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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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Posukh OL, Maslova EA, Danilchenko VY, Zytsar MV, Orishchenko KE. Functional Consequences of Pathogenic Variants of the GJB2 Gene (Cx26) Localized in Different Cx26 Domains. Biomolecules 2023; 13:1521. [PMID: 37892203 PMCID: PMC10604905 DOI: 10.3390/biom13101521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/08/2023] [Accepted: 10/10/2023] [Indexed: 10/29/2023] Open
Abstract
One of the most common forms of genetic deafness has been predominantly associated with pathogenic variants in the GJB2 gene, encoding transmembrane protein connexin 26 (Cx26). The Cx26 molecule consists of an N-terminal domain (NT), four transmembrane domains (TM1-TM4), two extracellular loops (EL1 and EL2), a cytoplasmic loop, and a C-terminus (CT). Pathogenic variants in the GJB2 gene, resulting in amino acid substitutions scattered across the Cx26 domains, lead to a variety of clinical outcomes, including the most common non-syndromic autosomal recessive deafness (DFNB1A), autosomal dominant deafness (DFNA3A), as well as syndromic forms combining hearing loss and skin disorders. However, for rare and poorly documented variants, information on the mode of inheritance is often lacking. Numerous in vitro studies have been conducted to elucidate the functional consequences of pathogenic GJB2 variants leading to amino acid substitutions in different domains of Cx26 protein. In this work, we summarized all available data on a mode of inheritance of pathogenic GJB2 variants leading to amino acid substitutions and reviewed published information on their functional effects, with an emphasis on their localization in certain Cx26 domains.
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Affiliation(s)
- Olga L. Posukh
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Ekaterina A. Maslova
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Valeriia Yu. Danilchenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Marina V. Zytsar
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
| | - Konstantin E. Orishchenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
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Mao L, Wang Y, An L, Zeng B, Wang Y, Frishman D, Liu M, Chen Y, Tang W, Xu H. Molecular Mechanisms and Clinical Phenotypes of GJB2 Missense Variants. BIOLOGY 2023; 12:biology12040505. [PMID: 37106706 PMCID: PMC10135792 DOI: 10.3390/biology12040505] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 01/19/2023] [Accepted: 01/20/2023] [Indexed: 03/29/2023]
Abstract
The GJB2 gene is the most common gene responsible for hearing loss (HL) worldwide, and missense variants are the most abundant type. GJB2 pathogenic missense variants cause nonsyndromic HL (autosomal recessive and dominant) and syndromic HL combined with skin diseases. However, the mechanism by which these different missense variants cause the different phenotypes is unknown. Over 2/3 of the GJB2 missense variants have yet to be functionally studied and are currently classified as variants of uncertain significance (VUS). Based on these functionally determined missense variants, we reviewed the clinical phenotypes and investigated the molecular mechanisms that affected hemichannel and gap junction functions, including connexin biosynthesis, trafficking, oligomerization into connexons, permeability, and interactions between other coexpressed connexins. We predict that all possible GJB2 missense variants will be described in the future by deep mutational scanning technology and optimizing computational models. Therefore, the mechanisms by which different missense variants cause different phenotypes will be fully elucidated.
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Affiliation(s)
- Lu Mao
- Precision Medicine Center, Academy of Medical Science, Zhengzhou University, Zhengzhou 450052, China
| | - Yueqiang Wang
- Basecare Medical Device Co., Ltd., Suzhou 215000, China
| | - Lei An
- Translational Medicine Center, Huaihe Hospital of Henan University, Kaifeng 475000, China
| | - Beiping Zeng
- Precision Medicine Center, Academy of Medical Science, Zhengzhou University, Zhengzhou 450052, China
| | - Yanyan Wang
- The Research and Application Center of Precision Medicine, The Second Affiliated Hospital of Zhengzhou University, Zhengzhou 450014, China
| | - Dmitrij Frishman
- Wissenschaftszentrum Weihenstephan, Technische Universitaet Muenchen, Am Staudengarten 2, 85354 Freising, Germany
| | - Mengli Liu
- Precision Medicine Center, Academy of Medical Science, Zhengzhou University, Zhengzhou 450052, China
| | - Yanyu Chen
- Precision Medicine Center, Academy of Medical Science, Zhengzhou University, Zhengzhou 450052, China
| | - Wenxue Tang
- The Research and Application Center of Precision Medicine, The Second Affiliated Hospital of Zhengzhou University, Zhengzhou 450014, China
| | - Hongen Xu
- Precision Medicine Center, Academy of Medical Science, Zhengzhou University, Zhengzhou 450052, China
- The Research and Application Center of Precision Medicine, The Second Affiliated Hospital of Zhengzhou University, Zhengzhou 450014, China
- Correspondence:
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Connexin Mutations and Hereditary Diseases. Int J Mol Sci 2022; 23:ijms23084255. [PMID: 35457072 PMCID: PMC9027513 DOI: 10.3390/ijms23084255] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 04/04/2022] [Accepted: 04/09/2022] [Indexed: 02/01/2023] Open
Abstract
Inherited diseases caused by connexin mutations are found in multiple organs and include hereditary deafness, congenital cataract, congenital heart diseases, hereditary skin diseases, and X-linked Charcot–Marie–Tooth disease (CMT1X). A large number of knockout and knock-in animal models have been used to study the pathology and pathogenesis of diseases of different organs. Because the structures of different connexins are highly homologous and the functions of gap junctions formed by these connexins are similar, connexin-related hereditary diseases may share the same pathogenic mechanism. Here, we analyze the similarities and differences of the pathology and pathogenesis in animal models and find that connexin mutations in gap junction genes expressed in the ear, eye, heart, skin, and peripheral nerves can affect cellular proliferation and differentiation of corresponding organs. Additionally, some dominant mutations (e.g., Cx43 p.Gly60Ser, Cx32 p.Arg75Trp, Cx32 p.Asn175Asp, and Cx32 p.Arg142Trp) are identified as gain-of-function variants in vivo, which may play a vital role in the onset of dominant inherited diseases. Specifically, patients with these dominant mutations receive no benefits from gene therapy. Finally, the complete loss of gap junctional function or altered channel function including permeability (ions, adenosine triphosphate (ATP), Inositol 1,4,5-trisphosphate (IP3), Ca2+, glucose, miRNA) and electric activity are also identified in vivo or in vitro.
