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Yasarbas SS, Inal E, Yildirim MA, Dubrac S, Lamartine J, Mese G. Connexins in epidermal health and diseases: insights into their mutations, implications, and therapeutic solutions. Front Physiol 2024; 15:1346971. [PMID: 38827992 PMCID: PMC11140265 DOI: 10.3389/fphys.2024.1346971] [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: 11/30/2023] [Accepted: 04/15/2024] [Indexed: 06/05/2024] Open
Abstract
The epidermis, the outermost layer of the skin, serves as a protective barrier against external factors. Epidermal differentiation, a tightly regulated process essential for epidermal homeostasis, epidermal barrier formation and skin integrity maintenance, is orchestrated by several players, including signaling molecules, calcium gradient and junctional complexes such as gap junctions (GJs). GJ proteins, known as connexins facilitate cell-to-cell communication between adjacent keratinocytes. Connexins can function as either hemichannels or GJs, depending on their interaction with other connexons from neighboring keratinocytes. These channels enable the transport of metabolites, cAMP, microRNAs, and ions, including Ca2+, across cell membranes. At least ten distinct connexins are expressed within the epidermis and mutations in at least five of them has been linked to various skin disorders. Connexin mutations may cause aberrant channel activity by altering their synthesis, their gating properties, their intracellular trafficking, and the assembly of hemichannels and GJ channels. In addition to mutations, connexin expression is dysregulated in other skin conditions including psoriasis, chronic wound and skin cancers, indicating the crucial role of connexins in skin homeostasis. Current treatment options for conditions with mutant or altered connexins are limited and primarily focus on symptom management. Several therapeutics, including non-peptide chemicals, antibodies, mimetic peptides and allele-specific small interfering RNAs are promising in treating connexin-related skin disorders. Since connexins play crucial roles in maintaining epidermal homeostasis as shown with linkage to a range of skin disorders and cancer, further investigations are warranted to decipher the molecular and cellular alterations within cells due to mutations or altered expression, leading to abnormal proliferation and differentiation. This would also help characterize the roles of each isoform in skin homeostasis, in addition to the development of innovative therapeutic interventions. This review highlights the critical functions of connexins in the epidermis and the association between connexins and skin disorders, and discusses potential therapeutic options.
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Affiliation(s)
- S. Suheda Yasarbas
- Izmir Institute of Technology, Faculty of Science, Department of Molecular Biology and Genetics, Izmir, Turkiye
| | - Ece Inal
- Izmir Institute of Technology, Faculty of Science, Department of Molecular Biology and Genetics, Izmir, Turkiye
| | - M. Azra Yildirim
- Izmir Institute of Technology, Faculty of Science, Department of Molecular Biology and Genetics, Izmir, Turkiye
| | - Sandrine Dubrac
- Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Innsbruck, Austria
| | - Jérôme Lamartine
- Skin Functional Integrity Group, Laboratory for Tissue Biology and Therapeutics Engineering (LBTI) CNRS UMR5305, University of Lyon, Lyon, France
| | - Gulistan Mese
- Izmir Institute of Technology, Faculty of Science, Department of Molecular Biology and Genetics, Izmir, Turkiye
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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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Connexin Mutations and Hereditary Diseases. Int J Mol Sci 2022; 23:ijms23084255. [PMID: 35457072 PMCID: PMC9027513 DOI: 10.3390/ijms23084255] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 04/04/2022] [Accepted: 04/09/2022] [Indexed: 02/01/2023] Open
Abstract
Inherited diseases caused by connexin mutations are found in multiple organs and include hereditary deafness, congenital cataract, congenital heart diseases, hereditary skin diseases, and X-linked Charcot–Marie–Tooth disease (CMT1X). A large number of knockout and knock-in animal models have been used to study the pathology and pathogenesis of diseases of different organs. Because the structures of different connexins are highly homologous and the functions of gap junctions formed by these connexins are similar, connexin-related hereditary diseases may share the same pathogenic mechanism. Here, we analyze the similarities and differences of the pathology and pathogenesis in animal models and find that connexin mutations in gap junction genes expressed in the ear, eye, heart, skin, and peripheral nerves can affect cellular proliferation and differentiation of corresponding organs. Additionally, some dominant mutations (e.g., Cx43 p.Gly60Ser, Cx32 p.Arg75Trp, Cx32 p.Asn175Asp, and Cx32 p.Arg142Trp) are identified as gain-of-function variants in vivo, which may play a vital role in the onset of dominant inherited diseases. Specifically, patients with these dominant mutations receive no benefits from gene therapy. Finally, the complete loss of gap junctional function or altered channel function including permeability (ions, adenosine triphosphate (ATP), Inositol 1,4,5-trisphosphate (IP3), Ca2+, glucose, miRNA) and electric activity are also identified in vivo or in vitro.
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Sellitto C, Li L, White TW. Connexin hemichannel inhibition ameliorates epidermal pathology in a mouse model of keratitis ichthyosis deafness syndrome. Sci Rep 2021; 11:24118. [PMID: 34916582 PMCID: PMC8677806 DOI: 10.1038/s41598-021-03627-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 12/07/2021] [Indexed: 02/05/2023] Open
Abstract
AbstractMutations in five different genes encoding connexin channels cause eleven clinically defined human skin diseases. Keratitis ichthyosis deafness (KID) syndrome is caused by point mutations in the GJB2 gene encoding Connexin 26 (Cx26) which result in aberrant activation of connexin hemichannels. KID syndrome has no cure and is associated with bilateral hearing loss, blinding keratitis, palmoplantar keratoderma, ichthyosiform erythroderma and a high incidence of childhood mortality. Here, we have tested whether a topically applied hemichhanel inhibitor (flufenamic acid, FFA) could ameliorate the skin pathology associated with KID syndrome in a transgenic mouse model expressing the lethal Cx26-G45E mutation. We found that FFA blocked the hemichannel activity of Cx26-G45E in vitro, and substantially reduced epidermal pathology in vivo, compared to untreated, or vehicle treated control animals. FFA did not reduce the expression of mutant connexin hemichannel protein, and cessation of FFA treatment allowed disease progression to continue. These results suggested that aberrant hemichannel activity is a major driver of skin disease in KID syndrome, and that the inhibition of mutant hemichannel activity could provide an attractive target to develop novel therapeutic interventions to treat this incurable disease.
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Natha CM, Vemulapalli V, Fiori MC, Chang CWT, Altenberg GA. Connexin hemichannel inhibitors with a focus on aminoglycosides. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166115. [PMID: 33711451 DOI: 10.1016/j.bbadis.2021.166115] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 02/06/2021] [Accepted: 02/22/2021] [Indexed: 12/31/2022]
Abstract
Connexins are membrane proteins involved directly in cell-to-cell communication through the formation of gap-junctional channels. These channels result from the head-to-head docking of two hemichannels, one from each of two adjacent cells. Undocked hemichannels are also present at the plasma membrane where they mediate the efflux of molecules that participate in autocrine and paracrine signaling, but abnormal increase in hemichannel activity can lead to cell damage in disorders such as cardiac infarct, stroke, deafness, cataracts, and skin diseases. For this reason, connexin hemichannels have emerged as a valid therapeutic target. Know small molecule hemichannel inhibitors are not ideal leads for the development of better drugs for clinical use because they are not specific and/or have toxic effects. Newer inhibitors are more selective and include connexin mimetic peptides, anti-connexin antibodies and drugs that reduce connexin expression such as antisense oligonucleotides. Re-purposed drugs and their derivatives are also promising because of the significant experience with their clinical use. Among these, aminoglycoside antibiotics have been identified as inhibitors of connexin hemichannels that do not inhibit gap-junctional channels. In this review, we discuss connexin hemichannels and their inhibitors, with a focus on aminoglycoside antibiotics and derivatives of kanamycin A that inhibit connexin hemichannels, but do not have antibiotic effect.
