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Posukh OL, Maslova EA, Danilchenko VY, Zytsar MV, Orishchenko KE. Functional Consequences of Pathogenic Variants of the GJB2 Gene (Cx26) Localized in Different Cx26 Domains. Biomolecules 2023; 13:1521. [PMID: 37892203 PMCID: PMC10604905 DOI: 10.3390/biom13101521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/08/2023] [Accepted: 10/10/2023] [Indexed: 10/29/2023] Open
Abstract
One of the most common forms of genetic deafness has been predominantly associated with pathogenic variants in the GJB2 gene, encoding transmembrane protein connexin 26 (Cx26). The Cx26 molecule consists of an N-terminal domain (NT), four transmembrane domains (TM1-TM4), two extracellular loops (EL1 and EL2), a cytoplasmic loop, and a C-terminus (CT). Pathogenic variants in the GJB2 gene, resulting in amino acid substitutions scattered across the Cx26 domains, lead to a variety of clinical outcomes, including the most common non-syndromic autosomal recessive deafness (DFNB1A), autosomal dominant deafness (DFNA3A), as well as syndromic forms combining hearing loss and skin disorders. However, for rare and poorly documented variants, information on the mode of inheritance is often lacking. Numerous in vitro studies have been conducted to elucidate the functional consequences of pathogenic GJB2 variants leading to amino acid substitutions in different domains of Cx26 protein. In this work, we summarized all available data on a mode of inheritance of pathogenic GJB2 variants leading to amino acid substitutions and reviewed published information on their functional effects, with an emphasis on their localization in certain Cx26 domains.
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Affiliation(s)
- Olga L. Posukh
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Ekaterina A. Maslova
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Valeriia Yu. Danilchenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Marina V. Zytsar
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
| | - Konstantin E. Orishchenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
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Aboagye ET, Adadey SM, Wonkam-Tingang E, Amenga-Etego L, Awandare GA, Wonkam A. Global Distribution of Founder Variants Associated with Non-Syndromic Hearing Impairment. Genes (Basel) 2023; 14:399. [PMID: 36833326 PMCID: PMC9957346 DOI: 10.3390/genes14020399] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 01/28/2023] [Accepted: 01/30/2023] [Indexed: 02/05/2023] Open
Abstract
The genetic etiology of non-syndromic hearing impairment (NSHI) is highly heterogeneous with over 124 distinct genes identified. The wide spectrum of implicated genes has challenged the implementation of molecular diagnosis with equal clinical validity in all settings. Differential frequencies of allelic variants in the most common NSHI causal gene, gap junction beta 2 (GJB2), has been described as stemming from the segregation of a founder variant and/or spontaneous germline variant hot spots. We aimed to systematically review the global distribution and provenance of founder variants associated with NSHI. The study protocol was registered on PROSPERO, the International Prospective Register of Systematic Reviews, with the registration number "CRD42020198573". Data from 52 reports, involving 27,959 study participants from 24 countries, reporting 56 founder pathogenic or likely pathogenic (P/LP) variants in 14 genes (GJB2, GJB6, GSDME, TMC1, TMIE, TMPRSS3, KCNQ4, PJVK, OTOF, EYA4, MYO15A, PDZD7, CLDN14, and CDH23), were reviewed. Varied number short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs) were used for haplotype analysis to identify the shared ancestral informative markers in a linkage disequilibrium and variants' origins, age estimates, and common ancestry computations in the reviewed reports. Asia recorded the highest number of NSHI founder variants (85.7%; 48/56), with variants in all 14 genes, followed by Europe (16.1%; 9/56). GJB2 had the highest number of ethnic-specific P/LP founder variants. This review reports on the global distribution of NSHI founder variants and relates their evolution to population migration history, bottleneck events, and demographic changes in populations linked with the early evolution of deleterious founder alleles. International migration and regional and cultural intermarriage, coupled to rapid population growth, may have contributed to re-shaping the genetic architecture and structural dynamics of populations segregating these pathogenic founder variants. We have highlighted and showed the paucity of data on hearing impairment (HI) variants in Africa, establishing unexplored opportunities in genetic traits.
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Affiliation(s)
- Elvis Twumasi Aboagye
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra LG Box 54, Ghana
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa
| | - Samuel Mawuli Adadey
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra LG Box 54, Ghana
| | - Edmond Wonkam-Tingang
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa
| | - Lucas Amenga-Etego
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra LG Box 54, Ghana
| | - Gordon A. Awandare
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra LG Box 54, Ghana
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa
- McKusick-Nathans Institute and Department of Genetic Medicine, John Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Connexin Mutations and Hereditary Diseases. Int J Mol Sci 2022; 23:ijms23084255. [PMID: 35457072 PMCID: PMC9027513 DOI: 10.3390/ijms23084255] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 04/04/2022] [Accepted: 04/09/2022] [Indexed: 02/01/2023] Open
Abstract
Inherited diseases caused by connexin mutations are found in multiple organs and include hereditary deafness, congenital cataract, congenital heart diseases, hereditary skin diseases, and X-linked Charcot–Marie–Tooth disease (CMT1X). A large number of knockout and knock-in animal models have been used to study the pathology and pathogenesis of diseases of different organs. Because the structures of different connexins are highly homologous and the functions of gap junctions formed by these connexins are similar, connexin-related hereditary diseases may share the same pathogenic mechanism. Here, we analyze the similarities and differences of the pathology and pathogenesis in animal models and find that connexin mutations in gap junction genes expressed in the ear, eye, heart, skin, and peripheral nerves can affect cellular proliferation and differentiation of corresponding organs. Additionally, some dominant mutations (e.g., Cx43 p.Gly60Ser, Cx32 p.Arg75Trp, Cx32 p.Asn175Asp, and Cx32 p.Arg142Trp) are identified as gain-of-function variants in vivo, which may play a vital role in the onset of dominant inherited diseases. Specifically, patients with these dominant mutations receive no benefits from gene therapy. Finally, the complete loss of gap junctional function or altered channel function including permeability (ions, adenosine triphosphate (ATP), Inositol 1,4,5-trisphosphate (IP3), Ca2+, glucose, miRNA) and electric activity are also identified in vivo or in vitro.
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Zadeh Shirazi A, McDonnell MD, Fornaciari E, Bagherian NS, Scheer KG, Samuel MS, Yaghoobi M, Ormsby RJ, Poonnoose S, Tumes DJ, Gomez GA. A deep convolutional neural network for segmentation of whole-slide pathology images identifies novel tumour cell-perivascular niche interactions that are associated with poor survival in glioblastoma. Br J Cancer 2021; 125:337-350. [PMID: 33927352 PMCID: PMC8329064 DOI: 10.1038/s41416-021-01394-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 03/16/2021] [Accepted: 04/08/2021] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Glioblastoma is the most aggressive type of brain cancer with high-levels of intra- and inter-tumour heterogeneity that contribute to its rapid growth and invasion within the brain. However, a spatial characterisation of gene signatures and the cell types expressing these in different tumour locations is still lacking. METHODS We have used a deep convolutional neural network (DCNN) as a semantic segmentation model to segment seven different tumour regions including leading edge (LE), infiltrating tumour (IT), cellular tumour (CT), cellular tumour microvascular proliferation (CTmvp), cellular tumour pseudopalisading region around necrosis (CTpan), cellular tumour perinecrotic zones (CTpnz) and cellular tumour necrosis (CTne) in digitised glioblastoma histopathological slides from The Cancer Genome Atlas (TCGA). Correlation analysis between segmentation results from tumour images together with matched RNA expression data was performed to identify genetic signatures that are specific to different tumour regions. RESULTS We found that spatially resolved gene signatures were strongly correlated with survival in patients with defined genetic mutations. Further in silico cell ontology analysis along with single-cell RNA sequencing data from resected glioblastoma tissue samples showed that these tumour regions had different gene signatures, whose expression was driven by different cell types in the regional tumour microenvironment. Our results further pointed to a key role for interactions between microglia/pericytes/monocytes and tumour cells that occur in the IT and CTmvp regions, which may contribute to poor patient survival. CONCLUSIONS This work identified key histopathological features that correlate with patient survival and detected spatially associated genetic signatures that contribute to tumour-stroma interactions and which should be investigated as new targets in glioblastoma. The source codes and datasets used are available in GitHub: https://github.com/amin20/GBM_WSSM .
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Affiliation(s)
- Amin Zadeh Shirazi
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA, Australia
- Computational Learning Systems Laboratory, UniSA STEM, University of South Australia, Mawson Lakes, SA, Australia
| | - Mark D McDonnell
- Computational Learning Systems Laboratory, UniSA STEM, University of South Australia, Mawson Lakes, SA, Australia
| | - Eric Fornaciari
- Department of Mathematics of Computation, University of California, Los Angeles (UCLA), CA, USA
| | | | - Kaitlin G Scheer
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA, Australia
| | - Michael S Samuel
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA, Australia
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Mahdi Yaghoobi
- Electrical and Computer Engineering Department, Department of Artificial Intelligence, Islamic Azad University, Mashhad Branch, Mashhad, Iran
| | - Rebecca J Ormsby
- Flinders Health and Medical Research Institute, College of Medicine & Public Health, Flinders University, Adelaide, SA, Australia
| | - Santosh Poonnoose
- Flinders Health and Medical Research Institute, College of Medicine & Public Health, Flinders University, Adelaide, SA, Australia
- Department of Neurosurgery, Flinders Medical Centre, Bedford Park, SA, Australia
| | - Damon J Tumes
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA, Australia
| | - Guillermo A Gomez
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA, Australia.
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Ilyaskin AV, Korbmacher C, Diakov A. Inhibition of the epithelial sodium channel (ENaC) by connexin 30 involves stimulation of clathrin-mediated endocytosis. J Biol Chem 2021; 296:100404. [PMID: 33577799 PMCID: PMC7973139 DOI: 10.1016/j.jbc.2021.100404] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 02/05/2021] [Accepted: 02/08/2021] [Indexed: 01/16/2023] Open
Abstract
Mice lacking connexin 30 (Cx30) display increased epithelial sodium channel (ENaC) activity in the distal nephron and develop salt-sensitive hypertension. This indicates a functional link between Cx30 and ENaC, which remains incompletely understood. Here, we explore the effect of Cx30 on ENaC function using the Xenopus laevis oocyte expression system. Coexpression of human Cx30 with human αβγENaC significantly reduced ENaC-mediated whole-cell currents. The size of the inhibitory effect on ENaC depended on the expression level of Cx30 and required Cx30 ion channel activity. ENaC inhibition by Cx30 was mainly due to reduced cell surface ENaC expression resulting from enhanced ENaC retrieval without discernible effects on proteolytic channel activation and single-channel properties. ENaC retrieval from the cell surface involves the interaction of the ubiquitin ligase Nedd4-2 with PPPxY-motifs in the C-termini of ENaC. Truncating the C- termini of β- or γENaC significantly reduced the inhibitory effect of Cx30 on ENaC. In contrast, mutating the prolines belonging to the PPPxY-motif in γENaC or coexpressing a dominant-negative Xenopus Nedd4 (xNedd4-CS) did not significantly alter ENaC inhibition by Cx30. Importantly, the inhibitory effect of Cx30 on ENaC was significantly reduced by Pitstop-2, an inhibitor of clathrin-mediated endocytosis, or by mutating putative clathrin adaptor protein 2 (AP-2) recognition motifs (YxxФ) in the C termini of β- or γ-ENaC. In conclusion, our findings suggest that Cx30 inhibits ENaC by promoting channel retrieval from the plasma membrane via clathrin-dependent endocytosis. Lack of this inhibition may contribute to increased ENaC activity and salt-sensitive hypertension in mice with Cx30 deficiency.
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Affiliation(s)
- Alexandr V Ilyaskin
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Christoph Korbmacher
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Alexei Diakov
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
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Maslova EA, Orishchenko KE, Posukh OL. Functional Evaluation of a Rare Variant c.516G>C (p.Trp172Cys) in the GJB2 (Connexin 26) Gene Associated with Nonsyndromic Hearing Loss. Biomolecules 2021; 11:61. [PMID: 33466560 PMCID: PMC7824951 DOI: 10.3390/biom11010061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 01/03/2021] [Accepted: 01/04/2021] [Indexed: 01/05/2023] Open
Abstract
Mutations in the GJB2 gene encoding transmembrane protein connexin 26 (Cx26) are the most common cause for hearing loss worldwide. Cx26 plays a crucial role in the ionic and metabolic homeostasis in the inner ear, indispensable for normal hearing process. Different pathogenic mutations in the GJB2 gene can affect all stages of the Cx26 life cycle and result in nonsyndromic autosomal recessive (DFNB1) or dominant (DFNA3) deafness and syndromes associating hearing loss with skin disorders. This study aims to elucidate the functional consequences of a rare GJB2 variant c.516G>C (p.Trp172Cys) found with high frequency in deaf patients from indigenous populations of Southern Siberia (Russia). The substitution c.516G>C leads to the replacement of tryptophan at a conserved amino acid position 172 with cysteine (p.Trp172Cys) in the second extracellular loop of Cx26 protein. We analyzed the subcellular localization of mutant Cx26-p.Trp172Cys protein by immunocytochemistry and the hemichannels permeability by dye loading assay. The GJB2 knockout HeLa cell line has been generated using CRISPR/Cas9 genome editing tool. Subsequently, the HeLa transgenic cell lines stably expressing different GJB2 variants (wild type and mutations associated with hearing loss) were established based on knockout cells and used for comparative functional analysis. The impaired trafficking of mutant Cx26-p.Trp172Cys protein to the plasma membrane and reduced hemichannels permeability support the pathogenic effect of the c.516G>C (p.Trp172Cys) variant and its association with nonsyndromic hearing loss. Our data contribute to a better understanding of the role of mutations in the second extracellular loop of Cx26 protein in pathogenesis of deafness.
