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Tlili A, Mahfood M, Al Mutery A, Chouchen J. Genetic analysis of 106 sporadic cases with hearing loss in the UAE population. Hum Genomics 2024; 18:59. [PMID: 38844983 PMCID: PMC11157727 DOI: 10.1186/s40246-024-00630-8] [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: 02/03/2024] [Accepted: 05/27/2024] [Indexed: 06/09/2024] Open
Abstract
BACKGROUND Hereditary hearing loss is a rare hereditary condition that has a significant presence in consanguineous populations. Despite its prevalence, hearing loss is marked by substantial genetic diversity, which poses challenges for diagnosis and screening, particularly in cases with no clear family history or when the impact of the genetic variant requires functional analysis, such as in the case of missense mutations and UTR variants. The advent of next-generation sequencing (NGS) has transformed the identification of genes and variants linked to various conditions, including hearing loss. However, there remains a high proportion of undiagnosed patients, attributable to various factors, including limitations in sequencing coverage and gaps in our knowledge of the entire genome, among other factors. In this study, our objective was to comprehensively identify the spectrum of genes and variants associated with hearing loss in a cohort of 106 affected individuals from the UAE. RESULTS In this study, we investigated 106 sporadic cases of hearing impairment and performed genetic analyses to identify causative mutations. Screening of the GJB2 gene in these cases revealed its involvement in 24 affected individuals, with specific mutations identified. For individuals without GJB2 mutations, whole exome sequencing (WES) was conducted. WES revealed 33 genetic variants, including 6 homozygous and 27 heterozygous DNA changes, two of which were previously implicated in hearing loss, while 25 variants were novel. We also observed multiple potential pathogenic heterozygous variants across different genes in some cases. Notably, a significant proportion of cases remained without potential pathogenic variants. CONCLUSIONS Our findings confirm the complex genetic landscape of hearing loss and the limitations of WES in achieving a 100% diagnostic rate, especially in conditions characterized by genetic heterogeneity. These results contribute to our understanding of the genetic basis of hearing loss and emphasize the need for further research and comprehensive genetic analyses to elucidate the underlying causes of this condition.
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Affiliation(s)
- Abdelaziz Tlili
- Department of Applied Biology, College of Sciences, University of Sharjah, Building W8 Room 107, P.O. Box: 27272, Sharjah, United Arab Emirates.
- Human Genetics and Stem Cell Laboratory, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah, United Arab Emirates.
| | - Mona Mahfood
- Department of Applied Biology, College of Sciences, University of Sharjah, Building W8 Room 107, P.O. Box: 27272, Sharjah, United Arab Emirates
| | - Abdullah Al Mutery
- Department of Applied Biology, College of Sciences, University of Sharjah, Building W8 Room 107, P.O. Box: 27272, Sharjah, United Arab Emirates
| | - Jihen Chouchen
- Human Genetics and Stem Cell Laboratory, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah, United Arab Emirates
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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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Buratto D, Saxena A, Ji Q, Yang G, Pantano S, Zonta F. Rapid Assessment of Binding Affinity of SARS-COV-2 Spike Protein to the Human Angiotensin-Converting Enzyme 2 Receptor and to Neutralizing Biomolecules Based on Computer Simulations. Front Immunol 2021; 12:730099. [PMID: 34858396 PMCID: PMC8632240 DOI: 10.3389/fimmu.2021.730099] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 10/25/2021] [Indexed: 12/17/2022] Open
Abstract
SARS-CoV-2 infects humans and causes Coronavirus disease 2019 (COVID-19). The S1 domain of the spike glycoprotein of SARS-CoV-2 binds to human angiotensin-converting enzyme 2 (hACE2) via its receptor-binding domain, while the S2 domain facilitates fusion between the virus and the host cell membrane for entry. The spike glycoprotein of circulating SARS-CoV-2 genomes is a mutation hotspot. Some mutations may affect the binding affinity for hACE2, while others may modulate S-glycoprotein expression, or they could result in a virus that can escape from antibodies generated by infection with the original variant or by vaccination. Since a large number of variants are emerging, it is of vital importance to be able to rapidly assess their characteristics: while changes of binding affinity alone do not always cause direct advantages for the virus, they still can provide important insights on where the evolutionary pressure is directed. Here, we propose a simple and cost-effective computational protocol based on Molecular Dynamics simulations to rapidly screen the ability of mutated spike protein to bind to the hACE2 receptor and selected neutralizing biomolecules. Our results show that it is possible to achieve rapid and reliable predictions of binding affinities. A similar approach can be used to perform preliminary screenings of the potential effects of S-RBD mutations, helping to prioritize the more time-consuming and expensive experimental work.
