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Domínguez-Ruiz M, Murillo-Cuesta S, Contreras J, Cantero M, Garrido G, Martín-Bernardo B, Gómez-Rosas E, Fernández A, Del Castillo FJ, Montoliu L, Varela-Nieto I, Del Castillo I. A murine model for the del(GJB6-D13S1830) deletion recapitulating the phenotype of human DFNB1 hearing impairment: generation and functional and histopathological study. BMC Genomics 2024; 25:359. [PMID: 38605287 PMCID: PMC11007912 DOI: 10.1186/s12864-024-10289-z] [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: 02/06/2024] [Accepted: 04/07/2024] [Indexed: 04/13/2024] Open
Abstract
Inherited hearing impairment is a remarkably heterogeneous monogenic condition, involving hundreds of genes, most of them with very small (< 1%) epidemiological contributions. The exception is GJB2, the gene encoding connexin-26 and underlying DFNB1, which is the most frequent type of autosomal recessive non-syndromic hearing impairment (ARNSHI) in most populations (up to 40% of ARNSHI cases). DFNB1 is caused by different types of pathogenic variants in GJB2, but also by large deletions that keep the gene intact but remove an upstream regulatory element that is essential for its expression. Such large deletions, found in most populations, behave as complete loss-of-function variants, usually associated with a profound hearing impairment. By using CRISPR-Cas9 genetic edition, we have generated a murine model (Dfnb1em274) that reproduces the most frequent of those deletions, del(GJB6-D13S1830). Dfnb1em274 homozygous mice are viable, bypassing the embryonic lethality of the Gjb2 knockout, and present a phenotype of profound hearing loss (> 90 dB SPL) that correlates with specific structural abnormalities in the cochlea. We show that Gjb2 expression is nearly abolished and its protein product, Cx26, is nearly absent all throughout the cochlea, unlike previous conditional knockouts in which Gjb2 ablation was not obtained in all cell types. The Dfnb1em274 model recapitulates the clinical presentation of patients harbouring the del(GJB6-D13S1830) variant and thus it is a valuable tool to study the pathological mechanisms of DFNB1 and to assay therapies for this most frequent type of human ARNSHI.
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Affiliation(s)
- María Domínguez-Ruiz
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Silvia Murillo-Cuesta
- Institute for Biomedical Research "Sols-Morreale", Spanish National Research Council-Autonomous University of Madrid, Madrid, Spain
- Hospital La Paz Institute for Health Research (IdiPAZ), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Julio Contreras
- Institute for Biomedical Research "Sols-Morreale", Spanish National Research Council-Autonomous University of Madrid, Madrid, Spain
- Anatomy and Embryology Department, Faculty of Veterinary, Universidad Complutense de Madrid, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Marta Cantero
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Gema Garrido
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Belén Martín-Bernardo
- Institute for Biomedical Research "Sols-Morreale", Spanish National Research Council-Autonomous University of Madrid, Madrid, Spain
- Hospital La Paz Institute for Health Research (IdiPAZ), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Elena Gómez-Rosas
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
| | - Almudena Fernández
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Francisco J Del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Lluís Montoliu
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Isabel Varela-Nieto
- Institute for Biomedical Research "Sols-Morreale", Spanish National Research Council-Autonomous University of Madrid, Madrid, Spain
- Hospital La Paz Institute for Health Research (IdiPAZ), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain
| | - Ignacio Del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain.
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER-ISCIII), Madrid, Spain.
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2
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Badaoui M, Chanson M. Intercellular Communication in Airway Epithelial Cell Regeneration: Potential Roles of Connexins and Pannexins. Int J Mol Sci 2023; 24:16160. [PMID: 38003349 PMCID: PMC10671439 DOI: 10.3390/ijms242216160] [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: 09/26/2023] [Revised: 10/19/2023] [Accepted: 11/08/2023] [Indexed: 11/26/2023] Open
Abstract
Connexins and pannexins are transmembrane proteins that can form direct (gap junctions) or indirect (connexons, pannexons) intercellular communication channels. By propagating ions, metabolites, sugars, nucleotides, miRNAs, and/or second messengers, they participate in a variety of physiological functions, such as tissue homeostasis and host defense. There is solid evidence supporting a role for intercellular signaling in various pulmonary inflammatory diseases where alteration of connexin/pannexin channel functional expression occurs, thus leading to abnormal intercellular communication pathways and contributing to pathophysiological aspects, such as innate immune defense and remodeling. The integrity of the airway epithelium, which is the first line of defense against invading microbes, is established and maintained by a repair mechanism that involves processes such as proliferation, migration, and differentiation. Here, we briefly summarize current knowledge on the contribution of connexins and pannexins to necessary processes of tissue repair and speculate on their possible involvement in the shaping of the airway epithelium integrity.
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Affiliation(s)
| | - Marc Chanson
- Department of Cell Physiology & Metabolism, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland;
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Hool SA, Jeng J, Jagger DJ, Marcotti W, Ceriani F. Age-related changes in P2Y receptor signalling in mouse cochlear supporting cells. J Physiol 2023; 601:4375-4395. [PMID: 37715703 PMCID: PMC10952729 DOI: 10.1113/jp284980] [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: 05/04/2023] [Accepted: 08/16/2023] [Indexed: 09/18/2023] Open
Abstract
Our sense of hearing depends on the function of a specialised class of sensory cells, the hair cells, which are found in the organ of Corti of the mammalian cochlea. The unique physiological environment in which these cells operate is maintained by a syncitium of non-sensory supporting cells, which are crucial for regulating cochlear physiology and metabolic homeostasis. Despite their importance for cochlear function, the role of these supporting cells in age-related hearing loss, the most common sensory deficit in the elderly, is poorly understood. Here, we investigated the age-related changes in the expression and function of metabotropic purinergic receptors (P2Y1 , P2Y2 and P2Y4 ) in the supporting cells of the cochlear apical coil. Purinergic signalling in supporting cells is crucial during the development of the organ of Corti and purinergic receptors are known to undergo changes in expression during ageing in several tissues. Immunolabelling and Ca2+ imaging experiments revealed a downregulation of P2Y receptor expression and a decrease of purinergic-mediated calcium responses after early postnatal stages in the supporting cells. An upregulation of P2Y receptor expression was observed in the aged cochlea when compared to 1 month-old adults. The aged mice also had significantly larger calcium responses and displayed calcium oscillations during prolonged agonist applications. We conclude that supporting cells in the aged cochlea upregulate P2Y2 and P2Y4 receptors and display purinergic-induced Ca2+ responses that mimic those observed during pre-hearing stages of development, possibly aimed at limiting or preventing further damage to the sensory epithelium. KEY POINTS: Age-related hearing loss is associated with lower hearing sensitivity and decreased ability to understand speech. We investigated age-related changes in the expression and function of metabotropic purinergic (P2Y) receptors in cochlear non-sensory supporting cells of mice displaying early-onset (C57BL/6N) and late-onset (C3H/HeJ) hearing loss. The expression of P2Y1 , P2Y2 and P2Y4 receptors in the supporting cells decreased during cochlear maturation, but that of P2Y2 and P2Y4 was upregulated in the aged cochlea. P2Y2 and P2Y4 receptors were primarily responsible for the ATP-induced Ca2+ responses in the supporting cells. The degree of purinergic expression upregulation in aged supporting cells mirrored hearing loss progression in the different mouse strains. We propose that the upregulation of purinergic-mediated signalling in the aged cochlea is subsequent to age-related changes in the hair cells and may act as a protective mechanism to limit or to avoid further damage to the sensory epithelium.
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Affiliation(s)
- Sarah A. Hool
- School of BiosciencesUniversity of SheffieldSheffieldUK
| | - Jing‐Yi Jeng
- School of BiosciencesUniversity of SheffieldSheffieldUK
| | | | - Walter Marcotti
- School of BiosciencesUniversity of SheffieldSheffieldUK
- Neuroscience InstituteUniversity of SheffieldSheffieldUK
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4
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Kersbergen CJ, Babola TA, Kanold PO, Bergles DE. Preservation of developmental spontaneous activity enables early auditory system maturation in deaf mice. PLoS Biol 2023; 21:e3002160. [PMID: 37368868 PMCID: PMC10298803 DOI: 10.1371/journal.pbio.3002160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 05/11/2023] [Indexed: 06/29/2023] Open
Abstract
Intrinsically generated neural activity propagates through the developing auditory system to promote maturation and refinement of sound processing circuits prior to hearing onset. This early patterned activity is induced by non-sensory supporting cells in the organ of Corti, which are highly interconnected through gap junctions containing connexin 26 (Gjb2). Although loss of function mutations in Gjb2 impair cochlear development and are the most common cause of congenital deafness, it is not known if these variants disrupt spontaneous activity and the developmental trajectory of sound processing circuits in the brain. Here, we show in a new mouse model of Gjb2-mediated congenital deafness that cochlear supporting cells adjacent to inner hair cells (IHCs) unexpectedly retain intercellular coupling and the capacity to generate spontaneous activity, exhibiting only modest deficits prior to hearing onset. Supporting cells lacking Gjb2 elicited coordinated activation of IHCs, leading to coincident bursts of activity in central auditory neurons that will later process similar frequencies of sound. Despite alterations in the structure of the sensory epithelium, hair cells within the cochlea of Gjb2-deficient mice were intact and central auditory neurons could be activated within appropriate tonotopic domains by loud sounds at hearing onset, indicating that early maturation and refinement of auditory circuits was preserved. Only after cessation of spontaneous activity following hearing onset did progressive hair cell degeneration and enhanced auditory neuron excitability manifest. This preservation of cochlear spontaneous neural activity in the absence of connexin 26 may increase the effectiveness of early therapeutic interventions to restore hearing.
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Affiliation(s)
- Calvin J. Kersbergen
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Travis A. Babola
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Patrick O. Kanold
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Dwight E. Bergles
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Otolaryngology Head and Neck Surgery, Johns Hopkins University, Baltimore, Maryland, United States of America
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
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5
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Li Q, Cui C, Liao R, Yin X, Wang D, Cheng Y, Huang B, Wang L, Yan M, Zhou J, Zhao J, Tang W, Wang Y, Wang X, Lv J, Li J, Li H, Shu Y. The pathogenesis of common Gjb2 mutations associated with human hereditary deafness in mice. Cell Mol Life Sci 2023; 80:148. [PMID: 37178259 PMCID: PMC10182940 DOI: 10.1007/s00018-023-04794-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 03/31/2023] [Accepted: 04/28/2023] [Indexed: 05/15/2023]
Abstract
Mutations in GJB2 (Gap junction protein beta 2) are the most common genetic cause of non-syndromic hereditary deafness in humans, especially the 35delG and 235delC mutations. Owing to the homozygous lethality of Gjb2 mutations in mice, there are currently no perfect mouse models carrying Gjb2 mutations derived from patients for mimicking human hereditary deafness and for unveiling the pathogenesis of the disease. Here, we successfully constructed heterozygous Gjb2+/35delG and Gjb2+/235delC mutant mice through advanced androgenic haploid embryonic stem cell (AG-haESC)-mediated semi-cloning technology, and these mice showed normal hearing at postnatal day (P) 28. A homozygous mutant mouse model, Gjb235delG/35delG, was then generated using enhanced tetraploid embryo complementation, demonstrating that GJB2 plays an indispensable role in mouse placenta development. These mice exhibited profound hearing loss similar to human patients at P14, i.e., soon after the onset of hearing. Mechanistic analyses showed that Gjb2 35delG disrupts the function and formation of intercellular gap junction channels of the cochlea rather than affecting the survival and function of hair cells. Collectively, our study provides ideal mouse models for understanding the pathogenic mechanism of DFNB1A-related hereditary deafness and opens up a new avenue for investigating the treatment of this disease.
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Affiliation(s)
- Qing Li
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China.
| | - Chong Cui
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Rongyu Liao
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Xidi Yin
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Daqi Wang
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Yanbo Cheng
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Bowei Huang
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Liqin Wang
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Meng Yan
- School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, China
| | - Jinan Zhou
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Jingjing Zhao
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Wei Tang
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Yingyi Wang
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | | | - Jun Lv
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China
| | - Jinsong Li
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
- School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, China
| | - Huawei Li
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China.
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China.
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China.
| | - Yilai Shu
- ENT Institute and Department of Otorhinolaryngology, Eye and ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China.
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China.
- NHC Key Laboratory of Hearing Medicine, Fudan University, Shanghai, China.
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6
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Defourny J, Thiry M. Recent insights into gap junction biogenesis in the cochlea. Dev Dyn 2023; 252:239-246. [PMID: 36106826 DOI: 10.1002/dvdy.538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 09/08/2022] [Accepted: 09/11/2022] [Indexed: 11/06/2022] Open
Abstract
In the cochlea, connexin 26 (Cx26) and connexin 30 (Cx30) co-assemble into two types of homomeric and heteromeric gap junctions between adjacent non-sensory epithelial cells. These channels provide a mechanical coupling between connected cells, and their activity is critical to maintain cochlear homeostasis. Many of the mutations in GJB2 or GJB6, which encode Cx26 and Cx30 in humans, impair the formation of membrane channels and cause autosomal syndromic and non-syndromic hearing loss. Thus, deciphering the connexin trafficking pathways in situ should represent a major step forward in understanding the pathogenic significance of many of these mutations. A growing body of evidence now suggests that Cx26/Cx30 heteromeric and Cx30 homomeric channels display distinct assembly mechanisms. Here, we review the most recent advances that have been made toward unraveling the biogenesis and stability of these gap junctions in the cochlea.