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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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Ichthyoses-A Clinical and Pathological Spectrum from Heterogeneous Cornification Disorders to Inflammation. Dermatopathology (Basel) 2021; 8:107-123. [PMID: 34066992 PMCID: PMC8161842 DOI: 10.3390/dermatopathology8020017] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 04/27/2021] [Accepted: 04/28/2021] [Indexed: 11/22/2022] Open
Abstract
Ichthyoses are inborn keratinization disorders affecting the skin only (non-syndromic) or are associated with diseases of internal organs (syndromic). In newborns, they can be life-threatening. The identification of the gene defects resulted in reclassification and a better understanding of the pathophysiology. Histopathologic patterns include orthohyperkeratosis with a reduced or well-developed stratum granulosum, hyperkeratosis with ortho- and parakeratosis with preserved or prominent stratum granulosum, and epidermolytic ichthyosis. Another pattern features “perinuclear vacuoles and binucleated keratinocytes”, which is associated with keratin mutations. Some ichthyoses are histologically defined by psoriasis-like features, and distinct subtypes show follicular hyperkeratosis. In addition to histological and immunohistochemical methods, these patterns allow a better histopathologic diagnosis.
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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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Metze D, Süßmuth K, Traupe H. [Ichthyoses: a dermatopathological spectrum from heterogeneous cornification disorders to psoriasiform dermatitis]. DER PATHOLOGE 2020; 41:326-333. [PMID: 32458048 DOI: 10.1007/s00292-020-00792-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Ichthyoses are hereditary cornification disorders that occur in isolation (nonsyndromic) or with associated internal diseases (syndromic) and can lead to life-threatening complications. The identification of the genetic causes has led to an understanding of the molecular mechanisms, but also to reclassification. The pathological changes in skin biopsies were also more precisely characterized. Certain histological patterns could be defined, which are based on the defects of epidermal differentiation but also on the inflammatory pattern. Complementary histo- and immunohistochemical methods sometimes allow a precise diagnosis, or at least a limitation of the differential diagnoses.
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Affiliation(s)
- Dieter Metze
- Klinik für Hautkrankheiten, Universitätsklinikum Münster, Von-Esmarch-Str. 56, 48149, Münster, Deutschland.
| | - Kira Süßmuth
- Klinik für Hautkrankheiten, Universitätsklinikum Münster, Von-Esmarch-Str. 56, 48149, Münster, Deutschland
| | - Heiko Traupe
- Klinik für Hautkrankheiten, Universitätsklinikum Münster, Von-Esmarch-Str. 56, 48149, Münster, Deutschland
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Progressive Deformity of the Lower Limbs in a Patient with KID (Keratitis-Ichthyosis-Deafness) Syndrome. Case Rep Orthop 2020; 2020:8747392. [PMID: 32733727 PMCID: PMC7369675 DOI: 10.1155/2020/8747392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/23/2020] [Accepted: 06/29/2020] [Indexed: 11/23/2022] Open
Abstract
Purpose Progressive deformity of the lower limbs can be encountered in a long list of syndromic associations. The baseline tool in the management of such disorders is to approach to a definite diagnosis. Methods We describe a 4-year-old girl who presented with the clinical phenotype and genotype of congenital erythrokeratoderma, keratosis, and sensorineural hearing loss (keratitis-ichthyosis-deafness syndrome) (KID syndrome). She manifested progressive contractures of the knees associated with talipes equinovarus of the feet. The latter deformities were the main reasons behind her severe retardation in acquiring the normal locomotor functions. Results The analysis revealed mutations in intron 1 of the GJB2 gene of C.32G>A (p.Gly11Glu) and c.35delG in the compound heterozygous state. The presence in the genotype of the “dominant” mutation c.32G>A (p.Glu11Glu) was compatible with the clinical phenotype of KID syndrome. Conclusion Surgical interventions through the extension of the hamstring tendons have been performed successfully via the application of an external distraction apparatus, namely, Volkov- Oganesyan. The latter procedures resulted in total release of her awkward knee contractures. Eventually, the child was able to regain the physiological alignment of her lower limbs and resume walking. To the best of our knowledge, the overall management of this child could be the first in the literature.
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Cammarata-Scalisi F, Willoughby CE, Cárdenas Tadich A, Labrador N, Herrera A, Callea M. Clinical, etiopathogenic, and therapeutic aspects of KID syndrome. Dermatol Ther 2020; 33:e13507. [PMID: 32367610 DOI: 10.1111/dth.13507] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/20/2020] [Accepted: 04/28/2020] [Indexed: 11/26/2022]
Abstract
Keratitis-ichthyosis-deafness (KID syndrome) is a syndromes ichthyoses that is clinically and genetically heterogeneous requiring early and long-term multidisciplinary monitoring of affected individuals. A review of the clinical, etiopathogenic and therapeutic aspects is presented of this rare congenital ectodermal disorder.