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Affiliation(s)
- Ekaterina A. Maslova
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia; (E.A.M.); (K.E.O.)
- Novosibirsk State University, Novosibirsk 630090, Russia
| | - Konstantin E. Orishchenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia; (E.A.M.); (K.E.O.)
- Novosibirsk State University, Novosibirsk 630090, Russia
| | - Olga L. Posukh
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia; (E.A.M.); (K.E.O.)
- Novosibirsk State University, Novosibirsk 630090, Russia
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Kanavy DM, McNulty SM, Jairath MK, Brnich SE, Bizon C, Powell BC, Berg JS. Comparative analysis of functional assay evidence use by ClinGen Variant Curation Expert Panels. Genome Med 2019; 11:77. [PMID: 31783775 PMCID: PMC6884856 DOI: 10.1186/s13073-019-0683-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 11/05/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The 2015 American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) guidelines for clinical sequence variant interpretation state that "well-established" functional studies can be used as evidence in variant classification. These guidelines articulated key attributes of functional data, including that assays should reflect the biological environment and be analytically sound; however, details of how to evaluate these attributes were left to expert judgment. The Clinical Genome Resource (ClinGen) designates Variant Curation Expert Panels (VCEPs) in specific disease areas to make gene-centric specifications to the ACMG/AMP guidelines, including more specific definitions of appropriate functional assays. We set out to evaluate the existing VCEP guidelines for functional assays. METHODS We evaluated the functional criteria (PS3/BS3) of six VCEPs (CDH1, Hearing Loss, Inherited Cardiomyopathy-MYH7, PAH, PTEN, RASopathy). We then established criteria for evaluating functional studies based on disease mechanism, general class of assay, and the characteristics of specific assay instances described in the primary literature. Using these criteria, we extensively curated assay instances cited by each VCEP in their pilot variant classification to analyze VCEP recommendations and their use in the interpretation of functional studies. RESULTS Unsurprisingly, our analysis highlighted the breadth of VCEP-approved assays, reflecting the diversity of disease mechanisms among VCEPs. We also noted substantial variability between VCEPs in the method used to select these assays and in the approach used to specify strength modifications, as well as differences in suggested validation parameters. Importantly, we observed discrepancies between the parameters VCEPs specified as required for approved assay instances and the fulfillment of these requirements in the individual assays cited in pilot variant interpretation. CONCLUSIONS Interpretation of the intricacies of functional assays often requires expert-level knowledge of the gene and disease, and current VCEP recommendations for functional assay evidence are a useful tool to improve the accessibility of functional data by providing a starting point for curators to identify approved functional assays and key metrics. However, our analysis suggests that further guidance is needed to standardize this process and ensure consistency in the application of functional evidence.
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Affiliation(s)
- Dona M Kanavy
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Shannon M McNulty
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Meera K Jairath
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Sarah E Brnich
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Chris Bizon
- Renaissance Computing Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Bradford C Powell
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Jonathan S Berg
- Department of Genetics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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Shen J, Oza AM, Del Castillo I, Duzkale H, Matsunaga T, Pandya A, Kang HP, Mar-Heyming R, Guha S, Moyer K, Lo C, Kenna M, Alexander JJ, Zhang Y, Hirsch Y, Luo M, Cao Y, Wai Choy K, Cheng YF, Avraham KB, Hu X, Garrido G, Moreno-Pelayo MA, Greinwald J, Zhang K, Zeng Y, Brownstein Z, Basel-Salmon L, Davidov B, Frydman M, Weiden T, Nagan N, Willis A, Hemphill SE, Grant AR, Siegert RK, DiStefano MT, Amr SS, Rehm HL, Abou Tayoun AN. Consensus interpretation of the p.Met34Thr and p.Val37Ile variants in GJB2 by the ClinGen Hearing Loss Expert Panel. Genet Med 2019; 21:2442-2452. [PMID: 31160754 PMCID: PMC7235630 DOI: 10.1038/s41436-019-0535-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 04/24/2019] [Indexed: 12/02/2022] Open
Abstract
PURPOSE Pathogenic variants in GJB2 are the most common cause of autosomal recessive sensorineural hearing loss. The classification of c.101T>C/p.Met34Thr and c.109G>A/p.Val37Ile in GJB2 are controversial. Therefore, an expert consensus is required for the interpretation of these two variants. METHODS The ClinGen Hearing Loss Expert Panel collected published data and shared unpublished information from contributing laboratories and clinics regarding the two variants. Functional, computational, allelic, and segregation data were also obtained. Case-control statistical analyses were performed. RESULTS The panel reviewed the synthesized information, and classified the p.Met34Thr and p.Val37Ile variants utilizing professional variant interpretation guidelines and professional judgment. We found that p.Met34Thr and p.Val37Ile are significantly overrepresented in hearing loss patients, compared with population controls. Individuals homozygous or compound heterozygous for p.Met34Thr or p.Val37Ile typically manifest mild to moderate hearing loss. Several other types of evidence also support pathogenic roles for these two variants. CONCLUSION Resolving controversies in variant classification requires coordinated effort among a panel of international multi-institutional experts to share data, standardize classification guidelines, review evidence, and reach a consensus. We concluded that p.Met34Thr and p.Val37Ile variants in GJB2 are pathogenic for autosomal recessive nonsyndromic hearing loss with variable expressivity and incomplete penetrance.
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Affiliation(s)
- Jun Shen
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
- Harvard Medical School Center for Hereditary Deafness, Boston, MA, USA.
- Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, MA, USA.
| | - Andrea M Oza
- Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, MA, USA
- Department of Otolaryngology and Communication Enhancement, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Ignacio Del Castillo
- Servicio de Genetica, Hospital Universitario Ramon y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Hatice Duzkale
- Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Tatsuo Matsunaga
- Division of Hearing and Balance Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Arti Pandya
- University of North Carolina, Chapel Hill, NC, USA
| | | | | | - Saurav Guha
- Counsyl, South San Francisco, CA, USA
- New York Genome Center, New York, NY, 10013, USA
| | | | | | - Margaret Kenna
- Harvard Medical School Center for Hereditary Deafness, Boston, MA, USA
- Department of Otolaryngology and Communication Enhancement, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - John J Alexander
- EGL Genetics/Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
- ConsulGene, LLC, Jacksonville, FL, USA
| | - Yan Zhang
- Certer for Medical Genetics, Guangdong Women and Children Hospital, Guangzhou, Guangdong, China
| | - Yoel Hirsch
- Dor Yeshorim, Committee for Prevention of Jewish Genetic Diseases, Brooklyn, NY, USA
| | - Minjie Luo
- The Children's Hospital of Philadelphia, Philadelphia, PA, USA
- The University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Ye Cao
- Department of Obstetrics and Gynecology, The Chinese University of Hong Kong, Hong Kong, China
| | - Kwong Wai Choy
- Department of Obstetrics and Gynecology, The Chinese University of Hong Kong, Hong Kong, China
| | - Yen-Fu Cheng
- Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan
- Department of Otolaryngology-Head and Neck Surgery, Taipei Veterinary Hospital, Taipei, Taiwan
- School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Karen B Avraham
- Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Petach Tikva, Israel
| | - Xinhua Hu
- Department of Biostatistics, Fairbanks School of Public Health and School of Medicine, Indiana University, Indianapolis, IN, USA
| | - Gema Garrido
- Servicio de Genetica, Hospital Universitario Ramon y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Miguel A Moreno-Pelayo
- Servicio de Genetica, Hospital Universitario Ramon y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - John Greinwald
- Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Kejian Zhang
- Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Yukun Zeng
- Certer for Medical Genetics, Guangdong Women and Children Hospital, Guangzhou, Guangdong, China
| | - Zippora Brownstein
- Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Petach Tikva, Israel
| | - Lina Basel-Salmon
- Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Petach Tikva, Israel
- Pediatric Genetics Clinic, Schneider Children's Medical Center of Israel, Petach Tikva, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Felsenstein Medical Research Center, Petach Tikva, Israel
| | - Bella Davidov
- Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Petach Tikva, Israel
| | - Moshe Frydman
- Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Petach Tikva, Israel
- Danek Gartner Institute of Human Genetics, Sheba Medical Center, Tel Hashomer, Israel
| | - Tzvi Weiden
- Dor Yeshorim, Committee for Prevention of Jewish Genetic Diseases, Jerusalem, Israel
| | - Narasimhan Nagan
- Integrated Genetics, Laboratory Corporation of America® Holdings, Westborough, MA, USA
| | - Alecia Willis
- Integrated Genetics, Laboratory Corporation of America® Holdings, Research Triangle Park, NC, USA
| | - Sarah E Hemphill
- Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, MA, USA
| | - Andrew R Grant
- Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, MA, USA
- The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Rebecca K Siegert
- Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, MA, USA
- The Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Marina T DiStefano
- Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, MA, USA
| | - Sami S Amr
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
- Harvard Medical School Center for Hereditary Deafness, Boston, MA, USA
- Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, MA, USA
| | - Heidi L Rehm
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
- Harvard Medical School Center for Hereditary Deafness, Boston, MA, USA
- Laboratory for Molecular Medicine, Partners HealthCare Personalized Medicine, Cambridge, MA, USA
- The Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
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9
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Oza AM, DiStefano MT, Hemphill SE, Cushman BJ, Grant AR, Siegert RK, Shen J, Chapin A, Boczek NJ, Schimmenti LA, Murry JB, Hasadsri L, Nara K, Kenna M, Booth KT, Azaiez H, Griffith A, Avraham KB, Kremer H, Rehm HL, Amr SS, Abou Tayoun AN. Expert specification of the ACMG/AMP variant interpretation guidelines for genetic hearing loss. Hum Mutat 2019; 39:1593-1613. [PMID: 30311386 DOI: 10.1002/humu.23630] [Citation(s) in RCA: 285] [Impact Index Per Article: 57.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 07/23/2018] [Accepted: 08/25/2018] [Indexed: 12/23/2022]
Abstract
Due to the high genetic heterogeneity of hearing loss (HL), current clinical testing includes sequencing large numbers of genes, which often yields a significant number of novel variants. Therefore, the standardization of variant interpretation is crucial to provide consistent and accurate diagnoses. The Hearing Loss Variant Curation Expert Panel was created within the Clinical Genome Resource to provide expert guidance for standardized genomic interpretation in the context of HL. As one of its major tasks, our Expert Panel has adapted the American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines for the interpretation of sequence variants in HL genes. Here, we provide a comprehensive illustration of the newly specified ACMG/AMP HL rules. Three rules remained unchanged, four rules were removed, and the remaining 21 rules were specified. These rules were further validated and refined using a pilot set of 51 variants assessed by curators and disease experts. Of the 51 variants evaluated in the pilot, 37% (19/51) changed category based upon application of the expert panel specified rules and/or aggregation of evidence across laboratories. These HL-specific ACMG/AMP rules will help standardize variant interpretation, ultimately leading to better care for individuals with HL.
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Affiliation(s)
- Andrea M Oza
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Department of Otolaryngology and Communication Enhancement, Boston Children's Hospital, Boston, Massachusetts
| | - Marina T DiStefano
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - Sarah E Hemphill
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Brandon J Cushman
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Andrew R Grant
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Rebecca K Siegert
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Jun Shen
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Department of Pathology, Brigham & Women's Hospital, Boston, Massachusetts
| | | | - Nicole J Boczek
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Lisa A Schimmenti
- Department of Otorhinolaryngology, Clinical Genomics and Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota
| | - Jaclyn B Murry
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts
| | - Linda Hasadsri
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Kiyomitsu Nara
- Division of Hearing and Balance Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Margaret Kenna
- Department of Otolaryngology and Communication Enhancement, Boston Children's Hospital, Boston, Massachusetts.,Harvard Medical School, Boston, Massachusetts
| | - Kevin T Booth
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology, University of Iowa Hospital and Clinics, Iowa City, Iowa.,The Interdisciplinary Graduate Program in Molecular Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Hela Azaiez
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology, University of Iowa Hospital and Clinics, Iowa City, Iowa
| | - Andrew Griffith
- Audiology Unit, National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland
| | - Karen B Avraham
- Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Hannie Kremer
- Department of Otorhinolaryngology and Department of Human Genetics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Heidi L Rehm
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Center for Genomic Medicine, Massachusetts General Hospital, Boston, Massachusetts.,The Broad Institute of MIT and Harvard, Cambridge, Massachusetts
| | - Sami S Amr
- Laboratory for Molecular Medicine, Partners Healthcare Personalized Medicine, Cambridge, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Department of Pathology, Brigham & Women's Hospital, Boston, Massachusetts
| | - Ahmad N Abou Tayoun
- The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,The University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
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10
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Gallego-Martinez A, Requena T, Roman-Naranjo P, Lopez-Escamez JA. Excess of Rare Missense Variants in Hearing Loss Genes in Sporadic Meniere Disease. Front Genet 2019; 10:76. [PMID: 30828346 PMCID: PMC6385525 DOI: 10.3389/fgene.2019.00076] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 01/28/2019] [Indexed: 12/25/2022] Open
Abstract
Meniere's disease (MD) is a clinical spectrum of rare disorders characterized by vertigo attacks, associated with sensorineural hearing loss (SNHL) and tinnitus involving low to medium frequencies. Although it shows familial aggregation with incomplete phenotypic forms and variable expressivity, most cases are considered sporadic. The aim of this study was to investigate the burden for rare variation in SNHL genes in patients with sporadic MD. We conducted a targeted-sequencing study including SNHL and familial MD genes in 890 MD patients to compare the frequency of rare variants in cases using three independent public datasets as controls. Patients with sporadic MD showed a significant enrichment of missense variants in SNHL genes that was not found in the controls. The list of genes includes GJB2, USH1G, SLC26A4, ESRRB, and CLDN14. A rare synonymous variant with unknown significance was found in the MARVELD2 gene in several unrelated patients with MD. There is a burden of rare variation in certain SNHL genes in sporadic MD. Furthermore, the interaction of common and rare variants in SNHL genes may have an additive effect on MD phenotype. This study will contribute to design a gene panel for the genetic diagnosis of MD.
