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Liu Z, Bai X, Wan P, Mo F, Chen G, Zhang J, Gao J. Targeted Deletion of Loxl3 by Col2a1-Cre Leads to Progressive Hearing Loss. Front Cell Dev Biol 2021; 9:683495. [PMID: 34150778 PMCID: PMC8212933 DOI: 10.3389/fcell.2021.683495] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Accepted: 05/11/2021] [Indexed: 12/20/2022] Open
Abstract
Collagens are major constituents of the extracellular matrix (ECM) that play an essential role in the structure of the inner ear and provide elasticity and rigidity when the signals of sound are received and transformed into electrical signals. LOXL3 is a member of the lysyl oxidase (LOX) family that are copper-dependent amine oxidases, generating covalent cross-links to stabilize polymeric elastin and collagen fibers in the ECM. Biallelic missense variant of LOXL3 was found in Stickler syndrome with mild conductive hearing loss. However, available information regarding the specific roles of LOXL3 in auditory function is limited. In this study, we showed that the Col2a1-Cre-mediated ablation of Loxl3 in the inner ear can cause progressive hearing loss, degeneration of hair cells and secondary degeneration of spiral ganglion neurons. The abnormal distribution of type II collagen in the spiral ligament and increased inflammatory responses were also found in Col2a1–Loxl3–/– mice. Amino oxidase activity exerts an effect on collagen; thus, Loxl3 deficiency was expected to result in the instability of collagen in the spiral ligament and the basilar membrane, which may interfere with the mechanical properties of the organ of Corti and induce the inflammatory responses that are responsible for the hearing loss. Overall, our findings suggest that Loxl3 may play an essential role in maintaining hearing function.
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Affiliation(s)
- Ziyi Liu
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
| | - Xinfeng Bai
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
| | - Peifeng Wan
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
| | - Fan Mo
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
| | - Ge Chen
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
| | - Jian Zhang
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
| | - Jiangang Gao
- School of Life Science and Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong University, Jinan, China
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Tarchini B, Lu X. New insights into regulation and function of planar polarity in the inner ear. Neurosci Lett 2019; 709:134373. [PMID: 31295539 PMCID: PMC6732021 DOI: 10.1016/j.neulet.2019.134373] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 07/02/2019] [Accepted: 07/06/2019] [Indexed: 12/18/2022]
Abstract
Acquisition of cell polarity generates signaling and cytoskeletal asymmetry and thus underpins polarized cell behaviors during tissue morphogenesis. In epithelial tissues, both apical-basal polarity and planar polarity, which refers to cell polarization along an axis orthogonal to the apical-basal axis, are essential for epithelial morphogenesis and function. A prime example of epithelial planar polarity can be found in the auditory sensory epithelium (or organ of Corti, OC). Sensory hair cells, the sound receptors, acquire a planar polarized apical cytoskeleton which is uniformely oriented along an axis orthogonal to the longitudinal axis of the cochlear duct. Both cell-intrinsic and tissue-level planar polarity are necessary for proper perception of sound. Here we review recent insights into the novel roles and mechanisms of planar polarity signaling gained from genetic analysis in mice, focusing mainly on the OC but also with some discussions on the vestibular sensory epithelia.
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Affiliation(s)
- Basile Tarchini
- The Jackson Laboratory, Bar Harbor, ME, 04609, USA; Department of Medicine, Tufts University, Boston, 02111, MA, USA; Graduate School of Biomedical Science and Engineering (GSBSE), University of Maine, Orono, 04469, ME, USA.
| | - Xiaowei Lu
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA, 22908, USA.
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Bowling T, Lemons C, Meaud J. Reducing tectorial membrane viscoelasticity enhances spontaneous otoacoustic emissions and compromises the detection of low level sound. Sci Rep 2019; 9:7494. [PMID: 31097743 PMCID: PMC6522542 DOI: 10.1038/s41598-019-43970-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/02/2019] [Indexed: 01/08/2023] Open
Abstract
The mammalian cochlea is able to detect faint sounds due to the presence of an active nonlinear feedback mechanism that boosts cochlear vibrations of low amplitude. Because of this feedback, self-sustained oscillations called spontaneous otoacoustic emissions (SOAEs) can often be measured in the ear canal. Recent experiments in genetically modified mice have demonstrated that mutations of the genes expressed in the tectorial membrane (TM), an extracellular matrix located in the cochlea, can significantly enhance the generation of SOAEs. Multiple untested mechanisms have been proposed to explain these unexpected results. In this work, a physiologically motivated computational model of a mammalian species commonly studied in auditory research, the gerbil, is used to demonstrate that altering the viscoelastic properties of the TM tends to affect the linear stability of the cochlea, SOAE generation and the cochlear response to low amplitude stimuli. These results suggest that changes in TM properties might be the underlying cause for SOAE enhancement in some mutant mice. Furthermore, these theoretical findings imply that the TM contributes to keeping the mammalian cochlea near an oscillatory instability, which promotes high sensitivity and the detection of low level stimuli.