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Affiliation(s)
| | | | | | | | - Adriana Herrera
- Ophthalmology Unit, University of Los Andes, Mérida, Venezuela
| | - Michele Callea
- Unit of Dentistry, Bambino Gesù Children' Hospital, IRCCS, Rome, Italy
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A case of keratitis, ichthyosis, and deafness syndrome with rickets. JAAD Case Rep 2020; 6:9-12. [PMID: 31890828 PMCID: PMC6928269 DOI: 10.1016/j.jdcr.2019.10.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Inner Ear Connexin Channels: Roles in Development and Maintenance of Cochlear Function. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a033233. [PMID: 30181354 DOI: 10.1101/cshperspect.a033233] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Connexin 26 and connexin 30 are the prevailing isoforms in the epithelial and connective tissue gap junction systems of the developing and mature cochlea. The most frequently encountered variants of the genes that encode these connexins, which are transcriptionally coregulated, determine complete loss of protein function and are the predominant cause of prelingual hereditary deafness. Reducing connexin 26 expression by Cre/loxP recombination in the inner ear of adult mice results in a decreased endocochlear potential, increased hearing thresholds, and loss of >90% of outer hair cells, indicating that this connexin is essential for maintenance of cochlear function. In the developing cochlea, connexins are necessary for intercellular calcium signaling activity. Ribbon synapses and basolateral membrane currents fail to mature in inner hair cells of mice that are born with reduced connexin expression, even though hair cells do not express any connexin. In contrast, pannexin 1, an alternative mediator of intercellular signaling, is dispensable for hearing acquisition and auditory function.
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Xie MX, Yang WP, Luo HJ, Ismail F, Hao YY, Yang JQ. G59S mutation in the GJB2 gene in a Chinese family with classic Vohwinkel syndrome. J Dermatol 2019; 46:154-157. [PMID: 30565282 DOI: 10.1111/1346-8138.14727] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 11/05/2018] [Indexed: 11/28/2022]
Abstract
Vohwinkel syndrome (VS) is a rare autosomal dominant condition, also known as mutilating palmoplantar keratoderma accompanied by sensorineural deafness. The LOR and GJB2 genes are reported to be responsible for VS. The GJB2 gene encodes connexin 26, a component of intercellular gap junctions expressed in various tissues. We report the case of a 31-year-old Chinese woman with classic VS characterized by sensorineural deafness and mutilating palmoplantar keratoderma. Further genetic studies demonstrated a nucleotide change (c.175G>A) in the GJB2 gene, leading to an amino acid alteration (G59S). This identical missense mutation (G59S) has also been reported in a patient with Bart-Pumphrey syndrome. Together with our findings and previous studies, we conclude that the identical mutation (G59S) in the GJB2 gene contributes to various manifestations.
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Affiliation(s)
- Ming-Xing Xie
- Department of Dermatology, Changxing Hospital, Huzhou, China
| | - Wei-Ping Yang
- Department of Stomatology, The First Affiliated Hospital of Huzhou University, Huzhou, China
| | - Hao-Jie Luo
- Department of Dermatology, The First Affiliated Hospital of Huzhou University, Huzhou, China
| | - Ferina Ismail
- Department of Dermatology, The Royal London Hospital, London, UK
| | - Yang-Yang Hao
- Department of Dermatology, The First Affiliated Hospital of Huzhou University, Huzhou, China
| | - Jian-Qiang Yang
- Department of Dermatology, The First Affiliated Hospital of Huzhou University, Huzhou, China
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Youssefian L, Vahidnezhad H, Saeidian AH, Mahmoudi H, Karamzadeh R, Kariminejad A, Huang J, Li L, Jannace TF, Fortina P, Zeinali S, White TW, Uitto J. A novel autosomal recessive GJB2-associated disorder: Ichthyosis follicularis, bilateral severe sensorineural hearing loss, and punctate palmoplantar keratoderma. Hum Mutat 2018; 40:217-229. [PMID: 30431684 DOI: 10.1002/humu.23686] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/26/2018] [Accepted: 10/30/2018] [Indexed: 11/07/2022]
Abstract
Ichthyosis follicularis, a distinct cutaneous entity reported in combination with atrichia, and photophobia has been associated with mutations in MBTPS2. We sought the genetic cause of a novel syndrome of ichthyosis follicularis, bilateral severe sensorineural hearing loss and punctate palmoplantar keratoderma in two families. We performed whole exome sequencing on three patients from two families. The pathogenicity and consequences of mutations were studied in the Xenopus oocyte expression system and by molecular modeling analysis. Compound heterozygous mutations in the GJB2 gene were discovered: a pathogenic c.526A>G; p.Asn176Asp, and a common frameshift mutation, c.35delG; p.Gly12Valfs*2. The p.Asn176Asp missense mutation was demonstrated to significantly reduce the cell-cell gap junction channel activity and increase the nonjunctional hemichannel activity in the Xenopus oocyte expression system. Molecular modeling analyses of the mutant Cx26 protein revealed significant changes in the structural characteristics and electrostatic potential of the Cx26, either in hemichannel or gap junction conformation. Thus, association of a new syndrome of an autosomal recessive disorder of ichthyosis follicularis, bilateral severe sensorineural hearing loss and punctate palmoplantar keratoderma with mutations in GJB2, expands the phenotypic spectrum of the GJB2-associated disorders. The findings attest to the complexity of the clinical consequences of different mutations in GJB2.