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Affiliation(s)
- Damiano Buratto
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
| | - Abhishek Saxena
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
| | - Qun Ji
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
| | - Guang Yang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
| | - Sergio Pantano
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
- Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Francesco Zonta
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
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4
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Mahfood M, Chouchen J, Kamal Eddine Ahmad Mohamed W, Al Mutery A, Harati R, Tlili A. Whole exome sequencing, in silico and functional studies confirm the association of the GJB2 mutation p.Cys169Tyr with deafness and suggest a role for the TMEM59 gene in the hearing process. Saudi J Biol Sci 2021; 28:4421-4429. [PMID: 34354426 PMCID: PMC8324942 DOI: 10.1016/j.sjbs.2021.04.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 04/11/2021] [Accepted: 04/12/2021] [Indexed: 12/25/2022] Open
Abstract
The development of next generation sequencing techniques has facilitated the detection of mutations at an unprecedented rate. These efficient tools have been particularly beneficial for extremely heterogeneous disorders such as autosomal recessive non-syndromic hearing loss, the most common form of genetic deafness. GJB2 mutations are the most common cause of hereditary hearing loss. Amongst them the NM_004004.5: c.506G > A (p.Cys169Tyr) mutation has been associated with varying severity of hearing loss with unclear segregation patterns. In this study, we report a large consanguineous Emirati family with severe to profound hearing loss fully segregating the GJB2 missense mutation p.Cys169Tyr. Whole exome sequencing (WES), in silico, splicing and expression analyses ruled out the implication of any other variants and confirmed the implication of the p.Cys169Tyr mutation in this deafness family. We also show preliminary murine expression analysis that suggests a link between the TMEM59 gene and the hearing process. The present study improves our understanding of the molecular pathogenesis of hearing loss. It also emphasizes the significance of combining next generation sequencing approaches and segregation analyses especially in the diagnosis of disorders characterized by complex genetic heterogeneity.
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Key Words
- ARNSHL, autosomal recessive non-syndromic hearing loss
- Actb, Actin beta
- BAM, Binary Alignment Map
- BWA, Burrows-Wheeler Aligner
- C1QTNF9, C1q and TNF related 9
- Cx26, Connexin 26
- ESRRAP2, Estrogen-Related Receptor Alpha Pseudogene 2
- GJB2 gene
- GJB2, Gap Junction Protein Beta 2
- HHLA1, HERV-H LTR-Associating 1
- HL, Hearing loss
- KCNQ3, Potassium Voltage-Gated Channel Subfamily Q Member 3
- Missense mutation
- NGS, next generation sequencing
- NSHL, Non-syndromic hearing loss
- Non-syndromic hearing loss
- PROVEAN, Protein Variation Effect Analyzer
- PolyPhen-2, Polymorphism Phenotyping v2
- RFLP, restriction fragment length polymorphism
- ROH, runs of homozygosity
- RT-PCR, reverse transcription PCR
- RT-qPCR, quantitative reverse transcription PCR
- SAM, Sequence Alignment/Map
- SIFT, Sorting Intolerant From Tolerant
- SJL, Swiss Jim Lambert
- SPATA13, Spermatogenesis Associated 13
- ST3GAL1, ST3 Beta-Galactoside Alpha-2,3-Sialyltransferase 1
- TMEM59, Transmembrane Protein 59
- UAE, United Arab Emirates
- VariMAT, Variation and Mutation Annotation Toolkit
- WES, Whole exome sequencing
- Whole exome sequencing
- dpSNP, Single Nucleotide Polymorphism Database
- gEAR, gene Expression Analysis Resource
- gnomAD, genome aggregation database
- qPCR, quantitative PCR
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Affiliation(s)
- Mona Mahfood
- Department of Applied Biology, College of Sciences, University of Sharjah, Sharjah, United Arab Emirates
