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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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Alsabbagh MM. Keratitis-ichthyosis-deafness syndrome: A comprehensive review of cutaneous and systemic manifestations. Pediatr Dermatol 2023; 40:19-27. [PMID: 36444857 DOI: 10.1111/pde.15201] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 11/05/2022] [Indexed: 11/30/2022]
Abstract
Keratitis-ichthyosis-deafness syndrome is a rare genetic disease presenting with cutaneous, ocular, and otic defects. This comprehensive review provides insight into the clinical presentations, highlighting the cutaneous manifestations including histopathology and treatment options.
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Affiliation(s)
- Manahel Mahmood Alsabbagh
- Department of Molecular Medicine, Princess Al-Jawhara Center for Molecular Medicine and Inherited Disorders, Arabian Gulf University, Manama, Kingdom of Bahrain
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Keratitis-ichthyosis-deafness Syndrome with Heterozygous p.D50N in the GJB2 Gene in Two Serbian Adult Patients. Balkan J Med Genet 2022; 25:79-84. [PMID: 36880041 PMCID: PMC9985354 DOI: 10.2478/bjmg-2022-0014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023] Open
Abstract
Purpose Keratitis-ichthyosis-deafness (KID) syndrome is a rare congenital ectodermal dysplastic syndrome presenting with keratitis, ichthyosis and sensorineural hearing loss. The most common causes of KID syndrome are heterozygous missense mutations in the GJB2 gene that codes for connexin 26. Case report During the ophthalmological examination, two adult females complained of recent worsening of visual acuity in both eyes. Anamnesis revealed that their eyes were red and irritated from early childhood onwards. Both of them had thickening and keratinisation of eyelid margins, lash loss, diffuse opacification of cornea and conjunctiva caused by keratinisation of eye surface, superficial and deep corneal vascularisation and corneal oedema. Partial sensorineural hearing loss and difficulties in speech were also noted along with typical ichthyosiform erythroderma. Genetic testing of the GJB2 gene revealed a heterozygous p.D50N mutation in both patients.Patients were treated with a combined topical corticosteroid and artificial tears therapy, with steroid therapy being intensified during the last month. The therapy increased the visual acuity by decreasing corneal oedema and by forming a more regular air-tear interface during the six months follow up. Subsequently, the disease progressed despite the continuation of the therapy. Conclusion This is the first report of Serbian patients with KID syndrome. Despite the administration of the combined topical corticosteroid and artificial tears therapy the disease is relentlessly progressive and therapeutic success of ophthalmological signs with local therapeutic modalities used so far had been disappointing.
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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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Cohen-Barak E, Mwassi B, Zagairy F, Danial-Farran N, Khayat M, Tatour Y, Ziv M. Parental mosaic cutaneous-gonadal GJB2 mutation: From epidermal nevus to inherited ichthyosis-deafness syndrome. J Dermatol 2021; 49:379-382. [PMID: 34889473 DOI: 10.1111/1346-8138.16268] [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: 08/29/2021] [Revised: 11/10/2021] [Accepted: 11/22/2021] [Indexed: 11/26/2022]
Abstract
Ichthyosis and deafness syndrome is a group of devastating genodermatoses caused by heterozygous mutations in GJB2, encoding the gap junction protein connexin 26. These syndromes are characterized by severe skin disease, hearing loss, recurrent infections, and cutaneous neoplasms. Cutaneous somatic mutations in the same gene are associated with porokeratotic eccrine ostial dermal duct nevus. Here we report a family in which a parent presented with localized epidermal nevus and his child suffered with hystrix-like ichthyosis with deafness. Histologic examination of the parent's cutaneous lesion revealed verrucous epidermal nevus without features of porokeratotic eccrine ostial dermal duct nevus. Genetic analysis identified the same pathogenic variant, GJB2 c.148G>A (p.D50N), in DNA extracted from the parent's cutaneous lesion and the child's leukocytes, but not in the parent's leukocytes. This study expands the phenotypic heterogeneity of GJB2 mosaic variants in addition to porokeratotic eccrine ostial dermal duct nevus, and emphasizes the importance of molecular diagnosis of mosaic skin diseases considering the risk of severe inherited diseases in the offspring.
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Affiliation(s)
- Eran Cohen-Barak
- Department of Dermatology, "Emek" Medical Center, Afula, Israel.,Bruce and Ruth Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Bannan Mwassi
- Department of Dermatology, "Emek" Medical Center, Afula, Israel.,Bruce and Ruth Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Fadia Zagairy
- Department of Dermatology, "Emek" Medical Center, Afula, Israel
| | | | - Morad Khayat
- The Genetic Institute, "Emek" Medical Center, Afula, Israel
| | - Yasmin Tatour
- The Genetic Institute, "Emek" Medical Center, Afula, Israel
| | - Michael Ziv
- Department of Dermatology, "Emek" Medical Center, Afula, Israel
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Gap Junction Channelopathies and Calmodulinopathies. Do Disease-Causing Calmodulin Mutants Affect Direct Cell-Cell Communication? Int J Mol Sci 2021; 22:ijms22179169. [PMID: 34502077 PMCID: PMC8431743 DOI: 10.3390/ijms22179169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 08/19/2021] [Accepted: 08/21/2021] [Indexed: 11/24/2022] Open
Abstract
The cloning of connexins cDNA opened the way to the field of gap junction channelopathies. Thus far, at least 35 genetic diseases, resulting from mutations of 11 different connexin genes, are known to cause numerous structural and functional defects in the central and peripheral nervous system as well as in the heart, skin, eyes, teeth, ears, bone, hair, nails and lymphatic system. While all of these diseases are due to connexin mutations, minimal attention has been paid to the potential diseases of cell–cell communication caused by mutations of Cx-associated molecules. An important Cx accessory protein is calmodulin (CaM), which is the major regulator of gap junction channel gating and a molecule relevant to gap junction formation. Recently, diseases caused by CaM mutations (calmodulinopathies) have been identified, but thus far calmodulinopathy studies have not considered the potential effect of CaM mutations on gap junction function. The major goal of this review is to raise awareness on the likely role of CaM mutations in defects of gap junction mediated cell communication. Our studies have demonstrated that certain CaM mutants affect gap junction channel gating or expression, so it would not be surprising to learn that CaM mutations known to cause diseases also affect cell communication mediated by gap junction channels.
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Lee TL, Lin PH, Chen PL, Hong JB, Wu CC. Hereditary Hearing Impairment with Cutaneous Abnormalities. Genes (Basel) 2020; 12:43. [PMID: 33396879 PMCID: PMC7823799 DOI: 10.3390/genes12010043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Revised: 12/25/2020] [Accepted: 12/26/2020] [Indexed: 12/15/2022] Open
Abstract
Syndromic hereditary hearing impairment (HHI) is a clinically and etiologically diverse condition that has a profound influence on affected individuals and their families. As cutaneous findings are more apparent than hearing-related symptoms to clinicians and, more importantly, to caregivers of affected infants and young individuals, establishing a correlation map of skin manifestations and their underlying genetic causes is key to early identification and diagnosis of syndromic HHI. In this article, we performed a comprehensive PubMed database search on syndromic HHI with cutaneous abnormalities, and reviewed a total of 260 relevant publications. Our in-depth analyses revealed that the cutaneous manifestations associated with HHI could be classified into three categories: pigment, hyperkeratosis/nail, and connective tissue disorders, with each category involving distinct molecular pathogenesis mechanisms. This outline could help clinicians and researchers build a clear atlas regarding the phenotypic features and pathogenetic mechanisms of syndromic HHI with cutaneous abnormalities, and facilitate clinical and molecular diagnoses of these conditions.
