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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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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: 3] [Impact Index Per Article: 3.0] [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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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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Abstract
Changes in nail color can provide important clues of underlying systemic and skin disease. In particular, white discoloration (leukonychia) has a high prevalence with a wide array of potential relevant causes, from simple manicure habits to life-threatening liver or kidney failure. Therefore, a reliable assessment of the patient with leukonychia is essential. In the past, two classifications for leukonychia have been presented. The morphological classifies the nail according to the distribution of the white lines: total, partial, transversal, and longitudinal leukonychia. Mees’ and Muehrcke’s lines are examples of transversal leukonychia, while Terry’s and Lindsay’s nails are examples of total and partial leukonychia. The anatomical classifies according to the structure responsible for the white color: the nail plate in true leukonychia, the nail bed in apparent leukonychia, and the surface only in pseudoleukonychia. In this review, both morphological and anatomical features have been combined in an algorithm that enables clinicians to approach leukonychia efficiently and effectively.
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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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Hamie L, Eid E, Khalil S, Ghaoui N, Abbas O, Hamie M, Akl PA, Kurban M. Genodermatoses with hearing impairment. J Am Acad Dermatol 2021; 85:931-944. [PMID: 34153387 DOI: 10.1016/j.jaad.2021.06.850] [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: 01/11/2021] [Revised: 03/14/2021] [Accepted: 06/15/2021] [Indexed: 10/21/2022]
Abstract
Hearing loss is a prominent feature in multiple genodermatoses. Underappreciation of auditory deficits can misdirect proper diagnosis by the treating dermatologist. This review reviews the anatomic, developmental, and embryologic aspects that characterize the ear and summarizes genodermatoses that have aberrant auditory findings. The latter are classified into neural crest, metabolic, pigmentary, craniofacial, and a miscellaneous category of disorders lacking specific cutaneous findings. The algorithms provided in this review enable treating dermatologists to better recognize and manage genodermatoses with ear involvement.
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Affiliation(s)
- Lamiaa Hamie
- Department of Dermatology, American University of Beirut Medical Centre, Beirut, Lebanon
| | - Edward Eid
- Department of Dermatology, American University of Beirut Medical Centre, Beirut, Lebanon
| | - Samar Khalil
- Department of Dermatology, American University of Beirut Medical Centre, Beirut, Lebanon
| | - Nohra Ghaoui
- Department of Internal Medicine, American University of Beirut Medical Centre, Beirut, Lebanon
| | - Ossama Abbas
- Department of Dermatology, American University of Beirut Medical Centre, Beirut, Lebanon
| | | | | | - Mazen Kurban
- Department of Dermatology, American University of Beirut Medical Centre, Beirut, Lebanon; Department of Biochemistry and Molecular Genetics, American University of Beirut, Beirut, Lebanon; Division of Genomics and Translational Biomedicine, College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar.
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7
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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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Asgari T, Naji M, Mansouri P, Mahmoudi H, Zabihi M, Youssefian L, Mahdavi M, Naraghi ZS, Zeinali S, Vahidnezhad H, Uitto J. Keratitis-ichthyosis-deafness syndrome: Phenotypic heterogeneity and treatment perspective of patients with p.Asp50Asn GJB2 mutation. Dermatol Ther 2020; 33:e14493. [PMID: 33136289 DOI: 10.1111/dth.14493] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 10/26/2020] [Indexed: 11/29/2022]
Abstract
Keratitis-ichthyosis-deafness (KID) syndrome is caused by mutations in the GJB2 gene encoding connexin 26, a component of transmembrane hemichannels which form gap junction channels, critical for cell-cell communication. Here, we report two patients from two distinct families with KID syndrome with the same GJB2 mutation (p.Asp50Asn); in both cases the mutation was de novo, as the parents depicted the wild-type allele only. The patients' cutaneous manifestations were strikingly different illustrating the wide spectrum of phenotype of these patients, even with the same GJB2 mutation. One of the patients was treated with acitretin with dramatic improvement in his skin findings, illustrating the role of oral acitretin in treatment of patients with KID syndrome. Collectively, these patients attest to the phenotypic spectrum of KID syndrome, with therapeutic perspective.
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Affiliation(s)
- Tina Asgari
- Department of Biology, Science, and Research Branch, Islamic Azad University, Tehran, Iran
| | - Mahtab Naji
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.,Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Parvin Mansouri
- Skin and Stem Cell Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Hamidreza Mahmoudi
- Department of Dermatology, Tehran University of Medical Sciences, Razi Hospital, Tehran, Iran
| | | | - Leila Youssefian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.,Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Mohammadreza Mahdavi
- Thalassemia Research Center, Mazandaran University of Medical Sciences, Sari, Iran
| | - Zahra Safaei Naraghi
- Departments of Dermatology and Pathology, Tehran University of Medical Sciences, Razi Hospital, Tehran, Iran
| | - Sirous Zeinali
- Kawsar Human Genetics Research Center, Tehran, Iran.,Department of Molecular Medicine, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Hassan Vahidnezhad
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.,Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.,Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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Adadey SM, Wonkam-Tingang E, Twumasi Aboagye E, Nayo-Gyan DW, Boatemaa Ansong M, Quaye O, Awandare GA, Wonkam A. Connexin Genes Variants Associated with Non-Syndromic Hearing Impairment: A Systematic Review of the Global Burden. Life (Basel) 2020; 10:life10110258. [PMID: 33126609 PMCID: PMC7693846 DOI: 10.3390/life10110258] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/18/2020] [Accepted: 10/27/2020] [Indexed: 12/21/2022] Open
Abstract
Mutations in connexins are the most common causes of hearing impairment (HI) in many populations. Our aim was to review the global burden of pathogenic and likely pathogenic (PLP) variants in connexin genes associated with HI. We conducted a systematic review of the literature based on targeted inclusion/exclusion criteria of publications from 1997 to 2020. The databases used were PubMed, Scopus, Africa-Wide Information, and Web of Science. The protocol was registered on PROSPERO, the International Prospective Register of Systematic Reviews, with the registration number “CRD42020169697”. The data extracted were analyzed using Microsoft Excel and SPSS version 25 (IBM, Armonk, New York, United States). A total of 571 independent studies were retrieved and considered for data extraction with the majority of studies (47.8% (n = 289)) done in Asia. Targeted sequencing was found to be the most common technique used in investigating connexin gene mutations. We identified seven connexin genes that were associated with HI, and GJB2 (520/571 publications) was the most studied among the seven. Excluding PLP in GJB2, GJB6, and GJA1 the other connexin gene variants (thus GJB3, GJB4, GJC3, and GJC1 variants) had conflicting association with HI. Biallelic GJB2 PLP variants were the most common and widespread variants associated with non-syndromic hearing impairment (NSHI) in different global populations but absent in most African populations. The most common GJB2 alleles found to be predominant in specific populations include; p.Gly12ValfsTer2 in Europeans, North Africans, Brazilians, and Americans; p.V37I and p.L79Cfs in Asians; p.W24X in Indians; p.L56Rfs in Americans; and the founder mutation p.R143W in Africans from Ghana, or with putative Ghanaian ancestry. The present review suggests that only GJB2 and GJB3 are recognized and validated HI genes. The findings call for an extensive investigation of the other connexin genes in many populations to elucidate their contributions to HI, in order to improve gene-disease pair curations, globally.