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Affiliation(s)
- Jean Defourny
- GIGA-Neurosciences, Unit of Cell and Tissue Biology, University of Liège, Liège, Belgium
| | - Marc Thiry
- GIGA-Neurosciences, Unit of Cell and Tissue Biology, University of Liège, Liège, Belgium
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7
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Abbott AC, García IE, Villanelo F, Flores-Muñoz C, Ceriani R, Maripillán J, Novoa-Molina J, Figueroa-Cares C, Pérez-Acle T, Sáez JC, Sánchez HA, Martínez AD. Expression of KID syndromic mutation Cx26S17F produces hyperactive hemichannels in supporting cells of the organ of Corti. Front Cell Dev Biol 2023; 10:1071202. [PMID: 36699003 PMCID: PMC9868548 DOI: 10.3389/fcell.2022.1071202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Accepted: 12/15/2022] [Indexed: 01/11/2023] Open
Abstract
Some mutations in gap junction protein Connexin 26 (Cx26) lead to syndromic deafness, where hearing impairment is associated with skin disease, like in Keratitis Ichthyosis Deafness (KID) syndrome. This condition has been linked to hyperactivity of connexin hemichannels but this has never been demonstrated in cochlear tissue. Moreover, some KID mutants, like Cx26S17F, form hyperactive HCs only when co-expressed with other wild-type connexins. In this work, we evaluated the functional consequences of expressing a KID syndromic mutation, Cx26S17F, in the transgenic mouse cochlea and whether co-expression of Cx26S17F and Cx30 leads to the formation of hyperactive HCs. Indeed, we found that cochlear explants from a constitutive knock-in Cx26S17F mouse or conditional in vitro cochlear expression of Cx26S17F produces hyperactive HCs in supporting cells of the organ of Corti. These conditions also produce loss of hair cells stereocilia. In supporting cells, we found high co-localization between Cx26S17F and Cx30. The functional properties of HCs formed in cells co-expressing Cx26S17F and Cx30 were also studied in oocytes and HeLa cells. Under the recording conditions used in this study Cx26S17F did not form functional HCs and GJCs, but cells co-expressing Cx26S17F and Cx30 present hyperactive HCs insensitive to HCs blockers, Ca2+ and La3+, resulting in more Ca2+ influx and cellular damage. Molecular dynamic analysis of putative heteromeric HC formed by Cx26S17F and Cx30 presents alterations in extracellular Ca2+ binding sites. These results support that in KID syndrome, hyperactive HCs are formed by the interaction between Cx26S17F and Cx30 in supporting cells probably causing damage to hair cells associated to deafness.
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Affiliation(s)
- Ana C. Abbott
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile,Facultad de Medicina Veterinaria y Agronomía, Instituto de Ciencias Naturales, Universidad de las Américas, Viña del Mar, Chile
| | - Isaac E. García
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile,Laboratorio de Fisiología Molecular y Biofísica, Facultad de Odontología, Universidad de Valparaíso, Valparaíso, Chile,Centro de Investigaciones en Ciencias Odontológicas y Médicas, CICOM, Universidad de Valparaíso, Valparaíso, Chile
| | - Felipe Villanelo
- Facultad de Ingeniería, Arquitectura y Diseño, Universidad San Sebastián, Santiago, Chile,Computational Biology Lab, Centro Basal Ciencia & Vida, Universidad San Sebastián, Santiago, Chile
| | - Carolina Flores-Muñoz
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Ricardo Ceriani
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile,Escuela de Química y Farmacia, Facultad de Farmacia, Universidad de Valparaíso, Valparaíso, Chile
| | - Jaime Maripillán
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Joel Novoa-Molina
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Cindel Figueroa-Cares
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Tomas Pérez-Acle
- Facultad de Ingeniería, Arquitectura y Diseño, Universidad San Sebastián, Santiago, Chile,Computational Biology Lab, Centro Basal Ciencia & Vida, Universidad San Sebastián, Santiago, Chile
| | - Juan C. Sáez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Helmuth A. Sánchez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile,*Correspondence: Helmuth A. Sánchez, ; Agustín D. Martínez,
| | - Agustín D. Martínez
- Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile,*Correspondence: Helmuth A. Sánchez, ; Agustín D. Martínez,
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8
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Chen P, Wu W, Zhang J, Chen J, Li Y, Sun L, Hou S, Yang J. Pathological mechanisms of connexin26-related hearing loss: Potassium recycling, ATP-calcium signaling, or energy supply? Front Mol Neurosci 2022; 15:976388. [PMID: 36187349 PMCID: PMC9520402 DOI: 10.3389/fnmol.2022.976388] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 08/11/2022] [Indexed: 11/17/2022] Open
Abstract
Hereditary deafness is one of the most common human birth defects. GJB2 gene mutation is the most genetic etiology. Gap junction protein 26 (connexin26, Cx26) encoded by the GJB2 gene, which is responsible for intercellular substance transfer and signal communication, plays a critical role in hearing acquisition and maintenance. The auditory character of different Connexin26 transgenic mice models can be classified into two types: profound congenital deafness and late-onset progressive hearing loss. Recent studies demonstrated that there are pathological changes including endocochlear potential reduction, active cochlear amplification impairment, cochlear developmental disorders, and so on, in connexin26 deficiency mice. Here, this review summarizes three main hypotheses to explain pathological mechanisms of connexin26-related hearing loss: potassium recycling disruption, adenosine-triphosphate-calcium signaling propagation disruption, and energy supply dysfunction. Elucidating pathological mechanisms underlying connexin26-related hearing loss can help develop new protective and therapeutic strategies for this common deafness. It is worthy of further study on the detailed cellular and molecular upstream mechanisms to modify connexin (channel) function.
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Affiliation(s)
- Penghui Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Wenjin Wu
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Jifang Zhang
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Junmin Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Yue Li
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Lianhua Sun
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Shule Hou
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
- *Correspondence: Shule Hou,
| | - Jun Yang
- Department of Otorhinolaryngology-Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
- Jun Yang,
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9
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Paciello F, Zorzi V, Raspa M, Scavizzi F, Grassi C, Mammano F, Fetoni AR. Connexin 30 deletion exacerbates cochlear senescence and age-related hearing loss. Front Cell Dev Biol 2022; 10:950837. [PMID: 36016655 PMCID: PMC9395607 DOI: 10.3389/fcell.2022.950837] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 07/11/2022] [Indexed: 11/13/2022] Open
Abstract
Pathogenic mutations in the Gjb2 and Gjb6 genes, encoding connexin 26 (Cx26) and connexin 30 (Cx30), respectively, have been linked to the most frequent monogenic hearing impairment, nonsyndromic hearing loss, and deafness DFNB1. It is known that Cx26 plays an important role in auditory development, while the role of Cx30 in hearing remains controversial. Previous studies found that partial deletion of Cx26 can accelerate age-related hearing loss (ARHL), a multifactorial complex disorder, with both environmental and genetic factors contributing to the etiology of the disease. Here, we investigated the role of Cx30 in cochlear-aging processes using a transgenic mouse model with total deletion of Cx30 (Cx30 ΔΔ mice), in which Cx30 was removed without perturbing the surrounding sequences. We show that these mice are affected by exacerbated ARHL, with increased morphological cochlear damage, oxidative stress, inflammation, and vascular dysfunctions. Overall, our data demonstrate that Cx30 deletion can be considered a genetic risk factor for ARHL, making cochlear structures more susceptible to aging processes.
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Affiliation(s)
- Fabiola Paciello
- Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Veronica Zorzi
- CNR Institute of Biochemistry and Cell Biology, Monterotondo (RM), Italy
| | - Marcello Raspa
- CNR Institute of Biochemistry and Cell Biology, Monterotondo (RM), Italy
| | | | - Claudio Grassi
- Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | - Fabio Mammano
- CNR Institute of Biochemistry and Cell Biology, Monterotondo (RM), Italy
- Department of Physics and Astronomy, University of Padova, Padova, Italy
- *Correspondence: Fabio Mammano, ; Anna Rita Fetoni,
| | - Anna Rita Fetoni
- Department of Otolaryngology Head and Neck Surgery, Università Cattolica del Sacro Cuore, Rome, Italy
- Unit of Audiology, Department of Neuroscience, Reproductive Sciences and Dentistry, University of Naples Federico II, Naples, Italy
- *Correspondence: Fabio Mammano, ; Anna Rita Fetoni,
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10
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Cibelli A, Stout R, Timmermann A, de Menezes L, Guo P, Maass K, Seifert G, Steinhäuser C, Spray DC, Scemes E. Cx43 carboxyl terminal domain determines AQP4 and Cx30 endfoot organization and blood brain barrier permeability. Sci Rep 2021; 11:24334. [PMID: 34934080 PMCID: PMC8692511 DOI: 10.1038/s41598-021-03694-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 12/06/2021] [Indexed: 11/08/2022] Open
Abstract
The neurovascular unit (NVU) consists of cells intrinsic to the vessel wall, the endothelial cells and pericytes, and astrocyte endfeet that surround the vessel but are separated from it by basement membrane. Endothelial cells are primarily responsible for creating and maintaining blood-brain-barrier (BBB) tightness, but astrocytes contribute to the barrier through paracrine signaling to the endothelial cells and by forming the glia limitans. Gap junctions (GJs) between astrocyte endfeet are composed of connexin 43 (Cx43) and Cx30, which form plaques between cells. GJ plaques formed of Cx43 do not diffuse laterally in the plasma membrane and thus potentially provide stable organizational features to the endfoot domain, whereas GJ plaques formed of other connexins and of Cx43 lacking a large portion of its cytoplasmic carboxyl terminus are quite mobile. In order to examine the organizational features that immobile GJs impose on the endfoot, we have used super-resolution confocal microscopy to map number and sizes of GJ plaques and aquaporin (AQP)-4 channel clusters in the perivascular endfeet of mice in which astrocyte GJs (Cx30, Cx43) were deleted or the carboxyl terminus of Cx43 was truncated. To determine if BBB integrity was compromised in these transgenic mice, we conducted perfusion studies under elevated hydrostatic pressure using horseradish peroxide as a molecular probe enabling detection of micro-hemorrhages in brain sections. These studies revealed that microhemorrhages were more numerous in mice lacking Cx43 or its carboxyl terminus. In perivascular domains of cerebral vessels, we found that density of Cx43 GJs was higher in the truncation mutant, while GJ size was smaller. Density of perivascular particles formed by AQP4 and its extended isoform AQP4ex was inversely related to the presence of full length Cx43, whereas the ratio of sizes of the particles of the AQP4ex isoform to total AQP4 was directly related to the presence of full length Cx43. Confocal analysis showed that Cx43 and Cx30 were substantially colocalized in astrocyte domains near vasculature of truncation mutant mice. These results showing altered distribution of some astrocyte nexus components (AQP4 and Cx30) in Cx43 null mice and in a truncation mutant, together with leakier cerebral vasculature, support the hypothesis that localization and mobility of gap junction proteins and their binding partners influences organization of astrocyte endfeet which in turn impacts BBB integrity of the NVU.
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Affiliation(s)
- Antonio Cibelli
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Randy Stout
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
- New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, USA
| | - Aline Timmermann
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Laura de Menezes
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY, USA
- Insitute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Peng Guo
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY, USA
- Cellular Imaging Core Facility, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Karen Maass
- Cardiovascular Research Center, NYU Grossman School of Medicine, New York, NY, USA
| | - Gerald Seifert
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - Christian Steinhäuser
- Institute of Cellular Neurosciences, Medical Faculty, University of Bonn, Bonn, Germany
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY, USA.
| | - Eliana Scemes
- Department of Anatomy and Cell Biology, New York Medical College, Valhalla, NY, 10595, USA.
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11
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Zehnder T, Petrelli F, Romanos J, De Oliveira Figueiredo EC, Lewis TL, Déglon N, Polleux F, Santello M, Bezzi P. Mitochondrial biogenesis in developing astrocytes regulates astrocyte maturation and synapse formation. Cell Rep 2021; 35:108952. [PMID: 33852851 DOI: 10.1016/j.celrep.2021.108952] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 01/10/2021] [Accepted: 03/15/2021] [Indexed: 01/09/2023] Open
Abstract
The mechanisms controlling the post-natal maturation of astrocytes play a crucial role in ensuring correct synaptogenesis. We show that mitochondrial biogenesis in developing astrocytes is necessary for coordinating post-natal astrocyte maturation and synaptogenesis. The astrocytic mitochondrial biogenesis depends on the transient upregulation of metabolic regulator peroxisome proliferator-activated receptor gamma (PPARγ) co-activator 1α (PGC-1α), which is controlled by metabotropic glutamate receptor 5 (mGluR5). At tissue level, the loss or downregulation of astrocytic PGC-1α sustains astrocyte proliferation, dampens astrocyte morphogenesis, and impairs the formation and function of neighboring synapses, whereas its genetic re-expression is sufficient to restore the mitochondria compartment and correct astroglial and synaptic defects. Our findings show that the developmental enhancement of mitochondrial biogenesis in astrocytes is a critical mechanism controlling astrocyte maturation and supporting synaptogenesis, thus suggesting that astrocytic mitochondria may be a therapeutic target in the case of neurodevelopmental and psychiatric disorders characterized by impaired synaptogenesis.
