Reduction of Cellular Expression Levels Is a Common Feature of Functionally Affected Pendrin (SLC26A4) Protein Variants.

Sequence alterations in the pendrin gene (SLC26A4) leading to functionally affected protein variants are frequently involved in the pathogenesis of syndromic and nonsyndromic deafness. Considering the high number of SLC26A4 sequence alterations reported to date, discriminating between functionally affected and unaffected pendrin protein variants is essential in contributing to determine the genetic cause of deafness in a given patient. In addition, identifying molecular features common to the functionally affected protein variants can be extremely useful to design future molecule-directed therapeutic approaches. Here we show the functional and molecular characterization of six previously uncharacterized pendrin protein variants found in a cohort of 58 Brazilian deaf patients. Two variants (p.T193I and p.L445W) were undetectable in the plasma membrane, completely retained in the endoplasmic reticulum and showed no transport function; four (p.P142L, p.G149R, p.C282Y and p.Q413R) showed reduced function and significant, although heterogeneous, expression levels in the plasma membrane. Importantly, total expression levels of all of the functionally affected protein variants were significantly reduced with respect to the wild-type and a fully functional variant (p.R776C), regardless of their subcellular localization. Interestingly, reduction of expression may also reduce the transport activity of variants with an intrinsic gain of function (p.Q413R). As reduction of overall cellular abundance was identified as a common molecular feature of pendrin variants with affected function, the identification of strategies to prevent reduction in expression levels may represent a crucial step of potential future therapeutic interventions aimed at restoring the transport activity of dysfunctional pendrin variants.

Evaluation of Audiometric Thresholds and Speech Perception Sentence Test in Adults and Elderly After Cochlear Implantation.

AIM: To compare the audiometric thresholds and speech perception sentence test, between two groups with bilateral post-lingual, severe to profound sensorineural hearing loss. METHODS: Retrospective and analytical study, with 59 patients divided into 2 groups (under 60 years and above 60 years old) implanted between May/2002 and February/2007. RESULTS: The first group (control) included 30 patients with a mean age of 44 years. The audiometric threshold value in this group was 26 dB, and the average value of speech perception test was 94%. The second group included 29 patients with a mean age of 69 years. The average audiometric threshold was 29 dB, and the average value of SPT was 90%. The Mann-Whitney U-test was considered significant (P<0.05) only for 6-8 KHz frequencies and for SPT. CONCLUSION: Both groups had excellent outcomes in audiometric and speech testing with the use of CI, but with a significantly better performance in the adult group.

Molecular findings in Brazilian patients with osteogenesis imperfecta.

Osteogenesis imperfecta (OI) is a genetic disorder of increased bone fragility and low bone mass. Severity varies widely, ranging from intrauterine fractures and perinatal lethality to very mild forms without fractures. Most patients with a clinical diagnosis of OI have a mutation in the COL1A1 or COL1A2 genes that encode the a chains of type I procollagen, the major protein in bones. Hence, the aim of the present study was to identify mutations in the COL1A1 gene in 13 unrelated Brazilian OI patients. This is the first molecular study of OI in Brazil. We found 6 mutations, 4 of them novel (c.1885delG, p.P239A, p.G592S, p.G649D) and 2 previously described (p.R237X and p.G382S). Thus, the findings show that there are no prevalent mutations in our sample, and that their distribution is similar to that reported by other authors, with preponderance of substitutions for glycine in the triple helix domain, causing OI types II, III and IV.

[Prospects for genetic hearing loss screening: 35delG mutation tracking in a newborn population]. / Perspectivas para triagem da deficiência auditiva genética: rastreamento da mutação 35delG em neonatos.

OBJECTIVES: To investigate the prevalence of the 35delG mutation in a newborn population, with specific molecular testing, and to evaluate the prospects for genetic neonatal screening for hearing impairment. POPULATION AND METHOD: 233 newborn were evaluated at the Hospital de Base de São José do Rio Preto, SP, for molecular analysis of the 35delG mutation in the connexin 26 gene, with the reaction technique in allele-specific polymerase chain reaction, after genomic DNA extraction from umbilical cord blood. RESULTS: Five heterozygotes were identified, obtaining a prevalence of 2.24% of 35delG mutation carriers in the study population. CONCLUSION: Using the molecular test allowed for the identification of the 35delG mutation in the study population with the possibility of being used as a complement to neonatal audiometric screening as being simple, fast, and easily to perform with low costs.