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Affiliation(s)
- Cristina M Natha
- Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Varun Vemulapalli
- Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Mariana C Fiori
- Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Cheng-Wei T Chang
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT, USA
| | - Guillermo A Altenberg
- Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
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Garcia-Vega L, O’Shaughnessy EM, Albuloushi A, Martin PE. Connexins and the Epithelial Tissue Barrier: A Focus on Connexin 26. BIOLOGY 2021; 10:biology10010059. [PMID: 33466954 PMCID: PMC7829877 DOI: 10.3390/biology10010059] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/11/2021] [Accepted: 01/12/2021] [Indexed: 12/15/2022]
Abstract
Simple Summary Tissues that face the external environment are known as ‘epithelial tissue’ and form barriers between different body compartments. This includes the outer layer of the skin, linings of the intestine and airways that project into the lumen connecting with the external environment, and the cornea of the eye. These tissues do not have a direct blood supply and are dependent on exchange of regulatory molecules between cells to ensure co-ordination of tissue events. Proteins known as connexins form channels linking cells directly and permit exchange of small regulatory signals. A range of environmental stimuli can dysregulate the level of connexin proteins and or protein function within the epithelia, leading to pathologies including non-healing wounds. Mutations in these proteins are linked with hearing loss, skin and eye disorders of differing severity. As such, connexins emerge as prime therapeutic targets with several agents currently in clinical trials. This review outlines the role of connexins in epithelial tissue and how their dysregulation contributes to pathological pathways. Abstract Epithelial tissue responds rapidly to environmental triggers and is constantly renewed. This tissue is also highly accessible for therapeutic targeting. This review highlights the role of connexin mediated communication in avascular epithelial tissue. These proteins form communication conduits with the extracellular space (hemichannels) and between neighboring cells (gap junctions). Regulated exchange of small metabolites less than 1kDa aide the co-ordination of cellular activities and in spatial communication compartments segregating tissue networks. Dysregulation of connexin expression and function has profound impact on physiological processes in epithelial tissue including wound healing. Connexin 26, one of the smallest connexins, is expressed in diverse epithelial tissue and mutations in this protein are associated with hearing loss, skin and eye conditions of differing severity. The functional consequences of dysregulated connexin activity is discussed and the development of connexin targeted therapeutic strategies highlighted.
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Harnessing the therapeutic potential of antibodies targeting connexin hemichannels. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166047. [PMID: 33418036 DOI: 10.1016/j.bbadis.2020.166047] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 11/17/2020] [Accepted: 12/03/2020] [Indexed: 12/20/2022]
Abstract
BACKGROUND Connexin hemichannels have been implicated in pathology-promoting conditions, including inflammation, numerous widespread human diseases, including cancer and diabetes, and several rare diseases linked to pathological point mutations. METHODS We analysed the literature focusing on antibodies capable of modulating hemichannel function, highlighting generation methods, applications to basic biomedical research and translational potential. RESULTS Anti-hemichannel antibodies generated over the past 3 decades targeted mostly connexin 43, with a focus on cancer treatment. A slow transition from relatively unselective polyclonal antibodies to more selective monoclonal antibodies resulted in few products with interesting characteristics that are under evaluation for clinical trials. Selection of antibodies from combinatorial phage-display libraries, has permitted to engineer a monoclonal antibody that binds to and blocks pathological hemichannels formed by connexin 26, 30 and 32. CONCLUSIONS All known antibodies that modulate connexin hemichannels target the two small extracellular loops of the connexin proteins. The extracellular region of different connexins is highly conserved, and few residues of each connexins are exposed. The search for new antibodies may develop an unprecedented potential for therapeutic applications, as it may benefit tremendously from novel whole-cell screening platforms that permit in situ selection of antibodies against membrane proteins in native state. The demonstrated efficacy of mAbs in reaching and modulating hemichannels in vivo, together with their relative specificity for connexins overlapping epitopes, should hopefully stimulate an interest for widening the scope of anti-hemichannel antibodies. There is no shortage of currently incurable diseases for which therapeutic intervention may benefit from anti-hemichannel antibodies capable of modulating hemichannel function selectively and specifically.
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Beach R, Abitbol JM, Allman BL, Esseltine JL, Shao Q, Laird DW. GJB2 Mutations Linked to Hearing Loss Exhibit Differential Trafficking and Functional Defects as Revealed in Cochlear-Relevant Cells. Front Cell Dev Biol 2020; 8:215. [PMID: 32300592 PMCID: PMC7142214 DOI: 10.3389/fcell.2020.00215] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/12/2020] [Indexed: 11/13/2022] Open
Abstract
GJB2 gene (that encodes Cx26) mutations are causal of hearing loss highlighting the importance of Cx26-based channel signaling amongst the supporting cells in the organ of Corti. While the majority of these GJB2 mutations are inherited in an autosomal recessive manner, others are inherited in an autosomal dominant manner and lead to syndromic hearing loss as well as skin diseases. To assess if common or divergent mechanisms are at the root of GJB2-linked hearing loss, we expressed several mutants in cochlear-relevant HEI-OC1 cells derived from the developing organ of Corti. Since supporting cells of the mature mammalian organ of Corti have negligible Cx43, but HEI-OC1 cells are rich in Cx43, we first used CRISPR-Cas9 to ablate endogenous Cx43, thus establishing a connexin-deficient platform for controlled reintroduction of hearing-relevant connexins and Cx26 mutants. We found three distinct outcomes and cellular phenotypes when hearing loss-linked Cx26 mutants were expressed in cochlear-relevant cells. The dominant syndromic Cx26 mutant N54K had trafficking defects and did not fully prevent wild-type Cx26 gap junction plaque formation but surprisingly formed gap junctions when co-expressed with Cx30. In contrast, the dominant syndromic S183F mutant formed gap junctions incapable of transferring dye and, as expected, co-localized in the same gap junctions as wild-type Cx26 and Cx30, but also gained the capacity to intermix with Cx43 within gap junctions. Both recessive non-syndromic Cx26 mutants (R32H and R184P) were retained in intracellular vesicles including early endosomes and did not co-localize with Cx30. As might be predicted, none of the Cx26 mutants prevented Cx43 gap junction plaque formation in Cx43-rich HEI-OC1 cells while Cx43-ablation had little effect on the expression of reference genes linked to auditory cell differentiation. We conclude from our studies in cochlear-relevant cells that the selected Cx26 mutants likely evoke hearing loss via three unique connexin defects that are independent of Cx43 status.
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Affiliation(s)
- Rianne Beach
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Julia M. Abitbol
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Brian L. Allman
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Jessica L. Esseltine
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Qing Shao
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Dale W. Laird
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
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Bommakanti K, Iyer JS, Stankovic KM. Cochlear histopathology in human genetic hearing loss: State of the science and future prospects. Hear Res 2019; 382:107785. [PMID: 31493568 PMCID: PMC6778517 DOI: 10.1016/j.heares.2019.107785] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 07/30/2019] [Accepted: 08/15/2019] [Indexed: 12/22/2022]
Abstract
Sensorineural hearing loss (SNHL) is an extraordinarily common disability, affecting 466 million people across the globe. Half of these incidents are attributed to genetic mutations that disrupt the structure and function of the cochlea. The human cochlea's interior cannot be imaged or biopsied without damaging hearing; thus, everything known about the morphologic correlates of hereditary human deafness comes from histopathologic studies conducted in either cadaveric human temporal bone specimens or animal models of genetic deafness. The purpose of the present review is to a) summarize the findings from all published histopathologic studies conducted in human temporal bones with known SNHL-causing genetic mutations, and b) compare the reported phenotypes of human vs. mouse SNHL caused by the same genetic mutation. The fact that human temporal bone histopathologic analysis has been reported for only 22 of the nearly 200 identified deafness-causing genes suggests a great need for alternative and improved techniques for studying human hereditary deafness; in light of this, the present review concludes with a summary of promising future directions, specifically in the fields of high resolution cochlear imaging, intracochlear fluid biopsy, and gene therapy.
