1
|
Murtaza M, Zargar MH, Ali O, Khan IS, Ali MN. Spectrum and frequency of connexin 26 & connexin 30 gene mutations in patients with congenital hearing loss from Ladakh India. Meta Gene 2021. [DOI: 10.1016/j.mgene.2021.100960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
|
2
|
Liu W, Glueckert R, Schrott-Fischer A, Rask-Andersen H. Human cochlear microanatomy – an electron microscopy and super-resolution structured illumination study and review. HEARING BALANCE AND COMMUNICATION 2020. [DOI: 10.1080/21695717.2020.1807259] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Wei Liu
- Department of Surgical Sciences, Head and Neck Surgery, section of Otolaryngology, Uppsala University Hospital, Department of Otolaryngology, Uppsala University Hospital, Uppsala, Sweden
| | - Rudolf Glueckert
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | | | - Helge Rask-Andersen
- Department of Surgical Sciences, Head and Neck Surgery, section of Otolaryngology, Uppsala University Hospital, Department of Otolaryngology, Uppsala University Hospital, Uppsala, Sweden
| |
Collapse
|
3
|
Berekméri E, Fekete Á, Köles L, Zelles T. Postnatal Development of the Subcellular Structures and Purinergic Signaling of Deiters' Cells along the Tonotopic Axis of the Cochlea. Cells 2019; 8:cells8101266. [PMID: 31627326 PMCID: PMC6830339 DOI: 10.3390/cells8101266] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 10/03/2019] [Accepted: 10/15/2019] [Indexed: 01/04/2023] Open
Abstract
Exploring the development of the hearing organ helps in the understanding of hearing and hearing impairments and it promotes the development of the regenerative approaches-based therapeutic efforts. The role of supporting cells in the development of the organ of Corti is much less elucidated than that of the cochlear sensory receptor cells. The use of our recently published method of single-cell electroporation loading of a fluorescent Ca2+ probe in the mouse hemicochlea preparation provided an appropriate means to investigate the Deiters’ cells at the subcellular level in two different cochlear turns (apical, middle). Deiters’ cell’s soma and process elongated, and the process became slimmer by maturation without tonotopic preference. The tonotopically heterogeneous spontaneous Ca2+ activity less frequently occurred by maturation and implied subcellular difference. The exogenous ATP- and UTP-evoked Ca2+ responses were maturation-dependent and showed P2Y receptor dominance in the apical turn. By monitoring the basic structural dimensions of this supporting cell type as well as its spontaneous and evoked purinergic Ca2+ signaling in the hemicochlea preparation in different stages in the critical postnatal P5-25 developmental period for the first time, we showed that the soma and the phalangeal process of the Deiters’ cells go through age- and tonotopy-dependent changes in the morphometric parameters and purinergic signaling.
Collapse
Affiliation(s)
- Eszter Berekméri
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvárad tér 4., 1089 Budapest, Hungary.
- Department of Ecology, University of Veterinary Medicine, Rottenbiller u. 50., 1077 Budapest, Hungary.
| | - Ádám Fekete
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, 555 University Ave, Toronto, ON M5G 1X8, Canada.
| | - László Köles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvárad tér 4., 1089 Budapest, Hungary.
| | - Tibor Zelles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvárad tér 4., 1089 Budapest, Hungary.
- Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony u. 43., 1083 Budapest, Hungary.
| |
Collapse
|
4
|
Zhou Y, Song J, Wang YP, Zhang AM, Tan CY, Liu YH, Zhang ZP, Wang Y, Ma KT, Li L, Si JQ. Age‑associated variation in the expression and function of TMEM16A calcium‑activated chloride channels in the cochlear stria vascularis of guinea pigs. Mol Med Rep 2019; 20:1593-1604. [PMID: 31257512 PMCID: PMC6625423 DOI: 10.3892/mmr.2019.10423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 05/20/2019] [Indexed: 01/08/2023] Open
Abstract
The present study was designed to investigate the expression and function of transmembrane protein 16 (TMEM16A), a calcium‑activated chloride channel (CaCC), in the stria vascularis (SV) of the cochlea of guinea pigs at different ages, and to understand the role of CaCCs in the pathogenesis of presbycusis (age‑related hearing loss), the most common type of sensorineural hearing loss that occurs with natural aging. Guinea pigs were divided into the following groups: 2 weeks (young group), 3 months (youth group), 1 year (adult group), D‑galactose intervention (D‑gal group; aging model induced by subcutaneous injection of D‑galactose) and T16Ainh‑A01 (intraperitoneal injection of 50 µg/kg/day TMEM16A inhibitor T16Ainh‑A01 for 2 weeks). Differences in the hearing of guinea pigs between the various age groups were analyzed using auditory brainstem response (ABR), and immunofluorescence staining was performed to detect TMEM16A expression in the SV and determine the distribution. Reverse transcription‑quantitative PCR and western blot analyses were conducted to detect the mRNA and protein levels of TMEM16A in SV in the different age groups. Morris water maze behavior analysis demonstrated that spatial learning ability and memory were damaged in the D‑gal group. Superoxide dismutase activity and malondialdehyde content assays indicated that there was oxidative stress damage in the D‑gal group. The ABR thresholds gradually increased with age, and the increase in the T16Ainh‑A01 group was pronounced. Immunofluorescence analysis in the cochlear SV of guinea pigs in different groups revealed that expression of TMEM16A increased with increasing age (2 weeks to 1 year); fluorescence intensity was reduced in the D‑gal model of aging. As the guinea pigs continued to mature, the protein and mRNA contents of TMEM16A in the cochlea SV increased gradually, but were decreased in the D‑gal group. The findings indicated that CaCCs in the cochlear SV of guinea pigs were associated with the development of hearing in guinea pigs, and that downregulation of TMEM16A may be associated with age‑associated hearing loss.