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Affiliation(s)
- Alvaro Gallego-Martinez
- Otology and Neurotology Group CTS 495, Department of Genomic Medicine, Centre for Genomics and Oncological Research (GENyO), Pfizer, University of Granada, Andalusian Regional Government, Granada, Spain
| | - Teresa Requena
- Otology and Neurotology Group CTS 495, Department of Genomic Medicine, Centre for Genomics and Oncological Research (GENyO), Pfizer, University of Granada, Andalusian Regional Government, Granada, Spain
| | - Pablo Roman-Naranjo
- Otology and Neurotology Group CTS 495, Department of Genomic Medicine, Centre for Genomics and Oncological Research (GENyO), Pfizer, University of Granada, Andalusian Regional Government, Granada, Spain
| | - Jose A. Lopez-Escamez
- Otology and Neurotology Group CTS 495, Department of Genomic Medicine, Centre for Genomics and Oncological Research (GENyO), Pfizer, University of Granada, Andalusian Regional Government, Granada, Spain
- Department of Otolaryngology, Instituto de Investigación Biosanitaria (ibs. GRANADA), Hospital Universitario Virgen de las Nieves, Universidad de Granada, Granada, Spain
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11
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Albano JMR, Mussini N, Toriano R, Facelli JC, Ferraro MB, Pickholz M. Calcium interactions with Cx26 hemmichannel: Spatial association between MD simulations biding sites and variant pathogenicity. Comput Biol Chem 2018; 77:331-342. [PMID: 30466042 DOI: 10.1016/j.compbiolchem.2018.11.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 07/08/2018] [Accepted: 11/08/2018] [Indexed: 01/23/2023]
Abstract
Connexinophaties are a collective of diseases related to connexin channels and hemichannels. In particular many Cx26 alterations are strongly associated to human deafness. Calcium plays an important role on this structures regulation. Here, using calcium as a probe, extensive atomistic Molecular Dynamics simulations were performed on the Cx26 hemichannel embedded in a lipid bilayer. Exploring different initial conditions and calcium concentration, simulation reached ∼4 μs. Several analysis were carried out in order to reveal the calcium distribution and localization, such as electron density profiles, density maps and distance time evolution, which is directly associated to the interaction energy. Specific amino acid interactions with calcium and their stability were capture within this context. Few of these sites such as, GLU42, GLU47, GLY45 and ASP50, were already suggested in the literature. Besides, we identified novel calcium biding sites: ASP2, ASP117, ASP159, GLU114, GLU119, GLU120 and VAL226. To the best of our knowledge, this is the first time that these sites are reported within this context. Furthermore, since various pathologies involving the Cx26 hemichannel are associated with pathogenic variants in the corresponding CJB2 gene, using ClinVar, we were able to spatially associate the 3D positions of the identified calcium binding sites within the framework of this work with reported pathogenic variants in the CJB2 gene. This study presents a first step on finding associations between molecular features and pathological variants of the Cx26 hemichannel.
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Affiliation(s)
- Juan M R Albano
- Facultad de Ciencias Exactas y Naturales, Departamento de Física, Universidad de Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires, IFIBA, Buenos Aires, Argentina
| | - Nahuel Mussini
- Facultad de Ciencias Exactas y Naturales, Departamento de Física, Universidad de Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires, IFIBA, Buenos Aires, Argentina
| | - Roxana Toriano
- Facultad de Medicina, Departamento de Ciencias Fisiológicas, Laboratorio de Biomembranas, Buenos Aires, Argentina; CONICET - Universidad de Buenos Aires, IFIBIO Houssay, Buenos Aires, Argentina
| | - Julio C Facelli
- Department of Biomedical Informatics, The University of Utah, 421 Wakara Way, Suite 140, Salt Lake City, UT 84108, USA.
| | - Marta B Ferraro
- Facultad de Ciencias Exactas y Naturales, Departamento de Física, Universidad de Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires, IFIBA, Buenos Aires, Argentina
| | - Mónica Pickholz
- Facultad de Ciencias Exactas y Naturales, Departamento de Física, Universidad de Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires, IFIBA, Buenos Aires, Argentina
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12
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Plevova P, Tvrda P, Paprskarova M, Turska P, Kantorova B, Mrazkova E, Zapletalova J. Genetic Aetiology of Nonsyndromic Hearing Loss in Moravia-Silesia. MEDICINA-LITHUANIA 2018; 54:medicina54020028. [PMID: 30344259 PMCID: PMC6037260 DOI: 10.3390/medicina54020028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 05/01/2018] [Accepted: 05/02/2018] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND OBJECTIVE Hearing loss is the most common sensory deficit in humans. The aim of this study was to clarify the genetic aetiology of nonsyndromic hearing loss in the Moravian-Silesian population of the Czech Republic. PATIENTS AND METHODS This study included 200 patients (93 males, 107 females, mean age 16.9 years, ranging from 4 months to 62 years) with nonsyndromic sensorineural hearing loss. We screened all patients for mutations in GJB2 and the large deletion del(GJB6-D13S1830). We performed further screening for additional genes (SERPINB6, TMIE, COCH, ESPN, ACTG1, KCNQ4, and GJB3) with Sanger sequencing on a subset of patients that were negative for GJB2 mutations. RESULTS We detected biallelic GJB2 mutations in 44 patients (22%). Among these patients, 63.6%, 9.1% and 2.3% exhibited homozygous c.35delG, p.Trp24*, and p.Met34Thr mutations, respectively. The remaining 25% of these patients exhibited compound heterozygous c.35delG, c.-23+1G>A, p.Trp24*, p.Val37Ile, p.Met34Thr, p.Leu90Pro, c.235delC, c.313_326del14, p.Ser139Asn, and p.Gly147Leu mutations. We found a monoallelic GJB2 mutation in 12 patients (6.6%). We found no pathogenic mutations in the other tested genes. Conclusions: One fifth of our cohort had deafness related to GJB2 mutations. The del(GJB6-D13S1830), SERPINB6, TMIE, COCH, ESPN, ACTG1, GJB3, and KCNQ4 mutations were infrequently associated with deafness in the Moravian-Silesian population. Therefore, we suggest that del(GJB6-D13S1830) testing should be performed only when patients with deafness carry the monoallelic GJB2 mutation.
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Affiliation(s)
- Pavlina Plevova
- Department of Medical Genetics, University Hospital Ostrava, 17. listopadu 1790, 708 52 Ostrava, Czech Republic.
| | - Petra Tvrda
- Department of Medical Genetics, University Hospital Ostrava, 17. listopadu 1790, 708 52 Ostrava, Czech Republic.
| | - Martina Paprskarova
- Department of Medical Genetics, University Hospital Ostrava, 17. listopadu 1790, 708 52 Ostrava, Czech Republic.
| | - Petra Turska
- Department of Medical Genetics, University Hospital Ostrava, 17. listopadu 1790, 708 52 Ostrava, Czech Republic.
| | - Barbara Kantorova
- Department of Medical Genetics, University Hospital Ostrava, 17. listopadu 1790, 708 52 Ostrava, Czech Republic.
| | - Eva Mrazkova
- Department of Epidemiology and Public Health, Faculty of Medicine, University of Ostrava, Syllabova 19, 703 00 Ostrava, Zábřeh, Czech Republic.
- Department of Otorhinolaryngology, Hospital of Havířov, Dělnická 1132/24, 736 01 Havířov, Czech Republic.
| | - Jana Zapletalova
- Department of Medical Biophysics, Faculty of Medicine and Dentistry, Palacky University Olomouc, Hnevotinska 3, 775 15 Olomouc, Czech Republic.
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13
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del Castillo FJ, del Castillo I. DFNB1 Non-syndromic Hearing Impairment: Diversity of Mutations and Associated Phenotypes. Front Mol Neurosci 2017; 10:428. [PMID: 29311818 PMCID: PMC5743749 DOI: 10.3389/fnmol.2017.00428] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 12/07/2017] [Indexed: 02/02/2023] Open
Abstract
The inner ear is a very complex sensory organ whose development and function depend on finely balanced interactions among diverse cell types. The many different kinds of inner ear supporting cells play the essential roles of providing physical and physiological support to sensory hair cells and of maintaining cochlear homeostasis. Appropriately enough, the gene most commonly mutated among subjects with hereditary hearing impairment (HI), GJB2, encodes the connexin-26 (Cx26) gap-junction channel protein that underlies both intercellular communication among supporting cells and homeostasis of the cochlear fluids, endolymph and perilymph. GJB2 lies at the DFNB1 locus on 13q12. The specific kind of HI associated with this locus is caused by recessively-inherited mutations that inactivate the two alleles of the GJB2 gene, either in homozygous or compound heterozygous states. We describe the many diverse classes of genetic alterations that result in DFNB1 HI, such as large deletions that either destroy the GJB2 gene or remove a regulatory element essential for GJB2 expression, point mutations that interfere with promoter function or splicing, and small insertions or deletions and nucleotide substitutions that target the GJB2 coding sequence. We focus on how these alterations disrupt GJB2 and Cx26 functions and on their different effects on cochlear development and physiology. We finally discuss the diversity of clinical features of DFNB1 HI as regards severity, age of onset, inner ear malformations and vestibular dysfunction, highlighting the areas where future research should be concentrated.
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Affiliation(s)
- Francisco J. del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Ignacio del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
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14
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de Wolf E, van de Wiel J, Cook J, Dale N. Altered CO2 sensitivity of connexin26 mutant hemichannels in vitro. Physiol Rep 2017; 4:4/22/e13038. [PMID: 27884957 PMCID: PMC5357999 DOI: 10.14814/phy2.13038] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 10/19/2016] [Accepted: 10/21/2016] [Indexed: 12/17/2022] Open
Abstract
Connexin26 (Cx26) mutations underlie human pathologies ranging from hearing loss to keratitis ichthyosis deafness (KID) syndrome. Cx26 hemichannels are directly gated by CO2 and contribute to the chemosensory regulation of breathing. The KID syndrome mutation A88V is insensitive to CO2, and has a dominant negative action on the CO2 sensitivity of Cx26WT hemichannels, and reduces respiratory drive in humans. We have now examined the effect of further human mutations of Cx26 on its sensitivity to CO2 : Mutated Cx26 subunits, carrying one of A88S, N14K, N14Y, M34T, or V84L, were transiently expressed in HeLa cells. The CO2-dependence of hemichannel activity, and their ability to exert dominant negative actions on cells stably expressing Cx26WT, was quantified by a dye-loading assay. The KID syndrome mutation, N14K, abolished the sensitivity of Cx26 to CO2 Both N14Y and N14K exerted a powerful dominant negative action on the CO2 sensitivity of Cx26WT None of the other mutations (all recessive) had a dominant negative action. A88S shifted the affinity of Cx26 to slightly higher levels without reducing its ability to fully open to CO2 M34T did not change the affinity of Cx26 for CO2 but reduced its ability to open in response to CO2 V84L had no effect on the CO2-sensitivity of Cx26. Some pathological mutations of Cx26 can therefore alter the CO2 sensitivity of Cx26 hemichannels. The loss of CO2 sensitivity could contribute to pathology and consequent reduced respiratory drive could be an unrecognized comorbidity of these pathologies.
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Affiliation(s)
- Elizabeth de Wolf
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Joseph van de Wiel
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Jonathan Cook
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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15
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Nin F, Yoshida T, Sawamura S, Ogata G, Ota T, Higuchi T, Murakami S, Doi K, Kurachi Y, Hibino H. The unique electrical properties in an extracellular fluid of the mammalian cochlea; their functional roles, homeostatic processes, and pathological significance. Pflugers Arch 2016; 468:1637-49. [PMID: 27568193 PMCID: PMC5026722 DOI: 10.1007/s00424-016-1871-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 08/16/2016] [Indexed: 12/13/2022]
Abstract
The cochlea of the mammalian inner ear contains an endolymph that exhibits an endocochlear potential (EP) of +80 mV with a [K(+)] of 150 mM. This unusual extracellular solution is maintained by the cochlear lateral wall, a double-layered epithelial-like tissue. Acoustic stimuli allow endolymphatic K(+) to enter sensory hair cells and excite them. The positive EP accelerates this K(+) influx, thereby sensitizing hearing. K(+) exits from hair cells and circulates back to the lateral wall, which unidirectionally transports K(+) to the endolymph. In vivo electrophysiological assays demonstrated that the EP stems primarily from two K(+) diffusion potentials yielded by [K(+)] gradients between intracellular and extracellular compartments in the lateral wall. Such gradients seem to be controlled by ion channels and transporters expressed in particular membrane domains of the two layers. Analyses of human deafness genes and genetically modified mice suggested the contribution of these channels and transporters to EP and hearing. A computational model, which reconstitutes unidirectional K(+) transport by incorporating channels and transporters in the lateral wall and connects this transport to hair cell transcellular K(+) fluxes, simulates the circulation current flowing between the endolymph and the perilymph. In this model, modulation of the circulation current profile accounts for the processes leading to EP loss under pathological conditions. This article not only summarizes the unique physiological and molecular mechanisms underlying homeostasis of the EP and their pathological relevance but also describes the interplay between EP and circulation current.