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Affiliation(s)
- Krishna Bommakanti
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA; Eaton Peabody Laboratories and Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, USA; University of California San Diego School of Medicine, San Diego, CA, USA
| | - Janani S Iyer
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA; Eaton Peabody Laboratories and Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, USA; Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA, USA; Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, USA
| | - Konstantina M Stankovic
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA; Eaton Peabody Laboratories and Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, USA; Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA, USA; Harvard Program in Therapeutic Science, Harvard Medical School, Boston, MA, USA.
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Lin X, Li G, Zhang Y, Zhao J, Lu J, Gao Y, Liu H, Li GL, Yang T, Song L, Wu H. Hearing consequences in Gjb2 knock-in mice: implications for human p.V37I mutation. Aging (Albany NY) 2019; 11:7416-7441. [PMID: 31562289 PMCID: PMC6782001 DOI: 10.18632/aging.102246] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 08/22/2019] [Indexed: 01/09/2023]
Abstract
Human p.V37I mutation of GJB2 gene was strongly correlated with late-onset progressive hearing loss, especially among East Asia populations. We generated a knock-in mouse model based on human p.V37I variant (c.109G>A) that recapitulated the human phenotype. Cochlear pathology revealed no significant hair cell loss, stria vascularis atrophy or spiral ganglion neuron loss, but a significant change in the length of gap junction plaques, which may have contributed to the observed mild endocochlear potential (EP) drop in homozygous mice lasting lifetime. The cochlear amplification in homozygous mice was compromised, but outer hair cells' function remained unchanged, indicating that the reduced amplification was EP- rather than prestin-generated. In addition to ABR threshold elevation, ABR wave I latencies were also prolonged in aged homozygous animals. We found in homozygous IHCs a significant increase in ICa but no change in Ca2+ efficiency in triggering exocytosis. Environmental insults such as noise exposure, middle ear injection of KCl solution and systemic application of furosemide all exacerbated the pathological phenotype in homozygous mice. We conclude that this Gjb2 mutation-induced hearing loss results from 1) reduced cochlear amplifier caused by lowered EP, 2) IHCs excitotoxicity associated with potassium accumulation around hair cells, and 3) progression induced by environmental insults.
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Affiliation(s)
- Xin Lin
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Gen Li
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Yu Zhang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Jingjing Zhao
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Jiawen Lu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Yunge Gao
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Huihui Liu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Geng-Lin Li
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Tao Yang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Lei Song
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose diseases, Shanghai 200125, China
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11
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Lu X, Chen Z, Vick S, Watsky MA. Vitamin D receptor and metabolite effects on corneal epithelial cell gap junction proteins. Exp Eye Res 2019; 187:107776. [PMID: 31465769 DOI: 10.1016/j.exer.2019.107776] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/12/2019] [Accepted: 08/23/2019] [Indexed: 12/29/2022]
Abstract
Vitamin D is a fat-soluble prohormone that can be activated both systemically and within individual tissues. Our lab has previously demonstrated that the corneal epithelium can activate vitamin D and that the vitamin D metabolites 1,25(OH)2D3 and 24R,25(OH)2D3 can affect corneal epithelial migration, proliferation, and tight and gap junction function. These vitamin D-derived metabolites signal through the vitamin D receptor (VDR). The purpose of this study was to specifically determine the effects of 1,25(OH)2D3 and 24R,25(OH)2D3 on corneal epithelial cell gap junction proteins. Connexin (Cx) 26, 30 and 43 protein expression was detected in a human corneal epithelial cell line (HCEC), wild type and vitamin D receptor knockout (VDR-/-) mouse corneas, and cultured mouse primary epithelial cells (MPCEC). In vitro gap junction function was assessed using the scrape loading/dye transfer assay. HCEC and MPCEC were treated with 1,25(OH)2D3 or 24R,25(OH)2D3. Western blotting was used to detect gap junction proteins. Vitamin D3 effects on epithelial intracellular Ca++ (Ca++i) were determined using the dye Cal-520. Cx26 and Cx43 protein levels were significantly increased in HCEC and MPCEC treated with both 1,25(OH)2D3 and 24R,25(OH)2D3. Cx30 and Cx43 protein levels were also significantly increased in VDR-/- MPCEC. In vitro gap junction connectivity was significanlty enhanced in HCEC and MPCEC cultured with 24R,25(OH)2D3 and 1,25(OH)2D3. Ca++i was not affected by 1,25(OH)2D3 or 24R,25(OH)2D3 in HCEC or MPCEC. We conclude that both 1,25(OH)2D3 and 24R,25(OH)2D3 are positive regulators of connexin proteins and gap junction communication in the corneal epithelium. These vitamin D metabolites appear to signal through both VDR-dependent and -independent pathways. The effects of vitamin D on corneal epithelial gap junctions do not seem to be dependent on Ca++i.
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Affiliation(s)
- Xiaowen Lu
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Zhong Chen
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Sarah Vick
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Mitchell A Watsky
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA; The Graduate School, Augusta University, Augusta, GA, USA.
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12
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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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13
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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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14
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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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15
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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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16
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Shibata SB, Yoshimura H, Ranum PT, Goodwin AT, Smith RJH. Intravenous rAAV2/9 injection for murine cochlear gene delivery. Sci Rep 2017; 7:9609. [PMID: 28852025 PMCID: PMC5575199 DOI: 10.1038/s41598-017-09805-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 07/28/2017] [Indexed: 01/08/2023] Open
Abstract
Gene therapy for genetic deafness is a promising approach by which to prevent hearing loss or to restore hearing after loss has occurred. Although a variety of direct approaches to introduce viral particles into the inner ear have been described, presumed physiological barriers have heretofore precluded investigation of systemic gene delivery to the cochlea. In this study, we sought to characterize systemic delivery of a rAAV2/9 vector as a non-invasive means of cochlear transduction. In wild-type neonatal mice (postnatal day 0-1), we show that intravenous injection of rAAV2/9 carrying an eGFP-reporter gene results in binaural transduction of inner hair cells, spiral ganglion neurons and vestibular hair cells. Transduction efficiency increases in a dose-dependent manner. Inner hair cells are transduced in an apex-to-base gradient, with transduction reaching 96% in the apical turn. Hearing acuity in treated animals is unaltered at postnatal day 30. Transduction is influenced by viral serotype and age at injection, with less efficient cochlear transduction observed with systemic delivery of rAAV2/1 and in juvenile mice with rAAV2/9. Collectively, these data validate intravenous delivery of rAAV2/9 as a novel and atraumatic technique for inner ear transgene delivery in early postnatal mice.
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Affiliation(s)
- Seiji B Shibata
- Department of Otolaryngology - Head and Neck Surgery, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.,Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Hidekane Yoshimura
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.,Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Nagano, 390-8621, Japan
| | - Paul T Ranum
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.,Interdisciplinary Graduate Program in Molecular & Cellular Biology, The University of Iowa Graduate College, University of Iowa, Iowa City, IA, 52242, USA
| | - Alexander T Goodwin
- Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Richard J H Smith
- Department of Otolaryngology - Head and Neck Surgery, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA. .,Molecular Otolaryngology and Renal Research Laboratories, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA. .,Interdisciplinary Graduate Program in Molecular & Cellular Biology, The University of Iowa Graduate College, University of Iowa, Iowa City, IA, 52242, USA. .,Iowa Institute of Human Genetics, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.
