ACEMg Diet Supplement Modifies Progression of Hereditary Deafness.
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ABSTRACT:
SUBMITTER: Green KL
PROVIDER: S-EPMC4786814 | biostudies-other | 2016 Mar
REPOSITORIES: biostudies-other
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Project description:The authors describe a study in progress to identify Turkish families with hereditary hearing loss and isolate possible responsible disease genes. Due to extreme genetic heterogeneity and limited audiological differentiation of hereditary hearing loss, it is necessary to identify large or small families from genetic isolates to locate loci responsible for hearing loss on a chromosome. To accomplish this goal, the medical records of 3800 children were examined at the ENT Clinic of Ege University between 1975 and 1994. All were suspected of having various hearing impairments. Additionally, students from two schools for the hearing impaired in Izmir and Eskisehir, Turkey were examined. To date, 16 families with syndromal deafness and 55 families with non-syndromal hereditary hearing loss involving two or more affected individuals have been identified and categorized according to the mode of inheritance. The majority (66%) of the non-syndromal families showed an autosomal recessive pattern, 29% an autosomal dominant inheritance and 5% an X-linked mode of inheritance. In the study presented there has been a predominance of affected males versus females and the consanguinity rate was 22%.
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Project description:Animal models that recapitulate human disease are proving to be an invaluable tool in the identification of novel disease-associated genes. These models can improve our understanding of the complex genetic mechanisms involved in disease and provide a basis to guide therapeutic strategies to combat these conditions. We have identified a novel mouse model of non-syndromic sensorineural hearing loss with linkage to a region on chromosome 18. Eeyore mutant mice have early onset progressive hearing impairment and show abnormal structure of the sensory epithelium from as early as 4 weeks of age. Ultrastructural and histological analyses show irregular hair cell structure and degeneration of the sensory hair bundles in the cochlea. The identification of new genes involved in hearing is central to understanding the complex genetic pathways involved in the hearing process and the loci at which these pathways are interrupted in people with a genetic hearing loss. We therefore discuss possible candidate genes within the linkage region identified in eeyore that may underlie the deafness phenotype in these mice. Eeyore provides a new model of hereditary sensorineural deafness and will be an important tool in the search for novel deafness genes.
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Project description:Background: Preconception or prenatal carrier screening plays an important role in reproductive decision-making, but current research on hereditary deafness is limited. This study aimed to investigate the carrier frequencies of common deafness genes in the Chinese population who underwent carrier screening and to follow up on pregnancy outcomes in high-chance couples. Methods: Individual females or couples in preconception or early pregnancy were recruited from two hospitals in China. Carrier screening for common deafness genes in the Chinese population, including the GJB2 and SLC26A4 genes, was performed using next-generation sequencing technology. Genetic counseling was provided to subjects before and after testing. Results: Of the 9,993 subjects screened, the carrier rate was 2.86% for the GJB2 gene and 2.63% for the SLC26A4 gene. The variant with the highest carrier frequency in GJB2 was c.235delC (1.89%), and c.919-2A>G (1.08%) in SLC26A4. Of the six high-chance couples, four made alternative reproductive decisions (three with prenatal diagnosis and one with preimplantation genetic testing), with consequent termination of the birth of two affected fetuses. Conclusion: These findings confirmed the clinical utility of preconception or prenatal carrier screening for hereditary deafness.
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Project description:Hearing loss (HL) is one of the most common sensory impairments worldwide and represents a critical medical and public health issue. Since the mid-1900s, great efforts have been aimed at understanding the etiology of both syndromic and non-syndromic HL and identifying correlations with specific audiological phenotypes. The extraordinary discoveries in the field of molecular genetics during the last three decades have contributed substantially to the current knowledge. Next-generation sequencing technologies have dramatically increased the diagnostic rate for genetic HL, enabling the detection of novel variants in known deafness-related genes and the discovery of new genes implicated in hearing disease. Overall, genetic factors account for at least 40% of the cases with HL, but a portion of affected patients still lack a definite molecular diagnosis. Important steps forward have been made, but many aspects still have to be clarified. In particular, the role of epigenetics in the development, function and pathology of hearing is a research field that still needs to be explored. This research is extremely challenging due to the time- and tissue-dependent variability of the epigenetic changes. Multisystem diseases are expected to be investigated at first: specific epi-signatures have been identified for several syndromic disorders and represent potential markers for molecular diagnostics.
