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Xia A, Udagawa T, Quiñones PM, Atkinson PJ, Applegate BE, Cheng AG, Oghalai JS. The impact of targeted ablation of one row of outer hair cells and Deiters' cells on cochlear amplification. J Neurophysiol 2022; 128:1365-1373. [PMID: 36259670 PMCID: PMC9678430 DOI: 10.1152/jn.00501.2021] [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: 11/15/2021] [Revised: 10/13/2022] [Accepted: 10/17/2022] [Indexed: 11/22/2022] Open
Abstract
The mammalian cochlea contains three rows of outer hair cells (OHCs) that amplify the basilar membrane traveling wave with high gain and exquisite tuning. The pattern of OHC loss caused by typical methods of producing hearing loss in animal models (noise, ototoxic exposure, or aging) is variable and not consistent along the length of the cochlea. Thus, it is difficult to use these approaches to understand how forces from multiple OHCs summate to create normal cochlear amplification. Here, we selectively removed the third row of OHCs and Deiters' cells in adult mice and measured cochlear amplification. In the mature cochlear epithelia, expression of the Wnt target gene Lgr5 is restricted to the third row of Deiters' cells, the supporting cells directly underneath the OHCs. Diphtheria toxin administration to Lgr5DTR-EGFP/+ mice selectively ablated the third row of Deiters' cells and the third row of OHCs. Basilar membrane vibration in vivo demonstrated disproportionately lower reduction in cochlear amplification by about 13.5 dB. On a linear scale, this means that the 33% reduction in OHC number led to a 79% reduction in gain. Thus, these experimental data describe the impact of reducing the force of cochlear amplification by a specific amount. Furthermore, these data argue that because OHC forces progressively and sequentially amplify the traveling wave as it travels to its peak, the loss of even a relatively small number of OHCs, when evenly distributed longitudinally, will cause a substantial reduction in cochlear amplification.NEW & NOTEWORTHY Normal cochlear physiology involves force production from three rows of outer hair cells to amplify and tune the traveling wave. Here, we used a genetic approach to target and ablate the third row of outer hair cells in the mouse cochlea and found it reduced cochlear amplification by 79%. This means that the loss of even a relatively small number of OHCs, when evenly distributed, causes a substantial reduction in cochlear amplification.
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Affiliation(s)
- Anping Xia
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - Tomokatsu Udagawa
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
- Department of Otorhinolaryngology, The Jikei University School of Medicine, Tokyo, Japan
| | - Patricia M Quiñones
- Caruso Department of Otolaryngology-Head & Neck Surgery, University of Southern California, Los Angeles, California
| | - Patrick J Atkinson
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - Brian E Applegate
- Caruso Department of Otolaryngology-Head & Neck Surgery, University of Southern California, Los Angeles, California
- Department of Biomedical Engineering, Denney Research Center (DRB) 140, University of Southern California, Los Angeles, California
| | - Alan G Cheng
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - John S Oghalai
- Caruso Department of Otolaryngology-Head & Neck Surgery, University of Southern California, Los Angeles, California
- Department of Biomedical Engineering, Denney Research Center (DRB) 140, University of Southern California, Los Angeles, California
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Amor DJ, Stephenson SE, Mustapha M, Mensah MA, Ockeloen CW, Lee WS, Tankard RM, Phelan DG, Shinawi M, de Brouwer AP, Pfundt R, Dowling C, Toler TL, Sutton VR, Agolini E, Rinelli M, Capolino R, Martinelli D, Zampino G, Dumić M, Reardon W, Shaw-Smith C, Leventer RJ, Delatycki MB, Kleefstra T, Mundlos S, Mortier G, Bahlo M, Allen NJ, Lockhart PJ. Pathogenic Variants in GPC4 Cause Keipert Syndrome. Am J Hum Genet 2019; 104:914-924. [PMID: 30982611 DOI: 10.1016/j.ajhg.2019.02.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 02/25/2019] [Indexed: 12/22/2022] Open
Abstract
Glypicans are a family of cell-surface heparan sulfate proteoglycans that regulate growth-factor signaling during development and are thought to play a role in the regulation of morphogenesis. Whole-exome sequencing of the Australian family that defined Keipert syndrome (nasodigitoacoustic syndrome) identified a hemizygous truncating variant in the gene encoding glypican 4 (GPC4). This variant, located in the final exon of GPC4, results in premature termination of the protein 51 amino acid residues prior to the stop codon, and in concomitant loss of functionally important N-linked glycosylation (Asn514) and glycosylphosphatidylinositol (GPI) anchor (Ser529) sites. We subsequently identified seven affected males from five additional kindreds with novel and predicted pathogenic variants in GPC4. Segregation analysis and X-inactivation studies in carrier females provided supportive evidence that the GPC4 variants caused the condition. Furthermore, functional studies of recombinant protein suggested that the truncated proteins p.Gln506∗ and p.Glu496∗ were less stable than the wild type. Clinical features of Keipert syndrome included a prominent forehead, a flat midface, hypertelorism, a broad nose, downturned corners of mouth, and digital abnormalities, whereas cognitive impairment and deafness were variable features. Studies of Gpc4 knockout mice showed evidence of the two primary features of Keipert syndrome: craniofacial abnormalities and digital abnormalities. Phylogenetic analysis demonstrated that GPC4 is most closely related to GPC6, which is associated with a bone dysplasia that has a phenotypic overlap with Keipert syndrome. Overall, we have shown that pathogenic variants in GPC4 cause a loss of function that results in Keipert syndrome, making GPC4 the third human glypican to be linked to a genetic syndrome.
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Mohammadjavadi M, Ye PP, Xia A, Brown J, Popelka G, Pauly KB. Elimination of peripheral auditory pathway activation does not affect motor responses from ultrasound neuromodulation. Brain Stimul 2019; 12:901-910. [PMID: 30880027 DOI: 10.1016/j.brs.2019.03.005] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Revised: 01/28/2019] [Accepted: 03/04/2019] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Recent studies in a variety of animal models including rodents, monkeys, and humans suggest that transcranial focused ultrasound (tFUS) has considerable promise for non-invasively modulating neural activity with the ability to target deep brain structures. However, concerns have been raised that motor responses evoked by tFUS may be due to indirect activation of the auditory pathway rather than direct activation of motor circuits. OBJECTIVE In this study, we sought to examine the involvement of peripheral auditory system activation from tFUS stimulation applied to elicit motor responses. The purpose was to determine to what extent ultrasound induced auditory artifact could be a factor in ultrasound motor neuromodulation. METHODS In this study, tFUS-induced electromyography (EMG) signals were recorded and analyzed in wild-type (WT) normal hearing mice and two strains of genetically deaf mice to examine the involvement of the peripheral auditory system in tFUS-stimulated motor responses. In addition, auditory brainstem responses (ABRs) were measured to elucidate the effect of the tFUS stimulus envelope on auditory and motor responses. We also varied the tFUS stimulation duration to measure its effect on motor response duration. RESULTS We show, first, that the sharp edges in a tFUS rectangular envelope stimulus activate the peripheral afferent auditory pathway and, second, that smoothing these edges eliminates the auditory responses without affecting the motor responses in normal hearing WT mice. We further show that by eliminating peripheral auditory activity using two different strains of deaf knockout mice, motor responses are the same as in normal hearing WT mice. Finally, we demonstrate a high correlation between tFUS pulse duration and EMG response duration. CONCLUSION These results support the concept that tFUS-evoked motor responses are not a result of stimulation of the peripheral auditory system.
