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Tang HY, Xia A, Oghalai JS, Pereira FA, Alford RL. High frequency of the IVS2-2A>G DNA sequence variation in SLC26A5, encoding the cochlear motor protein prestin, precludes its involvement in hereditary hearing loss. BMC MEDICAL GENETICS 2005; 6:30. [PMID: 16086836 PMCID: PMC1190179 DOI: 10.1186/1471-2350-6-30] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Accepted: 08/08/2005] [Indexed: 11/10/2022]
Abstract
BACKGROUND Cochlear outer hair cells change their length in response to variations in membrane potential. This capability, called electromotility, is believed to enable the sensitivity and frequency selectivity of the mammalian cochlea. Prestin is a transmembrane protein required for electromotility. Homozygous prestin knockout mice are profoundly hearing impaired. In humans, a single nucleotide change in SLC26A5, encoding prestin, has been reported in association with hearing loss. This DNA sequence variation, IVS2-2A>G, occurs in the exon 3 splice acceptor site and is expected to abolish splicing of exon 3. METHODS To further explore the relationship between hearing loss and the IVS2-2A>G transition, and assess allele frequency, genomic DNA from hearing impaired and control subjects was analyzed by DNA sequencing. SLC26A5 genomic DNA sequences from human, chimp, rat, mouse, zebrafish and fruit fly were aligned and compared for evolutionary conservation of the exon 3 splice acceptor site. Alternative splice acceptor sites within intron 2 of human SLC26A5 were sought using a splice site prediction program from the Berkeley Drosophila Genome Project. RESULTS The IVS2-2A>G variant was found in a heterozygous state in 4 of 74 hearing impaired subjects of Hispanic, Caucasian or uncertain ethnicity and 4 of 150 Hispanic or Caucasian controls (p = 0.45). The IVS2-2A>G variant was not found in 106 subjects of Asian or African American descent. No homozygous subjects were identified (n = 330). Sequence alignment of SLC26A5 orthologs demonstrated that the A nucleotide at position IVS2-2 is invariant among several eukaryotic species. Sequence analysis also revealed five potential alternative splice acceptor sites in intron 2 of human SLC26A5. CONCLUSION These data suggest that the IVS2-2A>G variant may not occur more frequently in hearing impaired subjects than in controls. The identification of five potential alternative splice acceptor sites in intron 2 of human SLC26A5 suggests a potential mechanism by which expression of prestin might be maintained in cells carrying the SLC26A5 IVS2-2A>G DNA sequence variation. Additional studies are needed to evaluate the effect of the IVS2-2A>G transition on splicing of SLC26A5 transcripts and characterize the hearing status of individuals homozygous for the IVS2-2A>G variant.
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Affiliation(s)
- Hsiao-Yuan Tang
- The Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030, USA
| | - Anping Xia
- The Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030, USA
| | - John S Oghalai
- The Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030, USA
| | - Fred A Pereira
- The Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030, USA
- Huffington Center on Aging and Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, N710, Houston, TX 77030, USA
| | - Raye L Alford
- The Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030, USA
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Rodríguez-Soriano J, Vallo A, Pérez de Nanclares G, Bilbao JR, Castaño L. A founder mutation in the CLCNKB gene causes Bartter syndrome type III in Spain. Pediatr Nephrol 2005; 20:891-6. [PMID: 15875219 DOI: 10.1007/s00467-005-1867-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2004] [Revised: 01/10/2005] [Accepted: 01/10/2005] [Indexed: 12/11/2022]
Abstract
The term "Bartter syndrome" encompasses a group of closely related inherited tubulopathies characterized by markedly reduced NaCl transport by the distal nephron. At present, five different genetic variants have been demonstrated. The majority of patients with so-called classic Bartter syndrome carry inactivating mutations of the CLCNKB gene encoding the basolateral ClC-Kb chloride channel (Bartter syndrome type III). The purpose of this study was to investigate the underlying mutation in cases of classic Bartter syndrome followed at our center. Ten patients, including two sisters, with clinical and biochemical features of classic Bartter syndrome were included in the mutational analysis. They originated from different regions of Spain with either Basque or Spanish ancestry. There was no history of consanguineous marriage in any of the kindreds. The parents and siblings of each patient, as well as a population of 300 healthy control adult subjects, were also analyzed. All ten patients were found to be homozygous for an identical missense mutation in the CLCNKB gene, substituting a threonine for an alanine at codon 204 (A204T) in the putative fifth transmembrane domain of the protein. None of the 300 control subjects were homozygous for the A204T allele. Overall, the A204T mutation was detected on 2/600 control chromosomes. Despite sharing a common mutation, the clinical manifestations of the syndrome in the patients varied from lack of symptoms to severe growth retardation. Demonstration of a point mutation within the CLCNKB gene as the apparently unique cause of Bartter syndrome type III in Spain is highly suggestive of a founder effect. Our results also support the lack of correlation between genotype and phenotype in this disease.