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Affiliation(s)
- Tung-Lin Lee
- Department of Medical Education, National Taiwan University Hospital, Taipei City 100, Taiwan;
| | - Pei-Hsuan Lin
- Department of Otolaryngology, National Taiwan University Hospital, Taipei 11556, Taiwan;
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei City 100, Taiwan;
| | - Pei-Lung Chen
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei City 100, Taiwan;
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei City 100, Taiwan
- Department of Medical Genetics, National Taiwan University Hospital, Taipei 10041, Taiwan
- Department of Internal Medicine, National Taiwan University Hospital, Taipei 10041, Taiwan
| | - Jin-Bon Hong
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei City 100, Taiwan
- Department of Dermatology, National Taiwan University Hospital, Taipei City 100, Taiwan
| | - Chen-Chi Wu
- Department of Otolaryngology, National Taiwan University Hospital, Taipei 11556, Taiwan;
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei City 100, Taiwan;
- Department of Medical Genetics, National Taiwan University Hospital, Taipei 10041, Taiwan
- Department of Medical Research, National Taiwan University Biomedical Park Hospital, Hsinchu City 300, Taiwan
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Caroppo F, Szekely S, Fortina AB. Novel Variant c.148G>T of GJB2 Gene in a 5-Year-Old Child with KID Syndrome. Indian Dermatol Online J 2020; 11:1014-1015. [PMID: 33344363 PMCID: PMC7735005 DOI: 10.4103/idoj.idoj_603_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 09/15/2020] [Accepted: 10/13/2020] [Indexed: 11/23/2022] Open
Affiliation(s)
- Francesca Caroppo
- Pediatric Dermatology Unit - Department of Medicine DIMED, University of Padova, Padova, Italy
| | - Serena Szekely
- Pediatric Dermatology Unit - Department of Medicine DIMED, University of Padova, Padova, Italy
| | - Anna B Fortina
- Pediatric Dermatology Unit - Department of Medicine DIMED, University of Padova, Padova, Italy
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Bettoli V, Forconi R, Pezzini I, Martinello R, Scuderi V, Zedde P, Schettini N, Pacetti L, Corazza M. KID Syndrome and Hidradenitis Suppurativa: A Rare Association Responding to Surgical Treatment. Skin Appendage Disord 2020; 7:21-24. [PMID: 33614714 DOI: 10.1159/000509042] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 05/29/2020] [Indexed: 11/19/2022] Open
Abstract
Background Keratitis-ichthyosis-deafness (KID) syndrome is a rare genodermatosis characterized by keratitis, neurosensorial auditory impairment and ichthyosiform skin involvement. Frequent complications of the syndrome are chronic, opportunistic cutaneous infections, and the development of skin cancers. Several cases of association between KID syndrome and other conditions, including hidradenitis suppurativa (HS), are described in the literature. This correlation could be explained by the hyperproliferative state of the epidermis, which occurs in KID syndrome and may favor follicular plugging. Objectives The aim of this study was to describe a very rare case of association between KID syndrome and HS and its complex therapeutic management. Results The failure of the drugs commonly used in HS and the excellent results of surgery, although difficult to achieve, were experienced. Conclusion Despite the technical difficulties related to surgery, namely, cutaneous superinfections, frequent dehisce of the suture, and closure by secondary intention, the authors strongly recommend the surgical approach in these patients.
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Affiliation(s)
- Vincenzo Bettoli
- Section of Dermatology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Riccardo Forconi
- Section of Dermatology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Ilaria Pezzini
- Plastic and Reconstructive Surgery, Azienda Ospedaliero-Universitaria di Ferrara, Arcispedale Sant'Anna, Ferrara, Italy
| | - Ruby Martinello
- Department of Morphology, Surgery and Experimental Medicine, Institute of Obstetrics and Gynecology, University of Ferrara, Ferrara, Italy
| | - Valeria Scuderi
- Section of Dermatology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Piera Zedde
- Section of Dermatology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Natale Schettini
- Section of Dermatology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Lucrezia Pacetti
- Section of Dermatology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Monica Corazza
- Section of Dermatology, Department of Medical Sciences, University of Ferrara, Ferrara, Italy
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Lee MY, Wang HZ, White TW, Brooks T, Pittman A, Halai H, Petrova A, Xu D, Hart SL, Kinsler VA, Di WL. Allele-Specific Small Interfering RNA Corrects Aberrant Cellular Phenotype in Keratitis-Ichthyosis-Deafness Syndrome Keratinocytes. J Invest Dermatol 2019; 140:1035-1044.e7. [PMID: 31705875 DOI: 10.1016/j.jid.2019.09.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 08/16/2019] [Accepted: 09/17/2019] [Indexed: 11/29/2022]
Abstract
Keratitis-ichthyosis-deafness (KID) syndrome is a severe, untreatable condition characterized by ocular, auditory, and cutaneous abnormalities, with major complications of infection and skin cancer. Most cases of KID syndrome (86%) are caused by a heterozygous missense mutation (c.148G>A, p.D50N) in the GJB2 gene, encoding gap junction protein Cx26, which alters gating properties of Cx26 channels in a dominant manner. We hypothesized that a mutant allele-specific small interfering RNA could rescue the cellular phenotype in patient keratinocytes (KCs). A KID syndrome cell line (KID-KC) was established from primary patient KCs with a heterozygous p.D50N mutation. This cell line displayed impaired gap junction communication and hyperactive hemichannels, confirmed by dye transfer, patch clamp, and neurobiotin uptake assays. A human-murine chimeric skin graft model constructed with KID-KCs mimicked patient skin in vivo, further confirming the validity of these cells as a model. In vitro treatment with allele-specific small interfering RNA led to robust inhibition of the mutant GJB2 allele without altering expression of the wild-type allele. This corrected both gap junction and hemichannel activity. Notably, allele-specific small interfering RNA treatment caused only low-level off-target effects in KID-KCs, as detected by genome-wide RNA sequencing. Our data provide an important proof-of-concept and model system for the potential use of allele-specific small interfering RNA in treating KID syndrome and other dominant genetic conditions.
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Affiliation(s)
- Ming Yang Lee
- Infection, Immunity and Inflammation Programme/Immunobiology Section, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Hong-Zhan Wang
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York
| | - Tony Brooks
- UCL Genomics, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Alan Pittman
- Molecular Neuroscience, UCL Institute of Neurology, London, United Kingdom; Genetics Research Centre, St George's, University of London, London, United Kingdom
| | - Heerni Halai
- Infection, Immunity and Inflammation Programme/Immunobiology Section, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Anastasia Petrova
- Infection, Immunity and Inflammation Programme/Immunobiology Section, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Diane Xu
- Infection, Immunity and Inflammation Programme/Immunobiology Section, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Stephen L Hart
- Department of Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Veronica A Kinsler
- Department of Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London, United Kingdom; Paediatric Dermatology, Great Ormond Street Hospital for Children, London, United Kingdom
| | - Wei-Li Di
- Infection, Immunity and Inflammation Programme/Immunobiology Section, UCL Great Ormond Street Institute of Child Health, London, United Kingdom.
