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Yan D, Nawab A, Smeal M, Liu XZ. Etiologic Diagnosis of Genetic Hearing Loss in an Ethnically Diverse Deafness Cohort. Audiol Neurootol 2024:1-10. [PMID: 39182490 DOI: 10.1159/000540202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 06/25/2024] [Indexed: 08/27/2024] Open
Abstract
INTRODUCTION Hearing loss is a common sensory disorder that impacts patients across the lifespan. Many genetic variants have been identified that contribute to non-syndromic hearing loss. Yet, genetic testing is not routinely administered when hearing loss is diagnosed, particularly in adults. In this study, genetic testing was completed in patients with known hearing loss. METHODS A total of 104 patients who were evaluated for hearing loss were enrolled and received genetic testing. RESULTS Of those 104 patients, 39 had available genetic testing, 20 had one missing allele, and 45 yielded no genetic diagnosis. Of the 39 cases with genetic testing data, 24 were simplex cases, and 15 were multiplex cases. A majority of patients presented with an autosomal recessive inheritance pattern (n = 32), 26 of whom presented with congenital hearing loss. 38% of cases were positive for GJB2 mutation with c.35delG being the most common pathogenic variant. These findings are consistent with previous literature suggesting GJB2 mutations are the most common causes of non-syndromic hearing loss. CONCLUSION Given the frequency of genetic variants in patients with hearing loss, genetic testing should be considered a routine part of the hearing loss work-up, particularly as gene therapies are studied and become more widely available. LAY SUMMARY Many genetic variants have been identified that contribute to non-syndromic hearing loss. Given the frequency of genetic variants in patients with hearing loss, genetic testing should be considered a routine part of the hearing loss work-up.
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Affiliation(s)
- Denise Yan
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Aria Nawab
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida, USA,
| | - Molly Smeal
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Xue-Zhong Liu
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida, USA
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Wener ER, McLennan JD, Papsin BC, Cushing SL, Stavropoulos DJ, Mendoza-Londono R, Quercia N, Gordon KA. Variants in Genes Associated with Hearing Loss in Children: Prevalence in a Large Canadian Cohort. Laryngoscope 2024; 134:3832-3838. [PMID: 38426810 DOI: 10.1002/lary.31373] [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: 07/20/2023] [Revised: 01/17/2024] [Accepted: 02/02/2024] [Indexed: 03/02/2024]
Abstract
OBJECTIVE The objective of this study was to assess the prevalence of genetic variants associated with hearing loss in a large cohort of children in Canada using high throughput next generation sequencing (NGS). METHODS A total of 485 children with hearing loss underwent NGS testing with an 80 gene panel of syndromic and non-syndromic variants known to be associated with hearing loss. Genetic variants were classified as pathogenic, likely pathogenic, likely benign, benign, or variants of uncertain significance (VUS), according to the American College of Medical Genetics and Genomics guidelines. RESULTS Across the 80 genes tested, 923 variants, predominantly in 28 genes, were identified in 324 children. Pathogenic variants occurred in 19/80 (23.8%) of the hearing loss related genes tested and confirmed the etiology of hearing loss in 73/485 (15.1%) of children. GJB2 was the most prevalent gene, affecting 28/73 (38.4%) children with confirmed genetic hearing loss in our cohort. Most identified variants (748/923, 81.0%, in 76/80 genes) were of uncertain significance. CONCLUSION Genetic testing using NGS identified the etiology in approximately 15% of childhood hearing loss in a Canadian cohort which is lower than what is typically reported. GJB2 was the most common genetic cause of hearing loss. VUS are commonly identified, presenting clinical challenges for counseling. LEVEL OF EVIDENCE 4 Laryngoscope, 134:3832-3838, 2024.
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Affiliation(s)
- Emily R Wener
- Archie's Cochlear Implant Laboratory, Neuroscience & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Jacob D McLennan
- Archie's Cochlear Implant Laboratory, Neuroscience & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Blake C Papsin
- Archie's Cochlear Implant Laboratory, Neuroscience & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Otolaryngology-Head and Neck Surgery, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Sharon L Cushing
- Archie's Cochlear Implant Laboratory, Neuroscience & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Otolaryngology-Head and Neck Surgery, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Dimitri James Stavropoulos
- Genome Diagnostics Paediatric Laboratory Medicine, Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Roberto Mendoza-Londono
- Genome Diagnostics Paediatric Laboratory Medicine, Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Nada Quercia
- Division of Clinical & Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Genetic Counselling, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Karen A Gordon
- Archie's Cochlear Implant Laboratory, Neuroscience & Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Otolaryngology-Head and Neck Surgery, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada
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3
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Kabahuma RI, Schubert W, Labuschagne C, Yan D, Pepper MS, Liu X. Elucidation of repeat motifs R1- and R2-related TRIOBP variants in autosomal recessive nonsyndromic hearing loss DFNB28 among indigenous South African individuals. Mol Genet Genomic Med 2022; 10:e2015. [PMID: 36029164 PMCID: PMC9544205 DOI: 10.1002/mgg3.2015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 06/10/2022] [Accepted: 06/28/2022] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND DFNB28, a recessively inherited nonsyndromic form of deafness in humans, is caused by mutations in the TRIOBP gene (MIM #609761) on chromosome 22q13. Its protein TRIOBP helps to tightly bundle F-actin filaments, forming a rootlet that penetrates through the cuticular plate into the cochlear hair cell body. Repeat motifs R1 and R2, located in exon 7 of the TRIOBP-5 isoform, are the actin-binding domains. Deletion of both repeat motifs R1 and R2 results in complete disruption of both actin-binding and bundling activities, whereas deletion of the R2 motif alone retains F-actin bundling ability in stereocilia rootlets. METHODS Target sequencing, using a custom capture panel of 180 known and candidate genes associated with sensorineural hearing loss, bioinformatics processing, and data analysis were performed. Genesis 2.0 was used for variant filtering based on quality/score read depth and minor allele frequency (MAF) thresholds of 0.005 for recessive NSHL, as reported in population-based sequencing databases. All variants were reclassified based on the American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology (AMP) guidelines together with other variant interpretation guidelines for genetic hearing loss . Candidate variants were confirmed via Sanger sequencing according to standard protocols, using the ABIPRISM 3730 DNA Analyzer. DNA sequence analysis was performed with DNASTAR Lasergene software. RESULTS Candidate TRIOBP variants identified among 94 indigenous sub-Saharan African individuals were characterized through segregation analysis. Family TS005 carrying variants c.572delC, p.Pro191Argfs*50, and c.3510_3513dupTGCA, p.Pro1172Cysfs*13, demonstrated perfect cosegregation with the deafness phenotype. On the other hand, variants c.505C > A p.Asp168Glu and c.3636 T > A p.Leu1212Gln in the same family did not segregate with deafness and we have classified these variants as benign. A control family, TS067, carrying variants c.2532G > T p.Leu844Arg, c.2590C > A p.Asn867Lys, c.3484C > T p.Pro1161Leu, and c.3621 T > C p.Phe1187Leu demonstrated no cosegregation allowing us to classify these variants as benign. Together with published TRIOBP variants, the results showed that genotypes combining two truncating TRIOBP variants affecting repeat motifs R1 and R2 or R2 alone lead to a deafness phenotype, while a truncating variant affecting repeat motifs R1 and R2 or R2 alone combined with a missense variant does not. Homozygous truncating variants affecting repeat motif R2 cosegregate with the deafness phenotype. CONCLUSION While a single intact R1 motif may be adequate for actin-binding and bundling in the stereocilia of cochlear hair cells, our findings indicate that a truncated R2 motif in cis seems to be incompatible with normal hearing, either by interfering with the function of an intact R1 motif or through another as yet unknown mechanism. Our study also suggests that most heterozygous missense variants involving exon 7 are likely to be tolerated.
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Affiliation(s)
- Rosemary Ida Kabahuma
- Department of OtorhinolaryngologyUniversity of PretoriaPretoriaSouth Africa,Departments of Biochemistry, Genetics and Microbiology, Faculty of Natural and Agricultural SciencesUniversity of PretoriaPretoriaSouth Africa
| | - Wolf‐Dieter Schubert
- Departments of Biochemistry, Genetics and Microbiology, Faculty of Natural and Agricultural SciencesUniversity of PretoriaPretoriaSouth Africa
| | | | - Denise Yan
- Department of OtolaryngologyUniversity of Miami Miller School of MedicineMiamiFloridaUSA
| | - Michael Sean Pepper
- Institute for Cellular and Molecular Medicine, Department of Immunology and SAMRC Extramural Unit for Stem Cell Research and Therapy, Faculty of Health SciencesUniversity of PretoriaPretoriaSouth Africa
| | - Xue‐Zhong Liu
- Department of OtolaryngologyUniversity of Miami Miller School of MedicineMiamiFloridaUSA
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Dia Y, Adadey SM, Diop JPD, Aboagye ET, Ba SA, De Kock C, Ly CAT, Oluwale OG, Sène ARG, Sarr PD, Diallo BK, Diallo RN, Wonkam A. GJB2 Is a Major Cause of Non-Syndromic Hearing Impairment in Senegal. BIOLOGY 2022; 11:795. [PMID: 35625523 PMCID: PMC9138795 DOI: 10.3390/biology11050795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 05/16/2022] [Accepted: 05/17/2022] [Indexed: 11/29/2022]
Abstract
This study aimed to investigate GJB2 (MIM: 121011) and GJB6 (MIM: 604418) variants associated with familial non-syndromic hearing impairment (HI) in Senegal. We investigated a total of 129 affected and 143 unaffected individuals from 44 multiplex families by segregating autosomal recessive non-syndromic HI, 9 sporadic HI cases of putative genetic origin, and 148 control individuals without personal or family history of HI. The DNA samples were screened for GJB2 coding-region variants and GJB6-D3S1830 deletions. The mean age at the medical diagnosis of the affected individuals was 2.93 ± 2.53 years [range: 1−15 years]. Consanguinity was present in 40 out of 53 families (75.47%). Variants in GJB2 explained HI in 34.1% (n = 15/44) of multiplex families. A bi-allelic pathogenic variant, GJB2: c.94C>T: p.(Arg32Cys) accounted for 25% (n = 11/44 families) of familial cases, of which 80% (n = 12/15) were consanguineous. Interestingly, the previously reported “Ghanaian” founder variant, GJB2: c.427C>T: p.(Arg143Trp), accounted for 4.5% (n = 2/44 families) of the families investigated. Among the normal controls, the allele frequency of GJB2: c.94C>T and GJB2: c.427C>T was estimated at 1% (2/148 ∗ 2) and 2% (4/148 ∗ 2), respectively. No GJB6-D3S1830 deletion was identified in any of the HI patients. This is the first report of a genetic investigation of HI in Senegal, and suggests that GJB2: c.94C>T: p.(Arg32Cys) and GJB2: c.427C>T: p.(Arg143Trp) should be tested in clinical practice for congenital HI in Senegal.
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Affiliation(s)
- Yacouba Dia
- Division of Human Genetics, Faculty of Medicine, Pharmacy and Odontology, University Cheikh Anta Diop (UCAD), Dakar 10700, Senegal; (Y.D.); (J.P.D.D.); (S.A.B.); (C.A.T.L.); (A.R.G.S.); (P.D.S.), (R.N.D.)
| | - Samuel Mawuli Adadey
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa; (S.M.A.); (E.T.A.); (C.D.K.); (O.G.O.)
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Legon, Accra P.O. Box LG 54, Ghana
| | - Jean Pascal Demba Diop
- Division of Human Genetics, Faculty of Medicine, Pharmacy and Odontology, University Cheikh Anta Diop (UCAD), Dakar 10700, Senegal; (Y.D.); (J.P.D.D.); (S.A.B.); (C.A.T.L.); (A.R.G.S.); (P.D.S.), (R.N.D.)
| | - Elvis Twumasi Aboagye
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa; (S.M.A.); (E.T.A.); (C.D.K.); (O.G.O.)
| | - Seydi Abdoul Ba
- Division of Human Genetics, Faculty of Medicine, Pharmacy and Odontology, University Cheikh Anta Diop (UCAD), Dakar 10700, Senegal; (Y.D.); (J.P.D.D.); (S.A.B.); (C.A.T.L.); (A.R.G.S.); (P.D.S.), (R.N.D.)
| | - Carmen De Kock
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa; (S.M.A.); (E.T.A.); (C.D.K.); (O.G.O.)
| | - Cheikh Ahmed Tidjane Ly
- Division of Human Genetics, Faculty of Medicine, Pharmacy and Odontology, University Cheikh Anta Diop (UCAD), Dakar 10700, Senegal; (Y.D.); (J.P.D.D.); (S.A.B.); (C.A.T.L.); (A.R.G.S.); (P.D.S.), (R.N.D.)
| | - Oluwafemi Gabriel Oluwale
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa; (S.M.A.); (E.T.A.); (C.D.K.); (O.G.O.)
| | - Andrea Regina Gnilane Sène
- Division of Human Genetics, Faculty of Medicine, Pharmacy and Odontology, University Cheikh Anta Diop (UCAD), Dakar 10700, Senegal; (Y.D.); (J.P.D.D.); (S.A.B.); (C.A.T.L.); (A.R.G.S.); (P.D.S.), (R.N.D.)
| | - Pierre Diaga Sarr
- Division of Human Genetics, Faculty of Medicine, Pharmacy and Odontology, University Cheikh Anta Diop (UCAD), Dakar 10700, Senegal; (Y.D.); (J.P.D.D.); (S.A.B.); (C.A.T.L.); (A.R.G.S.); (P.D.S.), (R.N.D.)
| | - Bay Karim Diallo
- Department of Oto-Rhino-Laryngology, Albert Royer Children’s Hospital, Dakar 10700, Senegal;
| | - Rokhaya Ndiaye Diallo
- Division of Human Genetics, Faculty of Medicine, Pharmacy and Odontology, University Cheikh Anta Diop (UCAD), Dakar 10700, Senegal; (Y.D.); (J.P.D.D.); (S.A.B.); (C.A.T.L.); (A.R.G.S.); (P.D.S.), (R.N.D.)