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Affiliation(s)
| | | | - Anping Xia
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA, USA
| | - Julian Brown
- Howard Hughes Medical Institute, Department of Neurobiology, Stanford University, Stanford, CA, USA
| | - Gerald Popelka
- Department of Radiology, Stanford University, Stanford, CA, USA; Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA, USA
| | - Kim Butts Pauly
- Department of Radiology, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA; Department of Electrical Engineering, Stanford University, Stanford, CA, USA
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Dong W, Xia A, Raphael PD, Puria S, Applegate B, Oghalai JS. Organ of Corti vibration within the intact gerbil cochlea measured by volumetric optical coherence tomography and vibrometry. J Neurophysiol 2018; 120:2847-2857. [PMID: 30281386 PMCID: PMC6337041 DOI: 10.1152/jn.00702.2017] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 09/27/2018] [Accepted: 09/27/2018] [Indexed: 12/23/2022] Open
Abstract
There is indirect evidence that the mammalian cochlea in the low-frequency apical and the more commonly studied high-frequency basal regions function in fundamentally different ways. Here, we directly tested this hypothesis by measuring sound-induced vibrations of the organ of Corti (OoC) at three turns of the gerbil cochlea using volumetric optical coherence tomography vibrometry (VOCTV), an approach that permits noninvasive imaging through the bone. In the apical turn, there was little frequency selectivity, and the displacement-vs.-frequency curves had low-pass filter characteristics with a corner frequency of ~0.5-0.9 kHz. The vibratory magnitudes increased compressively with increasing stimulus intensity at all frequencies. In the middle turn, responses were similar except for a slight peak in the response at ~2.5 kHz. The gain was ~50 dB at the peak and 30-40 dB at lower frequencies. In the basal turn, responses were sharply tuned and compressively nonlinear, consistent with observations in the literature. These data demonstrated that there is a transition of the mechanical response of the OoC along the length of the cochlea such that frequency tuning is sharper in the base than in the apex. Because the responses are fundamentally different, it is not appropriate to simply frequency shift vibratory data measured at one cochlear location to predict the cochlear responses at other locations. Furthermore, this means that the number of hair cells stimulated by sound is larger for low-frequency stimuli and smaller for high-frequency stimuli for the same intensity level. Thus the mechanisms of central processing of sounds must vary with frequency. NEW & NOTEWORTHY A volumetric optical coherence tomography and vibrometry system was used to probe cochlear mechanics within the intact gerbil cochlea. We found a gradual transition of the mechanical response of the organ of Corti along the length of the cochlea such that tuning at the base is dramatically sharper than that at the apex. These data help to explain discrepancies in the literature regarding how the cochlea processes low-frequency sounds.
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Affiliation(s)
- Wei Dong
- VA Loma Linda Healthcare System, Loma Linda, California
- Department of Otolaryngology - Head and Neck Surgery, Loma Linda University Health , Loma Linda, California
| | - Anping Xia
- Department of Otolaryngology - Head and Neck Surgery, Stanford University , Stanford, California
| | - Patrick D Raphael
- Department of Otolaryngology - Head and Neck Surgery, Stanford University , Stanford, California
| | - Sunil Puria
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary and Harvard Medical School , Boston, Massachusetts
| | - Brian Applegate
- Department of Biomedical Engineering, Texas A&M University , College Station, Texas
| | - John S Oghalai
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California , Los Angeles, California
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Kim J, Xia A, Grillet N, Applegate BE, Oghalai JS. Osmotic stabilization prevents cochlear synaptopathy after blast trauma. Proc Natl Acad Sci U S A 2018; 115:E4853-E4860. [PMID: 29735658 PMCID: PMC6003510 DOI: 10.1073/pnas.1720121115] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Traumatic noise causes hearing loss by damaging sensory hair cells and their auditory synapses. There are no treatments. Here, we investigated mice exposed to a blast wave approximating a roadside bomb. In vivo cochlear imaging revealed an increase in the volume of endolymph, the fluid within scala media, termed endolymphatic hydrops. Endolymphatic hydrops, hair cell loss, and cochlear synaptopathy were initiated by trauma to the mechanosensitive hair cell stereocilia and were K+-dependent. Increasing the osmolality of the adjacent perilymph treated endolymphatic hydrops and prevented synaptopathy, but did not prevent hair cell loss. Conversely, inducing endolymphatic hydrops in control mice by lowering perilymph osmolality caused cochlear synaptopathy that was glutamate-dependent, but did not cause hair cell loss. Thus, endolymphatic hydrops is a surrogate marker for synaptic bouton swelling after hair cells release excitotoxic levels of glutamate. Because osmotic stabilization prevents neural damage, it is a potential treatment to reduce hearing loss after noise exposure.
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Affiliation(s)
- Jinkyung Kim
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA 94305
| | - Anping Xia
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA 94305
| | - Nicolas Grillet
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, CA 94305
| | - Brian E Applegate
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843
| | - John S Oghalai
- Caruso Department of Otolaryngology-Head and Neck Surgery, University of Southern California, Los Angeles, CA 90033
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Neuroplastin Isoform Np55 Is Expressed in the Stereocilia of Outer Hair Cells and Required for Normal Outer Hair Cell Function. J Neurosci 2017; 36:9201-16. [PMID: 27581460 DOI: 10.1523/jneurosci.0093-16.2016] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Accepted: 07/14/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Neuroplastin (Nptn) is a member of the Ig superfamily and is expressed in two isoforms, Np55 and Np65. Np65 regulates synaptic transmission but the function of Np55 is unknown. In an N-ethyl-N-nitrosaurea mutagenesis screen, we have now generated a mouse line with an Nptn mutation that causes deafness. We show that Np55 is expressed in stereocilia of outer hair cells (OHCs) but not inner hair cells and affects interactions of stereocilia with the tectorial membrane. In vivo vibrometry demonstrates that cochlear amplification is absent in Nptn mutant mice, which is consistent with the failure of OHC stereocilia to maintain stable interactions with the tectorial membrane. Hair bundles show morphological defects as the mutant mice age and while mechanotransduction currents can be evoked in early postnatal hair cells, cochlea microphonics recordings indicate that mechanontransduction is affected as the mutant mice age. We thus conclude that differential splicing leads to functional diversification of Nptn, where Np55 is essential for OHC function, while Np65 is implicated in the regulation of synaptic function. SIGNIFICANCE STATEMENT Amplification of input sound signals, which is needed for the auditory sense organ to detect sounds over a wide intensity range, depends on mechanical coupling of outer hair cells to the tectorial membrane. The current study shows that neuroplastin, a member of the Ig superfamily, which has previously been linked to the regulation of synaptic plasticity, is critical to maintain a stable mechanical link of outer hair cells with the tectorial membrane. In vivo recordings demonstrate that neuroplastin is essential for sound amplification and that mutation in neuroplastin leads to auditory impairment in mice.