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17
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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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18
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Press E, Alaga KC, Barr K, Shao Q, Bosen F, Willecke K, Laird DW. Disease-linked connexin26 S17F promotes volar skin abnormalities and mild wound healing defects in mice. Cell Death Dis 2017; 8:e2845. [PMID: 28569788 PMCID: PMC5520893 DOI: 10.1038/cddis.2017.234] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 03/20/2017] [Accepted: 03/21/2017] [Indexed: 12/11/2022]
Abstract
Several mutant mice have been generated to model connexin (Cx)-linked skin diseases; however, the role of connexins in skin maintenance and during wound healing remains to be fully elucidated. Here we generated a novel, viable, and fertile mouse (Cx26CK14-S17F/+) with the keratitis-ichthyosis-deafness mutant (Cx26S17F) driven by the cytokeratin 14 promoter. This mutant mouse mirrors several Cx26-linked human skin pathologies suggesting that the etiology of Cx26-linked skin disease indeed stems from epidermal expression of the Cx26 mutant. Cx26CK14-S17F/+ foot pad epidermis formed severe palmoplantar keratoderma, which expressed elevated levels of Cx26 and filaggrin. Primary keratinocytes isolated from Cx26CK14-S17F/+ neonates exhibited reduced gap junctional intercellular communication and migration. Furthermore, Cx26CK14-S17F/+ mouse skin wound closure was normal but repaired epidermis appeared hyperplastic with elevated expression of cytokeratin 6. Taken together, we suggest that the Cx26S17F mutant disturbs keratinocyte differentiation and epidermal remodeling following wound closure. We further posit that Cx26 contributes to epidermal homeostasis by regulating keratinocyte differentiation, and that mice harboring a disease-linked Cx26 mutant display epidermal abnormalities yet retain most wound healing properties.
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Affiliation(s)
- Eric Press
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
| | - Katanya C Alaga
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Kevin Barr
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Qing Shao
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Felicitas Bosen
- LIMES (Life and Medical Sciences Institute), Molecular Genetics, University of Bonn, Bonn, Germany
| | - Klaus Willecke
- LIMES (Life and Medical Sciences Institute), Molecular Genetics, University of Bonn, Bonn, Germany
| | - Dale W Laird
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada.,Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
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19
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Gudmundsson S, Wilbe M, Ekvall S, Ameur A, Cahill N, Alexandrov LB, Virtanen M, Hellström Pigg M, Vahlquist A, Törmä H, Bondeson ML. Revertant mosaicism repairs skin lesions in a patient with keratitis-ichthyosis-deafness syndrome by second-site mutations in connexin 26. Hum Mol Genet 2017; 26:1070-1077. [PMID: 28158657 PMCID: PMC5409067 DOI: 10.1093/hmg/ddx017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 12/30/2016] [Indexed: 01/21/2023] Open
Abstract
Revertant mosaicism (RM) is a naturally occurring phenomenon where the pathogenic effect of a germline mutation is corrected by a second somatic event. Development of healthy-looking skin due to RM has been observed in patients with various inherited skin disorders, but not in connexin-related disease. We aimed to clarify the underlying molecular mechanisms of suspected RM in the skin of a patient with keratitis-ichthyosis-deafness (KID) syndrome. The patient was diagnosed with KID syndrome due to characteristic skin lesions, hearing deficiency and keratitis. Investigation of GJB2 encoding connexin (Cx) 26 revealed heterozygosity for the recurrent de novo germline mutation, c.148G > A, p.Asp50Asn. At age 20, the patient developed spots of healthy-looking skin that grew in size and number within widespread erythrokeratodermic lesions. Ultra-deep sequencing of two healthy-looking skin biopsies identified five somatic nonsynonymous mutations, independently present in cis with the p.Asp50Asn mutation. Functional studies of Cx26 in HeLa cells revealed co-expression of Cx26-Asp50Asn and wild-type Cx26 in gap junction channel plaques. However, Cx26-Asp50Asn with the second-site mutations identified in the patient displayed no formation of gap junction channel plaques. We argue that the second-site mutations independently inhibit Cx26-Asp50Asn expression in gap junction channels, reverting the dominant negative effect of the p.Asp50Asn mutation. To our knowledge, this is the first time RM has been reported to result in the development of healthy-looking skin in a patient with KID syndrome.
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Affiliation(s)
- Sanna Gudmundsson
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Maria Wilbe
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Sara Ekvall
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Adam Ameur
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Nicola Cahill
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Ludmil B Alexandrov
- Theoretical Biology and Biophysics (T-6), Los Alamos National Laboratory, Los Alamos, NM, USA and
| | - Marie Virtanen
- Department of Medical Sciences, Dermatology, Uppsala University, Uppsala, Sweden
| | - Maritta Hellström Pigg
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Anders Vahlquist
- Department of Medical Sciences, Dermatology, Uppsala University, Uppsala, Sweden
| | - Hans Törmä
- Department of Medical Sciences, Dermatology, Uppsala University, Uppsala, Sweden
| | - Marie-Louise Bondeson
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
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20
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Srinivas M, Verselis VK, White TW. Human diseases associated with connexin mutations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:192-201. [PMID: 28457858 DOI: 10.1016/j.bbamem.2017.04.024] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 04/20/2017] [Accepted: 04/25/2017] [Indexed: 01/11/2023]
Abstract
Gap junctions and hemichannels comprised of connexins impact many cellular processes. Significant advances in our understanding of the functional role of these channels have been made by the identification of a host of genetic diseases caused by connexin mutations. Prominent features of connexin disorders are the inability of other connexins expressed in the same cell type to compensate for the mutated one, and the ability of connexin mutants to dominantly influence the activity of other wild-type connexins. Functional studies have begun to identify some of the underlying mechanisms whereby connexin channel mutation contributes to the disease state. Detailed mechanistic understanding of these functional differences will help to facilitate new pathophysiology driven therapies for the diverse array of connexin genetic disorders. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Miduturu Srinivas
- Department of Biological and Vision Sciences, SUNY College of Optometry, New York, NY 10036, USA
| | - Vytas K Verselis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA.
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21
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Nin F, Yoshida T, Sawamura S, Ogata G, Ota T, Higuchi T, Murakami S, Doi K, Kurachi Y, Hibino H. The unique electrical properties in an extracellular fluid of the mammalian cochlea; their functional roles, homeostatic processes, and pathological significance. Pflugers Arch 2016; 468:1637-49. [PMID: 27568193 PMCID: PMC5026722 DOI: 10.1007/s00424-016-1871-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 08/16/2016] [Indexed: 12/13/2022]
Abstract
The cochlea of the mammalian inner ear contains an endolymph that exhibits an endocochlear potential (EP) of +80 mV with a [K(+)] of 150 mM. This unusual extracellular solution is maintained by the cochlear lateral wall, a double-layered epithelial-like tissue. Acoustic stimuli allow endolymphatic K(+) to enter sensory hair cells and excite them. The positive EP accelerates this K(+) influx, thereby sensitizing hearing. K(+) exits from hair cells and circulates back to the lateral wall, which unidirectionally transports K(+) to the endolymph. In vivo electrophysiological assays demonstrated that the EP stems primarily from two K(+) diffusion potentials yielded by [K(+)] gradients between intracellular and extracellular compartments in the lateral wall. Such gradients seem to be controlled by ion channels and transporters expressed in particular membrane domains of the two layers. Analyses of human deafness genes and genetically modified mice suggested the contribution of these channels and transporters to EP and hearing. A computational model, which reconstitutes unidirectional K(+) transport by incorporating channels and transporters in the lateral wall and connects this transport to hair cell transcellular K(+) fluxes, simulates the circulation current flowing between the endolymph and the perilymph. In this model, modulation of the circulation current profile accounts for the processes leading to EP loss under pathological conditions. This article not only summarizes the unique physiological and molecular mechanisms underlying homeostasis of the EP and their pathological relevance but also describes the interplay between EP and circulation current.
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Affiliation(s)
- Fumiaki Nin
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
| | - Takamasa Yoshida
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
- Center for Transdisciplinary Research, Niigata University, Niigata, 950-2181, Japan
- Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan
| | - Seishiro Sawamura
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
| | - Genki Ogata
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
- Center for Transdisciplinary Research, Niigata University, Niigata, 950-2181, Japan
| | - Takeru Ota
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
| | - Taiga Higuchi
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
| | - Shingo Murakami
- Division of Molecular and Cellular Pharmacology, Department of Pharmacology, Osaka University, Osaka, 565-0871, Japan
- Center for Advanced Medical Engineering and Informatics, Graduate School of Medicine, Osaka University, Osaka, 565-0871, Japan
- Department of Physiology, School of Medicine, Toho University, Tokyo, 143-8540, Japan
| | - Katsumi Doi
- Department of Otolaryngology, Kindai University Faculty of Medicine, Osaka, 589-8511, Japan
| | - Yoshihisa Kurachi
- Division of Molecular and Cellular Pharmacology, Department of Pharmacology, Osaka University, Osaka, 565-0871, Japan
- Center for Advanced Medical Engineering and Informatics, Graduate School of Medicine, Osaka University, Osaka, 565-0871, Japan
| | - Hiroshi Hibino
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan.