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Affiliation(s)
- Thomas Bowling
- G.W.W. School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive NW, Atlanta, Georgia, 30332, USA
| | - Charlsie Lemons
- G.W.W. School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive NW, Atlanta, Georgia, 30332, USA
| | - Julien Meaud
- G.W.W. School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive NW, Atlanta, Georgia, 30332, USA. .,Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
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4
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A synthetic AAV vector enables safe and efficient gene transfer to the mammalian inner ear. Nat Biotechnol 2017; 35:280-284. [PMID: 28165475 PMCID: PMC5340646 DOI: 10.1038/nbt.3781] [Citation(s) in RCA: 216] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 01/04/2017] [Indexed: 01/01/2023]
Abstract
Efforts to develop gene therapies for hearing loss have been hampered by the lack of safe, efficient, and clinically relevant delivery modalities1, 2. Here we demonstrate the safety and efficiency of Anc80L65, a rationally designed synthetic vector3, for transgene delivery to the mouse cochlea. Cochlear explants incubated with Anc80L65 encoding eGFP demonstrated high level transduction of inner and outer hair cells (60–100%). Injection of Anc80L65 through the round window membrane resulted in highly efficient transduction of inner and outer hair cells, a substantial improvement over conventional adeno-associated virus (AAV) vectors. Anc80L65 round window injection was well tolerated, as indicated by sensory cell function, hearing and vestibular function, and immunologic parameters. The ability of Anc80L65 to target outer hair cells at high rates, a requirement for restoration of complex auditory function, may enable future gene therapies for hearing and balance disorders.
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Andrade LR, Salles FT, Grati M, Manor U, Kachar B. Tectorins crosslink type II collagen fibrils and connect the tectorial membrane to the spiral limbus. J Struct Biol 2016; 194:139-46. [PMID: 26806019 DOI: 10.1016/j.jsb.2016.01.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 01/12/2016] [Indexed: 12/23/2022]
Abstract
All inner ear organs possess extracellular matrix appendices over the sensory epithelia that are crucial for their proper function. The tectorial membrane (TM) is a gelatinous acellular membrane located above the hearing sensory epithelium and is composed mostly of type II collagen, and α and β tectorins. TM molecules self-assemble in the endolymph fluid environment, interacting medially with the spiral limbus and distally with the outer hair cell stereocilia. Here, we used immunogold labeling in freeze-substituted mouse cochleae to assess the fine localization of both tectorins in distinct TM regions. We observed that the TM adheres to the spiral limbus through a dense thin matrix enriched in α- and β-tectorin, both likely bound to the membranes of interdental cells. Freeze-etching images revealed that type II collagen fibrils were crosslinked by short thin filaments (4±1.5nm, width), resembling another collagen type protein, or chains of globular elements (15±3.2nm, diameter). Gold-particles for both tectorins also localized adjacent to the type II collagen fibrils, suggesting that these globules might be composed essentially of α- and β-tectorins. Finally, the presence of gold-particles at the TM lower side suggests that the outer hair cell stereocilia membrane has a molecular partner to tectorins, probably stereocilin, allowing the physical connection between the TM and the organ of Corti.
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Affiliation(s)
- Leonardo R Andrade
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Present address: Laboratory of Biomineralization, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil.
