/2011] [Indexed: 01/09/2023] Open
Abstract
MicroRNAs (miRNAs) post-transcriptionally repress complementary target gene expression and can contribute to cell differentiation. The coordinate expression of miRNA-183 family members (miR-183, miR-96, and miR-182) has been demonstrated in sensory cells of the mouse inner ear and other vertebrate sensory organs. To further examine hair cell miRNA expression in the mouse inner ear, we have analyzed miR-183 family expression in wild type animals and various mutants with defects in neurosensory development. miR-183 family member expression follows neurosensory cell specification, exhibits longitudinal (basal-apical) gradients in maturating cochlear hair cells, and is maintained in sensory neurons and most hair cells into adulthood. Depletion of hair cell miRNAs resulting from Dicer1 conditional knockout (CKO) in Atoh1-Cre transgenic mice leads to more disparate basal-apical gene expression profiles and eventual hair cell loss. Results suggest that hair cell miRNAs subdue cochlear gradient gene expression and are required for hair cell maintenance and survival.
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21
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Sciarretta C, Fritzsch B, Beisel K, Rocha-Sanchez SM, Buniello A, Horn JM, Minichiello L. PLCγ-activated signalling is essential for TrkB mediated sensory neuron structural plasticity. BMC DEVELOPMENTAL BIOLOGY 2010; 10:103. [PMID: 20932311 PMCID: PMC2964534 DOI: 10.1186/1471-213x-10-103] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 10/08/2010] [Indexed: 11/10/2022]
Abstract
Background The vestibular system provides the primary input of our sense of balance and spatial orientation. Dysfunction of the vestibular system can severely affect a person's quality of life. Therefore, understanding the molecular basis of vestibular neuron survival, maintenance, and innervation of the target sensory epithelia is fundamental. Results Here we report that a point mutation at the phospholipase Cγ (PLCγ) docking site in the mouse neurotrophin tyrosine kinase receptor TrkB (Ntrk2) specifically impairs fiber guidance inside the vestibular sensory epithelia, but has limited effects on the survival of vestibular sensory neurons and growth of afferent processes toward the sensory epithelia. We also show that expression of the TRPC3 cation calcium channel, whose activity is known to be required for nerve-growth cone guidance induced by brain-derived neurotrophic factor (BDNF), is altered in these animals. In addition, we find that absence of the PLCγ mediated TrkB signalling interferes with the transformation of bouton type afferent terminals of vestibular dendrites into calyces (the largest synaptic contact of dendrites known in the mammalian nervous system) on type I vestibular hair cells; the latter are normally distributed in these mutants as revealed by an unaltered expression pattern of the potassium channel KCNQ4 in these cells. Conclusions These results demonstrate a crucial involvement of the TrkB/PLCγ-mediated intracellular signalling in structural aspects of sensory neuron plasticity.
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Affiliation(s)
- Carla Sciarretta
- European Molecular Biology Laboratory, Mouse Biology Unit, Via Ramornie 32, 00015 Monterotondo, Rome, Italy
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22
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Lv P, Wei D, Yamoah EN. Kv7-type channel currents in spiral ganglion neurons: involvement in sensorineural hearing loss. J Biol Chem 2010; 285:34699-707. [PMID: 20739290 DOI: 10.1074/jbc.m110.136192] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alterations in K(v)7-mediated currents in excitable cells result in several diseased conditions. A case in DFNA2, an autosomal dominant version of progressive hearing loss, involves degeneration of hair cells and spiral ganglion neurons (SGNs) from basal to apical cochlea, manifesting as high-to-low frequency hearing loss, and has been ascribed to mutations in K(v)7.4 channels. Analyses of the cellular mechanisms of K(v)7.4 mutations and progressive degeneration of SGNs have been hampered by the paucity of functional data on the role K(v)7 channels play in young and adult neurons. To understand the cellular mechanisms of the disease in SGNs, we examined temporal (young, 0.5 months old, and senescent, 17 months old) and spatial (apical and basal) roles of K(v)7-mediated currents. We report that differential contribution of K(v)7 currents in mice SGNs results in distinct and profound variations of the membrane properties of basal versus apical neurons. The current produces a major impact on the resting membrane potential of basal neurons. Inhibition of the current promotes membrane depolarization, resulting in activation of Ca(2+) currents and a sustained rise in intracellular Ca(2+). Using TUNEL assay, we demonstrate that a sustained increase in intracellular Ca(2+) mediated by inhibition of K(v)7 current results in significant SGN apoptotic death. Thus, this study provides evidence of the cellular etiology and mechanisms of SGN degeneration in DFNA2.