Collapse
Affiliation(s)
- Ying Zhou
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Jia Song
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Yan-Ping Wang
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Ai-Mei Zhang
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Chao-Yang Tan
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Yan-Hui Liu
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Zhi-Ping Zhang
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Yang Wang
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Ke-Tao Ma
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Li Li
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Jun-Qiang Si
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| |
Collapse
|
5
|
Köles L, Szepesy J, Berekméri E, Zelles T. Purinergic Signaling and Cochlear Injury-Targeting the Immune System? Int J Mol Sci 2019; 20:ijms20122979. [PMID: 31216722 PMCID: PMC6627352 DOI: 10.3390/ijms20122979] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 06/14/2019] [Accepted: 06/14/2019] [Indexed: 02/06/2023] Open
Abstract
Hearing impairment is the most common sensory deficit, affecting more than 400 million people worldwide. Sensorineural hearing losses currently lack any specific or efficient pharmacotherapy largely due to the insufficient knowledge of the pathomechanism. Purinergic signaling plays a substantial role in cochlear (patho)physiology. P2 (ionotropic P2X and the metabotropic P2Y) as well as adenosine receptors expressed on cochlear sensory and non-sensory cells are involved mostly in protective mechanisms of the cochlea. They are implicated in the sensitivity adjustment of the receptor cells by a K+ shunt and can attenuate the cochlear amplification by modifying cochlear micromechanics. Cochlear blood flow is also regulated by purines. Here, we propose to comprehend this field with the purine-immune interactions in the cochlea. The role of harmful immune mechanisms in sensorineural hearing losses has been emerging in the horizon of cochlear pathologies. In addition to decreasing hearing sensitivity and increasing cochlear blood supply, influencing the immune system can be the additional avenue for pharmacological targeting of purinergic signaling in the cochlea. Elucidating this complexity of purinergic effects on cochlear functions is necessary and it can result in development of new therapeutic approaches in hearing disabilities, especially in the noise-induced ones.
Collapse
Affiliation(s)
- László Köles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary.
| | - Judit Szepesy
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary.
| | - Eszter Berekméri
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary.
- Department of Ecology, University of Veterinary Medicine, H-1078 Budapest, Hungary.
| | - Tibor Zelles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary.
- Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, H-1083 Budapest, Hungary.
| |
Collapse
|
6
|
Liu W, Schrott-Fischer A, Glueckert R, Benav H, Rask-Andersen H. The Human "Cochlear Battery" - Claudin-11 Barrier and Ion Transport Proteins in the Lateral Wall of the Cochlea. Front Mol Neurosci 2017; 10:239. [PMID: 28848383 PMCID: PMC5554435 DOI: 10.3389/fnmol.2017.00239] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 07/14/2017] [Indexed: 11/21/2022] Open
Abstract
Background: The cochlea produces an electric field potential essential for hair cell transduction and hearing. This biological “battery” is situated in the lateral wall of the cochlea and contains molecular machinery that secretes and recycles K+ ions. Its functioning depends on junctional proteins that restrict the para-cellular escape of ions. The tight junction protein Claudin-11 has been found to be one of the major constituents of this barrier that maintains ion gradients (Gow et al., 2004; Kitajiri et al., 2004a). We are the first to elucidate the human Claudin-11 framework and the associated ion transport machinery using super-resolution fluorescence illumination microscopy (SR-SIM). Methods: Archival cochleae obtained during meningioma surgery were used for SR-SIM together with transmission electron microscopy after ethical consent. Results: Claudin-11-expressing cells formed parallel tight junction lamellae that insulated the epithelial syncytium of the stria vascularis and extended to the suprastrial region. Intercellular gap junctions were found between the barrier cells and fibrocytes. Conclusion: Transmission electron microscopy, confocal microscopy and SR-SIM revealed exclusive cell specialization in the various subdomains of the lateral wall of the human cochlea. The Claudin-11-expressing cells exhibited both conductor and isolator characteristics, and these micro-porous separators may selectively mediate the movement of charged units to the intrastrial space in a manner that is analogous to a conventional electrochemical “battery.” The function and relevance of this battery for the development of inner ear disease are discussed.
Collapse
Affiliation(s)
- Wei Liu
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University HospitalUppsala, Sweden
| | | | - Rudolf Glueckert
- Department of Otolaryngology, Medical University of InnsbruckInnsbruck, Austria
| | | | - Helge Rask-Andersen
- Department of Surgical Sciences, Head and Neck Surgery, Section of Otolaryngology, Uppsala University HospitalUppsala, Sweden
| |
Collapse
|
7
|
ATP-sensitive K(+) channels (Kir6.1/SUR1) regulate gap junctional coupling in cochlear-supporting cells. Pflugers Arch 2016; 468:1215-1222. [PMID: 27030354 DOI: 10.1007/s00424-016-1815-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 03/20/2016] [Accepted: 03/22/2016] [Indexed: 10/22/2022]
Abstract
Using the double whole-cell patch-clamp technique, we found that the absence of intracellular ATP led to gap junction uncoupling in cochlear-supporting Hensen cells. The uncoupling was observed as a progressive reduction of the gap junctional electrical conductance from a starting value of approximately 40 nS to less than 0.04 nS within 10-20 min. The conductance rundown was partly avoided by at least 3 mM ATP and completely suppressed by 5 mM ATP or 5'-adenylyl-imidodiphosphate (AMP-PNP), the non-hydrolysable ATP analog, in the pipette filling solution, suggesting that ATP was needed as ligand and not as a hydrolysable energy supplier or substrate for enzymatic reactions. The effect of intracellular ATP was mimicked by the external application of barium, a nonselective blocker of inwardly rectifying K(+) (Kir) channels, and glibenclamide, an inhibitor of the ATP-sensitive Kir channels (KATP). Moreover a Ba(2+)-sensitive whole-cell inward current was observed in absence of internal ATP. We propose that the internal ATP kept the KATP channels in a closed state, thereby maintaining the gap junction coupling of Hensen cells. The immunostaining of guinea pig cochlear tissue revealed for the first time the expression of the KATP channel subunits Kir6.1 and SUR1 in Hensen cells and supported the proposed hypothesis. The results suggest that KATP channels, as regulator of the gap junction coupling in Hensen cells, could be the physiological link between the metabolic state of the supporting cells and K(+) recycling in the organ of Corti.