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Affiliation(s)
- Juan Rodríguez-Soriano
- Division of Pediatric Nephrology and Research Unit, Department of Pediatrics, Hospital de Cruces and Basque University School of Medicine, Bilbao, País Vasco, Spain.
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Snoeckx RL, Djelantik B, Van Laer L, Van de Heyning P, Van Camp G. GJB2 (connexin 26) mutations are not a major cause of hearing loss in the Indonesian population. Am J Med Genet A 2005; 135:126-9. [PMID: 15832357 DOI: 10.1002/ajmg.a.30726] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Although hereditary hearing loss is a very heterogeneous disorder, variants in one gene, GJB2 (connexin 26), account for up to 50% of autosomal recessive nonsyndromal sensorineural hearing loss in most populations. This study investigates the contribution of GJB2 to autosomal recessive nonsyndromal hearing loss in the Indonesian population. We performed DNA sequence analysis in 120 patients with profound early childhood nonsyndromal hearing loss and in 100 control individuals and identified three novel variations resulting in amino acid substitutions (p.Gly4Asp, p.Thr5Ala, and p.Gly160Arg). Although we proved that p.Gly4Asp was not disease-causing, the pathological nature of p.Thr5Ala and p.Gly160Arg could not be determined. No recurrent disease-causing mutation could be detected in this Indonesian population. These findings are in contrast with the results obtained in other populations where GJB2 is a major cause of congenital recessive hearing loss.
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Affiliation(s)
- Rikkert L Snoeckx
- Department of Medical Genetics, University of Antwerp, Universiteitsplein, Antwerp, Belgium
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204
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Seeman P, Bendová O, Rasková D, Malíková M, Groh D, Kabelka Z. Double heterozygosity with mutations involving both the GJB2 and GJB6 genes is a possible, but very rare, cause of congenital deafness in the Czech population. Ann Hum Genet 2005; 69:9-14. [PMID: 15638823 DOI: 10.1046/j.1529-8817.2003.00120.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutations in the GJB2 gene are the most common cause of prelingual, autosomal recessive, sensorineural hearing loss worldwide. Nevertheless, 10% to 50% of patients with prelingual nonsyndromic deafness only carry one mutation in the GJB2 gene. Recently a large 342 kb deletion named Delta(GJB6-D13S1830) involving the GJB6 gene was reported in Spanish and French deafness patients, either in a homozygous state or in combination with a monoallelic GJB2 mutation. No data have been reported about the frequency of this mutation in central Europe. Thirteen Czech patients with prelingual nonsyndromic sensorineural deafness carrying only one pathogenic mutation in the GJB2 gene were tested for the presence of the Delta(GJB6-D13S1830) mutation. One patient with a GJB2 mutation (313del14) also carried the Delta(GJB6-D13S1830). This is the first reported Czech case, and probably also the first central European case, of prelingual deafness due to mutations involving both the GJB2 and GJB6 genes. In addition, the Delta(GJB6-D13S1830) was not detected in 600 control chromosomes from Czech individuals with normal hearing. We show that in the Czech Republic the Delta(GJB6-D13S1830) is not the second most common causal factor in deafness patients heterozygous for a single GJB2 mutation, and that Delta(GJB6-D13S1830) is very rare in central Europe compared to reports from Spain, France and Israel.
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Affiliation(s)
- P Seeman
- Department of Child Neurology DNA laboratory, Charles University Prague, 2nd School of Medicine, V úvalu 84, 150 06 Praha 5, Czech.