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Affiliation(s)
- Fumiaki Nin
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
| | - Takamasa Yoshida
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
- Center for Transdisciplinary Research, Niigata University, Niigata, 950-2181, Japan
- Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan
| | - Seishiro Sawamura
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
| | - Genki Ogata
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
- Center for Transdisciplinary Research, Niigata University, Niigata, 950-2181, Japan
| | - Takeru Ota
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
| | - Taiga Higuchi
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan
| | - Shingo Murakami
- Division of Molecular and Cellular Pharmacology, Department of Pharmacology, Osaka University, Osaka, 565-0871, Japan
- Center for Advanced Medical Engineering and Informatics, Graduate School of Medicine, Osaka University, Osaka, 565-0871, Japan
- Department of Physiology, School of Medicine, Toho University, Tokyo, 143-8540, Japan
| | - Katsumi Doi
- Department of Otolaryngology, Kindai University Faculty of Medicine, Osaka, 589-8511, Japan
| | - Yoshihisa Kurachi
- Division of Molecular and Cellular Pharmacology, Department of Pharmacology, Osaka University, Osaka, 565-0871, Japan
- Center for Advanced Medical Engineering and Informatics, Graduate School of Medicine, Osaka University, Osaka, 565-0871, Japan
| | - Hiroshi Hibino
- Department of Molecular Physiology, Niigata University School of Medicine, 1-757 Asahimachi-dori, Chuo-ku, Niigata, Niigata, 951-8510, Japan.
- Center for Transdisciplinary Research, Niigata University, Niigata, 950-2181, Japan.
- AMED-CREST, AMED, Niigata, Japan.
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16
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García IE, Prado P, Pupo A, Jara O, Rojas-Gómez D, Mujica P, Flores-Muñoz C, González-Casanova J, Soto-Riveros C, Pinto BI, Retamal MA, González C, Martínez AD. Connexinopathies: a structural and functional glimpse. BMC Cell Biol 2016; 17 Suppl 1:17. [PMID: 27228968 PMCID: PMC4896260 DOI: 10.1186/s12860-016-0092-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Mutations in human connexin (Cx) genes have been related to diseases, which we termed connexinopathies. Such hereditary disorders include nonsyndromic or syndromic deafness (Cx26, Cx30), Charcot Marie Tooth disease (Cx32), occulodentodigital dysplasia and cardiopathies (Cx43), and cataracts (Cx46, Cx50). Despite the clinical phenotypes of connexinopathies have been well documented, their pathogenic molecular determinants remain elusive. The purpose of this work is to identify common/uncommon patterns in channels function among Cx mutations linked to human diseases. To this end, we compiled and discussed the effect of mutations associated to Cx26, Cx32, Cx43, and Cx50 over gap junction channels and hemichannels, highlighting the function of the structural channel domains in which mutations are located and their possible role affecting oligomerization, gating and perm/selectivity processes.
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Affiliation(s)
- Isaac E García
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Pavel Prado
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Oscar Jara
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Diana Rojas-Gómez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Paula Mujica
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Flores-Muñoz
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Jorge González-Casanova
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carolina Soto-Riveros
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Bernardo I Pinto
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
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LI YUNLONG, ZHU BAOSHENG. Genotypes and phenotypes of a family with a deaf child carrying combined heterozygous mutations in SLC26A4 and GJB3 genes. Mol Med Rep 2016; 14:319-24. [DOI: 10.3892/mmr.2016.5280] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 03/29/2016] [Indexed: 11/06/2022] Open
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Dória M, Fernandes S, Moura CP. Study of Met34Thr variant in nonsyndromic hearing loss in four Portuguese families. Porto Biomed J 2016; 1:32-35. [PMID: 32258544 DOI: 10.1016/j.pbj.2015.07.001] [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: 04/22/2015] [Accepted: 07/28/2015] [Indexed: 10/21/2022] Open
Abstract
Objective The purpose of this work was to characterize the Met34Thr variant in a group of patients with nonsyndromic hearing loss, in order to establish a genotype-phenotype correlation. Methods 13 cases from 4 unrelated Portuguese families were selected, in which one or more hearing-impaired members had Met34Thr variant. Results Met34Thr variant was identified in 11/13 cases. Two cases have an additional mutation - Val153Ile and 35delG. Hearing loss was mild in 2 patients (Met34Thr/Val153Ile; Met34Thr/Met34Thr), moderate in 3(Met34Thr/WT; Met34Thr/35delG; Met34Thr/Met34Thr), severe in 2 (2 Met34Thr/WT) and profound in 1 (Met34Thr/WT). Three individuals with Met34Thr had normal hearing thresholds. Conclusion The present data corroborate the hypothesis that the Met34Thr variant is associated with mild-to-severe forms of deafness and that this variant seems to segregate with a dominant hearing loss with incomplete penetrance and a variable expression of the phenotype. However, other factors are likely to also have a pathologic effect.
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Affiliation(s)
- Mariana Dória
- Faculty of Medicine, University of Porto, Porto, Portugal
| | - Susana Fernandes
- Department of Human Genetics, Faculty of Medicine, University of Porto/São João Hospital Center, Porto, Portugal.,Institute for Research and Innovation in Health/Instituto de Investigação e Inovação em Saúde, University of Porto, Porto, Portugal
| | - Carla Pinto Moura
- Faculty of Medicine, University of Porto, Porto, Portugal.,Institute for Research and Innovation in Health/Instituto de Investigação e Inovação em Saúde, University of Porto, Porto, Portugal.,Department of Otorhinolaryngology and Department of Human Genetics, São João Hospital Center, Porto, Portugal
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Mikstiene V, Jakaitiene A, Byckova J, Gradauskiene E, Preiksaitiene E, Burnyte B, Tumiene B, Matuleviciene A, Ambrozaityte L, Uktveryte I, Domarkiene I, Rancelis T, Cimbalistiene L, Lesinskas E, Kucinskas V, Utkus A. The high frequency of GJB2 gene mutation c.313_326del14 suggests its possible origin in ancestors of Lithuanian population. BMC Genet 2016; 17:45. [PMID: 26896187 PMCID: PMC4761217 DOI: 10.1186/s12863-016-0354-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 02/15/2016] [Indexed: 12/30/2022] Open
Abstract
Background Congenital hearing loss (CHL) is diagnosed in 1 – 2 newborns in 1000, genetic factors contribute to two thirds of CHL cases in industrialised countries. Mutations of the GJB2 gene located in the DFNB1 locus (13q11-12) are a major cause of CHL worldwide. The aim of this cross-sectional study was to assess the contribution of the DFNB1 locus containing the GJB2 and GJB6 genes in the development of early onset hearing loss in the affected group of participants, to determine the population-specific mutational profile and DFNB1-related HL burden in Lithuanian population. Methods Clinical data were obtained from a collection of 158 affected participants (146 unrelated probands) with early onset non-syndromic HL. GJB2 and GJB6 gene sequencing and GJB6 gene deletion testing were performed. The data of GJB2 and GJB6 gene sequencing in 98 participants in group of self-reported healthy Lithuanian inhabitants were analysed. Statistic summary, homogeneity tests, and logistic regression analysis were used for the assessment of genotype-phenotype correlation. Results Our findings show 57.5 % of affected participants with two pathogenic GJB2 gene mutations identified. The most prevalent GJB2 mutations were c.35delG, p. (Gly12Valfs*2) (rs80338939) and c.313_326del14, p. (Lys105Glyfs*5) (rs111033253) with allele frequencies 64.7 % and 28.3 % respectively. GJB6 gene mutations were not identified in the affected group of participants. The statistical analysis revealed significant differences between GJB2(−) and GJB2(+) groups in disease severity (p = 0.001), and family history (p = 0.01). The probability of identification of GJB2 mutations in patients with various HL characteristics was estimated. The carrier rate of GJB2 gene mutations – 7.1 % (~1 in 14) was identified in the group of healthy participants and a high frequency of GJB2-related hearing loss was estimated in our population. Discussion The results show a very high proportion of GJB2-positive individuals in the research group affected with sensorineural HL. The allele frequency of c.35delG mutation (64.7 %) is consistent with many previously published studies in groups of affected individuals of Caucasian populations. The high frequency of the c.313_326del14 (28.3 % of pathogenic alleles) mutation in affected group of participants was an unexpected finding in our study suggesting not only a high frequency of carriers of this mutation in our population but also its possible origin in Lithuanian ancestors. The high frequency of carriers of the c.313_326del14 mutation in the entire Lithuanian population is supported by it being identified twice in the ethnic Lithuanian group of healthy participants (a frequency 2.0 % of carriers in the study group). Conclusion Analysis of the allele frequency of GJB2 gene mutations revealed a high proportion of c. 313_326del14 (rs111033253) mutations in the GJB2-positive group suggesting its possible origin in Lithuanian forebears. The high frequency of carriers of GJB2 gene mutations in the group of healthy participants corresponds to the substantial frequency of GJB2-associated HL in Lithuania. The observations of the study indicate the significant contribution of GJB2 gene mutations to the pathogenesis of the disorder in the Lithuanian population and will contribute to introducing principles to predict the characteristics of the disease in patients. Electronic supplementary material The online version of this article (doi:10.1186/s12863-016-0354-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Violeta Mikstiene
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Audrone Jakaitiene
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Jekaterina Byckova
- Centre of Ear, Nose and Throat Diseases, Vilnius University Hospital Santariskiu clinics, Vilnius, Lithuania.
| | - Egle Gradauskiene
- Centre of Ear, Nose and Throat Diseases, Vilnius University Hospital Santariskiu clinics, Vilnius, Lithuania.
| | - Egle Preiksaitiene
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Birute Burnyte
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Birute Tumiene
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Ausra Matuleviciene
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Laima Ambrozaityte
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Ingrida Uktveryte
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Ingrida Domarkiene
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Tautvydas Rancelis
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Loreta Cimbalistiene
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Eugenijus Lesinskas
- Centre of Ear, Nose and Throat Diseases, Vilnius University Hospital Santariskiu clinics, Vilnius, Lithuania.
| | - Vaidutis Kucinskas
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
| | - Algirdas Utkus
- Department of Human and Medical Genetics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania.
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Dória M, Neto AP, Santos AC, Barros H, Fernandes S, Moura CP. Prevalence of 35delG and Met34Thr GJB2 variants in Portuguese samples. Int J Pediatr Otorhinolaryngol 2015; 79:2187-90. [PMID: 26482070 DOI: 10.1016/j.ijporl.2015.09.046] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 09/25/2015] [Accepted: 09/30/2015] [Indexed: 10/22/2022]
Abstract
OBJECTIVE To estimate the prevalence of 35delG and Met34Thr variants in a Portuguese children's community sample and to compare these frequencies with nonsyndromic hearing-loss patients. METHODS 502 children were randomly selected among the 8647 participants of the Portuguese birth cohort Generation XXI, and screened for Met34Thr and 35delG variants in the GJB2 gene. These variants were also studied on 89 index-cases, observed in the Clinic of "Hereditary Hearing-loss" in Saint John's Hospital Center, presenting a mild to profound nonsyndromic hearing-loss. RESULTS Among the 502 children from Generation XXI, 10 were heterozygous for the 35delG variant (95% Confidence Interval 1.03-3.68) and 1 homozygous (95% Confidence Interval 0.01-1.24). Other 10 children presented heterozygosity for the Met34Thr variant (95% Confidence Interval 1.03-3.68). No homozygous for the Met34Thr or compound heterozygotes (35delG/Met34Thr) were found. In the total of 89 nonsyndromic hearing-loss patients, 5 (95% Confidence Interval 2.11-12.8) were heterozygous and 7 (95% Confidence Interval 3.61-15.6) were homozygous for the 35delG variant. The Met34Thr variant was found in 4 patients, 2 heterozygous (95% Confidence Interval 0.13-8.31) and 2 homozygous (95% Confidence Interval 0.13-8.31). CONCLUSION The carrier frequency of 35delG and Met34Thr variants in a Portuguese sample was 1 in 50. Our data suggests that the 35delG mutation has an association with deafness. For the Met34Thr variant, no association was observed. However, Met34Thr seemed to conform to an additive model in hearing-loss.