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Cook J, de Wolf E, Dale N. Cx26 keratitis ichthyosis deafness syndrome mutations trigger alternative splicing of Cx26 to prevent expression and cause toxicity in vitro. ROYAL SOCIETY OPEN SCIENCE 2019; 6:191128. [PMID: 31598268 PMCID: PMC6731697 DOI: 10.1098/rsos.191128] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 07/08/2019] [Indexed: 06/10/2023]
Abstract
The Cx26 mRNA has not been reported to undergo alternative splicing. In expressing a series of human keratitis ichthyosis deafness (KID) syndrome mutations of Cx26 (A88V, N14K and A40V), we found the production of a truncated mRNA product. These mutations, although not creating a cryptic splice site, appeared to activate a pre-existing cryptic splice site. The alternative splicing of the mutant Cx26 mRNA could be prevented by mutating the predicted 3', 5' splice sites and the branch point. The presence of a C-terminal fluorescent protein tag (mCherry or Clover) was necessary for this alternative splicing to occur. Strangely, Cx26A88V could cause the alternative splicing of co-expressed WT Cx26-suggesting a trans effect. The alternative splicing of Cx26A88V caused cell death, and this could be prevented by the 3', 5' and branch point mutations. Expression of the KID syndrome mutants could be rescued by combining them with removal of the 5' splice site. We used this strategy to enable expression of Cx26A40V-5' and demonstrate that this KID syndrome mutation removed CO2 sensitivity from the Cx26 hemichannel. This is the fourth KID syndrome mutation found to abolish the CO2-sensitivity of the Cx26 hemichannel, and suggests that the altered CO-2-sensitivity could contribute to the pathology of this mutation. Future research on KID syndrome mutations should take care to avoid using a C-terminal tag to track cellular localization and expression or if this is unavoidable, combine this mutation with removal of the 5' splice site.
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12
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Hamadah I, Haider M, Chisti M. A novel homozygous mutation of GJB2-A new variant of keratitis-ichthyosis-deafness syndrome? JAAD Case Rep 2019; 5:283-287. [PMID: 30891482 PMCID: PMC6403109 DOI: 10.1016/j.jdcr.2019.01.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Affiliation(s)
- Issam Hamadah
- Dermatology Department, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Mansoor Haider
- Dermatology Department, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Muzamil Chisti
- Dermatology Department, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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Lilly E, Bunick CG, Maley AM, Zhang S, Spraker MK, Theos AJ, Vivar KL, Seminario-Vidal L, Bennett AE, Sidbury R, Ogawa Y, Akiyama M, Binder B, Hadj-Rabia S, Morotti RA, Glusac EJ, Choate KA, Richard G, Milstone LM. More than keratitis, ichthyosis, and deafness: Multisystem effects of lethal GJB2 mutations. J Am Acad Dermatol 2018; 80:617-625. [PMID: 30287322 DOI: 10.1016/j.jaad.2018.09.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 09/06/2018] [Accepted: 09/24/2018] [Indexed: 10/28/2022]
Abstract
BACKGROUND Infant death in keratitis-ichthyosis-deafness (KID) syndrome is recognized; its association with specific genotypes and pathophysiology is inadequately understood. OBJECTIVE We sought to discover characteristics that account for poor outcomes in lethal KID syndrome. METHODS We collected 4 new cases and 9 previously reported, genotyped cases of lethal KID syndrome. We performed new molecular modeling of the lethal mutants GJB2 p.A88V and GJB2 p.G45E. RESULTS Infant death occurred in all patients with GJB2 p.G45E and p.A88V; it is unusual with other GJB2 mutations. Early death with those 2 "lethal" mutations is likely multifactorial: during life all had ≥1 serious infection; most had poor weight gain and severe respiratory difficulties; many had additional anatomic abnormalities. Structural modeling of GJB2 p.G45E identified no impact on the salt bridge previously predicted to account for abnormal central carbon dioxide sensing of GJB2 p.A88V. LIMITATIONS This clinical review was retrospective. CONCLUSION GJB2 p.G45E and p.A88V are the only KID syndrome mutations associated with uniform early lethality. Those electrophysiologically severe mutations in GJB2 reveal abnormalities in many organs in lethal KID syndrome. All patients with KID syndrome may have subtle abnormalities beyond the eyes, ears, and skin. Early genotyping of KID syndrome births will inform prognostic discussion.
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Affiliation(s)
- Evelyn Lilly
- Department of Dermatology at Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
| | | | - Alexander M Maley
- Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia
| | - Shali Zhang
- Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia
| | - Mary K Spraker
- Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia
| | - Amy J Theos
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Karina L Vivar
- Department of Dermatology and Cutaneous Surgery, University of South Florida, Tampa, Florida
| | - Lucia Seminario-Vidal
- Department of Dermatology and Cutaneous Surgery, University of South Florida, Tampa, Florida
| | - Adam E Bennett
- Department of Dermatology and Cutaneous Surgery, University of South Florida, Tampa, Florida
| | - Robert Sidbury
- Division of Dermatology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington
| | - Yasushi Ogawa
- Department of Dermatology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Masashi Akiyama
- Department of Dermatology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Barbara Binder
- Department of Dermatology, Medical University of Graz, Graz, Austria
| | - Smail Hadj-Rabia
- Department of Dermatology, Reference Center for Genodermatoses and Rare Skin Diseases, INSERM U1163, Paris Descartes - Sorbonne Paris Cité University, Imagine Institute, Necker-Enfants Malades Universitary Hospital, Paris, France
| | | | - Earl J Glusac
- Department of Dermatology, Yale School of Medicine, New Haven, Connecticut; Department of Pathology, Yale School of Medicine, New Haven, Connecticut
| | - Keith A Choate
- Department of Dermatology, Yale School of Medicine, New Haven, Connecticut; Department of Pathology, Yale School of Medicine, New Haven, Connecticut
| | | | - Leonard M Milstone
- Department of Dermatology, Yale School of Medicine, New Haven, Connecticut
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14
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García IE, Villanelo F, Contreras GF, Pupo A, Pinto BI, Contreras JE, Pérez-Acle T, Alvarez O, Latorre R, Martínez AD, González C. The syndromic deafness mutation G12R impairs fast and slow gating in Cx26 hemichannels. J Gen Physiol 2018; 150:697-711. [PMID: 29643172 PMCID: PMC5940247 DOI: 10.1085/jgp.201711782] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 11/13/2017] [Accepted: 03/21/2018] [Indexed: 12/27/2022] Open
Abstract
Mutations in connexin 26 hemichannels that cause syndromic deafness have a gain-of-function phenotype that is poorly understood. García et al. show that one such mutation impairs fast and slow gating in these hemichannels because of an interaction between the N terminus and intracellular loop. Mutations in connexin 26 (Cx26) hemichannels can lead to syndromic deafness that affects the cochlea and skin. These mutations lead to gain-of-function hemichannel phenotypes by unknown molecular mechanisms. In this study, we investigate the biophysical properties of the syndromic mutant Cx26G12R (G12R). Unlike wild-type Cx26, G12R macroscopic hemichannel currents do not saturate upon depolarization, and deactivation is faster during hyperpolarization, suggesting that these channels have impaired fast and slow gating. Single G12R hemichannels show a large increase in open probability, and transitions to the subconductance state are rare and short-lived, demonstrating an inoperative fast gating mechanism. Molecular dynamics simulations indicate that G12R causes a displacement of the N terminus toward the cytoplasm, favoring an interaction between R12 in the N terminus and R99 in the intracellular loop. Disruption of this interaction recovers the fast and slow voltage-dependent gating mechanisms. These results suggest that the mechanisms of fast and slow gating in connexin hemichannels are coupled and provide a molecular mechanism for the gain-of-function phenotype displayed by the syndromic G12R mutation.