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205
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Kalay E, Caylan R, Kremer H, de Brouwer APM, Karaguzel A. GJB2 mutations in Turkish patients with ARNSHL: prevalence and two novel mutations. Hear Res 2005; 203:88-93. [PMID: 15855033 DOI: 10.1016/j.heares.2004.11.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Accepted: 11/30/2004] [Indexed: 11/19/2022]
Abstract
Mutations in the connexin 26 gene (GJB2) cause a significant proportion of prelingual non-syndromic autosomal recessive deafness in all populations studied so far. To determine the percentage of hearing loss attributed to GJB2 in northeast Turkey, 93 unrelated patients with autosomal recessive non-syndromic hearing loss (ARNSHL) were screened. Seven different mutations were found in 29 of the patients with severe to profound hearing loss. The 35delG mutation was the most common mutation, accounting for 76% of all mutant GJB2 alleles. Four already described mutations, W24X, 310del14, delE120 and R184P and two novel mutations, Q80K and P173S, were identified. The allelic Delta(GJB6-D13S1830), which can cause hearing loss in combination with GJB2 mutations, was not present in our patients. Our results are comparable to those reported in other regions in Turkey and indicate that GJB2 mutations account for about 30% of Turkish patients with ARNSHL. Besides 35delG, W24X and delE120 occur more than once in the Turkish ARNSHL population with a frequency of about 5%.
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Affiliation(s)
- Ersan Kalay
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
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Finsterer J, Fellinger J. Nuclear and mitochondrial genes mutated in nonsyndromic impaired hearing. Int J Pediatr Otorhinolaryngol 2005; 69:621-47. [PMID: 15850684 DOI: 10.1016/j.ijporl.2004.12.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Revised: 12/06/2004] [Accepted: 12/06/2004] [Indexed: 10/25/2022]
Abstract
Half of the cases with congenital impaired hearing are hereditary (HIH). HIH may occur as part of a multisystem disease (syndromic HIH) or as disorder restricted to the ear and vestibular system (nonsyndromic HIH). Since nonsyndromic HIH is almost exclusively caused by cochlear defects, affected patients suffer from sensorineural hearing loss. One percent of the total human genes, i.e. 300-500, are estimated to cause syndromic and nonsyndromic HIH. Of these, approximately 120 genes have been cloned thus far, approximately 80 for syndromic HIH and 42 for nonsyndromic HIH. In the majority of the cases, HIH manifests before (prelingual), and rarely after (postlingual) development of speech. Prelingual, nonsyndromic HIH follows an autosomal recessive trait (75-80%), an autosomal dominant trait (10-20%), an X-chromosomal, recessive trait (1-5%), or is maternally inherited (0-20%). Postlingual nonsyndromic HIH usually follows an autosomal dominant trait. Of the 41 mutated genes that cause nonsyndromic HIH, 15 cause autosomal dominant HIH, 15 autosomal recessive HIH, 6 both autosomal dominant and recessive HIH, 2 X-linked HIH, and 3 maternally inherited HIH. Mutations in a single gene may not only cause autosomal dominant, nonsyndromic HIH, but also autosomal recessive, nonsyndromic HIH (GJB2, GJB6, MYO6, MYO7A, TECTA, TMC1), and even syndromic HIH (CDH23, COL11A2, DPP1, DSPP, GJB2, GJB3, GJB6, MYO7A, MYH9, PCDH15, POU3F4, SLC26A4, USH1C, WFS1). Different mutations in the same gene may cause variable phenotypes within a family and between families. Most cases of recessive HIH result from mutations in a single locus, but an increasing number of disorders is recognized, in which mutations in two different genes (GJB2/GJB6, TECTA/KCNQ4), or two different mutations in a single allele (GJB2) are involved. This overview focuses on recent advances in the genetic background of nonsyndromic HIH.
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Affiliation(s)
- Josef Finsterer
- Department of Neurology, Krankenanstalt Rudolfstiftung, Vienna, Austria.
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Abstract
Tremendous progress has been made in our understanding of the molecular basis of hearing and hearing loss. Through recent advances, we have begun to understand the fascinating biology of the auditory system and unveiled new molecular mechanisms of hearing impairment. Changes in the diagnostic impact of genetic testing have occurred, as well as exciting developments in therapeutic options. Molecular diagnosis, which is already a reality for several hearing-associated genes, will doubtlessly continue to increase in the near future, both in terms of the number of mutations tested and the spectrum of genes. Genetic analysis for hearing loss is mostly used for diagnosis and treatment, and relatively rarely for reproductive decisions, in contrast to other inherited disorders. Inherited hearing loss, however, is characterized by impressive genetic heterogeneity. An abundance of genes carry a large number of mutations, but specific mutations in a single gene may lead to syndromic or non-syndromic hearing loss. Some mutations predominate in individual ethnic groups. For clinical and laboratory diagnosticians, it is challenging to keep abreast of the unfolding discoveries. This review aims to provide the framework pertinent to diagnosticians and a practical approach to mutation analysis in the hearing impaired.