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Affiliation(s)
- Samuel Mawuli Adadey
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon GA184, Accra, Greater Accra Region, Ghana; (S.M.A.); (O.Q.); (G.A.A.)
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa;
| | - Edmond Wonkam-Tingang
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa;
| | - Elvis Twumasi Aboagye
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa;
| | - Daniel Wonder Nayo-Gyan
- Department of Applied Chemistry and Biochemistry, C. K. Tedam University of Technology and Applied Sciences, P.O. Box 24, Navrongo 00000, Upper East Region, Ghana;
| | - Maame Boatemaa Ansong
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
| | - Osbourne Quaye
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon GA184, Accra, Greater Accra Region, Ghana; (S.M.A.); (O.Q.); (G.A.A.)
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
| | - Gordon A. Awandare
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon GA184, Accra, Greater Accra Region, Ghana; (S.M.A.); (O.Q.); (G.A.A.)
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa;
- Correspondence: ; Tel.: +27-21-4066307
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Beach R, Abitbol JM, Allman BL, Esseltine JL, Shao Q, Laird DW. GJB2 Mutations Linked to Hearing Loss Exhibit Differential Trafficking and Functional Defects as Revealed in Cochlear-Relevant Cells. Front Cell Dev Biol 2020; 8:215. [PMID: 32300592 PMCID: PMC7142214 DOI: 10.3389/fcell.2020.00215] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/12/2020] [Indexed: 11/13/2022] Open
Abstract
GJB2 gene (that encodes Cx26) mutations are causal of hearing loss highlighting the importance of Cx26-based channel signaling amongst the supporting cells in the organ of Corti. While the majority of these GJB2 mutations are inherited in an autosomal recessive manner, others are inherited in an autosomal dominant manner and lead to syndromic hearing loss as well as skin diseases. To assess if common or divergent mechanisms are at the root of GJB2-linked hearing loss, we expressed several mutants in cochlear-relevant HEI-OC1 cells derived from the developing organ of Corti. Since supporting cells of the mature mammalian organ of Corti have negligible Cx43, but HEI-OC1 cells are rich in Cx43, we first used CRISPR-Cas9 to ablate endogenous Cx43, thus establishing a connexin-deficient platform for controlled reintroduction of hearing-relevant connexins and Cx26 mutants. We found three distinct outcomes and cellular phenotypes when hearing loss-linked Cx26 mutants were expressed in cochlear-relevant cells. The dominant syndromic Cx26 mutant N54K had trafficking defects and did not fully prevent wild-type Cx26 gap junction plaque formation but surprisingly formed gap junctions when co-expressed with Cx30. In contrast, the dominant syndromic S183F mutant formed gap junctions incapable of transferring dye and, as expected, co-localized in the same gap junctions as wild-type Cx26 and Cx30, but also gained the capacity to intermix with Cx43 within gap junctions. Both recessive non-syndromic Cx26 mutants (R32H and R184P) were retained in intracellular vesicles including early endosomes and did not co-localize with Cx30. As might be predicted, none of the Cx26 mutants prevented Cx43 gap junction plaque formation in Cx43-rich HEI-OC1 cells while Cx43-ablation had little effect on the expression of reference genes linked to auditory cell differentiation. We conclude from our studies in cochlear-relevant cells that the selected Cx26 mutants likely evoke hearing loss via three unique connexin defects that are independent of Cx43 status.
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Affiliation(s)
- Rianne Beach
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Julia M. Abitbol
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Brian L. Allman
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Jessica L. Esseltine
- Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Qing Shao
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Dale W. Laird
- Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
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Yu X, Lin Y, Xu J, Che T, Li L, Yang T, Wu H. Molecular epidemiology of Chinese Han deaf patients with bi-allelic and mono-allelic GJB2 mutations. Orphanet J Rare Dis 2020; 15:29. [PMID: 31992338 PMCID: PMC6986010 DOI: 10.1186/s13023-020-1311-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 01/17/2020] [Indexed: 02/07/2023] Open
Abstract
Background Recessive mutations in GJB2 is the most common cause of genetic hearing loss worldwide. The aim of this study is to determine the spectrum and frequency of GJB2 variants in Chinese Han deaf patients and to investigate the underlying causative genes in patients with mono-allelic GJB2 mutations. Methods We analyzed the mutation screening results of GJB2 in 1852 Chinese Han probands with apparently autosomal-recessive hearing loss in our laboratory. Targeted next-generation sequencing of 139 known deafness-related genes were performed in 44 probands with mono-allelic GJB2 mutations. Results Bi-allelic GJB2 mutations was identified in 25.65% of patients, in which the c.235delC (p.L79Cfs*3) mutation is the most frequent cause for both severe-to-profound (84.93%) and mild-to-moderate hearing loss (54.05%), while the c.109G > A (p.V37I) mutation is another frequent cause for mild-to-moderate hearing loss (40.54%). In 3.89% of patients only one mutant allele can be identified in GJB2. Targeted next generation sequencing in 44 such probands revealed digenic heterozygous mutations in GJB2/GJB6 and GJB2/GJB3 as the likely pathogenic mechanism in three probands. In 13 probands, on the other hand, pathogenic mutations in other deafness-associated genes (STRC, EYA1, MITF, PCDH15, USH2A, MYO15A, CDH23, OTOF, SLC26A4, SMPX, and TIMM8A) can be identified as the independent genetic cause, suggesting that the mono-allelic GJB2 mutations in those probands is likely co-incidental. Conclusions Our results demonstrated that GJB2 should be a primary target for mutation screening in Chinese Han deaf patients, and those with mono-allelic GJB2 mutations should be further screened by next generation sequencing.