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Affiliation(s)
- Mariana Dória
- Faculty of Medicine, University of Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal.
| | - Ana Paula Neto
- Department of Human Genetics, Faculty of Medicine, University of Porto, Centro Hospitalar São João, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal; Institute for Research and Innovation in Health/Instituto de Investigação e Inovação em Saúde, University of Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal
| | - Ana Cristina Santos
- Department of Clinical Epidemiology, Predictive Medicine and Public Health, Faculty of Medicine, University of Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal; EPI Unit-Institute of Public Health, University of Porto, Rua das Taipas no. 135, 4050-600 Porto, Portugal
| | - Henrique Barros
- Department of Clinical Epidemiology, Predictive Medicine and Public Health, Faculty of Medicine, University of Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal; EPI Unit-Institute of Public Health, University of Porto, Rua das Taipas no. 135, 4050-600 Porto, Portugal
| | - Susana Fernandes
- Department of Human Genetics, Faculty of Medicine, University of Porto, Centro Hospitalar São João, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal; Institute for Research and Innovation in Health/Instituto de Investigação e Inovação em Saúde, University of Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal
| | - Carla Pinto Moura
- Department of Human Genetics, Faculty of Medicine, University of Porto, Centro Hospitalar São João, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal; Institute for Research and Innovation in Health/Instituto de Investigação e Inovação em Saúde, University of Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal; Department of Otorhinolaryngology, Centro Hospitalar São João, Faculty of Medicine, University of Porto, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal
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Characterization of a novel water pocket inside the human Cx26 hemichannel structure. Biophys J 2015; 107:599-612. [PMID: 25099799 DOI: 10.1016/j.bpj.2014.05.037] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 05/12/2014] [Accepted: 05/14/2014] [Indexed: 01/09/2023] Open
Abstract
Connexins (Cxs) are a family of vertebrate proteins constituents of gap junction channels (GJCs) that connect the cytoplasm of adjacent cells by the end-to-end docking of two Cx hemichannels. The intercellular transfer through GJCs occurs by passive diffusion allowing the exchange of water, ions, and small molecules. Despite the broad interest to understand, at the molecular level, the functional state of Cx-based channels, there are still many unanswered questions regarding structure-function relationships, perm-selectivity, and gating mechanisms. In particular, the ordering, structure, and dynamics of water inside Cx GJCs and hemichannels remains largely unexplored. In this work, we describe the identification and characterization of a believed novel water pocket-termed the IC pocket-located in-between the four transmembrane helices of each human Cx26 (hCx26) monomer at the intracellular (IC) side. Using molecular dynamics (MD) simulations to characterize hCx26 internal water structure and dynamics, six IC pockets were identified per hemichannel. A detailed characterization of the dynamics and ordering of water including conformational variability of residues forming the IC pockets, together with multiple sequence alignments, allowed us to propose a functional role for this cavity. An in vitro assessment of tracer uptake suggests that the IC pocket residue Arg-143 plays an essential role on the modulation of the hCx26 hemichannel permeability.
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The controversial p.Met34Thr variant in GJB2 gene: Two siblings, one genotype, two phenotypes. Int J Pediatr Otorhinolaryngol 2015; 79:1316-9. [PMID: 26117665 DOI: 10.1016/j.ijporl.2015.05.041] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 05/27/2015] [Accepted: 05/31/2015] [Indexed: 01/02/2023]
Abstract
INTRODUCTION Recent advances in molecular genetics have increased the identification of genes and mutations responsible for inherited forms of hearing loss (HL), enabling early detection of these cases. Approximately, 60% of early-onset HL cases are due to genetic causes, of which 70% are non-syndromic. Of these, 75-80% are inherited in an autosomal recessive pattern (DFNB). Mutations in GJB2 gene, coding for connexin 26 (Cx26), are the major cause of autosomal recessive hereditary HL, but some GJB2 mutations are yet of unclear or controversial significance. OBJECTIVES The aim of the present study was to identify the etiology of hearing loss, and correlate genotype-phenotype, in two Portuguese siblings with profound and moderate non-syndromic sensorineural bilateral HL. MATERIAL AND METHODS The affected subjects and their parents underwent audiological and genetic study. Molecular analysis of GJB2 gene was performed, searching for mutations in the coding region and receptor splicing site by automated sequencing. RESULTS The onset and the degree of HL were different in the two affected subjects. However, the same GJB2 genotype [p.Met34Thr]+[p.Arg184Pro] was identified in both siblings. The c.551G>C (p.Arg184Pro) and c.101T>C (p.Met34Thr) missense variants were inherited from the father and mother, respectively, both heterozygous carriers of these variants. CONCLUSION The clinical and genetic data here presented suggest that the non-syndromic sensorineural HL of these two Portuguese siblings might be due to the presence of p.Met34Thr and p.Arg184Pro variants in compound heterozygosity. If so, p.Met34Thr variant could have function as a hypomorphic allele that may cause HL depending on the opposing GJB2 allele. The observed phenotypic variability may not, however, be solely explained by variable expression of this genotype. A putative modifier gene or mutations in another HL-associated gene could probably be contributing to the severe HL in one of the siblings.
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Non-syndromic hearing loss caused by the dominant cis mutation R75Q with the recessive mutation V37I of the GJB2 (Connexin 26) gene. Exp Mol Med 2015; 47:e169. [PMID: 26088551 PMCID: PMC4491724 DOI: 10.1038/emm.2015.32] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 03/08/2015] [Indexed: 11/08/2022] Open
Abstract
GJB2 alleles containing two cis mutations have been rarely found in non-syndromic hearing loss. Herein, we present a Korean patient with non-syndromic hearing loss caused by the R75Q cis mutation with V37I, which arose de novo in the father and was inherited by the patient. Biochemical coupling and hemichannel permeability assays were performed after molecular cloning and transfection of HEK293T cells. Student's t-tests or analysis of variance followed by Tukey's multiple comparison test was used as statistical analysis. Biochemical coupling was significantly reduced in connexin 26 (Cx26)-R75Q- and Cx26-V37I-transfected cells, with greater extent in Cx26-R75Q and Cx26-R75Q+V37I cells. Interestingly, our patient and his father with the mutations had more residual hearing compared with patients with the dominant mutation alone. Although the difference in hemichannel activity between R75Q alone and R75Q in combination with V37I failed to reach significance, it is of note that there is a possibility that V37I located upstream of R75Q might have the ability to ameliorate R75Q expression. Our study emphasizes the importance of cis mutations with R75Q, as the gene effect of R75Q can be modulated depending on the type of additional mutation.
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Wingard JC, Zhao HB. Cellular and Deafness Mechanisms Underlying Connexin Mutation-Induced Hearing Loss - A Common Hereditary Deafness. Front Cell Neurosci 2015; 9:202. [PMID: 26074771 PMCID: PMC4448512 DOI: 10.3389/fncel.2015.00202] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Accepted: 05/11/2015] [Indexed: 11/30/2022] Open
Abstract
Hearing loss due to mutations in the connexin gene family, which encodes gap junctional proteins, is a common form of hereditary deafness. In particular, connexin 26 (Cx26, GJB2) mutations are responsible for ~50% of non-syndromic hearing loss, which is the highest incidence of genetic disease. In the clinic, Cx26 mutations cause various auditory phenotypes ranging from profound congenital deafness at birth to mild, progressive hearing loss in late childhood. Recent experiments demonstrate that congenital deafness mainly results from cochlear developmental disorders rather than hair cell degeneration and endocochlear potential reduction, while late-onset hearing loss results from reduction of active cochlear amplification, even though cochlear hair cells have no connexin expression. However, there is no apparent, demonstrable relationship between specific changes in connexin (channel) functions and the phenotypes of mutation-induced hearing loss. Moreover, new experiments further demonstrate that the hypothesized K+-recycling disruption is not a principal deafness mechanism for connexin deficiency induced hearing loss. Cx30 (GJB6), Cx29 (GJC3), Cx31 (GJB3), and Cx43 (GJA1) mutations can also cause hearing loss with distinct pathological changes in the cochlea. These new studies provide invaluable information about deafness mechanisms underlying connexin mutation-induced hearing loss and also provide important information for developing new protective and therapeutic strategies for this common deafness. However, the detailed cellular mechanisms underlying these pathological changes remain unclear. Also, little is known about specific mutation-induced pathological changes in vivo and little information is available for humans. Such further studies are urgently required.
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Affiliation(s)
- Jeffrey C Wingard
- Department of Otolaryngology, University of Kentucky Medical Center , Lexington, KY , USA
| | - Hong-Bo Zhao
- Department of Otolaryngology, University of Kentucky Medical Center , Lexington, KY , USA
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Zonta F, Girotto G, Buratto D, Crispino G, Morgan A, Abdulhadi K, Alkowari M, Badii R, Gasparini P, Mammano F. The p.Cys169Tyr variant of connexin 26 is not a polymorphism. Hum Mol Genet 2015; 24:2641-8. [PMID: 25628337 PMCID: PMC4383868 DOI: 10.1093/hmg/ddv026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/21/2015] [Indexed: 12/31/2022] Open
Abstract
Mutations in the GJB2 gene, which encodes the gap junction protein connexin 26 (Cx26), are the primary cause of hereditary prelingual hearing impairment. Here, the p.Cys169Tyr missense mutation of Cx26 (Cx26C169Y), previously classified as a polymorphism, has been identified as causative of severe hearing loss in two Qatari families. We have analyzed the effect of this mutation using a combination of confocal immunofluorescence microscopy and molecular dynamics simulations. At the cellular level, our results show that the mutant protein fails to form junctional channels in HeLa transfectants despite being correctly targeted to the plasma membrane. At the molecular level, this effect can be accounted for by disruption of the disulfide bridge that Cys169 forms with Cys64 in the wild-type structure (Cx26WT). The lack of the disulfide bridge in the Cx26C169Y protein causes a spatial rearrangement of two important residues, Asn176 and Thr177. In the Cx26WT protein, these residues play a crucial role in the intra-molecular interactions that permit the formation of an intercellular channel by the head-to-head docking of two opposing hemichannels resident in the plasma membrane of adjacent cells. Our results elucidate the molecular pathogenesis of hereditary hearing loss due to the connexin mutation and facilitate the understanding of its role in both healthy and affected individuals.
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Affiliation(s)
- Francesco Zonta
- Dipartimento di Fisica e Astronomia 'G. Galilei', Università di Padova, 35131 Padova, Italy
| | - Giorgia Girotto
- Department of Medical, Surgical and Health Sciences, University of Trieste, 34100 Trieste, Italy
| | - Damiano Buratto
- Dipartimento di Fisica e Astronomia 'G. Galilei', Università di Padova, 35131 Padova, Italy
| | - Giulia Crispino
- Dipartimento di Fisica e Astronomia 'G. Galilei', Università di Padova, 35131 Padova, Italy, Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Anna Morgan
- Department of Medical, Surgical and Health Sciences, University of Trieste, 34100 Trieste, Italy
| | - Khalid Abdulhadi
- Audiology and Balance Unit, National Program for Early Detection of Hearing Loss, WH, Hamad Medical Corporation (HMC) Doha, Doha, Qatar
| | - Moza Alkowari
- Molecular Genetics Laboratory, Department of Laboratory of Medicine and Pathology, Hamad Medical Corporation (HMC), Doha, Qatar
| | - Ramin Badii
- Molecular Genetics Laboratory, Department of Laboratory of Medicine and Pathology, Hamad Medical Corporation (HMC), Doha, Qatar
| | - Paolo Gasparini
- Department of Medical, Surgical and Health Sciences, University of Trieste, 34100 Trieste, Italy, Medical Genetics, Institute for Maternal and Child Health-IRCCS 'Burlo Garofolo', Trieste, Italy and
| | - Fabio Mammano
- Dipartimento di Fisica e Astronomia 'G. Galilei', Università di Padova, 35131 Padova, Italy, Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy, CNR Institute of Cell Biology and Neurobiology, 00015 Monterotondo, Rome, Italy
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Mroue R, Inman J, Mott J, Budunova I, Bissell MJ. Asymmetric expression of connexins between luminal epithelial- and myoepithelial- cells is essential for contractile function of the mammary gland. Dev Biol 2014; 399:15-26. [PMID: 25500615 DOI: 10.1016/j.ydbio.2014.11.026] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 11/27/2014] [Accepted: 11/28/2014] [Indexed: 12/20/2022]
Abstract
Intercellular communication is essential for glandular functions and tissue homeostasis. Gap junctions couple cells homotypically and heterotypically and co-ordinate reciprocal responses between the different cell types. Connexins (Cxs) are the main mammalian gap junction proteins, and the distribution of some Cx subtypes in the heterotypic gap junctions is not symmetrical; in the murine mammary gland, Cx26, Cx30 and Cx32 are expressed only in the luminal epithelial cells and Cx43 is expressed only in myoepithelial cells. Expression of all four Cxs peaks during late pregnancy and throughout lactation suggesting essential roles for these proteins in the functional secretory activity of the gland. Transgenic (Tg) mice over-expressing Cx26 driven by keratin 5 promoter had an unexpected mammary phenotype: the mothers were unable to feed their pups to weaning age leading to litter starvation and demise in early to mid-lactation. The mammary gland of K5-Cx26 female mice developed normally and produced normal levels of milk protein, suggesting a defect in delivery rather than milk production. Because the mammary gland of K5-Cx26 mothers contained excessive milk, we hypothesized that the defect may be in an inability to eject the milk. Using ex vivo three-dimensional mammary organoid cultures, we showed that tissues isolated from wild-type FVB females contracted upon treatment with oxytocin, whereas, organoids from Tg mice failed to do so. Unexpectedly, we found that ectopic expression of Cx26 in myoepithelial cells altered the expression of endogenous Cx43 resulting in impaired gap junction communication, demonstrated by defective dye coupling in mammary epithelial cells of Tg mice. Inhibition of gap junction communication or knock-down of Cx43 in organoids from wild-type mice impaired contraction in response to oxytocin, recapitulating the observations from the mammary glands of Tg mice. We conclude that Cx26 acts as a trans-dominant negative for Cx43 function in myoepithelial cells, highlighting the importance of cell type-specific expression of Cxs for optimal contractile function of the mammary myoepithelium.