Collapse
|
8
|
Han C, Linser P, Park HJ, Kim MJ, White K, Vann JM, Ding D, Prolla TA, Someya S. Sirt1 deficiency protects cochlear cells and delays the early onset of age-related hearing loss in C57BL/6 mice. Neurobiol Aging 2016; 43:58-71. [PMID: 27255815 DOI: 10.1016/j.neurobiolaging.2016.03.023] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 02/29/2016] [Accepted: 03/22/2016] [Indexed: 10/22/2022]
Abstract
Hearing gradually declines with age in both animals and humans, and this condition is known as age-related hearing loss (AHL). Here, we investigated the effects of deficiency of Sirt1, a member of the mammalian sirtuin family, on age-related cochlear pathology and associated hearing loss in C57BL/6 mice, a mouse model of early-onset AHL. Sirt1 deficiency reduced age-related oxidative damage of cochlear hair cells and spiral ganglion neurons and delayed the early onset of AHL. In cultured mouse inner ear cell lines, Sirt1 knockdown increased cell viability under oxidative stress conditions, induced nuclear translocation of Foxo3a, and increased acetylation status of Foxo3a. This resulted in increased activity of the antioxidant enzyme catalase. In young wild-type mice, both Sirt1 and Foxo3a proteins resided in the cytoplasm of the supporting cells within the organ of Corti of the cochlea. Therefore, our findings suggest that SIRT1 promotes early-onset AHL through suppressing FOXO3a-mediated oxidative stress resistance in the cochlea of C57BL/6 mice.
Collapse
Affiliation(s)
- Chul Han
- Department of Aging and Geriatric Research, University of Florida, Gainesville, FL, USA
| | - Paul Linser
- Whitney Laboratory, University of Florida, St Augustine, FL, USA
| | - Hyo-Jin Park
- Department of Neurology, University of Florida, Gainesville, FL, USA
| | - Mi-Jung Kim
- Department of Aging and Geriatric Research, University of Florida, Gainesville, FL, USA
| | - Karessa White
- Department of Aging and Geriatric Research, University of Florida, Gainesville, FL, USA
| | - James M Vann
- Department of Genetics, University of Wisconsin, Madison, WI, USA; Department of Medical Genetics, University of Wisconsin, Madison, WI, USA
| | - Dalian Ding
- Center for Hearing and Deafness, State University of New York at Buffalo, NY, USA
| | - Tomas A Prolla
- Department of Genetics, University of Wisconsin, Madison, WI, USA; Department of Medical Genetics, University of Wisconsin, Madison, WI, USA
| | - Shinichi Someya
- Department of Aging and Geriatric Research, University of Florida, Gainesville, FL, USA.
| |
Collapse
|
9
|
Tayoun ANA, Mason-Suares H, Frisella AL, Bowser M, Duffy E, Mahanta L, Funke B, Rehm HL, Amr SS. Targeted Droplet-Digital PCR as a Tool for Novel Deletion Discovery at the DFNB1 Locus. Hum Mutat 2015; 37:119-26. [DOI: 10.1002/humu.22912] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 09/21/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Ahmad N. Abou Tayoun
- Harvard Medical School Genetics Training Program; Harvard; Cambridge MA
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
- Division of Genomic Diagnostics; The Children's Hospital of Philadelphia; The University of Pennsylvania Perelman School of Medicine; PA
| | - Heather Mason-Suares
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
- Department of Pathology; Brigham and Women's Hospital; Harvard Medical School; Boston MA
| | - Ashley L. Frisella
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
| | - Mark Bowser
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
| | - Elizabeth Duffy
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
| | - Lisa Mahanta
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
| | - Birgit Funke
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
- Department of Pathology; Brigham and Women's Hospital; Harvard Medical School; Boston MA
| | - Heidi L. Rehm
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
- Department of Pathology; Brigham and Women's Hospital; Harvard Medical School; Boston MA
| | - Sami S. Amr
- Laboratory for Molecular Medicine; Partners Healthcare Personalized Medicine; Cambridge MA
- Department of Pathology; Brigham and Women's Hospital; Harvard Medical School; Boston MA
| |
Collapse
|
10
|
Lee MY, Takada T, Takada Y, Kappy MD, Beyer LA, Swiderski DL, Godin AL, Brewer S, King WM, Raphael Y. Mice with conditional deletion of Cx26 exhibit no vestibular phenotype despite secondary loss of Cx30 in the vestibular end organs. Hear Res 2015; 328:102-12. [PMID: 26232528 DOI: 10.1016/j.heares.2015.07.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 07/22/2015] [Accepted: 07/23/2015] [Indexed: 01/19/2023]
Abstract
Connexins are components of gap junctions which facilitate transfer of small molecules between cells. One member of the connexin family, Connexin 26 (Cx26), is prevalent in gap junctions in sensory epithelia of the inner ear. Mutations of GJB2, the gene encoding Cx26, cause significant hearing loss in humans. The vestibular system, however, does not usually show significant functional deficits in humans with this mutation. Mouse models for loss of Cx26 function demonstrate hearing loss and cochlear pathology but the extent of vestibular dysfunction and organ pathology are less well characterized. To understand the vestibular effects of Cx26 mutations, we evaluated vestibular function and histology of the vestibular sensory epithelia in a conditional knockout (CKO) mouse with Cx26 loss of function. Transgenic C57BL/6 mice, in which cre-Sox10 