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa; (S.M.A.); (E.T.A.); (C.D.K.); (O.G.O.)
- McKusick-Nathans Institute and Department of Genetic Medicine, Johns-Hopskins University School of Medicine, Baltimore, MD 21205, USA
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Manyisa N, Adadey SM, Wonkam-Tingang E, Yalcouye A, Wonkam A. Hearing Impairment in South Africa and the Lessons Learned for Planetary Health Genomics: A Systematic Review. OMICS : A JOURNAL OF INTEGRATIVE BIOLOGY 2022; 26:2-18. [PMID: 35041532 PMCID: PMC8792495 DOI: 10.1089/omi.2021.0181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Hearing impairment (HI) is a silent planetary health crisis that requires attention worldwide. The prevalence of HI in South Africa is estimated as 5.5 in 100 live births, which is about 5 times higher than the prevalence in high-income countries. This also offers opportunity to drive progressive science, technology and innovation policy, and health systems. We present here a systematic analysis and review on the prevalence, etiologies, clinical patterns, and genetics/genomics of HI in South Africa. We searched PubMed, Scopus, African Journals Online, AFROLIB, and African Index Medicus to identify the pertinent studies on HI in South Africa, published from inception to April 30, 2021, and the data were summarized narratively. We screened 944 records, of which 27 studies were included in the review. The age at diagnosis is ∼3 years of age and the most common factor associated with acquired HI was middle ear infections. There were numerous reports on medication toxicity, with kanamycin-induced ototoxicity requiring specific attention when considering the high burden of tuberculosis in South Africa. The Waardenburg Syndrome is the most common reported syndromic HI. The Usher Syndrome is the only syndrome with genetic investigations, whereby a founder mutation was identified among black South Africans (MYO7A-c.6377delC). GJB2 and GJB6 genes are not major contributors to nonsyndromic HI among Black South Africans. Furthermore, emerging data using targeted panel sequencing have shown a low resolution rate in Black South Africans in known HI genes. Importantly, mutations in known nonsyndromic HI genes are infrequent in South Africa. Therefore, whole-exome sequencing appears as the most effective way forward to identify variants associated with HI in South Africa. Taken together, this article contributes to the emerging field of planetary health genomics with a focus on HI and offers new insights and lessons learned for future roadmaps on genomics/multiomics and clinical studies of HI around the world.
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Affiliation(s)
- Noluthando Manyisa
- Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Samuel Mawuli Adadey
- Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,West African Centre for Cell Biology of Infectious Pathogens, College of Basic and Applied Sciences, University of Ghana, Accra, Ghana
| | - Edmond Wonkam-Tingang
- Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Abdoulaye Yalcouye
- Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Department of Neurology, Point G Teaching Hospital, University of Sciences, Techniques and Technology, Bamako, Mali
| | - Ambroise Wonkam
- Division of Human Genetics, Department of Pathology, Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Adadey SM, Wonkam-Tingang E, Aboagye ET, Quaye O, Awandare GA, Wonkam A. Hearing loss in Africa: current genetic profile. Hum Genet 2021; 141:505-517. [PMID: 34609590 PMCID: PMC9034983 DOI: 10.1007/s00439-021-02376-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 09/21/2021] [Indexed: 01/03/2023]
Abstract
Hearing impairment (HI) is highly heterogeneous with over 123 associated genes reported to date, mostly from studies among Europeans and Asians. Here, we performed a systematic review of literature on the genetic profile of HI in Africa. The study protocol was registered on PROSPERO, International Prospective Register of Systematic Reviews with the registration number “CRD42021240852”. Literature search was conducted on PubMed, Scopus, Africa-Wide Information, and Web of Science databases. A total of 89 full-text records was selected and retrieved for data extraction and analyses. We found reports from only 17/54 (31.5%) African countries. The majority (61/89; 68.5%) of articles were from North Africa, with few reports found from sub-Saharan Africa. The most common method used in these publications was targeted gene sequencing (n = 66/111; 59.5%), and only 13.5% (n = 15/111) used whole-exome sequencing. More than half of the studies were performed in families segregating HI (n = 51/89). GJB2 was the most investigated gene, with GJB2: p.(R143W) founder variant only reported in Ghana, while GJB2: c.35delG was common in North African countries. Variants in MYO15A were the second frequently reported in both North and Central Africa, followed by ATP6V1B1 only reported from North Africa. Usher syndrome was the main syndromic HI molecularly investigated, with variants in five genes reported: USH2A, USH1G, USH1C, MYO7A, and PCDH15. MYO7A: p.(P1780S) founder variant was reported as the common Usher syndrome variant among Black South Africans. This review provides the most comprehensive data on HI gene variants in the largely under-investigated African populations. Future exomes studies particularly in multiplex families will likely provide opportunities for the discovery of the next sets of novel HI genes, and well as unreported variants in known genes to further our understanding of HI pathobiology, globally.
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Affiliation(s)
- Samuel Mawuli Adadey
- Department of Biochemistry, Cell and Molecular Biology, West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon, Accra, Ghana.,Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, 7925, South Africa
| | - Edmond Wonkam-Tingang
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, 7925, South Africa
| | - Elvis Twumasi Aboagye
- Department of Biochemistry, Cell and Molecular Biology, West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon, Accra, Ghana
| | - Osbourne Quaye
- Department of Biochemistry, Cell and Molecular Biology, West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon, Accra, Ghana
| | - Gordon A Awandare
- Department of Biochemistry, Cell and Molecular Biology, West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon, Accra, Ghana
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, 7925, South Africa.
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Kamp M, Krause A, Ramsay M. Has translational genomics come of age in Africa? Hum Mol Genet 2021; 30:R164-R173. [PMID: 34240178 DOI: 10.1093/hmg/ddab180] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/27/2021] [Accepted: 06/29/2021] [Indexed: 01/12/2023] Open
Abstract
The rapid increase in genomics research in Africa and the growing promise of precision public health begs the question of whether African genomics has come of age and is being translated into improved healthcare for Africans. An assessment of the continent's readiness suggests that genetic service delivery remains limited and extremely fragile. The paucity of data on mutation profiles for monogenic disorders and lack of large genome-wide association cohorts for complex traits in African populations is a significant barrier, coupled with extreme genetic variation across different regions and ethnic groups. Data from many different populations is essential to developing appropriate genetic services. Of the proposed genetic service delivery models currently used in Africa-Uncharacterized, Limited, Disease-focused, Emerging and Established-the first three best describe the situation in most African countries. Implementation is fraught with difficulties related to the scarcity of an appropriately skilled medical genetic workforce, limited infrastructure and processes, insufficient health funding and lack of political support, and overstretched health systems. There is a strong nucleus of determined and optimistic clinicians and scientists with a clear vision, and there is hope for innovative solutions and technological leapfrogging. However, a multi-dimensional approach with active interventions to stimulate genomic research, clinical genetics and overarching healthcare systems is needed to reduce genetic service inequalities and accelerate precision public health on the continent. Human and infrastructure capacity development, dedicated funding, political will and supporting legislation, and public education and awareness, are critical elements for success. Africa-relevant genomic and related health economics research remains imperative with an overarching need to translate knowledge into improved healthcare. Given the limited data and genetic services across most of Africa, the continent has not yet come of 'genomics' age.
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Affiliation(s)
- Michelle Kamp
- Division of Human Genetics, National Health Laboratory Service and School of Pathology, Faculty of Health Sciences, The University of the Witwatersrand, National Health Laboratory Service, Johannesburg, 2193, South Africa.,Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
| | - Amanda Krause
- Division of Human Genetics, National Health Laboratory Service and School of Pathology, Faculty of Health Sciences, The University of the Witwatersrand, National Health Laboratory Service, Johannesburg, 2193, South Africa
| | - Michèle Ramsay
- Division of Human Genetics, National Health Laboratory Service and School of Pathology, Faculty of Health Sciences, The University of the Witwatersrand, National Health Laboratory Service, Johannesburg, 2193, South Africa.,Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
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8
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African genetic diversity and adaptation inform a precision medicine agenda. Nat Rev Genet 2021; 22:284-306. [PMID: 33432191 DOI: 10.1038/s41576-020-00306-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2020] [Indexed: 01/29/2023]
Abstract
The deep evolutionary history of African populations, since the emergence of modern humans more than 300,000 years ago, has resulted in high genetic diversity and considerable population structure. Selected genetic variants have increased in frequency due to environmental adaptation, but recent exposures to novel pathogens and changes in lifestyle render some of them with properties leading to present health liabilities. The unique discoverability potential from African genomic studies promises invaluable contributions to understanding the genomic and molecular basis of health and disease. Globally, African populations are understudied, and precision medicine approaches are largely based on data from European and Asian-ancestry populations, which limits the transferability of findings to the continent of Africa. Africa needs innovative precision medicine solutions based on African data that use knowledge and implementation strategies aligned to its climatic, cultural, economic and genomic diversity.
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Spectrum of MYO7A Mutations in an Indigenous South African Population Further Elucidates the Nonsyndromic Autosomal Recessive Phenotype of DFNB2 to Include Both Homozygous and Compound Heterozygous Mutations. Genes (Basel) 2021; 12:genes12020274. [PMID: 33671976 PMCID: PMC7919343 DOI: 10.3390/genes12020274] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 01/20/2021] [Accepted: 01/21/2021] [Indexed: 11/17/2022] Open
Abstract
MYO7A gene encodes unconventional myosin VIIA, which, when mutated, causes a phenotypic spectrum ranging from recessive hearing loss DFNB2 to deaf-blindness, Usher Type 1B (USH1B). MYO7A mutations are reported in nine DFNB2 families to date, none from sub-Saharan Africa.In DNA, from a cohort of 94 individuals representing 92 families from the Limpopo province of South Africa, eight MYO7A variations were detected among 10 individuals. Family studies identified homozygous and compound heterozygous mutations in 17 individuals out of 32 available family members. Four mutations were novel, p.Gly329Asp, p.Arg373His, p.Tyr1780Ser, and p.Pro2126Leufs*5. Two variations, p.Ser617Pro and p.Thr381Met, previously listed as of uncertain significance (ClinVar), were confirmed to be pathogenic. The identified mutations are predicted to interfere with the conformational properties of myosin VIIA through interruption or abrogation of multiple interactions between the mutant and neighbouring residues. Specifically, p.Pro2126Leufs*5, is predicted to abolish the critical site for the interactions between the tail and the motor domain essential for the autoregulation, leaving a non-functional, unregulated protein that causes hearing loss. We have identified MYO7A as a possible key deafness gene among indigenous sub-Saharan Africans. The spectrum of MYO7A mutations in this South African population points to DFNB2 as a specific entity that may occur in a homozygous or in a compound heterozygous state.
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Wonkam A, Lebeko K, Mowla S, Noubiap JJ, Chong M, Pare G. Whole exome sequencing reveals a biallelic frameshift mutation in GRXCR2 in hearing impairment in Cameroon. Mol Genet Genomic Med 2021; 9:e1609. [PMID: 33528103 PMCID: PMC8104159 DOI: 10.1002/mgg3.1609] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 01/06/2021] [Accepted: 01/11/2021] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Hearing impairment (HI) genes are poorly studied in African populations. METHODS We used whole exome sequencing (WES) to investigate pathogenic and likely pathogenic (PLP) variants in 10 individuals with HI, from four multiplex families from Cameroon, two of which were previously unresolved with a targeted gene enrichment (TGE) panel of 116 genes. In silico protein modelling, western blotting and live imaging of transfected HEK293 cells were performed to study protein structure and functions. RESULTS All PLP variants previously identified with TGE were replicated. In one previously unresolved family, we found a homozygous frameshift PLP variant in GRXCR2 (OMIM: 615762), NM_001080516.1(GRXCR2):c.251delC p.(Ile85SerfsTer33), in two affected siblings; and additionally, in 1/80 unrelated individuals affected with non-syndromic hearing impairment (NSHI). The GRXCR2-c.251delC variant introduced a premature stop codon, leading to truncation and loss of a zinc-finger domain. Fluorescence confocal microscopy tracked the wild-type GRXCR2 protein to the cellular membrane, unlike the mutated GRXCR2 protein. CONCLUSION This study confirms GRXCR2 as a HI-associated gene. GRXCR2 should be included to the currently available TGE panels for HI diagnosis.
