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Mammano F, Paller AS, White TW. Connexin Hemichannel Inhibition and Human Genodermatoses. J Invest Dermatol 2024:S0022-202X(24)02053-0. [PMID: 39269388 DOI: 10.1016/j.jid.2024.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2024] [Revised: 07/29/2024] [Accepted: 08/07/2024] [Indexed: 09/15/2024]
Abstract
Pathogenic variants in genes encoding connexins that cause skin diseases, such as keratitis-ichthyosis-deafness (KID) syndrome and hidrotic ectodermal dysplasia (HED) or Clouston syndrome, display increased hemichannel activity. Mechanistic insights derived from biophysical studies of the variant connexins support the hypothesis that inhibition of the acquired hemichannel activity could alleviate epidermal pathology. Use of pharmacological blockers and engineered mAbs in mouse models of HED and KID confirm that hemichannel inhibition is a promising target for new therapeutic approaches to KID and HED. Insights from this work could apply to other connexin-based genetic skin diseases in which hemichannel activity is elevated.
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Affiliation(s)
- Fabio Mammano
- Institute of Biochemistry and Cell Biology, Italian National Research Council, Rome, Italy; Department of Physics and Astronomy "G. Galilei", University of Padova, Padova, Italy
| | - Amy S Paller
- Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook, New York, USA.
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Sanecka A, Biernacka EK, Sosna M, Mueller-Malesinska M, Ploski R, Skarzynski H, Piotrowicz R. Evaluation of electrocardiographic parameters in patients with hearing loss genotyped for the connexin 26 gene (GJB2) mutations. Braz J Otorhinolaryngol 2016; 83:176-182. [PMID: 27177978 PMCID: PMC9442716 DOI: 10.1016/j.bjorl.2016.02.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 02/22/2016] [Accepted: 02/28/2016] [Indexed: 11/17/2022] Open
Abstract
Introduction Several studies have associated congenital sensorineural hearing loss in children with prolongation of the cardiac parameter QTc. The cause of this association is unknown. At the same time, mutations in GJB2, which encodes connexin 26, are the most common cause of congenital hearing impairment. Objective To compare electrocardiographic parameters (PR interval, QRS complex, and QTc interval) in patients with hearing loss who were tested for mutations in GJB2 and GJB6 to investigate whether these mutations affect electrical activity of the heart. Methods 346 patients (176 males, 170 females) with sensorineural hearing loss of 30 dB HL or more, aged 21.8 ± 19.9 years (including 147 children <14 years), underwent both genetic study for GJB2 and GJB6 mutations and electrocardiography. Results Mutations in GJB2, including homozygotes and heterozygotes, were found in 112 (32%) patients. There were no significant differences in ECG parameters between groups of patients with and without mutations in GJB2. No differences were observed either in men (mean PR with mutation: 155 ± 16.6 vs. 153.6 ± 30.1 without; QRS: 99.9 ± 9.9 vs. 101.1 ± 15.4; QTc: 414.9 ± 29.9 vs. 412.4 ± 25.7) or women (mean PR with: 148.7 ± 21 vs. 143.8 ± 22.8 without; QRS: 94.8 ± 7.6 vs. 92.9 ± 9.6; QTc: 416.8 ± 20.6 vs. 424.9 ± 22.8). In similar fashion, we did we find any significant differences between groups of children with and without GJB2 mutations (mean PR with: 126.3 ± 19.6 vs. 127 ± 19.7 without; QRS: 80.7 ± 9.5 vs. 79.4 ± 11.6; QTc: 419.7 ± 23.5 vs. 419.8 ± 24.8). Conclusion No association was found between the presence of GJB2 mutations encoding connexin 26 in patients with hearing loss and their ECG parameters (PR, QRS, QTc).
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Affiliation(s)
| | | | - Magdalena Sosna
- Institute of Physiology and Pathology of Hearing, World Hearing Center, Nadarzyn, Poland
| | | | - Rafal Ploski
- Medical University of Warsaw, Department of Medical Genetics, Warsaw, Poland
| | - Henryk Skarzynski
- Institute of Physiology and Pathology of Hearing, World Hearing Center, Nadarzyn, Poland.
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3
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Kelly JJ, Shao Q, Jagger DJ, Laird DW. Cx30 exhibits unique characteristics including a long half-life when assembled into gap junctions. J Cell Sci 2015; 128:3947-60. [DOI: 10.1242/jcs.174698] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 09/08/2015] [Indexed: 01/04/2023] Open
Abstract
In the present study we investigated the life-cycle, trafficking, assembly and cell surface dynamics of a poorly characterized connexin family member, connexin 30 (Cx30), which plays a critical role in skin health and hearing. Unexpectedly, Cx30 localization at the cell surface and gap junctional intercellular communication was not affected by prolonged treatments with the ER-Golgi transport inhibitor brefeldin-A or the protein synthesis inhibitor cycloheximide, whereas Cx43 was rapidly cleared. Fluorescent recovery after photobleaching revealed that Cx30 plaques were rebuilt from the outer edges in keeping with older channels residing in the inner core of the plaque. Expression of a dominant-negative form of Sar1 GTPase led to the accumulation of Cx30 within the ER in contrast to a report that Cx30 traffics via a Golgi-independent pathway. Co-expression of Cx30 with Cx43 revealed that these connexins segregate into distinct domains within common gap junction plaques suggesting their assembly is governed by different mechanisms. In summary, Cx30 was found to be an unusually stable, long-lived connexin (half-life >12 hrs), which may underlie its specific role in the epidermis and cochlea.
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Affiliation(s)
- John J. Kelly
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
| | - Qing Shao
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
| | | | - Dale W. Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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Gupta LK, Saini P, Khare AK, Mittal A. Progressive symmetric erythrokeratoderma: report of an Indian family. Int J Dermatol 2014; 53:e317-9. [PMID: 24601895 DOI: 10.1111/ijd.12334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Lalit Kumar Gupta
- Department of Dermatology, venereology and leprosy, Rabindra Nath Tagore Medical College, Udaipur, India.
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Vele O, Schrijver I. Inherited hearing loss: molecular genetics and diagnostic testing. ACTA ACUST UNITED AC 2013; 2:231-48. [PMID: 23495655 DOI: 10.1517/17530059.2.3.231] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Hearing loss is a clinically and genetically heterogeneous condition with major medical and social consequences. It affects up to 8% of the general population. OBJECTIVE This review recapitulates the principles of auditory physiology and the molecular basis of hearing loss, outlines the main types of non-syndromic and syndromic deafness by mode of inheritance, and provides an overview of current clinically available genetic testing. METHODS This paper reviews the literature on auditory physiology and on genes, associated with hearing loss, for which genetic testing is presently offered. RESULTS/CONCLUSION The advent of molecular diagnostic assays for hereditary hearing loss permits earlier detection of the underlying causes, facilitates appropriate interventions, and is expected to generate the data necessary for more specific genotype-phenotype correlations.