| | - Jihen Chouchen
- Human Genetics and Stem Cell Research Group, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah, United Arab Emirates
| | - Walaa Kamal Eddine Ahmad Mohamed
- Human Genetics and Stem Cell Research Group, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah, United Arab Emirates
| | - Abdullah Al Mutery
- Department of Applied Biology, College of Sciences, University of Sharjah, Sharjah, United Arab Emirates.,Human Genetics and Stem Cell Research Group, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah, United Arab Emirates
| | - Rania Harati
- Department of Pharmacy Practice and Pharmacotherapeutics, College of Pharmacy, University of Sharjah, Sharjah, United Arab Emirates
| | - Abdelaziz Tlili
- Department of Applied Biology, College of Sciences, University of Sharjah, Sharjah, United Arab Emirates.,Human Genetics and Stem Cell Research Group, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah, United Arab Emirates
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5
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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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6
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Calligari P, Torsello M, Bortoli M, Orian L, Polimeno A. Modelling of Ca2+-promoted structural effects in wild type and post-translationally modified Connexin26. MOLECULAR SIMULATION 2019. [DOI: 10.1080/08927022.2019.1690653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Paolo Calligari
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Padova, Italy
| | - Mauro Torsello
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Padova, Italy
| | - Marco Bortoli
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Padova, Italy
| | - Laura Orian
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Padova, Italy
| | - Antonino Polimeno
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Padova, Italy
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7
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Youssefian L, Vahidnezhad H, Saeidian AH, Mahmoudi H, Karamzadeh R, Kariminejad A, Huang J, Li L, Jannace TF, Fortina P, Zeinali S, White TW, Uitto J. A novel autosomal recessive GJB2-associated disorder: Ichthyosis follicularis, bilateral severe sensorineural hearing loss, and punctate palmoplantar keratoderma. Hum Mutat 2018; 40:217-229. [PMID: 30431684 DOI: 10.1002/humu.23686] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/26/2018] [Accepted: 10/30/2018] [Indexed: 11/07/2022]
Abstract
Ichthyosis follicularis, a distinct cutaneous entity reported in combination with atrichia, and photophobia has been associated with mutations in MBTPS2. We sought the genetic cause of a novel syndrome of ichthyosis follicularis, bilateral severe sensorineural hearing loss and punctate palmoplantar keratoderma in two families. We performed whole exome sequencing on three patients from two families. The pathogenicity and consequences of mutations were studied in the Xenopus oocyte expression system and by molecular modeling analysis. Compound heterozygous mutations in the GJB2 gene were discovered: a pathogenic c.526A>G; p.Asn176Asp, and a common frameshift mutation, c.35delG; p.Gly12Valfs*2. The p.Asn176Asp missense mutation was demonstrated to significantly reduce the cell-cell gap junction channel activity and increase the nonjunctional hemichannel activity in the Xenopus oocyte expression system. Molecular modeling analyses of the mutant Cx26 protein revealed significant changes in the structural characteristics and electrostatic potential of the Cx26, either in hemichannel or gap junction conformation. Thus, association of a new syndrome of an autosomal recessive disorder of ichthyosis follicularis, bilateral severe sensorineural hearing loss and punctate palmoplantar keratoderma with mutations in GJB2, expands the phenotypic spectrum of the GJB2-associated disorders. The findings attest to the complexity of the clinical consequences of different mutations in GJB2.