| | - Felipe T Salles
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Present address: Department of Community Dentistry and Behavioral Science, University of Florida College of Dentistry, Gainesville, FL 32610, USA
| | - M'hamed Grati
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Present address: Laboratory of Molecular Genetics, Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Uri Manor
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA; Present address: Section on Organelle Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Bechara Kachar
- Laboratory of Cell Structure and Dynamics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
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Longitudinal spread of mechanical excitation through tectorial membrane traveling waves. Proc Natl Acad Sci U S A 2015; 112:12968-73. [PMID: 26438861 DOI: 10.1073/pnas.1511620112] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mammalian inner ear separates sounds by their frequency content, and this separation underlies important properties of human hearing, including our ability to understand speech in noisy environments. Studies of genetic disorders of hearing have demonstrated a link between frequency selectivity and wave properties of the tectorial membrane (TM). To understand these wave properties better, we developed chemical manipulations that systematically and reversibly alter TM stiffness and viscosity. Using microfabricated shear probes, we show that (i) reducing pH reduces TM stiffness with little change in TM viscosity and (ii) adding PEG increases TM viscosity with little change in TM stiffness. By applying these manipulations in measurements of TM waves, we show that TM wave speed is determined primarily by stiffness at low frequencies and by viscosity at high frequencies. Both TM viscosity and stiffness affect the longitudinal spread of mechanical excitation through the TM over a broad range of frequencies. Increasing TM viscosity or decreasing stiffness reduces longitudinal spread of mechanical excitation, thereby coupling a smaller range of best frequencies and sharpening tuning. In contrast, increasing viscous loss or decreasing stiffness would tend to broaden tuning in resonance-based TM models. Thus, TM wave and resonance mechanisms are fundamentally different in the way they control frequency selectivity.
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Sellon JB, Ghaffari R, Farrahi S, Richardson GP, Freeman DM. Porosity controls spread of excitation in tectorial membrane traveling waves. Biophys J 2014; 106:1406-13. [PMID: 24655516 DOI: 10.1016/j.bpj.2014.02.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 02/05/2014] [Accepted: 02/06/2014] [Indexed: 11/18/2022] Open
Abstract
Cochlear frequency selectivity plays a key role in our ability to understand speech, and is widely believed to be associated with cochlear amplification. However, genetic studies targeting the tectorial membrane (TM) have demonstrated both sharper and broader tuning with no obvious changes in hair bundle or somatic motility mechanisms. For example, cochlear tuning of Tectb(-/-) mice is significantly sharper than that of Tecta(Y1870C/+) mice, even though TM stiffnesses are similarly reduced relative to wild-type TMs. Here we show that differences in TM viscosity can account for these differences in tuning. In the basal cochlear turn, nanoscale pores of Tecta(Y1870C/+) TMs are significantly larger than those of Tectb(-/-) TMs. The larger pore size reduces shear viscosity (by ∼70%), thereby reducing traveling wave speed and increasing spread of excitation. These results demonstrate the previously unrecognized importance of TM porosity in cochlear and neural tuning.
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Affiliation(s)
- Jonathan B Sellon
- Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Cambridge, Massachusetts; Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Roozbeh Ghaffari
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Shirin Farrahi
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts; Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Guy P Richardson
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Dennis M Freeman
- Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Cambridge, Massachusetts; Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts; Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts.
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8
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Teudt IU, Richter CP. Basilar membrane and tectorial membrane stiffness in the CBA/CaJ mouse. J Assoc Res Otolaryngol 2014; 15:675-94. [PMID: 24865766 PMCID: PMC4164692 DOI: 10.1007/s10162-014-0463-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 05/07/2014] [Indexed: 10/25/2022] Open
Abstract
The mouse has become an important animal model in understanding cochlear function. Structures, such as the tectorial membrane or hair cells, have been changed by gene manipulation, and the resulting effect on cochlear function has been studied. To contrast those findings, physical properties of the basilar membrane (BM) and tectorial membrane (TM) in mice without gene mutation are of great importance. Using the hemicochlea of CBA/CaJ mice, we have demonstrated that tectorial membrane (TM) and basilar membrane (BM) revealed a stiffness gradient along the cochlea. While a simple spring mass resonator predicts the change in the characteristic frequency of the BM, the spring mass model does not predict the frequency change along the TM. Plateau stiffness values of the TM were 0.6 ± 0.5, 0.2 ± 0.1, and 0.09 ± 0.09 N/m for the basal, middle, and upper turns, respectively. The BM plateau stiffness values were 3.7 ± 2.2, 1.2 ± 1.2, and 0.5 ± 0.5 N/m for the basal, middle, and upper turns, respectively. Estimations of the TM Young's modulus (in kPa) revealed 24.3 ± 25.2 for the basal turns, 5.1 ± 4.5 for the middle turns, and 1.9 ± 1.6 for the apical turns. Young's modulus determined at the BM pectinate zone was 76.8 ± 72, 23.9 ± 30.6, and 9.4 ± 6.2 kPa for the basal, middle, and apical turns, respectively. The reported stiffness values of the CBA/CaJ mouse TM and BM provide basic data for the physical properties of its organ of Corti.