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Affiliation(s)
- Ping Lv
- Department of Anesthesiology and Pain Medicine, School of Medicine, University of California, Davis, California 95618, USA
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23
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Huss D, Navaluri R, Faulkner KF, Dickman JD. Development of otolith receptors in Japanese quail. Dev Neurobiol 2010; 70:436-55. [PMID: 20155736 DOI: 10.1002/dneu.20787] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
This study examined the morphological development of the otolith vestibular receptors in quail. Here, we describe epithelial growth, hair cell density, stereocilia polarization, and afferent nerve innervation during development. The otolith maculae epithelial areas increased exponentially throughout embryonic development reaching asymptotic values near posthatch day P7. Increases in hair cell density were dependent upon macular location; striolar hair cells developed first followed by hair cells in extrastriola regions. Stereocilia polarization was initiated early, with defining reversal zones forming at E8. Less than half of all immature hair cells observed had nonpolarized internal kinocilia with the remaining exhibiting planar polarity. Immunohistochemistry and neural tracing techniques were employed to examine the shape and location of the striolar regions. Initial innervation of the maculae was by small fibers with terminal growth cones at E6, followed by collateral branches with apparent bouton terminals at E8. Calyceal terminal formation began at E10; however, no mature calyces were observed until E12, when all fibers appeared to be dimorphs. Calyx afferents innervating only Type I hair cells did not develop until E14. Finally, the topographic organization of afferent macular innervation in the adult quail utricle was quantified. Calyx and dimorph afferents were primarily confined to the striolar regions, while bouton fibers were located in the extrastriola and Type II band. Calyx fibers were the least complex, followed by dimorph units. Bouton fibers had large innervation fields, with arborous branches and many terminal boutons.
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Affiliation(s)
- David Huss
- Department of Biology, California Institute of Technology, Pasadena, California 91125, USA
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24
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Majumder P, Crispino G, Rodriguez L, Ciubotaru CD, Anselmi F, Piazza V, Bortolozzi M, Mammano F. ATP-mediated cell-cell signaling in the organ of Corti: the role of connexin channels. Purinergic Signal 2010; 6:167-87. [PMID: 20806010 PMCID: PMC2912995 DOI: 10.1007/s11302-010-9192-9] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 05/31/2010] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Connexin 26 (Cx26) and connexin 30 (Cx30) form hemichannels that release ATP from the endolymphatic surface of cochlear supporting and epithelial cells and also form gap junction (GJ) channels that allow the concomitant intercellular diffusion of Ca(2+) mobilizing second messengers. Released ATP in turn activates G-protein coupled P2Y(2) and P2Y(4) receptors, PLC-dependent generation of IP(3), release of Ca(2+) from intracellular stores, instigating the regenerative propagation of intercellular Ca(2+) signals (ICS). The range of ICS propagation is sensitive to the concentration of extracellular divalent cations and activity of ectonucleotidases. Here, the expression patterns of Cx26 and Cx30 were characterized in postnatal cochlear tissues obtained from mice aged between P5 and P6. The expression gradient along the longitudinal axis of the cochlea, decreasing from the basal to the apical cochlear turn (CT), was more pronounced in outer sulcus (OS) cells than in inner sulcus (IS) cells. GJ-mediated dye coupling was maximal in OS cells of the basal CT, inhibited by the nonselective connexin channel blocker carbenoxolone (CBX) and absent in hair cells. Photostimulating OS cells with caged inositol (3,4,5) tri-phosphate (IP(3)) resulted in transfer of ICS in the lateral direction, from OS cells to IS cells across the hair cell region (HCR) of medial and basal CTs. ICS transfer in the opposite (medial) direction, from IS cells photostimulated with caged IP(3) to OS cells, occurred mostly in the basal CT. In addition, OS cells displayed impressive rhythmic activity with oscillations of cytosolic free Ca(2+) concentration ([Ca(2+)](i)) coordinated by the propagation of Ca(2+) wavefronts sweeping repeatedly through the same tissue area along the coiling axis of the cochlea. Oscillations evoked by uncaging IP(3) or by applying ATP differed greatly, by as much as one order of magnitude, in frequency and waveform rise time. ICS evoked by direct application of ATP propagated along convoluted cellular paths in the OS, which often branched and changed dynamically over time. Potential implications of these findings are discussed in the context of developmental regulation and cochlear pathophysiology. ELECTRONIC SUPPLEMENTARY MATERIAL The online version of this article (doi:10.1007/s11302-010-9192-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Paromita Majumder
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Giulia Crispino
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Laura Rodriguez
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Catalin Dacian Ciubotaru
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Fabio Anselmi
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Valeria Piazza
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
| | - Mario Bortolozzi
- Dipartimento di Fisica “G. Galilei”, Università di Padova, via Marzolo 8, 35129 Padova, Italy
- Istituto di Neuroscienze, CNR, Padova, Italy
| | - Fabio Mammano
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, via G. Orus 2, 35129 Padova, Italy
- Dipartimento di Fisica “G. Galilei”, Università di Padova, via Marzolo 8, 35129 Padova, Italy
- Istituto di Neuroscienze, CNR, Padova, Italy