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Two-Dimensional Cochlear Micromechanics Measured In Vivo Demonstrate Radial Tuning within the Mouse Organ of Corti. J Neurosci 2017; 36:8160-73. [PMID: 27488636 DOI: 10.1523/jneurosci.1157-16.2016] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 06/07/2016] [Indexed: 12/18/2022] Open
Abstract
UNLABELLED The exquisite sensitivity and frequency discrimination of mammalian hearing underlie the ability to understand complex speech in noise. This requires force generation by cochlear outer hair cells (OHCs) to amplify the basilar membrane traveling wave; however, it is unclear how amplification is achieved with sharp frequency tuning. Here we investigated the origin of tuning by measuring sound-induced 2-D vibrations within the mouse organ of Corti in vivo Our goal was to determine the transfer function relating the radial shear between the structures that deflect the OHC bundle, the tectorial membrane and reticular lamina, to the transverse motion of the basilar membrane. We found that, after normalizing their responses to the vibration of the basilar membrane, the radial vibrations of the tectorial membrane and reticular lamina were tuned. The radial tuning peaked at a higher frequency than transverse basilar membrane tuning in the passive, postmortem condition. The radial tuning was similar in dead mice, indicating that this reflected passive, not active, mechanics. These findings were exaggerated in Tecta(C1509G/C1509G) mice, where the tectorial membrane is detached from OHC stereocilia, arguing that the tuning of radial vibrations within the hair cell epithelium is distinct from tectorial membrane tuning. Together, these results reveal a passive, frequency-dependent contribution to cochlear filtering that is independent of basilar membrane filtering. These data argue that passive mechanics within the organ of Corti sharpen frequency selectivity by defining which OHCs enhance the vibration of the basilar membrane, thereby tuning the gain of cochlear amplification. SIGNIFICANCE STATEMENT Outer hair cells amplify the traveling wave within the mammalian cochlea. The resultant gain and frequency sharpening are necessary for speech discrimination, particularly in the presence of background noise. Here we measured the 2-D motion of the organ of Corti in mice and found that the structures that stimulate the outer hair cell stereocilia, the tectorial membrane and reticular lamina, were sharply tuned in the radial direction. Radial tuning was similar in dead mice and in mice lacking a tectorial membrane. This suggests that radial tuning comes from passive mechanics within the hair cell epithelium, and that these mechanics, at least in part, may tune the gain of cochlear amplification.
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Santa Maria PL, Gottlieb P, Santa Maria C, Kim S, Puria S, Yang YP. Functional Outcomes of Heparin-Binding Epidermal Growth Factor-Like Growth Factor for Regeneration of Chronic Tympanic Membrane Perforations in Mice. Tissue Eng Part A 2017; 23:436-444. [PMID: 28142401 PMCID: PMC5444491 DOI: 10.1089/ten.tea.2016.0395] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 01/27/2017] [Indexed: 02/02/2023] Open
Abstract
We aim to demonstrate that regeneration of chronic tympanic perforations with heparin-binding epidermal growth factor-like growth factor (HB-EGF) delivered by an injectable hydrogel restored hearing to levels similar to that of nonperforated tympanic membranes. Chronic tympanic membrane perforation is currently managed as an outpatient surgery with tympanoplasty. Due to the costs of this procedure in the developed world and a lack of accessibility and resources in developing countries, there is a great need for a new treatment that does not require surgery. In this study, we show in a mouse model through measurement of auditory brainstem response and distortion product otoacoustic emissions that tympanic perforations lead to hearing loss and this can be predominantly recovered with HB-EGF treatment (5 μg/mL). Our animal model suggests a return to function between 2 and 6 months after treatment. Auditory brainstem response thresholds had returned to the control levels at 2 months, but the distortion product otoacoustic emissions returned between 2 and 6 months. We also show how the vibration characteristics of the regenerated tympanic membrane, as measured by laser Doppler vibrometry, can be similar to that of an unperforated tympanic membrane. Using the best available methods for preclinical evaluation in animal models, it is likely that HB-EGF-like growth factor treatment leads to regeneration of chronic tympanic membrane perforations and restoration of the tympanic membrane to normal function, suggesting a potential route for nonsurgical treatment.
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Affiliation(s)
- Peter Luke Santa Maria
- Department of Otolaryngology, Head and Neck Surgery, Stanford University, Stanford, California
- Ear Sciences Centre, The University of Western Australia, Nedlands, Australia
- Ear Science Institute Australia, Subiaco, Australia
| | - Peter Gottlieb
- Department of Mechanical Engineering, Stanford University, Stanford, California
| | - Chloe Santa Maria
- Department of Otolaryngology, Head and Neck Surgery, Stanford University, Stanford, California
- Ear Sciences Centre, The University of Western Australia, Nedlands, Australia
- Ear Science Institute Australia, Subiaco, Australia
| | - Sungwoo Kim
- Department of Orthopedic Surgery, Stanford University, Stanford, California
| | - Sunil Puria
- Department of Otolaryngology, Head and Neck Surgery, Stanford University, Stanford, California
- Department of Mechanical Engineering, Stanford University, Stanford, California
| | - Yunzhi Peter Yang
- Department of Orthopedic Surgery, Stanford University, Stanford, California
- Department of Materials Science and Engineering, Stanford University, Stanford, California
- Department of Bioengineering, Stanford University, Stanford, California
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Xia A, Liu X, Raphael PD, Applegate BE, Oghalai JS. Hair cell force generation does not amplify or tune vibrations within the chicken basilar papilla. Nat Commun 2016; 7:13133. [PMID: 27796310 PMCID: PMC5095595 DOI: 10.1038/ncomms13133] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 09/07/2016] [Indexed: 12/22/2022] Open
Abstract
Frequency tuning within the auditory papilla of most non-mammalian species is electrical, deriving from ion-channel resonance within their sensory hair cells. In contrast, tuning within the mammalian cochlea is mechanical, stemming from active mechanisms within outer hair cells that amplify the basilar membrane travelling wave. Interestingly, hair cells in the avian basilar papilla demonstrate both electrical resonance and force-generation, making it unclear which mechanism creates sharp frequency tuning. Here, we measured sound-induced vibrations within the apical half of the chicken basilar papilla in vivo and found broadly-tuned travelling waves that were not amplified. However, distortion products were found in live but not dead chickens. These findings support the idea that avian hair cells do produce force, but that their effects on vibration are small and do not sharpen tuning. Therefore, frequency tuning within the apical avian basilar papilla is not mechanical, and likely derives from hair cell electrical resonance. The avian auditory papilla has many similarities to the mammalian cochlea but whether force generation by hair cells amplifies the travelling wave, as it does in mammals, remains unknown. Here the authors show that the chicken basilar papilla does not have a ‘cochlear amplifier' and that sharp frequency tuning does not derive from mechanical vibrations.