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Project description:Whole exome sequencing provides unprecedented opportunities to identify causative DNA variants in rare Mendelian disorders. Finding the responsible mutation via traditional methods in families with hearing loss is difficult due to a high degree of genetic heterogeneity. In this study we combined autozygosity mapping and whole exome sequencing in a family with 3 affected children having nonsyndromic hearing loss born to consanguineous parents. Two novel missense homozygous variants, c.508C>A (p.H170N) in GIPC3 and c.1328C>T (p.T443M) in ZNF57, were identified in the same ?6 Mb autozygous region on chromosome 19 in affected members of the family. Both variants co-segregated with the phenotype and were absent in 335 ethnicity-matched controls. Biallelic GIPC3 mutations have recently been reported to cause autosomal recessive nonsyndromic sensorineural hearing loss. Thus we conclude that the hearing loss in the family described in this report is caused by a novel missense mutation in GIPC3. Identified variant in GIPC3 had a low read depth, which was initially filtered out during the analysis leaving ZNF57 as the only potential causative gene. This study highlights some of the challenges in the analyses of whole exome data in the bid to establish the true causative variant in Mendelian disease.
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Project description:Harboyan syndrome is a degenerative corneal disorder defined as congenital hereditary endothelial dystrophy (CHED) accompanied by progressive, postlingual sensorineural hearing loss. To date, 24 cases from 11 families of various origin (Asian Indian, South American Indian, Sephardi Jewish, Brazilian Portuguese, Dutch, Gypsy, Moroccan, Dominican) have been reported. More than 50% of the reported cases have been associated with parental consanguinity. The ocular manifestations in Harboyan syndrome include diffuse bilateral corneal edema occurring with severe corneal clouding, blurred vision, visual loss and nystagmus. They are apparent at birth or within the neonatal period and are indistinguishable from those characteristic of the autosomal recessive CHED (CHED2). Hearing deficit in Harboyan is slowly progressive and typically found in patients 10-25 years old. There are no reported cases with prelinglual deafness, however, a significant hearing loss in children as young as 4 years old has been detected by audiometry, suggesting that hearing may be affected earlier, even at birth. Harboyan syndrome is caused by mutations in the SLC4A11 gene located at the CHED2 locus on chromosome 20p13-p12, indicating that CHED2 and Harboyan syndrome are allelic disorders. A total of 62 different SLC4A11 mutations have been reported in 98 families (92 CHED2 and 6 Harboyan). All reported cases have been consistent with autosomal recessive transmission. Diagnosis is based on clinical criteria, detailed ophthalmological assessment and audiometry. A molecular confirmation of the clinical diagnosis is feasible. A variety of genetic, metabolic, developmental and acquired diseases presenting with clouding of the cornea should be considered in the differential diagnosis (Peters anomaly, sclerocornea, limbal dermoids, congenital glaucoma). Audiometry must be performed to differentiate Harboyan syndrome from CHED2. Autosomal recessive types of CHED (CHED2 and Harboyan syndrome) should carefully be distinguished from the less severe autosomal dominant type CHED1. The ocular abnormalities in patients with Harboyan syndrome may be treated with topical hyperosmolar solutions. However, corneal transplantation (penetrating keratoplasty) represents definitive treatment. Corneal transplantation produces a substantial visual gain and has a relatively good surgical prognosis. Audiometric monitoring should be offered to all patients with CHED2. Hearing aids may be necessary in adolescence.
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Project description:Mutations in GJB2 (Gap junction protein beta 2) are the most common genetic cause of non-syndromic hereditary deafness in humans, especially the 35delG and 235delC mutations. Owing to the homozygous-lethal of Gjb2 mutation in mice, there are currently no perfect mouse models carrying Gjb2 mutation to mimic human hereditary deafness and unveil the pathogenesis. Here, we first constructed heterozygous mutant mice, Gjb2+/35delG and Gjb2+/235delC, through androgenic haploid embryonic stem cells (AG-haESCs) mediated semi-cloning technology, which showed normal hearing function at P28. Furthermore, a homozygous mutant mouse model, Gjb235delG/35delG, was generated via enhanced tetraploid embryo complementation, which exhibited profound hearing loss like human patients at P14. Mechanism analysis showed that Gjb2 35delG disrupts the formation of intercellular gap junction channel and tunnel of Corti, and hair cell mechanotransduction, rather than the development of hair cells. Collectively, our study provides ideal mouse models for understanding the pathogenic mechanism and opens up a new avenue for investigating the treatment for DFNB1A-related hereditary deafness.
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