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Affiliation(s)
- Tamara Zehnder
- Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - Francesco Petrelli
- Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - Jennifer Romanos
- Institute of Pharmacology and Toxicology, University of Zurich, 8057 Zurich, Switzerland
| | - Eva C De Oliveira Figueiredo
- Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - Tommy L Lewis
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Nicole Déglon
- Department of Clinical Neurosciences, Laboratory of Neurotherapies and Neuromodulation (LNTM), Lausanne University Hospital (CHUV) and University of Lausanne, 1011 Lausanne, Switzerland; Neurosciences Research Center (CRN), Laboratory of Neurotherapies and Neuromodulation (LNTM), Lausanne University Hospital and University of Lausanne, 1011 Lausanne, Switzerland
| | - Franck Polleux
- Department of Neuroscience, Columbia University, New York, NY 10032, USA; Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Mirko Santello
- Institute of Pharmacology and Toxicology, University of Zurich, 8057 Zurich, Switzerland.
| | - Paola Bezzi
- Department of Fundamental Neurosciences, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland; Department of Physiology and Pharmacology, Sapienza University of Rome, 00185 Rome, Italy.
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12
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Gentile G, Paciello F, Zorzi V, Spampinato AG, Guarnaccia M, Crispino G, Tettey-Matey A, Scavizzi F, Raspa M, Fetoni AR, Cavallaro S, Mammano F. miRNA and mRNA Profiling Links Connexin Deficiency to Deafness via Early Oxidative Damage in the Mouse Stria Vascularis. Front Cell Dev Biol 2021; 8:616878. [PMID: 33569381 PMCID: PMC7868390 DOI: 10.3389/fcell.2020.616878] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 12/10/2020] [Indexed: 12/15/2022] Open
Abstract
Pathogenic mutations in the non-syndromic hearing loss and deafness 1 (DFNB1) locus are the primary cause of monogenic inheritance for prelingual hearing loss. To unravel molecular pathways involved in etiopathology and look for early degeneration biomarkers, we used a system biology approach to analyze Cx30−/− mice at an early cochlear post-natal developmental stage. These mice are a DFNB1 mouse model with severely reduced expression levels of two connexins in the inner ear, Cx30, and Cx26. Integrated analysis of miRNA and mRNA expression profiles in the cochleae of Cx30−/− mice at post-natal day 5 revealed the overexpression of five miRNAs (miR-34c, miR-29b, miR-29c, miR-141, and miR-181a) linked to apoptosis, oxidative stress, and cochlear degeneration, which have Sirt1 as a common target of transcriptional and/or post-transcriptional regulation. In young adult Cx30−/− mice (3 months of age), these alterations culminated with blood barrier disruption in the Stria vascularis (SV), which is known to have the highest aerobic metabolic rate of all cochlear structures and whose microvascular alterations contribute to age-related degeneration and progressive decline of auditory function. Our experimental validation of selected targets links hearing acquisition failure in Cx30−/− mice, early oxidative stress, and metabolic dysregulation to the activation of the Sirt1–p53 axis. This is the first integrated analysis of miRNA and mRNA in the cochlea of the Cx30−/− mouse model, providing evidence that connexin downregulation determines a miRNA-mediated response which leads to chronic exhaustion of cochlear antioxidant defense mechanisms and consequent SV dysfunction. Our analyses support the notion that connexin dysfunction intervenes early on during development, causing vascular damage later on in life. This study identifies also early miRNA-mediated biomarkers of hearing impairment, either inherited or age related.
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Affiliation(s)
- Giulia Gentile
- Department of Biomedical Sciences, National Research Council (CNR) Institute for Biomedical Research and Innovation, Catania, Italy
| | - Fabiola Paciello
- Department of Neuroscience, Università Cattolica del Sacro Cuore, Rome, Italy.,Fondazione Policlinico Universitario A. Gemelli Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Veronica Zorzi
- Department of Head and Neck Surgery, Università Cattolica del Sacro Cuore, Rome, Italy.,Department of Biomedical Sciences, National Research Council (CNR) Institute of Biochemistry and Cell Biology, Rome, Italy
| | - Antonio Gianmaria Spampinato
- Department of Biomedical Sciences, National Research Council (CNR) Institute for Biomedical Research and Innovation, Catania, Italy.,Department of Mathematics and Computer Science, University of Catania, Catania, Italy
| | - Maria Guarnaccia
- Department of Biomedical Sciences, National Research Council (CNR) Institute for Biomedical Research and Innovation, Catania, Italy
| | - Giulia Crispino
- Department of Biomedical Sciences, National Research Council (CNR) Institute of Biochemistry and Cell Biology, Rome, Italy
| | - Abraham Tettey-Matey
- Department of Biomedical Sciences, National Research Council (CNR) Institute of Biochemistry and Cell Biology, Rome, Italy
| | - Ferdinando Scavizzi
- Department of Biomedical Sciences, National Research Council (CNR) Institute of Biochemistry and Cell Biology, Rome, Italy
| | - Marcello Raspa
- Fondazione Policlinico Universitario A. Gemelli Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Anna Rita Fetoni
- Fondazione Policlinico Universitario A. Gemelli Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy.,Department of Head and Neck Surgery, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Sebastiano Cavallaro
- Department of Biomedical Sciences, National Research Council (CNR) Institute for Biomedical Research and Innovation, Catania, Italy
| | - Fabio Mammano
- Department of Biomedical Sciences, National Research Council (CNR) Institute of Biochemistry and Cell Biology, Rome, Italy.,Department of Physics and Astronomy "G. Galilei", University of Padua, Padua, Italy
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13
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Mazzarda F, D'Elia A, Massari R, De Ninno A, Bertani FR, Businaro L, Ziraldo G, Zorzi V, Nardin C, Peres C, Chiani F, Tettey-Matey A, Raspa M, Scavizzi F, Soluri A, Salvatore AM, Yang J, Mammano F. Organ-on-chip model shows that ATP release through connexin hemichannels drives spontaneous Ca 2+ signaling in non-sensory cells of the greater epithelial ridge in the developing cochlea. LAB ON A CHIP 2020; 20:3011-3023. [PMID: 32700707 DOI: 10.1039/d0lc00427h] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Prior work supports the hypothesis that ATP release through connexin hemichannels drives spontaneous Ca2+ signaling in non-sensory cells of the greater epithelial ridge (GER) in the developing cochlea; however, direct proof is lacking. To address this issue, we plated cochlear organotypic cultures (COCs) and whole cell-based biosensors with nM ATP sensitivity (ATP-WCBs) at the bottom and top of an ad hoc designed transparent microfluidic chamber, respectively. By performing dual multiphoton Ca2+ imaging, we monitored the propagation of intercellular Ca2+ waves in the GER of COCs and ATP-dependent Ca2+ responses in overlying ATP-WCBs. Ca2+ signals in both COCs and ATP-WCBs were inhibited by supplementing the extracellular medium with ATP diphosphohydrolase (apyrase). Spontaneous Ca2+ signals were strongly depressed in the presence of Gjb6-/- COCs, in which connexin 30 (Cx30) is absent and connexin 26 (Cx26) is strongly downregulated. In contrast, spontaneous Ca2+ signals were not affected by replacement of Panx1-/- with Panx1+/+ COCs in the microfluidic chamber. Similar results were obtained by estimating ATP release from COCs using a classical luciferin-luciferase bioluminescence assay. Therefore, connexin hemichannels and not pannexin 1 channels mediate the release of ATP that is responsible for Ca2+ wave propagation in the developing mouse cochlea. The technological advances presented here have the potential to shed light on a plethora of unrelated open issues that involve paracrine signaling in physiology and pathology and cannot be addressed with standard methods.
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Affiliation(s)
- Flavia Mazzarda
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy. and Department of Science, Università degli Studi di Roma3, Rome, Italy
| | - Annunziata D'Elia
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy. and Department of Science, Università degli Studi di Roma3, Rome, Italy
| | - Roberto Massari
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy.
| | - Adele De Ninno
- CNR Institute for Photonics and Nanotechnology, Rome, Italy.
| | | | - Luca Businaro
- CNR Institute for Photonics and Nanotechnology, Rome, Italy.
| | - Gaia Ziraldo
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy. and Institute of Otorhinolaryngology, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Veronica Zorzi
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy. and Institute of Otorhinolaryngology, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Chiara Nardin
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy.
| | - Chiara Peres
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy.
| | - Francesco Chiani
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy.
| | | | - Marcello Raspa
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy.
| | | | - Alessandro Soluri
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy.
| | | | - Jun Yang
- Department of Otorhinolaryngology Head and Neck Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. and Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai, China
| | - Fabio Mammano
- CNR Institute of Biochemistry and Cell Biology, Monterotondo, Rome, Italy. and Department of Physics and Astronomy "G. Galilei", University of Padova, Padua, Italy.
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14
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Ghézali G, Vasile F, Curry N, Fantham M, Cheung G, Ezan P, Cohen-Salmon M, Kaminski C, Rouach N. Neuronal Activity Drives Astroglial Connexin 30 in Perisynaptic Processes and Shapes Its Functions. Cereb Cortex 2020; 30:753-766. [PMID: 31271200 PMCID: PMC7086174 DOI: 10.1093/cercor/bhz123] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 04/22/2019] [Accepted: 05/17/2019] [Indexed: 12/17/2022] Open
Abstract
Astrocytes play key roles in brain functions through dynamic interactions with neurons. One of their typical features is to express high levels of connexins (Cxs), Cx43 and Cx30, the gap junction (GJ)-forming proteins. Cx30 is involved in basic cognitive processes and shapes synaptic and network activities, as shown by recent studies in transgenic animals. Yet it remains unknown whether astroglial Cx30 expression, localization, and functions are endogenously and dynamically regulated by neuronal activity and could therefore play physiological roles in neurotransmission. We here show that neuronal activity increased hippocampal Cx30 protein levels via a posttranslational mechanism regulating lysosomal degradation. Neuronal activity also increased Cx30 protein levels at membranes and perisynaptic processes, as revealed by superresolution imaging. This translated at the functional level in the activation of Cx30 hemichannels and in Cx30-mediated remodeling of astrocyte morphology independently of GJ biochemical coupling. Altogether, these data show activity-dependent dynamics of Cx30 expression, perisynaptic localization, and functions.
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Affiliation(s)
- Grégory Ghézali
- Neuroglial Interactions in Cerebral Physiology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, 75005 Paris, France
- Doctoral School N° 158, Pierre and Marie Curie University, 75006 Paris, France
| | - Flora Vasile
- Neuroglial Interactions in Cerebral Physiology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, 75005 Paris, France
- Doctoral School N°474, Rene Descartes University, 75006 Paris, France
| | - Nathan Curry
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK
| | - Marcus Fantham
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK
| | - Giselle Cheung
- Neuroglial Interactions in Cerebral Physiology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, 75005 Paris, France
| | - Pascal Ezan
- Neuroglial Interactions in Cerebral Physiology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, 75005 Paris, France
| | - Martine Cohen-Salmon
- Neuroglial Interactions in Cerebral Physiology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, 75005 Paris, France
| | - Clemens Kaminski
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiology, Center for Interdisciplinary Research in Biology, Collège de France, CNRS UMR 7241, INSERM U1050, Labex Memolife, PSL Research University, 75005 Paris, France
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15
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Mammano F. Inner Ear Connexin Channels: Roles in Development and Maintenance of Cochlear Function. Cold Spring Harb Perspect Med 2019; 9:a033233. [PMID: 30181354 PMCID: PMC6601451 DOI: 10.1101/cshperspect.a033233] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Connexin 26 and connexin 30 are the prevailing isoforms in the epithelial and connective tissue gap junction systems of the developing and mature cochlea. The most frequently encountered variants of the genes that encode these connexins, which are transcriptionally coregulated, determine complete loss of protein function and are the predominant cause of prelingual hereditary deafness. Reducing connexin 26 expression by Cre/loxP recombination in the inner ear of adult mice results in a decreased endocochlear potential, increased hearing thresholds, and loss of >90% of outer hair cells, indicating that this connexin is essential for maintenance of cochlear function. In the developing cochlea, connexins are necessary for intercellular calcium signaling activity. Ribbon synapses and basolateral membrane currents fail to mature in inner hair cells of mice that are born with reduced connexin expression, even though hair cells do not express any connexin. In contrast, pannexin 1, an alternative mediator of intercellular signaling, is dispensable for hearing acquisition and auditory function.