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Affiliation(s)
- Anping Xia
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, California 94305, USA
| | - Xiaofang Liu
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, California 94305, USA.,Department of Anorectal Surgery, the First Affiliated hospital of China Medical University, 155 NanjingBei Street, ShenYang, LiaoNing Province 110001, China
| | - Patrick D Raphael
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, California 94305, USA
| | - Brian E Applegate
- Department of Biomedical Engineering, Texas A&M University, 5059 Emerging Technology Building, 3120 TAMU, College Station, Texas 77843, USA
| | - John S Oghalai
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, California 94305, USA
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Abstract
Although hyperbilirubinemia is extremely common among neonates and is usually mild and transient, it sometimes leads to bilirubin-induced neurologic damage (BIND). The auditory pathway is highly sensitive to the effects of elevated total serum/plasma bilirubin (TB) levels, with damage manifesting clinically as auditory neuropathy spectrum disorder. Compared to full-term neonates, preterm neonates are more susceptible to BIND and suffer adverse effects at lower TB levels with worse long-term outcomes. Furthermore, although standardized guidelines for management of hyperbilirubinemia exist for term and late preterm neonates, similar guidelines for neonates less than 35 weeks gestational age are limited.
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Affiliation(s)
- Cristen Olds
- Department of Otolaryngology - Head and Neck Surgery, Stanford University, 801 Welch Road, CA 94305, USA
| | - John S Oghalai
- Department of Otolaryngology - Head and Neck Surgery, Stanford University, 801 Welch Road, CA 94305, USA.
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Song Y, Xia A, Lee HY, Wang R, Ricci AJ, Oghalai JS. Activity-dependent regulation of prestin expression in mouse outer hair cells. J Neurophysiol 2015; 113:3531-42. [PMID: 25810486 DOI: 10.1152/jn.00869.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 03/19/2015] [Indexed: 12/11/2022] Open
Abstract
Prestin is a membrane protein necessary for outer hair cell (OHC) electromotility and normal hearing. Its regulatory mechanisms are unknown. Several mouse models of hearing loss demonstrate increased prestin, inspiring us to investigate how hearing loss might feedback onto OHCs. To test whether centrally mediated feedback regulates prestin, we developed a novel model of inner hair cell loss. Injection of diphtheria toxin (DT) into adult CBA mice produced significant loss of inner hair cells without affecting OHCs. Thus, DT-injected mice were deaf because they had no afferent auditory input despite OHCs continuing to receive normal auditory mechanical stimulation and having normal function. Patch-clamp experiments demonstrated no change in OHC prestin, indicating that loss of information transfer centrally did not alter prestin expression. To test whether local mechanical feedback regulates prestin, we used Tecta(C1509G) mice, where the tectorial membrane is malformed and only some OHCs are stimulated. OHCs connected to the tectorial membrane had normal prestin levels, whereas OHCs not connected to the tectorial membrane had elevated prestin levels, supporting an activity-dependent model. To test whether the endocochlear potential was necessary for prestin regulation, we studied Tecta(C1509G) mice at different developmental ages. OHCs not connected to the tectorial membrane had lower than normal prestin levels before the onset of the endocochlear potential and higher than normal prestin levels after the onset of the endocochlear potential. Taken together, these data indicate that OHC prestin levels are regulated through local feedback that requires mechanoelectrical transduction currents. This adaptation may serve to compensate for variations in the local mechanical environment.
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Affiliation(s)
- Yohan Song
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California
| | - Anping Xia
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California
| | - Hee Yoon Lee
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California
| | - Rosalie Wang
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California
| | - Anthony J Ricci
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California
| | - John S Oghalai
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California
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12
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Santa Maria PL, Kim S, Varsak YK, Yang YP. Heparin binding-epidermal growth factor-like growth factor for the regeneration of chronic tympanic membrane perforations in mice. Tissue Eng Part A 2015; 21:1483-94. [PMID: 25567607 DOI: 10.1089/ten.tea.2014.0474] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We aim to explore the role of epidermal growth factor (EGF) ligand shedding in tympanic membrane wound healing and to investigate the translation of its modulation in tissue engineering of chronic tympanic membrane perforations. Chronic suppurative otitis media (CSOM) is an infected chronic tympanic membrane perforation. Up to 200 million suffer from its associated hearing loss and it is the most common cause of pediatric hearing loss in developing countries. There is a need for nonsurgical treatment due to a worldwide lack of resources. In this study, we show that EGF ligand shedding is essential for tympanic membrane healing as it's inhibition, with KB-R7785, leads to chronic perforation in 87.9% (n=58) compared with 0% (n=20) of controls. We then show that heparin binding-EGF-like growth factor (5 μg/mL), which acts to shed EGF ligands, can regenerate chronic perforations in mouse models with 92% (22 of 24) compared with 38% (10 of 26), also with eustachian tube occlusion with 94% (18 of 19) compared with 9% (2 of 23) and with CSOM 100% (16 of 16) compared with 41% (7 of 17). We also show the nonototoxicity of this treatment and its hydrogel delivery vehicle. This provides preliminary data for a clinical trial where it could be delivered by nonspecialist trained healthcare workers and fulfill the clinical need for a nonsurgical treatment for chronic tympanic membrane perforation and CSOM.