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Affiliation(s)
- Iris Schrijver
- Department of Pathology and Pediatrics, L235, Stanford University Medical Center, 300 Pasteur Drive, Stanford, CA 94305, USA.
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208
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Frei K, Ramsebner R, Lucas T, Hamader G, Szuhai K, Weipoltshammer K, Baumgartner WD, Wachtler FJ, Kirschhofer K. GJB2 mutations in hearing impairment: identification of a broad clinical spectrum for improved genetic counseling. Laryngoscope 2005; 115:461-5. [PMID: 15744158 DOI: 10.1097/01.mlg.0000157855.47143.71] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES/HYPOTHESIS Hearing impairment has a high prevalence affecting approximately 1 in 1000 newborn children. Alterations in the gap junction protein beta 2 (GJB2) and gap junction protein beta 6 (GJB6) are associated with nonsyndromic hearing impairment and should have a significant impact on genetic counseling. STUDY DESIGN Various cases of nonsyndromic hearing impairment were screened for alterations in GJB2 and GJB6 in this clinical study. METHODS The prevalence of mutations in GJB2 encoding for connexin 26 in a patient group with nonsyndromic hearing impairment comprising 45 families and 57 sporadic cases was initially determined by sequencing. The role of GJB2 was then assessed in individuals with hearing impairment (3 families and 20 sporadic cases) who are usually excluded from analysis because of the presence of additional symptoms or in cases in which a role for nongenetic factors cannot be eliminated. In hearing-impaired individuals with heterozygous GJB2 mutations the recently identified 342-kb deletion truncating GJB6 called del(GJB6-D13S1830) as a digenetic component in hearing impairment was excluded by polymerase chain reaction. RESULTS Autosomal recessively inherited GJB2 mutations induced hearing impairment in 25.5% of individuals in the nonsyndromic hearing impairment group. GJB2 alterations were also seen in 17.4% of individuals in whom additional symptoms or a role for nongenetic involvement could not be excluded. In all, 15 different alterations in GJB2 were detected, including the previously unknown 154G>C, 557C>T, and 682C>T mutations, and these were correlated to clinical parameters. CONCLUSION Improved genetic counseling can be performed by screening for GJB2 alterations in patients with nonsyndromic hearing impairment including patients within groups for which a role for exogenetic factors cannot be excluded. Specific genetic counseling for GJB2-linked hearing impairment in heterozygotes will depend on future research.
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Affiliation(s)
- Klemens Frei
- Department of Otorhinolaryngology, Medical University of Vienna, Austria.
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209
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First molecular screening of deafness in the Altai Republic population. BMC MEDICAL GENETICS 2005; 6:12. [PMID: 15790391 PMCID: PMC1079841 DOI: 10.1186/1471-2350-6-12] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Accepted: 03/24/2005] [Indexed: 11/24/2022]
Abstract
Background We studied the molecular basis of NSHL in Republic of Altai (South Siberia, Russia). The Altaians are the indigenous Asian population of the Altai Mountain region considered as a melting-pot and a dispersion center for world-wide human expansions in the past. Methods A total of 76 patients of Altaian, Russian or mixed ethnicity and 130 Altaian controls were analyzed by PCR-DHPLC and sequencing in the GJB2 gene. The GJB6 deletion and the common non-syndromic deafness-causing mitochondrial mutations were also tested when appropriate. Results 8.3% of the Altaian chromosomes were carrying GJB2 mutations versus 46.9% of the Russian chromosomes. The 235delC mutation was predominant among Altaians, whereas the 35delG mutation was most prevalent among Russian patients. Conclusion We found an Asian-specific GJB2 diversity among Altaians, and different GJB2 contribution for deafness in the Altaian and Russian patients. The high carrier frequency of 235delC in Altaians (4.6%) is probably defined by gene drift/founder effect in a particular group. The question whether the Altai region could be one of founder sources for the 235delC mutation widespread in Asia is open.