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Affiliation(s)
- Fabio Mammano
- University of Padova, Department of Physics and Astronomy "G. Galilei," Padova 35129, Italy
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai 201210, China
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16
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Kelly JJ, Abitbol JM, Hulme S, Press ER, Laird DW, Allman BL. The connexin 30 A88V mutant reduces cochlear gap junction expression and confers long-term protection against hearing loss. J Cell Sci 2019; 132:jcs.224097. [PMID: 30559251 DOI: 10.1242/jcs.224097] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 12/06/2018] [Indexed: 12/23/2022] Open
Abstract
Mutations in the genes that encode the gap junction proteins connexin 26 (Cx26, encoded by GJB2) and Cx30 (GJB6) are the leading cause of hereditary hearing loss. That said, the Cx30 p.Ala88Val (A88V) mutant causes Clouston syndrome, but not hearing loss. Here, we report that the Cx30-A88V mutant, despite being toxic to inner ear-derived HEI-OC1 cells, conferred remarkable long-term protection against age-related high frequency hearing loss in Cx30A88V/A88V mice. During early development, there were no overt structural differences in the cochlea between genotypes, including a normal complement of hair cells; however, the supporting cell Cx30 gap junction plaques in mutant mice were reduced in size. In adulthood, Cx30A88V/A88V mutant mice had a reduction of cochlear Cx30 mRNA and protein, yet a full complement of hair cells. Conversely, the age-related high frequency hearing loss in Cx30+/+ and Cx30+/A88V mice was due to extensive loss of outer hair cells. Our data suggest that the Cx30-A88V mutant confers long-term hearing protection and prevention of hair cell death, possibly via a feedback mechanism that leads to the reduction of total Cx30 gap junction expression in the cochlea.
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Affiliation(s)
- John J Kelly
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Julia M Abitbol
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Stephanie Hulme
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Eric R Press
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Dale W Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Brian L Allman
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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17
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Sirko P, Gale JE, Ashmore JF. Intercellular Ca 2+ signalling in the adult mouse cochlea. J Physiol 2018; 597:303-317. [PMID: 30318615 PMCID: PMC6312409 DOI: 10.1113/jp276400] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 10/12/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Intercellular Ca2+ waves are increases in cytoplasmic Ca2+ levels that propagate between cells. Periodic Ca2+ waves have been linked to gene regulation and are thought to play a crucial role in the development of our hearing epithelium, the organ of Corti and the acquisition of hearing. We observed regular periodic intercellular Ca2+ waves in supporting cells of an ex vivo preparation of the adult mouse organ of Corti, and these waves were found to propagate independently of extracellular ATP and were inhibited by the gap junction blockers 1-octanol and carbenoxolone. Our results establish that the existence of periodic Ca2+ waves in the organ of Corti is not restricted to the prehearing period. ABSTRACT We have investigated wave-like cytoplasmic calcium (Ca2+ ) signalling in an ex vivo preparation of the adult mouse organ of Corti. Two types of intercellular Ca2+ waves that differ in propagation distance and speed were observed. One type was observed to travel up to 100 μm with an average velocity of 7 μm/s. Such waves were initiated by local tissue damage in the outer hair cell region. The propagation distance was decreased when the purinergic receptor antagonists pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS; 50 μm) or suramin (150 μm) were added to the extracellular buffer. Immunocytochemical analysis and experiments with calcium indicator dyes showed that both P2X and P2Y receptors were present in supporting cells. A second class of waves identified to travel longitudinally along the organ of Corti propagated at a lower velocity of 1-3 μm/s. These 'slow' Ca2+ waves were particularly evident in the inner sulcus and Deiters' cells. They travelled for distances of up to 500 μm. The slow Ca2+ signalling varied periodically (approximately one wave every 10 min) and was maintained for more than 3 h. The slow waves were not affected by apyrase, or by the P2 receptor agonists suramin (150 μm) or PPADS (50 μm) but were blocked by the connexin channel blockers octanol (1 mm) and carbenoxolone (100 μm). It is proposed that the observed Ca2+ waves might be a physiological response to a change in extracellular environment and may be involved in critical gene regulation activities in the supporting cells of the cochlea.
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Affiliation(s)
- Piotr Sirko
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK
| | - Jonathan E Gale
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.,Department of Cell & Developmental Biology, UCL, Gower St., London, WC1E 6BT, UK
| | - Jonathan F Ashmore
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.,Department of Neuroscience, Physiology & Pharmacology, UCL, Gower St., London, WC1E 6BT, UK
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18
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Fetoni AR, Zorzi V, Paciello F, Ziraldo G, Peres C, Raspa M, Scavizzi F, Salvatore AM, Crispino G, Tognola G, Gentile G, Spampinato AG, Cuccaro D, Guarnaccia M, Morello G, Van Camp G, Fransen E, Brumat M, Girotto G, Paludetti G, Gasparini P, Cavallaro S, Mammano F. Cx26 partial loss causes accelerated presbycusis by redox imbalance and dysregulation of Nfr2 pathway. Redox Biol 2018; 19:301-317. [PMID: 30199819 PMCID: PMC6129666 DOI: 10.1016/j.redox.2018.08.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 07/26/2018] [Accepted: 08/05/2018] [Indexed: 11/29/2022] Open
Abstract
Mutations in GJB2, the gene that encodes connexin 26 (Cx26), are the most common cause of sensorineural hearing impairment. The truncating variant 35delG, which determines a complete loss of Cx26 protein function, is the prevalent GJB2 mutation in several populations. Here, we generated and analyzed Gjb2+/- mice as a model of heterozygous human carriers of 35delG. Compared to control mice, auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) worsened over time more rapidly in Gjb2+/- mice, indicating they were affected by accelerated age-related hearing loss (ARHL), or presbycusis. We linked causally the auditory phenotype of Gjb2+/- mice to apoptosis and oxidative damage in the cochlear duct, reduced release of glutathione from connexin hemichannels, decreased nutrient delivery to the sensory epithelium via cochlear gap junctions and deregulated expression of genes that are under transcriptional control of the nuclear factor erythroid 2-related factor 2 (Nrf2), a pivotal regulator of tolerance to redox stress. Moreover, a statistically significant genome-wide association with two genes (PRKCE and TGFB1) related to the Nrf2 pathway (p-value < 4 × 10-2) was detected in a very large cohort of 4091 individuals, originating from Europe, Caucasus and Central Asia, with hearing phenotype (including 1076 presbycusis patients and 1290 healthy matched controls). We conclude that (i) elements of the Nrf2 pathway are essential for hearing maintenance and (ii) their dysfunction may play an important role in the etiopathogenesis of human presbycusis.
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Affiliation(s)
- Anna Rita Fetoni
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy; Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy; Institute of Otolaryngology, Fondazione Policlinico Universitario A. Gemelli IRCCS, Largo F. Vito 1, 00168 Rome, Italy
| | - Veronica Zorzi
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy; Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy
| | - Fabiola Paciello
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy; Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy
| | - Gaia Ziraldo
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy; Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy
| | - Chiara Peres
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy
| | - Marcello Raspa
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy
| | | | | | - Giulia Crispino
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy
| | - Gabriella Tognola
- CNR Institute of Electronics, Computer and Telecommunication Engineering, 20133 Milano, Italy
| | - Giulia Gentile
- CNR Institute of Neurological Sciences, 95126 Catania, Italy
| | | | - Denis Cuccaro
- CNR Institute of Neurological Sciences, 95126 Catania, Italy
| | | | | | - Guy Van Camp
- Center of Medical Genetics, University of Antwerp and Antwerp University Hospital, Universiteitsplein 1, 2610 Antwerp, Belgium
| | - Erik Fransen
- Department of Biomedical Sciences, University of Antwerp, 2650 Antwerp, Belgium
| | - Marco Brumat
- Dept Med Surg & Hlth Sci, University of Trieste, Trieste, Italy; IRCCS Burlo Garofolo, Inst Maternal & Child Hlth, Trieste, Italy
| | - Giorgia Girotto
- Dept Med Surg & Hlth Sci, University of Trieste, Trieste, Italy; IRCCS Burlo Garofolo, Inst Maternal & Child Hlth, Trieste, Italy
| | - Gaetano Paludetti
- Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Rome, Italy; Institute of Otolaryngology, Fondazione Policlinico Universitario A. Gemelli IRCCS, Largo F. Vito 1, 00168 Rome, Italy
| | - Paolo Gasparini
- Dept Med Surg & Hlth Sci, University of Trieste, Trieste, Italy; IRCCS Burlo Garofolo, Inst Maternal & Child Hlth, Trieste, Italy.
| | | | - Fabio Mammano
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy; University of Padova, Department of Physics and Astronomy "G. Galilei", Padova, Italy.
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19
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Delmar M, Laird DW, Naus CC, Nielsen MS, Verselis VK, White TW. Connexins and Disease. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a029348. [PMID: 28778872 DOI: 10.1101/cshperspect.a029348] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Inherited or acquired alterations in the structure and function of connexin proteins have long been associated with disease. In the present work, we review current knowledge on the role of connexins in diseases associated with the heart, nervous system, cochlea, and skin, as well as cancer and pleiotropic syndromes such as oculodentodigital dysplasia (ODDD). Although incomplete by virtue of space and the extent of the topic, this review emphasizes the fact that connexin function is not only associated with gap junction channel formation. As such, both canonical and noncanonical functions of connexins are fundamental components in the pathophysiology of multiple connexin related disorders, many of them highly debilitating and life threatening. Improved understanding of connexin biology has the potential to advance our understanding of mechanisms, diagnosis, and treatment of disease.
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Affiliation(s)
- Mario Delmar
- The Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, New York 10016
| | - Dale W Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A5C1, Canada
| | - Christian C Naus
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Morten S Nielsen
- Department of Biological Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark
| | - Vytautas K Verselis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, New York 10461
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11790
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20
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Bartle EI, Rao TC, Urner TM, Mattheyses AL. Bridging the gap: Super-resolution microscopy of epithelial cell junctions. Tissue Barriers 2018; 6:e1404189. [PMID: 29420122 PMCID: PMC5823550 DOI: 10.1080/21688370.2017.1404189] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 10/26/2017] [Accepted: 10/30/2017] [Indexed: 02/02/2023] Open
Abstract
Cell junctions are critical for cell adhesion and communication in epithelial tissues. It is evident that the cellular distribution, size, and architecture of cell junctions play a vital role in regulating function. These details of junction architecture have been challenging to elucidate in part due to the complexity and size of cell junctions. A major challenge in understanding these features is attaining high resolution spatial information with molecular specificity. Fluorescence microscopy allows localization of specific proteins to junctions, but with a resolution on the same scale as junction size, rendering internal protein organization unobtainable. Super-resolution microscopy provides a bridge between fluorescence microscopy and nanoscale approaches, utilizing fluorescent tags to reveal protein organization below the resolution limit. Here we provide a brief introduction to super-resolution microscopy and discuss novel findings into the organization, structure and function of epithelial cell junctions.
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Affiliation(s)
- Emily I. Bartle
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Tejeshwar C. Rao
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Tara M. Urner
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Alexa L. Mattheyses
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
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21
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del Castillo FJ, del Castillo I. DFNB1 Non-syndromic Hearing Impairment: Diversity of Mutations and Associated Phenotypes. Front Mol Neurosci 2017; 10:428. [PMID: 29311818 PMCID: PMC5743749 DOI: 10.3389/fnmol.2017.00428] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 12/07/2017] [Indexed: 02/02/2023] Open
Abstract
The inner ear is a very complex sensory organ whose development and function depend on finely balanced interactions among diverse cell types. The many different kinds of inner ear supporting cells play the essential roles of providing physical and physiological support to sensory hair cells and of maintaining cochlear homeostasis. Appropriately enough, the gene most commonly mutated among subjects with hereditary hearing impairment (HI), GJB2, encodes the connexin-26 (Cx26) gap-junction channel protein that underlies both intercellular communication among supporting cells and homeostasis of the cochlear fluids, endolymph and perilymph. GJB2 lies at the DFNB1 locus on 13q12. The specific kind of HI associated with this locus is caused by recessively-inherited mutations that inactivate the two alleles of the GJB2 gene, either in homozygous or compound heterozygous states. We describe the many diverse classes of genetic alterations that result in DFNB1 HI, such as large deletions that either destroy the GJB2 gene or remove a regulatory element essential for GJB2 expression, point mutations that interfere with promoter function or splicing, and small insertions or deletions and nucleotide substitutions that target the GJB2 coding sequence. We focus on how these alterations disrupt GJB2 and Cx26 functions and on their different effects on cochlear development and physiology. We finally discuss the diversity of clinical features of DFNB1 HI as regards severity, age of onset, inner ear malformations and vestibular dysfunction, highlighting the areas where future research should be concentrated.