- Centro Interdipartimentale per lo Studio dei Segnali Cellulari, Università di Padova, via G. Orus 2, 35129 Padova, Italy
- VIMM, Via G. Orus 2, 35129 Padova, Italy
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25
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Li GQ, Meredith FL, Rennie KJ. Development of K(+) and Na(+) conductances in rodent postnatal semicircular canal type I hair cells. Am J Physiol Regul Integr Comp Physiol 2009; 298:R351-8. [PMID: 19939976 DOI: 10.1152/ajpregu.00460.2009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The rodent vestibular system is immature at birth. During the first postnatal week, vestibular type I and type II hair cells start to acquire their characteristic morphology and afferent innervation. We have studied postnatal changes in the membrane properties of type I hair cells acutely isolated from the semicircular canals (SCC) of gerbils and rats using whole cell patch clamp and report for the first time developmental changes in ionic conductances in these cells. At postnatal day (P) 5 immature hair cells expressed a delayed rectifier K(+) conductance (G(DR)) which activated at potentials above approximately -50 mV in both species. Hair cells also expressed a transient Na(+) conductance (G(Na)) with a mean half-inactivation of approximately -90 mV. At P6 in rat and P7 in gerbil, a low-voltage activated K(+) conductance (G(K,L)) was first observed and conferred a low-input resistance, typical of adult type I hair cells, on SCC type I hair cells. G(K,L) expression in hair cells increased markedly during the second postnatal week and was present in all rat type I hair cells by P14. In gerbil hair cells, G(K,L) appeared later and was present in all type I hair cells by P19. During the third postnatal week, G(Na) expression declined and was absent by the fourth postnatal week in rat and the sixth postnatal week in gerbils. Understanding the ionic changes associated with hair cell maturation could help elucidate development and regeneration mechanisms in the inner ear.
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Affiliation(s)
- Gang Q Li
- Department of Otolaryngology, University of Colorado Denver, Aurora, Colorado, USA
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26
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Gómez-Casati ME, Wedemeyer C, Taranda J, Lipovsek M, Dalamon V, Elgoyhen AB, Katz E. Electrical properties and functional expression of ionic channels in cochlear inner hair cells of mice lacking the alpha10 nicotinic cholinergic receptor subunit. J Assoc Res Otolaryngol 2009; 10:221-32. [PMID: 19252947 DOI: 10.1007/s10162-009-0164-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Accepted: 02/11/2009] [Indexed: 01/12/2023] Open
Abstract
Cochlear inner hair cells (IHCs) release neurotransmitter onto afferent auditory nerve fibers in response to sound stimulation. During early development, synaptic transmission is triggered by spontaneous Ca2+ spikes which are modulated by an efferent cholinergic innervation to IHCs. This synapse is inhibitory and mediated by the alpha9alpha10 nicotinic cholinergic receptor (nAChR). After the onset of hearing, large-conductance Ca2+-activated K+ channels are acquired and both the spiking activity and the efferent innervation disappear from IHCs. In this work, we studied the developmental changes in the membrane properties of cochlear IHCs from alpha10 nAChR gene (Chrna10) "knockout" mice. Electrophysiological properties of IHCs were studied by whole-cell recordings in acutely excised apical turns of the organ of Corti from developing mice. Neither the spiking activity nor the developmental functional expression of voltage-gated and/or calcium-sensitive K+ channels is altered in the absence of the alpha10 nAChR subunit. The present results show that the alpha10 nAChR subunit is not essential for the correct establishment of the intrinsic electrical properties of IHCs during development.
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Affiliation(s)
- María Eugenia Gómez-Casati
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Vuelta de Obligado 2490, Buenos Aires 1428, Argentina
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27
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Nie L, Zhu J, Gratton MA, Liao A, Mu KJ, Nonner W, Richardson GP, Yamoah EN. Molecular identity and functional properties of a novel T-type Ca2+ channel cloned from the sensory epithelia of the mouse inner ear. J Neurophysiol 2008; 100:2287-99. [PMID: 18753322 DOI: 10.1152/jn.90707.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The molecular identity of non-Cav1.3 channels in auditory and vestibular hair cells has remained obscure, yet the evidence in support of their roles to promote diverse Ca2+-dependent functions is indisputable. Recently, a transient Cav3.1 current that serves as a functional signature for the development and regeneration of hair cells has been identified in the chicken basilar papilla. The Cav3.1 current promotes spontaneous activity of the developing hair cell, which may be essential for synapse formation. Here, we have isolated and sequenced the full-length complementary DNA of a distinct isoform of Cav3.1 in the mouse inner ear. The channel is derived from alternative splicing of exon14, exon25A, exon34, and exon35. Functional expression of the channel in Xenopus oocytes yielded Ca2+ currents, which have a permeation phenotype consistent with T-type channels. However, unlike most multiion channels, the T-type channel does not exhibit the anomalous mole fraction effect, possibly reflecting comparable permeation properties of divalent cations. The Cav3.1 channel was expressed in sensory and nonsensory epithelia of the inner ear. Moreover, there are profound changes in the expression levels during development. The differential expression of the channel during development and the pharmacology of the inner ear Cav3.1 channel may have contributed to the difficulties associated with identification of the non-Cav1.3 currents.