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Affiliation(s)
- Leila Youssefian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
- Genetics, Genomics and Cancer Biology PhD Program, Thomas Jefferson University, Philadelphia, PA, USA
| | - Hassan Vahidnezhad
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
- Biotechnology Research Center, Department of Molecular Medicine, Pasteur Institute of Iran, Tehran, Iran
| | - Amir Hossein Saeidian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
- Genetics, Genomics and Cancer Biology PhD Program, Thomas Jefferson University, Philadelphia, PA, USA
| | - Hamidreza Mahmoudi
- Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Razieh Karamzadeh
- Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
| | | | - Jianhe Huang
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
| | - Leping Li
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Thomas F Jannace
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Paolo Fortina
- Department of Cancer Biology, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA
- Department of Molecular Medicine, Sapienza University, Rome, Italy
| | - Sirous Zeinali
- Biotechnology Research Center, Department of Molecular Medicine, Pasteur Institute of Iran, Tehran, Iran
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA, USA
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8
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Missoum A. The role of gene GJB2 and connexin 26 in hearing impairment. UKRAINIAN BIOCHEMICAL JOURNAL 2018. [DOI: 10.15407/ubj90.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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9
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Zonta F, Buratto D, Crispino G, Carrer A, Bruno F, Yang G, Mammano F, Pantano S. Cues to Opening Mechanisms From in Silico Electric Field Excitation of Cx26 Hemichannel and in Vitro Mutagenesis Studies in HeLa Transfectans. Front Mol Neurosci 2018; 11:170. [PMID: 29904340 PMCID: PMC5990870 DOI: 10.3389/fnmol.2018.00170] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 05/04/2018] [Indexed: 01/06/2023] Open
Abstract
Connexin channels play numerous essential roles in virtually every organ by mediating solute exchange between adjacent cells, or between cytoplasm and extracellular milieu. Our understanding of the structure-function relationship of connexin channels relies on X-ray crystallographic data for human connexin 26 (hCx26) intercellular gap junction channels. Comparison of experimental data and molecular dynamics simulations suggests that the published structures represent neither fully-open nor closed configurations. To facilitate the search for alternative stable configurations, we developed a coarse grained (CG) molecular model of the hCx26 hemichannel and studied its responses to external electric fields. When challenged by a field of 0.06 V/nm, the hemichannel relaxed toward a novel configuration characterized by a widened pore and an increased bending of the second transmembrane helix (TM2) at the level of the conserved Pro87. A point mutation that inhibited such transition in our simulations impeded hemichannel opening in electrophysiology and dye uptake experiments conducted on HeLa tranfectants. These results suggest that the hCx26 hemichannel uses a global degree of freedom to transit between different configuration states, which may be shared among the whole connexin family.
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Affiliation(s)
- Francesco Zonta
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China.,CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Damiano Buratto
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China.,CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Physics and Astronomy "G. Galilei", University of Padua, Padua, Italy
| | - Giulia Crispino
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Physics and Astronomy "G. Galilei", University of Padua, Padua, Italy.,Venetian Institute of Molecular Medicine, Padua, Italy
| | - Andrea Carrer
- CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Physics and Astronomy "G. Galilei", University of Padua, Padua, Italy.,Department of Biomedical Sciences, University of Padua, Padua, Italy
| | | | - Guang Yang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
| | - Fabio Mammano
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China.,CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy.,Department of Physics and Astronomy "G. Galilei", University of Padua, Padua, Italy.,Venetian Institute of Molecular Medicine, Padua, Italy
| | - Sergio Pantano
- Group of Biomolecular Simulations, Institut Pasteur de Montevideo, Montevideo, Uruguay
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10