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Affiliation(s)
- Francisco J. del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Ignacio del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
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22
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Zorzi V, Paciello F, Ziraldo G, Peres C, Mazzarda F, Nardin C, Pasquini M, Chiani F, Raspa M, Scavizzi F, Carrer A, Crispino G, Ciubotaru CD, Monyer H, Fetoni AR, M Salvatore A, Mammano F. Mouse Panx1 Is Dispensable for Hearing Acquisition and Auditory Function. Front Mol Neurosci 2017; 10:379. [PMID: 29234270 PMCID: PMC5712377 DOI: 10.3389/fnmol.2017.00379] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 10/30/2017] [Indexed: 11/13/2022] Open
Abstract
Panx1 forms plasma membrane channels in brain and several other organs, including the inner ear. Biophysical properties, activation mechanisms and modulators of Panx1 channels have been characterized in detail, however the impact of Panx1 on auditory function is unclear due to conflicts in published results. To address this issue, hearing performance and cochlear function of the Panx1−/− mouse strain, the first with a reported global ablation of Panx1, were scrutinized. Male and female homozygous (Panx1−/−), hemizygous (Panx1+/−) and their wild type (WT) siblings (Panx1+/+) were used for this study. Successful ablation of Panx1 was confirmed by RT-PCR and Western immunoblotting in the cochlea and brain of Panx1−/− mice. Furthermore, a previously validated Panx1-selective antibody revealed strong immunoreactivity in WT but not in Panx1−/− cochleae. Hearing sensitivity, outer hair cell-based “cochlear amplifier” and cochlear nerve function, analyzed by auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) recordings, were normal in Panx1+/− and Panx1−/− mice. In addition, we determined that global deletion of Panx1 impacts neither on connexin expression, nor on gap-junction coupling in the developing organ of Corti. Finally, spontaneous intercellular Ca2+ signal (ICS) activity in organotypic cochlear cultures, which is key to postnatal development of the organ of Corti and essential for hearing acquisition, was not affected by Panx1 ablation. Therefore, our results provide strong evidence that, in mice, Panx1 is dispensable for hearing acquisition and auditory function.
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Affiliation(s)
- Veronica Zorzi
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,School of Medicine, Institute of Otolaryngology, Catholic University, Rome, Italy
| | - Fabiola Paciello
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Gaia Ziraldo
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,School of Medicine, Institute of Otolaryngology, Catholic University, Rome, Italy
| | - Chiara Peres
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Flavia Mazzarda
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Science, Roma Tre University, Rome, Italy
| | - Chiara Nardin
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Science, Roma Tre University, Rome, Italy
| | - Miriam Pasquini
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, Italy
| | - Francesco Chiani
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Marcello Raspa
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | | | - Andrea Carrer
- Department of Physics and Astronomy G. Galilei, University of Padua, Padua, Italy
| | - Giulia Crispino
- Department of Physics and Astronomy G. Galilei, University of Padua, Padua, Italy
| | | | - Hannah Monyer
- Department of Clinical Neurobiology, Deutches Krebforschungzentrum, University of Heidelberg, Heidelberg, Germany
| | - Anna R Fetoni
- School of Medicine, Institute of Otolaryngology, Catholic University, Rome, Italy
| | - Anna M Salvatore
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Fabio Mammano
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Physics and Astronomy G. Galilei, University of Padua, Padua, Italy.,Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
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23
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Mao B, Moss CF, Wilkinson GS. Age-dependent gene expression in the inner ear of big brown bats (Eptesicus fuscus). PLoS One 2017; 12:e0186667. [PMID: 29073148 PMCID: PMC5658057 DOI: 10.1371/journal.pone.0186667] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2017] [Accepted: 10/05/2017] [Indexed: 12/25/2022] Open
Abstract
For echolocating bats, hearing is essential for survival. Specializations for detecting and processing high frequency sounds are apparent throughout their auditory systems. Recent studies on echolocating mammals have reported evidence of parallel evolution in some hearing-related genes in which distantly related groups of echolocating animals (bats and toothed whales), cluster together in gene trees due to apparent amino acid convergence. However, molecular adaptations can occur not only in coding sequences, but also in the regulation of gene expression. The aim of this study was to examine the expression of hearing-related genes in the inner ear of developing big brown bats, Eptesicus fuscus, during the period in which echolocation vocalizations increase dramatically in frequency. We found that seven genes were significantly upregulated in juveniles relative to adults, and that the expression of four genes through development correlated with estimated age. Compared to available data for mice, it appears that expression of some hearing genes is extended in juvenile bats. These results are consistent with a prolonged growth period required to develop larger cochlea relative to body size, a later maturation of high frequency hearing, and a greater dependence on high frequency hearing in echolocating bats.
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Affiliation(s)
- Beatrice Mao
- Department of Biology, College of Computer, Mathematical, and Natural Sciences, University of Maryland, College Park, Maryland, United States of America
| | - Cynthia F. Moss
- Department of Psychological and Brain Sciences, Zanvyl Krieger School of Arts and Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Gerald S. Wilkinson
- Department of Biology, College of Computer, Mathematical, and Natural Sciences, University of Maryland, College Park, Maryland, United States of America
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24
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Xu L, Carrer A, Zonta F, Qu Z, Ma P, Li S, Ceriani F, Buratto D, Crispino G, Zorzi V, Ziraldo G, Bruno F, Nardin C, Peres C, Mazzarda F, Salvatore AM, Raspa M, Scavizzi F, Chu Y, Xie S, Yang X, Liao J, Liu X, Wang W, Wang S, Yang G, Lerner RA, Mammano F. Design and Characterization of a Human Monoclonal Antibody that Modulates Mutant Connexin 26 Hemichannels Implicated in Deafness and Skin Disorders. Front Mol Neurosci 2017; 10:298. [PMID: 29018324 PMCID: PMC5615210 DOI: 10.3389/fnmol.2017.00298] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 09/05/2017] [Indexed: 12/21/2022] Open
Abstract
Background: Mutations leading to changes in properties, regulation, or expression of connexin-made channels have been implicated in 28 distinct human hereditary diseases. Eight of these result from variants of connexin 26 (Cx26), a protein critically involved in cell-cell signaling in the inner ear and skin. Lack of non-toxic drugs with defined mechanisms of action poses a serious obstacle to therapeutic interventions for diseases caused by mutant connexins. In particular, molecules that specifically modulate connexin hemichannel function without affecting gap junction channels are considered of primary importance for the study of connexin hemichannel role in physiological as well as pathological conditions. Monoclonal antibodies developed in the last three decades have become the most important class of therapeutic biologicals. Recombinant methods permit rapid selection and improvement of monoclonal antibodies from libraries with large diversity. Methods: By screening a combinatorial library of human single-chain fragment variable (scFv) antibodies expressed in phage, we identified a candidate that binds an extracellular epitope of Cx26. We characterized antibody action using a variety of biochemical and biophysical assays in HeLa cells, organotypic cultures of mouse cochlea and human keratinocyte-derived cells. Results: We determined that the antibody is a remarkably efficient, non-toxic, and completely reversible inhibitor of hemichannels formed by connexin 26 and does not affect direct cell-cell communication via gap junction channels. Importantly, we also demonstrate that the antibody efficiently inhibits hyperative mutant Cx26 hemichannels implicated in autosomal dominant non-syndromic hearing impairment accompanied by keratitis and hystrix-like ichthyosis-deafness (KID/HID) syndrome. We solved the crystal structure of the antibody, identified residues that are critical for binding and used molecular dynamics to uncover its mechanism of action. Conclusions: Although further studies will be necessary to validate the effect of the antibody in vivo, the methodology described here can be extended to select antibodies against hemichannels composed by other connexin isoforms and, consequently, to target other pathologies associated with hyperactive hemichannels. Our study highlights the potential of this approach and identifies connexins as therapeutic targets addressable by screening phage display libraries expressing human randomized antibodies.
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Affiliation(s)
- Liang Xu
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China.,Institute of Biochemistry and Cell Biology, Shanghai Institute for Biological Sciences, Chinese Academy of SciencesShanghai, China
| | - Andrea Carrer
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Department of Physics and Astronomy "G. Galilei,", University of PadovaPadova, Italy
| | - Francesco Zonta
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China.,CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy
| | - Zhihu Qu
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China
| | - Peixiang Ma
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China
| | - Sheng Li
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China
| | - Federico Ceriani
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Department of Physics and Astronomy "G. Galilei,", University of PadovaPadova, Italy
| | - Damiano Buratto
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Department of Physics and Astronomy "G. Galilei,", University of PadovaPadova, Italy
| | - Giulia Crispino
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Department of Physics and Astronomy "G. Galilei,", University of PadovaPadova, Italy.,Venetian Institute of Molecular MedicinePadova, Italy
| | - Veronica Zorzi
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Institute of Otolaryngology, Catholic University School of MedicineRome, Italy
| | - Gaia Ziraldo
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Department of Physics and Astronomy "G. Galilei,", University of PadovaPadova, Italy.,Institute of Otolaryngology, Catholic University School of MedicineRome, Italy
| | - Francesca Bruno
- Department of Physics and Astronomy "G. Galilei,", University of PadovaPadova, Italy.,Venetian Institute of Molecular MedicinePadova, Italy
| | - Chiara Nardin
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Department of Science, Roma Tre UniversityRome, Italy
| | - Chiara Peres
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy
| | - Flavia Mazzarda
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Department of Science, Roma Tre UniversityRome, Italy
| | - Anna M Salvatore
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy
| | - Marcello Raspa
- CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy
| | | | - Youjun Chu
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China
| | - Sichun Xie
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China
| | - Xuemei Yang
- School of Life Science and Technology, Shanghai Tech UniversityShanghai, China
| | - Jun Liao
- School of Life Science and Technology, Shanghai Tech UniversityShanghai, China
| | - Xiao Liu
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China.,Institute of Biochemistry and Cell Biology, Shanghai Institute for Biological Sciences, Chinese Academy of SciencesShanghai, China.,University of Chinese Academy of SciencesBeijing, China
| | - Wei Wang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China
| | - Shanshan Wang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China
| | - Guang Yang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China
| | - Richard A Lerner
- Department of Cell and Molecular Biology, The Scripps Research InstituteLa Jolla, CA, United States
| | - Fabio Mammano
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech UniversityShanghai, China.,CNR Institute of Cell Biology and NeurobiologyMonterotondo, Italy.,Department of Physics and Astronomy "G. Galilei,", University of PadovaPadova, Italy.,Venetian Institute of Molecular MedicinePadova, Italy
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25
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In vivo genetic manipulation of inner ear connexin expression by bovine adeno-associated viral vectors. Sci Rep 2017; 7:6567. [PMID: 28779115 PMCID: PMC5544751 DOI: 10.1038/s41598-017-06759-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 06/19/2017] [Indexed: 01/03/2023] Open
Abstract
We have previously shown that in vitro transduction with bovine adeno–associated viral (BAAV) vectors restores connexin expression and rescues gap junction coupling in cochlear organotypic cultures from connexin–deficient mice that are models DFNB1 nonsyndromic hearing loss and deafness. The aims of this study were to manipulate inner ear connexin expression in vivo using BAAV vectors, and to identify the optimal route of vector delivery. Injection of a BAAV vector encoding a bacterial Cre recombinase via canalostomy in adult mice with floxed connexin 26 (Cx26) alleles promoted Cre/LoxP recombination, resulting in decreased Cx26 expression, decreased endocochlear potential, increased hearing thresholds, and extensive loss of outer hair cells. Injection of a BAAV vector encoding GFP-tagged Cx30 via canalostomy in P4 mice lacking connexin 30 (Cx30) promoted formation of Cx30 gap junctions at points of contacts between adjacent non-sensory cells of the cochlear sensory epithelium. Levels of exogenous Cx30 decayed over time, but were still detectable four weeks after canalostomy. Our results suggest that persistence of BAAV-mediated gene replacement in the cochlea is limited by the extensive remodeling of the organ of Corti throughout postnatal development and associated loss of non-sensory cells.
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26
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Connexin-Mediated Signaling in Nonsensory Cells Is Crucial for the Development of Sensory Inner Hair Cells in the Mouse Cochlea. J Neurosci 2017; 37:258-268. [PMID: 28077706 PMCID: PMC5242392 DOI: 10.1523/jneurosci.2251-16.2016] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 10/10/2016] [Accepted: 11/07/2016] [Indexed: 12/03/2022] Open
Abstract
Mutations in the genes encoding for gap junction proteins connexin 26 (Cx26) and connexin 30 (Cx30) have been linked to syndromic and nonsyndromic hearing loss in mice and humans. The release of ATP from connexin hemichannels in cochlear nonsensory cells has been proposed to be the main trigger for action potential activity in immature sensory inner hair cells (IHCs), which is crucial for the refinement of the developing auditory circuitry. Using connexin knock-out mice, we show that IHCs fire spontaneous action potentials even in the absence of ATP-dependent intercellular Ca2+ signaling in the nonsensory cells. However, this signaling from nonsensory cells was able to increase the intrinsic IHC firing frequency. We also found that connexin expression is key to IHC functional maturation. In Cx26 conditional knock-out mice (Cx26Sox10-Cre), the maturation of IHCs, which normally occurs at approximately postnatal day 12, was partially prevented. Although Cx30 has been shown not to be required for hearing in young adult mice, IHCs from Cx30 knock-out mice exhibited a comprehensive brake in their development, such that their basolateral membrane currents and synaptic machinery retain a prehearing phenotype. We propose that IHC functional differentiation into mature sensory receptors is initiated in the prehearing cochlea provided that the expression of either connexin reaches a threshold level. As such, connexins regulate one of the most crucial functional refinements in the mammalian cochlea, the disruption of which contributes to the deafness phenotype observed in mice and DFNB1 patients. SIGNIFICANCE STATEMENT The correct development and function of the mammalian cochlea relies not only on the sensory hair cells, but also on the surrounding nonsensory cells. Although the nonsensory cells have been largely implicated in the general homeostasis in the mature cochlea, their involvement in the initial functional differentiation of the sensory inner hair cells is less clear. Using mutant mouse models for the most common form of congenital deafness in humans, which are knock-outs for the gap-junction channels connexin 26 and connexin 30 genes, we show that defects in nonsensory cells prevented the functional maturation of inner hair cells. In connexin knock-outs, inner hair cells remained stuck at a prehearing stage of development and, as such, are unable to process sound information.