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Affiliation(s)
- Leila Youssefian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
- Genetics, Genomics and Cancer Biology PhD Program, Thomas Jefferson University, Philadelphia, PA, USA
| | - Hassan Vahidnezhad
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
- Biotechnology Research Center, Department of Molecular Medicine, Pasteur Institute of Iran, Tehran, Iran
| | - Amir Hossein Saeidian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
- Genetics, Genomics and Cancer Biology PhD Program, Thomas Jefferson University, Philadelphia, PA, USA
| | - Hamidreza Mahmoudi
- Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Razieh Karamzadeh
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | | | - Jianhe Huang
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
| | - Leping Li
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Thomas F Jannace
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Paolo Fortina
- Department of Cancer Biology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA
- Department of Molecular Medicine, Sapienza University, Rome, Italy
| | - Sirous Zeinali
- Biotechnology Research Center, Department of Molecular Medicine, Pasteur Institute of Iran, Tehran, Iran
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
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16
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Guerra L, Castori M, Didona B, Castiglia D, Zambruno G. Hereditary palmoplantar keratodermas. Part II: syndromic palmoplantar keratodermas - Diagnostic algorithm and principles of therapy. J Eur Acad Dermatol Venereol 2018; 32:899-925. [DOI: 10.1111/jdv.14834] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 01/05/2018] [Indexed: 12/19/2022]
Affiliation(s)
- L. Guerra
- Laboratory of Molecular and Cell Biology; Istituto Dermopatico dell'Immacolata-IRCCS; Rome Italy
| | - M. Castori
- Division of Medical Genetics; Casa Sollievo della Sofferenza-IRCCS; San Giovanni Rotondo Italy
| | - B. Didona
- Rare Skin Disease Center; Istituto Dermopatico dell'Immacolata-IRCCS; Rome Italy
| | - D. Castiglia
- Laboratory of Molecular and Cell Biology; Istituto Dermopatico dell'Immacolata-IRCCS; Rome Italy
| | - G. Zambruno
- Genetic and Rare Diseases Research Area and Dermatology Unit; Bambino Gesù Children's Hospital-IRCCS; Rome Italy
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17
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del Castillo FJ, del Castillo I. DFNB1 Non-syndromic Hearing Impairment: Diversity of Mutations and Associated Phenotypes. Front Mol Neurosci 2017; 10:428. [PMID: 29311818 PMCID: PMC5743749 DOI: 10.3389/fnmol.2017.00428] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 12/07/2017] [Indexed: 02/02/2023] Open
Abstract
The inner ear is a very complex sensory organ whose development and function depend on finely balanced interactions among diverse cell types. The many different kinds of inner ear supporting cells play the essential roles of providing physical and physiological support to sensory hair cells and of maintaining cochlear homeostasis. Appropriately enough, the gene most commonly mutated among subjects with hereditary hearing impairment (HI), GJB2, encodes the connexin-26 (Cx26) gap-junction channel protein that underlies both intercellular communication among supporting cells and homeostasis of the cochlear fluids, endolymph and perilymph. GJB2 lies at the DFNB1 locus on 13q12. The specific kind of HI associated with this locus is caused by recessively-inherited mutations that inactivate the two alleles of the GJB2 gene, either in homozygous or compound heterozygous states. We describe the many diverse classes of genetic alterations that result in DFNB1 HI, such as large deletions that either destroy the GJB2 gene or remove a regulatory element essential for GJB2 expression, point mutations that interfere with promoter function or splicing, and small insertions or deletions and nucleotide substitutions that target the GJB2 coding sequence. We focus on how these alterations disrupt GJB2 and Cx26 functions and on their different effects on cochlear development and physiology. We finally discuss the diversity of clinical features of DFNB1 HI as regards severity, age of onset, inner ear malformations and vestibular dysfunction, highlighting the areas where future research should be concentrated.
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Affiliation(s)
- Francisco J. del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Ignacio del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
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18
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Higashino T, Lee JYW, McGrath JA. Advances in the genetic understanding of hypohidrotic ectodermal dysplasia. Expert Opin Orphan Drugs 2017. [DOI: 10.1080/21678707.2017.1405806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Toshihide Higashino
- St John’s Institute of Dermatology, King’s College London, Guy’s Hospital, London, UK
- Department of Integrative Physiology and Bio-Nano Medicine, National Defense Medical College, Tokorozawa, Japan
| | - John Y. W. Lee
- St John’s Institute of Dermatology, King’s College London, Guy’s Hospital, London, UK
| | - John A. McGrath
- St John’s Institute of Dermatology, King’s College London, Guy’s Hospital, London, UK
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19
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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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20
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Srinivas M, Verselis VK, White TW. Human diseases associated with connexin mutations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:192-201. [PMID: 28457858 DOI: 10.1016/j.bbamem.2017.04.024] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 04/20/2017] [Accepted: 04/25/2017] [Indexed: 01/11/2023]
Abstract
Gap junctions and hemichannels comprised of connexins impact many cellular processes. Significant advances in our understanding of the functional role of these channels have been made by the identification of a host of genetic diseases caused by connexin mutations. Prominent features of connexin disorders are the inability of other connexins expressed in the same cell type to compensate for the mutated one, and the ability of connexin mutants to dominantly influence the activity of other wild-type connexins. Functional studies have begun to identify some of the underlying mechanisms whereby connexin channel mutation contributes to the disease state. Detailed mechanistic understanding of these functional differences will help to facilitate new pathophysiology driven therapies for the diverse array of connexin genetic disorders. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Miduturu Srinivas
- Department of Biological and Vision Sciences, SUNY College of Optometry, New York, NY 10036, USA
| | - Vytas K Verselis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA.