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210
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Strom CM, Crossley B, Redman JB, Quan F, Buller A, McGinniss MJ, Sun W. Molecular screening for diseases frequent in Ashkenazi Jews: lessons learned from more than 100,000 tests performed in a commercial laboratory. Genet Med 2005; 6:145-52. [PMID: 15354333 DOI: 10.1097/01.gim.0000127267.57526.d1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
PURPOSE To determine the frequency of carriers of Ashkenazi Jewish (AJ) genetic diseases in the US population and compare these numbers with previously published frequencies reported in smaller more isolated cohorts. METHODS A database containing more than 100,000 genotyping assays was queried. Assays for 10 separate AJ genetic diseases where comparisons were made with published data. RESULTS As expected, we observed lower carrier frequencies in a general, US population than those reported in literature. In 2427 patients tested for a panel of 8 AJ diseases, 20 (1:121) were carriers of two diseases and 331 (1:7) were carriers of a single disease. Fifty-three of 7184 (1:306) individuals tested for Gaucher disease had 2 Gaucher Disease mutations indicating a potentially affected phenotype. CONCLUSIONS As the number of AJ diseases increases, progressively more individuals will be identified as carriers of at least one disease.
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Affiliation(s)
- Charles M Strom
- Quest Diagnostics Nichols Institute, 33608 Ortega Highway, San Juan Capistrano, CA 92690, USA
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211
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Santos RLP, Aulchenko YS, Huygen PLM, van der Donk KP, de Wijs IJ, Kemperman MH, Admiraal RJC, Kremer H, Hoefsloot LH, Cremers CWRJ. Hearing impairment in Dutch patients with connexin 26 (GJB2) and connexin 30 (GJB6) mutations. Int J Pediatr Otorhinolaryngol 2005; 69:165-74. [PMID: 15656949 DOI: 10.1016/j.ijporl.2004.08.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Accepted: 08/16/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Despite the identification of mutations in the connexin 26 (GJB2) gene as the most common cause of recessive nonsyndromic hearing loss, the pattern of hearing impairment with these mutations remains inconsistent. Recently a deletion encompassing the GJB6 gene was identified and hypothesized to also contribute to hearing loss. We hereby describe the hearing impairment in Dutch patients with biallelic connexin 26 (GJB2) and GJB2+connexin 30 (GJB6) mutations. METHODS The audiograms of patients who were screened for GJB2 and GJB6 mutations were analysed retrospectively. Standard statistical testing was done for symmetry and shape, while repeated measurement analysis was used to assess the relation between mutation and severity. Progression was also studied via linear regression analysis. RESULTS Of 222 hearing-impaired individuals, 35 exhibited sequence variations; of these 19 had audiograms for study. Hearing loss in patients with biallelic "radical" (i.e. deletions, nonsense and splice site) mutations was significantly worse than in the wild type and heterozygotes (SAS proc GENMOD, p=0.013). The presence of at least one missense mutation in compound heterozygotes tends to lead to better hearing thresholds compared to biallelic radical mutations (p=0.08). One patient with the [35delG]+[del(GJB6-D13S1830)] genotype was severely impaired. Non-progressive hearing impairment was demonstrated in five 35delG homozygotes in individual longitudinal analyses. However a patient with the [299A>C]+[416G>A] genotype showed significant threshold progression in the lower frequencies. Findings on asymmetry and shape were inconclusive. CONCLUSIONS Our data support the hypothesis that severity is a function of genotype and its effect on the amino acid sequence. A bigger cohort is required to establish non-progressivity more definitively.
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Affiliation(s)
- Regie Lyn P Santos
- Department of Epidemiology and Biostatistics, Genetic Epidemiology Unit, Erasmus Medical Center Rotterdam, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands
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Belintani Piatto V, Maria Goloni Bertollo E, Lúcia Sartorato E, Victor Maniglia J. Prevalence of the GJB2 mutations and the del(GJB6-D13S1830) mutation in Brazilian patients with deafness. Hear Res 2005; 196:87-93. [PMID: 15464305 DOI: 10.1016/j.heares.2004.05.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2003] [Accepted: 05/25/2004] [Indexed: 11/25/2022]
Abstract
Mutations in the GJB2 gene are the most common cause of sensorineural non-syndromic deafness in different populations. One specific mutation, 35delG, has accounted for the majority of the mutations detected in the GJB2 gene in many countries. The aim of this study was to determine the prevalence of GJB2 mutations and the del(GJB6-D13S1830) mutation in non-syndromic deaf Brazilians. The 33 unrelated probands were examined by clinical evaluation to exclude syndromic forms of deafness. Mutation analysis in the GJB2 gene and the testing for the del(GJB6-D13S1830) were performed in both the patients and their family members. The 35delG mutation was found in nine of the probands or in 14 of the mutated alleles. The V37I mutation and the del(GJB6-D13S1830) mutation were also found in two patients, both are compound heterozygote with 35delG mutation. These findings strengthen the importance of genetic diagnosis, providing early treatment, and genetic counseling of deaf patients.