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Zhao HB. Hypothesis of K +-Recycling Defect Is Not a Primary Deafness Mechanism for Cx26 ( GJB2) Deficiency. Front Mol Neurosci 2017; 10:162. [PMID: 28603488 PMCID: PMC5445178 DOI: 10.3389/fnmol.2017.00162] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 05/10/2017] [Indexed: 12/20/2022] Open
Abstract
K+-recycling defect is a long-standing hypothesis for deafness mechanism of Connexin26 (Cx26, GJB2) mutations, which cause the most common hereditary deafness and are responsible for >50% of nonsyndromic hearing loss. The hypothesis states that Cx26 deficiency may disrupt inner ear gap junctions and compromise sinking and recycling of expelled K+ ions after hair cell excitation, causing accumulation of K+-ions in the extracellular space around hair cells producing K+-toxicity, which eventually induces hair cell degeneration and hearing loss. However, this hypothesis has never been directly evidenced, even though it has been widely referred to. Recently, more and more experiments demonstrate that this hypothesis may not be a deafness mechanism underlying Cx26 deficiency. In this review article, we summarized recent advances on the K+-recycling and mechanisms underlying Cx26 deficiency induced hearing loss. The mechanisms underlying K+-sinking, which is the first step for K+-recycling in the cochlea, and Cx26 deficiency induced cochlear developmental disorders, which are responsible for Cx26 deficiency induced congenital deafness and associated with disruption of permeability of inner ear gap junctional channels to miRNAs, are also summarized and discussed.
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Affiliation(s)
- Hong-Bo Zhao
- Department of Otolaryngology, University of Kentucky Medical CenterLexington, KY, United States
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28
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Mammano F, Bortolozzi M. Ca 2+ signaling, apoptosis and autophagy in the developing cochlea: Milestones to hearing acquisition. Cell Calcium 2017; 70:117-126. [PMID: 28578918 DOI: 10.1016/j.ceca.2017.05.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/09/2017] [Accepted: 05/09/2017] [Indexed: 12/16/2022]
Abstract
In mammals, the sense of hearing arises through a complex sequence of morphogenetic events that drive the sculpting of the auditory sensory epithelium into its terminally functional three-dimensional shape. While the majority of the underlying mechanisms remain unknown, it has become increasingly clear that Ca2+ signaling is at center stage and plays numerous fundamental roles both in the sensory hair cells and in the matrix of non-sensory, epithelial and supporting cells, which embed them and are tightly interconnected by a dense network of gap junctions formed by connexin 26 (Cx26) and connexin 30 (Cx30) protein subunits. In this review, we discuss the intricate interplay between Ca2+ signaling, connexin expression and function, apoptosis and autophagy in the crucial steps that lead to hearing acquisition.
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Affiliation(s)
- Fabio Mammano
- Department of Physics and Astronomy "G. Galilei", University of Padua, 35131 Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Foundation for Advanced Biomedical Research, 35129 Padua, Italy; Department of Biomedical Sciences, Institute of Cell Biology and Neurobiology, Italian National Research Council, 00015 Monterotondo, (RM), Italy.
| | - Mario Bortolozzi
- Department of Physics and Astronomy "G. Galilei", University of Padua, 35131 Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Foundation for Advanced Biomedical Research, 35129 Padua, Italy; Department of Biomedical Sciences, Institute of Protein Biochemistry, Italian National Research Council, 80131 Naples (NA), Italy
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Critical role of ATP-induced ATP release for Ca2+ signaling in nonsensory cell networks of the developing cochlea. Proc Natl Acad Sci U S A 2016; 113:E7194-E7201. [PMID: 27807138 DOI: 10.1073/pnas.1616061113] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Spatially and temporally coordinated variations of the cytosolic free calcium concentration ([Ca2+]c) play a crucial role in a variety of tissues. In the developing sensory epithelium of the mammalian cochlea, elevation of extracellular adenosine trisphosphate concentration ([ATP]e) triggers [Ca2+]c oscillations and propagation of intercellular inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ waves. What remains uncertain is the relative contribution of gap junction channels and connexin hemichannels to these fundamental mechanisms, defects in which impair hearing acquisition. Another related open question is whether [Ca2+]c oscillations require oscillations of the cytosolic IP3 concentration ([IP3]c) in this system. To address these issues, we performed Ca2+ imaging experiments in the lesser epithelial ridge of the mouse cochlea around postnatal day 5 and constructed a computational model in quantitative adherence to experimental data. Our results indicate that [Ca2+]c oscillations are governed by Hopf-type bifurcations within the experimental range of [ATP]e and do not require [IP3]c oscillations. The model replicates accurately the spatial extent and propagation speed of intercellular Ca2+ waves and predicts that ATP-induced ATP release is the primary mechanism underlying intercellular propagation of Ca2+ signals. The model also uncovers a discontinuous transition from propagating regimes (intercellular Ca2+ wave speed > 11 μm⋅s-1) to propagation failure (speed = 0), which occurs upon lowering the maximal ATP release rate below a minimal threshold value. The approach presented here overcomes major limitations due to lack of specific connexin channel inhibitors and can be extended to other coupled cellular systems.
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30
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Esseltine JL, Laird DW. Next-Generation Connexin and Pannexin Cell Biology. Trends Cell Biol 2016; 26:944-955. [PMID: 27339936 DOI: 10.1016/j.tcb.2016.06.003] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 06/02/2016] [Accepted: 06/06/2016] [Indexed: 01/17/2023]
Abstract
Connexins and pannexins are two families of large-pore channel forming proteins that are capable of passing small signaling molecules. While connexins serve the seminal task of direct gap junctional intercellular communication, pannexins are far less understood but function primarily as single membrane channels in autocrine and paracrine signaling. Advancements in connexin and pannexin biology in recent years has revealed that in addition to well-described classical functions at the plasma membrane, exciting new evidence suggests that connexins and pannexins participate in alternative pathways involving multiple intracellular compartments. Here we briefly highlight classical functions of connexins and pannexins but focus our attention mostly on the transformative findings that suggest that these channel-forming proteins may serve roles far beyond our current understandings.
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Affiliation(s)
- Jessica L Esseltine
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
| | - Dale W Laird
- Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada.
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31
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Super-resolution structured illumination fluorescence microscopy of the lateral wall of the cochlea: the Connexin26/30 proteins are separately expressed in man. Cell Tissue Res 2016; 365:13-27. [DOI: 10.1007/s00441-016-2359-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 01/07/2016] [Indexed: 10/22/2022]
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32
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Burke WF, Warnecke A, Schöner-Heinisch A, Lesinski-Schiedat A, Maier H, Lenarz T. Prevalence and audiological profiles of GJB2 mutations in a large collective of hearing impaired patients. Hear Res 2016; 333:77-86. [PMID: 26778469 DOI: 10.1016/j.heares.2016.01.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 01/07/2016] [Accepted: 01/13/2016] [Indexed: 11/28/2022]
Abstract
Mutations in the GJB2 gene are known to represent the commonest cause of hereditary and congenital hearing loss. In this study, a complete sequencing of the GJB2 gene in a cohort of 506 patients from a single, large cochlear implant program in Europe was performed. Audiological testing for those patients who could actively participate was performed using pure tone audiometry (PTA). Those unable to undergo PTA were measured using click-auditory brainstem response (ABR). Data analysis was performed to determine genotype-phenotype correlations of the mutational status vs. audiological profiles and vs. age at the time of presentation. An overall prevalence of biallelic mutations of 13.4% was found for the total collective. When subsets of younger patients were examined, the prevalence increased to 27% of those up to age 18 and 35% of those up to age 5 at the time of testing, respectively. This increase was found to be highly significant (p < 0.001). Analysis of the mean PTA thresholds revealed a strong correlation between allele combination status and mean PTA (p = 0.021). The prevalence of simple heterozygotes was found to be approximately 10.1%, which is around 3.3 times the value expected in the general population. As GJB2 follows a recessive pattern of inheritance, the question arises as to why such a large fraction of simple heterozygotes was observed among the hearing impaired patients included in this study.
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Affiliation(s)
- W F Burke
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany; Cluster of Excellence, Hearing4All, Germany.
| | - A Warnecke
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany; Cluster of Excellence, Hearing4All, Germany
| | - A Schöner-Heinisch
- Institute for Human Genetics, Hannover Medical School, Hannover, Germany
| | | | - H Maier
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany; Cluster of Excellence, Hearing4All, Germany
| | - T Lenarz
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany; Cluster of Excellence, Hearing4All, Germany
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33
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Ceriani F, Ciubotaru CD, Bortolozzi M, Mammano F. Design and Construction of a Cost-Effective Spinning Disk System for Live Imaging of Inner Ear Tissue. Methods Mol Biol 2016; 1427:223-241. [PMID: 27259930 DOI: 10.1007/978-1-4939-3615-1_13] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Confocal imaging of fluorescent probes offers a powerful, non-invasive tool which enables data collection from vast population of cells at high spatial and temporal resolution. Spinning disk confocal microscopy parallelizes the imaging process permitting the study of dynamic events in populations of living cells on the millisecond time scale. Several spinning disk microscopy solutions are commercially available, however these are often poorly configurable and relatively expensive. This chapter describes a procedure to assemble a cost-effective homemade spinning disk system for fluorescence microscopy, which is highly flexible and easily configurable. We finally illustrate a reliable protocol to obtain high-quality Ca(2+) and voltage imaging data from cochlear preparations.
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Affiliation(s)
- Federico Ceriani
- Department of Physics and Astronomy, University of Padua, via Marzolo 8, Padua, 35131, Italy
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine (VIMM), via G. Orus 2, Padua, 35129, Italy
- CNR, Institute of Cell Biology and Neurobiology, via E. Ramarini 32, Monterotondo, RM, 00015, Italy
| | | | - Mario Bortolozzi
- Department of Physics and Astronomy, University of Padua, via Marzolo 8, Padua, 35131, Italy.
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine (VIMM), via G. Orus 2, Padua, 35129, Italy.
- CNR, Institute of Cell Biology and Neurobiology, via E. Ramarini 32, Monterotondo, RM, 00015, Italy.
| | - Fabio Mammano
- Department of Physics and Astronomy, University of Padua, via Marzolo 8, Padua, 35131, Italy
- Foundation for Advanced Biomedical Research, Venetian Institute of Molecular Medicine (VIMM), via G. Orus 2, Padua, 35129, Italy
- CNR, Institute of Cell Biology and Neurobiology, via E. Ramarini 32, Monterotondo, RM, 00015, Italy
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Abstract
Gene silencing by small interfering RNA (SiRNA) is an attractive therapeutic approach for pathological disorders that targets a specific gene. However, its applications are limited, as naked RNA is rapidly degraded by RNases and is inadequately internalized by the target cells in the body. Several viral and nonviral vectors have been described to improve the delivery of SiRNAs both in cultured cells as well as in vivo. Increasing evidence suggests that cell-penetrating peptides (CPPs) are an efficient, non-cytotoxic tool for intracellular delivery of SiRNA. Recently, a new peptide, PepFect6 (PF6), based system has been described for efficient SiRNA delivery in various cell types. PF6 is an amphipathic stearyl-TP10 peptide carrying a pH titratable trifluoromethylquinoline moiety that facilitate endosomal release. PF6 forms stable non-covalent complexes with SiRNA. Upon internalization, the complexes rapidly escape the endosomal compartment, resulting in robust RNA interference (RNAi) responses. This chapter describes a protocol to use the PF6-nanoparticle technology for SiRNA delivery into organotypic cultures of the inner ear i.e., cochlea. We also highlight different critical points in the peptide/SiRNA complex preparation, transfection and in analyzing the efficacy of PF6-SiRNA associated RNAi response.