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21
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Sakiyama T, Kubo A. Hereditary palmoplantar keratoderma "clinical and genetic differential diagnosis". J Dermatol 2017; 43:264-74. [PMID: 26945534 DOI: 10.1111/1346-8138.13219] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 10/15/2015] [Indexed: 11/29/2022]
Abstract
Hereditary palmoplantar keratoderma (PPK) is a heterogeneous group of disorders characterized by hyperkeratosis of the palm and the sole skin. Hereditary PPK are divided into four groups--diffuse, focal, striate and punctate PPK--according to the clinical patterns of the hyperkeratotic lesions. Each group includes simple PPK, without associated features, and PPK with associated features, such as involvement of nails, teeth and other organs. PPK have been classified by a clinically based descriptive system. In recent years, many causative genes of PPK have been identified, which has confirmed and/or rearranged the traditional classifications. It is now important to diagnose PPK by a combination of the traditional morphological classification and genetic testing. In this review, we focus on PPK without associated features and introduce their morphological features, genetic backgrounds and new findings from the last decade.
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Affiliation(s)
- Tomo Sakiyama
- Department of Dermatology, Keio University School of Medicine, Tokyo, Japan
| | - Akiharu Kubo
- Department of Dermatology, Keio University School of Medicine, Tokyo, Japan
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22
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Yoneda K. Inherited ichthyosis: Syndromic forms. J Dermatol 2017; 43:252-63. [PMID: 26945533 DOI: 10.1111/1346-8138.13284] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 12/01/2015] [Indexed: 12/01/2022]
Abstract
Among diseases that cause ichthyosis as one of the symptoms, there are some diseases that induce abnormalities in organs other than the skin. Of these, diseases with characteristic signs are regarded as syndromes. Although these syndromes are very rare, Netherton syndrome, Sjögren-Larsson syndrome, Conradi-Hünermann-Happle syndrome, Dorfman-Chanarin syndrome, ichthyosis follicularis, atrichia and photophobia (IFAP) syndrome, and Refsum syndrome have been described in texts as representative ones. It is important to know the molecular genetics and pathomechanisms in order to establish an effective therapy and beneficial genetic counseling including a prenatal diagnosis.
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Affiliation(s)
- Kozo Yoneda
- Department of Dermatology, Faculty of Medicine, Kagawa University, Kagawa, Japan
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23
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García IE, Prado P, Pupo A, Jara O, Rojas-Gómez D, Mujica P, Flores-Muñoz C, González-Casanova J, Soto-Riveros C, Pinto BI, Retamal MA, González C, Martínez AD. Connexinopathies: a structural and functional glimpse. BMC Cell Biol 2016; 17 Suppl 1:17. [PMID: 27228968 PMCID: PMC4896260 DOI: 10.1186/s12860-016-0092-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Mutations in human connexin (Cx) genes have been related to diseases, which we termed connexinopathies. Such hereditary disorders include nonsyndromic or syndromic deafness (Cx26, Cx30), Charcot Marie Tooth disease (Cx32), occulodentodigital dysplasia and cardiopathies (Cx43), and cataracts (Cx46, Cx50). Despite the clinical phenotypes of connexinopathies have been well documented, their pathogenic molecular determinants remain elusive. The purpose of this work is to identify common/uncommon patterns in channels function among Cx mutations linked to human diseases. To this end, we compiled and discussed the effect of mutations associated to Cx26, Cx32, Cx43, and Cx50 over gap junction channels and hemichannels, highlighting the function of the structural channel domains in which mutations are located and their possible role affecting oligomerization, gating and perm/selectivity processes.
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Affiliation(s)
- Isaac E García
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Pavel Prado
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Oscar Jara
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Diana Rojas-Gómez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Paula Mujica
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Flores-Muñoz
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Jorge González-Casanova
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Soto-Riveros
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Bernardo I Pinto
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
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24
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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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27
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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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28
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Wang H, Cao X, Lin Z, Lee M, Jia X, Ren Y, Dai L, Guan L, Zhang J, Lin X, Zhang J, Chen Q, Feng C, Zhou EY, Yin J, Xu G, Yang Y. Exome sequencing reveals mutation in GJA1 as a cause of keratoderma-hypotrichosis-leukonychia totalis syndrome. Hum Mol Genet 2014; 24:243-50. [DOI: 10.1093/hmg/ddu442] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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Sokolov M, Brownstein Z, Frydman M, Avraham KB. Apparent phenotypic anticipation in autosomal dominant connexin 26 deafness. J Basic Clin Physiol Pharmacol 2014; 25:289-92. [PMID: 25153233 DOI: 10.1515/jbcpp-2014-0053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 07/07/2014] [Indexed: 11/15/2022]
Abstract
BACKGROUND Connexin 26 (GJB2) mutations are associated with various types of hearing loss, either without associated symptoms or with skin disease, constituting a form of syndromic hearing loss. These mutations can lead to deafness in either a recessive or a dominant autosomal form of inheritance. METHODS Ascertainment of a Jewish Ashkenazi family with nonsyndromic hearing loss led to the construction of a pedigree for a four-generation family, with hearing loss detected in three successive generations. The entire coding region of the GJB2 gene was amplified and sequenced by Sanger sequencing. RESULTS Audiological analysis revealed that the age of onset and severity of hearing loss were earlier and more severe, respectively, in each successive generation of an Ashkenazi Jewish family. A mutation, c.224G>A, leading to missense p.Arg75Gln was detected only in the affected members of the family. CONCLUSIONS The entire coding region of GJB2 should be checked in hearing-impaired patients by Sanger sequencing, rather than examination only of the two most prevalent mutations, regardless of mode of inheritance or ethnicity. Furthermore, predictions regarding phenotype based on genotype can be difficult to make due to clinical variability in multigenerational families, as demonstrated in the family presented in this study.