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Affiliation(s)
- Xiaoyu Yu
- Department of Otorhinolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Yun Lin
- Department of Otorhinolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Jun Xu
- Department of Otorhinolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Tuanjie Che
- Key Laboratory of Functional Genomic and Molecular Diagnosis of Gansu Province, Lanzhou, 730030, China
| | - Lin Li
- Laboratory of Precision Medicine and Translational Medicine, Suzhou Hospital Affiliated to Nanjing Medical University, Suzhou Science and Technology Town Hospital, Suzhou, 215153, China
| | - Tao Yang
- Department of Otorhinolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. .,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China. .,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China.
| | - Hao Wu
- Department of Otorhinolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. .,Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China. .,Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China.
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12
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Stylianaki EA, Karpouzis A, Tripsianis G, Veletza S. Assessment of Gap Junction Protein Beta-2 rs3751385 Gene Polymorphism in Psoriasis Vulgaris. J Clin Med Res 2019; 11:642-650. [PMID: 31523338 PMCID: PMC6731047 DOI: 10.14740/jocmr3845] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 06/25/2019] [Indexed: 02/05/2023] Open
Abstract
Background Gap junction protein beta 2 (GJB2) upregulation in psoriasis transcriptome analysis as well as connexin 26 (Cx26, encoded by GJB2) expression upregulation in psoriatic plaques has already been substantiated. GJB2 rs72474224 and rs3751385 have been correlated with psoriasis vulgaris incidence in Chinese populations. Here we study the effect of rs3751385 in patients suffering from psoriasis vulgaris in a Caucasian Greek population at the prefecture of Thrace in Northern Greece. Methods One hundred and seventy-three (111 males and 62 females) psoriatic patients (108 were of early-onset psoriasis) and 171 matched controls were included in the study. Genomic DNA was extracted from peripheral blood leukocytes and genotyping was carried out by polymerase chain reaction-restriction-fragment length polymorphism (PCR-RFLP). Results A statistically significant lower frequency of C/T genotype in late-onset male psoriasis vulgaris (P = 0.029) as well as of T allele in female early-onset psoriasis vulgaris (P = 0.049) were ascertained. Conclusions On condition that all other genetic or environmental factors remain stable, the existence and possible interaction between GJB2 rs3751385 C and T alleles in male psoriatic patients may be considered as protective gene component against late-onset psoriasis appearance, while presence of the T allele in female might block the histogenetic mechanisms of early-onset psoriasis lesions.
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Affiliation(s)
- Elli-Anna Stylianaki
- Department of Biology, Faculty of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
| | - Anthony Karpouzis
- Department of Dermatology, Faculty of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
| | - Gregory Tripsianis
- Department of Medical Statistics, Faculty of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
| | - Stavroula Veletza
- Department of Biology, Faculty of Medicine, Democritus University of Thrace, Alexandroupolis, Greece
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13
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Acquired Leukonychia of the Distal Nail Plate: A Morphologic and Proteomic Analysis. Am J Dermatopathol 2019; 42:261-264. [PMID: 31415249 DOI: 10.1097/dad.0000000000001473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Leukonychia, or whitening of the nail plate, is a common disease that was first described in 1919. Leukonychia is classified as acquired or congenital and may be due to abnormality of the nail bed (pseudoleukonychia) or nail plate (true leukonychia). The distal whitened area of the nail plate was clipped from a 31-year-old woman with striated leukonychia and a 32-year-old man and 34-year-old woman with punctate leukonychia. Routine hematoxylin and eosin staining of all clipped samples was performed. A piece of nail with leukonychia and a normal nail from case 2 were sent to the Mayo Clinic for mass spectrometric analysis. On hematoxylin and eosin examination, all leukonychia samples showed odd-appearing eosinophilic linear parakeratinization in the mid-segment of the nail plate. Mass spectrometric analysis of case 2 revealed serum proteins (albumin, serotransferrin IgG, gamma chain, IgG lambda chain, and haptoglobulin) and hair proteins that were not found in the keratin content of the normal nail (keratin type Ha1 and cuticular keratin Ha4). This is the first description of odd-appearing linear parakeratosis and the first proteomic analysis showing abnormal protein content in acquired leukonychia.
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14
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Mammano F. Inner Ear Connexin Channels: Roles in Development and Maintenance of Cochlear Function. Cold Spring Harb Perspect Med 2019; 9:a033233. [PMID: 30181354 PMCID: PMC6601451 DOI: 10.1101/cshperspect.a033233] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Connexin 26 and connexin 30 are the prevailing isoforms in the epithelial and connective tissue gap junction systems of the developing and mature cochlea. The most frequently encountered variants of the genes that encode these connexins, which are transcriptionally coregulated, determine complete loss of protein function and are the predominant cause of prelingual hereditary deafness. Reducing connexin 26 expression by Cre/loxP recombination in the inner ear of adult mice results in a decreased endocochlear potential, increased hearing thresholds, and loss of >90% of outer hair cells, indicating that this connexin is essential for maintenance of cochlear function. In the developing cochlea, connexins are necessary for intercellular calcium signaling activity. Ribbon synapses and basolateral membrane currents fail to mature in inner hair cells of mice that are born with reduced connexin expression, even though hair cells do not express any connexin. In contrast, pannexin 1, an alternative mediator of intercellular signaling, is dispensable for hearing acquisition and auditory function.