drives excision of the Cx26 gene from non-sensory cells flanking the sensory epithelium of the inner ear (Gjb2-CKO), were compared to age-matched wild types. Animals were sacrificed at ages between 4 and 40 weeks and their cochlear and vestibular sensory organs harvested for histological examination. Cx26 immunoreactivity was prominent in the peripheral vestibular system and the cochlea of wild type mice, but absent in the Gjb2-CKO specimens. The hair cell population in the cochleae of the Gjb2-CKO mice was severely depleted but in the vestibular organs it was intact, despite absence of Cx26 expression. The vestibular organs appeared normal at the latest time point examined, 40 weeks. To determine whether compensation by another connexin explains survival of the normal vestibular sensory epithelium, we evaluated the presence of Cx30 in the Gjb2-CKO mouse. We found that Cx30 labeling was normal in the cochlea, but it was decreased or absent in the vestibular system. The vestibular phenotype of the mutants was not different from wild-types as determined by time on the rotarod, head stability tests and physiological responses to vestibular stimulation. Thus presence of Cx30 in the cochlea does not compensate for Cx26 loss, and the absence of both connexins from vestibular sensory epithelia is no more injurious than the absence of one of them. Further studies to uncover the physiological foundation for this difference between the cochlea and the vestibular organs may help in designing treatments for GJB2 mutations.
Collapse
Affiliation(s)
- Min Young Lee
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - Tomoko Takada
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - Yohei Takada
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - Michelle D Kappy
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - Lisa A Beyer
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - Donald L Swiderski
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - Ashley L Godin
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - Shannon Brewer
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - W Michael King
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Department of Otolaryngology - Head and Neck Surgery, University of Michigan, 1150 West. Medical Center Dr., Ann Arbor, MI 48109-5648, USA.
| |
Collapse
|
11
|
Zhang J, Scherer SS, Yum SW. Dominant Cx26 mutants associated with hearing loss have dominant-negative effects on wild type Cx26. Mol Cell Neurosci 2010; 47:71-8. [PMID: 21040787 DOI: 10.1016/j.mcn.2010.10.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 09/23/2010] [Accepted: 10/15/2010] [Indexed: 11/19/2022] Open
Abstract
Mutations in GJB2, the gene encoding the human gap junction protein connexin26 (Cx26), cause either non-syndromic hearing loss or syndromes affecting both hearing and skin. We have investigated whether dominant Cx26 mutants can interact physically with wild type Cx26. HeLa cells stably expressing wild type Cx26 were transiently transfected to co-express nine individual dominant Cx26 mutants; six associated with non-syndromic hearing loss (W44C, W44S, R143Q, D179N, R184Q, and C202F) and three associated with hearing loss and palmoplantar keratoderma (G59A, R75Q, and R75W). All mutants co-localized and co-immunoprecipitated with wild type Cx26, indicating that they interact physically, likely by forming admixed heteromeric/heterotypic channels. Furthermore, all nine mutants inhibited the transfer of calcein in cells stably expressing Cx26, demonstrating that they each have dominant effects on wild type Cx26. Taken together, these results show that dominant-negative effects of these Cx26 mutants likely contribute to the pathogenesis of hearing loss.
Collapse
Affiliation(s)
- Junxian Zhang
- Department of Pediatrics, Division of Neurology, The Children's Hospital of Philadelphia, USA
| | | | | |
Collapse
|
12
|
Shehzadi A, Masood K. In Silico Study of Human Gap Junction Beta-2 Protein by Homology Modeling. Genomics Inform 2010. [DOI: 10.5808/gi.2010.8.2.070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
13
|
Dominant connexin26 mutants associated with human hearing loss have trans-dominant effects on connexin30. Neurobiol Dis 2010; 38:226-36. [PMID: 20096356 DOI: 10.1016/j.nbd.2010.01.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 11/27/2009] [Accepted: 01/12/2010] [Indexed: 11/23/2022] Open
Abstract
Dominant mutations in GJB2, the gene encoding the human gap junction protein connexin26 (Cx26), cause hearing loss. We investigated whether dominant Cx26 mutants interact directly with Cx30. HeLa cells stably expressing nine dominant Cx26 mutants, six associated with non-syndromic hearing loss (W44C, W44S, R143Q, D179N, R184Q and C202F) and three associated with hearing loss and palmoplantar keratoderma (G59A, R75Q and R75W), individually or together with Cx30, were analyzed by immunocytochemistry, co-immunoprecipitation, and functional assays (scrape-loading and/or fluorescence recovery after photobleaching). When expressed alone, all mutants formed gap junction plaques, but with impaired intercellular dye transfer. When expressed with Cx30, all mutants co-localized and co-immunoprecipitated with Cx30, indicating they likely co-assembled into heteromers. Furthermore, 8/9 Cx26 mutants inhibited the transfer of neurobiotin or calcein, indicating that these Cx26 mutants have trans-dominant effects on Cx30, an effect that may contribute to the pathogenesis of hearing loss.