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Affiliation(s)
- Ambroise Wonkam
- Department of Medicine, Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.,Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Kamogelo Lebeko
- Department of Medicine, Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Shaheen Mowla
- Department of Pathology, Division of Haematology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Jean Jacques Noubiap
- Centre for Heart Rhythm Disorders, South Australian Health and Medical Research Institute (SAHMRI, University of Adelaide and Royal Adelaide Hospital, Adelaide, Australia
| | - Mike Chong
- Population Health Research Institute, Hamilton Health Sciences and McMaster University, Hamilton, ON, Canada
| | - Guillaume Pare
- Population Health Research Institute, Hamilton Health Sciences and McMaster University, Hamilton, ON, Canada
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11
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Adadey SM, Wonkam-Tingang E, Twumasi Aboagye E, Nayo-Gyan DW, Boatemaa Ansong M, Quaye O, Awandare GA, Wonkam A. Connexin Genes Variants Associated with Non-Syndromic Hearing Impairment: A Systematic Review of the Global Burden. Life (Basel) 2020; 10:life10110258. [PMID: 33126609 PMCID: PMC7693846 DOI: 10.3390/life10110258] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/18/2020] [Accepted: 10/27/2020] [Indexed: 12/21/2022] Open
Abstract
Mutations in connexins are the most common causes of hearing impairment (HI) in many populations. Our aim was to review the global burden of pathogenic and likely pathogenic (PLP) variants in connexin genes associated with HI. We conducted a systematic review of the literature based on targeted inclusion/exclusion criteria of publications from 1997 to 2020. The databases used were PubMed, Scopus, Africa-Wide Information, and Web of Science. The protocol was registered on PROSPERO, the International Prospective Register of Systematic Reviews, with the registration number “CRD42020169697”. The data extracted were analyzed using Microsoft Excel and SPSS version 25 (IBM, Armonk, New York, United States). A total of 571 independent studies were retrieved and considered for data extraction with the majority of studies (47.8% (n = 289)) done in Asia. Targeted sequencing was found to be the most common technique used in investigating connexin gene mutations. We identified seven connexin genes that were associated with HI, and GJB2 (520/571 publications) was the most studied among the seven. Excluding PLP in GJB2, GJB6, and GJA1 the other connexin gene variants (thus GJB3, GJB4, GJC3, and GJC1 variants) had conflicting association with HI. Biallelic GJB2 PLP variants were the most common and widespread variants associated with non-syndromic hearing impairment (NSHI) in different global populations but absent in most African populations. The most common GJB2 alleles found to be predominant in specific populations include; p.Gly12ValfsTer2 in Europeans, North Africans, Brazilians, and Americans; p.V37I and p.L79Cfs in Asians; p.W24X in Indians; p.L56Rfs in Americans; and the founder mutation p.R143W in Africans from Ghana, or with putative Ghanaian ancestry. The present review suggests that only GJB2 and GJB3 are recognized and validated HI genes. The findings call for an extensive investigation of the other connexin genes in many populations to elucidate their contributions to HI, in order to improve gene-disease pair curations, globally.
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Affiliation(s)
- Samuel Mawuli Adadey
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon GA184, Accra, Greater Accra Region, Ghana; (S.M.A.); (O.Q.); (G.A.A.)
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa;
| | - Edmond Wonkam-Tingang
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa;
| | - Elvis Twumasi Aboagye
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa;
| | - Daniel Wonder Nayo-Gyan
- Department of Applied Chemistry and Biochemistry, C. K. Tedam University of Technology and Applied Sciences, P.O. Box 24, Navrongo 00000, Upper East Region, Ghana;
| | - Maame Boatemaa Ansong
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
| | - Osbourne Quaye
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon GA184, Accra, Greater Accra Region, Ghana; (S.M.A.); (O.Q.); (G.A.A.)
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
| | - Gordon A. Awandare
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, P.O. Box LG 54, Legon GA184, Accra, Greater Accra Region, Ghana; (S.M.A.); (O.Q.); (G.A.A.)
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, P.O. Box LG 54, Legon Accra GA184, Greater Accra Region, Ghana; (E.T.A.); (M.B.A.)
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa;
- Correspondence: ; Tel.: +27-21-4066307
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12
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Wonkam A, Manyisa N, Bope CD, Dandara C, Chimusa ER. Whole exome sequencing reveals pathogenic variants in MYO3A, MYO15A and COL9A3 and differential frequencies in ancestral alleles in hearing impairment genes among individuals from Cameroon. Hum Mol Genet 2020; 29:3729-3743. [PMID: 33078831 PMCID: PMC7861016 DOI: 10.1093/hmg/ddaa225] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 10/01/2020] [Accepted: 10/12/2020] [Indexed: 12/30/2022] Open
Abstract
There is scarcity of known gene variants of hearing impairment (HI) in African populations. This knowledge deficit is ultimately affecting the development of genetic diagnoses. We used whole exome sequencing to investigate gene variants, pathways of interactive genes and the fractions of ancestral overderived alleles for 159 HI genes among 18 Cameroonian patients with non-syndromic HI (NSHI) and 129 ethnically matched controls. Pathogenic and likely pathogenic (PLP) variants were found in MYO3A, MYO15A and COL9A3, with a resolution rate of 50% (9/18 patients). The study identified significant genetic differentiation in novel population-specific gene variants at FOXD4L2, DHRS2L6, RPL3L and VTN between HI patients and controls. These gene variants are found in functional/co-expressed interactive networks with other known HI-associated genes and in the same pathways with VTN being a hub protein, that is, focal adhesion pathway and regulation of the actin cytoskeleton (P-values <0.05). The results suggest that these novel population-specific gene variants are possible modifiers of the HI phenotypes. We found a high proportion of ancestral allele versus derived at low HI patients-specific minor allele frequency in the range of 0.0–0.1. The results showed a relatively low pickup rate of PLP variants in known genes in this group of Cameroonian patients with NSHI. In addition, findings may signal an evolutionary enrichment of some variants of HI genes in patients, as the result of polygenic adaptation, and suggest the possibility of multigenic influence on the phenotype of congenital HI, which deserves further investigations.
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Affiliation(s)
- Ambroise Wonkam
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa.,Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa
| | - Noluthando Manyisa
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa
| | - Christian D Bope
- Department of Mathematics and Department of Computer Science, Faculty of Sciences, University of Kinshasa, Kinshasa, Democratic Republic of Congo
| | - Collet Dandara
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa
| | - Emile R Chimusa
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa
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13
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Abstract
The incidence of hearing impairment (HI) is higher in low- and middle-income countries when compared to high-income countries. There is therefore a necessity to estimate the burden of this condition in developing world. The aim of our study was to use a systematic approach to provide summarized data on the prevalence, etiologies, clinical patterns and genetics of HI in Cameroon. We searched PubMed, Scopus, African Journals Online, AFROLIB and African Index Medicus to identify relevant studies on HI in Cameroon, published from inception to 31 October, 2019, with no language restrictions. Reference lists of included studies were also scrutinized, and data were summarized narratively. This study is registered with PROSPERO, number CRD42019142788. We screened 333 records, of which 17 studies were finally included in the review. The prevalence of HI in Cameroon ranges from 0.9% to 3.6% in population-based studies and increases with age. Environmental factors contribute to 52.6% to 62.2% of HI cases, with meningitis, impacted wax and age-related disorder being the most common ones. Hereditary HI comprises 0.8% to 14.8% of all cases. In 32.6% to 37% of HI cases, the origin remains unknown. Non-syndromic hearing impairment (NSHI) is the most frequent clinical entity and accounts for 86.1% to 92.5% of cases of HI of genetic origin. Waardenburg and Usher syndromes account for 50% to 57.14% and 8.9% to 42.9% of genetic syndromic cases, respectively. No pathogenic mutation was described in GJB6 gene, and the prevalence of pathogenic mutations in GJB2 gene ranged from 0% to 0.5%. The prevalence of pathogenic mutations in other known NSHI genes was <10% in Cameroonian probands. Environmental factors are the leading etiology of HI in Cameroon, and mutations in most important HI genes are infrequent in Cameroon. Whole genome sequencing therefore appears as the most effective way to identify variants associated with HI in Cameroon and sub-Saharan Africa in general.
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14
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Wonkam Tingang E, Noubiap JJ, F. Fokouo JV, Oluwole OG, Nguefack S, Chimusa ER, Wonkam A. Hearing Impairment Overview in Africa: the Case of Cameroon. Genes (Basel) 2020; 11:genes11020233. [PMID: 32098311 PMCID: PMC7073999 DOI: 10.3390/genes11020233] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 02/15/2020] [Accepted: 02/19/2020] [Indexed: 01/27/2023] Open
Abstract
The incidence of hearing impairment (HI) is higher in low- and middle-income countries when compared to high-income countries. There is therefore a necessity to estimate the burden of this condition in developing world. The aim of our study was to use a systematic approach to provide summarized data on the prevalence, etiologies, clinical patterns and genetics of HI in Cameroon. We searched PubMed, Scopus, African Journals Online, AFROLIB and African Index Medicus to identify relevant studies on HI in Cameroon, published from inception to 31 October, 2019, with no language restrictions. Reference lists of included studies were also scrutinized, and data were summarized narratively. This study is registered with PROSPERO, number CRD42019142788. We screened 333 records, of which 17 studies were finally included in the review. The prevalence of HI in Cameroon ranges from 0.9% to 3.6% in population-based studies and increases with age. Environmental factors contribute to 52.6% to 62.2% of HI cases, with meningitis, impacted wax and age-related disorder being the most common ones. Hereditary HI comprises 0.8% to 14.8% of all cases. In 32.6% to 37% of HI cases, the origin remains unknown. Non-syndromic hearing impairment (NSHI) is the most frequent clinical entity and accounts for 86.1% to 92.5% of cases of HI of genetic origin. Waardenburg and Usher syndromes account for 50% to 57.14% and 8.9% to 42.9% of genetic syndromic cases, respectively. No pathogenic mutation was described in GJB6 gene, and the prevalence of pathogenic mutations in GJB2 gene ranged from 0% to 0.5%. The prevalence of pathogenic mutations in other known NSHI genes was <10% in Cameroonian probands. Environmental factors are the leading etiology of HI in Cameroon, and mutations in most important HI genes are infrequent in Cameroon. Whole genome sequencing therefore appears as the most effective way to identify variants associated with HI in Cameroon and sub-Saharan Africa in general.
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Affiliation(s)
- Edmond Wonkam Tingang
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa; (E.W.T.); (O.G.O.); (E.R.C.)
| | - Jean Jacques Noubiap
- Centre for Heart Rhythm Disorders, South Australian Health and Medical Research Institute (SAHMRI), University of Adelaide and Royal Adelaide Hospital, Adelaide 5000, Australia;
| | | | - Oluwafemi Gabriel Oluwole
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa; (E.W.T.); (O.G.O.); (E.R.C.)
| | - Séraphin Nguefack
- Department of Paediatrics, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé 1364, Cameroon;
- Paediatrics unit, Gynaeco-Obstetric and Paediatric Hospital, Yaoundé 4362, Cameroon
| | - Emile R. Chimusa
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa; (E.W.T.); (O.G.O.); (E.R.C.)
| | - Ambroise Wonkam
- Division of Human Genetics, Department of Pathology, University of Cape Town, Cape Town 7925, South Africa; (E.W.T.); (O.G.O.); (E.R.C.)