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Affiliation(s)
- Isaac E García
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.,Laboratory of Molecular Physiology and Biophysics, Facultad de Odontología, Universidad de Valparaíso, Valparaíso, Chile
| | - Felipe Villanelo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.,Computational Biology Laboratory, Fundación Ciencia & Vida, Santiago, Chile
| | - Gustavo F Contreras
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Bernardo I Pinto
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Jorge E Contreras
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ
| | - Tomás Pérez-Acle
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.,Computational Biology Laboratory, Fundación Ciencia & Vida, Santiago, Chile
| | - Osvaldo Alvarez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.,Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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15
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Chen K, Zhan Y, Wu X, Zong L, Jiang H. Germinal mosaicism of PAX3 mutation caused Waardenburg syndrome type I. Int J Pediatr Otorhinolaryngol 2018; 104:200-204. [PMID: 29287868 DOI: 10.1016/j.ijporl.2017.11.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 11/10/2017] [Accepted: 11/14/2017] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Waardenburg syndrome mutations are most often recurrent or de novo. The rate of familial recurrence is low and families with several affected children are extremely rare. In this study, we aimed to clarify the underlying hereditary cause of Waardenburg syndrome type I in two siblings in a Chinese family, with a mother affected by prelingual mild hearing loss and a father who was negative for clinical symptoms of Waardenburg syndrome and had a normal hearing threshold. METHODS Complete characteristic features of the family members were recorded and genetic sequencing and parent-child relationship analyses were performed. RESULTS The two probands were found to share double mutations in the PAX3/GJB2 genes that caused concurrent hearing loss in Waardenburg syndrome type I. Their mother carried the GJB2 c.109G > A homozygous mutation; however, neither the novel PAX3 c.592delG mutation, nor the Waardenburg syndrome phenotype, was observed in either parent. CONCLUSION These previously unreported digenic mutations in PAX3/GJB2 resulted in deafness associated with Waardenburg syndrome type I in this family. To our knowledge, this is the first report describing germinal mosaicism in Waardenburg syndrome. This concept is important because it complicates genetic counseling of this family regarding the risk of recurrence of the mutations in subsequent pregnancies.
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Affiliation(s)
- Kaitian Chen
- Department of Otorhinolaryngology, The First Affiliated Hospital, Sun Yat-Sen University and Institute of Otorhinolaryngology, Sun Yat-sen University, Guangzhou 510080, PR China
| | - Yuan Zhan
- Department of Otorhinolaryngology, The First Affiliated Hospital, Sun Yat-Sen University and Institute of Otorhinolaryngology, Sun Yat-sen University, Guangzhou 510080, PR China
| | - Xuan Wu
- Department of Otorhinolaryngology, The First Affiliated Hospital, Sun Yat-Sen University and Institute of Otorhinolaryngology, Sun Yat-sen University, Guangzhou 510080, PR China
| | - Ling Zong
- Department of Otorhinolaryngology, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China
| | - Hongyan Jiang
- Department of Otorhinolaryngology, Hainan General Hospital, Haikou 570311, China.
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16
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de Wolf E, van de Wiel J, Cook J, Dale N. Altered CO2 sensitivity of connexin26 mutant hemichannels in vitro. Physiol Rep 2017; 4:4/22/e13038. [PMID: 27884957 PMCID: PMC5357999 DOI: 10.14814/phy2.13038] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 10/19/2016] [Accepted: 10/21/2016] [Indexed: 12/17/2022] Open
Abstract
Connexin26 (Cx26) mutations underlie human pathologies ranging from hearing loss to keratitis ichthyosis deafness (KID) syndrome. Cx26 hemichannels are directly gated by CO2 and contribute to the chemosensory regulation of breathing. The KID syndrome mutation A88V is insensitive to CO2, and has a dominant negative action on the CO2 sensitivity of Cx26WT hemichannels, and reduces respiratory drive in humans. We have now examined the effect of further human mutations of Cx26 on its sensitivity to CO2 : Mutated Cx26 subunits, carrying one of A88S, N14K, N14Y, M34T, or V84L, were transiently expressed in HeLa cells. The CO2-dependence of hemichannel activity, and their ability to exert dominant negative actions on cells stably expressing Cx26WT, was quantified by a dye-loading assay. The KID syndrome mutation, N14K, abolished the sensitivity of Cx26 to CO2 Both N14Y and N14K exerted a powerful dominant negative action on the CO2 sensitivity of Cx26WT None of the other mutations (all recessive) had a dominant negative action. A88S shifted the affinity of Cx26 to slightly higher levels without reducing its ability to fully open to CO2 M34T did not change the affinity of Cx26 for CO2 but reduced its ability to open in response to CO2 V84L had no effect on the CO2-sensitivity of Cx26. Some pathological mutations of Cx26 can therefore alter the CO2 sensitivity of Cx26 hemichannels. The loss of CO2 sensitivity could contribute to pathology and consequent reduced respiratory drive could be an unrecognized comorbidity of these pathologies.
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Affiliation(s)
- Elizabeth de Wolf
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Joseph van de Wiel
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Jonathan Cook
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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17
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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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18
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Press ER, Shao Q, Kelly JJ, Chin K, Alaga A, Laird DW. Induction of cell death and gain-of-function properties of connexin26 mutants predict severity of skin disorders and hearing loss. J Biol Chem 2017; 292:9721-9732. [PMID: 28428247 DOI: 10.1074/jbc.m116.770917] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 04/20/2017] [Indexed: 11/06/2022] Open
Abstract
Connexin26 (Cx26) is a gap junction protein that oligomerizes in the cell to form hexameric transmembrane channels called connexons. Cell surface connexons dock between adjacent cells to allow for gap junctional intercellular communication. Numerous autosomal dominant mutations in the Cx26-encoding GJB2 gene lead to many skin disorders and sensorineural hearing loss. Although some insights have been gained into the pathogenesis of these diseases, it is not fully understood how distinct GJB2 mutations result in hearing loss alone or in skin pathologies with comorbid hearing loss. Here we investigated five autosomal dominant Cx26 mutants (N14K, D50N, N54K, M163V, and S183F) linked to various syndromic or nonsyndromic diseases to uncover the molecular mechanisms underpinning these disease links. We demonstrated that when gap junction-deficient HeLa cells expressed the N14K and D50N mutants, they undergo cell death. The N54K mutant was retained primarily within intracellular compartments and displayed dominant or transdominant properties on wild-type Cx26 and coexpressed Cx30 and Cx43. The S183F mutant formed some gap junction plaques but was largely retained within the cell and exhibited only a mild transdominant reduction in gap junction communication when co-expressed with Cx30. The M163V mutant, which causes only hearing loss, exhibited impaired gap junction function and showed no transdominant interactions. These findings suggest that Cx26 mutants that promote cell death or exert transdominant effects on other connexins in keratinocytes will lead to skin diseases and hearing loss, whereas mutants having reduced channel function but exhibiting no aberrant effects on coexpressed connexins cause only hearing loss. Moreover, cell death-inducing GJB2 mutations lead to more severe syndromic disease.