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30
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Molica F, Meens MJP, Morel S, Kwak BR. Mutations in cardiovascular connexin genes. Biol Cell 2014; 106:269-93. [PMID: 24966059 DOI: 10.1111/boc.201400038] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 06/20/2014] [Indexed: 12/25/2022]
Abstract
Connexins (Cxs) form a family of transmembrane proteins comprising 21 members in humans. Cxs differ in their expression patterns, biophysical properties and ability to combine into homomeric or heteromeric gap junction channels between neighbouring cells. The permeation of ions and small metabolites through gap junction channels or hemichannels confers a crucial role to these proteins in intercellular communication and in maintaining tissue homeostasis. Among others, Cx37, Cx40, Cx43, Cx45 and Cx47 are found in heart, blood and lymphatic vessels. Mutations or polymorphisms in the genes coding for these Cxs have not only been implicated in cardiovascular pathologies but also in a variety of other disorders. While mutations in Cx43 are mostly linked to oculodentodigital dysplasia, Cx47 mutations are associated with Pelizaeus-Merzbacher-like disease and lymphoedema. Cx40 mutations are principally linked to atrial fibrillation. Mutations in Cx37 have not yet been described, but polymorphisms in the Cx37 gene have been implicated in the development of arterial disease. This review addresses current knowledge on gene mutations in cardiovascular Cxs systematically and links them to alterations in channel properties and disease.
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Affiliation(s)
- Filippo Molica
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland; Department of Medical Specializations - Cardiology, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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31
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Chander R, Jabeen M, Barara M, Kataria D. Progressive symmetric erythrokeratoderma with unusual associations. Indian J Dermatol 2014; 59:317. [PMID: 24891689 PMCID: PMC4037979 DOI: 10.4103/0019-5154.131476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Ram Chander
- Department of Dermatology and STD, Lady Hardinge Medical College, New Delhi, India
| | - Masarat Jabeen
- Department of Dermatology and STD, Lady Hardinge Medical College, New Delhi, India
| | - Meenu Barara
- Department of Dermatology and STD, Lady Hardinge Medical College, New Delhi, India
| | - Dinesh Kataria
- Department of Psychiatry, Lady Hardinge Medical College, New Delhi, India. E-mail:
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32
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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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33
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Williams P, Memon A, Sinha T, Fryer A. Connecting with connexins. Australas J Dermatol 2013; 54:287-9. [PMID: 23808595 DOI: 10.1111/ajd.12070] [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: 09/10/2012] [Accepted: 02/03/2013] [Indexed: 11/28/2022]
Abstract
We describe a case of an 18-year-old woman with congenital sensorineural deafness who presented to the dermatology clinic with asymptomatic thickening of the skin over the palmar aspect of her hands and feet. An examination revealed palmoplantar keratoderma of the palms and soles of the feet with no pseudoainhum. Her father wore a hearing aid and his deafness had been thought to be acquired. Mutation analysis of the connexin 26 gene revealed that she carried a paternally inherited mutation, p.Asp46Glu and a maternally inherited M34T variant. The p.Asp46Glu mutation has been described in a family exhibiting non-syndromic autosomal dominant deafness. Although the M34T variant has been described as a non-pathogenic variant or with a very mild phenotype only, its combination with the p.Asp46Glu mutation may account for her mild cutaneous phenotype with later clinical presentation.
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Affiliation(s)
- Penelope Williams
- Department of Dermatology, Royal Liverpool and Broadgreen Hospital NHS Trust, Southport, UK
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34
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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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35
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Abstract
The progress of molecular genetics helps clinicians to prove or exclude a suspected diagnosis for a vast and yet increasing number of genodermatoses. This leads to precise genetic counselling, prenatal diagnosis and preimplantation genetic haplotyping for many inherited skin conditions. It is also helpful in such occasions as phenocopy, late onset and incomplete penetrance, uniparental disomy, mitochondrial inheritance and pigmentary mosaicism. Molecular methods of two genodermatoses are explained in detail, i.e. genodermatoses with skin fragility and neurofibromatosis type 1.
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Affiliation(s)
- Vesarat Wessagowit
- Molecular Genetics Laboratory, The Institute of Dermatology, Bangkok, Thailand.