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Affiliation(s)
- Fabio Mammano
- University of Padova, Department of Physics and Astronomy "G. Galilei," Padova 35129, Italy
- CNR Institute of Cell Biology and Neurobiology, Monterotondo 00015, Italy
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai 201210, China
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15
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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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16
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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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17
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Khan T, Khan M, Yousaf A, Khan S, Naeem M, Shah A, Murtaza G, Ali A, Jabeen N, Hussain HMJ, Ma H, Zhang Y, Zubair M, Jiang X, Zhang H. Whole exome sequencing identifies a novel dominant missense mutation underlying leukonychia in a Pakistani family. J Hum Genet 2018; 63:1071-1076. [PMID: 30033443 DOI: 10.1038/s10038-018-0491-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 06/17/2018] [Accepted: 06/28/2018] [Indexed: 02/08/2023]
Abstract
Hereditary leukonychia (also known as porcelain nails or white nails) is a genetic disorder. It may exist as an isolated feature or associated with other cutaneous or systemic disorders. Although a number of genes have been described to cause leukonychia, still the underlying genetic etiologies of many cases remain unknown. Here, we report a Pakistani family presenting leukonychia and koilonychia nails in mother and five of her kids. All the affected individuals had white to pale nails in appearance exhibiting complete and partial leukonychia, respectively. Similarly, nails of finger and toe appeared brittle and concave, showing the characteristics features of koilonychia. Whole exome sequencing and subsequent Sanger sequencing identified a pathogenic novel missense mutation (c.1390G>A, p.Glu464Lys) in PLCD1, co-segregating with the disorder in an autosomal dominant pattern. In silico prediction tools supported the pathogenicity of the identified mutation. Literature review determined that mutations in PLCD1 only cause leukonychia. Therefore, our findings add another pathogenic variant to the PLCD1 mutation pool causing leukonychia that would help to understand the underlying molecular mechanism.
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Affiliation(s)
- Teka Khan
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Manan Khan
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Ayesha Yousaf
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Saadullah Khan
- Department of Biotechnology and Genetic Engineering, Kohat University of Science and Technology, Kohat, Pakistan
| | - Muhammad Naeem
- Medical Genetics Research Laboratory, Department of Biotechnology, Quaid-I-Azam University, Islamabad, Pakistan
| | - Akram Shah
- Department of Zoology, University of Peshawar, Peshawar, Pakistan
| | - Ghulam Murtaza
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Asim Ali
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Nazish Jabeen
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Hafiz Muhammad Jafar Hussain
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Hui Ma
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Yuanwei Zhang
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Muhammad Zubair
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Xiaohua Jiang
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China
| | - Huan Zhang
- USTC-SJH Joint Center for Human Reproduction and Genetics, The CAS Key Laboratory of Innate Immunity and Chronic Diseases, Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China (USTC), Collaborative Innovation Center of Genetics and Development, Hefei, 230027, Anhui, China.
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18
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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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19
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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: 65] [Impact Index Per Article: 9.3] [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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20
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Bai D, Yue B, Aoyama H. Crucial motifs and residues in the extracellular loops influence the formation and specificity of connexin docking. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:9-21. [PMID: 28693896 DOI: 10.1016/j.bbamem.2017.07.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 06/25/2017] [Accepted: 07/03/2017] [Indexed: 12/19/2022]
Abstract
Most of the early studies on gap junction (GJ) channel function and docking compatibility were on rodent connexins, while recent research on GJ channels gradually shifted from rodent to human connexins largely due to the fact that mutations in many human connexin genes are found to associate with inherited human diseases. The studies on human connexins have revealed some key differences from those found in rodents, calling for a comprehensive characterization of human GJ channels. Functional studies revealed that docking and formation of functional GJ channels between two hemichannels are possible only between docking-compatible connexins. Two groups of docking-compatible rodent connexins have been identified. Compatibility is believed to be due to their amino acid residue differences at the extracellular loop domains (E1 and E2). Sequence alignment of the E1 and E2 domains of all connexins known to make GJs revealed that they are highly conserved and show high sequence identity with human Cx26, which is the only connexin with near atomic resolution GJ structure. We hypothesize that different connexins have a similar structure as that of Cx26 at the E1 and E2 domains and use the corresponding residues in their E1 and E2 domains for docking. Based on the Cx26 GJ structure and sequence analysis of well-studied connexins, we propose that the E1-E1 docking interactions are staggered with each E1 interacting with two E1s on the docked connexon. The putative E1 docking residues are conserved in both docking-compatible and -incompatible connexins, indicating that E1 does not likely serve a role in docking compatibility. However, in the case of E2-E2 docking interactions, the putative docking residues are only conserved within the docking-compatible connexins, suggesting the E2 is likely to serve the function of docking compatibility. Docking compatibility studies on human connexins have attracted a lot of attention due to the fact that putative docking residues are mutational hotspots for several connexin-linked human diseases. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Donglin Bai
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
| | - Benny Yue
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Hiroshi Aoyama
- Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan
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21
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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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22
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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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23
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Wang HH, Feng Y, Li HB, Wu H, Mei LY, Wang XW, Jiang L, He CF. Digenic mutations involving both the BSND and GJB2 genes detected in Bartter syndrome type IV. Int J Pediatr Otorhinolaryngol 2017; 92:17-20. [PMID: 28012523 DOI: 10.1016/j.ijporl.2016.10.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 10/23/2016] [Accepted: 10/24/2016] [Indexed: 11/30/2022]
Abstract
Bartter syndrome type IV, characterized by salt-losing nephropathies and sensorineural deafness, is caused by mutations of BSND or simultaneous mutations of both CLCNKA and CLCNKB. GJB2 is the primary causative gene for non-syndromic sensorineural deafness and associated with several syndromic sensorineural deafness. Owing to the rarity of Bartter syndrome, only a few mutations have been reported in the abovementioned causative genes. To investigate the underlying mutations in a Chinese patient with Bartter syndrome type IV, genetic analysis of BSND, CLCNKA, CLCNKB and GJB2 were performed by polymerase chain reaction and direct sequencing. Finally, double homozygous mutations c.22C > T (p.Arg8Trp) and c.127G > A (Val43Ile) were detected in exon 1 of BSND. Intriguingly, compound heterozygous mutations c.235delC (p.Leu79CysfsX3) and c.109G > A (p.Val37Ile) were also revealed in exon 2 of GJB2 in the same patient. No pathogenic mutations were found in CLCNKA and CLCNKB. Our results indicated that the homozygous mutation c.22C > T was the key genetic reason for the proband, and a digenic effect of BSND and GJB2 might contributed to sensorineural deafness. To our knowledge, it was the first report showing that the GJB2 gene mutations were detected in Bartter syndrome.