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Affiliation(s)
- Suvarna Dash-Wagh
- Department of Neuroscience, Karolinska Institutet, Retzeus väg 8, Stockholm, 17177, Sweden.
| | - Ülo Langel
- Department of Neurochemistry, Stockholm University, Stockholm, 10691, Sweden
| | - Mats Ulfendahl
- Department of Neuroscience, Karolinska Institutet, Retzeus väg 8, Stockholm, 17177, Sweden
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35
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Zheng J, Ying Z, Cai Z, Sun D, He Z, Gao Y, Zhang T, Zhu Y, Chen Y, Guan MX. GJB2 Mutation Spectrum and Genotype-Phenotype Correlation in 1067 Han Chinese Subjects with Non-Syndromic Hearing Loss. PLoS One 2015; 10:e0128691. [PMID: 26043044 PMCID: PMC4456361 DOI: 10.1371/journal.pone.0128691] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 04/29/2015] [Indexed: 11/17/2022] Open
Abstract
Mutations in Gap Junction Beta 2 (GJB2) have been reported to be a major cause of non-syndromic hearing loss in many populations worldwide. The spectrums and frequencies of GJB2 variants vary substantially among different ethnic groups, and the genotypes among these populations remain poorly understood. In the present study, we carried out a systematic and extended mutational screening of GJB2 gene in 1067 Han Chinese subjects with non-syndromic hearing loss, and the resultant GJB2 variants were evaluated by phylogenetic, structural and bioinformatic analysis. A total of 25 (23 known and 2 novel) GJB2 variants were identified, including 6 frameshift mutations, 1 nonsense mutation, 16 missense mutations and 2 silent mutations. In this cohort, c.235delC is the most frequently observed pathogenic mutation. The phylogenetic, structural and bioinformatic analysis showed that 2 novel variants c.127G>T (p.V43L), c.293G>C (p.R98P) and 2 known variants c. 107T>C (p.L36P) and c.187G>T (p.V63L) are localized at highly conserved amino acids. In addition, these 4 mutations are absent in 203 healthy individuals, therefore, they are probably the most likely candidate pathogenic mutations. In addition, 66 (24 novel and 42 known) genotypes were identified, including 6 homozygotes, 20 compound heterozygotes, 18 single heterozygotes, 21 genotypes harboring only polymorphism(s) and the wild type genotype. Among these, 153 (14.34%) subjects were homozygous for pathogenic mutations, 63 (5.91%) were compound heterozygotes, and 157 (14.71%) carried single heterozygous mutation. Furthermore, 65.28% (141/216) of these cases with two pathogenic mutations exhibited profound hearing loss. These data suggested that mutations in GJB2 gene are responsible for approximately 34.96% of non-syndromic hearing loss in Han Chinese population from Zhejiang Province in eastern China. In addition, our results also strongly supported the idea that other factors such as alterations in regulatory regions, additional genes, and environmental factors may contribute to the clinical manifestation of deafness.
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Affiliation(s)
- Jing Zheng
- Institute of Genetics, School of Medicine, Zhejiang University, Hangzhou, China
| | - Zhengbiao Ying
- Department of Otolaryngology, Wenling People’s Hospital, Wenzhou Medical University, Taizhou, China
| | - Zhaoyang Cai
- Department of Otolaryngology, Wenling People’s Hospital, Wenzhou Medical University, Taizhou, China
| | - Dongmei Sun
- Department of Laboratory Medicine, Jinhua Municipal Central Hospital, Jinhua, China
| | - Zheyun He
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China
| | - Yinglong Gao
- Attardi Institute of Mitochondrial Biomedicine, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China
| | - Ting Zhang
- Department of Otolaryngology, Wenling People’s Hospital, Wenzhou Medical University, Taizhou, China
| | - Yi Zhu
- Department of Otolaryngology, the First Affiliated Hospital, Wenzhou Medical University, Wenzhou, China
| | - Ye Chen
- Institute of Genetics, School of Medicine, Zhejiang University, Hangzhou, China
- Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou, China
| | - Min-Xin Guan
- Institute of Genetics, School of Medicine, Zhejiang University, Hangzhou, China
- Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou, China
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36
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Liu WJ, Yang J. Developmental expression of inositol 1, 4, 5-trisphosphate receptor in the post-natal rat cochlea. Eur J Histochem 2015; 59:2486. [PMID: 26150157 PMCID: PMC4503970 DOI: 10.4081/ejh.2015.2486] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 04/06/2015] [Accepted: 04/06/2015] [Indexed: 11/23/2022] Open
Abstract
Inositol 1, 4, 5-trisphosphate receptor (IP3R) has been established to be essential for hearing. However, the expression of IP3R in the cochlea in the period of auditory development remains unknown. We investigated the expression of IP3R in the developing rat cochlea using immunohistochemistry and real-time reverse transcription polymerase chain reaction (RT-PCR). We observed its presence in the developing rat cochlea, and changes in IP3R protein expressions from the early post-natal period to adult. At birth (post-natal day 0, P0), IP3R expression was only found in Hensen's cell. IP3R immunoreactivity first appeared in the sensory hair cells in the organ of Corti at P2. This localization was confirmed by means of double-labeling experiments with Myosin VIIA, a marker for cochlear hair cells. Colocalization of IP3R and Myosin VIIA from P2 to the second post-natal week suggested early expression of IP3R in developing inner and outer hair cells. Claudius' cells near the spiral ligament were labelled for IP3R from P8 onwards. Transient IP3R expression was observed in the stria vascularis in early post-natal rat from P4 to P8. Spiral ganglion neurons also exhibited weaker IP3R fluorescence signals during post-natal development. The results of RT-PCR demonstrated that all three IP3R isoforms (IP3R1, IP3R2, and IP3R3) were present in rat cochlea during four different developmental stages of cochlea, from P0 to P28. Present immunohistochemical evidence for both change and maintenance of expression of IP3R during post-natal development of the rat cochlea indicated the possible involvement of IP3R-mediated calcium signaling in cochlear development.
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Affiliation(s)
- W J Liu
- Shanghai Jiaotong University.
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37
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Sanchez HA, Verselis VK. Aberrant Cx26 hemichannels and keratitis-ichthyosis-deafness syndrome: insights into syndromic hearing loss. Front Cell Neurosci 2014; 8:354. [PMID: 25386120 PMCID: PMC4209889 DOI: 10.3389/fncel.2014.00354] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 10/08/2014] [Indexed: 02/01/2023] Open
Abstract
Mutation of the GJB2 gene, which encodes the connexin 26 (Cx26) gap junction (GJ) protein, is the most common cause of hereditary, sensorineural hearing loss. Cx26 is not expressed in hair cells, but is widely expressed throughout the non-sensory epithelial cells of the cochlea. Most GJB2 mutations produce non-syndromic deafness, but a subset produces syndromic deafness in which profound hearing loss is accompanied by a diverse array of infectious and neoplastic cutaneous disorders that can be fatal. Although GJ channels, which are assembled by the docking of two, so-called hemichannels (HCs), have been the main focus of deafness-associated disease models, it is now evident that the HCs themselves can function in the absence of docking and contribute to signaling across the cell membrane as a novel class of ion channel. A notable feature of syndromic deafness mutants is that the HCs exhibit aberrant behaviors providing a plausible basis for disease that is associated with excessive or altered contributions of Cx26 HCs that, in turn, lead to compromised cell integrity. Here we discuss some of the aberrant Cx26 HC properties that have been described for mutants associated with keratitis-ichthyosis-deafness (KID) syndrome, a particularly severe Cx26-associated syndrome, which shed light on genotype-phenotype relationships and causes underlying cochlear dysfunction.
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Affiliation(s)
- Helmuth A Sanchez
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine Bronx, NY, USA
| | - Vytas K Verselis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine Bronx, NY, USA
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38
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Stewart MKG, Plante I, Bechberger JF, Naus CC, Laird DW. Mammary gland specific knockdown of the physiological surge in Cx26 during lactation retains normal mammary gland development and function. PLoS One 2014; 9:e101546. [PMID: 24988191 PMCID: PMC4079510 DOI: 10.1371/journal.pone.0101546] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Accepted: 06/08/2014] [Indexed: 12/17/2022] Open
Abstract
Connexin26 (Cx26) is the major Cx protein expressed in the human mammary gland and is up-regulated during pregnancy while remaining elevated throughout lactation. It is currently unknown if patients with loss-of-function Cx26 mutations that result in hearing loss and skin diseases have a greater susceptibility to impaired breast development. To investigate if Cx26 plays a critical role in mammary gland development and differentiation, a novel Cx26 conditional knockout mouse model was generated by crossing Cx26fl/fl mice with mice expressing Cre under the β-Lactoglobulin promoter. Conditional knockdown of Cx26 from the mammary gland resulted in a dramatic reduction in detectable gap junction plaques confirmed by a significant ∼65-70% reduction in Cx26 mRNA and protein throughout parturition and lactation. Interestingly, this reduction was accompanied by a decrease in mammary gland Cx30 gap junction plaques at parturition, while no change was observed for Cx32 or Cx43. Whole mount, histological and immunofluorescent assessment of breast tissue revealed comparatively normal lobuloalveolar development following pregnancy in the conditionally knockdown mice compared to control mice. In addition, glands from genetically-modified mice were capable of producing milk proteins that were evident in the lumen of alveoli and ducts at similar levels as controls, suggesting normal gland function. Together, our results suggest that low levels of Cx26 expression throughout pregnancy and lactation, and not the physiological surge in Cx26, is sufficient for normal gland development and function.
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Affiliation(s)
- Michael K G Stewart
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | | | - John F Bechberger
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christian C Naus
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Dale W Laird
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada; Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
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39
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Genetics of auditory mechano-electrical transduction. Pflugers Arch 2014; 467:49-72. [PMID: 24957570 PMCID: PMC4281357 DOI: 10.1007/s00424-014-1552-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 06/04/2014] [Accepted: 06/05/2014] [Indexed: 12/29/2022]
Abstract
The hair bundles of cochlear hair cells play a central role in the auditory mechano-electrical transduction (MET) process. The identification of MET components and of associated molecular complexes by biochemical approaches is impeded by the very small number of hair cells within the cochlea. In contrast, human and mouse genetics have proven to be particularly powerful. The study of inherited forms of deafness led to the discovery of several essential proteins of the MET machinery, which are currently used as entry points to decipher the associated molecular networks. Notably, MET relies not only on the MET machinery but also on several elements ensuring the proper sound-induced oscillation of the hair bundle or the ionic environment necessary to drive the MET current. Here, we review the most significant advances in the molecular bases of the MET process that emerged from the genetics of hearing.
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40
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Yi E, Lee J, Lee CJ. Developmental Role of Anoctamin-1/TMEM16A in Ca(2+)-Dependent Volume Change in Supporting Cells of the Mouse Cochlea. Exp Neurobiol 2013; 22:322-9. [PMID: 24465148 PMCID: PMC3897694 DOI: 10.5607/en.2013.22.4.322] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 12/14/2013] [Accepted: 12/14/2013] [Indexed: 11/19/2022] Open
Abstract
Mammalian cochlea undergoes morphological and functional changes during the postnatal period, around the hearing onset. Major changes during the initial 2 postnatal weeks of mouse include maturation of sensory hair cells and supporting cells, and acquisition of afferent and efferent innervations. During this period, supporting cells in the greater epithelial ridge (GER) of the cochlea exhibit spontaneous and periodic activities which involves ATP, increase in intracellular Ca(2+), and cell volume change. This Ca(2+)-dependent volume change has been proposed to involve chloride channels or transporters. We found that the spontaneous volume changes were eliminated by anion channel blocker, 100 µM NPPB. Among candidates, expression of Anoctamin-1 (Ano1 or TMEM16A), bestriphin-1 and NKCC1 were investigated in whole-mount cochlea of P9-10 mice. Immunolabeling indicated high level of Ano1 expression in the GER, but not of betrophin-1 or NKCC1. Double-labeling with calretinin and confocal image analysis further elucidated the cellular localization of Ano1 immunoreactivity in supporting cells. It was tested if the Ano1 expression exhibits similar time course to the spontaneous activities in postnatal cochlear supporting cells. Cochlear preparations from P2-3, P5-6, P9-10, P15-16 mice were subjected to immunolabeling. High level of Ano1 immunoreactivity was observed in the GER of P2-3, P5-6, P9-10 cochleae, but not of P15-17 cochleae. Taken together, the localization and time course in Ano1 expression pattern correlates with the spontaneous, periodic volume changes recorded in postnatal cochlear supporting cells. From these results we propose that Ano1 is the pacemaker of spontaneous activities in postnatal cochlea.