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36
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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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37
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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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38
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Griepentrog GJ, Lucarelli MJ, Burkat CN, Lemke BN, Rose JG. Periorbital Edema Following Hyaluronic Acid Gel Injection: A Retrospective Review. ACTA ACUST UNITED AC 2011. [DOI: 10.5992/0748-8068-28.4.251] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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39
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Sakabe JI, Yoshiki R, Sugita K, Haruyama S, Sawada Y, Kabashima R, Bito T, Nakamura M, Tokura Y. Connexin 26 (GJB2) mutations in keratitis-ichthyosis-deafness syndrome presenting with squamous cell carcinoma. J Dermatol 2011; 39:814-5. [PMID: 22098592 DOI: 10.1111/j.1346-8138.2011.01414.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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40
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Abstract
Cx (connexin) proteins are components of gap junctions which are aqueous pores that allow intercellular exchange of ions and small molecules. Mutations in Cx genes are linked to a range of human disorders. In the present review we discuss mutations in β-Cx genes encoding Cx26, Cx30, Cx30.3 and Cx31 which lead to skin disease and deafness. Functional studies with Cx proteins have given insights into disease-associated mechanisms and non-gap junctional roles for Cx proteins.
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41
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Affiliation(s)
- K Natsuga
- Department of Dermatology, Hokkaido University Graduate School of Medicine, North 15 West 7, Sapporo 060-8638, Japan.
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42
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Iossa S, Chinetti V, Corvino V, Marciano E, Franzè A. R75Q dominant mutation in GJB2 gene silenced by the in Cis recessive mutation c.35delG. Am J Med Genet A 2010; 152A:2658-60. [PMID: 20815033 DOI: 10.1002/ajmg.a.33630] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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43
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Terrinoni A, Codispoti A, Serra V, Bruno E, Didona B, Paradisi M, Nisticò S, Campione E, Napolitano B, Diluvio L, Melino G. Connexin 26 (GJB2) mutations as a cause of the KID syndrome with hearing loss. Biochem Biophys Res Commun 2010; 395:25-30. [PMID: 20307501 DOI: 10.1016/j.bbrc.2010.03.098] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 03/17/2010] [Indexed: 10/19/2022]
Abstract
KID syndrome (MIM 148210) is an ectodermal dysplasia characterized by the occurrence of localized erythematous scaly skin lesions, keratitis and severe bilateral sensorineural deafness. KID syndrome is inherited as an autosomic dominant disease, due to mutations in the gene encoding gap junction protein GJB2 (connexin 26, Cx26). Cx26 is a component of gap junction channels in the epidermis and in the stria vascularis of the cochlea. These channels play a role in the coordinated exchange of molecules and ions occurring in a wide spectrum of cellular activities. In this paper we describe two patients with Cx26 mutations cause cell death by the alteration of protein trafficking, membrane localization and probably interfering with intracellular ion concentrations. We discuss the pathogenesis of both the hearing and skin phenotypes.
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Affiliation(s)
- Alessandro Terrinoni
- Biochemistry Laboratory, IDI-IRCCS, C/O Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, 00133 Rome, Italy.
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44
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Gap junctions in inherited human disease. Pflugers Arch 2010; 460:451-66. [PMID: 20140684 DOI: 10.1007/s00424-010-0789-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 01/05/2010] [Accepted: 01/12/2010] [Indexed: 12/16/2022]
Abstract
Gap junctions (GJ) provide direct intercellular communication. The structures underlying these cell junctions are membrane-associated channels composed of six integral membrane connexin (Cx) proteins, which can form communicating channels connecting the cytoplasms of adjacent cells. This provides coupled cells with a direct pathway for sharing ions, nutrients, or small metabolites to establish electrical coupling or balancing metabolites in various tissues. Genetic approaches have uncovered a still growing number of mutations in Cxs related to human diseases including deafness, skin disease, peripheral and central neuropathies, cataracts, or cardiovascular dysfunctions. The discovery of a growing number of inherited human disorders provides an unequivocal demonstration that gap junctional communication is crucial for diverse physiological processes.
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45
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Neoh CY, Chen H, Ng SK, Lane EB, Common JEA. A rare connexin 26 mutation in a patient with a forme fruste of keratitis-ichthyosis-deafness (KID) syndrome. Int J Dermatol 2009; 48:1078-81. [PMID: 19785089 DOI: 10.1111/j.1365-4632.2009.04136.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Keratitis-ichthyosis-deafness (KID) syndrome is a rare ectodermal dysplasia characterized by generalized erythrokeratotic plaques, sensorineural hearing loss, and vascularizing keratitis. Cutaneous changes and hearing loss typically present in early childhood, whereas ocular symptoms present later. Mutations in the connexin (Cx) 26 gene, GJB2, are now established to underlie many of the affected cases, with the majority of patients harboring the p.D50N mutation. METHODS A rare patient demonstrating features of incomplete KID syndrome associated with an uncommon Cx26 gene mutation is described. RESULTS The patient presented late in adolescence with partial features of KID syndrome. There was limited cutaneous involvement and the rare association of cystic acne. Both hearing impairment and ophthalmic involvement were mild in severity. Genetic mutation analysis revealed a previously described, rare mutation in GJB2, resulting in a glycine to arginine change at codon 12 (p.G12R). CONCLUSIONS This report describes a patient exhibiting characteristics suggestive of a late-onset, incomplete form of KID syndrome with the GJB2 mutation (p.G12R). The p.G12R mutation has only been described in one other patient with KID syndrome, whose clinical presentation was not characterized.
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Affiliation(s)
- Ching Yin Neoh
- National Skin Center, Institute of Medical Biology, 1 Mandalay Road, Singapore.