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Affiliation(s)
- Hong-Han Wang
- Department of Head and Neck Surgery, Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, 410013, China
| | - Yong Feng
- Department of Otolaryngology, Head & Neck Surgery, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China; State Key Laboratory of Medical Genetics, Changsha, 410078, Hunan, China; Province Key Laboratory of Otolaryngology Critical Diseases, Changsha, 410008, Hunan, China
| | - Hai-Bo Li
- Department of Ophtalmology, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
| | - Hong Wu
- Department of Otolaryngology, Head & Neck Surgery, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
| | - Ling-Yun Mei
- Department of Otolaryngology, Head & Neck Surgery, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
| | - Xing-Wei Wang
- Department of Otolaryngology, Head & Neck Surgery, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
| | - Lu Jiang
- Department of Otolaryngology, Head & Neck Surgery, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
| | - Chu-Feng He
- Department of Otolaryngology, Head & Neck Surgery, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China.
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24
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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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25
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Intra-familial phenotypic variability in a Moroccan family with hearing loss and palmoplantar keratoderma (PPK). Curr Res Transl Med 2016; 64:61-4. [PMID: 27316387 DOI: 10.1016/j.retram.2016.01.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 01/27/2016] [Indexed: 01/03/2023]
Abstract
Mutations in the GJB2 gene encoding connexin 26 are the main cause of hereditary hearing impairment. These mutations generate mainly autosomal recessive and rarely autosomal dominant deafness. Dominant mutations in GJB2 can be responsible for isolated deafness as well as syndromic hearing loss associated with various skin abnormalities. Until now few papers discuss dominant mutations in the GJB2 gene. In this work we report a rare case about a Moroccan family with a compound heterozygous mutation (the dominant p.R75Q and the recessive c.35delG alleles) in the GJB2 gene with intra-familial phenotypic variability. This study reinforces the involvement of p.R75Q mutation of GJB2 in syndromic deafness associated with dermatological diseases the palmoplantar keratoderma.
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26
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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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27
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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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28
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Pandey N, Xavier DF, Chatterjee A, Mani RS, Hiremagalore R, Tharakan A, Rajashekhar B, Anand A. Functional Analysis of a Novel Connexin30 Mutation in a Large Family with Hearing Loss, Pesplanus, Ichthyosis, Cutaneous Nodules, and Keratoderma. Ann Hum Genet 2015; 80:11-9. [PMID: 26620415 DOI: 10.1111/ahg.12141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Accepted: 09/11/2015] [Indexed: 11/28/2022]
Abstract
Mutations in the gap-junction gene Cx30 (Connexin30, GJB6) are a known cause of hearing loss. Here, we report our findings on a large multigeneration family in which severe to profound sensorineural hearing impairment is associated with a variety of skin-related anomalies. Genome-wide analysis of the family showed that the locus maps to chromosome region 13ptel-q12.1 and that a novel mutation, p.N54K, in Cx30, cosegregates with the phenotype. Unlike wild-type Cx30, p.N54K Cx30 is predominantly localized in the cytoplasm and does not permit transfer of neurobiotin, suggesting improper cellular localization and abolishment of gap-junction activity.
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Affiliation(s)
- Nishtha Pandey
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India.,Centre for Human Genetics, Bangalore, India
| | - Dennis F Xavier
- Department of Speech and Hearing, School of Allied Health Sciences, Manipal University, Manipal, India
| | - Arunima Chatterjee
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
| | - Ram-Shankar Mani
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
| | | | - Ajith Tharakan
- Department of Dermatology, Sree Narayana Institute of Medical Sciences, Cochin, India
| | - B Rajashekhar
- Department of Speech and Hearing, School of Allied Health Sciences, Manipal University, Manipal, India
| | - Anuranjan Anand
- Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
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29
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Yao F, Yue M, Zhang C, Zuo X, Zheng X, Zhang A, Wang Z, Liu S, Li H, Meng L, Zeng M, Fan X, Sun L, Zhang X. A genetic coding variant rs72474224 in GJB2 is associated with clinical features of psoriasis vulgaris in a Chinese Han population. ACTA ACUST UNITED AC 2015; 86:134-8. [PMID: 26104599 DOI: 10.1111/tan.12595] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 04/22/2015] [Accepted: 05/22/2015] [Indexed: 12/19/2022]
Abstract
Our recent targeted sequencing study identified a missense single-nucleotide polymorphism rs72474224 (c.324C>T) in GJB2. To investigate the correlation between rs72474224 (c.324C>T) and subphenotypes of psoriasis, genotype data for rs72474224 (c.324C>T, p.Val37Ile) was analyzed in 9946 cases and 9906 controls. The additive model provided the best fit for rs72474224 (P = 7.34 × 10(-9)). The genotypic and allelic frequency distributions were associated with plaque psoriasis in case-only (Pgenotype = 2.67 × 10(-3), Pallele = 6.22 × 10(-4)) and subphenotype-control (Pgenotype = 1.58 × 10(-11), Pallele = 8.16 × 10(-12)) analyses. No other significant difference was found in case-only analyses. Rs72474224 in GJB2 is preferentially associated with plaque psoriasis in Chinese population and might contribute to the complexity of psoriasis clinical features.