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Tlili A, Al Mutery A, Kamal Eddine Ahmad Mohamed W, Mahfood M, Hadj Kacem H. Prevalence of GJB2 Mutations in Affected Individuals from United Arab Emirates with Autosomal Recessive Nonsyndromic Hearing Loss. Genet Test Mol Biomarkers 2017; 21:686-691. [PMID: 29016196 DOI: 10.1089/gtmb.2017.0130] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AIM Mutations in the gap junction protein beta 2 (GJB2) gene are responsible for more cases of nonsyndromic recessive hearing loss than any other gene. The purpose of our study was to evaluate the prevalence of GJB2 mutations among affected individuals from United Arab Emirates (UAE). METHODS There were 50 individuals diagnosed with hereditary hearing loss and 120 healthy individuals enrolled in the study. The Sanger sequencing method was used to screen the GJB2 coding region in all affected individuals. The c.-1G>A variant was determined by the polymerase chain reaction-restriction fragment length polymorphism method in normal individuals. RESULTS AND DISCUSSION Nine cases with bi-allelic mutations and three cases with mono-allelic mutations were detected in 12 out of 50 patients (24%). The homozygous mutation c.35delG was identified as the cause of hearing loss in six participants (12%). The mutation c.506G>A was identified in three affected individuals (6%). The allelic frequency (14%) and low percentage of individuals that were homozygous (2%) for the c.35delG mutation suggest that there are other genes responsible for nonsyndromic deafness in the UAE population. The results reported here are a preliminary step in collecting epidemiological data regarding autosomal recessive nonsyndromic hearing loss related to GJB2 gene mutations among the UAE population. CONCLUSION The c.35delG mutation of the GJB2 gene is the most frequently seen causative mutation in the UAE and is followed by the p.Cys169Tyr mutation.
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Affiliation(s)
- Abdelaziz Tlili
- 1 Department of Applied Biology, College of Sciences, University of Sharjah , Sharjah, United Arab Emirates .,2 Human Genetics and Stem Cell Laboratory, Research Institute of Sciences and Engineering, University of Sharjah , Sharjah, United Arab Emirates
| | - Abdullah Al Mutery
- 1 Department of Applied Biology, College of Sciences, University of Sharjah , Sharjah, United Arab Emirates
| | | | - Mona Mahfood
- 1 Department of Applied Biology, College of Sciences, University of Sharjah , Sharjah, United Arab Emirates
| | - Hassen Hadj Kacem
- 1 Department of Applied Biology, College of Sciences, University of Sharjah , Sharjah, United Arab Emirates .,2 Human Genetics and Stem Cell Laboratory, Research Institute of Sciences and Engineering, University of Sharjah , Sharjah, United Arab Emirates
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11
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Vicario M, Calì T, Cieri D, Vallese F, Bortolotto R, Lopreiato R, Zonta F, Nardella M, Micalizzi A, Lefeber DJ, Valente EM, Bertini E, Zanotti G, Zanni G, Brini M, Carafoli E. A novel PMCA3 mutation in an ataxic patient with hypomorphic phosphomannomutase 2 (PMM2) heterozygote mutations: Biochemical characterization of the pump defect. Biochim Biophys Acta Mol Basis Dis 2017; 1863:3303-3312. [PMID: 28807751 DOI: 10.1016/j.bbadis.2017.08.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 07/28/2017] [Accepted: 08/09/2017] [Indexed: 11/28/2022]
Abstract
The neuron-restricted isoform 3 of the plasma membrane Ca2+ ATPase plays a major role in the regulation of Ca2+ homeostasis in the brain, where the precise control of Ca2+ signaling is a necessity. Several function-affecting genetic mutations in the PMCA3 pump associated to X-linked congenital cerebellar ataxias have indeed been described. Interestingly, the presence of co-occurring mutations in additional genes suggest their synergistic action in generating the neurological phenotype as digenic modulators of the role of PMCA3 in the pathologies. Here we report a novel PMCA3 mutation (G733R substitution) in the catalytic P-domain of the pump in a patient affected by non-progressive ataxia, muscular hypotonia, dysmetria and nystagmus. Biochemical studies of the pump have revealed impaired ability to control cellular Ca2+ handling both under basal and under stimulated conditions. A combined analysis by homology modeling and molecular dynamics have revealed a role for the mutated residue in maintaining the correct 3D configuration of the local structure of the pump. Mutation analysis in the patient has revealed two additional function-impairing compound heterozygous missense mutations (R123Q and G214S substitution) in phosphomannomutase 2 (PMM2), a protein that catalyzes the isomerization of mannose 6-phosphate to mannose 1-phosphate. These mutations are known to be associated with Type Ia congenital disorder of glycosylation (PMM2-CDG), the most common group of disorders of N-glycosylation. The findings highlight the association of PMCA3 mutations to cerebellar ataxia and strengthen the possibility that PMCAs act as digenic modulators in Ca2+-linked pathologies.