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Affiliation(s)
- Liping Nie
- Center for Neuroscience, Program in Communication Science, University of California, Davis, 1544 Newton Ct., Davis, CA 95618, USA
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28
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Eatock RA, Xue J, Kalluri R. Ion channels in mammalian vestibular afferents may set regularity of firing. J Exp Biol 2008; 211:1764-74. [PMID: 18490392 PMCID: PMC3311106 DOI: 10.1242/jeb.017350] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Rodent vestibular afferent neurons offer several advantages as a model system for investigating the significance and origins of regularity in neuronal firing interval. Their regularity has a bimodal distribution that defines regular and irregular afferent classes. Factors likely to be involved in setting firing regularity include the morphology and physiology of the afferents' contacts with hair cells, which may influence the averaging of synaptic noise and the afferents' intrinsic electrical properties. In vitro patch clamp studies on the cell bodies of primary vestibular afferents reveal a rich diversity of ion channels, with indications of at least two neuronal populations. Here we suggest that firing patterns of isolated vestibular ganglion somata reflect intrinsic ion channel properties, which in vivo combine with hair cell synaptic drive to produce regular and irregular firing.
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Affiliation(s)
- Ruth Anne Eatock
- Otology and Laryngology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA.
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29
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Development and regeneration of hair cells share common functional features. Proc Natl Acad Sci U S A 2007; 104:19108-13. [PMID: 18025474 DOI: 10.1073/pnas.0705927104] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The structural phenotype of neural connections in the auditory brainstem is sculpted by spontaneous and stimulus-induced neural activities during development. However, functional and molecular mechanisms of spontaneous action potentials (SAPs) in the developing cochlea are unknown. Additionally, it is unclear how regenerating hair cells establish their neural ranking in the constellation of neurons in the brainstem. We have demonstrated that a transient Ca(2+) current produced by the Ca(v)3.1 channel is expressed early in development to initiate spontaneous Ca(2+) spikes. Ca(v)1.3 currents, typical of mature hair cells, appeared later in development. Moreover, there is a surprising disappearance of the Ca(v)3.1 current that coincides with the attenuation of the transient Ca(2+) current as the electrical properties of hair cells transition to the mature phenotype. Remarkably, this process is recapitulated during hair-cell regeneration, suggesting that the transient expression of Ca(v)3.1 and the ensuing SAPs are signatures of hair cell development and regeneration.
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30
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Brugeaud A, Travo C, Demêmes D, Lenoir M, Llorens J, Puel JL, Chabbert C. Control of hair cell excitability by vestibular primary sensory neurons. J Neurosci 2007; 27:3503-11. [PMID: 17392466 PMCID: PMC1994966 DOI: 10.1523/jneurosci.5185-06.2007] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the rat utricle, synaptic contacts between hair cells and the nerve fibers arising from the vestibular primary neurons form during the first week after birth. During that period, the sodium-based excitability that characterizes neonate utricle sensory cells is switched off. To investigate whether the establishment of synaptic contacts was responsible for the modulation of the hair cell excitability, we used an organotypic culture of rat utricle in which the setting of synapses was prevented. Under this condition, the voltage-gated sodium current and the underlying action potentials persisted in a large proportion of nonafferented hair cells. We then studied whether impairment of nerve terminals in the utricle of adult rats may also affect hair cell excitability. We induced selective and transient damages of afferent terminals using glutamate excitotoxicity in vivo. The efficiency of the excitotoxic injury was attested by selective swellings of the terminals and underlying altered vestibular behavior. Under this condition, the sodium-based excitability transiently recovered in hair cells. These results indicate that the modulation of hair cell excitability depends on the state of the afferent terminals. In adult utricle hair cells, this property may be essential to set the conditions required for restoration of the sensory network after damage. This is achieved via re-expression of a biological process that occurs during synaptogenesis.