Collapse
|
14
|
Tan A, Henzl MT. Conformational stabilities of guinea pig OCP1 and OCP2. Biophys Chem 2009; 144:108-18. [DOI: 10.1016/j.bpc.2009.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 07/08/2009] [Accepted: 07/09/2009] [Indexed: 11/25/2022]
|
15
|
Martínez AD, Acuña R, Figueroa V, Maripillan J, Nicholson B. Gap-junction channels dysfunction in deafness and hearing loss. Antioxid Redox Signal 2009; 11:309-22. [PMID: 18837651 PMCID: PMC2673109 DOI: 10.1089/ars.2008.2138] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Gap-junction channels connect the cytoplasm of adjacent cells, allowing the diffusion of ions and small metabolites. They are formed at the appositional plasma membranes by a family of related proteins named connexins. Mutations in connexins 26, 31, 30, 32, and 43 have been associated with nonsyndromic or syndromic deafness. The majority of these mutations are inherited in an autosomal recessive manner, but a few of them have been associated with dominantly inherited hearing loss. Mutations in the connexin26 gene (GJB2) are the most common cause of genetic deafness. This review summarizes the most relevant and recent information about different mutations in connexin genes found in human patients, with emphasis on GJB2. The possible effects of the mutations on channel expression and function are discussed, in addition to their possible physiologic consequences for inner ear physiology. Finally, we propose that connexin channels (gap junctions and hemichannels) may be targets for age-related hearing loss induced by oxidative damage.
Collapse
Affiliation(s)
- Agustín D Martínez
- Centro de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.
| | | | | | | | | |
Collapse
|
16
|
Yum SW, Zhang J, Valiunas V, Kanaporis G, Brink PR, White TW, Scherer SS. Human connexin26 and connexin30 form functional heteromeric and heterotypic channels. Am J Physiol Cell Physiol 2007; 293:C1032-48. [PMID: 17615163 DOI: 10.1152/ajpcell.00011.2007] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutations in GJB2 and GJB6, the genes that encode the human gap junction proteins connexin26 (Cx26) and connexin30 (Cx30), respectively, cause hearing loss. Cx26 and Cx30 are both expressed in the cochlea, leading to the potential formation of heteromeric hemichannels and heterotypic gap junction channels. To investigate their interactions, we expressed human Cx26 and Cx30 individually or together in HeLa cells. When they were expressed together, Cx26 and Cx30 appeared to interact directly (by their colocalization in gap junction plaques, by coimmunoprecipitation, and by fluorescence resonance energy transfer). Scrape-loading cells that express either Cx26 or Cx30 demonstrated that Cx26 homotypic channels robustly transferred both cationic and anionic tracers, whereas Cx30 homotypic channels transferred cationic but not anionic tracers. Cells expressing both Cx26 and Cx30 also transferred both cationic and anionic tracers by scrape loading, and the rate of calcein (an anionic tracer) transfer was intermediate between their homotypic counterparts by fluorescence recovery after photobleaching. Fluorescence recovery after photobleaching also showed that Cx26 and Cx30 form functional heterotypic channels, allowing the transfer of calcein, which did not pass the homotypic Cx30 channels. Electrophysiological recordings of cell pairs expressing different combinations of Cx26 and/or Cx30 demonstrated unique gating properties of cell pairs expressing both Cx26 and Cx30. These results indicate that Cx26 and Cx30 form functional heteromeric and heterotypic channels, whose biophysical properties and permeabilities are different from their homotypic counterparts.
Collapse
Affiliation(s)
- Sabrina W Yum
- Section of Neurology, St. Christopher's Hospital for Children, Erie Ave. at Front St., Philadelphia, PA 19134, USA.
| | | | | | | | | | | | | |
Collapse
|
17
|
Deng Y, Chen Y, Reuss L, Altenberg GA. Mutations of connexin 26 at position 75 and dominant deafness: essential role of arginine for the generation of functional gap-junctional channels. Hear Res 2006; 220:87-94. [PMID: 16945493 DOI: 10.1016/j.heares.2006.07.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 07/11/2006] [Accepted: 07/13/2006] [Indexed: 11/27/2022]
Abstract
Gap-junctional channels are large intercellular aqueous pores formed by head-to-head association of two gap-junctional hemichannels (connexin hexamers), one from each of the adjacent cells. The mechano-transduction of sound waves into electrical impulses occurs in the cochlea, which houses the organ of Corti. Hereditary deafness is frequent and mutations of connexin 26, the predominant connexin of the cochlea, are its most frequent cause. Mutations of R75 cause deafness and disrupt gap-junctional communication. Here, we determined the effects of substitutions of R75 with different residues (alanine, asparagine, aspartic acid, lysine, phenylalanine, tyrosine or tryptophan) on formation of gap-junctional channels and hemichannels. We show that connexin 26 R75 is essential for the formation of gap-junctional channels. Substitution of R75 with aromatic residues yields functional hemichannels that display altered voltage dependence, whereas substitution with other residues yields non-functional hemichannels. The expression of R75 mutants has a dominant negative effect on gap-junctional communication mediated by wild-type connexin 26, independently of the ability of the mutants to form functional gap-junctional hemichannels. Our results show that the arginine located at position 75 of connexin 26 is essential for function, and cannot be replaced by other residues.