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Affiliation(s)
- Mattia Vicario
- Department of Biomedical Sciences, University of Padova, 35131 Padova, (Italy)
| | - Tito Calì
- Department of Biomedical Sciences, University of Padova, 35131 Padova, (Italy)
| | - Domenico Cieri
- Department of Biomedical Sciences, University of Padova, 35131 Padova, (Italy)
| | - Francesca Vallese
- Department of Biomedical Sciences, University of Padova, 35131 Padova, (Italy)
| | - Raissa Bortolotto
- Department of Biomedical Sciences, University of Padova, 35131 Padova, (Italy)
| | - Raffaele Lopreiato
- Department of Biomedical Sciences, University of Padova, 35131 Padova, (Italy)
| | - Francesco Zonta
- Shanghai Institute of Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China; Department of Biomedical Sciences, Institute of Cell Biology and Neurobiology, Italian National Research Council, 00015, Monterotondo, Rome, Italy
| | - Marta Nardella
- Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | | | - Dirk J Lefeber
- Department of Neurology, Translational Metabolic Laboratory, Donders Institute for Brain, Cognition, and Behavior, Radboudumc, Nijmegen, The Netherlands
| | - Enza Maria Valente
- Neurogenetics Unit, IRCCS Santa Lucia Foundation, Rome, Italy; Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Enrico Bertini
- Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Giuseppe Zanotti
- Department of Biomedical Sciences, University of Padova, 35131 Padova, (Italy)
| | - Ginevra Zanni
- Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
| | - Marisa Brini
- Department of Biology, University of Padova, Italy.
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Cianci M, Folli C, Zonta F, Florio P, Berni R, Zanotti G. Structural evidence for asymmetric ligand binding to transthyretin. ACTA ACUST UNITED AC 2015; 71:1582-92. [DOI: 10.1107/s1399004715010585] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 06/01/2015] [Indexed: 12/22/2022]
Abstract
Human transthyretin (TTR) represents a notable example of an amyloidogenic protein, and several compounds that are able to stabilize its native state have been proposed as effective drugs in the therapy of TTR amyloidosis. The two thyroxine (T4) binding sites present in the TTR tetramer display negative binding cooperativity. Here, structures of TTR in complex with three natural polyphenols (pterostilbene, quercetin and apigenin) have been determined, in which this asymmetry manifests itself as the presence of a main binding site with clear ligand occupancy and related electron density and a second minor site with a much lower ligand occupancy. The results of an analysis of the structural differences between the two binding sites are consistent with such a binding asymmetry. The different ability of TTR ligands to saturate the two T4 binding sites of the tetrameric protein can be ascribed to the different affinity of ligands for the weaker binding site. In comparison, the high-affinity ligand tafamidis, co-crystallized under the same experimental conditions, was able to fully saturate the two T4 binding sites. This asymmetry is characterized by the presence of small but significant differences in the conformation of the cavity of the two binding sites. Molecular-dynamics simulations suggest the presence of even larger differences in solution. Competition binding assays carried out in solution revealed the presence of a preferential binding site in TTR for the polyphenols pterostilbene and quercetin that was different from the preferential binding site for T4. The TTR binding asymmetry could possibly be exploited for the therapy of TTR amyloidosis by using a cocktail of two drugs, each of which exhibits preferential binding for a distinct binding site, thus favouring saturation of the tetrameric protein and consequently its stabilization.
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