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Affiliation(s)
- Oana Vele
- Stanford University School of Medicine, Department of Pathology and Pediatrics, L235, 300 Pasteur Drive, Stanford, CA 94305, USA +1 650 724 2403 ; +1 650 724 1567 ;
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Neoh CY, Chen H, Ng SK, Lane EB, Common JEA. A rare connexin 26 mutation in a patient with a forme fruste of keratitis-ichthyosis-deafness (KID) syndrome. Int J Dermatol 2009; 48:1078-81. [PMID: 19785089 DOI: 10.1111/j.1365-4632.2009.04136.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Keratitis-ichthyosis-deafness (KID) syndrome is a rare ectodermal dysplasia characterized by generalized erythrokeratotic plaques, sensorineural hearing loss, and vascularizing keratitis. Cutaneous changes and hearing loss typically present in early childhood, whereas ocular symptoms present later. Mutations in the connexin (Cx) 26 gene, GJB2, are now established to underlie many of the affected cases, with the majority of patients harboring the p.D50N mutation. METHODS A rare patient demonstrating features of incomplete KID syndrome associated with an uncommon Cx26 gene mutation is described. RESULTS The patient presented late in adolescence with partial features of KID syndrome. There was limited cutaneous involvement and the rare association of cystic acne. Both hearing impairment and ophthalmic involvement were mild in severity. Genetic mutation analysis revealed a previously described, rare mutation in GJB2, resulting in a glycine to arginine change at codon 12 (p.G12R). CONCLUSIONS This report describes a patient exhibiting characteristics suggestive of a late-onset, incomplete form of KID syndrome with the GJB2 mutation (p.G12R). The p.G12R mutation has only been described in one other patient with KID syndrome, whose clinical presentation was not characterized.
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Affiliation(s)
- Ching Yin Neoh
- National Skin Center, Institute of Medical Biology, 1 Mandalay Road, Singapore.
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Fenwick A, Richardson RJ, Butterworth J, Barron MJ, Dixon MJ. Novel mutations in GJA1 cause oculodentodigital syndrome. J Dent Res 2008; 87:1021-6. [PMID: 18946008 DOI: 10.1177/154405910808701108] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Oculodentodigital syndrome (ODD) is a rare, usually autosomal-dominant disorder that is characterized by developmental abnormalities of the face, eyes, teeth, and limbs. The most common clinical findings include a long, narrow nose, short palpebral fissures, type III syndactyly, and dental abnormalities including generalized microdontia and enamel hypoplasia. Recently, it has been shown that mutations in the gene GJA1, which encodes the gap junction protein connexin 43, underlie oculodentodigital syndrome. Gap junction communication between adjacent cells is known to be vital during embryogenesis and subsequently for normal tissue homeostasis. Here, we report 8 missense mutations in the coding region of GJA1, 6 of which have not been described previously, in ten unrelated families diagnosed with ODD. In addition, immunofluorescence analyses of a developmental series of mouse embryos and adult tissue demonstrates a strong correlation between the sites of connexin 43 expression and the clinical phenotype displayed by individuals affected by ODD.
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Affiliation(s)
- A Fenwick
- Faculty of Life Sciences and Dental School, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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8
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Mazereeuw-Hautier J. Syndrome de keratitis-ichthyosis-deafness (KID). Ann Dermatol Venereol 2008; 135:80-2; quiz 79, 83. [DOI: 10.1016/j.annder.2007.11.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Accepted: 11/14/2007] [Indexed: 11/15/2022]
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Laird DW. Closing the gap on autosomal dominant connexin-26 and connexin-43 mutants linked to human disease. J Biol Chem 2007; 283:2997-3001. [PMID: 18089569 DOI: 10.1074/jbc.r700041200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cells within the vast majority of human tissues communicate directly through clustered arrays of intercellular channels called gap junctions. Gene ablation studies in mouse models have revealed that these intercellular channels are necessary for a variety of organ functions and that some of these genes are essential for survival. Molecular genetics has uncovered that germ line mutations in nearly half of the genes that encode the 21-member connexin family of gap junction proteins are linked to one or more human diseases. Frequently, these mutations are autosomal recessive, whereas in other cases, autosomal dominant mutations manifest as disease. Given the broad and overlapping distribution of connexins in a wide arrangement of tissues, it is hard to predict where connexin-linked diseases will clinically manifest. For instance, the most prevalent connexin in the human body is connexin-43 (Cx43), yet autosomal dominant mutations in the GJA1 gene, which encodes Cx43, exhibit modest developmental disorders resulting in a disease termed oculodentodigital dysplasia. Autosomal recessive mutations in the gene encoding Cx26 result in moderate to severe sensorineural hearing loss, whereas autosomal dominant mutations produce hearing loss and a wide range of skin diseases, including palmoplantar keratoderma. Here, we will focus on autosomal dominant mutations of the genes encoding Cx26 and Cx43 in relation to models that link genotypes to phenotypic outcomes with particular reference to how these approaches provide insight into human disease.
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Affiliation(s)
- Dale W Laird
- Departments of Anatomy & Cell Biology and Physiology & Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada.
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Wang CM, Lincoln J, Cook JE, Becker DL. Abnormal connexin expression underlies delayed wound healing in diabetic skin. Diabetes 2007; 56:2809-17. [PMID: 17717278 DOI: 10.2337/db07-0613] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE Dynamically regulated expression of the gap junction protein connexin (Cx)43 plays pivotal roles in wound healing. Cx43 is normally downregulated and Cx26 upregulated in keratinocytes at the edge of the wound as they adopt a migratory phenotype. We have examined the dynamics of Cx expression during wound healing in diabetic rats, which is known to be slow. RESEARCH DESIGN AND METHODS We induced diabetes with streptozotocin and examined Cx expression and communication in intact and healing skin. RESULTS We found that diabetes decreased Cx43 and Cx26 protein and communication in the intact epidermis and increased Cx43 protein and communication in the intact dermis. Diabetes also altered the dynamic changes of Cxs associated with wound healing. Within 24 h, Cx43 was upregulated in a thickened bulb of keratinocytes at the wound edge (rather than downregulated as in controls, which formed a thin process of migratory cells). Cx43 decline was delayed until 48 h, when reepithelialization began. Although Cx26 was upregulated as normal after wounding in diabetic skin, its distribution at the wound edge was abnormal, being more widespread. Application of Cx43-specific antisense gel to diabetic wounds prevented the abnormal upregulation of Cx43 and doubled the rate of reepithelialization, which exceeded control levels. CONCLUSIONS Cx expression in diabetic skin is abnormal, as is the dynamic response of Cx43 to injury, which may underlie the delayed healing of diabetic wounds. Preventing the upregulation of Cx43 in diabetic wounds significantly improves the rate of healing and clearly has potential therapeutic value.