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Affiliation(s)
- Rana Mroue
- Helen Diller Family Cancer Research Center, UCSF, 1450 3rd street, San Francisco, CA 94158, USA
| | - Jamie Inman
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Joni Mott
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Irina Budunova
- Department of Dermatology, Northwestern University Feinberg School of Medicine, 676 North St. Clair Street, Suite 1600, Chicago, IL 60611, USA
| | - Mina J Bissell
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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Jagger DJ, Forge A. Connexins and gap junctions in the inner ear--it's not just about K⁺ recycling. Cell Tissue Res 2014; 360:633-44. [PMID: 25381570 PMCID: PMC4452565 DOI: 10.1007/s00441-014-2029-z] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 10/06/2014] [Indexed: 12/19/2022]
Abstract
Normal development, function and repair of the sensory epithelia in the inner ear are all dependent on gap junctional intercellular communication. Mutations in the connexin genes GJB2 and GJB6 (encoding CX26 and CX30) result in syndromic and non-syndromic deafness via various mechanisms. Clinical vestibular defects, however, are harder to connect with connexin dysfunction. Cx26 and Cx30 proteins are widely expressed in the epithelial and connective tissues of the cochlea, where they may form homomeric or heteromeric gap junction channels in a cell-specific and spatiotemporally complex fashion. Despite the study of mutant channels and animal models for both recessive and dominant autosomal deafness, it is still unclear why gap junctions are essential for auditory function, and why Cx26 and Cx30 do not compensate for each other in vivo. Cx26 appears to be essential for normal development of the auditory sensory epithelium, but may be dispensable during normal hearing. Cx30 appears to be essential for normal repair following sensory cell loss. The specific modes of intercellular signalling mediated by inner ear gap junction channels remain undetermined, but they are hypothesised to play essential roles in the maintenance of ionic and metabolic homeostasis in the inner ear. Recent studies have highlighted involvement of gap junctions in the transfer of essential second messengers between the non-sensory cells, and have proposed roles for hemichannels in normal hearing. Here, we summarise the current knowledge about the molecular and functional properties of inner ear gap junctions, and about tissue pathologies associated with connexin mutations.
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Affiliation(s)
- Daniel J Jagger
- UCL Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK,
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Zonta F, Buratto D, Cassini C, Bortolozzi M, Mammano F. Molecular dynamics simulations highlight structural and functional alterations in deafness-related M34T mutation of connexin 26. Front Physiol 2014; 5:85. [PMID: 24624091 PMCID: PMC3941013 DOI: 10.3389/fphys.2014.00085] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 02/12/2014] [Indexed: 11/22/2022] Open
Abstract
Mutations of the GJB2 gene encoding the connexin 26 (Cx26) gap junction protein, which is widely expressed in the inner ear, are the primary cause of hereditary non-syndromic hearing loss in several populations. The deafness–associated single amino acid substitution of methionine 34 (M34) in the first transmembrane helix (TM1) with a threonine (T) ensues in the production of mutant Cx26M34T channels that are correctly synthesized and assembled in the plasma membrane. However, mutant channels overexpressed in HeLa cells retain only 11% of the wild type unitary conductance. Here we extend and rationalize those findings by comparing wild type Cx26 (Cx26WT) and Cx26M34T mutant channels in silico, using molecular dynamics simulations. Our results indicate that the quaternary structure of the Cx26M34T hemichannel is altered at the level of the pore funnel due to the disruption of the hydrophobic interaction between M34 and tryptophan 3 (W3) in the N–terminal helix (NTH). Our simulations also show that external force stimuli applied to the NTHs can detach them from the inner wall of the pore more readily in the mutant than in the wild type hemichannel. These structural alterations significantly increase the free energy barrier encountered by permeating ions, correspondingly decreasing the unitary conductance of the Cx26M34T hemichannel. Our results accord with the proposal that the mutant resides most of the time in a low conductance state. However, the small displacement of the NTHs in our Cx26M34T hemichannel model is not compatible with the formation of a pore plug as in the related Cx26M34A mutant.
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Affiliation(s)
- Francesco Zonta
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy
| | - Damiano Buratto
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy
| | - Chiara Cassini
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy
| | - Mario Bortolozzi
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy ; Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata Padova, Italy
| | - Fabio Mammano
- Dipartimento di Fisica e Astronomia "G. Galilei", Università degli Studi di Padova Padova, Italy ; Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata Padova, Italy ; Istituto di Neuroscienze, Consiglio Nazionale delle Ricerche Padova, Italy
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Ceriani F, Mammano F. A rapid and sensitive assay of intercellular coupling by voltage imaging of gap junction networks. Cell Commun Signal 2013; 11:78. [PMID: 24144139 PMCID: PMC3819673 DOI: 10.1186/1478-811x-11-78] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 10/01/2013] [Indexed: 12/16/2022] Open
Abstract
Background A variety of mechanisms that govern connexin channel gating and permeability regulate coupling in gap junction networks. Mutations in connexin genes have been linked to several pathologies, including cardiovascular anomalies, peripheral neuropathy, skin disorders, cataracts and deafness. Gap junction coupling and its patho–physiological alterations are commonly assayed by microinjection experiments with fluorescent tracers, which typically require several minutes to allow dye transfer to a limited number of cells. Comparable or longer time intervals are required by fluorescence recovery after photobleaching experiments. Paired electrophysiological recordings have excellent time resolution but provide extremely limited spatial information regarding network connectivity. Results Here, we developed a rapid and sensitive method to assay gap junction communication using a combination of single cell electrophysiology, large–scale optical recordings and a digital phase–sensitive detector to extract signals with a known frequency from Vf2.1.Cl, a novel fluorescent sensor of plasma membrane potential. Tests performed in HeLa cell cultures confirmed that suitably encoded Vf2.1.Cl signals remained confined within the network of cells visibly interconnected by fluorescently tagged gap junction channels. We used this method to visualize instantly intercellular connectivity over the whole field of view (hundreds of cells) in cochlear organotypic cultures from postnatal mice. A simple resistive network model reproduced accurately the spatial dependence of the electrical signals throughout the cellular network. Our data suggest that each pair of cochlear non−sensory cells of the lesser epithelial ridge is coupled by ~1500 gap junction channels, on average. Junctional conductance was reduced by 14% in cochlear cultures harboring the T5M mutation of connexin30, which induces a moderate hearing loss in connexin30T5M/T5M knock–in mice, and by 91% in cultures from connexin30−/− mice, which are profoundly deaf. Conclusions Our methodology allows greater sensitivity (defined as the minimum magnitude of input signal required to produce a specified output signal having a specified signal−to−noise ratio) and better time resolution compared to classical tracer–based techniques. It permitted us to dynamically visualize intercellular connectivity down to the 10th order in non−sensory cell networks of the developing cochlea. We believe that our approach is of general interest and can be seamlessly extended to a variety of biological systems, as well as to other connexin−related disease conditions.
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Affiliation(s)
| | - Fabio Mammano
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, Padova 35131, Italy.
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Volo T, Sathiyaseelan T, Astolfi L, Guaran V, Trevisi P, Emanuelli E, Martini A. Hair phenotype in non-syndromic deafness. Int J Pediatr Otorhinolaryngol 2013; 77:1280-5. [PMID: 23751281 DOI: 10.1016/j.ijporl.2013.05.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Revised: 05/08/2013] [Accepted: 05/09/2013] [Indexed: 10/26/2022]
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 epidermal tissues. Hence, mutations in GJB2 gene, which is responsible for non-syndromic deafness, may be associated with an abnormal skin and hair phenotype. We analyzed hair samples from 96 subjects: a study group of 42 patients with hearing impairments of genetic origin (38 with a non-syndromic form, 4 with a syndromic form), and a control group including 54 people, i.e. 43 patients with other, non-genetic hearing impairments and 11 healthy volunteers aged up to 10 years old. The surface structure of 49 hair samples was normal, whereas in 45 cases it was altered, with a damaged appearance. Two hair samples were considered unclassifiable: one from the patient heterozygotic for the pendrin mutation (Fig. 2C), the other from a patient from Ghana with a R134W mutation (Fig. 2D). Among the 43 altered hair samples, 31 belonged to patients with connexin mutations and the other 12 came from patients without connexin mutations.
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Affiliation(s)
- T Volo
- Otolaryngology and Otosurgery Unit, University Hospital of Padova, Italy.
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31
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Matos TD, Simões-Teixeira H, Caria H, Gonçalves AC, Chora J, Correia MDC, Moura C, Rosa H, Monteiro L, O'Neill A, Dias Ó, Andrea M, Fialho G. Spectrum and frequency of GJB2 mutations in a cohort of 264 Portuguese nonsyndromic sensorineural hearing loss patients. Int J Audiol 2013; 52:466-71. [PMID: 23668481 DOI: 10.3109/14992027.2013.783719] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE To assess the spectrum and prevalence of mutations in the GJB2 gene in Portuguese nonsyndromic sensorineural hearing loss (NSSHL) patients. DESIGN Sequencing of the coding region, basal promoter, exon 1, and donor splice site of the GJB2 gene; screening for the presence of the two common GJB6 deletions. STUDY SAMPLE A cohort of 264 Portuguese NSSHL patients. RESULTS At least one out of 21 different GJB2 variants was identified in 80 (30.2%) of the 264 patients analysed. Two mutant alleles were found in 53 (20%) of these probands, of which 83% (44/53) harboured at least one c.35delG allele. Twenty-seven (10.2%) of the probands harboured only one mutant allele. Subsequent analysis revealed that the GJB6 deletion del(GJB6-D13S1854) was present in at least 7.4% (2/27) of the patients carrying only one mutant GJB2 allele. Overall, one in five (55/264) of the patients were diagnosed as having DFNB1-related NSSHL, of which the vast majority (53/55) harboured only GJB2 mutations. CONCLUSIONS This study provides clear demonstration that mutations in the GJB2 gene are an important cause of NSSHL in Portugal, thus representing a valuable indicator as regards therapeutical and rehabilitation options, as well as genetic counseling of these patients and their families.
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Affiliation(s)
- Tiago Daniel Matos
- Centre for Biodiversity, Functional, and Integrative Genomics BioFIG, Faculty of Science, University of Lisbon, Lisboa, Portugal
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Löppönen T, Dietz A, Väisänen ML, Valtonen H, Kosunen A, Hyvärinen A, Ignatius J, Löppönen H. Homozygous M34T mutation of the GJB2 gene associates with an autosomal recessive nonsyndromic sensorineural hearing impairment in Finnish families. Acta Otolaryngol 2012; 132:862-73. [PMID: 22668073 DOI: 10.3109/00016489.2012.669498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
CONCLUSION The genetic and audiological data support the hypothesis that the p.M34T is a pathogenic mutation in the Finnish population. The p.M34T mutation displays an autosomal recessive pattern of inheritance and is associated with mild to moderate nonsyndromic sensorineural hearing impairment (SNHI) in the homozygous state. The audiograms often display a hearing impairment notch at 2-4 kHz in young patients, which may aid in the early diagnosis. OBJECTIVES The aim of the study was to assess whether the p.M34T mutation in the GJB2 gene may associate with nonsyndromic SNHI. METHODS We systematically reviewed the families with children diagnosed with nonsyndromic SNHI caused by a homozygous p.M34T mutation at the Kuopio and Oulu University Hospital Clinics. The children were re-examined and audiological and genetic data were obtained from their parents and healthy siblings to study genotype-phenotype correlation. RESULTS We describe 11 patients from 6 families including 5 sibling pairs from 6 to 23 years of age with homozygous p.M34T genotype all having mild nonsyndromic SNHI. In addition, we found three patients with compound p.M34T mutation also exhibiting mild to moderate SNHI.
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Affiliation(s)
- Tuija Löppönen
- Department of Paediatrics, Child Neurology, Kuopio University Hospital, Finland
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Minárik G, Tretinárová D, Szemes T, Kádasi L. Prevalence of DFNB1 mutations in Slovak patients with non-syndromic hearing loss. Int J Pediatr Otorhinolaryngol 2012; 76:400-3. [PMID: 22281373 DOI: 10.1016/j.ijporl.2011.12.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 12/20/2011] [Indexed: 11/24/2022]
Abstract
OBJECTIVES Non-syndromic hearing loss is one of the most common genetically determined diseases in human. The incidence is approximately 1:700 and most of the cases are caused by mutations in specific locus - DFNB1, which contains two genes -GJB2 and GJB6. For the GJB2 gene following mutations are most prevalent in specific populations - 35delG, 235delC, W24X and 167delT for Caucasians, Asians, Indians and Ashkenazi Jews, respectively. Large deletions are common in GJB6 gene. Many other mutations and polymorphisms were found in DFNB1 focused non-syndromic hearing loss studies thus the establishment of optimal screening protocol should be based on population specific mutation screening studies and is an objective in our study. PATIENTS AND METHODS In our study samples from 273 non-syndromic hearing loss patients were screened for mutations in coding and non-coding part of GJB2 gene and large deletion in GJB6 gene - del(GJB6-D13S1830). RESULTS Causal mutation on both chromosomes was detected in 24.57% of patients, another 9.9% carried causal mutation on one chromosome. Totally 7 polymorphisms: V27I, M34T, F83L, 354 C→T, R127H, V153I, 684 C→A and 11 causal mutations: IVS1+1 G→A, 35delG, W24X, V37I, E47X, 167delT, V84M, L90P, 310del14, 333-334delAA, R184Q were detected. No patient carried the GJB6 deletion mutation (del(GJB6-D13S1830)). CONCLUSION According to our results sequencing of GJB2 coding regions and IVS1+1G→A specific detection should explain approximately 25% of sporadic NSHL cases and these two tests are relevant for use as routine screening protocol for NSHL in Slovakia. The GJB6 del(GJB6-D13S1830) mutation was not detected in any of NSHL samples therefore it is not necessary to implement it in our routine screening protocol.