- Center for Transdisciplinary Research, Niigata University, Niigata, 950-2181, Japan.
- AMED-CREST, AMED, Niigata, Japan.
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22
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Cx26 knockout predisposes the mammary gland to primary mammary tumors in a DMBA-induced mouse model of breast cancer. Oncotarget 2016; 6:37185-99. [PMID: 26439696 PMCID: PMC4741923 DOI: 10.18632/oncotarget.5953] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 09/17/2015] [Indexed: 11/28/2022] Open
Abstract
Down-regulation of the gap junction protein connexin26 (Cx26) is an early event following breast cancer onset and has led to Cx26 being classically described as a tumor suppressor. Interestingly, mutations in theCx26 gene (GJB2) reduce or ablate Cx26 gap junction channel function and are the most common cause of genetic deafness. It is unknown if patients with loss-of-function GJB2 mutations have a greater susceptibility to breast tumorigenesis or aggressive breast cancer progression. To investigate these possibilities, 7, 12-dimethylbenz[α]anthracene (DMBA)-induced tumor development was evaluated in BLG-Cre; Cx26fl/fl mice expressing Cre under the β-Lactoglobulin promoter (Cre+) compared to Cx26fl/fl controlmice (Cre-) following pituitary isograft driven Cx26 knockout. A significantly increased number of DMBA-treated Cre+ mice developed primary mammary tumors, as well as developed multiple tumors, compared to Cre- mice. Primary tumors of Cre+ mice were of multiple histological subtypes and had similar palpable tumour onset and growth rate compared to tumors from Cre- mice. Lungs were evaluated for evidence of metastases revealing a similar percentage of lung metastases in Cre+ and Cre- mice. Together, our results suggest that loss of Cx26 predisposes the mammary gland to chemically induced mammary tumour formation which may have important implications to patients with GJB2 mutations.
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23
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García IE, Prado P, Pupo A, Jara O, Rojas-Gómez D, Mujica P, Flores-Muñoz C, González-Casanova J, Soto-Riveros C, Pinto BI, Retamal MA, González C, Martínez AD. Connexinopathies: a structural and functional glimpse. BMC Cell Biol 2016; 17 Suppl 1:17. [PMID: 27228968 PMCID: PMC4896260 DOI: 10.1186/s12860-016-0092-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Mutations in human connexin (Cx) genes have been related to diseases, which we termed connexinopathies. Such hereditary disorders include nonsyndromic or syndromic deafness (Cx26, Cx30), Charcot Marie Tooth disease (Cx32), occulodentodigital dysplasia and cardiopathies (Cx43), and cataracts (Cx46, Cx50). Despite the clinical phenotypes of connexinopathies have been well documented, their pathogenic molecular determinants remain elusive. The purpose of this work is to identify common/uncommon patterns in channels function among Cx mutations linked to human diseases. To this end, we compiled and discussed the effect of mutations associated to Cx26, Cx32, Cx43, and Cx50 over gap junction channels and hemichannels, highlighting the function of the structural channel domains in which mutations are located and their possible role affecting oligomerization, gating and perm/selectivity processes.
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Affiliation(s)
- Isaac E García
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Pavel Prado
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Oscar Jara
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Diana Rojas-Gómez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Paula Mujica
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Flores-Muñoz
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Jorge González-Casanova
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Soto-Riveros
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Bernardo I Pinto
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
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24
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Connexin channels in congenital skin disorders. Semin Cell Dev Biol 2016; 50:4-12. [PMID: 26775130 DOI: 10.1016/j.semcdb.2015.11.018] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 11/23/2015] [Indexed: 11/22/2022]
Abstract
Gap junctions and hemichannels comprised of connexins influence epidermal proliferation and differentiation. Significant advances in our understanding of the functional role of connexins in the skin have been made by studying the diseases caused by connexin mutations. Eleven clinically defined cutaneous disorders with an overlapping spectrum of phenotypes are caused by mutations in five different connexin genes, highlighting that disease presentation must be deciphered with an understanding of how connexin functions are affected. Increasing evidence suggests that the skin diseases produced by connexin mutations result from dominant gains of function. In palmoplantar keratoderma with deafness, the connexin 26 mutations transdominantly alter the function of wild-type connexin 43 and create leaky heteromeric hemichannels. In keratitis-ichthyosis-deafness syndrome, different connexin 26 mutations can either form dominant hemichannels with altered calcium regulation or increased calcium permeability, leading to clinical subtypes of this syndrome. It is only with detailed understanding of these subtle functional differences that we can hope to create successful pathophysiology driven therapies for the connexin skin disorders.
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25
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García IE, Bosen F, Mujica P, Pupo A, Flores-Muñoz C, Jara O, González C, Willecke K, Martínez AD. From Hyperactive Connexin26 Hemichannels to Impairments in Epidermal Calcium Gradient and Permeability Barrier in the Keratitis-Ichthyosis-Deafness Syndrome. J Invest Dermatol 2016; 136:574-583. [PMID: 26777423 DOI: 10.1016/j.jid.2015.11.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 11/05/2015] [Accepted: 11/06/2015] [Indexed: 01/19/2023]
Abstract
The keratitis-ichthyosis-deafness (KID) syndrome is characterized by corneal, skin, and hearing abnormalities. KID has been linked to heterozygous dominant missense mutations in the GJB2 and GJB6 genes, encoding connexin26 and 30, respectively. In vitro evidence indicates that KID mutations lead to hyperactive (open) hemichannels, which in some cases is accompanied by abnormal function of gap junction channels. Transgenic mouse models expressing connexin26 KID mutations reproduce human phenotypes and present impaired epidermal calcium homeostasis and abnormal lipid composition of the stratum corneum affecting the water barrier. Here we have compiled relevant data regarding the KID syndrome and propose a mechanism for the epidermal aspects of the disease.
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Affiliation(s)
- Isaac E García
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Felicitas Bosen
- LIMES (Life and Medical Sciences) Institute, University of Bonn, Bonn, Germany
| | - Paula Mujica
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Flores-Muñoz
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Oscar Jara
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Klaus Willecke
- LIMES (Life and Medical Sciences) Institute, University of Bonn, Bonn, Germany.
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
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26
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Abstract
Connexin mutations underlie numerous human genetic diseases. Several connexin genes have been linked to skin diseases, and mechanistic studies have indicated that a gain of abnormal channel function may be responsible for pathology. The topical accessibility of the epidermal connexins, the existence of several mouse models of human skin disease, and the ongoing identification of pharmacological inhibitors targeting connexins provide an opportunity to test new therapeutic approaches.
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Affiliation(s)
- Noah A Levit
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, United States
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, United States.
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27
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Bosen F, Celli A, Crumrine D, vom Dorp K, Ebel P, Jastrow H, Dörmann P, Winterhager E, Mauro T, Willecke K. Altered epidermal lipid processing and calcium distribution in the KID syndrome mouse model Cx26S17F. FEBS Lett 2015; 589:1904-10. [PMID: 26070424 DOI: 10.1016/j.febslet.2015.05.047] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 05/15/2015] [Accepted: 05/18/2015] [Indexed: 12/23/2022]
Abstract
The keratitis-ichthyosis-deafness (KID) syndrome is caused by mutations in the gap junctional channel protein connexin 26 (Cx26), among them the mutation Cx26S17F. Heterozygous Cx26S17F mice resemble the human KID syndrome, i.e. exhibiting epidermal hyperplasia and hearing impairments. Newborn Cx26S17F mice show a defective epidermal water barrier as well as altered epidermal lipid secretion and location. Linoleoyl ω-esterified ceramides are strongly decreased on the skin surface of Cx26S17F mice. Moreover, the epidermal calcium gradient is altered in the mutant mice. These alterations may be caused by an abnormal Cx26S17F channel function that leads to a defective epidermal water barrier, which in turn may trigger the hyperproliferation seen in the KID syndrome.