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Affiliation(s)
- Peter Luke Santa Maria
- 1 Department of Otolaryngology, Head and Neck Surgery, Stanford University , Stanford, California
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Noninvasive in vivo imaging reveals differences between tectorial membrane and basilar membrane traveling waves in the mouse cochlea. Proc Natl Acad Sci U S A 2015; 112:3128-33. [PMID: 25737536 DOI: 10.1073/pnas.1500038112] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Sound is encoded within the auditory portion of the inner ear, the cochlea, after propagating down its length as a traveling wave. For over half a century, vibratory measurements to study cochlear traveling waves have been made using invasive approaches such as laser Doppler vibrometry. Although these studies have provided critical information regarding the nonlinear processes within the living cochlea that increase the amplitude of vibration and sharpen frequency tuning, the data have typically been limited to point measurements of basilar membrane vibration. In addition, opening the cochlea may alter its function and affect the findings. Here we describe volumetric optical coherence tomography vibrometry, a technique that overcomes these limitations by providing depth-resolved displacement measurements at 200 kHz inside a 3D volume of tissue with picometer sensitivity. We studied the mouse cochlea by imaging noninvasively through the surrounding bone to measure sound-induced vibrations of the sensory structures in vivo, and report, to our knowledge, the first measures of tectorial membrane vibration within the unopened cochlea. We found that the tectorial membrane sustains traveling wave propagation. Compared with basilar membrane traveling waves, tectorial membrane traveling waves have larger dynamic ranges, sharper frequency tuning, and apically shifted positions of peak vibration. These findings explain discrepancies between previously published basilar membrane vibration and auditory nerve single unit data. Because the tectorial membrane directly overlies the inner hair cell stereociliary bundles, these data provide the most accurate characterization of the stimulus shaping the afferent auditory response available to date.
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14
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Abstract
Hyperbilirubinemia occurs commonly in neonates and is usually mild and transient, with no long-lasting sequelae. However, bilirubin-induced neurologic damage may occur in some infants. The auditory pathway is the most sensitive part of the central nervous system to bilirubin-induced toxicity, and permanent sequelae may result from only moderately elevated total serum/plasma bilirubin levels. The damage to the auditory system occurs primarily within the brainstem and cranial nerve VIII, and manifests clinically as auditory neuropathy spectrum disorder.
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Affiliation(s)
- Cristen Olds
- Department of Otolaryngology - Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305-5739, USA
| | - John S Oghalai
- Department of Otolaryngology - Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305-5739, USA.
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15
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Huth ME, Han KH, Sotoudeh K, Hsieh YJ, Effertz T, Vu AA, Verhoeven S, Hsieh MH, Greenhouse R, Cheng AG, Ricci AJ. Designer aminoglycosides prevent cochlear hair cell loss and hearing loss. J Clin Invest 2015; 125:583-92. [PMID: 25555219 DOI: 10.1172/jci77424] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 11/13/2014] [Indexed: 02/02/2023] Open
Abstract
Bacterial infections represent a rapidly growing challenge to human health. Aminoglycosides are widely used broad-spectrum antibiotics, but they inflict permanent hearing loss in up to ~50% of patients by causing selective sensory hair cell loss. Here, we hypothesized that reducing aminoglycoside entry into hair cells via mechanotransducer channels would reduce ototoxicity, and therefore we synthesized 9 aminoglycosides with modifications based on biophysical properties of the hair cell mechanotransducer channel and interactions between aminoglycosides and the bacterial ribosome. Compared with the parent aminoglycoside sisomicin, all 9 derivatives displayed no or reduced ototoxicity, with the lead compound N1MS 17 times less ototoxic and with reduced penetration of hair cell mechanotransducer channels in rat cochlear cultures. Both N1MS and sisomicin suppressed growth of E. coli and K. pneumoniae, with N1MS exhibiting superior activity against extended spectrum β lactamase producers, despite diminished activity against P. aeruginosa and S. aureus. Moreover, systemic sisomicin treatment of mice resulted in 75% to 85% hair cell loss and profound hearing loss, whereas N1MS treatment preserved both hair cells and hearing. Finally, in mice with E. coli-infected bladders, systemic N1MS treatment eliminated bacteria from urinary tract tissues and serially collected urine samples, without compromising auditory and kidney functions. Together, our findings establish N1MS as a nonototoxic aminoglycoside and support targeted modification as a promising approach to generating nonototoxic antibiotics.
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16
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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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17
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Calton MA, Lee D, Sundaresan S, Mendus D, Leu R, Wangsawihardja F, Johnson KR, Mustapha M. A lack of immune system genes causes loss in high frequency hearing but does not disrupt cochlear synapse maturation in mice. PLoS One 2014; 9:e94549. [PMID: 24804771 PMCID: PMC4012943 DOI: 10.1371/journal.pone.0094549] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 03/18/2014] [Indexed: 12/12/2022] Open
Abstract
Early cochlear development is marked by an exuberant outgrowth of neurites that innervate multiple targets. The establishment of mature cochlear neural circuits is, however, dependent on the pruning of inappropriate axons and synaptic connections. Such refinement also occurs in the central nervous system (CNS), and recently, genes ordinarily associated with immune and inflammatory processes have been shown to play roles in synaptic pruning in the brain. These molecules include the major histocompatibility complex class I (MHCI) genes, H2-Kb and H2-Db, and the complement cascade gene, C1qa. Since the mechanisms involved in synaptic refinement in the cochlea are not well understood, we investigated whether these immune system genes may be involved in this process and whether they are required for normal hearing function. Here we report that these genes are not necessary for normal synapse formation and refinement in the mouse cochlea. We further demonstrate that C1qa expression is not necessary for normal hearing in mice but the lack of expression of H2-Kb and H2-Db causes hearing impairment. These data underscore the importance of the highly polymorphic family of MHCI genes in hearing in mice and also suggest that factors and mechanisms regulating synaptic refinement in the cochlea may be distinct from those in the CNS.
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Affiliation(s)
- Melissa A. Calton
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Dasom Lee
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Srividya Sundaresan
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Diana Mendus
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Rose Leu
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Felix Wangsawihardja
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California, United States of America
| | | | - Mirna Mustapha
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California, United States of America
- * E-mail:
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Xia A, Song Y, Wang R, Gao SS, Clifton W, Raphael P, Chao SI, Pereira FA, Groves AK, Oghalai JS. Prestin regulation and function in residual outer hair cells after noise-induced hearing loss. PLoS One 2013; 8:e82602. [PMID: 24376553 PMCID: PMC3869702 DOI: 10.1371/journal.pone.0082602] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 10/25/2013] [Indexed: 12/27/2022] Open
Abstract
The outer hair cell (OHC) motor protein prestin is necessary for electromotility, which drives cochlear amplification and produces exquisitely sharp frequency tuning. TectaC1509G transgenic mice have hearing loss, and surprisingly have increased OHC prestin levels. We hypothesized, therefore, that prestin up-regulation may represent a generalized response to compensate for a state of hearing loss. In the present study, we sought to determine the effects of noise-induced hearing loss on prestin expression. After noise exposure, we performed cytocochleograms and observed OHC loss only in the basal region of the cochlea. Next, we patch clamped OHCs from the apical turn (9–12 kHz region), where no OHCs were lost, in noise-exposed and age-matched control mice. The non-linear capacitance was significantly higher in noise-exposed mice, consistent with higher functional prestin levels. We then measured prestin protein and mRNA levels in whole-cochlea specimens. Both Western blot and qPCR studies demonstrated increased prestin expression after noise exposure. Finally, we examined the effect of the prestin increase in vivo following noise damage. Immediately after noise exposure, ABR and DPOAE thresholds were elevated by 30–40 dB. While most of the temporary threshold shifts recovered within 3 days, there were additional improvements over the next month. However, DPOAE magnitudes, basilar membrane vibration, and CAP tuning curve measurements from the 9–12 kHz cochlear region demonstrated no differences between noise-exposed mice and control mice. Taken together, these data indicate that prestin is up-regulated by 32–58% in residual OHCs after noise exposure and that the prestin is functional. These findings are consistent with the notion that prestin increases in an attempt to partially compensate for reduced force production because of missing OHCs. However, in regions where there is no OHC loss, the cochlea is able to compensate for the excess prestin in order to maintain stable auditory thresholds and frequency discrimination.