- Department of Medicine, University of Cape Town, Cape Town 7925, South Africa
- Correspondence: ; Tel.: +27-21-4066-307
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15
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GJB2 and GJB6 Mutations in Hereditary Recessive Non-Syndromic Hearing Impairment in Cameroon. Genes (Basel) 2019; 10:genes10110844. [PMID: 31731535 PMCID: PMC6895965 DOI: 10.3390/genes10110844] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 10/07/2019] [Accepted: 10/23/2019] [Indexed: 02/06/2023] Open
Abstract
This study aimed to investigate GJB2 (connexin 26) and GJB6 (connexin 30) mutations associated with familial non-syndromic childhood hearing impairment (HI) in Cameroon. We selected only families segregating HI, with at least two affected individuals and with strong evidence of non-environmental causes. DNA was extracted from peripheral blood, and the entire coding region of GJB2 was interrogated using Sanger sequencing. Multiplex PCR and Sanger sequencing were used to analyze the prevalence of the GJB6-D3S1830 deletion. A total of 93 patients, belonging to 41 families, were included in the analysis. Hearing impairment was sensorineural in 51 out of 54 (94.4%) patients. Pedigree analysis suggested autosomal recessive inheritance in 85.4% (35/41) of families. Hearing impairment was inherited in an autosomal dominant and mitochondrial mode in 12.2% (5/41) and 2.4% (1/41) of families, respectively. Most HI participants were non-syndromic (92.5%; 86/93). Four patients from two families presented with type 2 Waardenburg syndrome, and three cases of type 2 Usher syndrome were identified in one family. No GJB2 mutations were found in any of the 29 families with non-syndromic HI. Additionally, the GJB6-D3S1830 deletion was not identified in any of the HI patients. This study confirms that mutations in the GJB2 gene and the del(GJB6-D13S1830) mutation do not contribute to familial HI in Cameroon.
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16
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Adadey SM, Manyisa N, Mnika K, de Kock C, Nembaware V, Quaye O, Amedofu GK, Awandare GA, Wonkam A. GJB2 and GJB6 Mutations in Non-Syndromic Childhood Hearing Impairment in Ghana. Front Genet 2019; 10:841. [PMID: 31620164 PMCID: PMC6759689 DOI: 10.3389/fgene.2019.00841] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 08/13/2019] [Indexed: 01/16/2023] Open
Abstract
Our study aimed to investigate GJB2 (connexin 26) and GJB6 (connexin 30) mutations associated with non-syndromic childhood hearing impairment (HI) as well as the environmental causes of HI in Ghana. Medical reports of 1,104 students attending schools for the deaf were analyzed. Families segregating HI, as well as isolated cases of HI of putative genetic origin were recruited. DNA was extracted from peripheral blood followed by Sanger sequencing of the entire coding region of GJB2. Multiplex PCR and Sanger sequencing were used to analyze the prevalence of GJB6-D3S1830 deletion. Ninety-seven families segregating HI were identified, with 235 affected individuals; and a total of 166 isolated cases of putative genetic causes, were sampled from 11 schools for the deaf in Ghana. The environmental factors, particularly meningitis, remain a major cause of HI impairment in Ghana. The male/female ratio was 1.49. Only 59.6% of the patients had their first comprehensive HI test between 6 to 11 years of age. Nearly all the participants had sensorineural HI (99.5%; n = 639). The majority had pre-lingual HI (68.3%, n = 754), of which 92.8% were congenital. Pedigree analysis suggested autosomal recessive inheritance in 96.9% of the familial cases. GJB2-R143W mutation, previously reported as founder a mutation in Ghana accounted for 25.9% (21/81) in the homozygous state in familial cases, and in 7.9% (11/140) of non-familial non-syndromic congenital HI cases, of putative genetic origin. In a control population without HI, we found a prevalent of GJB2-R143W carriers of 1.4% (2/145), in the heterozygous state. No GJB6-D3S1830 deletion was identified in any of the HI patients. GJB2-R143W mutation accounted for over a quarter of familial non-syndromic HI in Ghana and should be investigated in clinical practice. The large connexin 30 gene deletion (GJB6-D3S1830 deletion) does not account for of congenital non-syndromic HI in Ghana. There is a need to employ next generation sequencing approaches and functional genomics studies to identify the other genes involved in most families and isolated cases of HI in Ghana.
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Affiliation(s)
- Samuel M. Adadey
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Noluthando Manyisa
- Division of Human Genetics, Faculty of Health Sciences—University of Cape Town, Cape Town , South Africa
| | - Khuthala Mnika
- Division of Human Genetics, Faculty of Health Sciences—University of Cape Town, Cape Town , South Africa
| | - Carmen de Kock
- Division of Human Genetics, Faculty of Health Sciences—University of Cape Town, Cape Town , South Africa
| | - Victoria Nembaware
- Division of Human Genetics, Faculty of Health Sciences—University of Cape Town, Cape Town , South Africa
| | - Osbourne Quaye
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Geoffrey K. Amedofu
- Department of Eye, Ear, Nose and Throat, School of Medical Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Gordon A. Awandare
- West African Centre for Cell Biology of Infectious Pathogens (WACCBIP), University of Ghana, Accra, Ghana
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences—University of Cape Town, Cape Town , South Africa
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17
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Hong H, Budhathoki C, Farley JE. Increased risk of aminoglycoside-induced hearing loss in MDR-TB patients with HIV coinfection. Int J Tuberc Lung Dis 2019; 22:667-674. [PMID: 29862952 DOI: 10.5588/ijtld.17.0830] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
SETTING A high proportion of individuals with multidrug-resistant tuberculosis (MDR-TB) develop permanent hearing loss due to ototoxicity caused by injectable aminoglycosides (AGs). The prevalence of AG-induced hearing loss is greatest in tuberculosis (TB) and human immunodeficiency virus (HIV) endemic countries in sub-Saharan Africa. However, whether HIV coinfection is associated with a higher incidence of AG-induced hearing loss during MDR-TB treatment is controversial. OBJECTIVE To evaluate the impact of HIV coinfection on AG-induced hearing loss among individuals with MDR-TB in sub-Saharan Africa. DESIGN This was a meta-analysis of articles published in PubMed, Embase, Scopus, Cumulative Index to Nursing and Allied Health Literature, Web of Science, Cochrane Review, and reference lists using search terms 'hearing loss', 'aminoglycoside', and 'sub-Saharan Africa'. RESULTS Eight studies conducted in South Africa, Botswana and Namibia and published between 2012 and 2016 were included. As the included studies were homogeneous (χ2 = 8.84, df = 7), a fixed-effects model was used. Individuals with MDR-TB and HIV coinfection had a 22% higher risk of developing AG-induced hearing loss than non-HIV-infected individuals (pooled relative risk 1.22, 95%CI 1.10-1.36) during MDR-TB treatment. CONCLUSION This finding is critical for TB programs with regard to the expansion of injectable-sparing regimens. Our findings lend credibility to using injectable-sparing regimens and more frequent hearing monitoring, particularly in resource-limited settings for HIV-coinfected individuals.
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Affiliation(s)
- H Hong
- Department of Community-Public Health
| | | | - J E Farley
- Department of Community-Public Health, REACH Initiative, Johns Hopkins University School of Nursing, Baltimore, Maryland, USA
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18
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Hong H, Dooley KE, Starbird LE, Francis HW, Farley JE. Adverse outcome pathway for aminoglycoside ototoxicity in drug-resistant tuberculosis treatment. Arch Toxicol 2019; 93:1385-1399. [PMID: 30963202 DOI: 10.1007/s00204-019-02407-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/06/2019] [Indexed: 12/22/2022]
Abstract
Individuals treated for multidrug-resistant tuberculosis (MDR-TB) with aminoglycosides (AGs) in resource-limited settings often experience permanent hearing loss. However, AG ototoxicity has never been conceptually integrated or causally linked to MDR-TB patients' pre-treatment health condition. We sought to develop a framework that examines the relationships between pre-treatment conditions and AG-induced hearing loss among MDR-TB-infected individuals in sub-Saharan Africa. The adverse outcome pathway (AOP) approach was used to develop a framework linking key events (KEs) within a biological pathway that results in adverse outcomes (AO), which are associated with chemical perturbation of a molecular initiating event (MIE). This AOP describes pathways initiating from AG accumulation in hair cells, sound transducers of the inner ear immediately after AG administration. After administration, the drug catalyzes cellular oxidative stress due to overproduction of reactive oxygen species. Since oxidative stress inhibits mitochondrial protein synthesis, hair cells undergo apoptotic cell death, resulting in irreversible hearing loss (AO). We identified the following pre-treatment conditions that worsen the causal linkage between MIE and AO: HIV, malnutrition, aging, noise, smoking, and alcohol use. The KEs are: (1) nephrotoxicity, pre-existing hearing loss, and hypoalbuminemia that catalyzes AG accumulation; (2) immunodeficiency and antioxidant deficiency that trigger oxidative stress pathways; and (3) co-administration of mitochondrial toxic drugs that hinder mitochondrial protein synthesis, causing apoptosis. This AOP clearly warrants the development of personalized interventions for patients undergoing MDR-TB treatment. Such interventions (i.e., choosing less ototoxic drugs, scheduling frequent monitoring, modifying nutritional status, avoiding poly-pharmacy) will be required to limit the burden of AG ototoxicity.
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Affiliation(s)
- Hyejeong Hong
- Johns Hopkins University School of Nursing, 525 North Wolfe Street, Baltimore, MD, 21205, USA. .,Johns Hopkins University School of Nursing, The REACH Initiative, 855 N. Wolfe Street, 21205, Baltimore, MD, USA.
| | - Kelly E Dooley
- Divisions of Clinical Pharmacology and Infectious Disease, Johns Hopkins University School of Medicine, 600 North Wolfe Street, 21205, Baltimore, MD, USA
| | - Laura E Starbird
- Center for Health Policy, Columbia University School of Nursing, 560 W 168 St, 10032, New York, NY, USA
| | - Howard W Francis
- Division of Head and Neck Surgery and Communication Sciences, Duke University School of Medicine, 40 Duke Medicine Circle, 27710, Durham, NC, USA
| | - Jason E Farley
- Johns Hopkins University School of Nursing, 525 North Wolfe Street, Baltimore, MD, 21205, USA.,Johns Hopkins University School of Nursing, The REACH Initiative, 855 N. Wolfe Street, 21205, Baltimore, MD, USA
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19
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Han JJ, Nguyen PD, Oh DY, Han JH, Kim AR, Kim MY, Park HR, Tran LH, Dung NH, Koo JW, Lee JH, Oh SH, Anh Vu H, Choi BY. Elucidation of the unique mutation spectrum of severe hearing loss in a Vietnamese pediatric population. Sci Rep 2019; 9:1604. [PMID: 30733538 PMCID: PMC6367484 DOI: 10.1038/s41598-018-38245-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 12/17/2018] [Indexed: 11/09/2022] Open
Abstract
The mutational spectrum of deafness in Indochina Peninsula, including Vietnam, remains mostly undetermined. This significantly hampers the progress toward establishing an effective genetic screening method and early customized rehabilitation modalities for hearing loss. In this study, we evaluated the genetic profile of severe-to-profound hearing loss in a Vietnamese pediatric population using a hierarchical genetic analysis protocol that screened 11 known deafness-causing variants, followed by massively parallel sequencing targeting 129 deafness-associated genes. Eighty-seven children with isolated severe-to-profound non-syndromic hearing loss without family history were included. The overall molecular diagnostic yield was estimated to be 31.7%. The mutational spectrum for severe-to-profound non-syndromic hearing loss in our Vietnamese population was unique: The most prevalent variants resided in the MYO15A gene (7.2%), followed by GJB2 (6.9%), MYO7A (5.5%), SLC26A4 (4.6%), TMC1 (1.8%), ESPN (1.8%), POU3F4 (1.8%), MYH14 (1.8%), EYA1 (1.8%), and MR-RNR1 (1.1%). The unique spectrum of causative genes in the Vietnamese deaf population was similar to that in the southern Chinese deaf population. It is our hope that the mutation spectrum provided here could aid in establishing an efficient protocol for genetic analysis of severe-to-profound hearing loss and a customized screening kit for the Vietnamese population.
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Affiliation(s)
- Jae Joon Han
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Pham Dinh Nguyen
- Department of Otorhinolaryngology, Children's Hospital 1, Ho Chi Minh City, Vietnam
| | - Doo-Yi Oh
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Jin Hee Han
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Ah-Reum Kim
- Biomedical Research Institute, Seoul National University Hospital, Seoul, Korea
| | - Min Young Kim
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Hye-Rim Park
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Lam Huyen Tran
- Department of Otorhinolaryngology, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam
| | - Nguyen Huu Dung
- Department of Otorhinolaryngology, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam
| | - Ja-Won Koo
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Jun Ho Lee
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul, Korea
| | - Seung Ha Oh
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul, Korea
| | - Hoang Anh Vu
- Center for Molecular Biomedicine, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam.
| | - Byung Yoon Choi
- Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, Korea.
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20
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Krause A, Seymour H, Ramsay M. Common and Founder Mutations for Monogenic Traits in Sub-Saharan African Populations. Annu Rev Genomics Hum Genet 2018; 19:149-175. [DOI: 10.1146/annurev-genom-083117-021256] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This review highlights molecular genetic studies of monogenic traits where common pathogenic mutations occur in black families from sub-Saharan Africa. Examples of founder mutations have been identified for oculocutaneous albinism, cystic fibrosis, Fanconi anemia, and Gaucher disease. Although there are few studies from Africa, some of the mutations traverse populations across the continent, and they are almost all different from the common mutations observed in non-African populations. Myotonic dystrophy is curiously absent among Africans, and nonsyndromic deafness does not arise from mutations in GJB2 and GJB7. Locus heterogeneity is present for Huntington disease, with two common triplet expansion loci in Africa, HTT and JPH3. These findings have important clinical consequences for diagnosis, treatment, and genetic counseling in affected families. We currently have just a glimpse of the molecular etiology of monogenic diseases in sub-Saharan Africa, a proverbial “ears of the hippo” situation.