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Affiliation(s)
- Gabriel Minárik
- Institute of Molecular Biomedicine, Comenius University Faculty of Medicine, Bratislava, Slovakia.
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Ek-Vitorin JF, Burt JM. Structural basis for the selective permeability of channels made of communicating junction proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:51-68. [PMID: 22342665 DOI: 10.1016/j.bbamem.2012.02.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 01/24/2012] [Accepted: 02/01/2012] [Indexed: 01/08/2023]
Abstract
The open state(s) of gap junction channels is evident from their permeation by small ions in response to an applied intercellular (transjunctional/transchannel) voltage gradient. That an open channel allows variable amounts of current to transit from cell-to-cell in the face of a constant intercellular voltage difference indicates channel open/closing can be complete or partial. The physiological significance of such open state options is, arguably, the main concern of junctional regulation. Because gap junctions are permeable to many substances, it is sensible to inquire whether and how each open state influences the intercellular diffusion of molecules as valuable as, but less readily detected than current-carrying ions. Presumably, structural changes perceived as shifts in channel conductivity would significantly alter the transjunctional diffusion of molecules whose limiting diameter approximates the pore's limiting diameter. Moreover, changes in junctional permeability to some molecules might occur without evident changes in conductivity, either at macroscopic or single channel level. Open gap junction channels allow the exchange of cytoplasmic permeants between contacting cells by simple diffusion. The identity of such permeants, and the functional circumstances and consequences of their junctional exchange presently constitute the most urgent (and demanding) themes of the field. Here, we consider the necessity for regulating this exchange, the possible mechanism(s) and structural elements likely involved in such regulation, and how regulatory phenomena could be perceived as changes in chemical vs. electrical coupling; an overall reflection on our collective knowledge of junctional communication is then applied to suggest new avenues of research. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.
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Hall A, Pembrey M, Lutman M, Steer C, Bitner-Glindzicz M. Prevalence and audiological features in carriers of GJB2 mutations, c.35delG and c.101T>C (p.M34T), in a UK population study. BMJ Open 2012; 2:bmjopen-2012-001238. [PMID: 22855627 PMCID: PMC3449272 DOI: 10.1136/bmjopen-2012-001238] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVES To determine the carrier rate of the GJB2 mutation c.35delG and c.101T>C in a UK population study; to determine whether carriers of the mutation had worse hearing or otoacoustic emissions compared to non-carriers. DESIGN Prospective cohort study. SETTING University of Bristol, UK. PARTICIPANTS Children in the Avon Longitudinal Study of Parents and Children. 9202 were successfully genotyped for the c.35delG mutation and c.101>T and classified as either carriers or non-carriers. OUTCOME MEASURES Hearing thresholds at age 7, 9 and 11 years and otoacoustic emissions at age 9 and 11. RESULTS The carrier frequency of the c.35delG mutation was 1.36% (95% CI 1.13 to 1.62) and c.101T>C was 2.69% (95% CI 2.37 to 3.05). Carriers of c.35delG and c.101T>C had worse hearing than non-carriers at the extra-high frequency of 16 kHz. The mean difference in hearing at age 7 for the c.35delG mutation was 8.53 dB (95% CI 2.99, 14.07) and 12.57 dB at age 9 (95% CI 8.10, 17.04). The mean difference for c.101T>C at age 7 was 3.25 dB (95% CI -0.25 to 6.75) and 7.61 dB (95% CI 4.26 to 10.96) at age 9. Otoacoustic emissions were smaller in the c.35delG mutation carrier group: at 4 kHz the mean difference was -4.95 dB (95% CI -6.70 to -3.21) at age 9 and -3.94 dB (95% CI -5.78 to -2.10) at age 11. There was weak evidence for differences in otoacoustic emissions amplitude for c.101T>C carriers. CONCLUSION Carriers of the c.35delG mutation and c.101T>C have worse extra-high-frequency hearing than non-carriers. This may be a predictor for changes in lower-frequency hearing in adulthood. The milder effects observed in carriers of c.101T>C are in keeping with its classification as a mutation causing mild/moderate hearing loss in homozygosity or compound heterozygosity.
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Affiliation(s)
- Amanda Hall
- Centre for Hearing and Balance Studies, University of Bristol, Bristol, UK
| | - Marcus Pembrey
- Department of Social and Community Medicine, University of Bristol, Bristol, UK
| | - Mark Lutman
- Institute of Sound and Vibration Research, University of Southampton, Southampton, UK
| | - Colin Steer
- Department of Social and Community Medicine, University of Bristol, Bristol, UK
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Choi SY, Lee KY, Kim HJ, Kim HK, Chang Q, Park HJ, Jeon CJ, Lin X, Bok J, Kim UK. Functional evaluation of GJB2 variants in nonsyndromic hearing loss. Mol Med 2011; 17:550-6. [PMID: 21298213 DOI: 10.2119/molmed.2010.00183] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2010] [Accepted: 01/07/2011] [Indexed: 11/06/2022] Open
Abstract
Mutations in the gap junction β2 (GJB2) gene, encoding the connexin26 (CX26) protein, are the most common cause of non-syndromic hearing loss (HL) in many populations. In the East Asian population, two variants, p.V27I (c.79G>A) and p.E114G (c.341G>A), are considered benign polymorphisms since these variants have been identified in both HL patients and normal hearing controls. However, some studies have postulated that homozygotes carrying both p.V27I and p.E114G variants could cause HL. To elucidate possible roles of these variants, we used in vitro approaches to directly assess the pathogenicity of four haplotypes generated by the two polymorphisms: VE (wild type), I*E (p.V27I variant only), VG* (p.E114G variant only), I*G* (both variants). In biochemical coupling assays, the gap junctions (GJs) composed of VG* and I*G* types displayed defective channel activities compared with those of VE wild types or I*E types, which showed normal channel activities. Interestingly, the defect in hemichannel activity was a bit less severe in I*G* type than VG* type, suggesting that I* variant (p.V27I) may compensate for the deleterious effect of G* variant (p.E114G) in hemichannel activities. Our population studies using 412 Korean individuals showed that I*G* type was detected at around 20% in both HL patients and normal controls, suggesting that I*G* type may not be a pathogenic polymorphism. In contrast, VG* type was very rare (3/824) and detected only in HL patients, suggesting that VG* homozygotes (VG*/VG*) or compound heterozygotes carrying VG* type with other mutations may cause HL.
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Affiliation(s)
- Soo-Young Choi
- Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu, Korea
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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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Schütz M, Scimemi P, Majumder P, De Siati RD, Crispino G, Rodriguez L, Bortolozzi M, Santarelli R, Seydel A, Sonntag S, Ingham N, Steel KP, Willecke K, Mammano F. The human deafness-associated connexin 30 T5M mutation causes mild hearing loss and reduces biochemical coupling among cochlear non-sensory cells in knock-in mice. Hum Mol Genet 2010; 19:4759-73. [PMID: 20858605 PMCID: PMC2989887 DOI: 10.1093/hmg/ddq402] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 08/18/2010] [Accepted: 09/14/2010] [Indexed: 12/11/2022] Open
Abstract
Mutations in the GJB2 and GJB6 genes, respectively, coding for connexin26 (Cx26) and connexin30 (Cx30) proteins, are the most common cause for prelingual non-syndromic deafness in humans. In the inner ear, Cx26 and Cx30 are expressed in different non-sensory cell types, where they largely co-localize and may form heteromeric gap junction channels. Here, we describe the generation and characterization of a mouse model for human bilateral middle/high-frequency hearing loss based on the substitution of an evolutionarily conserved threonine by a methionine residue at position 5 near the N-terminus of Cx30 (Cx30T5M). The mutation was inserted in the mouse genome by homologous recombination in mouse embryonic stem cells. Expression of the mutated Cx30T5M protein in these transgenic mice is under the control of the endogenous Cx30 promoter and was analysed via activation of the lacZ reporter gene. When probed by auditory brainstem recordings, Cx30(T5M/T5M) mice exhibited a mild, but significant increase in their hearing thresholds of about 15 dB at all frequencies. Immunolabelling with antibodies to Cx26 or Cx30 suggested normal location of these proteins in the adult inner ear, but western blot analysis showed significantly down-regulated the expression levels of Cx26 and Cx30. In the developing cochlea, electrical coupling, probed by dual patch-clamp recordings, was normal. However, transfer of the fluorescent tracer calcein between cochlear non-sensory cells was reduced, as was intercellular Ca(2+) signalling due to spontaneous ATP release from connexin hemichannels. Our findings link hearing loss to decreased biochemical coupling due to the point-mutated Cx30 in mice.
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Affiliation(s)
- Melanie Schütz
- Institut fuer Genetik, Rheinische Friedrich-Wilhelms-Universitaet Bonn, Roemerstrasse 164, D-53117 Bonn, Germany
| | - Pietro Scimemi
- Dipartimento di Specialità Medico Chirurgiche, Università di Padova, via Giustiniani 2, 35129 Padova, Italy
- Servizio di Audiologia, Ospedale ‘Ca’ Foncello’, Treviso, Italy
| | - Paromita Majumder
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Romolo Daniele De Siati
- Dipartimento di Specialità Medico Chirurgiche, Università di Padova, via Giustiniani 2, 35129 Padova, Italy
- Servizio di Audiologia, Ospedale ‘Ca’ Foncello’, Treviso, Italy
| | - Giulia Crispino
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Laura Rodriguez
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Mario Bortolozzi
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
- Dipartimento di Fisica ‘G. Galilei’, Università di Padova, 35131 Padova, Italy
- Istituto CNR di Neuroscienze, Padova, Italy and
| | - Rosamaria Santarelli
- Dipartimento di Specialità Medico Chirurgiche, Università di Padova, via Giustiniani 2, 35129 Padova, Italy
- Servizio di Audiologia, Ospedale ‘Ca’ Foncello’, Treviso, Italy
| | - Anke Seydel
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
| | - Stephan Sonntag
- Institut fuer Genetik, Rheinische Friedrich-Wilhelms-Universitaet Bonn, Roemerstrasse 164, D-53117 Bonn, Germany
| | - Neil Ingham
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Karen P. Steel
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Klaus Willecke
- Institut fuer Genetik, Rheinische Friedrich-Wilhelms-Universitaet Bonn, Roemerstrasse 164, D-53117 Bonn, Germany
| | - Fabio Mammano
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, 35129 Padova, Italy
- Dipartimento di Fisica ‘G. Galilei’, Università di Padova, 35131 Padova, Italy
- Istituto CNR di Neuroscienze, Padova, Italy and
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Oshima A, Tani K, Toloue MM, Hiroaki Y, Smock A, Inukai S, Cone A, Nicholson BJ, Sosinsky GE, Fujiyoshi Y. Asymmetric configurations and N-terminal rearrangements in connexin26 gap junction channels. J Mol Biol 2010; 405:724-35. [PMID: 21094651 DOI: 10.1016/j.jmb.2010.10.032] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 10/13/2010] [Accepted: 10/19/2010] [Indexed: 10/18/2022]
Abstract
Gap junction channels are unique in that they possess multiple mechanisms for channel closure, several of which involve the N terminus as a key component in gating, and possibly assembly. Here, we present electron crystallographic structures of a mutant human connexin26 (Cx26M34A) and an N-terminal deletion of this mutant (Cx26M34Adel2-7) at 6-Å and 10-Å resolutions, respectively. The three-dimensional map of Cx26M34A was improved by data from 60° tilt images and revealed a breakdown of the hexagonal symmetry in a connexin hemichannel, particularly in the cytoplasmic domain regions at the ends of the transmembrane helices. The Cx26M34A structure contained an asymmetric density in the channel vestibule ("plug") that was decreased in the Cx26M34Adel2-7 structure, indicating that the N terminus significantly contributes to form this plug feature. Functional analysis of the Cx26M34A channels revealed that these channels are predominantly closed, with the residual electrical conductance showing normal voltage gating. N-terminal deletion mutants with and without the M34A mutation showed no electrical activity in paired Xenopus oocytes and significantly decreased dye permeability in HeLa cells. Comparing this closed structure with the recently published X-ray structure of wild-type Cx26, which is proposed to be in an open state, revealed a radial outward shift in the transmembrane helices in the closed state, presumably to accommodate the N-terminal plug occluding the pore. Because both Cx26del2-7 and Cx26M34Adel2-7 channels are closed, the N terminus appears to have a prominent role in stabilizing the open configuration.
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Affiliation(s)
- Atsunori Oshima
- Department of Biophysics, Faculty of Science, Kyoto University, Oiwake, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
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40
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Rodriguez-Paris J, Pique L, Colen T, Roberson J, Gardner P, Schrijver I. Genotyping with a 198 mutation arrayed primer extension array for hereditary hearing loss: assessment of its diagnostic value for medical practice. PLoS One 2010; 5:e11804. [PMID: 20668687 PMCID: PMC2909915 DOI: 10.1371/journal.pone.0011804] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 07/02/2010] [Indexed: 11/18/2022] Open
Abstract
Molecular diagnostic testing of individuals with congenital sensorineural hearing loss typically begins with DNA sequencing of the GJB2 gene. If the cause of the hearing loss is not identified in GJB2, additional testing can be ordered. However, the step-wise analysis of several genes often results in a protracted diagnostic process. The more comprehensive Hereditary Hearing Loss Arrayed Primer Extension microarray enables analysis of 198 mutations across eight genes (GJB2, GJB6, GJB3, GJA1, SLC26A4, SLC26A5, MTRNR1 and MTTS1) in a single test. To evaluate the added diagnostic value of this microarray for our ethnically diverse patient population, we tested 144 individuals with congenital sensorineural hearing loss who were negative for biallelic GJB2 or GJB6 mutations. The array successfully detected all GJB2 changes previously identified in the study group, confirming excellent assay performance. Additional mutations were identified in the SLC26A4, SLC26A5 and MTRNR1 genes of 12/144 individuals (8.3%), four of whom (2.8%) had genotypes consistent with pathogenicity. These results suggest that the current format of this microarray falls short of adding diagnostic value beyond the customary testing of GJB2, perhaps reflecting the array's limitations on the number of mutations included for each gene, but more likely resulting from unknown genetic contributors to this phenotype. We conclude that mutations in other hearing loss associated genes should be incorporated in the array as knowledge of the etiology of hearing loss evolves. Such future modification of the flexible configuration of the Hereditary Hearing Loss Arrayed Primer Extension microarray would improve its impact as a diagnostic tool.