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Affiliation(s)
- Felicitas Bosen
- LIMES (Life and Medical Science Institute), Molecular Genetics, University of Bonn, 53115 Bonn, Germany
| | - Anna Celli
- Department of Dermatology, SF-VAMC and UCSF, San Francisco, CA, USA
| | - Debra Crumrine
- Department of Dermatology, SF-VAMC and UCSF, San Francisco, CA, USA
| | - Katharina vom Dorp
- Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Germany
| | - Philipp Ebel
- LIMES (Life and Medical Science Institute), Molecular Genetics, University of Bonn, 53115 Bonn, Germany
| | - Holger Jastrow
- Electron Microscopy Unit, Imaging Center Essen, University Clinic Essen, Germany
| | - Peter Dörmann
- Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Germany
| | - Elke Winterhager
- Electron Microscopy Unit, Imaging Center Essen, University Clinic Essen, Germany
| | - Theodora Mauro
- Department of Dermatology, SF-VAMC and UCSF, San Francisco, CA, USA
| | - Klaus Willecke
- LIMES (Life and Medical Science Institute), Molecular Genetics, University of Bonn, 53115 Bonn, Germany.
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28
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Wingard JC, Zhao HB. Cellular and Deafness Mechanisms Underlying Connexin Mutation-Induced Hearing Loss - A Common Hereditary Deafness. Front Cell Neurosci 2015; 9:202. [PMID: 26074771 PMCID: PMC4448512 DOI: 10.3389/fncel.2015.00202] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Accepted: 05/11/2015] [Indexed: 11/30/2022] Open
Abstract
Hearing loss due to mutations in the connexin gene family, which encodes gap junctional proteins, is a common form of hereditary deafness. In particular, connexin 26 (Cx26, GJB2) mutations are responsible for ~50% of non-syndromic hearing loss, which is the highest incidence of genetic disease. In the clinic, Cx26 mutations cause various auditory phenotypes ranging from profound congenital deafness at birth to mild, progressive hearing loss in late childhood. Recent experiments demonstrate that congenital deafness mainly results from cochlear developmental disorders rather than hair cell degeneration and endocochlear potential reduction, while late-onset hearing loss results from reduction of active cochlear amplification, even though cochlear hair cells have no connexin expression. However, there is no apparent, demonstrable relationship between specific changes in connexin (channel) functions and the phenotypes of mutation-induced hearing loss. Moreover, new experiments further demonstrate that the hypothesized K+-recycling disruption is not a principal deafness mechanism for connexin deficiency induced hearing loss. Cx30 (GJB6), Cx29 (GJC3), Cx31 (GJB3), and Cx43 (GJA1) mutations can also cause hearing loss with distinct pathological changes in the cochlea. These new studies provide invaluable information about deafness mechanisms underlying connexin mutation-induced hearing loss and also provide important information for developing new protective and therapeutic strategies for this common deafness. However, the detailed cellular mechanisms underlying these pathological changes remain unclear. Also, little is known about specific mutation-induced pathological changes in vivo and little information is available for humans. Such further studies are urgently required.
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Affiliation(s)
- Jeffrey C Wingard
- Department of Otolaryngology, University of Kentucky Medical Center , Lexington, KY , USA
| | - Hong-Bo Zhao
- Department of Otolaryngology, University of Kentucky Medical Center , Lexington, KY , USA
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29
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Connexins and skin disease: insights into the role of beta connexins in skin homeostasis. Cell Tissue Res 2015; 360:645-58. [PMID: 25616557 DOI: 10.1007/s00441-014-2094-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 12/08/2014] [Indexed: 12/20/2022]
Abstract
Cell-to-cell communication triggered by connexin channels plays a central role in maintaining epidermal homeostasis. Here, we discuss the role of the beta connexin subgroup, where site-specific mutations in at least 4 of these proteins lead to distinctive non-inflammatory and inflammatory hyperproliferative epidermal disorders. Recent advances in the molecular pathways evoked and correlation with clinical outcome are discussed. The latest data provide increasing evidence that connexins in the epidermis are sensors to environmental stress and that targeting aberrant hemichannel activity holds significant therapeutic potential for inflammatory skin disorders.
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30
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Recordati C, Basta SM, Benedetti L, Baldin F, Capillo M, Scanziani E, Gobbi A. Pathologic and Environmental Studies Provide New Pathogenetic Insights Into Ringtail of Laboratory Mice. Vet Pathol 2014; 52:700-11. [DOI: 10.1177/0300985814556191] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ringtail is a pathologic condition of laboratory rodents characterized by annular constrictions of the tail. Traditionally, it is classified as an environmental disorder caused by low relative humidity, but other factors (temperature, dietary deficiencies, genetic susceptibility, and caging type) have also been proposed. Twenty litters of mice with ringtail lesions occurred from September 2010 to August 2013 in a facility located in the northern Italy. Mice were maintained under controlled environmental conditions and fed a standard diet. Retrospective analysis of environmental data (relative humidity, temperature) was carried out. Gross, histopathologic, scanning, and transmission electron microscopy examination of tails and limbs was performed. The incidence of ringtail was 0.075% (20/26 800) of all weaned litters over the 3-year period of examination. Temperature and relative humidity remained within accepted limits in all cases except one. We observed annular constrictions in tail, digits of pes, crus, and antebrachium in 116 (100.0%), 47 (40.5%), 11 (9.5%), and 2 (1.7%) of 116 affected mice, respectively. Histologic and ultrastructural examination revealed abnormal keratin desquamation and presence of a keratin ring encircling the tail, causing progressive strangulation of the growing tail with subsequent compression and ulceration of underlying soft tissues, resulting in circulatory changes (edema, hyperemia, thrombosis, hemorrhages), ischemic necrosis, and eventually auto-amputation distal to the constriction. On the basis of our findings, we suggest a disorder of cornification as the primary lesion of ringtail in mice. The cause of these cases, however, remained undetermined, even though traditional etiologic factors (relative humidity, temperature, diet, caging type) were reasonably excluded.
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Affiliation(s)
- C. Recordati
- Mouse & Animal Pathology Laboratory, Fondazione Filarete, Milano, Italy
| | - S. M. Basta
- Mouse & Animal Pathology Laboratory, Fondazione Filarete, Milano, Italy
- Dipartimento di Scienze Veterinarie e Sanità Pubblica, Università degli Studi di Milano, Milano, Italy
| | - L. Benedetti
- Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Milano, Italy
| | - F. Baldin
- Department of Experimental Oncology, European Institute of Oncology, Milano, Italy
- COGENTECH S.C.A.R.L., Milano, Italy
| | - M. Capillo
- Department of Experimental Oncology, European Institute of Oncology, Milano, Italy
- COGENTECH S.C.A.R.L., Milano, Italy
| | - E. Scanziani
- Mouse & Animal Pathology Laboratory, Fondazione Filarete, Milano, Italy
- Dipartimento di Scienze Veterinarie e Sanità Pubblica, Università degli Studi di Milano, Milano, Italy
| | - A. Gobbi
- Department of Experimental Oncology, European Institute of Oncology, Milano, Italy
- COGENTECH S.C.A.R.L., Milano, Italy
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31
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Nakagawa T. Strategies for developing novel therapeutics for sensorineural hearing loss. Front Pharmacol 2014; 5:206. [PMID: 25278894 PMCID: PMC4165348 DOI: 10.3389/fphar.2014.00206] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 08/20/2014] [Indexed: 01/01/2023] Open
Abstract
Sensorineural hearing loss (SNHL) is a common disability in the world; however, at present, options for the pharmacological treatment of SNHL are very limited. Previous studies involving human temporal bone analyses have revealed that the degeneration of the cochlea is a common mechanism of SNHL. A major problem for the development of novel pharmacotherapy for SNHL has been the limited regeneration capacity in mammalian cochlear cells. However, recent progress in basic studies has led to several effective strategies for the induction of regeneration in the mammalian cochlea, in accordance with the stage of degeneration. In addition, recent advances in the identification of human deafness genes and their characterization in mouse models have elucidated cellular and/or molecular mechanisms of SNHL, which will contribute to clarify molecular targets of pharmacotherapy for treatment of SNHL.