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Affiliation(s)
- Chiuhui Mary Wang
- Department of Anatomy and Developmental Biology, University College London, Gower Street, London, WC1E 6BT, UK
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Bavamian S, Klee P, Britan A, Populaire C, Caille D, Cancela J, Charollais A, Meda P. Islet-cell-to-cell communication as basis for normal insulin secretion. Diabetes Obes Metab 2007; 9 Suppl 2:118-32. [PMID: 17919186 DOI: 10.1111/j.1463-1326.2007.00780.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The emergence of pancreatic islets has necessitated the development of a signalling system for the intra- and inter-islet coordination of beta cells. With evolution, this system has evolved into a complex regulatory network of partially cross-talking pathways, whereby individual cells sense the state of activity of their neighbours and, accordingly, regulate their own level of functioning. A consistent feature of this network in vertebrates is the expression of connexin (Cx)-36-made cell-to-cell channels, which cluster at gap junction domains of the cell membrane, and which adjacent beta cells use to share cytoplasmic ions and small metabolites within individual islets. This chapter reviews what is known about Cx36, and the mechanism whereby this beta-cell connexin significantly regulates insulin secretion. It further outlines other less established functions of the protein and evaluates its potential relevance for the development of novel therapeutic approaches to diabetes.
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Affiliation(s)
- S Bavamian
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, Genève, Switzerland
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Arita K, Nanda A, Wessagowit V, Akiyama M, Alsaleh QA, McGrath JA. A novel mutation in the VDR gene in hereditary vitamin D-resistant rickets. Br J Dermatol 2007; 158:168-71. [PMID: 17970811 DOI: 10.1111/j.1365-2133.2007.08232.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- K Arita
- Genetic Skin Disease Group, St John's Institute of Dermatology, Division of Genetics and Molecular Medicine, The Guy's, King's College and St Thomas' School of Medicine, London, UK.
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Yum SW, Zhang J, Valiunas V, Kanaporis G, Brink PR, White TW, Scherer SS. Human connexin26 and connexin30 form functional heteromeric and heterotypic channels. Am J Physiol Cell Physiol 2007; 293:C1032-48. [PMID: 17615163 DOI: 10.1152/ajpcell.00011.2007] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutations in GJB2 and GJB6, the genes that encode the human gap junction proteins connexin26 (Cx26) and connexin30 (Cx30), respectively, cause hearing loss. Cx26 and Cx30 are both expressed in the cochlea, leading to the potential formation of heteromeric hemichannels and heterotypic gap junction channels. To investigate their interactions, we expressed human Cx26 and Cx30 individually or together in HeLa cells. When they were expressed together, Cx26 and Cx30 appeared to interact directly (by their colocalization in gap junction plaques, by coimmunoprecipitation, and by fluorescence resonance energy transfer). Scrape-loading cells that express either Cx26 or Cx30 demonstrated that Cx26 homotypic channels robustly transferred both cationic and anionic tracers, whereas Cx30 homotypic channels transferred cationic but not anionic tracers. Cells expressing both Cx26 and Cx30 also transferred both cationic and anionic tracers by scrape loading, and the rate of calcein (an anionic tracer) transfer was intermediate between their homotypic counterparts by fluorescence recovery after photobleaching. Fluorescence recovery after photobleaching also showed that Cx26 and Cx30 form functional heterotypic channels, allowing the transfer of calcein, which did not pass the homotypic Cx30 channels. Electrophysiological recordings of cell pairs expressing different combinations of Cx26 and/or Cx30 demonstrated unique gating properties of cell pairs expressing both Cx26 and Cx30. These results indicate that Cx26 and Cx30 form functional heteromeric and heterotypic channels, whose biophysical properties and permeabilities are different from their homotypic counterparts.
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Affiliation(s)
- Sabrina W Yum
- Section of Neurology, St. Christopher's Hospital for Children, Erie Ave. at Front St., Philadelphia, PA 19134, USA.
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Retamal MA, Schalper KA, Shoji KF, Orellana JA, Bennett MVL, Sáez JC. Possible involvement of different connexin43 domains in plasma membrane permeabilization induced by ischemia-reperfusion. J Membr Biol 2007; 218:49-63. [PMID: 17705051 DOI: 10.1007/s00232-007-9043-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2007] [Accepted: 06/15/2007] [Indexed: 01/04/2023]
Abstract
In vitro and in vivo studies support the involvement of connexin 43-based cell-cell channels and hemichannels in cell death propagation induced by ischemia-reperfusion. In this context, open connexin hemichannels in the plasma membrane have been proposed to act as accelerators of cell death. Progress on the mechanisms underlying the cell permeabilization induced by ischemia-reperfusion reveals the involvement of several factors leading to an augmented open probability and increased number of hemichannels on the cell surface. While open probability can be increased by a reduction in extracellular concentration of divalent cations and changes in covalent modifications of connexin 43 (oxidation and phosphorylation), increase in number of hemichannels requires an elevation of the intracellular free Ca(2+) concentration. Reversal of connexin 43 redox changes and membrane permeabilization can be induced by intracellular, but not extracellular, reducing agents, suggesting a cytoplasmic localization of the redox sensor(s). In agreement, hemichannels formed by connexin 45, which lacks cytoplasmic cysteines, or by connexin 43 with its C-terminal domain truncated to remove its cysteines are insensitive to reducing agents. Although further studies are required for a precise localization of the redox sensor of connexin 43 hemichannels, modulation of the redox potential is proposed as a target for the design of pharmacological tools to reduce cell death induced by ischemia-reperfusion in connexin 43-expressing cells.
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Affiliation(s)
- Mauricio A Retamal
- Departamento de Ciencias Fisiológicas, Pontificia Universidad Católica de Chile, Alameda 340, Santiago, Chile
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Thomas T, Shao Q, Laird DW. Differentiation of Organotypic Epidermis in the Presence of Skin Disease-Linked Dominant-Negative Cx26 Mutants and Knockdown Cx26. J Membr Biol 2007; 217:93-104. [PMID: 17638039 DOI: 10.1007/s00232-007-9036-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Accepted: 05/14/2007] [Indexed: 10/23/2022]
Abstract
In this study, we chose a differentiation-competent rat epidermal keratinocyte (REK) cell line to examine the role of Cx26 and disease-linked Cx26 mutants in organotypic epidermal differentiation. First, we generated stable REK cell lines expressing three skin disease-linked mutants (G59A, D66H and R75W). Second, we used an RNAi approach to knock down the expression of Cx26 in REKs. Interestingly, the three-dimensional (3D) architecture of the organotypic epidermis altered the intracellular spatial distribution of the mutants in comparison to 2D cultured REKs, highlighting the importance of using organotypic cultures. Unexpectedly, the presence of disease-linked mutants or the overexpression of wild-type Cx26 had little effect on the differentiation of the organotypic epidermis as determined by the architecture of the epidermis, expression of molecular markers indicative of epidermis differentiation (keratin 10, keratin 14, involucrin, loricrin) and stratification/cornification of the epidermis. Likewise, organotypic epidermis continued to differentiate normally upon Cx26 knockdown. While Cx26 has been reported to be upregulated during wound healing, no reduction in wound closure was observed in 2D REK cultures that expressed loss-of-function, dominant Cx26 mutants. In conclusion, we demonstrate that gain or loss of Cx26 function does not disrupt organotypic epidermal differentiation and offer insights into why patients harboring Cx26 mutations do not frequently present with more severe disease that encompasses thin skin.