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Affiliation(s)
- Juan Rodriguez-Paris
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Lynn Pique
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Tahl Colen
- California Ear Institute, Palo Alto, California, United States of America
| | - Joseph Roberson
- California Ear Institute, Palo Alto, California, United States of America
| | - Phyllis Gardner
- Department of Medicine, Stanford University School of Medicine, Stanford, California, United States of America
| | - Iris Schrijver
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
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Reduced electromotility of outer hair cells associated with connexin-related forms of deafness: an in silico study of a cochlear network mechanism. J Assoc Res Otolaryngol 2010; 11:559-71. [PMID: 20635191 DOI: 10.1007/s10162-010-0226-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 06/23/2010] [Indexed: 10/19/2022] Open
Abstract
Mutations in the GJB2 gene encoding for the connexin 26 (Cx26) protein are the most common source of nonsyndromic forms of deafness. Cx26 is a building block of gap junctions (GJs) which establish electrical connectivity in distinct cochlear compartments by allowing intercellular ionic (and metabolic) exchange. Animal models of the Cx26 deficiency in the organ of Corti seem to suggest that the hearing loss and the degeneration of outer hair cells (OHCs) and inner hair cells is due to failed K(+) and metabolite homeostasis. However, OHCs can develop normally in some mutants, suggesting that the hair cells death is not the universal mechanism. In search for alternatives, we have developed an in silico large scale three-dimensional model of electrical current flow in the cochlea in the small signal, linearised, regime. The effect of mutations was analysed by varying the magnitude of resistive components representing the GJ network in the organ of Corti. The simulations indeed show that reduced GJ conductivity increases the attenuation of the OHC transmembrane potential at frequencies above 5 kHz from 6.1 dB/decade in the wild-type to 14.2 dB/decade. As a consequence of increased GJ electrical filtering, the OHC transmembrane potential is reduced by up to 35 dB at frequencies >10 kHz. OHC electromotility, driven by this potential, is crucial for sound amplification, cochlear sensitivity and frequency selectivity. Therefore, we conclude that reduced OHC electromotility may represent an additional mechanism underlying deafness in the presence of Cx26 mutations and may explain lowered OHC functionality in particular reported Cx26 mutants.
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Matos TD, Simões-Teixeira H, Caria H, Rosa H, O'Neill A, Fialho G. The controversial p.Arg127His mutation in GJB2: report on three Portuguese hearing loss family cases. Genet Test Mol Biomarkers 2010; 14:141-4. [PMID: 19929408 DOI: 10.1089/gtmb.2009.0103] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations in the GJB2 gene account for up to 50% of hereditary nonsyndromic hearing loss in several populations. Over 200 mutations are already described in this gene, and three of them, c.35delG, c.167delT, and c.235delC, are the most frequent in Caucasians, Ashkenazi Jews, and Asians, respectively. Most of GJB2 hearing loss-related mutations are recessive, but a few dominant alleles have also been described. Apart from the clearly pathogenic mutations, there are some other variants whose pathogenicity is still controversial, such as p.Met34Thr, p.Val37Ile, p.Arg127His, and p.Val153Ile. The p.Arg127His allele has been found in some mono- and biallelic hearing-impaired patients from several countries. In this article we report on some Portuguese patients harboring this mutation. Taking into consideration the analysis of these Portuguese cases as well as the genetic and functional data regarding p.Arg127His available in the literature, we conclude that this variant may be a cause of hearing loss depending on environmental factors and/or genetic background.
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Affiliation(s)
- Tiago D Matos
- Faculty of Science, Centre for Biodiversity, Functional, and Integrative Genomics (BioFIG), University of Lisbon, Lisbon, Portugal
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Chinetti V, Iossa S, Auletta G, Laria C, de Luca M, Di Leva F, Riccardi P, Giannini P, Gasparini P, Ciccodicola A, Marciano E, Franzè A. Screening forGJB2andGJB6gene mutations in patients from Campania region with sensorineural hearing loss. Int J Audiol 2010; 49:326-31. [DOI: 10.3109/14992021003601756] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Gassmann O, Kreir M, Ambrosi C, Pranskevich J, Oshima A, Röling C, Sosinsky G, Fertig N, Steinem C. The M34A mutant of Connexin26 reveals active conductance states in pore-suspending membranes. J Struct Biol 2009; 168:168-76. [PMID: 19236918 PMCID: PMC2785080 DOI: 10.1016/j.jsb.2009.02.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Revised: 02/09/2009] [Accepted: 02/11/2009] [Indexed: 11/20/2022]
Abstract
Connexin26 (Cx26) is a member of the connexin family, the building blocks for gap junction intercellular channels. These dodecameric assemblies are involved in gap junction-mediated cell-cell communication allowing the passage of ions and small molecules between two neighboring cells. Mutations in Cx26 lead to the disruption of gap junction-mediated intercellular communication with consequences such as hearing loss and skin disorders. We show here that a mutant of Cx26, M34A, forms an active hemichannel in lipid bilayer experiments. A comparison with the Cx26 wild-type is presented. Two different techniques using micro/nano-structured substrates for the formation of pore-suspending lipid membranes are used. We reconstituted the Cx26 wild-type and Cx26M34A into artificial lipid bilayers and observed single channel activity for each technique, with conductance levels of around 35, 70 and 165 pS for the wild-type. The conductance levels of Cx26M34A were found at around 45 and 70 pS.
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Affiliation(s)
- Oliver Gassmann
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Germany
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45
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Dietz A, Löppönen T, Valtonen H, Hyvärinen A, Löppönen H. Prevalence and etiology of congenital or early acquired hearing impairment in Eastern Finland. Int J Pediatr Otorhinolaryngol 2009; 73:1353-7. [PMID: 19616857 DOI: 10.1016/j.ijporl.2009.06.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Revised: 06/17/2009] [Accepted: 06/18/2009] [Indexed: 10/20/2022]
Abstract
OBJECTIVE The purpose of this study was to determine the prevalence and etiology of congenital or early acquired bilateral sensorineural hearing impairment (SNHI) in children born from 1988 to 2002 in the district of Kuopio University Hospital, Finland, and to compare the results with those from an earlier 14-year period in the same region and similar population. METHODS The data were collected retrospectively from Hospital Records. The degree of hearing impairment was based on average air conduction threshold calculated over the frequencies 0.5, 1, 2 and 4 kHz in the better hearing ear. Hearing impairment was classified as mild (≥ 20-39 dB), moderate (40-69 dB), severe (70-95 dB) and profound (>95 dB). RESULTS We identified 92 children with bilateral SNHI diagnosed before the age of 7 years. The overall prevalence and the prevalence for at least moderate SNHI was 2.1 per 1000 live births and 1.2 per 1000 live births, respectively. We found no differences in the prevalence of SNHI during both study periods. Etiology was genetic in 46%, acquired in 14% and unknown in 40%. Out of the genetic cases 74% were non-syndromic and 26% were syndromic. In comparison to the previous study there was a decline in the proportion of acquired SNHI and the proportion of genetic and unknown cause had increased. Six children in five families had homozygous 35delG mutation and six children in four families presented with a homozygous M34T mutation. CONCLUSIONS The prevalence of congenital or early acquired SNHI in the Kuopio University Hospital district area has not changed during a period of 29 years. Despite possibility to test the GBJ2 gene, the proportion of hearing impairment of unknown etiology remained high.
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Affiliation(s)
- Aarno Dietz
- Department of Otorhinolaryngology, Kuopio University Hospital, PO Box 1777, FIN-70211 Kuopio, Finland.
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Berto A, Pellati D, Castiglione A, Busi M, Trevisi P, Gualandi F, Ferlini A, Martini A. Audiological profiles and gjb2, gjb6 mutations: A retrospective study on genetic and clinical data from 2003 to 2008. ACTA ACUST UNITED AC 2009. [DOI: 10.1080/16513860902900136] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Cama E, Melchionda S, Palladino T, Carella M, Santarelli R, Genovese E, Benettazzo F, Zelante L, Arslan E. Hearing loss features in GJB2 biallelic mutations and GJB2/GJB6 digenic inheritance in a large Italian cohort. Int J Audiol 2009; 48:12-7. [DOI: 10.1080/14992020802400654] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Hoang Dinh E, Ahmad S, Chang Q, Tang W, Stong B, Lin X. Diverse deafness mechanisms of connexin mutations revealed by studies using in vitro approaches and mouse models. Brain Res 2009; 1277:52-69. [PMID: 19230829 DOI: 10.1016/j.brainres.2009.02.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2009] [Revised: 02/01/2009] [Accepted: 02/04/2009] [Indexed: 12/12/2022]
Abstract
Mutations in connexins (Cxs), the constitutive protein subunits of gap junction (GJ) intercellular channels, are one of the most common human genetic defects that cause severe prelingual non-syndromic hearing impairments. Many subtypes of Cxs (e.g., Cxs 26, 29, 30, 31, 43) and pannexins (Panxs) are expressed in the cochlea where they contribute to the formation of a GJ-based intercellular communication network. Cx26 and Cx30 are the predominant cochlear Cxs and they co-assemble in most GJ plaques to form hybrid GJs. The cellular localization of specific Cx subtypes provides a basis for understanding the molecular structure of GJs and hemichannels in the cochlea. Information about the interactions among the various co-assembled Cx partners is critical to appreciate the functional consequences of various types of genetic mutations. In vitro studies of reconstituted GJs in cell lines have yielded surprisingly heterogeneous mechanisms of dysfunction caused by various Cx mutations. Availability of multiple lines of Cx-mutant mouse models has provided some insight into the pathogenesis processes in the cochlea of deaf mice. Here we summarize recent advances in understanding the structure and function of cochlear GJs and give a critical review of current findings obtained from both in vitro studies and mouse models on the mechanisms of Cx mutations that lead to cell death in the cochlea and hearing loss.
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Affiliation(s)
- Emilie Hoang Dinh
- Department of Otolaryngology, Emory University School of Medicine, 615 Michael Street, Atlanta, GA 30322-3030, USA
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Martínez AD, Acuña R, Figueroa V, Maripillan J, Nicholson B. Gap-junction channels dysfunction in deafness and hearing loss. Antioxid Redox Signal 2009; 11:309-22. [PMID: 18837651 PMCID: PMC2673109 DOI: 10.1089/ars.2008.2138] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Gap-junction channels connect the cytoplasm of adjacent cells, allowing the diffusion of ions and small metabolites. They are formed at the appositional plasma membranes by a family of related proteins named connexins. Mutations in connexins 26, 31, 30, 32, and 43 have been associated with nonsyndromic or syndromic deafness. The majority of these mutations are inherited in an autosomal recessive manner, but a few of them have been associated with dominantly inherited hearing loss. Mutations in the connexin26 gene (GJB2) are the most common cause of genetic deafness. This review summarizes the most relevant and recent information about different mutations in connexin genes found in human patients, with emphasis on GJB2. The possible effects of the mutations on channel expression and function are discussed, in addition to their possible physiologic consequences for inner ear physiology. Finally, we propose that connexin channels (gap junctions and hemichannels) may be targets for age-related hearing loss induced by oxidative damage.
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Affiliation(s)
- Agustín D Martínez
- Centro de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.
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Gap junctions and connexins in the inner ear: their roles in homeostasis and deafness. Curr Opin Otolaryngol Head Neck Surg 2009; 16:452-7. [PMID: 18797288 DOI: 10.1097/moo.0b013e32830e20b0] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
PURPOSE OF REVIEW Mutations in GJB2 and GJB6, the genes encoding the gap-junction proteins connexin 26 and connexin 30, are the most common cause of autosomal recessive nonsyndromic deafness in many populations across the world. In this review, we discuss current ideas about the roles of gap junctions in the inner ear and the implications of connexin mutations on auditory function. RECENT FINDINGS In recent years, a complex picture of the roles of gap junctions in cochlear physiology emerged. Rather than being mere conduits for the circulation of potassium ions in the inner ear, gap junctions have been implicated in intercellular signaling among nonsensory cells and may be involved in the maintenance of the endothelial barrier in the stria vascularis. Studies of mutant channels and mouse models for connexin-related deafness have provided valuable insights into some of the mechanisms by which connexin dysfunction causes cochlear degeneration. They have also identified potential therapeutic interventions for specific connexin mutations, such as the restoration of normal connexin 26 protein levels in GJB6-associated deafness. SUMMARY Despite recent advances, a better understanding of the complexity of gap-junctional communication in the inner ear and the structure-function relationships of connexin proteins is required for the development of mechanism-based treatments of connexin-associated hearing loss.
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