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Affiliation(s)
- Amanda Krause
- Division of Human Genetics, National Health Laboratory Service, and Division of Human Genetics, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Heather Seymour
- Division of Human Genetics, National Health Laboratory Service, and Division of Human Genetics, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Michèle Ramsay
- Division of Human Genetics, National Health Laboratory Service, and Division of Human Genetics, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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21
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Adadey SM, Awandare G, Amedofu GK, Wonkam A. Public Health Burden of Hearing Impairment and the Promise of Genomics and Environmental Research: A Case Study in Ghana, Africa. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2018; 21:638-646. [PMID: 29140768 DOI: 10.1089/omi.2017.0145] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Hearing impairment (HI) is one of the most disabling conditions of major global health burden that contributes adversely to the social and economic development of a country, if not managed properly. A proper assessment of the nationwide burden and etiology of HI is instrumental in the prevention, treatment, and management of the condition. This article sought to perform an expert review of HI in Ghana to determine the present knowledge of its burden and possible causes of the condition. A literature search was conducted in PubMed using the following keywords: "hearing loss" OR "hearing impairment" OR "deafness" AND "Ghana." The literature was scanned until July 20, 2017, with specific inclusion of targeted landmark and background articles on HI. From the search, 18 of out 5869 articles were selected and considered for the review. The results of the search indicated that there were no extensive studies to determine the national burden of HI in Ghana. However, the few studies assessed suggested that the disease is either acquired or inherited. The burden of acquired HI was higher in adults than children, women than men, and people working in a noisy environment. Regarding the genetic cause, specific founder mutations in GJB2 gene (R143W, L79P, V178A, R184Q, A197S, I203K, and L214P) was the only identified genetic cause of HI in Ghana, but the other HI genes were not investigated. There has been some modest effort to study HI in Ghana, but comprehensive studies on the genetic and environmental etiologies (using the "multi-OMICS" approaches), classification, and burden of HI on Ghana are needed.
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Affiliation(s)
- Samuel Mawuli Adadey
- 1 West African Centre for Cell Biology of Infectious Pathogens, College of Basic and Applied Sciences, University of Ghana , Accra, Ghana
| | - Gordon Awandare
- 1 West African Centre for Cell Biology of Infectious Pathogens, College of Basic and Applied Sciences, University of Ghana , Accra, Ghana
| | | | - Ambroise Wonkam
- 3 Division of Human Genetics, Department of Medicine, Faculty of Health Sciences, University of Cape Town , Cape Town, South Africa
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22
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Pawlak-Osiñska K, Linkowska K, Grzybowski T. Genes important for otoneurological diagnostic purposes - current status and future prospects. ACTA ACUST UNITED AC 2018; 38:242-250. [PMID: 29984802 DOI: 10.14639/0392-100x-1692] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 10/12/2017] [Indexed: 11/23/2022]
Abstract
SUMMARY This review focuses on the current knowledge of the genes responsible for non-syndromic hearing loss that can be useful for otoneurological diagnostic purposes. From among a large number of genes that have been associated with non-syndromic hearing impairment, we selected several best-known genes, including the COCH gene, GJB2, GJB6 and SLC26A4, and we describe their role and effects of mutations and prevalence of mutations in various populations. Next, we focus on genes associated with tinnitus. Important areas for further research include assessment of genes potentially involved in pathophysiology of tinnitus and vertigo, which have traditionally been considered as being of otological aetiology, while advances in neuroimaging techniques have increasingly shifted studies toward neurological correlations.
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Affiliation(s)
- K Pawlak-Osiñska
- Department of Otolaryngology and Oncology Collegium Medicum in Bydgoszcz Nicolaus Copernicus University, Skłodowskiej-Curie 9, Bydgoszcz, Poland
| | - K Linkowska
- Department of Forensic Medicine Division of Molecular and Forensic Genetics Collegium Medicum in Bydgoszcz Nicolaus Copernicus University, Skłodowskiej-Curie 9, Bydgoszcz, Poland
| | - T Grzybowski
- Department of Forensic Medicine Division of Molecular and Forensic Genetics Collegium Medicum in Bydgoszcz Nicolaus Copernicus University, Skłodowskiej-Curie 9, Bydgoszcz, Poland
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23
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Caroça C, de Matos TM, Ribeiro D, Lourenço V, Martins T, Campelo P, Fialho G, Silva SN, Paço J, Caria H. Genetic Basis of Nonsyndromic Sensorineural Hearing Loss in the Sub-Saharan African Island Population of São Tomé and Príncipe: The Role of the DFNB1 Locus? OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2018; 20:449-55. [PMID: 27501294 DOI: 10.1089/omi.2016.0067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Hearing loss (HL) is a common condition with both genetic and environmental causes, and it greatly impacts global health. The prevalence of HL is reportedly higher in developing countries such as the Sub-Saharan African island of São Tomé and Príncipe, where the deaf community is estimated to be less than 1% of the population. We investigated the role of the DFNB1 locus (GJB2 and GJB6 genes) in the etiology of nonsyndromic sensorineural hearing loss (NSSHL) in São Tomé and Príncipe. A sample of 316 individuals, comprising 136 NSSHL patients (92 bilateral, 44 unilateral) and 180 controls, underwent a clinical and audiological examination. Sequencing of the GJB2 coding region and testing for the (GJB6-D13S1830) and del(GJB6-D13S1854) GJB6 deletions were performed. A total of 311 out of 316 individuals were successfully analyzed regarding the GJB2 and GJB6 genetic variations, respectively. The frequency of the GJB2 coding mutations in patients and controls was low. Some of those coding mutations are the most commonly found in Eurasian and Mediterranean populations and have also been identified in Portugal. None of the GJB6 deletions was present. The presence of certain coding variants in São Tomé and Príncipe suggests a non-Sub-Saharan genetic influx and supports the previously reported genetic influx from European (mainly Portuguese) ancestors. In summary, DFNB1 locus does not appear to be a major contributor to NSSHL in São Tomé and Príncipe. However, the presence of both pathogenic and likely pathogenic mutations in GJB2 suggests that GJB2-related NSSHL might still occur in this population, warranting further research on GJB2 testing in NSSHL cases.
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Affiliation(s)
- Cristina Caroça
- 1 Otolaryngology Department, Nova Medical School/Faculty of Medical Sciences , Universidade Nova de Lisboa, Lisboa, Portugal .,2 Hospital CUF Infante Santo , Otolaryngology Department, Hospital CUF Infante Santo, Lisboa, Portugal
| | - Tiago Morim de Matos
- 3 Deafness Research Group, Biomedicine and Translational Research, BioISI, Faculty of Sciences, University of Lisbon , Lisbon, Portugal
| | - Diogo Ribeiro
- 2 Hospital CUF Infante Santo , Otolaryngology Department, Hospital CUF Infante Santo, Lisboa, Portugal
| | - Vera Lourenço
- 2 Hospital CUF Infante Santo , Otolaryngology Department, Hospital CUF Infante Santo, Lisboa, Portugal
| | - Tânia Martins
- 2 Hospital CUF Infante Santo , Otolaryngology Department, Hospital CUF Infante Santo, Lisboa, Portugal
| | - Paula Campelo
- 2 Hospital CUF Infante Santo , Otolaryngology Department, Hospital CUF Infante Santo, Lisboa, Portugal
| | - Graça Fialho
- 3 Deafness Research Group, Biomedicine and Translational Research, BioISI, Faculty of Sciences, University of Lisbon , Lisbon, Portugal
| | - Susana Nunes Silva
- 4 Centre for Toxicogenomics and Human Health (ToxOmics), NOVA Medical School , Faculty of Medical Sciences, Universidade Nova de Lisboa, Lisboa, Portugal
| | - João Paço
- 1 Otolaryngology Department, Nova Medical School/Faculty of Medical Sciences , Universidade Nova de Lisboa, Lisboa, Portugal .,2 Hospital CUF Infante Santo , Otolaryngology Department, Hospital CUF Infante Santo, Lisboa, Portugal
| | - Helena Caria
- 3 Deafness Research Group, Biomedicine and Translational Research, BioISI, Faculty of Sciences, University of Lisbon , Lisbon, Portugal .,5 School of Health, Polytechnic Institute of Setubal , Setubal, Portugal
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Rudman JR, Kabahuma RI, Bressler SE, Feng Y, Blanton SH, Yan D, Liu XZ. The genetic basis of deafness in populations of African descent. J Genet Genomics 2017; 44:285-294. [PMID: 28642064 DOI: 10.1016/j.jgg.2017.03.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 02/03/2017] [Accepted: 03/24/2017] [Indexed: 11/24/2022]
Abstract
Hearing loss is the most common sensorineural disorder worldwide and is associated with more than 1000 mutations in more than 90 genes. While mutations in genes such as GJB2 (gap-junction protein β 2) and GJB6 (gap-junction protein β 6) are highly prevalent in Caucasian, Asian, and Middle Eastern populations, they are rare in both native African populations and those of African descent. The objective of this paper is to review the current knowledge regarding the epidemiology and genetics of hearing loss in African populations with a focus on native sub-Saharan African populations. Environmental etiologies related to poor access to healthcare and perinatal care account for the majority of cases. Syndromic etiologies including Waardenburg, Pendred and Usher syndromes are uncommon causes of hearing loss in these populations. Of the non-syndromic causes, common mutations in GJB2 and GJB6 are rarely implicated in populations of African descent. Recent use of next-generation sequencing (NGS) has identified several candidate deafness genes in African populations from Nigeria and South Africa that are unique when compared to common causative mutations worldwide. Researchers also recently described a dominant mutation in MYO3a in an African American family with non-syndromic hearing loss. The use of NGS and specialized panels will aid in identifying rare and novel mutations in a more cost- and time-effective manner. The identification of common hearing loss mutations in indigenous African populations will pave the way for translation into genetic deafness research in populations of African descent worldwide.
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Affiliation(s)
- Jason R Rudman
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Rosemary I Kabahuma
- Department of Otorhinolaryngology, Steve Biko Academic Hospital, University of Pretoria, Pretoria 0001, South Africa.
| | - Sara E Bressler
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Yong Feng
- Department of Otolaryngology, Xiangya Hospital, Central South University, Changsha 410008, China
| | - Susan H Blanton
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA; Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL 33136, USA; John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Denise Yan
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Xue-Zhong Liu
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL 33136, USA; Department of Otolaryngology, Xiangya Hospital, Central South University, Changsha 410008, China; Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL 33136, USA; John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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25
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Lebeko K, Manyisa N, Chimusa ER, Mulder N, Dandara C, Wonkam A. A Genomic and Protein-Protein Interaction Analyses of Nonsyndromic Hearing Impairment in Cameroon Using Targeted Genomic Enrichment and Massively Parallel Sequencing. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2017; 21:90-99. [PMID: 28075205 DOI: 10.1089/omi.2016.0171] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Hearing impairment (HI) is one of the leading causes of disability in the world, impacting the social, economic, and psychological well-being of the affected individual. This is particularly true in sub-Saharan Africa, which carries one of the highest burdens of this condition. Despite this, there are limited data on the most prevalent genes or mutations that cause HI among sub-Saharan Africans. Next-generation technologies, such as targeted genomic enrichment and massively parallel sequencing, offer new promise in this context. This study reports, for the first time to the best of our knowledge, on the prevalence of novel mutations identified through a platform of 116 HI genes (OtoSCOPE®), among 82 African probands with HI. Only variants OTOF NM_194248.2:c.766-2A>G and MYO7A NM_000260.3:c.1996C>T, p.Arg666Stop were found in 3 (3.7%) and 5 (6.1%) patients, respectively. In addition and uniquely, the analysis of protein-protein interactions (PPI), through interrogation of gene subnetworks, using a custom script and two databases (Enrichr and PANTHER), and an algorithm in the igraph package of R, identified the enrichment of sensory perception and mechanical stimulus biological processes, and the most significant molecular functions of these variants pertained to binding or structural activity. Furthermore, 10 genes (MYO7A, MYO6, KCTD3, NUMA1, MYH9, KCNQ1, UBC, DIAPH1, PSMC2, and RDX) were identified as significant hubs within the subnetworks. Results reveal that the novel variants identified among familial cases of HI in Cameroon are not common, and PPI analysis has highlighted the role of 10 genes, potentially important in understanding HI genomics among Africans.