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Affiliation(s)
- Aurore Brugeaud
- Institut National de la Santé et de la Recherche Médicale Unité 583, 34091 Montpellier, France, and
| | - Cécile Travo
- Institut National de la Santé et de la Recherche Médicale Unité 583, 34091 Montpellier, France, and
| | - Danielle Demêmes
- Institut National de la Santé et de la Recherche Médicale Unité 583, 34091 Montpellier, France, and
| | - Marc Lenoir
- Institut National de la Santé et de la Recherche Médicale Unité 583, 34091 Montpellier, France, and
| | - Jordi Llorens
- Departament de Ciencies Fisiologiques II, Universitat de Barcelona, l'Hospitalet de Llobregat, 08907 Barcelona, Spain
| | - Jean-Luc Puel
- Institut National de la Santé et de la Recherche Médicale Unité 583, 34091 Montpellier, France, and
| | - Christian Chabbert
- Institut National de la Santé et de la Recherche Médicale Unité 583, 34091 Montpellier, France, and
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31
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Sadeghi SG, Chacron MJ, Taylor MC, Cullen KE. Neural variability, detection thresholds, and information transmission in the vestibular system. J Neurosci 2007; 27:771-81. [PMID: 17251416 PMCID: PMC5053814 DOI: 10.1523/jneurosci.4690-06.2007] [Citation(s) in RCA: 197] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 11/25/2006] [Accepted: 12/14/2006] [Indexed: 11/21/2022] Open
Abstract
A fundamental issue in neural coding is the role of spike timing variation in information transmission of sensory stimuli. Vestibular afferents are particularly well suited to study this issue because they are classified as either regular or irregular based on resting discharge variability as well as morphology. Here, we compared the responses of each afferent class to sinusoidal and random head rotations using both information theoretic and gain measures. Information theoretic measures demonstrated that regular afferents transmitted, on average, two times more information than irregular afferents, despite having significantly lower gains. Moreover, consistent with information theoretic measures, regular afferents had angular velocity detection thresholds that were 50% lower than those of irregular afferents (approximately 4 vs 8 degrees/s). Finally, to quantify the information carried by spike times, we added spike-timing jitter to the spike trains of both regular and irregular afferents. Our results showed that this significantly reduced information transmitted by regular afferents whereas it had little effect on irregular afferents. Thus, information is carried in the spike times of regular but not irregular afferents. Using a simple leaky integrate and fire model with a dynamic threshold, we show that differential levels of intrinsic noise can explain differences in the resting discharge, the responses to sensory stimuli, as well as the information carried by action potential timings of each afferent class. Our experimental and modeling results provide new insights as to how neural variability influences the strategy used by two different classes of sensory neurons to encode behaviorally relevant stimuli.
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Affiliation(s)
- Soroush G. Sadeghi
- Department of Physiology, McGill University, Montreal, Quebec, Canada H3G 1Y6, and
| | - Maurice J. Chacron
- Department of Physiology, McGill University, Montreal, Quebec, Canada H3G 1Y6, and
| | - Michael C. Taylor
- Department of Physiology, McGill University, Montreal, Quebec, Canada H3G 1Y6, and
- Department of Physics, McGill University, Montreal, Quebec, Canada H3G 1Y6
| | - Kathleen E. Cullen
- Department of Physiology, McGill University, Montreal, Quebec, Canada H3G 1Y6, and
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32
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Rocha-Sanchez SMS, Morris KA, Kachar B, Nichols D, Fritzsch B, Beisel KW. Developmental expression of Kcnq4 in vestibular neurons and neurosensory epithelia. Brain Res 2007; 1139:117-25. [PMID: 17292869 PMCID: PMC1858668 DOI: 10.1016/j.brainres.2006.12.087] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2006] [Revised: 12/19/2006] [Accepted: 12/21/2006] [Indexed: 10/23/2022]
Abstract
Sensory signal transduction of the inner ear afferent neurons and hair cells (HCs) requires numerous ionic conductances. The KCNQ4 voltage-gated M-type potassium channel is thought to set the resting membrane potential in cochlear HCs. Here we describe the spatiotemporal expression patterns of Kcnq4 and the associated alternative splice forms in the HCs of vestibular labyrinth. Whole mount immunodetection, qualitative and quantitative RT-PCR were performed to characterize the expression patterns of Kcnq4 transcripts and proteins. A topographical expression and upregulation of Kcnq4 during development was observed and indicated that Kcnq4 is not restricted to either a specific vestibular structure or cell type, but is present in afferent calyxes, vestibular ganglion neurons, and both type I and type II HCs. Of the four alternative splice variants, Kcnq4_v1 transcripts were the predominant form in the HCs, while Kcnq4_v3 was the major variant in the vestibular neurons. Differential quantitative expression of Kcnq4_v1 and Kcnq4_v3 were respectively detected in the striolar and extra-striolar regions of the utricle and saccule. Analysis of gerbils and rats yielded results similar to those obtained in mice, suggesting that the spatiotemporal expression pattern of Kcnq4 in the vestibular system is conserved among rodents. Analyses of vestibular HCs of Bdnf conditional mutant mice, which are devoid of any innervation, demonstrate that regulation of Kcnq4 expression in vestibular HCs is independent of innervation.