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Affiliation(s)
- Eric R Press
- Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Qing Shao
- From the Departments of Anatomy and Cell Biology and
| | - John J Kelly
- From the Departments of Anatomy and Cell Biology and
| | - Katrina Chin
- From the Departments of Anatomy and Cell Biology and
| | - Anton Alaga
- From the Departments of Anatomy and Cell Biology and
| | - Dale W Laird
- Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada .,From the Departments of Anatomy and Cell Biology and
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19
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Al Malki A, Marguery MC, Giordano-Labadie F, Konstantinou MP, Mokeddem L, Lamant L, Paul C, Maza A, Mazereeuw-Hautier J. Systemic allergic contact dermatitis caused by methyl aminolaevulinate in a patient with keratosis-ichthyosis-deafness syndrome. Contact Dermatitis 2017; 76:190-192. [DOI: 10.1111/cod.12703] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 09/05/2016] [Accepted: 09/06/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Aysha Al Malki
- Department of Dermatology; Paul Sabatier University and Toulouse University Hospital; 31400 Toulouse France
| | - Marie-Claude Marguery
- Department of Dermatology; Paul Sabatier University and Toulouse University Hospital; 31400 Toulouse France
| | - Françoise Giordano-Labadie
- Department of Dermatology; Paul Sabatier University and Toulouse University Hospital; 31400 Toulouse France
| | - Maria P. Konstantinou
- Department of Dermatology; Paul Sabatier University and Toulouse University Hospital; 31400 Toulouse France
| | - Lorraine Mokeddem
- Department of Dermatology; Paul Sabatier University and Toulouse University Hospital; 31400 Toulouse France
| | - Laurence Lamant
- Department of Anatomy and Cytopathlogy; Institut Universitaire du Cancer - IUCT Toulouse; 31059 Tolouse France
| | - Carle Paul
- Department of Dermatology; Paul Sabatier University and Toulouse University Hospital; 31400 Toulouse France
| | - Aude Maza
- Department of Dermatology; Paul Sabatier University and Toulouse University Hospital; 31400 Toulouse France
| | - Juliette Mazereeuw-Hautier
- Department of Dermatology; Paul Sabatier University and Toulouse University Hospital; 31400 Toulouse France
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20
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Bhanu Prasad V, Mallick S, Upadhyay AD, Rath GK. Systematic review and individual patient data analysis of pediatric head and neck squamous cell carcinoma: An analysis of 217 cases. Int J Pediatr Otorhinolaryngol 2017; 92:75-81. [PMID: 28012539 DOI: 10.1016/j.ijporl.2016.11.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Revised: 11/04/2016] [Accepted: 11/07/2016] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Pediatric head and neck Squamous cell carcinoma (PHNSCC) is a rare disease. The optimum treatment and outcome remains poorly understood because of rarity. METHODS We conducted an individual patient data analysis of PHNSCC. Two authors independently searched PubMed, google search, and Cochrane library for eligible studies using following search words: Pediatric Head and neck squamous cell carcinoma, Head and neck squamous cell carcinoma under age of 20, Head and neck squamous cell carcinoma in young, PHNSCC till June 1, 2016 published in English language. RESULTS Total of 217 patients of PHNSCC were found in the literature. Median age among the cohort was 15 years (Range: 0-20 years) with a clear male preponderance. Oral cavity tumors were commonest 75 (70%) followed by laryngeal neoplasms 16(15%). Median disease free survival was 9 months (Range: 0-216 months). Median overall survival was 48 months (Range: 1-216 months). In univariate analysis treatment modality had significant impact on disease free survival (DFS). Whereas, patients treated with Surgery, Laryngeal primary had significantly better OS. Patients with associated fanconis anemia had significantly worse overall survival (OS). CONCLUSION PHNSCC is a rare disease with poorer outcome. Associated DNA defects leads to poorer OS. Patients treated with surgery alone or surgery followed by adjuvant radiation had better DFS and OS. Molecular profiling and personalized therapy may improve survival with limited toxicity.
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Affiliation(s)
- V Bhanu Prasad
- Department of Radiation Oncology, All India Institute of Medical Sciences, New Delhi, India.
| | - Supriya Mallick
- Department of Radiation Oncology, All India Institute of Medical Sciences, New Delhi, India.
| | - Ashish Dutt Upadhyay
- Department of Bio-Statistics, All India Institute of Medical Sciences, New Delhi, India.
| | - G K Rath
- Department of Radiation Oncology, All India Institute of Medical Sciences, New Delhi, India.
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21
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Saral S, Vural A, Wollenberg A, Ruzicka T. A practical approach to ichthyoses with systemic manifestations. Clin Genet 2016; 91:799-812. [DOI: 10.1111/cge.12828] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/06/2016] [Accepted: 06/22/2016] [Indexed: 12/20/2022]
Affiliation(s)
- S. Saral
- Department of Dermatology and Venereology; Ankara University; Ankara Turkey
- Department of Dermatology and Allergology; Ludwig-Maximilian University; Munich Germany
| | - A. Vural
- Department of Neurology; Hacettepe University; Ankara Turkey
| | - A. Wollenberg
- Department of Dermatology and Allergology; Ludwig-Maximilian University; Munich Germany
| | - T. Ruzicka
- Department of Dermatology and Allergology; Ludwig-Maximilian University; Munich Germany
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22
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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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23
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Connexin26 Mutations Causing Palmoplantar Keratoderma and Deafness Interact with Connexin43, Modifying Gap Junction and Hemichannel Properties. J Invest Dermatol 2016; 136:225-235. [PMID: 26763442 PMCID: PMC4731051 DOI: 10.1038/jid.2015.389] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 09/03/2015] [Accepted: 09/21/2015] [Indexed: 12/23/2022]
Abstract
Mutations in GJB2 (Cx26) cause either deafness, or deafness associated with skin diseases. That different disorders can be caused by distinct mutations within the same gene suggests that unique channel activities are influenced by each class of mutation. We have examined the functional characteristics of two human mutations, Cx26-H73R and Cx26-S183F, causing palmoplantar keratoderma (PPK) and deafness. Both failed to form gap junction channels or hemichannels when expressed alone. Co-expression of the mutants with wild-type Cx43 showed a trans-dominant inhibition of Cx43 gap junction channels, without reductions in Cx43 protein synthesis. In addition, the presence of mutant Cx26 shifted Cx43 channel gating and kinetics towards a more Cx26-like behavior. Co-immunoprecipitation showed Cx43 being pulled down more efficiently with mutant Cx26, than wild-type, confirming the enhanced formation of heteromeric connexons. Finally, the formation of heteromeric connexons resulted in significantly increased Cx43 hemichannel activity in the presence of Cx26 mutants. These findings suggest a common mechanism whereby Cx26 mutations causing PPK and deafness trans-dominantly influence multiple functions of wild-type Cx43. They also implicate a role for aberrant hemichannel activity in the pathogenesis of PPK, and further highlight an emerging role for Cx43 in genetic skin diseases.
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24
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Markova TG, Brazhkina NB, Bliznech EA, Bakhshinyan VV, Polyakov AV, Tavartkiladze GA. Phenotype in a patient with p.D50N mutation in GJB2 gene resemble both KID and Clouston syndromes. Int J Pediatr Otorhinolaryngol 2016; 81:10-4. [PMID: 26810281 DOI: 10.1016/j.ijporl.2015.11.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 11/13/2015] [Accepted: 11/18/2015] [Indexed: 11/18/2022]
Abstract
Keratitis-ichthyosis-deafness (KID) syndrome (OMIM 148210) is a rare ectodermal dysplasia syndrome characterized by vascularizing keratitis, congenital profound sensorineural hearing loss, and progressive erythrokeratoderma. We have found a 148G-A transition in the GJB2 gene, resulting in an asp50-to-asn (D50N) substitution in a girl with congenital deafness. This finding allowed us to diagnose а KID syndrome. But clinical features were uncommon because of a mild skin manifestation, lack of keratitis and unusual appearance resembling Clouston syndrome. Molecular genetic tests showed that it was de novo mutation because parents have normal genotype. Several autosomal dominant mutations in the GJB2 gene (сonnexin 26) now established to underlie many of the affected cases, with the majority of patients harboring the p.D50N mutation. Skin disease-associated mutation of connexin proteins can cause functional disturbances in gap junction intercellular conductance. It is likely that multiple disease mechanisms are involved across the wide spectrum of hereditary diseases relating to connexin proteins. The clinical data may provide additional insights into the dysregulation mechanisms of mutations result in the disease.