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Affiliation(s)
- F Yao
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China.,Department of Dermatology at Anqing Hospital, Anhui Medical University, Hefei, China
| | - M Yue
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - C Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zuo
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zheng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - A Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - Z Wang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - S Liu
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - H Li
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - L Meng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - M Zeng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Fan
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - L Sun
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
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30
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Canavan T, Tosti A, Mallory H, McKay K, Cantrell W, Elewski B. An Idiopathic Leukonychia Totalis and Leukonychia Partialis Case Report and Review of the Literature. Skin Appendage Disord 2015; 1:38-42. [PMID: 27172289 DOI: 10.1159/000380956] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 02/13/2015] [Indexed: 11/19/2022] Open
Abstract
Leukonychia totalis and leukonychia partialis are rare nail findings characterized by complete or partial whitening of the nail plate. Leukonychia totalis and leukonychia partialis are usually inherited or associated with systemic disease. Here, we report the case of a 25-year-old man with idiopathic acquired leukonychia totalis and leukonychia partialis and review the literature on this topic.
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Affiliation(s)
- Theresa Canavan
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, Ala., USA
| | - Antonella Tosti
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, Ala., USA
| | - Hurst Mallory
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, Ala., USA
| | - Kristopher McKay
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, Ala., USA
| | - Wendy Cantrell
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, Ala., USA
| | - Boni Elewski
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, Ala., USA
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31
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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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32
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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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33
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Berger AC, Kelly JJ, Lajoie P, Shao Q, Laird DW. Mutations in Cx30 that are linked to skin disease and non-syndromic hearing loss exhibit several distinct cellular pathologies. J Cell Sci 2014; 127:1751-64. [DOI: 10.1242/jcs.138230] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
ABSTRACT
Connexin 30 (Cx30), a member of the large gap-junction protein family, plays a role in the homeostasis of the epidermis and inner ear through gap junctional intercellular communication (GJIC). Here, we investigate the underlying mechanisms of four autosomal dominant Cx30 gene mutations that are linked to hearing loss and/or various skin diseases. First, the T5M mutant linked to non-syndromic hearing loss formed functional gap junction channels and hemichannels, similar to wild-type Cx30. The loss-of-function V37E mutant associated with Clouston syndrome or keratitis-ichthyosis-deafness syndrome was retained in the endoplasmic reticulum and significantly induced apoptosis. The G59R mutant linked to the Vohwinkel and Bart-Pumphrey syndromes was retained primarily in the Golgi apparatus and exhibited loss of gap junction channel and hemichannel function but did not cause cell death. Lastly, the A88V mutant, which is linked to the development of Clouston syndrome, also significantly induced apoptosis but through an endoplasmic-reticulum-independent mechanism. Collectively, we discovered that four unique Cx30 mutants might cause disease through different mechanisms that also likely include their selective trans-dominant effects on coexpressed connexins, highlighting the overall complexity of connexin-linked diseases and the importance of GJIC in disease prevention.
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Affiliation(s)
- Amy C. Berger
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - John J. Kelly
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Patrick Lajoie
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Qing Shao
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Dale W. Laird
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
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34
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Extracellular domains play different roles in gap junction formation and docking compatibility. Biochem J 2014; 458:1-10. [PMID: 24438327 DOI: 10.1042/bj20131162] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
GJ (gap junction) channels mediate direct intercellular communication and play an important role in many physiological processes. Six connexins oligomerize to form a hemichannel and two hemichannels dock together end-to-end to form a GJ channel. Connexin extracellular domains (E1 and E2) have been shown to be important for the docking, but the molecular mechanisms behind the docking and formation of GJ channels are not clear. Recent developments in atomic GJ structure and functional studies on a series of connexin mutants revealed that E1 and E2 are likely to play different roles in the docking. Non-covalent interactions at the docking interface, including hydrogen bonds, are predicted to form between interdocked extracellular domains. Protein sequence alignment analysis on the docking compatible/incompatible connexins indicate that the E1 domain is important for the formation of the GJ channel and the E2 domain is important in the docking compatibility in heterotypic channels. Interestingly, the hydrogen-bond forming or equivalent residues in both E1 and E2 domains are mutational hot spots for connexin-linked human diseases. Understanding the molecular mechanisms of GJ docking can assist us to develop novel strategies in rescuing the disease-linked connexin mutants.
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35
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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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36
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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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37
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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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38
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Vele O, Schrijver I. Inherited hearing loss: molecular genetics and diagnostic testing. ACTA ACUST UNITED AC 2013; 2:231-48. [PMID: 23495655 DOI: 10.1517/17530059.2.3.231] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Hearing loss is a clinically and genetically heterogeneous condition with major medical and social consequences. It affects up to 8% of the general population. OBJECTIVE This review recapitulates the principles of auditory physiology and the molecular basis of hearing loss, outlines the main types of non-syndromic and syndromic deafness by mode of inheritance, and provides an overview of current clinically available genetic testing. METHODS This paper reviews the literature on auditory physiology and on genes, associated with hearing loss, for which genetic testing is presently offered. RESULTS/CONCLUSION The advent of molecular diagnostic assays for hereditary hearing loss permits earlier detection of the underlying causes, facilitates appropriate interventions, and is expected to generate the data necessary for more specific genotype-phenotype correlations.
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Affiliation(s)
- Oana Vele
- Stanford University School of Medicine, Department of Pathology and Pediatrics, L235, 300 Pasteur Drive, Stanford, CA 94305, USA +1 650 724 2403 ; +1 650 724 1567 ;
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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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Ogawa A, Shimizu K, Yoshizaki A, Sato S, Kanda Y, Kumagami H, Takahashi H, Usami S. A case of palmoplantar lichen planus in a patient with congenital sensorineural deafness. Clin Exp Dermatol 2012; 38:30-2. [PMID: 22924538 DOI: 10.1111/j.1365-2230.2012.04374.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report a case of palmoplantar lichen planus in a 7-year-old Japanese girl with congenital deafness, who presented with erythematous eruptions and hyperkeratosis, with peeling and fissures on her soles, palms and digits. On histological examination of a skin biopsy from the lesion on her wrist, lichen planus was identified. Using computed tomography of the inner ears, bilateral cochlear dysplasia was found. The patient's DNA was sequenced; no sequence variants were detected in the GJB2 gene encoding connexin-26, but she had a missense mutation in SLC26A4 (solute carrier family 26, member 4). Mutations in SLC26A4 are known causes of hearing loss, but this is a novel mutation, which has not been reported previously. In addition, there have been no reports of cutaneous symptoms in previously reported patients with mutations in SLC26A4. To our knowledge, therefore, this is the first report of palmoplantar lichen planus associated with sensorineural deafness accompanied by a mutation in the SLC26A4 gene.