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MESH Headings
- Animals
- Cochlear Microphonic Potentials
- Evoked Potentials, Auditory, Brain Stem
- Gene Expression Regulation
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/pathology
- Hearing Loss, Noise-Induced/metabolism
- Hearing Loss, Noise-Induced/pathology
- Hearing Loss, Noise-Induced/physiopathology
- Mice
- Models, Biological
- Molecular Motor Proteins/genetics
- Molecular Motor Proteins/metabolism
- Noise
- Otoacoustic Emissions, Spontaneous
- Patch-Clamp Techniques
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
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Affiliation(s)
- Anping Xia
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Yohan Song
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Rosalie Wang
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Simon S. Gao
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, Stanford, California, United States of America
- Department of Bioengineering, Rice University, Houston, Texas, United States of America
| | - Will Clifton
- Bobby R. Alford Department of Otolaryngology – Head and Neck Surgery, Baylor College of Medicine, Houston, Texas, United States of America
| | - Patrick Raphael
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Sung-il Chao
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, Stanford, California, United States of America
- Department of Otolaryngology–Head and Neck Surgery, Chosun University, Gwangju, South Korea
| | - Fred A. Pereira
- Bobby R. Alford Department of Otolaryngology – Head and Neck Surgery, Baylor College of Medicine, Houston, Texas, United States of America
| | - Andrew K. Groves
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - John S. Oghalai
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, Stanford, California, United States of America
- * E-mail:
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Probst FJ, Corrigan RR, del Gaudio D, Salinger AP, Lorenzo I, Gao SS, Chiu I, Xia A, Oghalai JS, Justice MJ. A point mutation in the gene for asparagine-linked glycosylation 10B (Alg10b) causes nonsyndromic hearing impairment in mice (Mus musculus). PLoS One 2013; 8:e80408. [PMID: 24303013 PMCID: PMC3841196 DOI: 10.1371/journal.pone.0080408] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 10/02/2013] [Indexed: 01/10/2023] Open
Abstract
The study of mouse hearing impairment mutants has led to the identification of a number of human hearing impairment genes and has greatly furthered our understanding of the physiology of hearing. The novel mouse mutant neurological/sensory 5 (nse5) demonstrates a significantly reduced or absent startle response to sound and is therefore a potential murine model of human hearing impairment. Genetic analysis of 500 intercross progeny localized the mutant locus to a 524 kilobase (kb) interval on mouse chromosome 15. A missense mutation in a highly-conserved amino acid was found in the asparagine-linked glycosylation 10B gene (Alg10b), which is within the critical interval for the nse5 mutation. A 20.4 kb transgene containing a wildtype copy of the Alg10b gene rescued the mutant phenotype in nse5/nse5 homozygous animals, confirming that the mutation in Alg10b is responsible for the nse5/nse5 mutant phenotype. Homozygous nse5/nse5 mutants had abnormal auditory brainstem responses (ABRs), distortion product otoacoustic emissions (DPOAEs), and cochlear microphonics (CMs). Endocochlear potentials (EPs), on the other hand, were normal. ABRs and DPOAEs also confirmed the rescue of the mutant nse5/nse5 phenotype by the wildtype Alg10b transgene. These results suggested a defect in the outer hair cells of mutant animals, which was confirmed by histologic analysis. This is the first report of mutation in a gene involved in the asparagine (N)-linked glycosylation pathway causing nonsyndromic hearing impairment, and it suggests that the hearing apparatus, and the outer hair cells in particular, are exquisitely sensitive to perturbations of the N-linked glycosylation pathway.
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Affiliation(s)
- Frank J. Probst
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Rebecca R. Corrigan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Daniela del Gaudio
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Andrew P. Salinger
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Isabel Lorenzo
- Genetically Engineered Mouse Shared Resource, Baylor College of Medicine, Houston, Texas, United States of America
| | - Simon S. Gao
- Department of Bioengineering, Rice University, Houston, Texas, United States of America
| | - Ilene Chiu
- Department of Otolaryngology-Head and Neck Surgery, Baylor College of Medicine, Houston, Texas, United States of America
| | - Anping Xia
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California, United States of America
| | - John S. Oghalai
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California, United States of America
| | - Monica J. Justice
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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20
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Gao SS, Raphael PD, Wang R, Park J, Xia A, Applegate BE, Oghalai JS. In vivo vibrometry inside the apex of the mouse cochlea using spectral domain optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2013. [PMID: 23411442 DOI: 10.1364/boe.4.000230] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Sound transduction within the auditory portion of the inner ear, the cochlea, is a complex nonlinear process. The study of cochlear mechanics in large rodents has provided important insights into cochlear function. However, technological and experimental limitations have restricted studies in mice due to their smaller cochlea. These challenges are important to overcome because of the wide variety of transgenic mouse strains with hearing loss mutations that are available for study. To accomplish this goal, we used spectral domain optical coherence tomography to visualize and measure sound-induced vibrations of intracochlear tissues. We present, to our knowledge, the first vibration measurements from the apex of an unopened mouse cochlea.
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Affiliation(s)
- Simon S Gao
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305, USA ; Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
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21
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Gao SS, Raphael PD, Wang R, Park J, Xia A, Applegate BE, Oghalai JS. In vivo vibrometry inside the apex of the mouse cochlea using spectral domain optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2013; 4:230-40. [PMID: 23411442 PMCID: PMC3567710 DOI: 10.1364/boe.4.00230] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 01/11/2013] [Accepted: 01/14/2013] [Indexed: 05/03/2023]
Abstract
Sound transduction within the auditory portion of the inner ear, the cochlea, is a complex nonlinear process. The study of cochlear mechanics in large rodents has provided important insights into cochlear function. However, technological and experimental limitations have restricted studies in mice due to their smaller cochlea. These challenges are important to overcome because of the wide variety of transgenic mouse strains with hearing loss mutations that are available for study. To accomplish this goal, we used spectral domain optical coherence tomography to visualize and measure sound-induced vibrations of intracochlear tissues. We present, to our knowledge, the first vibration measurements from the apex of an unopened mouse cochlea.