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Affiliation(s)
- Tamsin Thomas
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
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Gong XQ, Shao Q, Langlois S, Bai D, Laird DW. Differential potency of dominant negative connexin43 mutants in oculodentodigital dysplasia. J Biol Chem 2007; 282:19190-202. [PMID: 17420259 DOI: 10.1074/jbc.m609653200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Oculodentodigital dysplasia (ODDD) is a congenital autosomal dominant disorder with phenotypic variability, which has been associated with mutations in the GJA1 gene encoding connexin43 (Cx43). Given that Cx43 mutants are thought to be equally co-expressed with wild-type Cx43 in ODDD patients, it is imperative to examine the consequence of these mutants in model systems that reflect this molar ratio. To that end, we used differential fluorescent protein tagging of mutant and wild-type Cx43 to quantitatively monitor the ratio of mutant/wild-type within the same putative gap junction plaques and co-immunoprecipitation to determine if the mutants interact with wild-type Cx43. Together the fluorescence-based assay was combined with patch clamp analysis to assess the dominant negative potency of Cx43 mutants. Our results revealed that the ODDD-linked Cx43 mutants, G21R and G138R, as well as amino terminus green fluorescent protein-tagged Cx43, were able to co-localize with wild-type Cx43 at the gap junction plaque-like structures and to co-immunoprecipitate with wild-type Cx43. All Cx43 mutants demonstrated dominant negative action on gap junctional conductance of wild-type Cx43 but not that of Cx32. More interestingly, these Cx43 mutants demonstrated different potencies in inhibiting the function of wild-type Cx43 with the G21R mutant being two times more potent than the G138R mutant. The potency difference in the dominant negative properties of ODDD-linked Cx43 mutants may have clinical implications for the various symptoms and disease severity observed in ODDD patients.
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Affiliation(s)
- Xiang-Qun Gong
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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Wiszniewski L, Sanz J, Scerri I, Gasparotto E, Dudez T, Lacroix JS, Suter S, Gallati S, Chanson M. Functional expression of connexin30 and connexin31 in the polarized human airway epithelium. Differentiation 2007; 75:382-92. [PMID: 17428265 DOI: 10.1111/j.1432-0436.2007.00157.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Gap junctions are documented in the human airway epithelium but the functional expression and molecular identity of their protein constituents (connexins, Cx) in the polarized epithelium is not known. To address this question, we documented the expression of a family of epithelial Cx (Cx26, Cx30, Cx30.3, Cx31, Cx31.1, Cx32, Cx37, Cx40, and Cx43) in primary human airway epithelial cells (AEC) grown on porous supports. Under submerged conditions, AEC formed a monolayer of airway cells whereas the air-liquid interface induced within 30-60 days AEC differentiation into a polarized epithelium for up to 6-9 months. Maturation of AEC was associated with the down-regulation of Cx26 and Cx43. The well-differentiated airway epithelium exhibited gap junctional communication between ciliated and between ciliated and basal cells. Interestingly, Cx30 was mostly present between ciliated cells whereas Cx31 was found between basal cells. These results are supportive of the establishment of signal-selective gap junctions with maturation of AEC, likely contributing to support airway epithelium function. These results lay the ground for studying the role of Cx-mediated cell-cell communication during repair following AEC injury and exploring Cx-targeted interventions to modulate the healing process.
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Affiliation(s)
- Ludovic Wiszniewski
- Laboratory of Clinical Investigation III, Department of Pediatrics, Geneva University Hospitals, Geneva, Switzerland
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Maher AC, Thomas T, Riley JL, Veitch G, Shao Q, Laird DW. Rat epidermal keratinocytes as an organotypic model for examining the role of Cx43 and Cx26 in skin differentiation. ACTA ACUST UNITED AC 2007; 12:219-30. [PMID: 16531317 DOI: 10.1080/15419060500511818] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
In order to characterize connexin expression and regulation in the epidermis, we have characterized a rat epidermal keratinocyte (REK) cell line that is phenotypically similar to basal keratinocytes in that they have the ability to differentiate into organotypic epidermis consisting of a basal cell layer, 2-3 suprabasal cell layers, and a cornified layer. RT-PCR revealed that REK cells express mRNA for Cx26, Cx31, Cx31.1, Cx37, and Cx43, which mimics the reported connexin profile for rat tissue. In addition, we report the expression of Cx30, Cx30.3, Cx40, and Cx45 in rat keratinocytes, highlighting the complexity of the connexin complement in rat epidermis. Furthermore, 3-dimensional analysis of organotypic skin revealed that Cx26 and Cx43 are exquisitely regulated during the differentiation process. The life-cycle of these connexins including their expression, transport, assembly into gap junctions, internalization, and degradation are elegantly depicted in organotypic epidermis as keratinocytes proceed from differentiation to programmed cell death.
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Affiliation(s)
- Amy C Maher
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada
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19
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Chanson M, Kwak BR. Connexin37: a potential modifier gene of inflammatory disease. J Mol Med (Berl) 2007; 85:787-95. [PMID: 17318613 DOI: 10.1007/s00109-007-0169-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Revised: 01/31/2007] [Accepted: 02/01/2007] [Indexed: 12/22/2022]
Abstract
There is an increasing appreciation of the importance of gap junction proteins (connexins) in modulating the severity of inflammatory diseases. Multiple epidemiological gene association studies have detected a link between a single nucleotide polymorphism in the human connexin37 (Cx37) gene and coronary artery disease or myocardial infarction in various populations. This C1019T polymorphism causes a proline-to-serine substitution (P319S) in the regulatory C terminal tail of Cx37, a protein that is expressed in the vascular endothelium as well as in monocytes and macrophages. Indeed, these three cell types are key players in atherogenesis. In the early phases of atherosclerosis, blood monocytes are recruited to the sites of injury in response to chemotactic factors. Monocytes adhere to the dysfunctional endothelium and transmigrate across endothelial cells to penetrate the arterial intima. In the intima, monocytes proliferate, mature, and accumulate lipids to progress into macrophage foam cells. This review focuses on Cx37 and its impact on the cellular and molecular events underlying tissue function, with particular emphasis of the contribution of the C1019T polymorphism in atherosclerosis. We will also discuss evidence for a potential mechanism by which allelic variants of Cx37 are differentially predictive of increased risk for inflammatory diseases.