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Affiliation(s)
- A Ogawa
- Department of Dermatology, Nagasaki University Graduate School of Biomedical Sciences, Japan.
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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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Liu QP, Wu LS, Li FF, Liu S, Su J, Kuang YH, Chen C, Xie XY, Jiang MH, Zhao S, Chen ML, Chen X. The association between GJB2 gene polymorphism and psoriasis: a verification study. Arch Dermatol Res 2012; 304:769-72. [PMID: 22890607 DOI: 10.1007/s00403-012-1273-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 07/16/2012] [Accepted: 07/19/2012] [Indexed: 12/31/2022]
Abstract
Psoriasis is a chronic inflammatory skin disease with multifactorial etiology. Connexin 26 (Cx26), an important gap junction protein, has been found highly expressed in plaques of psoriasis. Recently, genome wide association studies (GWAS) identified one new single nucleotide polymorphism (SNP) in GJB2 gene coding for Cx26 protein associated with psoriasis in Chinese Han population. In this paper, we verified the GWAS data in Chinese Han population. Here we genotyped the polymorphism of GJB2 rs3751385:C>T in 371 psoriasis patients and 330 healthy controls in Chinese Han population using polymerase chain reaction restriction fragment length polymorphism assay (PCR-RFLP). Our case-control assay indicated decreased frequency of the GJB2 rs3751385 C allele in psoriasis patients compared with that in the healthy controls [p = 6.02 × 10(-5), Odds ratio (OR) = 0.793, 95 % confidence interval (CI) 0.706-0.889]. The result suggested that GJB2 gene polymorphism rs3751385:C>T was associated with psoriasis susceptibility of Chinese Han population.
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Affiliation(s)
- Que-Ping Liu
- Department of Dermatology, Xiang-Ya Hospital Central South University, Changsha, Hunan, People's Republic of China
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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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Xu J, Nicholson BJ. The role of connexins in ear and skin physiology - functional insights from disease-associated mutations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:167-78. [PMID: 22796187 DOI: 10.1016/j.bbamem.2012.06.024] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Revised: 06/23/2012] [Accepted: 06/29/2012] [Indexed: 12/20/2022]
Abstract
Defects in several different connexins have been associated with several different diseases. The most common of these is deafness, where a few mutations in connexin (Cx) 26 have been found to contribute to over 50% of the incidence of non-syndromic deafness in different human populations. Other mutations in Cx26 or Cx30 have also been associated with various skin phenotypes linked to deafness (palmoplanta keratoderma, Bart-Pumphrey syndrome, Vohwinkel syndrome, keratitis-ichthyosis-deafness syndrome, etc.). The large array of disease mutants offers unique opportunities to gain insights into the underlying function of gap junction proteins and their channels in the normal and pathogenic physiologies of the cochlea and epidermis. This review focuses on those mutants where the impact on channel function has been assessed, and correlated with the disease phenotype, or organ function in knock-out mouse models. These approaches have provided evidence supporting a role of gap junctions and hemichannels in K(+) removal and recycling in the ear, as well as possible roles for nutrient passage, in the cochlea. In contrast, increases in hemichannel opening leading to increased cell death, were associated with several keratitis-ichthyosis-deafness syndrome skin disease/hearing mutants. In addition to providing clues for therapeutic strategies, these findings allow us to better understand the specific functions of connexin channels that are important for normal tissue function. This article is part of a Special Issue entitled: The communicating junctions, roles and dysfunctions.
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Affiliation(s)
- Ji Xu
- Department of Physiology, University of California, Los Angeles, CA 90095, USA
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Petersen MB, Grigoriadou M, Koutroumpe M, Kokotas H. The novel c.247_249delTTC (p.F83del) GJB2 mutation in a family with prelingual sensorineural deafness. Int J Pediatr Otorhinolaryngol 2012; 76:969-71. [PMID: 22484064 DOI: 10.1016/j.ijporl.2012.03.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2012] [Revised: 03/06/2012] [Accepted: 03/10/2012] [Indexed: 11/29/2022]
Abstract
Non-syndromic hearing loss is one of the most common hereditary determined diseases in human, and the disease is a genetically heterogeneous disorder. Mutations in the GJB2 gene, encoding connexin 26 (Cx26), are a major cause of non-syndromic recessive hearing impairment in many countries and are largely dependent on ethnic groups. Due to the high frequency of the c.35delG GJB2 mutation in the Greek population, we have previously suggested that Greek patients with sensorineural, non-syndromic deafness should be tested for the c.35delG mutation and the coding region of the GJB2 gene should be sequenced in c.35delG heterozygotes. Here we present on the clinical and molecular genetic evaluation of a family suffering from prelingual, sensorineural, non-syndromic deafness. A novel c.247_249delTTC (p.F83del) GJB2 mutation was detected in compound heterozygosity with the c.35delG GJB2 mutation in the proband and was later confirmed in the father, while the mother was homozygous for the c.35delG GJB2 mutation. We conclude that compound heterozygosity of the novel c.247_249delTTC (p.F83del) and the c.35delG mutations in the GJB2 gene was the cause of deafness in the proband and his father.