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Affiliation(s)
- Simon S. Gao
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305, USA
- Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Patrick D. Raphael
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305, USA
| | - Rosalie Wang
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305, USA
| | - Jesung Park
- Department of Biomedical Engineering, Texas A&M University, 337 Zachry Engineering Center, 3120 TAMU, College Station, TX 77843, USA
| | - Anping Xia
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305, USA
| | - Brian E. Applegate
- Department of Biomedical Engineering, Texas A&M University, 337 Zachry Engineering Center, 3120 TAMU, College Station, TX 77843, USA
| | - John S. Oghalai
- Department of Otolaryngology-Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305, USA
- Department of Bioengineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
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22
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Liu CC, Gao SS, Yuan T, Steele C, Puria S, Oghalai JS. Biophysical mechanisms underlying outer hair cell loss associated with a shortened tectorial membrane. J Assoc Res Otolaryngol 2011; 12:577-94. [PMID: 21567249 PMCID: PMC3173552 DOI: 10.1007/s10162-011-0269-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2011] [Accepted: 04/17/2011] [Indexed: 01/09/2023] Open
Abstract
The tectorial membrane (TM) connects to the stereociliary bundles of outer hair cells (OHCs). Humans with an autosomal dominant C1509G mutation in alpha-tectorin, a protein constituent of the TM, are born with a partial hearing loss that worsens over time. The Tecta(C1509/+) transgenic mouse with the same point mutation has partial hearing loss secondary to a shortened TM that only contacts the first row of OHCs. As well, Tecta(C1509G/+) mice have increased expression of the OHC electromotility protein, prestin. We sought to determine whether these changes impact OHC survival. Distortion product otoacoustic emission thresholds in a quiet environment did not change to 6 months of age. However, noise exposure produced acute threshold shifts that fully recovered in Tecta (+/+) mice but only partially recovered in Tecta(C1509G/+) mice. While Tecta(+/+) mice lost OHCs primarily at the base and within all three rows, Tecta(C1509G/+) mice lost most of their OHCs in a more apical region of the cochlea and nearly completely within the first row. In order to estimate the impact of a shorter TM on the forces faced by the stereocilia within the first OHC row, both the wild type and the heterozygous conditions were simulated in a computational model. These analyses predicted that the shear force on the stereocilia is ~50% higher in the heterozygous condition. We then measured electrically induced movements of the reticular lamina in situ and found that while they decreased to the noise floor in prestin null mice, they were increased by 4.58 dB in Tecta(C1509G/+) mice compared to Tecta(+/+) mice. The increased movements were associated with a fourfold increase in OHC death as measured by vital dye staining. Together, these findings indicate that uncoupling the TM from some OHCs leads to partial hearing loss and places the remaining coupled OHCs at higher risk. Both the mechanics of the malformed TM and the increased prestin-related movements of the organ of Corti contribute to this higher risk profile.
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Affiliation(s)
- Christopher C. Liu
- The Bobby R. Alford Department of Otolaryngology–Head and Neck Surgery, Baylor College of Medicine, Houston, TX 77030 USA
| | - Simon S. Gao
- Department of Bioengineering, Rice University, Houston, TX 77005 USA
| | - Tao Yuan
- The Bobby R. Alford Department of Otolaryngology–Head and Neck Surgery, Baylor College of Medicine, Houston, TX 77030 USA
| | - Charles Steele
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94304-5739 USA
| | - Sunil Puria
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94304-5739 USA
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305-5739 USA
| | - John S. Oghalai
- Department of Bioengineering, Rice University, Houston, TX 77005 USA
- Department of Otolaryngology–Head and Neck Surgery, Stanford University, 801 Welch Road, Stanford, CA 94305-5739 USA
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23
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Jahan I, Pan N, Kersigo J, Fritzsch B. Neurod1 suppresses hair cell differentiation in ear ganglia and regulates hair cell subtype development in the cochlea. PLoS One 2010; 5:e11661. [PMID: 20661473 PMCID: PMC2908541 DOI: 10.1371/journal.pone.0011661] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Accepted: 06/23/2010] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND At least five bHLH genes regulate cell fate determination and differentiation of sensory neurons, hair cells and supporting cells in the mammalian inner ear. Cross-regulation of Atoh1 and Neurog1 results in hair cell changes in Neurog1 null mice although the nature and mechanism of the cross-regulation has not yet been determined. Neurod1, regulated by both Neurog1 and Atoh1, could be the mediator of this cross-regulation. METHODOLOGY/PRINCIPAL FINDINGS We used Tg(Pax2-Cre) to conditionally delete Neurod1 in the inner ear. Our data demonstrate for the first time that the absence of Neurod1 results in formation of hair cells within the inner ear sensory ganglia. Three cell types, neural crest derived Schwann cells and mesenchyme derived fibroblasts (neither expresses Neurod1) and inner ear derived neurons (which express Neurod1) constitute inner ear ganglia. The most parsimonious explanation is that Neurod1 suppresses the alternative fate of sensory neurons to develop as hair cells. In the absence of Neurod1, Atoh1 is expressed and differentiates cells within the ganglion into hair cells. We followed up on this effect in ganglia by demonstrating that Neurod1 also regulates differentiation of subtypes of hair cells in the organ of Corti. We show that in Neurod1 conditional null mice there is a premature expression of several genes in the apex of the developing cochlea and outer hair cells are transformed into inner hair cells. CONCLUSIONS/SIGNIFICANCE Our data suggest that the long noted cross-regulation of Atoh1 expression by Neurog1 might actually be mediated in large part by Neurod1. We suggest that Neurod1 is regulated by both Neurog1 and Atoh1 and provides a negative feedback for either gene. Through this and other feedback, Neurod1 suppresses alternate fates of neurons to differentiate as hair cells and regulates hair cell subtypes.
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Affiliation(s)
- Israt Jahan
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Ning Pan
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Jennifer Kersigo
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
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24
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Jahan I, Kersigo J, Pan N, Fritzsch B. Neurod1 regulates survival and formation of connections in mouse ear and brain. Cell Tissue Res 2010; 341:95-110. [PMID: 20512592 DOI: 10.1007/s00441-010-0984-6] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 04/15/2010] [Indexed: 12/11/2022]
Abstract
The developing sensory neurons of the mammalian ear require two sequentially activated bHLH genes, Neurog1 and Neurod1, for their development. Neurons never develop in Neurog1 null mice, and most neurons die in Neurod1 null mutants, a gene upregulated by Neurog1. The surviving neurons of Neurod1 null mice are incompletely characterized in postnatal mice because of the early lethality of mutants and the possible compromising effect of the absence of insulin on peripheral neuropathies. Using Tg(Pax2-cre), we have generated a conditional deletion of floxed Neurod1 for the ear; this mouse is viable and allows us to investigate ear innervation defects of Neurod1 absence only in the ear. We have compared the defects in embryos and show an ear phenotype in conditional Neurod1 null mice comparable with the systemic Neurod1 null mouse. By studying postnatal animals, we show that Neurod1 not only is necessary for the survival of most spiral and many vestibular neurons, but is also essential for a segregated central projection of vestibular and cochlear afferents. In the absence of Neurod1 in the ear, vestibular and cochlear afferents enter the cochlear nucleus as a single mixed nerve. Neurites coming from vestibular and cochlear sensory epithelia project centrally to both cochlear and vestibular nuclei, in addition to their designated target projections. The peripheral innervation of the remaining sensory neurons is disorganized and shows collaterals of single neurons projecting to multiple endorgans, displaying no tonotopic organization of the organ of Corti or the cochlear nucleus. Pending elucidation of the molecular details for these Neurod1 functions, these data demonstrate that Neurod1 is not only a major factor for the survival of neurons but is crucial for the development of normal ear connections, both in the ear and in the central nervous system.