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Affiliation(s)
- Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 534-729, Korea
| | - Jaekwang Lee
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology, Seoul 136-791, Korea
| | - C Justin Lee
- WCI Center for Functional Connectomics, Korea Institute of Science and Technology, Seoul 136-791, Korea. ; KU-KIST Graduate School of Converging Science & Techonology, Korea University, Seoul 136-790, Korea
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Ceriani F, Mammano F. A rapid and sensitive assay of intercellular coupling by voltage imaging of gap junction networks. Cell Commun Signal 2013; 11:78. [PMID: 24144139 PMCID: PMC3819673 DOI: 10.1186/1478-811x-11-78] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 10/01/2013] [Indexed: 12/16/2022] Open
Abstract
Background A variety of mechanisms that govern connexin channel gating and permeability regulate coupling in gap junction networks. Mutations in connexin genes have been linked to several pathologies, including cardiovascular anomalies, peripheral neuropathy, skin disorders, cataracts and deafness. Gap junction coupling and its patho–physiological alterations are commonly assayed by microinjection experiments with fluorescent tracers, which typically require several minutes to allow dye transfer to a limited number of cells. Comparable or longer time intervals are required by fluorescence recovery after photobleaching experiments. Paired electrophysiological recordings have excellent time resolution but provide extremely limited spatial information regarding network connectivity. Results Here, we developed a rapid and sensitive method to assay gap junction communication using a combination of single cell electrophysiology, large–scale optical recordings and a digital phase–sensitive detector to extract signals with a known frequency from Vf2.1.Cl, a novel fluorescent sensor of plasma membrane potential. Tests performed in HeLa cell cultures confirmed that suitably encoded Vf2.1.Cl signals remained confined within the network of cells visibly interconnected by fluorescently tagged gap junction channels. We used this method to visualize instantly intercellular connectivity over the whole field of view (hundreds of cells) in cochlear organotypic cultures from postnatal mice. A simple resistive network model reproduced accurately the spatial dependence of the electrical signals throughout the cellular network. Our data suggest that each pair of cochlear non−sensory cells of the lesser epithelial ridge is coupled by ~1500 gap junction channels, on average. Junctional conductance was reduced by 14% in cochlear cultures harboring the T5M mutation of connexin30, which induces a moderate hearing loss in connexin30T5M/T5M knock–in mice, and by 91% in cultures from connexin30−/− mice, which are profoundly deaf. Conclusions Our methodology allows greater sensitivity (defined as the minimum magnitude of input signal required to produce a specified output signal having a specified signal−to−noise ratio) and better time resolution compared to classical tracer–based techniques. It permitted us to dynamically visualize intercellular connectivity down to the 10th order in non−sensory cell networks of the developing cochlea. We believe that our approach is of general interest and can be seamlessly extended to a variety of biological systems, as well as to other connexin−related disease conditions.
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Affiliation(s)
| | - Fabio Mammano
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, Padova 35131, Italy.
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Abstract
Gjb2 and Gjb6, two contiguous genes respectively encoding the gap junction protein connexin26 (Cx26) and connexin 30 (Cx30) display overlapping expression in the inner ear. Both have been linked to the most frequent monogenic hearing impairment, the recessive isolated deafness DFNB1. Although there is robust evidence for the direct involvement of Cx26 in cochlear functions, the contribution of Cx30 is unclear since deletion of Cx30 strongly downregulates Cx26 both in human and in mouse. Thus, it is imperative that any role of Cx30 in audition be clearly evaluated. Here, we developed a new Cx30 knock-out mouse model (Cx30(Δ/Δ)) in which half of Cx26 expression was preserved. Our results show that Cx30 and Cx26 coordinated expression is dependent on the spacing of their surrounding chromosomic region, and that Cx30(Δ/Δ) mutants display normal hearing. Thus, in deaf patients with GJB6 deletion as well as in the previous Cx30 knock-out mouse model, defective Cx26 expression is the likely cause of deafness, and in contrast to current opinion, Cx30 is dispensable for cochlear functions.
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Gialluisi A, Dediu D, Francks C, Fisher SE. Persistence and transmission of recessive deafness and sign language: new insights from village sign languages. Eur J Hum Genet 2013; 21:894-6. [PMID: 23321624 DOI: 10.1038/ejhg.2012.292] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Forge A, Jagger DJ, Kelly JJ, Taylor RR. Connexin30 mediated intercellular communication plays an essential role in epithelial repair in the cochlea. J Cell Sci 2013; 126:1703-12. [DOI: 10.1242/jcs.125476] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A role for connexin (Cx) 30 in epithelial repair following injury was examined in the organ of Corti, the sensory epithelium of the cochlea. In this tissue, lesions caused by loss of the sensory hair cells are closed by the supporting cells that surround each one. Gap junctions in which Cx30 is the predominant connexin are large and numerous between supporting cells. In mice carrying a deletion in the gene (Gjb6) that encodes Cx30, the size and number of gap junction plaques, and the extent of dye transfer, between supporting cells was greatly reduced compared with normal animals. This corresponded with unique peculiarities of the lesion closure events during the progressive hair cell loss that occurs in these animals in comparison with other models of hair cell loss whether acquired or as a result of a mutation. Only one, rather than all, of the supporting cells that contacted an individual dying hair closed the lesion, indicating disturbance of the co-ordination of cellular responses. The cell shape changes that the supporting cells normally undergo during repair of the organ of Corti did not occur, and there was disruption of the migratory activities that normally lead to the replacement of a columnar epithelium with a squamous-like one. These observations demonstrate a role for Cx30 and intercellular communication in regulating repair responses in an epithelial tissue.
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Dash-Wagh S, Jacob S, Lindberg S, Fridberger A, Langel U, Ulfendahl M. Intracellular Delivery of Short Interfering RNA in Rat Organ of Corti Using a Cell-penetrating Peptide PepFect6. MOLECULAR THERAPY. NUCLEIC ACIDS 2012; 1:e61. [PMID: 23232329 PMCID: PMC3528302 DOI: 10.1038/mtna.2012.50] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
RNA interference (RNAi) using short interfering RNA (siRNA) is an attractive therapeutic approach for treatment of dominant-negative mutations. Some rare missense dominant-negative mutations lead to congenital-hearing impairments. A variety of viral vectors have been tested with variable efficacy for modulating gene expression in inner ear. However, there is concern regarding their safety for clinical use. Here, we report a novel cell-penetrating peptide (CPP)-based nonviral approach for delivering siRNA into inner ear tissue using organotypic cultures as model system. PepFect6 (PF6), a variant of stearyl-TP10, was specially designed for improved delivery of siRNA by facilitating endosomal release. We show that PF6 was internalized by all cells without inducing cytotoxicity in cochlear cultures. PF6/siRNA nanoparticles lead to knockdown of target genes, a housekeeping gene and supporting cell-specific connexin 26. Interestingly, application of PF6/connexin 26 siRNA exhibited knockdown of both connexin 26 and 30 mRNA and their absence led to impaired intercellular communication as demonstrated by reduced transfer of calcein among the PF6/connexin 26-siRNA–treated cells. Thus, we conclude that PF6 is an efficient nonviral vector for delivery of siRNA, which can be applied as a tool for the development of siRNA-based therapeutic applications for hearing impairments.
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Affiliation(s)
- Suvarna Dash-Wagh
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Mammano F. ATP-dependent intercellular Ca2+ signaling in the developing cochlea: facts, fantasies and perspectives. Semin Cell Dev Biol 2012; 24:31-9. [PMID: 23022499 DOI: 10.1016/j.semcdb.2012.09.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 09/14/2012] [Indexed: 10/27/2022]
Abstract
Hearing relies on a sensitive mechanoelectrical transduction process in the cochlea of the inner ear. The cochlea contains sensory, secretory, neural, supporting and epithelial cells which are all essential to the sound transduction process. It is well known that a complex extracellular purinergic signaling system contributes to cochlear homeostasis, altering cochlear sensitivity and neural output via ATP-gated ion channels (P2X receptors) and G protein-coupled P2Y receptors. This review focuses on the emerging roles of ATP that are currently under investigation in the developing sensory epithelium, with particular emphasis on the link between ATP release, Ca(2+) signaling, the expression and function of gap junction proteins connexin26 and connexin30, and the acquisition of hearing.
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Affiliation(s)
- Fabio Mammano
- Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova, 35131 Padova, Italy.
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Reduced phosphatidylinositol 4,5-bisphosphate synthesis impairs inner ear Ca2+ signaling and high-frequency hearing acquisition. Proc Natl Acad Sci U S A 2012; 109:14013-8. [PMID: 22891314 DOI: 10.1073/pnas.1211869109] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Phosphatidylinositol phosphate kinase type 1γ (PIPKIγ) is a key enzyme in the generation of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] and is expressed at high levels in the nervous system. Homozygous knockout mice lacking this enzyme die postnatally within 24 h, whereas PIPKIγ(+/-) siblings breed normally and have no reported phenotype. Here we show that adult PIPKIγ(+/-) mice have dramatically elevated hearing thresholds for high-frequency sounds. During the first postnatal week we observed a reduction of ATP-dependent Ca(2+) signaling activity in cochlear nonsensory cells. Because Ca(2+) signaling under these conditions depends on inositol-1,4,5-trisphosphate generation from phospholipase C (PLC)-dependent hydrolysis of PI(4,5)P(2), we conclude that (i) PIPKIγ is primarily responsible for the synthesis of the receptor-regulated PLC-sensitive PI(4,5)P(2) pool in the cell syncytia that supports auditory hair cells; (ii) spatially graded impairment of this signaling pathway in cochlear nonsensory cells causes a selective alteration in the acquisition of hearing in PIPKIγ(+/-) mice. This mouse model also suggests that PIPKIγ may determine the level of gap junction contribution to cochlear development.
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Xu J, Nicholson BJ. The role of connexins in ear and skin physiology - functional insights from disease-associated mutations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:167-78. [PMID: 22796187 DOI: 10.1016/j.bbamem.2012.06.024] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Revised: 06/23/2012] [Accepted: 06/29/2012] [Indexed: 12/20/2022]
Abstract
Defects in several different connexins have been associated with several different diseases. The most common of these is deafness, where a few mutations in connexin (Cx) 26 have been found to contribute to over 50% of the incidence of non-syndromic deafness in different human populations. Other mutations in Cx26 or Cx30 have also been associated with various skin phenotypes linked to deafness (palmoplanta keratoderma, Bart-Pumphrey syndrome, Vohwinkel syndrome, keratitis-ichthyosis-deafness syndrome, etc.). The large array of disease mutants offers unique opportunities to gain insights into the underlying function of gap junction proteins and their channels in the normal and pathogenic physiologies of the cochlea and epidermis. This review focuses on those mutants where the impact on channel function has been assessed, and correlated with the disease phenotype, or organ function in knock-out mouse models. These approaches have provided evidence supporting a role of gap junctions and hemichannels in K(+) removal and recycling in the ear, as well as possible roles for nutrient passage, in the cochlea. In contrast, increases in hemichannel opening leading to increased cell death, were associated with several keratitis-ichthyosis-deafness syndrome skin disease/hearing mutants. In addition to providing clues for therapeutic strategies, these findings allow us to better understand the specific functions of connexin channels that are important for normal tissue function. This article is part of a Special Issue entitled: The communicating junctions, roles and dysfunctions.
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Affiliation(s)
- Ji Xu
- Department of Physiology, University of California, Los Angeles, CA 90095, USA
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Wang N, De Bock M, Decrock E, Bol M, Gadicherla A, Vinken M, Rogiers V, Bukauskas FF, Bultynck G, Leybaert L. Paracrine signaling through plasma membrane hemichannels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:35-50. [PMID: 22796188 DOI: 10.1016/j.bbamem.2012.07.002] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 06/29/2012] [Accepted: 07/06/2012] [Indexed: 12/24/2022]
Abstract
Plasma membrane hemichannels composed of connexin (Cx) proteins are essential components of gap junction channels but accumulating evidence suggests functions of hemichannels beyond the communication provided by junctional channels. Hemichannels not incorporated into gap junctions, called unapposed hemichannels, can open in response to a variety of signals, electrical and chemical, thereby forming a conduit between the cell's interior and the extracellular milieu. Open hemichannels allow the bidirectional passage of ions and small metabolic or signaling molecules of below 1-2kDa molecular weight. In addition to connexins, hemichannels can also be formed by pannexin (Panx) proteins and current evidence suggests that Cx26, Cx32, Cx36, Cx43 and Panx1, form hemichannels that allow the diffusive release of paracrine messengers. In particular, the case is strong for ATP but substantial evidence is also available for other messengers like glutamate and prostaglandins or metabolic substances like NAD(+) or glutathione. While this field is clearly in expansion, evidence is still lacking at essential points of the paracrine signaling cascade that includes not only messenger release, but also downstream receptor signaling and consequent functional effects. The data available at this moment largely derives from in vitro experiments and still suffers from the difficulty of separating the functions of connexin-based hemichannels from gap junctions and from pannexin hemichannels. However, messengers like ATP or glutamate have universal roles in the body and further defining the contribution of hemichannels as a possible release pathway is expected to open novel avenues for better understanding their contribution to a variety of physiological and pathological processes. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.
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Affiliation(s)
- Nan Wang
- Department of Basic Medical Sciences, Ghent University, Ghent, Belgium
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Ceriani F, Mammano F. Calcium signaling in the cochlea - Molecular mechanisms and physiopathological implications. Cell Commun Signal 2012; 10:20. [PMID: 22788415 PMCID: PMC3408374 DOI: 10.1186/1478-811x-10-20] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/12/2012] [Indexed: 12/20/2022] Open
Abstract
Calcium ions (Ca2+) regulate numerous and diverse aspects of cochlear and vestibular physiology. This review focuses on the Ca2+ control of mechanotransduction and synaptic transmission in sensory hair cells, as well as on Ca2+ signalling in non-sensory cells of the developing cochlea.
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Affiliation(s)
- Federico Ceriani
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, 35131, Padova, Italy.
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