Satisfaction of Children with Auditory Neuropathy and Cochlear Implant.

OBJECTIVE: In auditory neuropathy (AN) a dyssynchrony in the nerve conduction of the auditory nerve fibers is observed. Typically, patients with AN exhibit moderate to profound sensorineural hearing loss, and treatment using cochlear implants (CIs) or hearing aids should be performed as early as possible for a better hearing rehabilitation. The aim of this study is to evaluate the satisfaction level of patients with AN spectrum disorder treated using CIs. The Satisfaction with Amplification in Daily Life questionnaire was selected to evaluate 10 patients with AN treated using CIs. MATERIALS AND METHODS: Clinical study of patients with AN spectrum disorder submitted to CI. A retrospective data analysis, genetic and clinical evaluation in a tertiary referral center was done. RESULTS: The means of the subscales for positive effects, services and costs, negative factors, and personal image were 6.15, 4.6, 3.26, and 3.33, respectively. CONCLUSIONS: Patients with AN treated using CIs consider themselves satisfied.

Screening for mutations in the GJB3 gene in Brazilian patients with nonsyndromic deafness.

Deafness is a complex disorder that is affected by a high number of genes and environmental factors. Recently, enormous progress has been made in nonsyndromic deafness research, with the identification of 90 loci and 33 nuclear and 2 mitochondrial genes involved (http://dnalab-www.uia.ac.be/dnalab/hhh/). Mutations in the GJB3 gene, encoding the gap junction protein connexin 31 (Cx31), have been pathogenically linked to erythrokeratodermia variabilis and nonsyndromic autosomal recessive or dominant hereditary hearing impairment. To determine the contribution of the GJB3 gene to sporadic deafness, we analysed the GJB3 gene in 67 families with nonsyndromic hearing impairment. A single coding exon of the GJB3 gene was amplified from genomic DNA and then sequenced. Here we report on three amino acid changes: Y177D (c.529T > G), 49delK (c.1227C > T), and R32W (c.144-146delGAA). The latter substitution has been previously described, but its involvement in hearing impairment remains uncertain. We hypothesize that mutations in the GJB3 gene are an infrequent cause of nonsyndromic deafness.

Newborn hearing screening and genetic testing in 8974 Brazilian neonates.

OBJECTIVE: An early diagnosis has been a priority in the audiological practice. Identifying hearing loss until 3 months old through Universal Newborn Hearing Screening and intervention before 6 months old, minimize the impact of auditory loss in the health and communication development of these children. However, in the clinical practice, despite the help of the risk indicators in the audiological and etiological diagnosis, the integrated services have come up against the challenge of determining the causes of auditory loss, bearing in mind that approximately 50% of the subjects who have congenital loss do not show risk factors in their clinical history. The current research aims introduce together etiologic and audiological diagnosis of newborns. METHODS: We eluted dried blood spots from paper and performed genetic testing for 35delG mutation in 8974 newborns that were also screened for transient otoacoustic emissions (TOAE). In addition, the A1555G and A827G mutations in the MTRNR1 mitochondrial gene were screened in all newborns. RESULTS: We have found 17 individuals who failed in TOAE. Among them, we detected 4 homozygous newborns for 35delG mutation and 3 individuals with A827G mutation in the MTRNR1 mitochondrial gene. The frequency of 35delG carriers was 0.94% [84/8974]. In all 17 individuals who failed in OAE no other mutation besides those mentioned above was found. CONCLUSIONS: The results greatly contribute to the public health area indicating the etiologic diagnosis, allowing family counseling as well as the early rehabilitation treatment or surgical intervention. Over time that will help to reduce the costs of rehabilitation considerably.

Connexin 26 35delG does not represent a mutational hotspot.