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Affiliation(s)
- Kamogelo Lebeko
- 1 Division of Human Genetics, Department of Pathology, Faculty of Health Sciences - University of Cape Town , Cap Town, South Africa
| | - Noluthando Manyisa
- 1 Division of Human Genetics, Department of Pathology, Faculty of Health Sciences - University of Cape Town , Cap Town, South Africa
| | - Emile R Chimusa
- 1 Division of Human Genetics, Department of Pathology, Faculty of Health Sciences - University of Cape Town , Cap Town, South Africa
| | - Nicola Mulder
- 2 Division of Computational Biology, Faculty of Health Sciences - University of Cape Town , Cap Town, South Africa
| | - Collet Dandara
- 1 Division of Human Genetics, Department of Pathology, Faculty of Health Sciences - University of Cape Town , Cap Town, South Africa
| | - Ambroise Wonkam
- 1 Division of Human Genetics, Department of Pathology, Faculty of Health Sciences - University of Cape Town , Cap Town, South Africa .,3 Department of Medicine, Faculty of Health Sciences - University of Cape Town , Cap Town, South Africa
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26
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First report of prevalence c.IVS1+1G>A and del (GJB6-13S1854) mutations in Syrian families with non-syndromic sensorineural hearing loss. Int J Pediatr Otorhinolaryngol 2017; 92:82-87. [PMID: 28012540 DOI: 10.1016/j.ijporl.2016.11.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 11/13/2016] [Accepted: 11/14/2016] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Mutations in GJB2 and GJB6 genes are a frequent cause of congenital non-syndromic hearing loss (NSHL). Mutational screening has usually focused on coding region of GJB2 gene. A few studies have been conducted on the non-coding region and exon 1. c.IVS1+1G>A (a splice site mutation in GJB2 gene have been detected as disruptive mutation. Del (GJB6 D13S1830) is found in many populations, but del (GJB6 D13S1854) is reported from a few restricted countries. This study was carried out to investigate the prevalence of splice site mutation c.IVS1+1G>A and two common deletions in GJB6 gene as the genetic etiology of hearing impairment in 70 Syrian families. METHODS The frequency of the c.IVS1+1G>A mutation and two deletions were determined by PCR-RFLP and A multiplex PCR assay. RESULT Our results showed a high prevalence of IVS1+1G>A mutation (20%) and del(GJB6-D13S1854) (15.7%) in deaf families. The homozygous genotype (c.IVS1+1G>A/c.IVS1+1G>A) was observed in one family and the compound heterozygous genotypes (c.35delG/c.IVS1+1G>A) and (c.IVS1+1G>A/V153I) were observed in 7 families and one family respectively. Also, the heterozygous state (c.IVS1+1G>A/unknown) was detected in 5 families. The study of del((GJB6-D13S1854) was showed a compound heterozygous genotype del((GJB6-D13S1854)/c.IVS1+1G>A) in the same families (5 families) having heterozygous genotype of c.IVS1+1G>A mutation. Also, del(GJB6-D13S1854) is combined with c.35delG mutation in 2 families and it was observed in the heterozygous state del(GJB6-D13S1854)/unknown) in 4 families. In contrast, the del(GJB6-D13S1830) described in many population was absent in our patients. CONCLUSION Our findings indicate to significant contribution of the splice site mutation and del(GJB6-D13S1854) in our deaf families and these mutations were important causes of hearing impairment.
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27
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Manzoli GN, Bademci G, Acosta AX, Félix TM, Cengiz FB, Foster J, Da Silva DSD, Menendez I, Sanchez-Pena I, Tekin D, Blanton SH, Abe-Sandes K, Liu XZ, Tekin M. Targeted Resequencing of Deafness Genes Reveals a Founder MYO15A Variant in Northeastern Brazil. Ann Hum Genet 2016; 80:327-331. [PMID: 27870113 PMCID: PMC5127167 DOI: 10.1111/ahg.12177] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 08/23/2016] [Accepted: 10/06/2016] [Indexed: 11/29/2022]
Abstract
Identifying the genetic etiology in a person with hearing loss (HL) is challenging due to the extreme genetic heterogeneity in HL and the population-specific variability. In this study, after excluding GJB2 variants, targeted resequencing of 180 deafness-related genes revealed the causative variants in 11 of 19 (58%) Brazilian probands with autosomal recessive HL. Identified pathogenic variants were in MYO15A (10 families) and CLDN14 (one family). Remarkably, the MYO15A p.(Val1400Met) variant was identified in eight families from the city of Monte Santo in the northeast region of Brazil. Haplotype analysis of this variant was consistent with a single founder. No other cases with this variant were detected among 105 simplex cases from other cities of northeastern Brazil, suggesting that this variant is confined to a geographical region. This study suggests that it is feasible to develop population-specific screening for deafness variants once causative variants are identified in different geographical groups.
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Affiliation(s)
- Gabrielle N Manzoli
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
- Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ), Salvador, Bahia, Brazil
| | - Guney Bademci
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Angelina X Acosta
- Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ), Salvador, Bahia, Brazil
| | - Têmis M Félix
- Serviço de Genética Médica, Hospital de Clinicas de Porto Alegre, Brazil
| | - F Basak Cengiz
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Joseph Foster
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Danniel S Dias Da Silva
- Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ), Salvador, Bahia, Brazil
| | - Ibis Menendez
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Isalis Sanchez-Pena
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Demet Tekin
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Susan H Blanton
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
- Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Kiyoko Abe-Sandes
- Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ), Salvador, Bahia, Brazil
| | - Xue Zhong Liu
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Mustafa Tekin
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
- Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
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28
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Barashkov NA, Pshennikova VG, Posukh OL, Teryutin FM, Solovyev AV, Klarov LA, Romanov GP, Gotovtsev NN, Kozhevnikov AA, Kirillina EV, Sidorova OG, Vasilyevа LM, Fedotova EE, Morozov IV, Bondar AA, Solovyevа NA, Kononova SK, Rafailov AM, Sazonov NN, Alekseev AN, Tomsky MI, Dzhemileva LU, Khusnutdinova EK, Fedorova SA. Spectrum and Frequency of the GJB2 Gene Pathogenic Variants in a Large Cohort of Patients with Hearing Impairment Living in a Subarctic Region of Russia (the Sakha Republic). PLoS One 2016; 11:e0156300. [PMID: 27224056 PMCID: PMC4880331 DOI: 10.1371/journal.pone.0156300] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 05/12/2016] [Indexed: 11/29/2022] Open
Abstract
Pathogenic variants in the GJB2 gene, encoding connexin 26, are known to be a major cause of hearing impairment (HI). More than 300 allelic variants have been identified in the GJB2 gene. Spectrum and allelic frequencies of the GJB2 gene vary significantly among different ethnic groups worldwide. Until now, the spectrum and frequency of the pathogenic variants in exon 1, exon 2 and the flanking intronic regions of the GJB2 gene have not been described thoroughly in the Sakha Republic (Yakutia), which is located in a subarctic region in Russia. The complete sequencing of the non-coding and coding regions of the GJB2 gene was performed in 393 patients with HI (Yakuts—296, Russians—51, mixed and other ethnicities—46) and in 187 normal hearing individuals of Yakut (n = 107) and Russian (n = 80) populations. In the total sample (n = 580), we revealed 12 allelic variants of the GJB2 gene, 8 of which were recessive pathogenic variants. Ten genotypes with biallelic recessive pathogenic variants in the GJB2 gene (in a homozygous or a compound heterozygous state) were found in 192 out of 393 patients (48.85%). We found that the most frequent GJB2 pathogenic variant in the Yakut patients was c.-23+1G>A (51.82%) and that the second most frequent was c.109G>A (2.37%), followed by c.35delG (1.64%). Pathogenic variants с.35delG (22.34%), c.-23+1G>A (5.31%), and c.313_326del14 (2.12%) were found to be the most frequent among the Russian patients. The carrier frequencies of the c.-23+1G>A and с.109G>A pathogenic variants in the Yakut control group were 10.20% and 2.80%, respectively. The carrier frequencies of с.35delG and c.101T>C were identical (2.5%) in the Russian control group. We found that the contribution of the GJB2 gene pathogenic variants in HI in the population of the Sakha Republic (48.85%) was the highest among all of the previously studied regions of Asia. We suggest that extensive accumulation of the c.-23+1G>A pathogenic variant in the indigenous Yakut population (92.20% of all mutant chromosomes in patients) and an extremely high (10.20%) carrier frequency in the control group may indicate a possible selective advantage for the c.-23+1G>A carriers living in subarctic climate.
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Affiliation(s)
- Nikolay A. Barashkov
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
- * E-mail:
| | - Vera G. Pshennikova
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Olga L. Posukh
- Laboratory of Human Molecular Genetics, Federal Research Center, Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russian Federation
- Novosibirsk State University, Novosibirsk, Russian Federation
| | - Fedor M. Teryutin
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Aisen V. Solovyev
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Leonid A. Klarov
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Department of Radiology, Republican Hospital # 2 –Center of Emergency Medicine, Ministry of Public Health of the Sakha Republic, Yakutsk, Russian Federation
| | - Georgii P. Romanov
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Nyurgun N. Gotovtsev
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Andrey A. Kozhevnikov
- Republican Centre of Professional Pathology, Republican Hospital # 2 –Center of Emergency Medicine, Ministry of Public Health of the Sakha Republic, Yakutsk, Russian Federation
| | - Elena V. Kirillina
- Institute of Foreign Philology and Regional Studies, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Oksana G. Sidorova
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
| | - Lena M. Vasilyevа
- Audiology-Logopaedic Centre, Republican Hospital #1– National Medical Centre, Ministry of Public Health of the Sakha Republic, Yakutsk, Russian Federation
| | - Elvira E. Fedotova
- Audiology-Logopaedic Centre, Republican Hospital #1– National Medical Centre, Ministry of Public Health of the Sakha Republic, Yakutsk, Russian Federation
| | - Igor V. Morozov
- Novosibirsk State University, Novosibirsk, Russian Federation
- SB RAS Genomics Core Facility, Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russian Federation
| | - Alexander A. Bondar
- SB RAS Genomics Core Facility, Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russian Federation
| | - Natalya A. Solovyevа
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Sardana K. Kononova
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Adyum M. Rafailov
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Nikolay N. Sazonov
- Department of Biochemistry and Biotechnology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
| | - Anatoliy N. Alekseev
- Institute of Humanitarian Research and Indigenous Peoples of the North, Siberian Branch of the Russian Academy of Sciences, Yakutsk, Russian Federation
| | - Mikhail I. Tomsky
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
| | - Lilya U. Dzhemileva
- Laboratory of Human Molecular Genetics, Institute of Biochemistry and Genetics, Ufa Scientific Centre, Russian Academy of Sciences, Ufa, Russian Federation
- Department of Immunology and Human Reproductive Health, Bashkir State Medical University, Ufa, Russian Federation
| | - Elza K. Khusnutdinova
- Laboratory of Human Molecular Genetics, Institute of Biochemistry and Genetics, Ufa Scientific Centre, Russian Academy of Sciences, Ufa, Russian Federation
- Department of Genetics and Fundamental Medicine, Bashkir State University, Ufa, Russian Federation
| | - Sardana A. Fedorova
- Department of Molecular Genetics, Federal State Budgetary Scientific Institution “Yakut Science Centre of Complex Medical Problems,” Yakutsk, Russian Federation
- Laboratory of Molecular Biology, Institute of Natural Sciences, M.K. Ammosov North-Eastern Federal University, Yakutsk, Russian Federation
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Etiology and associated GJB2 mutations in Mauritanian children with non-syndromic hearing loss. Eur Arch Otorhinolaryngol 2016; 273:3693-3698. [PMID: 27067584 DOI: 10.1007/s00405-016-4036-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 04/06/2016] [Indexed: 01/23/2023]
Abstract
Origins of all hearing impairment forms may be divided into genetic mutations and acquired influence. Both carry damage to the inner ear structure resulting in a mild to profound dysfunction of the auditory system. The purpose of this study was to assess the different etiologies of deafness in two reference centers for hearing-impaired children in Nouakchott/Mauritania. Data on gender, age, consanguinity, etiology and family history of deafness were gathered by interviewing the custodians of 139 children with hearing loss. DNA of pupils with hereditary non-syndromic deafness was then screened for GJB2 mutations by sequencing methods. Postnatal hearing loss was found in 36 (25.8 %) out of the 139 children surveyed. The main etiologies of this group were infections caused by meningitis (12.9 %) and measles (2.8 %). Unknown and ototoxic origins accounted for, respectively, 5.7 and 3.5 %. In 103 (74.1 %) children, deafness was identified near after the time of birth and, therefore, presumed as congenital. 56.8 % of deaf children had consanguineous parents. Two GJB2 mutations, c.del35G with an allele frequency of 4.7 % and R32C (3.7 %) were detected. Infections such as meningitis and measles were the most prevalent causes of postnatal deafness. In cases of congenital hearing impairment, two GJB2 allele variants, i.e., del35G and R32C (3.7 %) were detected. Extended genetic testing is recommended for a more comprehensive determination of congenital causes.