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Affiliation(s)
- Marc Chanson
- Department of Pediatrics, Geneva University Hospitals, 1211, Geneva 14, Switzerland
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20
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González D, Gómez-Hernández JM, Barrio LC. Species specificity of mammalian connexin-26 to form open voltage-gated hemichannels. FASEB J 2006; 20:2329-38. [PMID: 17077310 DOI: 10.1096/fj.06-5828com] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Mutations of connexin-26 (Cx26) cause nonsyndromic hearing loss and other syndromes affecting ectoderm-derived tissues. While the exact mechanisms underlying these diseases remain elusive, Cx's are generally considered to mediate cell-to-cell communication by forming gap junction channels. We show here that unlike rat Cx26, human and sheep Cx26 form voltage-gated hemichannels when expressed in oocytes and Neuro2A cells. A single evolutionary amino acidic change at position 159 of the rodent protein, the replacement of aspartic acid with asparagine in the human and sheep proteins, accounts for this species specificity. At the resting potential and in normal millimolar extracellular calcium, open human Cx26 hemichannels can be detected both electrophysiologically and by dye uptake, although they did not affect cell viability. These hemichannels opened at approximately -50 mV and their activation increased by depolarization until they inactivate at positive membrane potentials. Single-channel analysis revealed that activation and inactivation involved two distinct voltage gating mechanisms and that the fully open hemichannel displays a conductance twice that of the intercellular channel. The existence of a hemichannel that opens under physiological control of the membrane potential may have important implications for the normal and pathological activity of Cx26 in humans, particularly with respect to hearing and the epidermis.
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Affiliation(s)
- Daniel González
- Unit of Experimental Neurology, Research Department, Ramón y Cajal Hospital, Madrid, Spain
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21
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Functional Characterization of a GJA1 Frameshift Mutation Causing Oculodentodigital Dysplasia and Palmoplantar Keratoderma. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84095-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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22
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Gong XQ, Shao Q, Lounsbury CS, Bai D, Laird DW. Functional Characterization of aGJA1Frameshift Mutation Causing Oculodentodigital Dysplasia and Palmoplantar Keratoderma. J Biol Chem 2006; 281:31801-11. [PMID: 16891658 DOI: 10.1074/jbc.m605961200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A frameshift mutation generated from a dinucleotide deletion (780-781del) in the GJA1 gene encoding Cx43 results in a frameshift yielding 46 aberrant amino acids after residue 259 and a shortened protein of 305 residues compared with the 382 in wild-type Cx43. This frameshift mutant (fs260) causes oculodentodigital dysplasia (ODDD) that includes the added condition of palmoplantar keratoderma. When expressed in a variety of cell lines, the fs260 mutant was typically localized to the endoplasmic reticulum and other intracellular compartments. The fs260 mutant, but not the G138R ODDD-linked Cx43 mutant or a Cx43 mutant truncated at residue 259 (T259), reduced the number of apparent gap junction plaques formed from endogenous Cx43 in normal rat kidney cells or keratinocytes. Interestingly, mutation of a putative FF endoplasmic reticulum retention motif encoded within the 46 aberrant amino acid domain failed to restore efficient assembly of the fs260 mutant into gap junctions. Dual whole cell patch-clamp recording revealed that fs260-expressing N2A cells exerted severely reduced electrical coupling in comparison to wild-type Cx43 or the T259 mutant, whereas single patch capacitance recordings showed that fs260 could also dominantly inhibit the function of wild-type Cx43. Co-expression studies further revealed that the dominant negative effect of fs260 on wild-type Cx43 was dose-dependent, and at a predicted 1:1 expression ratio the fs260 mutant reduced wild-type Cx43-mediated gap junctional conductance by over 60%. These results suggest that the 46 aberrant amino acid residues associated with the frameshift mutant are, at least in part, responsible for the manifestation of palmoplantar keratoderma symptoms.
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Affiliation(s)
- Xiang-Qun Gong
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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23
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Abstract
Evaluation of the human genome suggests that all members of the connexin family of gap-junction proteins have now been successfully identified. This large and diverse family of proteins facilitates a number of vital cellular functions coupled with their roles, which range from the intercellular propagation of electrical signals to the selective intercellular passage of small regulatory molecules. Importantly, the extent of gap-junctional intercellular communication is under the direct control of regulatory events associated with channel assembly and turnover, as the vast majority of connexins have remarkably short half-lives of only a few hours. Since most cell types express multiple members of the connexin family, compensatory mechanisms exist to salvage tissue function in cases when one connexin is mutated or lost. However, numerous studies of the last decade have revealed that mutations in connexin genes can also lead to severe and debilitating diseases. In many cases, single point mutations lead to dramatic effects on connexin trafficking, assembly and channel function. This review will assess the current understanding of wild-type and selected disease-linked mutant connexin transport through the secretory pathway, gap-junction assembly at the cell surface, internalization and degradation.
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Affiliation(s)
- Dale W Laird
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada N6A 5C1.
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Nlend RN, Michon L, Bavamian S, Boucard N, Caille D, Cancela J, Charollais A, Charpantier E, Klee P, Peyrou M, Populaire C, Zulianello L, Meda P. Connexin36 and pancreatic beta-cell functions. Arch Physiol Biochem 2006; 112:74-81. [PMID: 16931449 DOI: 10.1080/13813450600712019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Most cell types are functionally coupled by connexin (Cx) channels, i.e. exchange cytoplasmic ions and small metabolites through gap junction domains of their membrane. This form of direct cell-to-cell communication occurs in all existing animals, whatever their position in the phylogenetic scale, and up to humans. Pancreatic beta-cells are no exception, and normally cross-talk with their neighbors via channels made of Cx36. These exchanges importantly contribute to coordinate and synchronize the function of individual cells within pancreatic islets, particularly in the context of glucose-induced insulin secretion. Compelling evidence now indicates that Cx36-mediated coupling, and/or the Cx36 protein per se, play significant regulatory roles in various beta-cell functions, ranging from the biosynthesis, storage and release of insulin. Recent preliminary data further suggest that the protein may also be implicated in the balance of beta-cell growth versus necrosis and apoptosis, and in the regulated expression of specific genes. Here, we review this evidence, discuss the possible involvement of Cx36 in the pathophysiology of diabetes, and evaluate the relevance of this connexin in the therapeutic approaches to the disease.