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46
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Abstract
Gap junctions allow the exchange of ions and small molecules between adjacent cells through intercellular channels formed by connexin proteins, which can also form functional hemichannels in nonjunctional membranes. Mutations in connexin genes cause a variety of human diseases. For example, mutations in GJB2, the gene encoding connexin-26 (Cx26), are not only a major cause of nonsyndromic deafness, but also cause syndromic deafness associated with skin disorders such as palmoplantar keratoderma, keratitis-ichthyosis deafness syndrome, Vohwinkel syndrome, hystrix-ichthyosis deafness syndrome and Bart-Pumphrey syndrome. The most common mutation in the Cx26 gene linked to nonsyndromic deafness is 35DeltaG, a frameshift mutation leading to an early stop codon. The large number of deaf individuals homozygous for 35DeltaG do not develop skin disease. Similarly, there is abundant experimental evidence to suggest that other Cx26 loss-of-function mutations cause deafness, but not skin disease. By contrast, Cx26 mutations that cause both skin diseases and deafness are all single amino acid changes. Since nonsyndromic deafness is predominantly a loss-of-function disorder, it follows that the syndromic mutants must show an alteration, or gain, of function to cause skin disease. Here, we summarise the functional consequences and clinical phenotypes resulting from Cx26 mutations that cause deafness and skin disease.
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47
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Abstract
Congenital ichthyoses are a group of genetic disorders with defective cornification, clinically characterized by scaling of the skin. Additionally, distinctive cutaneous inflammation can often be observed. For most of the patients these diseases lead to a significant restriction in quality of life. The diagnostic hallmarks are discussed. The diagnostic criteria include clinical and histological findings, often enhanced or confirmed by specialized tests. Because many of the congenital ichthyoses are extremely rare, their accurate diagnosis is often carried out in specialized centers. After discussing the vulgar ichthyoses as well as the diagnostic and therapeutic options in part one, in this second part we review congenital ichthyoses both with and without associated symptoms, focusing on the common genetic changes and their clinical phenotype. Specific therapies are still not available for most of these disorders. The use of different topical agents (e. g. urea, retinoids and salicylic acid) and baths followed by mechanical keratolysis (sometimes in combination with systemic retinoids) reduce skin symptoms. Patients with uncommon congenital ichthyoses often benefit from interdisciplinary management which involves specialized dermatological centers.
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Affiliation(s)
- Markus Krug
- Department of Dermatology, University of Tübingen, Germany.
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48
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Iossa S, Chinetti V, Auletta G, Laria C, De Luca M, Rienzo M, Giannini P, Delfino M, Ciccodicola A, Marciano E, Franzé A. New evidence for the correlation of the p.G130V mutation in the GJB2 gene and syndromic hearing loss with palmoplantar keratoderma. Am J Med Genet A 2009; 149A:685-8. [PMID: 18688874 DOI: 10.1002/ajmg.a.32462] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The GJB2 gene located on chromosome 13q12 and encoding the connexin 26 (Cx26) protein, a transmembrane protein involved in cell-cell attachment of almost all tissues, including the skin, causes autosomal recessive and sometimes dominant nonsyndromic sensorineural hearing loss. GJB2 mutations have also been identified in syndromic disorders exhibiting hearing loss associated with skin problems. Recently, a new mutation, p.G130V in the GJB2 gene has been reported as causative for Vohwinkel syndrome. In this case the p.G130V mutation was found in two patients (son and father) with palmoplantar keratoderma. The father also showed also skin constrictions of the 2nd and 3rd toes of the right foot. Here, we report on another family with palmoplantar keratoderma associated with a dominant form of hearing loss confirming the genotype-phenotype correlation between the mutation p.G130V and the skin abnormalities observed in syndromic disorders with hearing loss as described by [Snoeckx et al. (2005) Hum Mutat 26:60-65].
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Affiliation(s)
- Sandra Iossa
- Unit of Audiology, Department of Neurosciences, University of Naples Federico II, Naples, Italy
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49
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van Steensel MAM, Oranje AP, van der Schroeff JG, Wagner A, van Geel M. The missense mutation G12D in connexin30.3 can cause both erythrokeratodermia variabilis of Mendes da Costa and progressive symmetric erythrokeratodermia of Gottron. Am J Med Genet A 2009; 149A:657-61. [PMID: 19291775 DOI: 10.1002/ajmg.a.32744] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Progressive symmetric erythrokeratoderma of Gottron (PSEK) is commonly distinguished from erythrokeratodermia variabilis Mendes da Costa (EKV). However, conclusive proof that the disorders are identical is still lacking. We performed mutation analysis and microsatellite haplotyping in two independently referred patients with PSEK and three patients from a previously published family with EKV. All patients had the same mutation in the GJB4 gene causing the amino acid substitution p.Gly12Asp (G12D). Haplotype analysis showed that all five patients had the same allelic haplotype over 2 Mb covering the disease locus. Apparently, the same GJB4 mutation may cause either an EKV or a PSEK phenotype. A single ancestral founder might have introduced EKV in the Netherlands.
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Affiliation(s)
- M A M van Steensel
- Department of Dermatology, Maastricht University Medical Center, Maastricht, The Netherlands.
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50
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Yuan Y, Huang D, Yu F, Zhu X, Kang D, Yuan H, Han D, Dai P. A de novo GJB2 (connexin 26) mutation, R75W, in a Chinese pedigree with hearing loss and palmoplantar keratoderma. Am J Med Genet A 2009; 149A:689-92. [PMID: 18924167 DOI: 10.1002/ajmg.a.32461] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yongyi Yuan
- Department of Otolaryngology, PLA General Hospital, Beijing, People's Republic of China
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