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Lebeko K, Bosch J, Noubiap JJN, Dandara C, Wonkam A. Genetics of hearing loss in Africans: use of next generation sequencing is the best way forward. Pan Afr Med J 2015; 20:383. [PMID: 26185573 PMCID: PMC4499266 DOI: 10.11604/pamj.2015.20.383.5230] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 09/27/2014] [Indexed: 11/11/2022] Open
Abstract
Hearing loss is the most common communication disorder affecting about 1-7/1000 births worldwide. The most affected areas are developing countries due toextensively poor health care systems. Environmental causes contribute to 50-70% of cases, specifically meningitis in sub-Saharan Africa. The other 30-50% is attributed to genetic factors. Nonsyndromic hearing loss is the most common form of hearing loss accounting for up to 70% of cases. The most common mode of inheritance is autosomal recessive. The most prevalent mutations associated with autosomal recessive nonsyndromic hearing loss (ARNSHL) are found within connexin genes such as GJB2, mostly in people of European and Asian origin. For example, the c.35delG mutation ofGJB2 is found in 70% of ARNSHL patients of European descentand is rare in populations of otherethnicities. Other GJB2 mutations have been reported in various populations. The second most common mutations are found in theconnexin gene, GJB6, also with a high prevalencein patients of European descent. To date more than 60 genes have been associated with ARNSHL. We previously showed that mutations in GJB2, GJB6 and GJA1 are not significant causes of ARNSHL inpatients from African descents, i.e. Cameroonians and South AfricansIn order to resolve ARNSHL amongst sub-Saharan African patients, additional genes would need to be explored. Currently at least 60 genes are thought to play a role in ARNSHL thus the current approach using Sanger sequencing would not be appropriate as it would be expensive and time consuming. Next Generation sequencing (NGS) provides the best alternative approach. In this review, we reported on the success of using NGSas observed in various populations and advocate for the use of NGS to resolve cases of ARNSHL in sub-Saharan African populations.
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Affiliation(s)
- Kamogelo Lebeko
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Jason Bosch
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | | | - Collet Dandara
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa ; Institute for Infectious Disease and Molecular Medicine (IDM), Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
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Wonkam A. Letter to the editor regarding "GJB2, GJB6 or GJA1 genes should not be investigated in routine in non syndromic deafness in people of sub-Saharan African descent". Int J Pediatr Otorhinolaryngol 2015; 79:632-3. [PMID: 25639550 DOI: 10.1016/j.ijporl.2015.01.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 01/13/2015] [Indexed: 10/24/2022]
Affiliation(s)
- Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town (UCT), South Africa.
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Jing W, Zongjie H, Denggang F, Na H, Bin Z, Aifen Z, Xijiang H, Cong Y, Yunping D, Ring HZ, Ring BZ. Mitochondrial mutations associated with aminoglycoside ototoxicity and hearing loss susceptibility identified by meta-analysis. J Med Genet 2014; 52:95-103. [PMID: 25515069 DOI: 10.1136/jmedgenet-2014-102753] [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] [Indexed: 11/04/2022]
Abstract
BACKGROUND Genetic variations, including mitochondrial mutations, are important contributors to hearing loss, especially in children, and newborn genetic screens for hearing loss mutations are becoming increasingly common. Mitochondrial mutations have been linked with ototoxic responses to common antibiotics, therefore understanding the association of these mutations with hearing loss is of special importance. To address the usefulness of screening for these mutations in a clinical setting, we formed a collaboration of clinicians and geneticists to analyse the association of mitochondrial mutations with non-syndromic hearing loss, including the effect of ethnicity, audiological test methods and aminoglycoside exposure. METHODS This survey identified 122 variants in 43 studies that have been assessed for an association with hearing loss, and meta-analysis was performed on clinically relevant subsets. RNA folding and conservation analysis further explored possible relevance of these variants. RESULTS Among all studies, eight variants were found to have significant associations with hearing loss. A partially overlapping set of six variants had significant association with hearing loss when aminoglycoside exposure was assessed. Five of these variants predictive of sensitivity to aminoglycoside spatially co-localise in an RNA folding model. There was little effect of the audiological test method used to assess hearing loss on the association with the variants. CONCLUSIONS Our results found a small set of studied variants had reproducible association with hearing loss, which will help clarify mutations useful in genetic screens for hearing loss. Several of the aminoglycoside exposure-associated mutations may co-localise on folded 12S rRNA, suggesting a functional association between these loci and aminoglycoside-induced hearing loss.
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Affiliation(s)
- Wu Jing
- Institute of Genomic and Personalized Medicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Hao Zongjie
- Institute of Genomic and Personalized Medicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Fu Denggang
- Institute of Genomic and Personalized Medicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Hei Na
- Institute of Genomic and Personalized Medicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Zhang Bin
- Wuhan Women and Children Hospital, Wuhan, Hubei, China
| | - Zhou Aifen
- Wuhan Women and Children Hospital, Wuhan, Hubei, China
| | - Hu Xijiang
- Wuhan Women and Children Hospital, Wuhan, Hubei, China
| | - Yao Cong
- Wuhan Women and Children Hospital, Wuhan, Hubei, China
| | | | - Huijun Z Ring
- Institute of Genomic and Personalized Medicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Brian Z Ring
- Institute of Genomic and Personalized Medicine, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
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Common genes for non-syndromic deafness are uncommon in sub-Saharan Africa: a report from Nigeria. Int J Pediatr Otorhinolaryngol 2014; 78:1870-3. [PMID: 25218342 PMCID: PMC4208623 DOI: 10.1016/j.ijporl.2014.08.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 08/10/2014] [Accepted: 08/11/2014] [Indexed: 02/02/2023]
Abstract
INTRODUCTION Little is known about the molecular epidemiology of deafness in sub-Saharan Africa (SSA). Even in Nigeria, the most populous African nation, no genetic studies of deafness have been conducted. This pioneering work aims at investigating the frequencies of gene mutations relatively common in other parts of the world (i.e. those in GJB2, GJB6, and mitochondrial DNA) among subjects from Nigeria with hearing loss (HL) with no evidence of acquired pathology or syndromic findings. In addition, we review the literature on the genetics of deafness in SSA. METHOD We evaluated 81 unrelated deaf probands from the Yoruba tribe residing in Ibadan, a suburban city in Nigeria, for the aetiology of their deafness. Subjects underwent genetic testing if their history was negative for an environmental cause and physical examination did not find evidence of a syndrome. Both exons of GJB2 and mitochondrial DNA flanking the 1555A>G mutations were PCR-amplified followed by Sanger sequencing. GJB6 deletions were screened via quantitative PCR. RESULT We identified 44 probands who had nonsyndromic deafness with no environmental cause. The age at study time ranged between 8 months and 45 years (mean=24 years) and age at onset was congenital or prelingual (<age 2 years) in 37 (84%) probands and postlingual in 7 (16%) probands. Among these, 35 probands were the only affected members of their families (simplex cases), while there were at least two affected family members in nine cases (multiplex). Molecular analyses did not show a pathogenic variant in any one of the 44 probands studied. CONCLUSION GJB2, GJB6 and mitochondrial DNA 1555A>G mutations were not found among this initial cohort of the deaf in Nigeria. This makes imperative the search for other genes in the aetiology of HL in this population.
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Bosch J, Noubiap JJN, Dandara C, Makubalo N, Wright G, Entfellner JBD, Tiffin N, Wonkam A. Sequencing of GJB2 in Cameroonians and Black South Africans and comparison to 1000 Genomes Project Data Support Need to Revise Strategy for Discovery of Nonsyndromic Deafness Genes in Africans. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2014; 18:705-10. [PMID: 25162826 DOI: 10.1089/omi.2014.0063] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations in the GJB2 gene, encoding connexin 26, could account for 50% of congenital, nonsyndromic, recessive deafness cases in some Caucasian/Asian populations. There is a scarcity of published data in sub-Saharan Africans. We Sanger sequenced the coding region of the GJB2 gene in 205 Cameroonian and Xhosa South Africans with congenital, nonsyndromic deafness; and performed bioinformatic analysis of variations in the GJB2 gene, incorporating data from the 1000 Genomes Project. Amongst Cameroonian patients, 26.1% were familial. The majority of patients (70%) suffered from sensorineural hearing loss. Ten GJB2 genetic variants were detected by sequencing. A previously reported pathogenic mutation, g.3741_3743delTTC (p.F142del), and a putative pathogenic mutation, g.3816G>A (p.V167M), were identified in single heterozygous samples. Amongst eight the remaining variants, two novel variants, g.3318-41G>A and g.3332G>A, were reported. There were no statistically significant differences in allele frequencies between cases and controls. Principal Components Analyses differentiated between Africans, Asians, and Europeans, but only explained 40% of the variation. The present study is the first to compare African GJB2 sequences with the data from the 1000 Genomes Project and have revealed the low variation between population groups. This finding has emphasized the hypothesis that the prevalence of mutations in GJB2 in nonsyndromic deafness amongst European and Asian populations is due to founder effects arising after these individuals migrated out of Africa, and not to a putative "protective" variant in the genomic structure of GJB2 in Africans. Our results confirm that mutations in GJB2 are not associated with nonsyndromic deafness in Africans.
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Affiliation(s)
- Jason Bosch
- 1 Division of Human Genetics, Faculty of Health Sciences, University of Cape Town , Cape Town, South Africa
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Javidnia H, Carson N, Awubwa M, Byaruhanga R, Mack D, Vaccani JP. Connexin gene mutations among Ugandan patients with nonsyndromic sensorineural hearing loss. Laryngoscope 2014; 124:E373-6. [PMID: 24706568 DOI: 10.1002/lary.24697] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 03/31/2014] [Accepted: 04/02/2014] [Indexed: 11/06/2022]
Abstract
OBJECTIVES/HYPOTHESIS Congenital deafness occurs in approximately 1 in 1,000 live births, and 50% of these cases are hereditary. Connexin mutations have been identified as the most common cause of hereditary hearing loss in many populations. The prevalence of this mutation in African patients has not been adequately studied. The objective of this study was to determine the prevalence of connexin 26 and 30 mutations in a population of hearing-impaired patients from Uganda. STUDY DESIGN This is an observational study. METHODS Coding regions of both GJB2 and GJB6, noncoding exon 1 of GJB2, and 30 nucleotides of intronic sequence bordering the exons were analyzed in 126 subjects from Uganda with confirmed bilateral, severe-to-profound sensorineural hearing loss. All variants were analyzed for possible clinical significance using a combination of database searches and in silico tools. RESULTS Complete sequence data were obtained on 115/126 individuals; 11 had only partial or no results. Only one reported pathogenic variant was found in GJB2 (c.208C>G; p.Pro70Ala) and none in GJB6. Three reported variants and two novel variants within intron 1 of GJB2 and two variants within exon 3 of GJB6 were also found. CONCLUSIONS None of the most common types of deletions in the GJB2 gene (c.35delG, c.167delT or c.235delC) were found in this large cohort of deaf children from Uganda. This prompts a search for genetic causes of deafness among this and other previously studied African populations.
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Affiliation(s)
- Hedyeh Javidnia
- Department of Otolaryngology, Head and Neck Surgery, The Ottawa Hospital, Ottawa, Ontario, Canada
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Bosch J, Lebeko K, Nziale JJN, Dandara C, Makubalo N, Wonkam A. In search of genetic markers for nonsyndromic deafness in Africa: a study in Cameroonians and Black South Africans with the GJB6 and GJA1 candidate genes. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2014; 18:481-5. [PMID: 24785695 DOI: 10.1089/omi.2013.0166] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Deafness is the most common sensory disability in the world and has a variety of causes. Globally, mutations in GJB2 have been shown to play a major role in nonsyndromic deafness, but this has not been seen in Africans. Two other connexin genes, GJB6 and GJA1, have been implicated in hearing loss but have seldom been investigated in African populations. We set out to investigate the role of genetic variation in GJB6 and GJA1 in a group of Cameroonian and South African Blacks with nonsyndromic recessive hearing loss. A subset of 100 patients, affected with nonsyndromic hearing loss, from a cohort that was previously shown not to have GJB2 mutation, was analyzed by Sanger sequencing of the entire coding regions of GJB6 and GJA1. In addition, the large-scale GJB6-D3S1830 deletion was also investigated. No pathogenic mutation was detected in either GJB6 or GJA1, nor was the GJB6-D3S1830 deletion detected. There were no statistically significant differences in sequence variants between patients and controls. Mutations in GJB6 and GJA1 are not a major cause of nonsyndromic deafness in this group of Africans from Cameroon and South Africa. Currently, there is no sufficient evidence to support their testing in a clinical setting for individuals of African ancestry.