Collapse
Affiliation(s)
- Yanqin Deng
- Department of Neuroscience and Cell Biology, and the Sealy Center for Structural Biology and Molecular Biophysics, The University of Texas Medical Branch, Galveston, TX 77555-0437, United States
| | | | | | | |
Collapse
|
18
|
Nickel R, Becker D, Forge A. Molecular and functional characterization of gap junctions in the avian inner ear. J Neurosci 2006; 26:6190-9. [PMID: 16763027 PMCID: PMC6675194 DOI: 10.1523/jneurosci.1116-06.2006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 04/12/2006] [Accepted: 04/27/2006] [Indexed: 11/21/2022] Open
Abstract
To analyze the fundamental role of gap junctions in the vertebrate inner ear, we examined molecular and functional characteristics of gap junctional communication (GJC) in the auditory and vestibular system of the chicken. By screening inner ear tissues for connexin isoforms using degenerate reverse transcription-PCR, we identified, in addition to chicken Cx43 (cCx43) and the inner-ear-specific cCx30, an as yet uncharacterized connexin predicted to be the ortholog of the mammalian Cx26. In situ hybridization indicated that cCx30 and cCx26 transcripts were both widely expressed in the cochlear duct and utricle in an overlapping pattern, suggesting coexpression of these isoforms similar to that in the mammalian inner ear. Immunohistochemistry demonstrated that cCx43 was present in gap junctions connecting supporting cells of the basilar papilla, in which its immunofluorescence colocalized with that of cCx30. However, cCx43 was absent from supporting cell gap junctions of the utricular macula. This variation in the molecular composition of gap junction plaques coincided with differences in the functional properties of GJC between the auditory and vestibular sensory epithelia. Fluorescence recovery after photobleaching, adapted to examine the diffusion of calcein in inner ear explants, revealed asymmetric communication pathways among supporting cells in the basilar papilla but not in the utricular macula. This study supports the hypothesis that the coexpression of Cx26/Cx30 is unique to gap junctions in the vertebrate inner ear. Furthermore, it demonstrates asymmetric GJC within the supporting cell population of the auditory sensory epithelium, which might mediate potassium cycling and/or intercellular signaling.
Collapse
Affiliation(s)
- Regina Nickel
- Centre for Auditory Research, The Ear Institute, University College London, London WC1X 8EE, United Kingdom.
| | | | | |
Collapse
|
19
|
Jagger DJ, Forge A. Compartmentalized and signal-selective gap junctional coupling in the hearing cochlea. J Neurosci 2006; 26:1260-8. [PMID: 16436613 PMCID: PMC6674557 DOI: 10.1523/jneurosci.4278-05.2006] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Gap junctional intercellular communication (GJIC) plays a major role in cochlear function. Recent evidence suggests that connexin 26 (Cx26) and Cx30 are the major constituent proteins of cochlear gap junction channels, possibly in a unique heteromeric configuration. We investigated the functional and structural properties of native cochlear gap junctions in rats, from birth to the onset of hearing [postnatal day 12 (P12)]. Confocal immunofluorescence revealed increasing Cx26 and Cx30 expression from P0 to P12. Functional GJIC was assessed by coinjection of Lucifer yellow (LY) and Neurobiotin (NBN) during whole-cell recordings in cochlear slices. At P0, there was restricted dye transfer between supporting cells around outer hair cells. Transfer was more extensive between supporting cells around inner hair cells. At P8, there was extensive transfer of both dyes between all supporting cell types. By P12, LY no longer transferred between the supporting cells immediately adjacent to hair cells but still transferred between more peripheral cells. NBN transferred freely, but it did not transfer between inner and outer pillar cells. Freeze fracture further demonstrated decreasing GJIC between inner and outer pillar cells around the onset of hearing. These data are supportive of the appearance of signal-selective gap junctions around the onset of hearing, with specific properties required to support auditory function. Furthermore, they suggest that separate medial and lateral buffering compartments exist in the hearing cochlea, which are individually dedicated to the homeostasis of inner hair cells and outer hair cells.
Collapse
MESH Headings
- Animals
- Cell Communication/physiology
- Coloring Agents/analysis
- Connexin 26
- Connexin 30
- Connexins/biosynthesis
- Connexins/genetics
- Connexins/physiology
- Fluorescein-5-isothiocyanate/analysis
- Freeze Fracturing
- Gap Junctions/physiology
- Gene Expression
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/physiology
- Hair Cells, Auditory, Inner/ultrastructure
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/physiology
- Hair Cells, Auditory, Outer/ultrastructure
- Hearing/physiology
- Microinjections
- Microscopy, Confocal
- Organ of Corti/growth & development
- Organ of Corti/physiology
- Organ of Corti/ultrastructure
- Patch-Clamp Techniques
- Rats
- Rats, Sprague-Dawley
- Rhodamines/analysis
Collapse
Affiliation(s)
- Daniel J Jagger
- Centre for Auditory Research, UCL Ear Institute, University College London, London WC1X 8EE, United Kingdom.
| | | |
Collapse
|
20
|
Chen Y, Deng Y, Bao X, Reuss L, Altenberg GA. Mechanism of the defect in gap-junctional communication by expression of a connexin 26 mutant associated with dominant deafness. FASEB J 2005; 19:1516-8. [PMID: 16009703 DOI: 10.1096/fj.04-3491fje] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Gap-junctional channels (connexin oligomers) are large-diameter aqueous pores formed by head-to-head association of two gap-junctional hemichannels, one from each of the adjacent cells. Profound hearing loss of genetic origin is common, and mutations of connexin 26 (Cx26) are the most frequent cause of this disorder. The Cx26 R75W mutant has been associated with disruption of cell-to-cell communication and profound hearing loss, but the mechanism of the gap-junctional defect is unknown. Here, we show that Cx26 R75W forms gap-junctional hemichannels that display altered voltage dependency and reduced permeability, and which cannot form functional gap-junctional channels between neighboring cells. The R75W phenotype is dominant at the gap-junction channel but not at the hemichannel level. Therefore, the absence of gap-junctional communication caused by R75W expression is due to defective gap-junction formation by functional hemichannels.