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MESH Headings
- Alternative Splicing
- Animals
- Brain-Derived Neurotrophic Factor/genetics
- Brain-Derived Neurotrophic Factor/metabolism
- Gene Expression Regulation, Developmental
- Hair Cells, Vestibular/cytology
- Hair Cells, Vestibular/metabolism
- Immunohistochemistry
- KCNQ Potassium Channels/genetics
- KCNQ Potassium Channels/metabolism
- Mice
- Mice, Mutant Strains
- Neurons, Afferent/cytology
- Neurons, Afferent/metabolism
- Orientation/physiology
- RNA, Messenger/analysis
- Tissue Distribution
- Vestibule, Labyrinth/cytology
- Vestibule, Labyrinth/growth & development
- Vestibule, Labyrinth/innervation
- Vestibule, Labyrinth/metabolism
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Affiliation(s)
- Sonia M S Rocha-Sanchez
- Department of Oral Biology, Creighton University School of Dentistry, 2500 California Plaza, Omaha, NE 68178, USA.
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33
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Hurley KM, Gaboyard S, Zhong M, Price SD, Wooltorton JRA, Lysakowski A, Eatock RA. M-like K+ currents in type I hair cells and calyx afferent endings of the developing rat utricle. J Neurosci 2006; 26:10253-69. [PMID: 17021181 PMCID: PMC6674627 DOI: 10.1523/jneurosci.2596-06.2006] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Revised: 08/18/2006] [Accepted: 08/21/2006] [Indexed: 12/17/2022] Open
Abstract
Type I vestibular hair cells have large K+ currents that, like neuronal M currents, activate negative to resting potential and are modulatable. In rodents, these currents are acquired postnatally. In perforated-patch recordings from rat utricular hair cells, immature hair cells [younger than postnatal day 7 (P7)] had a steady-state K+ conductance (g(-30)) with a half-activation voltage (V1/2) of -30 mV. The size and activation range did not change in maturing type II cells, but, by P16, type I cells had added a K conductance that was on average fourfold larger and activated much more negatively. This conductance may comprise two components: g(-60) (V1/2 of -60 mV) and g(-80) (V1/2 of -80 mV). g(-80) washed out during ruptured patch recordings and was blocked by a protein kinase inhibitor. M currents can include contributions from KCNQ and ether-a-go-go-related (erg) channels. KCNQ and erg channel blockers both affected the K+ currents of type I cells, with KCNQ blockers being more potent at younger than P7 and erg blockers more potent at older than P16. Single-cell reverse transcription-PCR and immunocytochemistry showed expression of KCNQ and erg subunits. We propose that KCNQ channels contribute to g(-30) and g(-60) and erg subunits contribute to g(-80). Type I hair cells are contacted by calyceal afferent endings. Recordings from dissociated calyces and afferent endings revealed large K+ conductances, including a KCNQ conductance. Calyx endings were strongly labeled by KCNQ4 and erg1 antisera. Thus, both hair cells and calyx endings have large M-like K+ conductances with the potential to control the gain of transmission.
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Affiliation(s)
- Karen M. Hurley
- The Bobby R. Alford Department of Otorhinolaryngology, Head and Neck Surgery and
| | - Sophie Gaboyard
- Department of Anatomy and Cell Biology, University of Illinois, Chicago, Illinois 60612
| | - Meng Zhong
- The Bobby R. Alford Department of Otorhinolaryngology, Head and Neck Surgery and
| | - Steven D. Price
- Department of Anatomy and Cell Biology, University of Illinois, Chicago, Illinois 60612
| | | | - Anna Lysakowski
- Department of Anatomy and Cell Biology, University of Illinois, Chicago, Illinois 60612
| | - Ruth Anne Eatock
- The Bobby R. Alford Department of Otorhinolaryngology, Head and Neck Surgery and
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, and
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34
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Weston MD, Pierce ML, Rocha-Sanchez S, Beisel KW, Soukup GA. MicroRNA gene expression in the mouse inner ear. Brain Res 2006; 1111:95-104. [PMID: 16904081 DOI: 10.1016/j.brainres.2006.07.006] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2006] [Revised: 06/30/2006] [Accepted: 07/01/2006] [Indexed: 02/02/2023]
Abstract
MicroRNAs (miRNAs) are small non-coding RNAs that function through the RNA interference (RNAi) pathway and post-transcriptionally regulate gene expression in eukaryotic organisms. While miRNAs are known to affect cellular proliferation, differentiation, and morphological development, neither their expression nor roles in mammalian inner ear development have been characterized. We have investigated the extent of miRNA expression at various time points throughout maturation of the postnatal mouse inner ear by microarray analysis. Approximately one third of known miRNAs are detected in the inner ear, and their expression persists to adulthood. Expression of such miRNAs is validated by quantitative PCR and northern blot analysis. Further analysis by in situ hybridization demonstrates that certain miRNAs exhibit cell-specific expression patterns in the mouse inner ear. Notably, we demonstrate that miRNAs previously associated with mechanosensory cells in zebrafish are also expressed in hair cells of the auditory and vestibular endorgans. Our results demonstrate that miRNA expression is abundant in the mammalian inner ear and that certain miRNAs are evolutionarily associated with mechanosensory cell development and/or function. The data suggest that miRNAs contribute substantially to genetic programs intrinsic to development and function of the mammalian inner ear and that specific miRNAs might influence formation of sensory epithelia from the primitive otic neuroepithelium.