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Affiliation(s)
- I. U. Teudt
- />Department of Otolaryngology—Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Searle Building 12-561; 303 East Chicago Avenue, 60611-3008 Chicago, IL USA
- />Department of Otolaryngology—Head and Neck Surgery, University Clinic Hamburg-Eppendorf, Hamburg, Germany
- />Department of Otolaryngology—Head and Neck Surgery, Asklepios Clinic Altona, Hamburg, Germany
| | - C. P. Richter
- />Department of Otolaryngology—Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Searle Building 12-561; 303 East Chicago Avenue, 60611-3008 Chicago, IL USA
- />Department of Biomedical Engineering, Northwestern University, Evanston, IL USA
- />Hugh Knowles Center, Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL USA
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Gao SS, Wang R, Raphael PD, Moayedi Y, Groves AK, Zuo J, Applegate BE, Oghalai JS. Vibration of the organ of Corti within the cochlear apex in mice. J Neurophysiol 2014; 112:1192-204. [PMID: 24920025 DOI: 10.1152/jn.00306.2014] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The tonotopic map of the mammalian cochlea is commonly thought to be determined by the passive mechanical properties of the basilar membrane. The other tissues and cells that make up the organ of Corti also have passive mechanical properties; however, their roles are less well understood. In addition, active forces produced by outer hair cells (OHCs) enhance the vibration of the basilar membrane, termed cochlear amplification. Here, we studied how these biomechanical components interact using optical coherence tomography, which permits vibratory measurements within tissue. We measured not only classical basilar membrane tuning curves, but also vibratory responses from the rest of the organ of Corti within the mouse cochlear apex in vivo. As expected, basilar membrane tuning was sharp in live mice and broad in dead mice. Interestingly, the vibratory response of the region lateral to the OHCs, the "lateral compartment," demonstrated frequency-dependent phase differences relative to the basilar membrane. This was sharply tuned in both live and dead mice. We then measured basilar membrane and lateral compartment vibration in transgenic mice with targeted alterations in cochlear mechanics. Prestin(499/499), Prestin(-/-), and Tecta(C1509G/C1509G) mice demonstrated no cochlear amplification but maintained the lateral compartment phase difference. In contrast, Sfswap(Tg/Tg) mice maintained cochlear amplification but did not demonstrate the lateral compartment phase difference. These data indicate that the organ of Corti has complex micromechanical vibratory characteristics, with passive, yet sharply tuned, vibratory characteristics associated with the supporting cells. These characteristics may tune OHC force generation to produce the sharp frequency selectivity of mammalian hearing.
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Affiliation(s)
- Simon S Gao
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California; Department of Bioengineering, Rice University, Houston, Texas
| | - Rosalie Wang
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - Patrick D Raphael
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - Yalda Moayedi
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas
| | - Andrew K Groves
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas; Program in Developmental Biology, Baylor College of Medicine, Houston, Texas
| | - Jian Zuo
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee; and
| | - Brian E Applegate
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas
| | - John S Oghalai
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California;
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Jones GP, Lukashkina VA, Russell IJ, Elliott SJ, Lukashkin AN. Frequency-dependent properties of the tectorial membrane facilitate energy transmission and amplification in the cochlea. Biophys J 2013; 104:1357-66. [PMID: 23528095 DOI: 10.1016/j.bpj.2013.02.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 01/29/2013] [Accepted: 02/07/2013] [Indexed: 10/27/2022] Open
Abstract
The remarkable sensitivity, frequency selectivity, and dynamic range of the mammalian cochlea relies on longitudinal transmission of minuscule amounts of energy as passive, pressure-driven, basilar membrane (BM) traveling waves. These waves are actively amplified at frequency-specific locations by a mechanism that involves interaction between the BM and another extracellular matrix, the tectorial membrane (TM). From mechanical measurements of isolated segments of the TM, we made the important new (to our knowledge) discovery that the stiffness of the TM is reduced when it is mechanically stimulated at physiologically relevant magnitudes and at frequencies below their frequency place in the cochlea. The reduction in stiffness functionally uncouples the TM from the organ of Corti, thereby minimizing energy losses during passive traveling-wave propagation. Stiffening and decreased viscosity of the TM at high stimulus frequencies can potentially facilitate active amplification, especially in the high-frequency, basal turn, where energy loss due to internal friction within the TM is less than in the apex. This prediction is confirmed by neural recordings from several frequency regions of the cochlea.