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Affiliation(s)
- T G Markova
- Department the Epidemiology and Genetics of Hearing Loss, National Research Center for Audiology and Hearing Rehabilitation, 123 Leninsky Ave, 117513 Moscow, Russia.
| | - N B Brazhkina
- Out-Patient Clinic, National Research Center for Audiology and Hearing Rehabilitation, 123 Leninsky Ave, 117513 Moscow, Russia
| | - E A Bliznech
- Laboratory for DNA-Diagnostics, Federal State Budgetary Institution "Research Centre for Medical Genetics", 1, Room 116 Moskvorechie Str, 115478 Moscow, Russia.
| | - V V Bakhshinyan
- Cochlear Implants Center, National Research Center for Audiology and Hearing Rehabilitation, 123 Leninsky Ave, 117513 Moscow, Russia.
| | - A V Polyakov
- Laboratory for DNA-Diagnostics, Federal State Budgetary Institution "Research Centre for Medical Genetics", 1, Room 116 Moskvorechie Str, 115478 Moscow, Russia.
| | - G A Tavartkiladze
- National Research Center for Audiology and Hearing Rehabilitation, 123 Leninsky Ave, 117513 Moscow, Russia.
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25
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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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26
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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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Abstract
Genetic skin diseases, or genodermatoses, often have extracutaneous manifestations. Ocular manifestations in particular can have significant clinical implications, like blindness. Other manifestations, such as the corneal opacities that occur in X-linked ichthyosis, are asymptomatic but characteristic of a particular genodermatosis. Ophthalmologic examination can aid in diagnosis when characteristic findings are seen. The genodermatoses with ocular manifestations will be reviewed, but neurocutaneous, syndromes, genetic pigmentary disorders, and genetic metabolic diseases are not included because they are covered elsewhere in this issue.
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Affiliation(s)
- Melinda Jen
- Section of Pediatric Dermatology, Children's Hospital of Philadelphia; Departments of Pediatrics and Dermatology, Perelman School of Medicine at the University of Pennsylvania, 3550 Market St, Second floor, Philadelphia, PA, 19104.
| | - Sudha Nallasamy
- The Vision Center, Children's Hospital Los Angeles; Department of Ophthalmology, Keck School of Medicine, University of Southern California, 4650 Sunset Blvd, MS #88, Los Angeles, CA, 90027
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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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Lebeko K, Bosch J, Noubiap JJN, Dandara C, Wonkam A. Genetics of hearing loss in Africans: use of next generation sequencing is the best way forward. Pan Afr Med J 2015; 20:383. [PMID: 26185573 PMCID: PMC4499266 DOI: 10.11604/pamj.2015.20.383.5230] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 09/27/2014] [Indexed: 11/11/2022] Open
Abstract
Hearing loss is the most common communication disorder affecting about 1-7/1000 births worldwide. The most affected areas are developing countries due toextensively poor health care systems. Environmental causes contribute to 50-70% of cases, specifically meningitis in sub-Saharan Africa. The other 30-50% is attributed to genetic factors. Nonsyndromic hearing loss is the most common form of hearing loss accounting for up to 70% of cases. The most common mode of inheritance is autosomal recessive. The most prevalent mutations associated with autosomal recessive nonsyndromic hearing loss (ARNSHL) are found within connexin genes such as GJB2, mostly in people of European and Asian origin. For example, the c.35delG mutation ofGJB2 is found in 70% of ARNSHL patients of European descentand is rare in populations of otherethnicities. Other GJB2 mutations have been reported in various populations. The second most common mutations are found in theconnexin gene, GJB6, also with a high prevalencein patients of European descent. To date more than 60 genes have been associated with ARNSHL. We previously showed that mutations in GJB2, GJB6 and GJA1 are not significant causes of ARNSHL inpatients from African descents, i.e. Cameroonians and South AfricansIn order to resolve ARNSHL amongst sub-Saharan African patients, additional genes would need to be explored. Currently at least 60 genes are thought to play a role in ARNSHL thus the current approach using Sanger sequencing would not be appropriate as it would be expensive and time consuming. Next Generation sequencing (NGS) provides the best alternative approach. In this review, we reported on the success of using NGSas observed in various populations and advocate for the use of NGS to resolve cases of ARNSHL in sub-Saharan African populations.
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Affiliation(s)
- Kamogelo Lebeko
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Jason Bosch
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | | | - Collet Dandara
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa ; Institute for Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Homeida L, Wiley RT, Fatahzadeh M. Oral squamous cell carcinoma in a patient with keratitis-ichthyosis-deafness syndrome: a rare case. Oral Surg Oral Med Oral Pathol Oral Radiol 2015; 119:e226-32. [PMID: 25758847 DOI: 10.1016/j.oooo.2015.01.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 12/22/2014] [Accepted: 01/01/2015] [Indexed: 10/24/2022]
Abstract
Keratitis-ichthyosis-deafness (KID) syndrome is a rare form of ectodermal dysplasia with significant visual and auditory impairment. Pathogenesis involves a mutation in the GJB2 gene, which encodes connexin-26, a protein in the epithelial gap junctions thought to be involved in the differentiation of ectodermally derived tissues. Affected patients are also at increased risk for the epithelial malignancies. To our knowledge, nearly 100 cases of KID syndrome, including 19 with squamous cell carcinoma (SCC) complications, have been reported worldwide. We report here a patient with KID syndrome who developed an ulcerative oral lesion causing him significant discomfort; he was subsequently diagnosed with oral SCC. We review the clinical presentation and symptomatology, including those affecting the oral cavity for this syndrome and highlight the importance of multidisciplinary collaboration and life-long screening aimed at prevention of the evolving complications.
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Affiliation(s)
- L Homeida
- Candidate, Master of Dental Science, Rutgers School of Dental Medicine, Newark, New Jersey, USA
| | - R T Wiley
- Chief Resident, Oral Pathology, New York Hospital in Queens, New York, New York, USA
| | - M Fatahzadeh
- Department of Diagnostic Sciences, Rutgers School of Dental Medicine, Newark, New Jersey, USA.
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Keratitis-ichthyosis-deafness syndrome-associated Cx26 mutants produce nonfunctional gap junctions but hyperactive hemichannels when co-expressed with wild type Cx43. J Invest Dermatol 2015; 135:1338-1347. [PMID: 25625422 PMCID: PMC4801018 DOI: 10.1038/jid.2015.20] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 01/13/2015] [Accepted: 01/14/2015] [Indexed: 11/09/2022]
Abstract
Mutations in Cx26 gene are found in most cases of human genetic deafness. Some mutations produce syndromic deafness associated with skin disorders, like the Keratitis-Ichthyosis-Deafness syndrome (KID). Because in the human skin connexin 26 (Cx26) is co-expressed with other connexins, like Cx43 and Cx30, and as the KID syndrome is inherited as autosomal dominant condition, it is possible that KID mutations change the way Cx26 interacts with other co-expressed connexins. Indeed, some Cx26 syndromic mutations showed gap junction dominant negative effect when co-expressed with wild-type connexins, including Cx26 and Cx43. The nature of these interactions and the consequences on hemichannels and gap junction channel (GJC) functions remain unknown. In this study, we demonstrate that syndromic mutations, at the N terminus segment of Cx26, change connexin oligomerization compatibility, allowing aberrant interactions with Cx43. Strikingly, heteromeric oligomer formed by Cx43/Cx26 (syndromic mutants) shows exacerbated hemichannel activity but nonfunctional GJCs; this also occurs for those Cx26 KID mutants that do not show functional homomeric hemichannels. Heterologous expression of these hyperactive heteromeric hemichannels increases cell membrane permeability, favoring ATP release and Ca(2+) overload. The functional paradox produced by oligomerization of Cx43 and Cx26 KID mutants could underlie the severe syndromic phenotype in human skin.