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MESH Headings
- Animals
- Cell Differentiation/genetics
- Ear, Inner/cytology
- Ear, Inner/growth & development
- Ear, Inner/metabolism
- Gene Expression Regulation, Developmental/genetics
- Hair Cells, Auditory/cytology
- Hair Cells, Auditory/growth & development
- Hair Cells, Auditory/metabolism
- Labyrinth Supporting Cells/cytology
- Labyrinth Supporting Cells/metabolism
- Mice
- MicroRNAs/analysis
- MicroRNAs/genetics
- MicroRNAs/metabolism
- Nerve Tissue Proteins/biosynthesis
- Nerve Tissue Proteins/genetics
- Oligonucleotide Array Sequence Analysis
- Organ of Corti/cytology
- Organ of Corti/growth & development
- Organ of Corti/metabolism
- Vestibule, Labyrinth/cytology
- Vestibule, Labyrinth/growth & development
- Vestibule, Labyrinth/metabolism
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Affiliation(s)
- Michael D Weston
- Department of Biomedical Sciences, Creighton University School of Medicine, 2500 California Plaza, Omaha, Nebraska, NE 68178, USA
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35
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Beisel KW, Rocha-Sanchez SM, Ziegenbein SJ, Morris KA, Kai C, Kawai J, Carninci P, Hayashizaki Y, Davis RL. Diversity of Ca2+-activated K+ channel transcripts in inner ear hair cells. Gene 2006; 386:11-23. [PMID: 17097837 DOI: 10.1016/j.gene.2006.07.023] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Revised: 07/13/2006] [Accepted: 07/18/2006] [Indexed: 10/24/2022]
Abstract
Hair cells express a complement of ion channels, representing shared and distinct channels that confer distinct electrophysiological signatures for each cell. This diversity is generated by the use of alternative splicing in the alpha subunit, formation of heterotetrameric channels, and combinatorial association with beta subunits. These channels are thought to play a role in the tonotopic gradient observed in the mammalian cochlea. Mouse Kcnma1 transcripts, 5' and 3' ESTs, and genomic sequences were examined for the utilization of alternative splicing in the mouse transcriptome. Comparative genomic analyses investigated the conservation of KCNMA1 splice sites. Genomes of mouse, rat, human, opossum, chicken, frog and zebrafish established that the exon-intron structure and mechanism of KCNMA1 alternative splicing were highly conserved with 6-7 splice sites being utilized. The murine Kcnma1 utilized 6 out of 7 potential splice sites. RT-PCR experiments using murine gene-specific oligonucleotide primers analyzed the scope and variety of Kcnma1 and Kcnmb1-4 expression profiles in the cochlea and inner ear hair cells. In the cochlea splice variants were present representing sites 3, 4, 6, and 7, while site 1 was insertionless and site 2 utilized only exon 10. However, site 5 was not present. Detection of KCNMA1 transcripts and protein exhibited a quantitative longitudinal gradient with a reciprocal gradient found between inner and outer hair cells. Differential expression was also observed in the usage of the long form of the carboxy-terminus tail. These results suggest that a diversity of splice variants exist in rodent cochlear hair cells and this diversity is similar to that observed for non-mammalian vertebrate hair cells, such as chicken and turtle.