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Affiliation(s)
- Rachel Nlend Nlend
- Department of Cell Physiology and Metabolism, University of Geneva, Medical School, 1211 Genève 4, Switzerland
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Abrams CK, Freidin MM, Verselis VK, Bargiello TA, Kelsell DP, Richard G, Bennett MVL, Bukauskas FF. Properties of human connexin 31, which is implicated in hereditary dermatological disease and deafness. Proc Natl Acad Sci U S A 2006; 103:5213-8. [PMID: 16549784 PMCID: PMC1458820 DOI: 10.1073/pnas.0511091103] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The connexins are a family of at least 20 homologous proteins in humans that form aqueous channels connecting the interiors of coupled cells and mediating electrical and chemical communication. Mutations in the gene for human connexin 31 (hCx31) are associated with disorders of the skin and auditory system. Alterations in functional properties of Cx31 junctions are likely to play a role in these diseases; nonetheless, little is known about the properties of the wild-type channels. Here we show that hCx31 channels, like other connexin channels, are gated by voltage and close at low pH and when exposed to long-chain alkanols. Single-channel conductance of the fully open channel is approximately 85 pS, and it is permeable to Lucifer yellow, Alexa Fluor(350), ethidium bromide, and DAPI, which have valences of -2, -1, +1, and +2, respectively. In contrast to what has been reported for mouse Cx31, hCx31 appears to form functional heterotypic channels with all four connexins tested, Cx26, Cx30, Cx32, and Cx45. These findings provide an important first step in evaluating the pathogenesis of inherited human diseases associated with mutations in the gene for Cx31.
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Affiliation(s)
- Charles K. Abrams
- Departments of *Neuroscience, and
- Neurology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461
- To whom correspondence may be addressed. E-mail:
or
| | | | | | | | - David P. Kelsell
- Centre for Cutaneous Research, Institute for Cell and Molecular Science, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, 2 Newark Street, Whitechapel, London E1 2AT, United Kingdom; and
| | | | - Michael V. L. Bennett
- Departments of *Neuroscience, and
- To whom correspondence may be addressed. E-mail:
or
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26
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Affiliation(s)
- Rahul J Anand
- Division of Pediatric Surgery, Children's Hospital of Pittsburgh, Pittsburgh, PA, USA
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27
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Common JEA, O'Toole EA, Leigh IM, Thomas A, Griffiths WAD, Venning V, Grabczynska S, Peris Z, Kansky A, Kelsell DP. Clinical and Genetic Heterogeneity of Erythrokeratoderma Variabilis. J Invest Dermatol 2005; 125:920-7. [PMID: 16297190 DOI: 10.1111/j.0022-202x.2005.23919.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The skin disease erythrokeratoderma variabilis (EKV) has been shown to be associated with mutations in GJB3 and GJB4 encoding connexin (Cx)31 and Cx30.3, respectively. Gap junctions composed of Cx proteins are intracellular channels providing a mechanism of synchronized cellular response facilitating metabolic and electronic functions of the cell. In the skin, Cx31 and Cx30.3 are expressed in the stratum granulosum of the epidermis with a suggested role in late keratinocyte differentiation. Molecular investigations of GJB3 and GJB4 were performed in five pedigrees and three sporadic cases of EKV. Mutational analyzes revealed disease-associated Cx31 or Cx30.3 mutations in only three probands of which two were novel mutations and one was a recurrent mutation. These genetic studies further demonstrate the heterogeneous nature of the erythrokeratodermas as not all individuals that were clinically diagnosed with EKV harbor Cx31 or Cx30.3 mutations.
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Affiliation(s)
- John E A Common
- Centre for Cutaneous Research, Institute of Cell and Molecular Science, Barts and the London School of Medicine and Dentistry, Queen Mary, University of London, Whitechapel, London, UK
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28
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Abstract
The term 'erythrokeratodermas' or 'erythrokeratodermias' has been applied to a group of inherited disorders characterized by well-demarcated erythematous lesions and hyperkeratotic plaques. Connexin mutations have been demonstrated to be responsible for most cases of erythrokeratoderma variabilis but there remain some cases without demonstrated connexin mutations, suggesting genetic heterogeneity. The position of progressive symmetric erythrokeratoderma has become rather unclear. Loricin mutations have been found in some cases that clinically resemble variant Vohwinkel syndrome and other cases have features that overlap with those of erythrokeratoderma variablis. Whether progressive symmetric erythrokeratoderma exists as a distinct entity is under question.
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Affiliation(s)
- Maureen Rogers
- Department of Dermatology, The Children's Hospital at Westmead, Sydney, New South Wales, Australia.
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Chanson M, Derouette JP, Roth I, Foglia B, Scerri I, Dudez T, Kwak BR. Gap junctional communication in tissue inflammation and repair. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1711:197-207. [PMID: 15955304 DOI: 10.1016/j.bbamem.2004.10.005] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2004] [Revised: 10/12/2004] [Accepted: 10/14/2004] [Indexed: 11/18/2022]
Abstract
Local injury induces a complex orchestrated response to stimulate healing of injured tissues, cellular regeneration and phagocytosis. Practically, inflammation is defined as a defense process whereby fluid and white blood cells accumulate at a site of injury. The balance of cytokines, chemokines, and growth factors is likely to play a key role in regulating important cell functions such as migration, proliferation, and matrix synthesis during the process of inflammation. Hence, the initiation, maintenance, and resolution of innate responses depend upon cellular communication. A process similar to tissue repair and subsequent scarring is found in a variety of fibrotic diseases. This may occur in a single organ such as liver, kidneys, pancreas, lung, skin, and heart, but fibrosis may also have a more generalized distribution such as in atherosclerosis. The purpose of this review is to summarize recent advances on the contribution of gap junction-mediated intercellular communication in the modulation of the inflammatory response and tissue repair.
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Affiliation(s)
- Marc Chanson
- Laboratory of Clinical Investigation III, Department of Pediatrics, HUG-P.O. BOX 14, Micheli-du-Crest, 24, 1211 Geneva 14, Switzerland.
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30
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Abstract
Tremendous progress has been made in our understanding of the molecular basis of hearing and hearing loss. Through recent advances, we have begun to understand the fascinating biology of the auditory system and unveiled new molecular mechanisms of hearing impairment. Changes in the diagnostic impact of genetic testing have occurred, as well as exciting developments in therapeutic options. Molecular diagnosis, which is already a reality for several hearing-associated genes, will doubtlessly continue to increase in the near future, both in terms of the number of mutations tested and the spectrum of genes. Genetic analysis for hearing loss is mostly used for diagnosis and treatment, and relatively rarely for reproductive decisions, in contrast to other inherited disorders. Inherited hearing loss, however, is characterized by impressive genetic heterogeneity. An abundance of genes carry a large number of mutations, but specific mutations in a single gene may lead to syndromic or non-syndromic hearing loss. Some mutations predominate in individual ethnic groups. For clinical and laboratory diagnosticians, it is challenging to keep abreast of the unfolding discoveries. This review aims to provide the framework pertinent to diagnosticians and a practical approach to mutation analysis in the hearing impaired.
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Affiliation(s)
- Iris Schrijver
- Department of Pathology and Pediatrics, L235, Stanford University Medical Center, 300 Pasteur Drive, Stanford, CA 94305, USA.