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Affiliation(s)
- Vânia Belintani Piatto
- Medical School of São José do Rio Preto, Rua Frei Baltazar, No. 415, Boa Vista, São José do Rio Preto, São Paulo 15025-390, Brazil.
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213
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Najmabadi H, Nishimura C, Kahrizi K, Riazalhosseini Y, Malekpour M, Daneshi A, Farhadi M, Mohseni M, Mahdieh N, Ebrahimi A, Bazazzadegan N, Naghavi A, Avenarius M, Arzhangi S, Smith RJH. GJB2 mutations: Passage through Iran. Am J Med Genet A 2005; 133A:132-7. [PMID: 15666300 DOI: 10.1002/ajmg.a.30576] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Hereditary hearing loss (HHL) is a very common disorder. When inherited in an autosomal recessive manner, it typically presents as an isolated finding. Interestingly and unexpectedly, in spite of extreme heterogeneity, mutations in one gene, GJB2, are the most common cause of congenital severe-to-profound deafness in many different populations. In this study, we assessed the contributions made by GJB2 mutations and chromosome 13 g.1777179_2085947del (the deletion more commonly known as del (GJB6-D13S1830) that includes a portion of GJB6 and is hereafter called Delta(GJB6-D13S1830)) to the autosomal recessive non-syndromic deafness (ARNSD) genetic load in Iran. Probands from 664 different nuclear families were investigated. GJB2-related deafness was found in 111 families (16.7%). The carrier frequency of the 35delG mutation showed a geographic variation that is supported by studies in neighboring countries. Delta(GJB6-D13S1830) was not found. Our prevalence data for GJB2-related deafness reveal a geographic pattern that mirrors the south-to-north European gradient and supports a founder effect in southeastern Europe.
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Affiliation(s)
- Hossein Najmabadi
- Genetics Research Center, The Social Welfare and Rehabilitation Sciences University, Koodakyar Street, Daneshjoo Boulevard, Evin, Tehran, Iran.
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215
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Schimmenti LA, Martinez A, Fox M, Crandall B, Shapiro N, Telatar M, Sininger Y, Grody WW, Palmer CGS. Genetic testing as part of the Early Hearing Detection and Intervention (EHDI) process. Genet Med 2004; 6:521-5. [PMID: 15545749 DOI: 10.1097/01.gim.0000144187.21727.28] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Affiliation(s)
- Lisa A Schimmenti
- Department of Pediatrics and Institute of Human Genetics, University of Minnesota, USA
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216
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Abstract
Genetic screening utilizes analytical approaches adapted for high throughput to identify carrier and affected individuals in a targeted population. Currently, genetic screening focuses on carrier screening, prenatal screening, and newborn screening. Newborn screening should serve as a model for all genetic screening, with more than forty years of experience and numerous lessons learned. As with all genetic screening, there are policy concerns in newborn screening regarding which disorders and technologies should be selected, and how centralized or decentralized the process to set policy should be. The need to share experiences and develop databases transcends all other policy considerations in genetic screening. The future will see population-based screening for adult-onset disorders. However, there needs to be extensive research to define predictive risk for various ethnocultural groups and to determine effective interventions. Ethical concerns regarding the timing of population screening, as well as the scope of use of information, will need to be resolved if genomic medicine will achieve its promise of a predictive, preventive, and personalized medicine.
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Affiliation(s)
- Linda L McCabe
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles 90095, USA.
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217
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Abstract
Gap junctions contain hydrophilic membrane channels that allow direct communication between neighboring cells through the diffusion of ions, metabolites, and small cell signaling molecules. They are made up of a hexameric array of polypeptides encoded by the connexin multi-gene family. Cell-cell communication mediated by connexins is crucial to various cellular functions, including the regulation of cell growth, differentiation, and development. Mutations in connexin genes have been linked to a variety of human diseases, including cardiovascular anomalies, peripheral neuropathy, deafness, skin disorders, and cataracts. In addition to their coupling function, recent studies suggest that connexin proteins may also mediate signaling. This could involve interactions with other protein partners that may play a role not only in connexin assembly, trafficking, gating and turnover, but also in the coordinate regulation of cell-cell communication with cell adhesion and cell motility. The integration of these cell functions is likely to be important in the role of gap junctions in development and disease.