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Affiliation(s)
- Kirk W Beisel
- Department of Biomedical Sciences, Creighton University, 2500 California Plaza, Omaha, Nebraska 68178, USA
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36
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Marcotti W, Erven A, Johnson SL, Steel KP, Kros CJ. Tmc1 is necessary for normal functional maturation and survival of inner and outer hair cells in the mouse cochlea. J Physiol 2006; 574:677-98. [PMID: 16627570 PMCID: PMC1817746 DOI: 10.1113/jphysiol.2005.095661] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The deafness (dn) and Beethoven (Bth) mutant mice are models for profound congenital deafness (DFNB7/B11) and progressive hearing loss (DFNA36), respectively, caused by recessive and dominant mutations of transmembrane cochlear-expressed gene 1 (TMC1), which encodes a transmembrane protein of unknown function. In the mouse cochlea Tmc1 is expressed in both outer (OHCs) and inner (IHCs) hair cells from early stages of development. Immature hair cells of mutant mice seem normal in appearance and biophysical properties. From around P8 for OHCs and P12 for IHCs, mutants fail to acquire (dn/dn) or show reduced expression (Bth/Bth and, to a lesser extent Bth/+) of the K+ currents which contribute to their normal functional maturation (the BK-type current IK,f in IHCs, and the delayed rectifier IK,n in both cell types). Moreover, the exocytotic machinery in mutant IHCs does not develop normally as judged by the persistence of immature features of the Ca2+ current and exocytosis into adulthood. Mutant mice exhibited progressive hair cell damage and loss. The compound action potential (CAP) thresholds of Bth/+ mice were raised and correlated with the degree of hair cell loss. Homozygous mutants (dn/dn and Bth/Bth) never showed CAP responses, even at ages where many hair cells were still present in the apex of the cochlea, suggesting their hair cells never function normally. We propose that Tmc1 is involved in trafficking of molecules to the plasma membrane or serves as an intracellular regulatory signal for differentiation of immature hair cells into fully functional auditory receptors.
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MESH Headings
- Animals
- Cell Differentiation
- Cell Proliferation
- Cell Survival
- Cells, Cultured
- Cochlea/cytology
- Cochlea/physiology
- Hair Cells, Auditory, Inner/cytology
- Hair Cells, Auditory, Inner/physiology
- Hair Cells, Auditory, Outer/cytology
- Hair Cells, Auditory, Outer/physiology
- Membrane Proteins/metabolism
- Mice
- Mice, Transgenic
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Affiliation(s)
- Walter Marcotti
- School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK
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37
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Kelley MW. Hair cell development: commitment through differentiation. Brain Res 2006; 1091:172-85. [PMID: 16626654 DOI: 10.1016/j.brainres.2006.02.062] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Revised: 02/15/2006] [Accepted: 02/17/2006] [Indexed: 10/24/2022]
Abstract
The perceptions of sound, balance and acceleration are mediated through the vibration of stereociliary bundles located on the lumenal surfaces of mechanosensory hair cells located within the inner ear. In mammals, virtually all hair cells are generated during a relatively brief period in embryogenesis with any subsequent hair cell loss leading to a progressive and permanent loss of sensitivity. In light of the importance of these cells, considerable effort has been focused on understanding the molecular genetic pathways that regulate their development. The results of these studies have begun to elucidate the signaling molecules that regulate several key events in hair cell development. In particular, significant progress has been made in the understanding of hair cell commitment, survival and differentiation. In addition, several aspects of the development of the stereociliary bundle, including its elongation and orientation, have recently been examined. This review will summarize results from each of these developmental events and describe the molecular signaling pathways involved.
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Affiliation(s)
- Matthew W Kelley
- Section on Developmental Neuroscience, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 35 Convent Drive, Bethesda, MA 20892, USA.
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38
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Géléoc GSG, Risner JR, Holt JR. Developmental acquisition of voltage-dependent conductances and sensory signaling in hair cells of the embryonic mouse inner ear. J Neurosci 2005; 24:11148-59. [PMID: 15590931 PMCID: PMC2638092 DOI: 10.1523/jneurosci.2662-04.2004] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
How and when sensory hair cells acquire the remarkable ability to detect and transmit mechanical information carried by sound and head movements has not been illuminated. Previously, we defined the onset of mechanotransduction in embryonic hair cells of mouse vestibular organs to be at approximately embryonic day 16 (E16). Here we examine the functional maturation of hair cells in intact sensory epithelia excised from the inner ears of embryonic mice. Hair cells were studied at stages between E14 and postnatal day 2 using the whole-cell, tight-seal recording technique. We tracked the developmental acquisition of four voltage-dependent conductances. We found a delayed rectifier potassium conductance that appeared as early as E14 and grew in amplitude over the subsequent prenatal week. Interestingly, we also found a low-voltage-activated potassium conductance present at E18, approximately 1 week earlier than reported previously. An inward rectifier conductance appeared at approximately E15 and doubled in size over the next few days. We also noted transient expression of a voltage-gated sodium conductance that peaked between E16 and E18 and then declined to near zero at birth. We propose that hair cells undergo a stereotyped developmental pattern of ion channel acquisition and that the precise pattern may underlie other developmental processes such as synaptogenesis and functional differentiation into type I and type II hair cells. In addition, we find that the developmental acquisition of basolateral conductances shapes the hair cell receptor potential and therefore comprises an important step in the signal cascade from mechanotransduction to neurotransmission.
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Affiliation(s)
- Gwenaëlle S G Géléoc
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia 22932, USA
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