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31
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Di WL, Gu Y, Common JEA, Aasen T, O'Toole EA, Kelsell DP, Zicha D. Connexin interaction patterns in keratinocytes revealed morphologically and by FRET analysis. J Cell Sci 2005; 118:1505-14. [PMID: 15769851 DOI: 10.1242/jcs.01733] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Multiple connexins, the major proteins of gap junctions, have overlapping expression in the human epidermis and are postulated to have a key role in keratinocyte differentiation and homeostasis. The functional importance of connexins in the epidermis is emphasised by the association of mutations in four human connexins with various hyperproliferative skin disorders. As immunohistochemistry demonstrated overlapping expression of specific connexins in keratinocytes, we performed colocalisation analyses and applied a modified FRET methodology to assess possible heteromeric interactions between different combinations of four wild-type (wt) and mutant connexins. The data generated indicate that there is evidence for multiple connexin interactions at the plasma membrane between (wt)Cx26, (wt)Cx30 and (wt)Cx31 in keratinocytes and thus, the potential for the formation of a large number of different channel types each with different channel properties. In addition, we demonstrate that the inherent in vitro trafficking defect of the skin disease mutations (D50N)Cx26 and (G11R)Cx30 can be overcome partially by the coexpression of different wild-type connexins but this rescue does not result in large gap junction aggregates at the plasma membrane. These data indicate that skin disease associated Cx26 or Cx30 mutations are likely to disrupt a number of different channel types important in distinct aspects of keratinocyte biology.
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Affiliation(s)
- Wei-Li Di
- Centre for Cutaneous Research, Institute of Cell and Molecular Science, Barts and the London School of Medicine and Dentistry, Queen Mary, University of London, 4 Newark Street, London E1 2AT, UK
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Bygum A, Betz RC, Kragballe K, Steiniche T, Peeters N, Wuyts W, Nöthen MM. KID Syndrome: Report of a Scandinavian Patient with Connexin‐26 Gene Mutation. Acta Derm Venereol 2005; 85:152-5. [PMID: 15823911 DOI: 10.1080/00015550410024148] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Keratitis-ichthyosis-deafness syndrome is a rare genodermatosis, which has recently been connected with mutations in the connexin-26 gene, GJB2. We present a 15-year-old boy with erythroderma, hyperkeratotic plaques and deafness. Sequencing analysis showed a heterozygous missense mutation D50N (148G>A) in GJB2. The boy has not yet manifested characteristic eye lesions but his case shows that tardy development of eye signs should not preclude a clinical diagnosis of keratitis-ichthyosis-deafness syndrome. Besides the typical clinical features, the patient's height was above the 98th percentile and he displayed a delayed bone age in his hands. Additionally, he suffered from migrainoid headaches and the results of a magnetic resonance scan of the cerebrum showed he had a large cisterna magna which probably occurred independently from the syndrome. This patient is the first Danish patient in whom the keratitis-ichthyosis-deafness syndrome has been verified by mutation analysis.
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Affiliation(s)
- Anette Bygum
- Department of Dermatology, Odense University Hospital, 5000 Odense C, Denmark.
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33
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Binder B, Hennies HC, Kraschl R, Smolle J. Connexin-26-Mutation bei "Keratitis-Ichthyosis-Deafness"-Syndrom (KID-Syndrom). Connexin 26 mutation and keratitis-ichthyosis-deafness (KID) Syndrome. J Dtsch Dermatol Ges 2005; 3:105-8. [PMID: 16351012 DOI: 10.1111/j.1610-0378.2005.04748.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Keratitis-ichthyosis-deafness syndrome (KID syndrome) is an extremely rare disorder. Inheritance is autosomal dominant but many cases occur sporadically following a spontaneous mutation. The cause of KID syndrome are missense mutations of the gene GJB2, encoding connexin 26. PATIENTS AND METHODS We clinically studied two cases of KID syndrome and extracted genomic DNA from peripheral blood. RESULTS The patients showed different heterozygous mutations of the connexin 26 gene and had quite different clinical courses. CONCLUSIONS Both patients showed heterozygous mutations of the connexin 26 gene; a different Cx26 dominant mutation can cause a very different clinical course.
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Affiliation(s)
- Barbara Binder
- Univ.-Klinik für Dermatologie und Venerologie, Graz, Osterreich.
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Affiliation(s)
- Mary Beth Dinulos
- Department of Pediatrics, Section of Genetics and Child Development, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756, USA.
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35
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Abstract
Hair and nails are skin appendages that share with other ectodermal tissues a common developmental pathway. Inherited disorders affecting these two structures therefore very often involve other epithelial components and present with multiple anomalies, generating both physical and psychological distress among patients and their families. The present review briefly describes major recent advances in our understanding of hair and nail genodermatoses.
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Affiliation(s)
- Eli Sprecher
- Department of Dermatology and the Laboratory of Molecular Dermatology, Rambam Medical Center, Haifa 31096, Israel.
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36
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Abstract
PURPOSE OF REVIEW Many genodermatoses have been linked in recent years to their respective genes. The underlying biology and integrative nature of these genes with other genes and organ systems is beginning to be understood. This paper reviews recent advances in neurocutaneous disorders, ectodermal dysplasias, and the phenomenon of revertant gene mosaicism. RECENT FINDINGS In neurofibromatosis type 1, molecular assays are being developed to distinguish malignant from benign and premalignant lesions. Clinical mutation analysis for the NF1 gene has been problematic; a sensitive new assay using automated comparative sequence analysis may be helpful. Revision of clinical care guidelines is ongoing. New data for the prospective management of optic pathway gliomas is reviewed. The two genes that underlie tuberous sclerosis complex, tuberin and hamartin, lie at the center of an important signal transduction pathway with significant implications for pharmacologic treatment. Issues in genetic counseling for this highly variable disease are updated. Extensive progress has been made in understanding the basis of several forms of ectodermal dysplasia. Disorders caused by mutations in p63 and the connexin and NF-kappaB gene families will be reviewed. Finally, phenotypic in vivo amelioration of genodermatoses via revertant gene mosaicism will be discussed as a possible mechanism to be exploited in directed therapeutic approaches. SUMMARY This paper reviews recent developments in the molecular and biologic bases of neurofibromatosis type 1, tuberous sclerosis, and ectodermal disorders related to p63 and the connexin and NF-kappaB gene families. The concept of revertant gene mosaicism is also discussed as a potential model for gene therapy.
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Affiliation(s)
- Rhonda E Schnur
- Division of Genetics, Department of Pediatrics, Cooper University Hospital/Robert Wood Johnson Medical School, Camden, New Jersey 08103, USA.