Collapse
Affiliation(s)
- Y Chen
- Department of Neuroscience and Cell Biology, and Membrane Protein Laboratory of the Sealy Center for Structural Biology, The University of Texas Medical Branch Galveston, Texas 77555-0437, USA
| | | | | | | | | |
Collapse
|
21
|
Seeman P, Bendová O, Rasková D, Malíková M, Groh D, Kabelka Z. Double heterozygosity with mutations involving both the GJB2 and GJB6 genes is a possible, but very rare, cause of congenital deafness in the Czech population. Ann Hum Genet 2005; 69:9-14. [PMID: 15638823 DOI: 10.1046/j.1529-8817.2003.00120.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutations in the GJB2 gene are the most common cause of prelingual, autosomal recessive, sensorineural hearing loss worldwide. Nevertheless, 10% to 50% of patients with prelingual nonsyndromic deafness only carry one mutation in the GJB2 gene. Recently a large 342 kb deletion named Delta(GJB6-D13S1830) involving the GJB6 gene was reported in Spanish and French deafness patients, either in a homozygous state or in combination with a monoallelic GJB2 mutation. No data have been reported about the frequency of this mutation in central Europe. Thirteen Czech patients with prelingual nonsyndromic sensorineural deafness carrying only one pathogenic mutation in the GJB2 gene were tested for the presence of the Delta(GJB6-D13S1830) mutation. One patient with a GJB2 mutation (313del14) also carried the Delta(GJB6-D13S1830). This is the first reported Czech case, and probably also the first central European case, of prelingual deafness due to mutations involving both the GJB2 and GJB6 genes. In addition, the Delta(GJB6-D13S1830) was not detected in 600 control chromosomes from Czech individuals with normal hearing. We show that in the Czech Republic the Delta(GJB6-D13S1830) is not the second most common causal factor in deafness patients heterozygous for a single GJB2 mutation, and that Delta(GJB6-D13S1830) is very rare in central Europe compared to reports from Spain, France and Israel.
Collapse
Affiliation(s)
- P Seeman
- Department of Child Neurology DNA laboratory, Charles University Prague, 2nd School of Medicine, V úvalu 84, 150 06 Praha 5, Czech.
| | | | | | | | | | | |
Collapse
|
22
|
Henzl MT, Thalmann I, Larson JD, Ignatova EG, Thalmann R. The cochlear F-box protein OCP1 associates with OCP2 and connexin 26. Hear Res 2005; 191:101-9. [PMID: 15109709 DOI: 10.1016/j.heares.2004.01.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2003] [Accepted: 01/01/2004] [Indexed: 11/18/2022]
Abstract
OCP1 and OCP2 are the most abundant proteins in the organ of Corti. Their distributions map identically to the epithelial gap-junction system, which unites the supporting cell population. Sequence data imply that OCP1 and OCP2 are subunits of an SCF E3 ubiquitin ligase. Consistent with that hypothesis, electrophoretic mobility-shift assays and pull-down assays with immobilized OCP1 demonstrate the formation of an OCP1-OCP2 complex. Sedimentation equilibrium data indicate that the complex is heterodimeric. The coincidence of the OCP1-OCP2 distribution and the epithelial gap-junction system suggests that one or more connexin isoforms may be targets of an SCF(OCP1) complex. Significantly, immobilized OCP1 binds (35)S-labeled connexin 26 (Cx26) produced by in vitro transcription-translation. Moreover, Cx26 can be co-immunoprecipitated from extracts of the organ of Corti by immobilized anti-OCP1, implying that OCP1 and Cx26 may associate in vivo. Given that lesions in the Cx26 gene (GJB2) are the most common cause of hereditary deafness, the OCP1-Cx26 interaction has substantial biomedical relevance.
Collapse
Affiliation(s)
- Michael T Henzl
- Department of Biochemistry, University of Missouri - Columbia, 117 Schweitzer Hall, Columbia, MO 65211, USA.
| | | | | | | | | |
Collapse
|
23
|
Abstract
Over the past decade, the molecular basis of most disorders of cornification has been unveiled. Among these, a distinct group has emerged because of primary defects in cell-cell communication due to faulty gap junction proteins also known as connexins. This review aims to delineate the cutaneous connexin disorders and to highlight intriguing genotype-phenotype correlations and emanating clinical implications.
Collapse
Affiliation(s)
- Gabriele Richard
- Department of Dermatology and Cutaneous Biology and the Jefferson Institute of Molecular Medicine, Jefferson Medical College, Philadelphia, PA 19107, USA.
| |
Collapse
|
24
|
Meşe G, Londin E, Mui R, Brink PR, White TW. Altered gating properties of functional Cx26 mutants associated with recessive non-syndromic hearing loss. Hum Genet 2004; 115:191-9. [PMID: 15241677 DOI: 10.1007/s00439-004-1142-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 04/21/2004] [Indexed: 11/29/2022]
Abstract
Connexins (Cx) form gap junctions that allow the exchange of small metabolites and ions. In the inner ear, Cx26 is the major gap junction protein and mutations in the Cx26-encoding gene, GJB2, are the most frequent cause of autosomal recessive non-syndromic hearing loss (DFNB1). We have functionally analyzed five Cx26 mutations associated with DFNB1, comprising the following single amino-acid substitutions: T8M, R143W, V153I, N206S and L214P. Coupling of cells expressing wild-type or mutant Cx26 was measured in the paired Xenopus oocyte assay. We found that the R143W, V153I and L214P mutations were unable to form functional channels. In contrast, the T8M and N206S mutants did electrically couple cells, though their voltage gating properties were different from wild-type Cx26 channels. The electrical coupling of oocytes expressing the T8M and N206S mutants suggest that these channels may retain high permeability to potassium ions. Therefore, deafness associated with Cx26 mutations may not only depend on reduced potassium re-circulation in the inner ear. Instead, abnormalities in the exchange of other metabolites through the cochlear gap junction network may also produce deafness.