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Affiliation(s)
- G P Jones
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom
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Abstract
The tectorial membrane (TM) clearly plays a mechanical role in stimulating cochlear sensory receptors, but the presence of fixed charge in TM constituents suggests that electromechanical properties also may be important. Here, we measure the fixed charge density of the TM and show that this density of fixed charge is sufficient to affect mechanical properties and to generate electrokinetic motions. In particular, alternating currents applied to the middle and marginal zones of isolated TM segments evoke motions at audio frequencies (1-1,000 Hz). Electrically evoked motions are nanometer scaled (∼5-900 nm), decrease with increasing stimulus frequency, and scale linearly over a broad range of electric field amplitudes (0.05-20 kV/m). These findings show that the mammalian TM is highly charged and suggest the importance of a unique TM electrokinetic mechanism.
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Evolutionary paths to mammalian cochleae. J Assoc Res Otolaryngol 2012; 13:733-43. [PMID: 22983571 DOI: 10.1007/s10162-012-0349-9] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 08/27/2012] [Indexed: 10/27/2022] Open
Abstract
Evolution of the cochlea and high-frequency hearing (>20 kHz; ultrasonic to humans) in mammals has been a subject of research for many years. Recent advances in paleontological techniques, especially the use of micro-CT scans, now provide important new insights that are here reviewed. True mammals arose more than 200 million years (Ma) ago. Of these, three lineages survived into recent geological times. These animals uniquely developed three middle ear ossicles, but these ossicles were not initially freely suspended as in modern mammals. The earliest mammalian cochleae were only about 2 mm long and contained a lagena macula. In the multituberculate and monotreme mammalian lineages, the cochlea remained relatively short and did not coil, even in modern representatives. In the lineage leading to modern therians (placental and marsupial mammals), cochlear coiling did develop, but only after a period of at least 60 Ma. Even Late Jurassic mammals show only a 270 ° cochlear coil and a cochlear canal length of merely 3 mm. Comparisons of modern organisms, mammalian ancestors, and the state of the middle ear strongly suggest that high-frequency hearing (>20 kHz) was not realized until the early Cretaceous (~125 Ma). At that time, therian mammals arose and possessed a fully coiled cochlea. The evolution of modern features of the middle ear and cochlea in the many later lineages of therians was, however, a mosaic and different features arose at different times. In parallel with cochlear structural evolution, prestins in therian mammals evolved into effective components of a new motor system. Ultrasonic hearing developed quite late-the earliest bat cochleae (~60 Ma) did not show features characteristic of those of modern bats that are sensitive to high ultrasonic frequencies.
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Keller JM, Noben-Trauth K. Genome-wide linkage analyses identify Hfhl1 and Hfhl3 with frequency-specific effects on the hearing spectrum of NIH Swiss mice. BMC Genet 2012; 13:32. [PMID: 22540152 PMCID: PMC3416580 DOI: 10.1186/1471-2156-13-32] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 04/27/2012] [Indexed: 11/26/2022] Open
Abstract
Background The mammalian cochlea receives and analyzes sound at specific places along the cochlea coil, commonly referred to as the tonotopic map. Although much is known about the cell-level molecular defects responsible for severe hearing loss, the genetics responsible for less severe and frequency-specific hearing loss remains unclear. We recently identified quantitative trait loci (QTLs) Hfhl1 and Hfhl2 that affect high-frequency hearing loss in NIH Swiss mice. Here we used 2f1-f2 distortion product otoacoustic emissions (DPOAE) measurements to refine the hearing loss phenotype. We crossed the high frequency hearing loss (HFHL) line of NIH Swiss mice to three different inbred strains and performed linkage analysis on the DPOAE data obtained from the second-generation populations. Results We identified a QTL of moderate effect on chromosome 7 that affected 2f1-f2 emissions intensities (Hfhl1), confirming the results of our previous study that used auditory brainstem response (ABR) thresholds to identify QTLs affecting HFHL. We also identified a novel significant QTL on chromosome 9 (Hfhl3) with moderate effects on 2f1-f2 emissions intensities. By partitioning the DPOAE data into frequency subsets, we determined that Hfhl1 and Hfhl3 affect hearing primarily at frequencies above 24 kHz and 35 kHz, respectively. Furthermore, we uncovered additional QTLs with small effects on isolated portions of the DPOAE spectrum. Conclusions This study identifies QTLs with effects that are isolated to limited portions of the frequency map. Our results support the hypothesis that frequency-specific hearing loss results from variation in gene activity along the cochlear partition and suggest a strategy for creating a map of cochlear genes that influence differences in hearing sensitivity and/or vulnerability in restricted portions of the cochlea.
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Affiliation(s)
- James M Keller
- Laboratory of Molecular Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 5 Research Court, Rockville, MD 20850, USA.
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