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37
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Richard G, Brown N, Ishida-Yamamoto A, Krol A. Expanding The Phenotypic Spectrum of Cx26 Disorders: Bart–Pumphrey Syndrome is Caused by a Novel Missense Mutation in GJB2. J Invest Dermatol 2004; 123:856-63. [PMID: 15482471 DOI: 10.1111/j.0022-202x.2004.23470.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bart-Pumphrey syndrome (BPS) is an autosomal dominant disorder characterized by sensorineural hearing loss, palmoplantar keratoderma, knuckle pads, and leukonychia, which show considerable phenotypic variability. The clinical features partially overlap with Vohwinkel syndrome and Keratitis-Ichthyosis-Deafness syndrome, both disorders caused by dominant mutations in the GJB2 gene encoding the gap junction protein connexin-26, suggesting an etiological relationship. We report here a novel GJB2 mutation N54K segregating in a family with BPS, which was not detected in 110 control individuals of Northern European ancestry. This non-conservative missense mutation lies within a cluster of pathogenic GJB2 mutations affecting the evolutionary conserved first extracellular loop of Cx26 important for docking of connexin hemichannels and voltage gating. Immunostaining of Cx26 in lesional palmar and knuckle skin was weak or absent, although its adnexal expression appeared normal and the punctate membrane staining of Cx26 and other epidermal connexins was not altered. Nevertheless, the widespread immunostaining of Cx30 throughout the spinous cell layers suggested a compensatory overexpression. Our results emphasize that pleiotropic GJB2 mutations are responsible for at least 5 overlapping dermatological disorders associated with syndromic hearing loss and cover a wide range of severity and organ involvement.
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Affiliation(s)
- Gabriele Richard
- Department of Dermatology and Cutaneous Biology, and Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
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38
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Abstract
Gap junctions contain hydrophilic membrane channels that allow direct communication between neighboring cells through the diffusion of ions, metabolites, and small cell signaling molecules. They are made up of a hexameric array of polypeptides encoded by the connexin multi-gene family. Cell-cell communication mediated by connexins is crucial to various cellular functions, including the regulation of cell growth, differentiation, and development. Mutations in connexin genes have been linked to a variety of human diseases, including cardiovascular anomalies, peripheral neuropathy, deafness, skin disorders, and cataracts. In addition to their coupling function, recent studies suggest that connexin proteins may also mediate signaling. This could involve interactions with other protein partners that may play a role not only in connexin assembly, trafficking, gating and turnover, but also in the coordinate regulation of cell-cell communication with cell adhesion and cell motility. The integration of these cell functions is likely to be important in the role of gap junctions in development and disease.
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Affiliation(s)
- Chih-Jen Wei
- Laboratory of Developmental Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.
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Jan AY, Amin S, Ratajczak P, Richard G, Sybert VP. Genetic heterogeneity of KID syndrome: identification of a Cx30 gene (GJB6) mutation in a patient with KID syndrome and congenital atrichia. J Invest Dermatol 2004; 122:1108-13. [PMID: 15140211 DOI: 10.1111/j.0022-202x.2004.22518.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Connexins are integral membrane proteins forming aqueous gap junction channels that allow the diffusional exchange of ions and small metabolites between cells, thus coordinating metabolic activities in multicellular tissues. Dominant mutations in the Cx26 gene GJB2 have been shown to cause keratitis-ichthyosis-deafness (KID) syndrome, palmoplantar keratoderma associated with hearing loss, and Vohwinkel syndrome. Missense mutations in the closely related Cx30 gene GJB6 underlie Clouston syndrome (autosomal dominant hidrotic ectodermal dysplasia). We report a 6-y-old boy with phenotypic characteristics of KID syndrome as well as atrichia. In contrast to other KID syndrome patients, molecular analysis of the connexin gene GJB2 did not disclose a pathogenic mutation, although the patient was homozygous for a common polymorphism (V27I) in the coding sequence of Cx26. Nevertheless, screening of GJB6 revealed a heterozygous missense mutation (V37E) predicted to alter sequence and charge of the first transmembrane helix of Cx30, which was previously implicated in Clouston syndrome (Smith et al, 2002). The presence of a pathogenic Cx30 mutation and the lack of a pathologic molecular change in Cx26 in this patient, whose clinical features predominantly resemble KID syndrome, suggest genetic heterogeneity of KID syndrome and underscore that mutations in Cx30, similar to those in Cx26 or Cx31, can cause different phenotypes. Based on our results, connexin gene mutations should be considered in patients presenting with congenital sensorineural hearing loss and disorders of cornification, and screening of several connexin genes with known cutaneous phenotype, such as those for Cx26, Cx30, Cx30.3, and Cx31, may be required.
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Affiliation(s)
- Amy Y Jan
- Division of Dermatology, Department of Medicine, University of Washington, Seattle, WA, USA
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Christiansen J, Dyck JD, Elyas BG, Lilley M, Bamforth JS, Hicks M, Sprysak KA, Tomaszewski R, Haase SM, Vicen-Wyhony LM, Somerville MJ. Chromosome 1q21.1 contiguous gene deletion is associated with congenital heart disease. Circ Res 2004; 94:1429-35. [PMID: 15117819 DOI: 10.1161/01.res.0000130528.72330.5c] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Congenital heart disease (CHD), comprising structural or functional abnormalities present at birth, is the most common birth defect in humans. Reduced expression of connexin40 (Cx40) has been found in association with atrial fibrillation, and deletion of Cx40 in a mouse model causes various structural heart abnormalities in 18% of heterozygotes. We screened 505 unrelated CHD cases for deletions or duplications of the Cx40 gene (GJA5) by real-time quantitative PCR, in order to determine whether altered copy number of this gene may be associated with a cardiac phenotype in humans. Dosage of Cx40 flanking genes (ACPL1 and Cx50 gene, GJA8) was determined by real-time PCR for all apparent positive cases. In total, 3 cases were found to carry deletions on chromosome 1q21.1 spanning ACPL1, Cx40, and Cx50 genes. Absence of heterozygosity was observed in all 3 index cases over a 1.5- to 3-Mb region. Samples from the parents of two cases were obtained, and microsatellites across 1q21.1 were genotyped. One of the apparently unaffected parents was found to carry this deletion. All 3 index cases presented with obstruction of the aortic arch as the common structural cardiac malformation, and had no consistent dysmorphic features. Genotyping of 520 unrelated normal controls for this deletion was negative. We hypothesize that this 1q21.1 multigene deletion is associated with a range of cardiac defects, with anomalies of the aortic arch being a particular feature.
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MESH Headings
- Acid Phosphatase/genetics
- Adolescent
- Adult
- Animals
- Aorta, Thoracic/abnormalities
- Aorta, Thoracic/embryology
- Child
- Child, Preschool
- Chromosomes, Human, Pair 1/genetics
- Chromosomes, Human, Pair 1/ultrastructure
- Computer Systems
- Connexins/deficiency
- Connexins/genetics
- Eye Proteins/genetics
- Female
- Gene Deletion
- Heart Defects, Congenital/embryology
- Heart Defects, Congenital/genetics
- Humans
- Infant
- Infant, Newborn
- Loss of Heterozygosity
- Male
- Mice
- Microsatellite Repeats
- Models, Animal
- Penetrance
- Polymerase Chain Reaction
- Gap Junction alpha-5 Protein
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Affiliation(s)
- Jesse Christiansen
- Department of Medical Genetics, University of Alberta Edmonton, Alberta, Canada
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