Collapse
Affiliation(s)
- Gülistan Meşe
- Graduate Program in Genetics, State University of New York, BST 5-147, NY 11794-8661, Stony Brook, USA
| | | | | | | | | |
Collapse
|
25
|
Forge A, Becker D, Casalotti S, Edwards J, Marziano N, Nevill G. Gap junctions in the inner ear: comparison of distribution patterns in different vertebrates and assessement of connexin composition in mammals. J Comp Neurol 2003; 467:207-31. [PMID: 14595769 DOI: 10.1002/cne.10916] [Citation(s) in RCA: 214] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The distribution and size of gap junctions (GJ) in the sensory epithelia of the inner ear have been examined in a reptile (gecko), birds (chicken and owl), and mammals (mouse, guinea pig, gerbil, and bat), and the connexin composition of GJs in the mammalian inner ear has been assessed. Freeze fracture revealed a common pattern of GJ distribution in auditory and vestibular sensory epithelia in the different vertebrate classes. In all these tissues, GJs are numerous, often occupying more than 25% of the plasma membrane area of supporting cells and sometimes composed of more than 100,000 channels. Screening for 12 members of the connexin family in the mammalian inner ear by RT-PCR, Western blotting, and immunohistochemistry revealed four connexin isotypes, cx26, cx30, cx31, and cx43, in the cochlea and three, cx26, cx30, and cx43, in the vestibular organs. With antibodies characterised for their specificity, cx26 and cx30 colocalised in supporting cells of the organ of Corti, in the basal cell region of the stria vascularis, and in type 1 fibrocytes of the spiral ligament. No other connexin was detected in these regions. Cx31 was localised among type 2 fibrocytes below the spiral prominence, a region where cx30 was not expressed and cx26 expression appeared to be low. Cx43 was detected only in the region of "tension fibrocytes" lining the inner aspect of the otic capsule. This suggests separate functional compartments in the cochlea. In addition to cx26 and cx30, cx43 was detected in supporting cells of the vestibular sensory epithelia. Where cx26 and cx30 were colocalised, double immunogold labelling of thin sections showed both cx26 and cx30 evenly distributed in individual GJ plaques, a pattern consistent with the presence of heteromeric connexons. Coimmunoprecipitation of cochlear membrane proteins solubilised with a procedure that preserves the oligomeric structure of connexons confirmed the presence of heteromeric cx26/cx30 connexons. Heteromeric cx26/cx30 connexons may be unique to the inner ear, which could be one factor underlying the non-syndromic character of the deafness caused by mutations in cx26.
Collapse
Affiliation(s)
- Andrew Forge
- UCL Centre for Auditory Research and Institute of Laryngology and Otology, University College London, London WC1X 8EE, United Kingdom.
| | | | | | | | | | | |
Collapse
|
26
|
Ahmad S, Chen S, Sun J, Lin X. Connexins 26 and 30 are co-assembled to form gap junctions in the cochlea of mice. Biochem Biophys Res Commun 2003; 307:362-8. [PMID: 12859965 DOI: 10.1016/s0006-291x(03)01166-5] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The importance of connexins (Cxs) in the cochlear functions has been indicated by the finding that mutations in connexin genes cause a large proportion of sensorineural deafness cases. However, functional roles of connexins in the cochlea are still unclear. In this study, we compared the relative expression levels of 16 different subtypes of mouse connexins in the cochlea. cDNA macroarray hybridizations identified four most prominently expressed connexins (listed in descending order): Cxs 26, 29, 30, and 43. Two of these connexins (Cx26 and Cx30), both belonging to the beta-group, were investigated for their molecular assemblies in the cochlea. Co-immunostaining showed expressions of Cxs 26 and 30 in the same gap junction plaques and their co-assembly was confirmed by co-immunoprecipitation of proteins extracted from the cochlear tissues. The heterologous molecular assembly of connexins is expected to produce gap junctions with biophysical characteristics appropriate for maintaining ionic homeostasis in the cochlea.
Collapse
Affiliation(s)
- Shoab Ahmad
- Section on Neurobiology, Leslie and Susan Gonda Department of Cell and Molecular Biology, House Ear Institute, Los Angeles, CA 90057-1922, USA
| | | | | | | |
Collapse
|
27
|
Affiliation(s)
- G Richard
- Department of Dermatology and Cutaneous Biology, Jefferson Medical College and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA.
| |
Collapse
|
28
|
Abstract
The inner ear is structurally complex. A molecular description of its architecture is now emerging from the use of contemporary methods of cell and molecular biology, and from studies of ontogenetic development. With the application of clinical and molecular genetics, it has now become possible to identify genes associated with inherited, non-syndromic deafness and balance dysfunction in humans and in mice. This work is providing new insights into how the tissues of the inner ear are built to perform their tasks, and into the pathogenesis of a range of inner ear disorders.
Collapse
Affiliation(s)
- Andrew Forge
- UCL Centre for Auditory Research and Institute of Laryngology & Otology, University College London, UK
| | | |
Collapse
|