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Affiliation(s)
- Chih-Jen Wei
- Laboratory of Developmental Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.
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Frei K, Ramsebner R, Lucas T, Baumgartner WD, Schoefer C, Wachtler FJ, Kirschhofer K. Screening for monogenetic del(GJB6-D13S1830) and digenic del(GJB6-D13S1830)/GJB2 patterns of inheritance in deaf individuals from Eastern Austria. Hear Res 2004; 196:115-8. [PMID: 15464308 DOI: 10.1016/j.heares.2004.07.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2004] [Accepted: 05/28/2004] [Indexed: 11/19/2022]
Abstract
Genetically caused congenital deafness is a common trait affecting 1 in 2000 newborn children and is predominantly inherited in an autosomal recessive fashion. Genes such as the gap junction protein beta 2 (GJB2) encoding for Connexin (Cx26) and GJB6 (Cx30) are known to cause sensorineural deafness. Autosomal recessive deafness has been linked both to the monogenetic occurrence of mutated GJB2 or the GJB6 deletion del(GJB6-D13S1830) and digenic GJB2/del(GJB6-D13S1830) inheritance. Monogenetic GJB2 alterations are responsible for 25.5% of deafness in the eastern Austrian population. An additional 9.8% are heterozygous carriers of a single GJB2 mutation which is not responsible for deafness alone. Del(GJB6-D13S1830) and GJB2/del(GJB6-D13S1830) mutations have been shown to be the second most frequent cause of deafness in different populations. To address the question of the relevance of mutations in GJB6 either as a monogenetic or a digenic GJB2/del(GJB6-D13S1830) cause of deafness in this population, 76 unrelated individuals (33 families and 43 sporadic cases) were screened using PCR strategies. Similar to studies in other hard of hearing populations with similar or lower carrier frequencies of single GJB2 mutations, the presence of del(GJB6-D13S1830) was not detected in any individual within the patient group. Data therefore exclude a digenetic association of del(GJB6-D13S1830) with heterozygous GJB2 mutations as a cause of deafness in a representative sample of the population from Eastern Austria.
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Affiliation(s)
- Klemens Frei
- Department of Otorhinolaryngology, Medical University of Vienna, AKH-8J, Waehringer Gürtel 18-20, Vienna A-1090, Austria.
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219
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Nance WE, Kearsey MJ. Relevance of connexin deafness (DFNB1) to human evolution. Am J Hum Genet 2004; 74:1081-7. [PMID: 15079193 PMCID: PMC1182073 DOI: 10.1086/420979] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Accepted: 03/09/2004] [Indexed: 11/03/2022] Open
Abstract
The connexins are the subunits of a family of proteins that form gap junctions, allowing ions and small molecules to move between adjacent cells. At least four connexins are expressed in the ear, and, although there are known mutations at >100 loci that can cause deafness, those involving DFNB1, in the interval 13q11-q12 containing the GJB2 and GJB6 genes coding for connexins 26 and 30, are the most frequent cause of recessive deafness in many populations. We have suggested that the combined effects of relaxed selection and linguistic homogamy can explain the high frequency of connexin deafness and may have doubled its incidence in this country during the past 200 years. In this report, we show by computer simulation that assortative mating, in fact, can accelerate dramatically the genetic response to relaxed selection. Along with the effects of gene drift and consanguinity, assortative mating also may have played a key role in the joint evolution and accelerated fixation of genes for speech after they first appeared in Homo sapiens 100,000-150,000 years ago.
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Affiliation(s)
- Walter E Nance
- Department of Human Genetics, Virginia Commonwealth University, Richmond, VA, 23298, USA.