Non-syndromic hearing impairment (NSHI) is the most common form of deafness and presents with no other symptoms or sensory defects. Mutations in the gap junction gene GJB2 account for a high proportion of recessive NSHI. The GJB2 gene encodes connexin 26, which forms plasma membrane channels between cochlear cells. In Caucasian populations a single mutation, 35delG, accounts for most cases of NSHI. This mutation appears to be most prevalent in individuals of Mediterranean European descent, with carrier frequencies estimated as being as high as one in thirty. The 35delG region may be a mutational hotspot. The mutation arises from the deletion of a guanine from a six-guanine stretch and nearby microsatellite markers show little evidence for linkage disequilibrium. We believe that 35delG is an old mutation in a chromosomal region of high recombination. The genetic context of the 35delG mutation was examined to distinguish between an old or a recurring mutation. We identified two single-nucleotide polymorphisms (SNPs) immediately upstream of the first exon of GJB2. Polymerase chain reaction/restriction fragment length polymorphism analysis determined the SNP genotype of 35delG containing chromosomes from various populations, including Italy, Brazil, and North America. We found the same, relatively rare, polymorphism associated with the 35delG mutation in all populations studied. We have also examined microsatellite markers D13S175, which is 80 kb telomeric to GJB2, and D13S1316, which is 80 kb centromeric to GJB2. D13S175 appears to be in weak linkage disequilibrium with 35delG, while D13S1316 is less so. SNPs located between the 35delG mutation and the microsatellite markers show strong evidence of linkage disequilibrium. Taken together, these results indicate there has been substantial recombination near the 35delG mutation; however, we present evidence that the 35delG mutation arose in European and Middle Eastern populations from a single mutational event on a founder chromosome.

Prevalence and evolutionary origins of the del(GJB6-D13S1830) mutation in the DFNB1 locus in hearing-impaired subjects: a multicenter study.

Mutations in GJB2, the gene encoding connexin-26 at the DFNB1 locus on 13q12, are found in as many as 50% of subjects with autosomal recessive, nonsyndromic prelingual hearing impairment. However, genetic diagnosis is complicated by the fact that 10%-50% of affected subjects with GJB2 mutations carry only one mutant allele. Recently, a deletion truncating the GJB6 gene (encoding connexin-30), near GJB2 on 13q12, was shown to be the accompanying mutation in approximately 50% of these deaf GJB2 heterozygotes in a cohort of Spanish patients, thus becoming second only to 35delG at GJB2 as the most frequent mutation causing prelingual hearing impairment in Spain. Here, we present data from a multicenter study in nine countries that shows that the deletion is present in most of the screened populations, with higher frequencies in France, Spain, and Israel, where the percentages of unexplained GJB2 heterozygotes fell to 16.0%-20.9% after screening for the del(GJB6-D13S1830) mutation. Our results also suggest that additional mutations remain to be identified, either in DFNB1 or in other unlinked genes involved in epistatic interactions with GJB2. Analysis of haplotypes associated with the deletion revealed a founder effect in Ashkenazi Jews and also suggested a common founder for countries in Western Europe. These results have important implications for the diagnosis and counseling of families with DFNB1 deafness.

Perspectivas para triagem da deficiência auditiva genética: rastreamento da mutação 35delG em neonatos / Prospects for genetic hearing loss screening: 35delG mutation tracking in a newborn population

OBJETIVO: Investigar a prevalência da mutação 35delG em amostra de recém-nascidos, com teste molecular específico; avaliar as perspectivas para a triagem neonatal genética para a deficiência auditiva. CASUíSTICA E MÉTODO: Foram avaliados 223 recém-nascidos no Hospital de Base de São José do Rio Preto, em São Paulo, para análise molecular da mutação 35delG, no gene da conexina 26, com a técnica da reação em cadeia da polimerase alelo-específico, após extração do DNA genômico de sangue de cordão umbilical. RESULTADOS: Foram identificados cinco heterozigotos, obtendo-se prevalência de 2,24 por cento de portadores da mutação 35delG, na população do estudo. CONCLUSAO: O uso do teste molecular permitiu a identificação da mutação 35delG na população do estudo, podendo ser utilizado como complemento aos rastreamentos audiométricos neonatais por ser simples, rápido, de fácil execução e de baixo custo.

Somatic and germ cell cytogenetic studies and AZF microdeletion screening in infertile men

Clinical and cytogenetic studies were performed in 65 infertile individuals, and 56 of them were also screened for microdeletions in Yq11 (AZF region). Relevant environmental etiological factors were identified in 10 cases (15.4 percent). Sertoli-cell-only syndrome was diagnosed in six patients (9,2 percent). Karyotype abnormalities were detected in six individuals, and five other patients presented desynapsis of bivalents in meiosis. Three out of the 56 patients studied were carriers of microdeletions in the AZF region, one of them also presenting a chromosomal mosaicism for an extra i(22p).