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Affiliation(s)
- Israt Jahan
- Department of Biology, College of Liberal Arts and Sciences, University of Iowa, Iowa City, IA 52242, USA
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Xia A, Gao SS, Yuan T, Osborn A, Bress A, Pfister M, Maricich SM, Pereira FA, Oghalai JS. Deficient forward transduction and enhanced reverse transduction in the alpha tectorin C1509G human hearing loss mutation. Dis Model Mech 2010; 3:209-23. [PMID: 20142329 DOI: 10.1242/dmm.004135] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Most forms of hearing loss are associated with loss of cochlear outer hair cells (OHCs). OHCs require the tectorial membrane (TM) for stereociliary bundle stimulation (forward transduction) and active feedback (reverse transduction). Alpha tectorin is a protein constituent of the TM and the C1509G mutation in alpha tectorin in humans results in autosomal dominant hearing loss. We engineered and validated this mutation in mice and found that the TM was shortened in heterozygous Tecta(C1509G/+) mice, reaching only the first row of OHCs. Thus, deficient forward transduction renders OHCs within the second and third rows non-functional, producing partial hearing loss. Surprisingly, both Tecta(C1509G/+) and Tecta(C1509G/C1509G) mice were found to have increased reverse transduction as assessed by sound- and electrically-evoked otoacoustic emissions. We show that an increase in prestin, a protein necessary for electromotility, in all three rows of OHCs underlies this phenomenon. This mouse model demonstrates a human hearing loss mutation in which OHC function is altered through a non-cell-autonomous variation in prestin.
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Affiliation(s)
- Anping Xia
- The Bobby R. Alford Department of Otolaryngology - Head and Neck Surgery, Baylor College of Medicine, Houston, TX 77030, USA
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Yuan T, Gao SS, Saggau P, Oghalai JS. Calcium imaging of inner ear hair cells within the cochlear epithelium of mice using two-photon microscopy. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:016002. [PMID: 20210449 PMCID: PMC2821419 DOI: 10.1117/1.3290799] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 11/03/2009] [Accepted: 11/09/2009] [Indexed: 05/28/2023]
Abstract
Mice are an excellent model for studying mammalian hearing and transgenic mouse models of human hearing, loss are commonly available. However, the mouse cochlea is substantially smaller than other animal models routinely used to study cochlear physiology. This makes study of their hair cells difficult. We develop a novel methodology to optically image calcium within living hair cells left undisturbed within the excised mouse cochlea. Fresh cochleae are harvested, left intact within their otic capsule bone, and fixed in a recording chamber. The bone overlying the cochlear epithelium is opened and Reissner's membrane is incised. A fluorescent calcium indicator is applied to the preparation. A custom-built upright two-photon microscope was used to image the preparation using 3-D scanning. We are able to image about one third of a cochlear turn simultaneously, in either the apical or basal regions. Within one hour of animal sacrifice, we find that outer hair cells demonstrate increased fluorescence compared with surrounding supporting cells. This methodology is then used to visualize hair cell calcium changes during mechanotransduction over a region of the epithelium. Because the epithelium is left within the cochlea, dissection trauma is minimized and artifactual changes in hair cell physiology are expected to be reduced.
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Affiliation(s)
- Tao Yuan
- Baylor College of Medicine, The Bobby R. Alford Department of Otolaryngology, Head and Neck Surgery, Houston, Texas 77030, USA
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Atoh1-lineal neurons are required for hearing and for the survival of neurons in the spiral ganglion and brainstem accessory auditory nuclei. J Neurosci 2009; 29:11123-33. [PMID: 19741118 DOI: 10.1523/jneurosci.2232-09.2009] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Atoh1 is a basic helix-loop-helix transcription factor necessary for the specification of inner ear hair cells and central auditory system neurons derived from the rhombic lip. We used the Cre-loxP system and two Cre-driver lines (Egr2(Cre) and Hoxb1(Cre)) to delete Atoh1 from different regions of the cochlear nucleus (CN) and accessory auditory nuclei (AAN). Adult Atoh1-conditional knock-out mice (Atoh1(CKO)) are behaviorally deaf, have diminished auditory brainstem evoked responses, and have disrupted CN and AAN morphology and connectivity. In addition, Egr2; Atoh1(CKO) mice lose spiral ganglion neurons in the cochlea and AAN neurons during the first 3 d of life, revealing a novel critical period in the development of these neurons. These new mouse models of predominantly central deafness illuminate the importance of the CN for support of a subset of peripheral and central auditory neurons.
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Abstract
OBJECTIVES/HYPOTHESIS The cochlear amplifier is required for the exquisite sensitivity of mammalian hearing. Outer hair cells underlie the cochlear amplifier and they are unique in that they maintain an intracellular turgor pressure. Changing the turgor pressure of an isolated outer hair cells through osmotic challenge modulates its ability to produce electromotile force. We sought to determine the effect of osmotic challenge on cochlear function. STUDY DESIGN In vivo animal study. METHODS Hypotonic and hypertonic artificial perilymph was perfused through the scala tympani of anesthetized guinea pigs. Cochlear function was assessed by measuring the compound action potential, distortion product otoacoustic emissions, the cochlear microphonic, and the endocochlear potential. RESULTS Hypotonic perilymph decreased and hypertonic perilymph increased compound action potential and distortion product otoacoustic emission thresholds in a dose-dependent and reversible manner. The cochlear microphonic quadratic distortion product magnitude increased after hypotonic perfusion and decreased with hypertonic perfusion. There were no changes in the stimulus intensity growth curve of the low-frequency cochlear microphonic. The endocochlear potential was not affected by perilymph osmolality. CONCLUSIONS These data demonstrate that perilymph osmolality can modulate cochlear function and are consistent with what would be expected if outer hair cells turgor pressure changes the gain of the cochlear amplifier in vivo.
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