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Affiliation(s)
- Takayuki Nakagawa
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University Kyoto, Japan
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32
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Berthoud VM, Minogue PJ, Yu H, Snabb JI, Beyer EC. Connexin46fs380 causes progressive cataracts. Invest Ophthalmol Vis Sci 2014; 55:6639-48. [PMID: 25103261 PMCID: PMC4207115 DOI: 10.1167/iovs.14-15012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 07/28/2014] [Indexed: 01/17/2023] Open
Abstract
PURPOSE Although many connexin46 (Cx46) mutants have been linked to inherited human cataracts, there are no adequate animal models for their study. The current experiments were designed to characterize the consequences of expression of one such mutant, Cx46fs380, in the mouse lens. METHODS Mice expressing Cx46fs380 were generated by a knockin strategy. Levels and distribution of specific proteins were analyzed by immunoblotting and immunofluorescence. RESULTS Dark-field microscopy revealed that lenses of young heterozygous and homozygous Cx46fs380 mice did not have opacities, but they developed anterior nuclear cataracts that became more severe with age. Immunofluorescence and immunoblotting showed that Cx46 was severely reduced in both heterozygous and homozygous Cx46fs380 lenses at 1 month of age, whereas immunoreactive connexin50 (Cx50) was moderately decreased. The reduction in Cx50 became more severe in older lenses. The solubilities of crystallins from young wild-type and fs380 mice were similar, but older fs380 lenses exhibited abnormalities of abundance, solubility, and modification of some crystallins. CONCLUSIONS Major decreases in connexin levels precede the development of cataracts. These mice represent a useful model for elucidation of the progression of lens abnormalities during cataractogenesis especially as caused by a mutant connexin.
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Affiliation(s)
- Viviana M Berthoud
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
| | - Peter J Minogue
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
| | - Helena Yu
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
| | - Joseph I Snabb
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
| | - Eric C Beyer
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
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Martin PE, Easton JA, Hodgins MB, Wright CS. Connexins: sensors of epidermal integrity that are therapeutic targets. FEBS Lett 2014; 588:1304-14. [PMID: 24607543 DOI: 10.1016/j.febslet.2014.02.048] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 02/25/2014] [Accepted: 02/25/2014] [Indexed: 12/25/2022]
Abstract
Gap junction proteins (connexins) are differentially expressed throughout the multiple layers of the epidermis. A variety of skin conditions arise with aberrant connexin expression or function and suggest that maintaining the epidermal gap junction network has many important roles in preserving epidermal integrity and homeostasis. Mutations in a number of connexins lead to epidermal dysplasias giving rise to a range of dermatological disorders of differing severity. 'Gain of function' mutations reveal connexin-mediated roles in calcium signalling within the epidermis. Connexins are involved in epidermal innate immunity, inflammation control and in wound repair. The therapeutic potential of targeting connexins to improve wound healing responses is now clear. This review discusses the role of connexins in epidermal integrity, and examines the emerging evidence that connexins act as epidermal sensors to a variety of mechanical, temperature, pathogen-induced and chemical stimuli. Connexins thus act as an integral component of the skin's protective barrier.
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Affiliation(s)
- Patricia E Martin
- Department of Life Sciences and Institute for Applied Health Research, Glasgow Caledonian University, Glasgow G4 0BA, UK.
| | - Jennifer A Easton
- Department of Life Sciences and Institute for Applied Health Research, Glasgow Caledonian University, Glasgow G4 0BA, UK; Department of Dermatology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Malcolm B Hodgins
- Department of Life Sciences and Institute for Applied Health Research, Glasgow Caledonian University, Glasgow G4 0BA, UK
| | - Catherine S Wright
- Department of Life Sciences and Institute for Applied Health Research, Glasgow Caledonian University, Glasgow G4 0BA, UK
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Abstract
OBJECTIVE To review new insights into the pathophysiology of sensorineural hearing impairment. Specifically, we address defects of the ribbon synapses between inner hair cells and spiral ganglion neurons that cause auditory synaptopathy. DATA SOURCES AND STUDY SELECTION Here, we review original publications on the genetics, animal models, and molecular mechanisms of hair cell ribbon synapses and their dysfunction. CONCLUSION Hair cell ribbon synapses are highly specialized to enable indefatigable sound encoding with utmost temporal precision. Their dysfunctions, which we term auditory synaptopathies, impair audibility of sounds to varying degrees but commonly affect neural encoding of acoustic temporal cues essential for speech comprehension. Clinical features of auditory synaptopathies are similar to those accompanying auditory neuropathy, a group of genetic and acquired disorders of spiral ganglion neurons. Genetic auditory synaptopathies include alterations of glutamate loading of synaptic vesicles, synaptic Ca influx or synaptic vesicle turnover. Acquired synaptopathies include noise-induced hearing loss because of excitotoxic synaptic damage and subsequent gradual neural degeneration. Alterations of ribbon synapses likely also contribute to age-related hearing loss.
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Churko JM, Laird DW. Gap junction remodeling in skin repair following wounding and disease. Physiology (Bethesda) 2013; 28:190-8. [PMID: 23636264 DOI: 10.1152/physiol.00058.2012] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present review, we provide an overview of connexin expression during skin development and remodeling in wound healing, and reflect on how loss- or gain-of-function connexin mutations may change cellular phenotypes and lead to diseases of the skin. We also consider the therapeutic value of targeting connexins in wound healing.
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Affiliation(s)
- Jared M Churko
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
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36
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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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Xia CH, Chang B, DeRosa AM, Cheng C, White TW, Gong X. Cataracts and microphthalmia caused by a Gja8 mutation in extracellular loop 2. PLoS One 2012; 7:e52894. [PMID: 23300808 PMCID: PMC3530494 DOI: 10.1371/journal.pone.0052894] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 11/21/2012] [Indexed: 11/18/2022] Open
Abstract
The mouse semi-dominant Nm2249 mutation displays variable cataracts in heterozygous mice and smaller lenses with severe cataracts in homozygous mice. This mutation is caused by a Gja8(R205G) point mutation in the second extracellular loop of the Cx50 (or α8 connexin) protein. Immunohistological data reveal that Cx50-R205G mutant proteins and endogenous wild-type Cx46 (or α3 connexin) proteins form diffuse tiny spots rather than typical punctate signals of normal gap junctions in the lens. The level of phosphorylated Cx46 proteins is decreased in Gja8(R205G/R205G) mutant lenses. Genetic analysis reveals that the Cx50-R205G mutation needs the presence of wild-type Cx46 to disrupt lens peripheral fibers and epithelial cells. Electrophysiological data in Xenopus oocytes reveal that Cx50-R205G mutant proteins block channel function of gap junctions composed of wild-type Cx50, but only affect the gating of wild-type Cx46 channels. Both genetic and electrophysiological results suggest that Cx50-R205G mutant proteins alone are unable to form functional channels. These findings imply that the Gja8(R205G) mutation differentially impairs the functions of Cx50 and Cx46 to cause cataracts, small lenses and microphthalmia. The Gja8(R205G) mutation occurs at the same conserved residue as the human GJA8(R198W) mutation. This work provides molecular insights to understand the cataract and microphthalmia/microcornea phenotype caused by Gja8 mutations in mice and humans.