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220
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Brownstein Z, Ben-Yosef T, Dagan O, Frydman M, Abeliovich D, Sagi M, Abraham FA, Taitelbaum-Swead R, Shohat M, Hildesheimer M, Friedman TB, Avraham KB. The R245X mutation of PCDH15 in Ashkenazi Jewish children diagnosed with nonsyndromic hearing loss foreshadows retinitis pigmentosa. Pediatr Res 2004; 55:995-1000. [PMID: 15028842 DOI: 10.1203/01.pdr.0000125258.58267.56] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Usher syndrome is a frequent cause of the combination of deafness and blindness due to retinitis pigmentosa (RP). Five genes are known to underlie different forms of Usher syndrome type I (USH1). In the Ashkenazi Jewish population, the R245X mutation of the PCDH15 gene may be the most common cause of USH1 (Ben-Yosef T, Ness SL, Madeo AC, Bar-Lev A, Wolfman JH, Ahmed ZM, Desnick RK, Willner JP, Avraham KB, Ostrer H, Oddoux C, Griffith AJ, Friedman TB N Engl J Med 348: 1664-1670, 2003). To estimate what percentage of Ashkenazi Jewish children born with profound hearing loss will develop RP due to R245X, we examined the prevalence of the R245X PCDH15 mutation and its carrier rate among Ashkenazi Jews in Israel. Among probands diagnosed with nonsyndromic hearing loss not due to mutations of connexin 26 (GJB2) and/or connexin 30 (GJB6), and below the age of 10, 2 of 20 (10%) were homozygous for the R245X mutation. Among older nonsyndromic deaf individuals, no homozygotes were detected, although one individual was heterozygous for R245X. The carrier rate of the R245X mutation among the normal hearing Ashkenazi population in Israel was estimated at 1%. Ashkenazi Jewish children with profound prelingual hearing loss should be evaluated for the R245X PCDH15 mutation and undergo ophthalmologic evaluation to determine whether they will develop RP. Rehabilitation can then begin before loss of vision. Early use of cochlear implants in such cases may rescue these individuals from a dual neurosensory deficit.
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Affiliation(s)
- Zippora Brownstein
- Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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Roux AF, Pallares-Ruiz N, Vielle A, Faugère V, Templin C, Leprevost D, Artières F, Lina G, Molinari N, Blanchet P, Mondain M, Claustres M. Molecular epidemiology of DFNB1 deafness in France. BMC MEDICAL GENETICS 2004; 5:5. [PMID: 15070423 PMCID: PMC385234 DOI: 10.1186/1471-2350-5-5] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/10/2003] [Accepted: 03/06/2004] [Indexed: 11/23/2022]
Abstract
Background Mutations in the GJB2 gene have been established as a major cause of inherited non syndromic deafness in different populations. A high number of sequence variations have been described in the GJB2 gene and the associated pathogenic effects are not always clearly established. The prevalence of a number of mutations is known to be population specific, and therefore population specific testing should be a prerequisite step when molecular diagnosis is offered. Moreover, population studies are needed to determine the contribution of GJB2 variants to deafness. We present our findings from the molecular diagnostic screening of the GJB2 and GJB6 genes over a three year period, together with a population-based study of GJB2 variants. Methods and results Molecular studies were performed using denaturing High Performance Liquid Chromatograghy (DHPLC) and sequencing of the GJB2 gene. Over the last 3 years we have studied 159 families presenting sensorineural hearing loss, including 84 with non syndromic, stable, bilateral deafness. Thirty families were genotyped with causative mutations. In parallel, we have performed a molecular epidemiology study on more than 3000 dried blood spots and established the frequency of the GJB2 variants in our population. Finally, we have compared the prevalence of the variants in the hearing impaired population with the general population. Conclusion Although a high heterogeneity of sequence variation was observed in patients and controls, the 35delG mutation remains the most common pathogenic mutation in our population. Genetic counseling is dependent on the knowledge of the pathogenicity of the mutations and remains difficult in a number of cases. By comparing the sequence variations observed in hearing impaired patients with those sequence variants observed in general population, from the same ethnic background, we show that the M34T, V37I and R127H variants can not be responsible for profound or severe deafness.
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Affiliation(s)
- Anne-Françoise Roux
- Laboratoire de Génétique Moléculaire, CHU Montpellier, IURC, Montpellier, France
| | | | - Anne Vielle
- Laboratoire de Génétique Moléculaire, CHU Montpellier, IURC, Montpellier, France
| | - Valérie Faugère
- Laboratoire de Génétique Moléculaire, CHU Montpellier, IURC, Montpellier, France
| | - Carine Templin
- Laboratoire de Génétique Moléculaire, CHU Montpellier, IURC, Montpellier, France
| | - Dorothée Leprevost
- Laboratoire de Génétique Moléculaire, CHU Montpellier, IURC, Montpellier, France
| | - Françoise Artières
- Service D'Audiophonologie, Institut St-Pierre, Palavas-Les-Flots, France
| | | | - Nicolas Molinari
- Laboratoire de Biostatistique, Epidémiolgie et Recherche Clinique, IURC, Montpellier
| | | | | | - Mireille Claustres
- Laboratoire de Génétique Moléculaire, CHU Montpellier, IURC, Montpellier, France
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