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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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Phenotypic variability in gap junction syndromic skin disorders: experience from KID and Clouston syndromes' clinical diagnostics. J Appl Genet 2015; 56:329-37. [PMID: 25575739 PMCID: PMC4543413 DOI: 10.1007/s13353-014-0266-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 12/05/2014] [Accepted: 12/17/2014] [Indexed: 01/14/2023]
Abstract
Connexins belong to the family of gap junction proteins which enable direct cell-to-cell communication by forming channels in adjacent cells. Mutations in connexin genes cause a variety of human diseases and, in a few cases, result in skin disorders. There are significant differences in the clinical picture of two rare autosomal dominant syndromes: keratitis–ichthyosis–deafness (KID) syndrome and hidrotic ectodermal dysplasia (Clouston syndrome), which are caused by GJB2 and GJB6 mutations, respectively. This is despite the fact that, in both cases, malfunctioning of the same family proteins and some overlapping clinical features (nail dystrophy, hair loss, and palmoplantar keratoderma) is observed. KID syndrome is characterized by progressive vascularizing keratitis, ichthyosiform erythrokeratoderma, and neurosensory hearing loss, whereas Clouston syndrome is characterized by nail dystrophy, hypotrichosis, and palmoplantar keratoderma. The present paper presents a Polish patient with sporadic KID syndrome caused by the mutation of p.Asp50Asn in GJB2. The patient encountered difficulties in obtaining a correct diagnosis. The other case presented is that of a family with Clouston syndrome (caused by p.Gly11Arg mutation in GJB6), who are the first reported patients of Polish origin suffering from this disorder. Phenotype diversity among patients with the same genotypes reported to date is also summarized. The conclusion is that proper diagnosis of these syndromes is still challenging and should always be followed by molecular verification.
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Abstract
Facial involvement represents a characteristic feature of a wide range of genodermatoses. Specific facial findings often help point to the correct diagnosis, which improves counseling and management. In particular, this can facilitate the identification and treatment of associated extracutaneous disease. The highly visible nature of facial lesions in genodermatoses and facial birthmarks can result in stigmatization and frequently leads to particular concern in patients and their family members. It is therefore critical for dermatologists to be aware of the broad spectrum of facial manifestations in genetic skin disease, especially when these findings have important implications with regard to monitoring and treatment. In this contribution, facial involvement in genodermatoses is divided into five morphologic categories based on the most prominent feature: Papules, scaling, photosensitivity/findings associated with aging (eg, telangiectasias, atrophy, lentigines), blisters/erosions, and birthmarks. Hopefully, this will provide a practical and clinically useful approach to a large and diverse assortment of genetic skin conditions.
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35
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Levit NA, Sellitto C, Wang HZ, Li L, Srinivas M, Brink PR, White TW. Aberrant connexin26 hemichannels underlying keratitis-ichthyosis-deafness syndrome are potently inhibited by mefloquine. J Invest Dermatol 2014; 135:1033-1042. [PMID: 25229253 PMCID: PMC4363291 DOI: 10.1038/jid.2014.408] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 08/02/2014] [Accepted: 09/04/2014] [Indexed: 11/27/2022]
Abstract
Keratitis-ichthyosis-deafness (KID) syndrome is an ectodermal dysplasia caused by dominant mutations of connexin26 (Cx26). Loss of Cx26 function causes non-syndromic sensorineural deafness, without consequence in the epidermis. Functional analyses have revealed that a majority of KID-causing mutations confer a novel expansion of hemichannel activity, mediated by connexin channels in a non-junctional configuration. Inappropriate Cx26 hemichannel opening is hypothesized to compromise keratinocyte integrity and epidermal homeostasis. Pharmacological modulators of Cx26 are needed to assess the pathomechanistic involvement of hemichannels in the development of hyperkeratosis in KID syndrome. We have used electrophysiological assays to evaluate small molecule analogs of quinine for suppressive effects on aberrant hemichannel currents elicited by KID mutations. Here, we show that mefloquine inhibits several mutant hemichannel forms implicated in KID syndrome when expressed in Xenopus laevis oocytes (IC50≈16µM), using an extracellular divalent cation, zinc (Zn++), as a non-specific positive control for comparison (IC50≈3µM). Furthermore, we used freshly isolated transgenic keratinocytes to show that micromolar concentrations of mefloquine attenuated increased macroscopic membrane currents in primary mouse keratinocytes expressing human Cx26-G45E, a mutation causing a lethal form of KID syndrome.
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Affiliation(s)
- Noah A Levit
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Caterina Sellitto
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Hong-Zhan Wang
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Leping Li
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Miduturu Srinivas
- Department of Biological and Vision Sciences, SUNY College of Optometry, New York, USA
| | - Peter R Brink
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA.
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36
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Bosch J, Noubiap JJN, Dandara C, Makubalo N, Wright G, Entfellner JBD, Tiffin N, Wonkam A. Sequencing of GJB2 in Cameroonians and Black South Africans and comparison to 1000 Genomes Project Data Support Need to Revise Strategy for Discovery of Nonsyndromic Deafness Genes in Africans. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2014; 18:705-10. [PMID: 25162826 DOI: 10.1089/omi.2014.0063] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations in the GJB2 gene, encoding connexin 26, could account for 50% of congenital, nonsyndromic, recessive deafness cases in some Caucasian/Asian populations. There is a scarcity of published data in sub-Saharan Africans. We Sanger sequenced the coding region of the GJB2 gene in 205 Cameroonian and Xhosa South Africans with congenital, nonsyndromic deafness; and performed bioinformatic analysis of variations in the GJB2 gene, incorporating data from the 1000 Genomes Project. Amongst Cameroonian patients, 26.1% were familial. The majority of patients (70%) suffered from sensorineural hearing loss. Ten GJB2 genetic variants were detected by sequencing. A previously reported pathogenic mutation, g.3741_3743delTTC (p.F142del), and a putative pathogenic mutation, g.3816G>A (p.V167M), were identified in single heterozygous samples. Amongst eight the remaining variants, two novel variants, g.3318-41G>A and g.3332G>A, were reported. There were no statistically significant differences in allele frequencies between cases and controls. Principal Components Analyses differentiated between Africans, Asians, and Europeans, but only explained 40% of the variation. The present study is the first to compare African GJB2 sequences with the data from the 1000 Genomes Project and have revealed the low variation between population groups. This finding has emphasized the hypothesis that the prevalence of mutations in GJB2 in nonsyndromic deafness amongst European and Asian populations is due to founder effects arising after these individuals migrated out of Africa, and not to a putative "protective" variant in the genomic structure of GJB2 in Africans. Our results confirm that mutations in GJB2 are not associated with nonsyndromic deafness in Africans.
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Affiliation(s)
- Jason Bosch
- 1 Division of Human Genetics, Faculty of Health Sciences, University of Cape Town , Cape Town, South Africa
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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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Sanchez HA, Villone K, Srinivas M, Verselis VK. The D50N mutation and syndromic deafness: altered Cx26 hemichannel properties caused by effects on the pore and intersubunit interactions. ACTA ACUST UNITED AC 2014; 142:3-22. [PMID: 23797419 PMCID: PMC3691445 DOI: 10.1085/jgp.201310962] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutations in the GJB2 gene, which encodes Cx26, are the most common cause of sensorineural deafness. In syndromic cases, such as keratitis-ichthyosis-deafness (KID) syndrome, in which deafness is accompanied by corneal inflammation and hyperkeratotic skin, aberrant hemichannel function has emerged as the leading contributing factor. We found that D50N, the most frequent mutation associated with KID syndrome, produces multiple aberrant hemichannel properties, including loss of inhibition by extracellular Ca(2+), decreased unitary conductance, increased open hemichannel current rectification and voltage-shifted activation. We demonstrate that D50 is a pore-lining residue and that negative charge at this position strongly influences open hemichannel properties. Examination of two putative intersubunit interactions involving D50 suggested by the Cx26 crystal structure, K61-D50 and Q48-D50, showed no evidence of a K61-D50 interaction in hemichannels. However, our data suggest that Q48 and D50 interact and disruption of this interaction shifts hemichannel activation positive along the voltage axis. Additional shifts in activation by extracellular Ca(2+) remained in the absence of a D50-Q48 interaction but required an Asp or Glu at position 50, suggesting a separate electrostatic mechanism that critically involves this position. In gap junction (GJ) channels, D50 substitutions produced loss of function, whereas K61 substitutions functioned as GJ channels but not as hemichannels. These data demonstrate that D50 exerts effects on Cx26 hemichannel and GJ channel function as a result of its dual role as a pore residue and a component of an intersubunit complex in the extracellular region of the hemichannel. Differences in the effects of substitutions in GJ channels and hemichannels suggest that perturbations in structure occur upon hemichannel docking that significantly impact function. Collectively, these data provide insight into Cx26 structure-function and the underlying bases for the phenotypes associated with KID syndrome patients carrying the D50N mutation.