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Affiliation(s)
- Chun-hong Xia
- School of Optometry and Vision Science Program, University of California, Berkeley, California, United States of America
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Adam M. DeRosa
- Physiology and Biophysics, State University of New York – Stony Brook, Stony Brook, New York, United States of America
| | - Catherine Cheng
- School of Optometry and Vision Science Program, University of California, Berkeley, California, United States of America
| | - Thomas W. White
- Physiology and Biophysics, State University of New York – Stony Brook, Stony Brook, New York, United States of America
| | - Xiaohua Gong
- School of Optometry and Vision Science Program, University of California, Berkeley, California, United States of America
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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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Iossa S, Marciano E, Franzé A. GJB2 Gene Mutations in Syndromic Skin Diseases with Sensorineural Hearing Loss. Curr Genomics 2012; 12:475-785. [PMID: 22547955 PMCID: PMC3219843 DOI: 10.2174/138920211797904098] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 07/27/2011] [Accepted: 08/10/2011] [Indexed: 01/10/2023] Open
Abstract
The GJB2 gene is located on chromosome 13q12 and it encodes the connexin 26, a transmembrane protein involved in cell-cell attachment of almost all tissues. GJB2 mutations cause autosomal recessive (DFNB1) and sometimes dominant (DFNA3) non-syndromic sensorineural hearing loss. Moreover, it has been demonstrated that connexins are involved in regulation of growth and differentiation of epidermis and, in fact, GJB2 mutations have also been identified in syndromic disorders with hearing loss associated with various skin disease phenotypes. GJB2 mutations associated with skin disease are, in general, transmitted with a dominant inheritance pattern. Nonsyndromic deafness is caused prevalently by a loss-of-function, while literature evidences suggest for syndromic deafness a mechanism based on gain-of-function. The spectrum of skin manifestations associated with some mutations seems to have a very high phenotypic variability. Why some mutations can lead to widely varying cutaneous manifestations is poorly understood and in particular, the reason why the skin disease-deafness phenotypes differ from each other thus remains unclear. This review provides an overview of recent findings concerning pathogenesis of syndromic deafness imputable to GJB2 mutations with an emphasis on relevant clinical genotype-phenotype correlations. After describing connexin 26 fundamental characteristics, the most relevant and recent information about its known mutations involved in the syndromic forms causing hearing loss and skin problems are summarized. The possible effects of the mutations on channel expression and function are discussed.
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Scott CA, Tattersall D, O'Toole EA, Kelsell DP. Connexins in epidermal homeostasis and skin disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1952-61. [DOI: 10.1016/j.bbamem.2011.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 08/30/2011] [Accepted: 09/06/2011] [Indexed: 12/20/2022]
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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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42
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Wróbel M, Karlik M, Szaumkssel M, Rydzanicz M, Szyfter K, Szyfter W. [Comparison of different deafening strategies based on ototoxic drugs on mouse animals model]. Otolaryngol Pol 2012; 66:56-60. [PMID: 22381017 DOI: 10.1016/s0030-6657(12)70751-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Accepted: 09/27/2011] [Indexed: 11/19/2022]
Abstract
AIM OF THE STUDY To compare safety, reliability and usefulness of two deafening protocols on animal mouse model, based on aminoglycosides exposure MATERIAL AND METHOD Adults mice, Bulb/C, deafened with kanamycine 14 days treatment (group I), single kanamycin injection followed by etacrinic acid administration (group II) and control group. Hearing evaluation performed with ABR recordings on 6th day after drug exposure RESULTS Both protocols were not able to guarantee complete ablation of the inner ear in tested animals. Although short deafening strategy was more effective (83.33% deaf mice) it was combined with high rate of mortality during general anesthesia for hearing evaluation. CONCLUSIONS Variable outcomes in deafening mouse animal model implies the necessity of hearing evaluation every time prior to the pathophysiological as well as molecular studies. Mice exposed to severe oto- and nephrotoxic insult do not recover after anesthetic drug administration, thus harvesting inner ear tissues especially as the source of RNA should be performed immediately after ABR recordings.
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Affiliation(s)
- Maciej Wróbel
- Klinika Otolaryngologii i Onkologii Laryngologicznej Uniwersytetu Medycznego w Poznaniu.
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Mese G, Sellitto C, Li L, Wang HZ, Valiunas V, Richard G, Brink PR, White TW. The Cx26-G45E mutation displays increased hemichannel activity in a mouse model of the lethal form of keratitis-ichthyosis-deafness syndrome. Mol Biol Cell 2011; 22:4776-86. [PMID: 22031297 PMCID: PMC3237621 DOI: 10.1091/mbc.e11-09-0778] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Mutations in the GJB2 gene (Cx26) cause deafness in humans. Most are loss-of-function mutations and cause nonsyndromic deafness. Some mutations produce a gain of function and cause syndromic deafness associated with skin disorders, such as keratitis-ichthyosis-deafness syndrome (KIDS). Cx26-G45E is a lethal mutation linked to KIDS that forms constitutively active connexin hemichannels. The pathomechanism(s) by which mutant Cx26 hemichannels perturb normal epidermal cornification are poorly understood. We created an animal model for KIDS by generating an inducible transgenic mouse expressing Cx26-G45E in keratinocytes. Cx26-G45E mice displayed reduced viability, hyperkeratosis, scaling, skin folds, and hair loss. Histopathology included hyperplasia, acanthosis, papillomatosis, increased cell size, and osteal plugging. These abnormalities correlated with human KIDS pathology and were associated with increased hemichannel currents in transgenic keratinocytes. These results confirm the pathogenic nature of the G45E mutation and provide a new model for studying the role of aberrant connexin hemichannels in epidermal differentiation and inherited connexin disorders.
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Affiliation(s)
- Gulistan Mese
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA
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Degen J, Schütz M, Dicke N, Strenzke N, Jokwitz M, Moser T, Willecke K. Connexin32 can restore hearing in connexin26 deficient mice. Eur J Cell Biol 2011; 90:817-24. [PMID: 21813206 DOI: 10.1016/j.ejcb.2011.05.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 04/20/2011] [Accepted: 05/03/2011] [Indexed: 12/15/2022] Open
Abstract
Functional gap junction channels composed of certain connexin proteins are essential for the function of the cochlea. Homozygous deficiency in the Gjb2 (mice) or GJB2 (human) gene coding for connexin26 (Cx26) in the cochlea leads to hearing impairment in mice and humans, respectively. Here we have studied the functional equivalence of Cx26 and connexin32 (Cx32) isoforms in the cochlea. We analyzed a conditional mouse mutant in which the Gjb2 coding DNA was exchanged by LacZ DNA coding for the reporter protein beta-galactosidase. This allowed us to follow the unrestricted and cell type specific expression of Gjb2 promoter activity. After inner ear specific, Otogelin-Cre recombinase mediated deletion of the loxP-site-flanked LacZ coding DNA, transcription of the Gjb1 gene, coding for Cx32 was activated by the Gjb2 promoter. Interbreeding of these mice with conditional Gjb2 null mice resulted in animals in which Cx32 instead of Cx26 protein is expressed in the non-sensory epithelial network of the cochlea. When we analyzed the auditory function in these mice, we found that the expression of Cx32 protein is sufficient to support hearing in the absence of Cx26. Thus Cx32 can functionally replace Cx26 in the mouse cochlea resulting in almost normal hearing.
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Affiliation(s)
- Joachim Degen
- Institute of Genetics, University of Bonn, 53117 Bonn, Germany
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Abstract
Cx (connexin) proteins are components of gap junctions which are aqueous pores that allow intercellular exchange of ions and small molecules. Mutations in Cx genes are linked to a range of human disorders. In the present review we discuss mutations in β-Cx genes encoding Cx26, Cx30, Cx30.3 and Cx31 which lead to skin disease and deafness. Functional studies with Cx proteins have given insights into disease-associated mechanisms and non-gap junctional roles for Cx proteins.
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Affiliation(s)
- K Natsuga
- Department of Dermatology, Hokkaido University Graduate School of Medicine, North 15 West 7, Sapporo 060-8638, Japan.
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