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Affiliation(s)
- Michael B Petersen
- Department of Genetics, Institute of Child Health, Aghia Sophia Children's Hospital, Athens 11527, Greece
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Petersen MB, Grigoriadou M, Economides J, Kokotas H. Compound heterozygosity of the novel c.292C>T (p.R98W) and the c.35delG GJB2 mutations in postlingual, non-syndromic, sensorineural deafness. Int J Pediatr Otorhinolaryngol 2012; 76:549-51. [PMID: 22321824 DOI: 10.1016/j.ijporl.2012.01.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 01/11/2012] [Accepted: 01/13/2012] [Indexed: 11/18/2022]
Abstract
OBJECTIVES Connexins (Cxs) are membrane-spanning proteins that co-assemble into intercellular gap junction channels. Gap junction channels mediate electrical and biochemical communication between adjacent cells and play vital roles as mediators of intercellular molecular signaling. Cx-linked deafness highlights the key role of gap junctions in the physiological processes of hearing. Co-localization of Cxs with the gap junction system in the inner ear suggests a role in cochlear electrolyte homeostasis. During auditory transduction, they are proposed to maintain membrane potentials by regulating the flow of potassium ions between the sensory epithelia of the inner ear. METHODS Clinical and molecular genetic methods were employed in a Greek proband presenting with bilateral, postlingual, non-syndromic, sensorineural deafness. RESULTS We detected a novel c.292C>T (p.R98W) mutation in compound heterozygosity with the c.35delG mutation in the GJB2 gene. CONCLUSION Although mutations in the GJB2 gene usually cause prelingual, severe to profound deafness, compound heterozygosity of the novel c.292C>T (p.R98W) and the c.35delG GJB2 mutations appears to be the cause of postlingual, moderate, sensorineural deafness in our proband.
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Affiliation(s)
- Michael B Petersen
- Department of Genetics, Institute of Child Health, Aghia Sophia Children's Hospital, Athens, Greece
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Mese G, Sellitto C, Li L, Wang HZ, Valiunas V, Richard G, Brink PR, White TW. The Cx26-G45E mutation displays increased hemichannel activity in a mouse model of the lethal form of keratitis-ichthyosis-deafness syndrome. Mol Biol Cell 2011; 22:4776-86. [PMID: 22031297 PMCID: PMC3237621 DOI: 10.1091/mbc.e11-09-0778] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Mutations in the GJB2 gene (Cx26) cause deafness in humans. Most are loss-of-function mutations and cause nonsyndromic deafness. Some mutations produce a gain of function and cause syndromic deafness associated with skin disorders, such as keratitis-ichthyosis-deafness syndrome (KIDS). Cx26-G45E is a lethal mutation linked to KIDS that forms constitutively active connexin hemichannels. The pathomechanism(s) by which mutant Cx26 hemichannels perturb normal epidermal cornification are poorly understood. We created an animal model for KIDS by generating an inducible transgenic mouse expressing Cx26-G45E in keratinocytes. Cx26-G45E mice displayed reduced viability, hyperkeratosis, scaling, skin folds, and hair loss. Histopathology included hyperplasia, acanthosis, papillomatosis, increased cell size, and osteal plugging. These abnormalities correlated with human KIDS pathology and were associated with increased hemichannel currents in transgenic keratinocytes. These results confirm the pathogenic nature of the G45E mutation and provide a new model for studying the role of aberrant connexin hemichannels in epidermal differentiation and inherited connexin disorders.
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Affiliation(s)
- Gulistan Mese
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794, USA
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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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Chang EH, Pezzulo AA, Zabner J. Do cell junction protein mutations cause an airway phenotype in mice or humans? Am J Respir Cell Mol Biol 2011; 45:202-20. [PMID: 21297078 DOI: 10.1165/rcmb.2010-0498tr] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Cell junction proteins connect epithelial cells to each other and to the basement membrane. Genetic mutations of these proteins can cause alterations in some epithelia leading to varied phenotypes such as deafness, renal disease, skin disorders, and cancer. This review examines if genetic mutations in these proteins affect the function of lung airway epithelia. We review cell junction proteins with examples of disease mutation phenotypes in humans and in mouse knockout models. We also review which of these genes are expressed in airway epithelium by microarray expression profiling and immunocytochemistry. Last, we present a comprehensive literature review to find the lung phenotype when cell junction and adhesion genes are mutated or subject to targeted deletion. We found that in murine models, targeted deletion of cell junction and adhesion genes rarely result in a lung phenotype. Moreover, mutations in these genes in humans have no obvious lung phenotype. Our research suggests that simply because a cell junction or adhesion protein is expressed in an organ does not imply that it will exhibit a drastic phenotype when mutated. One explanation is that because a functioning lung is critical to survival, redundancy in the system is expected. Therefore mutations in a single gene might be compensated by a related function of a similar gene product. Further studies in human and animal models will help us understand the overlap in the function of cell junction gene products. Finally, it is possible that the human lung phenotype is subtle and has not yet been described.
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Affiliation(s)
- Eugene H Chang
- Department of Otolaryngology–Head and Neck Surgery, University of Iowa Hospitals and Clinics, Iowa City, USA
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Abstract
BACKGROUND Connexins are a family of transmembrane proteins that are widely expressed in the human body. Connexins play an important role in cell-cell communication and homeostasis in various tissues by forming gap junction channels, which enable a direct passage of ions or metabolites from one cell to another. Twenty-one different connexins are expressed in humans, each having distinct expression patterns and regulation properties. Knowledge on this family of proteins can be gained by making an inventory of mutations and associated diseases in human. DESIGN PubMed and other relevant databases were searched. In addition, key review articles were screened for relevant original publications. Sections of representative organs were photographed and annotated. RESULTS The crucial role of connexins is highlighted by the discovery of mutations in connexin genes which cause a variety of disorders such as myelin-related diseases, skin disorders, hearing loss, congenital cataract, or more complex syndromes such as the oculodendrodigital dysplasia. This review systematically addresses current knowledge on mutations in connexin genes and disease, focusing on the correlation between genetic defects, cellular phenotypes and clinical manifestations. CONCLUSIONS The review of diseases caused by mutations in connexin genes highlights the essential nature of connexin function and intercellular communication in tissue homeostasis.
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Affiliation(s)
- Anna Pfenniger
- Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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