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Affiliation(s)
- Jason Bosch
- 1 Division of Human Genetics, Department of Clinical Laboratory Sciences, Faculty of Health Sciences, University of Cape Town , Cape Town, South Africa
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Chan DK, Chang KW. GJB2-associated hearing loss: Systematic review of worldwide prevalence, genotype, and auditory phenotype. Laryngoscope 2013; 124:E34-53. [DOI: 10.1002/lary.24332] [Citation(s) in RCA: 183] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2013] [Indexed: 12/17/2022]
Affiliation(s)
- Dylan K. Chan
- Department of Otolaryngology-Head and Neck Surgery; University of California; San Francisco U.S.A
| | - Kay W. Chang
- Department of Otolaryngology-Head and Neck Surgery; Stanford University School of Medicine; Stanford California U.S.A
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Wonkam A, Noubiap JJN, Bosch J, Dandara C, Toure GB. Heterozygous p.Asp50Asn mutation in the GJB2 gene in two Cameroonian patients with keratitis-ichthyosis-deafness (KID) syndrome. BMC MEDICAL GENETICS 2013; 14:81. [PMID: 23924173 PMCID: PMC3750395 DOI: 10.1186/1471-2350-14-81] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 08/07/2013] [Indexed: 11/10/2022]
Abstract
BACKGROUND Keratitis-Ichthyosis-Deafness (KID) syndrome (OMIM 148210) is a congenital ectodermal defect that consists of an atypical ichthyosiform erythroderma associated with congenital sensorineural deafness. KID appears to be genetically heterogeneous and most cases are caused by GJB2 mutations. Mutations in African patients have been rarely described. CASE PRESENTATION We report on two unrelated Cameroonian individuals affected with sporadic KID, presenting with the classic phenotypic triad. The two patients were heterozygous for the most frequent p.Asp50Asn mutation. This first report in patients from sub-Saharan African origin supports the hypothesis that the occurrence of KID due to p.Asp50Asn mutation in GJB2 seems not to be population specific. CONCLUSIONS Our finding has implication in medical genetic practice, specifically in the molecular diagnosis of KID in Africans. These cases also reveal and emphasize the urgent need to develop appropriate policies to care for patients with rare/orphan diseases in Sub-Saharan Africa, as many of these cases become more and more recognizable.
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Affiliation(s)
- Ambroise Wonkam
- Division of Human Genetics, Department of Clinical Laboratory Sciences, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
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Manzoli GN, Abe-Sandes K, Bittles AH, da Silva DSD, Fernandes LDC, Paulon RMC, de Castro ICS, Padovani CMCA, Acosta AX. Non-syndromic hearing impairment in a multi-ethnic population of Northeastern Brazil. Int J Pediatr Otorhinolaryngol 2013; 77:1077-82. [PMID: 23684175 DOI: 10.1016/j.ijporl.2013.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Revised: 03/30/2013] [Accepted: 04/01/2013] [Indexed: 01/28/2023]
Abstract
OBJECTIVE There are many hearing impaired individuals in Monte Santo, a rural municipality in the state of Bahia, Brazil, including multiple familial cases strongly suggestive of a genetic aetiology. METHODS The present study investigated 81 subjects with hearing impairment (HI) recruited from 36 families. Mutations often associated with HI, i.e. the DFNB1 mutations c.35delG in GJB2, deletions del(GJB6-D13S1830) and del(GJB6-D13S1854), and A1555G in the mitochondrial gene MTRNR1 were initially analyzed, with additional mutations in GJB2 identified by sequencing the coding region of the gene. RESULTS Seven different mutations were present in GJB2 with mutations c.35delG and p.Arg75Gln, which are known to be pathogenic, identified in 37.0% of the subjects. Individuals homozygous for the c.35delG mutation were diagnosed in eight families, corresponding to 24.7% of unrelated individuals with nonsyndromic hearing impairment (NSHI), and an additional heterozygote for this mutation was present in a single family. Ten individuals (12.4%) in another family were heterozygous for the mutation p.Arg75Gln. CONCLUSIONS Significant heterogeneity was observed in the alleles and patterns of NSHI inheritance among the subjects studied, probably due to the extensive inter-ethnic admixture that characterizes the peoples of Brazil, together with a high prevalence of community endogamy and consanguineous marriage.
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Affiliation(s)
- Gabrielle N Manzoli
- Advanced Laboratory of Public Health/Gonçalo Moniz Research Center (CPqGM), Oswaldo Cruz Foundation (FIOCRUZ), Salvador, Bahia, Brazil
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Prevalence of DFNB1 mutations among cochlear implant users in Slovakia and its clinical implications. Eur Arch Otorhinolaryngol 2013; 271:1401-7. [PMID: 23700267 DOI: 10.1007/s00405-013-2559-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 05/04/2013] [Indexed: 10/26/2022]
Abstract
Hereditary etiology plays an important role in bilateral profound deafness as a main indication for cochlear implantation. Mutations in DFNB1 locus account for most of the inherited deafness cases in Caucasians. To provide actual data on mutation prevalence among implanted deaf subpopulation, we performed DNA analysis of GJB2 and GJB6 genes in 131 unrelated Slovak cochlear implant users. Eight previously described causal mutations and one probably pathogenic missense variant (c.127G>A) were detected in the GJB2 gene in 58 (44.28%) subjects. The most common mutation found was c.35delG with frequency 83.02% of all disease alleles, followed by c.71G>A, c.1-3201G>A, c.313_326del14, c.109G>A, 167delT, c.269T>C, and c.333_334delAA. GJB6 deletion delD13S1830 was identified in only one subject, in double heterozygosity with a GJB6 mutation. Thus, the deafness cause could be clearly attributable to DFNB1 mutations in 36.64% of the patients examined. In summary, the mutation profile found in our cohort was similar to the mutation spectrum reported for Central European deaf populations. The mutation prevalence in cochlear implant users was, however, almost by 25% higher than previously established for non-implanted hearing-impaired population in Slovakia. Finally, we also demonstrate a certain variability in deafness onset in patients with causal genotype and coincidence with other risk factors for deafness. Our results underline the importance of genetic tests in all cochlear implant candidates.
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de la Luz Arenas-Sordo M, Menendez I, Hernández-Zamora E, Sirmaci A, Gutiérrez-Tinajero D, McGetrick M, Murphy-Ruiz P, Leyva-Juárez X, Huesca-Hernández F, Dominguez-Aburto J, Tekin M. Unique spectrum of GJB2 mutations in Mexico. Int J Pediatr Otorhinolaryngol 2012; 76:1678-80. [PMID: 22925408 DOI: 10.1016/j.ijporl.2012.08.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 08/02/2012] [Accepted: 08/03/2012] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The aim of this study was to elucidate the involvement of mutations in three relatively common deafness genes in Mexican individuals with non-syndromic hearing loss. METHODS We sequenced GJB2 for mutations, screened for two deletions involving GJB6, del(GJB6-D13S1830) and del(GJB6-D13S1854), and for the m.1555A>G mutation in the MTRNR1 gene in 76 (71 simplex and 5 multiplex) unrelated Mexican probands with prelingual non-syndromic hearing loss. Samples were obtained from the Department of Genetics at Instituto Nacional de Rehabilitacion in Mexico City. RESULTS Eight previously reported pathogenic variants and two polymorphic variants in GJB2 were identified. The two screened GJB6 deletions and the m.1555A>G mutation were not detected. Eight cases (10.6%) were found to have bi-allelic mutations in GJB2 and six (7.9%) were found to have a monoallelic GJB2 mutation. Of the six monoallelic mutations, one (p.R184Q) was a previously reported autosomal dominant variant. The most frequent pathological allele detected in this population was the c.35delG mutation in the GJB2 gene. The p.V27I polymorphic variant was also detected, with an allele frequency of 0.24. All eight probands with GJB2 mutations had symmetric profound deafness, whereas patients without GJB2 mutations had moderate, severe or profound hearing loss. CONCLUSIONS This study shows that GJB2 mutations are an important cause of prelingual deafness in the Mexican population.
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Affiliation(s)
- Maria de la Luz Arenas-Sordo
- Departamento de Genetica, Instituto Nacional de Rehabilitacion, Calzada de Mexico Xochimilco No. 289, Colonia Arenal de Guadalupe, Delegacion Tlalpan, Mexico CP 14389, Mexico
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Vivero RJ, Ouyang X, Yan D, Du L, Liu W, Angeli SI, Liu XZ. Mitochondrial DNA mutation screening in an ethnically diverse nonsyndromic deafness cohort. Genet Test Mol Biomarkers 2012; 16:1146-8. [PMID: 22853457 DOI: 10.1089/gtmb.2011.0365] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Deafness is a heterogeneous trait with many known genetic and environmental causes. Hereditary hearing loss is an extremely common disorder in the general population. Mutations in mitochondrial DNA (mtDNA) are known to be associated with nonsyndromic deafness (NSD) and syndromic deafness. The objective of this article is to investigate the frequency of common mitochondrial mutations (A1555G, G7444A, and A3243G) in an ethnically diverse cohort of probands with NSD from South Florida. These patients were ascertained at the University of Miami. Polymerase chain reaction-restriction fragment length polymorphism analysis and direct sequencing methods were used for mutation screening in a cohort of 217 patients with NSD. The frequency of common mitochondrial mutations is 1.84% (4/217) in this cohort. A1555G and G7444A accounted for four patients with NSD. Our mutation frequencies are comparable with those previously reported in other populations, indicating that mutations in mtDNA are an important cause of NSD in our patient cohort.
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Affiliation(s)
- Richard J Vivero
- Department of Otolaryngology, University of Miami Ear Institute, Miami, Florida 33136, USA
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Zainal SA, Md Daud MK, Abd Rahman N, Zainuddin Z, Alwi Z. Mutation detection in GJB2 gene among Malays with non-syndromic hearing loss. Int J Pediatr Otorhinolaryngol 2012; 76:1175-9. [PMID: 22613756 DOI: 10.1016/j.ijporl.2012.04.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 04/26/2012] [Accepted: 04/27/2012] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To identify the mutations in the GJB2 gene and to determine its association with non-syndromic hearing loss in Malays. METHODS A comparative cross sectional study was conducted on a group of children from the deaf schools and the normal schools. A total of 91 buccal cell samples of non-syndromic hearing loss and 91 normal hearing children were taken. Polymerase chain reaction was used to amplify the coding region of GJB2 gene. The PCR product of GJB2 coding region was preceded with screening for mutations using denaturing high performance liquid chromatography (dHPLC) and mutations detected were confirmed by DNA sequencing. RESULTS Twelve sequence variations including mutations and polymorphisms were found in 32 patients and 37 control subjects. The variations were G4D, V27I, E114G, T123N, V37I and R127H in both groups, W24X, R32H, 257_259 del CGC and M34L in patients only and I203T and V153I in control subjects only. There were no association between homozygous (P=0.368) or heterozygous (P=0.164) GJB2 gene and non-syndromic hearing loss. CONCLUSIONS The types of GJB2 gene mutation were different and vary in Malay non-syndromic hearing loss as compared to the other races. Furthermore, the mutation did not associate with hearing loss in the population. Other related genes are believed to be involved and need to be sought in this group of patients.
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Affiliation(s)
- Siti Aishah Zainal
- Human Genome Center, School of Medical Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
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Charif M, Abidi O, Boulouiz R, Nahili H, Rouba H, Kandil M, Delprat B, Lenaers G, Barakat A. Molecular analysis of the TMPRSS3 gene in Moroccan families with non-syndromic hearing loss. Biochem Biophys Res Commun 2012; 419:643-7. [PMID: 22382023 DOI: 10.1016/j.bbrc.2012.02.066] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 02/13/2012] [Indexed: 11/18/2022]
Abstract
Autosomal recessive non-syndromic hearing impairment (ARNSHI) is the most common type of inherited hearing impairment, accounting for approximately 80% of inherited prelingual hearing impairment. Hearing loss is noted to be both phenotypically and genetically heterogeneous. Mutations in the TMPRSS3 gene, which encodes a transmembrane serine protease, are known to cause autosomal recessive non-syndromic hearing impairment DFNB8/10. In order to elucidate if the TMPRSS3 gene is responsible for ARNSHI in 80 Moroccan families with non-syndromic hearing impairment, the gene was sequenced using DNA samples from these families. Nineteen TMPRSS3 variants were found, nine are located in the exons among which six are missense and three are synonymous. The 10 remaining variations are located in non-coding regions. Missense variants analysis show that they do not have a significant pathogenic effect on protein while pathogenicity of some variant remains under discussion. Thus we show that the TMPRSS3 gene is not a major contributor to non-syndromic deafness in the Moroccan population.
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Affiliation(s)
- Majida Charif
- Laboratoire de Génétique Moléculaire et Humaine, Département de Recherche Scientifique, Institut Pasteur du Maroc, 20360 Casablanca, Morocco
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