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Affiliation(s)
- Helmuth A Sanchez
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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39
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de Zwart-Storm EA, Martin PE, van Steensel MAM. Gap junction diseases of the skin: novel insights from new mutations. ACTA ACUST UNITED AC 2014. [DOI: 10.1586/edm.09.47] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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40
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Derelioglu SS, Yılmaz Y, Keles S. Dental Treatments under the General Anesthesia in a Child with Keratitis, Ichthyosis, and Deafness Syndrome. Case Rep Dent 2013; 2013:618468. [PMID: 24151560 PMCID: PMC3789304 DOI: 10.1155/2013/618468] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 08/19/2013] [Indexed: 11/17/2022] Open
Abstract
KID syndrome is a rare genodermatosis characterized by keratitis, ichthyosis, and sensorineural deafness. Although the dermatological, ophthalmologic, and sensorineural defects are emphasized in the literature, oral and dental evaluations are so superficial. In this case report, dental and oral symptoms of a three year and five months old boy with KID syndrome, suffering severe Early Childhood Caries (s-ECC) and dental treatments done under General Anesthesia (GA) were reported.
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Affiliation(s)
- Sera Sımsek Derelioglu
- Department of Pedodontics, Faculty of Dentistry, Atatürk University, 25240 Erzurum, Turkey
| | - Yücel Yılmaz
- Department of Pedodontics, Faculty of Dentistry, Atatürk University, 25240 Erzurum, Turkey
| | - Sultan Keles
- Department of Pedodontics, Faculty of Dentistry, Atatürk University, 25240 Erzurum, Turkey
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41
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Wonkam A, Noubiap JJN, Bosch J, Dandara C, Toure GB. Heterozygous p.Asp50Asn mutation in the GJB2 gene in two Cameroonian patients with keratitis-ichthyosis-deafness (KID) syndrome. BMC MEDICAL GENETICS 2013; 14:81. [PMID: 23924173 PMCID: PMC3750395 DOI: 10.1186/1471-2350-14-81] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 08/07/2013] [Indexed: 11/10/2022]
Abstract
BACKGROUND Keratitis-Ichthyosis-Deafness (KID) syndrome (OMIM 148210) is a congenital ectodermal defect that consists of an atypical ichthyosiform erythroderma associated with congenital sensorineural deafness. KID appears to be genetically heterogeneous and most cases are caused by GJB2 mutations. Mutations in African patients have been rarely described. CASE PRESENTATION We report on two unrelated Cameroonian individuals affected with sporadic KID, presenting with the classic phenotypic triad. The two patients were heterozygous for the most frequent p.Asp50Asn mutation. This first report in patients from sub-Saharan African origin supports the hypothesis that the occurrence of KID due to p.Asp50Asn mutation in GJB2 seems not to be population specific. CONCLUSIONS Our finding has implication in medical genetic practice, specifically in the molecular diagnosis of KID in Africans. These cases also reveal and emphasize the urgent need to develop appropriate policies to care for patients with rare/orphan diseases in Sub-Saharan Africa, as many of these cases become more and more recognizable.
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Affiliation(s)
- Ambroise Wonkam
- Division of Human Genetics, Department of Clinical Laboratory Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
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Smyth CM, Sinnathuray AR, Hughes AE, Toner JG. Cochlear implantation in keratitis–ichthyosis–deafness syndrome – 10-year follow-up of two patients. Cochlear Implants Int 2013; 13:54-9. [PMID: 22340753 DOI: 10.1179/146701011x12950038111936] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Affiliation(s)
- C M Smyth
- Department of Otolaryngology, Belfast City Hospital, UK.
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43
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Barker EJ, Briggs RJS. Cochlear implantation in children with keratitis-ichthyosis-deafness (KID) syndrome: Outcomes in three cases. Cochlear Implants Int 2013; 10:166-73. [DOI: 10.1179/cim.2009.10.3.166] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Coggshall K, Farsani T, Ruben B, McCalmont TH, Berger TG, Fox LP, Shinkai K. Keratitis, ichthyosis, and deafness (KID) syndrome: A review of infectious and neoplastic complications. J Am Acad Dermatol 2013; 69:127-34. [DOI: 10.1016/j.jaad.2012.12.965] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 12/12/2012] [Accepted: 12/16/2012] [Indexed: 01/06/2023]
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EMQN Best Practice guidelines for diagnostic testing of mutations causing non-syndromic hearing impairment at the DFNB1 locus. Eur J Hum Genet 2013; 21:1325-9. [PMID: 23695287 PMCID: PMC3798855 DOI: 10.1038/ejhg.2013.83] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Avshalumova L, Fabrikant J, Koriakos A. Overview of skin diseases linked to connexin gene mutations. Int J Dermatol 2013; 53:192-205. [DOI: 10.1111/ijd.12062] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
| | - Jordan Fabrikant
- Texas Division; Department of Dermatology; Larkin Community Hospital; Miami FL USA
| | - Angie Koriakos
- Department of Dermatology; University of North Texas Health Science Center/Texas College of Osteopathic Medicine; Houston TX USA
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Mhaske PV, Levit NA, Li L, Wang HZ, Lee JR, Shuja Z, Brink PR, White TW. The human Cx26-D50A and Cx26-A88V mutations causing keratitis-ichthyosis-deafness syndrome display increased hemichannel activity. Am J Physiol Cell Physiol 2013; 304:C1150-8. [PMID: 23447037 DOI: 10.1152/ajpcell.00374.2012] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Mutations in the human gene encoding connexin 26 (Cx26 or GJB2) cause either nonsyndromic deafness or syndromic deafness associated with skin diseases. That distinct clinical disorders can be caused by different mutations within the same gene suggests that different channel activities influence the ear and skin. Here we use three different expression systems to examine the functional characteristics of two Cx26 mutations causing either mild (Cx26-D50A) or lethal (Cx26-A88V) keratitis-ichthyosis-deafness (KID) syndrome. In either cRNA-injected Xenopus oocytes, transfected HeLa cells, or transfected primary human keratinocytes, we show that both Cx26-D50A and Cx26-A88V form active hemichannels that significantly increase membrane current flow compared with wild-type Cx26. This increased membrane current accelerated cell death in low extracellular calcium solutions and was not due to increased mutant protein expression. Elevated mutant hemichannel currents could be blocked by increased extracellular calcium concentration. These results show that these two mutations exhibit a shared gain of functional activity and support the hypothesis that increased hemichannel activity is a common feature of human Cx26 mutations responsible for KID syndrome.
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Affiliation(s)
- Pallavi V Mhaske
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA
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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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50
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