Autosomal Dominant Non-syndromic Hearing Impairment Research Articles

A novel variant in GAS2 is associated with autosomal dominant nonsyndromic hearing impairment in a Chinese family

Knockout of GAS2 (growth arrest-specific protein 2), causes disorganization and destabilization of microtubule bundles in supporting cells of the cochlear duct, leading to hearing loss in vivo. However, the molecular mechanism through which GAS2 variant results in hearing loss remains unknown. By Whole-exome sequencing, we identified a novel heterozygous splicing variant in GAS2 (c.616–2 A > G) as the only candidate mutation segregating with late-onset and progressive nonsyndromic hearing loss (NSHL) in a large dominant family. This splicing mutation causes an intron retention and produces a C-terminal truncated protein (named GAS2mu). Mechanistically, the degradation of GAS2mu via the ubiquitin-proteasome pathway is enhanced, and cells expressing GAS2mu exhibit disorganized microtubule bundles. Additionally, GAS2mu further promotes apoptosis by increasing the Bcl-xS/Bcl-xL ratio instead of through the p53-dependent pathway as wild-type GAS2 does, indicating that GAS2mu acts as a toxic molecule to exacerbate apoptosis. Our findings demonstrate that this novel variant of GAS2 promotes its own protein degradation, microtubule disorganization and cellular apoptosis, leading to hearing loss in carriers. This study expands the spectrum of GAS2 variants and elucidates the underlying pathogenic mechanisms, providing a foundation for future investigations of new therapeutic strategies to prevent GAS2-associated progressive hearing loss.

Genetic etiology of non-syndromic hearing loss in Europe.

Hearing impairment not etiologically associated with clinical signs in other organs (non-syndromic) is genetically heterogeneous, so that over 120 genes are currently known to be involved. The frequency of mutations in each gene and the most frequent mutations vary throughout populations. Here we review the genetic etiology of non-syndromic hearing impairment (NSHI) in Europe. Over the years, epidemiological data were scarce because of the large number of involved genes, whose screening was not cost-effective until implementation of massively parallel DNA sequencing. In Europe, the most common form of autosomal recessive NSHI is DFNB1, which accounts for 11-57% of the cases. Mutations in STRC account for 16% of the recessive cases, and only a few more (MYO15A, MYO7A, LOXHD1, USH2A, TMPRSS3, CDH23, TMC1, OTOF, OTOA, SLC26A4, ADGRV1 and TECTA) have contributions higher than 2%. As regards autosomal-dominant NSHI, DFNA22 (MYO6) and DFNA8/12 (TECTA) represent the most common forms, accounting for 21% and 18% of elucidated cases, respectively. The contribution of ACTG1 and WFS1 drops to 9% in both cases, followed by POU4F3 (6.5%), MYO7A (5%), MYH14 and COL11A2 (4% each). Four additional genes contribute 2.5% each one (MITF, KCNQ4, EYA4, SOX10) and the remaining are residually represented. X-linked hearing loss and maternally-inherited NSHI have minor contributions in most countries. Further knowledge on the genetic epidemiology of NSHI in Europe needs a standardization of the experimental approaches and a stratification of the results according to clinical features, familial history and patterns of inheritance, to facilitate comparison between studies.

A Monoallelic Variant in REST Is Associated with Non-Syndromic Autosomal Dominant Hearing Impairment in a South African Family.

Hearing impairment (HI) is a sensory disorder with a prevalence of 0.0055 live births in South Africa. DNA samples from a South African family presenting with progressive, autosomal dominant non-syndromic HI were subjected to whole-exome sequencing, and a novel monoallelic variant in REST [c.1244GC; p.(C415S)], was identified as the putative causative variant. The co-segregation of the variant was confirmed with Sanger Sequencing. The variant is absent from databases, 103 healthy South African controls, and 52 South African probands with isolated HI. In silico analysis indicates that the p.C415S variant in REST substitutes a conserved cysteine and results in changes to the surrounding secondary structure and the disulphide bonds, culminating in alteration of the tertiary structure of REST. Localization studies using ectopically expressed GFP-tagged Wild type (WT) and mutant REST in HEK-293 cells show that WT REST localizes exclusively to the nucleus; however, the mutant protein localizes throughout the cell. Additionally, mutant REST has an impaired ability to repress its known target AF1q. The data demonstrates that the identified mutation compromises the function of REST and support its implication in HI. This study is the second report, worldwide, to implicate REST in HI and suggests that it should be included in diagnostic HI panels.

Mutations in TOP2B cause autosomal-dominant hereditary hearing loss via inhibition of the PI3K-Akt signalling pathway.

Hereditary hearing impairment is a clinically and genetically heterogeneous disease. Whole-exome sequencing was performed on seven affected and six unaffected members in a large Chinese family with autosomal-dominant nonsyndromic hearing loss. The pathogenic variant of the gene encoding human topoisomerase IIβ TOP2B (c.G4837C:p.D1613H) was cosegregated with hearing loss in this pedigree and another two variants of TOP2B were detected in 66 sporadic patients with hearing loss. top2b knockdown led to significant defects in zebrafish inner ears and caused downregulation of akt which resulted in inactivation of PI3K-Akt signalling. As a result, supporting cell and hair cell numbers were reduced through inhibition of the PI3K-Akt pathway. Therefore, we hypothesized that mutations in TOP2B can cause autosomal-dominant nonsyndromic hearing impairment through inhibition of the PI3K-Akt signalling pathway. DATABASE: The whole-exome sequence data in the study are available at the Sequence Read Archive database (NCBI) under the accession numbers SRR9050868, SRR9050867, SRR90508676, SRR90508675, SRR90508674, SRR90508673, SRR90508672, SRR90508671, SRR90508679, SRR90508670, SRR9050859. SRR9050858 and SRR9050857, respectively.

Identification of a novel missense eya4 mutation causing autosomal dominant non"‘syndromic hearing loss in a chinese family

The aim of this study was to identify the novel missense eya4 mutation which cause autosomal dominant non syndromic hearing loss In a Chinese family. Hearing loss is the most common sensory deficit in humans, but the middle-frequency sensorineural hearing loss (MFSNHL) is rare among hereditary non-syndromic hearing loss, and EYA4 is one of the genes reported to be associated with MFSNHL. A genetic analysis of a Chinese family with autosomal dominant non‑syndromic progressive hearing impairment was conducted and assessed. Targeted exome sequencing, conducted using DNA samples of an affected member in this family, revealed a novel heterozygous missense mutation c.1855T>G in exon 20 of EYA4, causing amino-acid (aa) substitution Gly for Trp at a conserved position aa-619. The p.W619G mutation related to hearing loss in this Chinese family was validated by Sanger sequencing. Bioinformatic analysis confirmed the pathogenic effects of this mutation. We identified the novel missense mutation c.1855T>G (p.W619G) in EYA4 causing autosomal dominant non-syndromic hearing impairment in the selected Chinese family.

Design and Characterization of a Human Monoclonal Antibody that Modulates Mutant Connexin 26 Hemichannels Implicated in Deafness and Skin Disorders

Background: Mutations leading to changes in properties, regulation, or expression of connexin-made channels have been implicated in 28 distinct human hereditary diseases. Eight of these result from variants of connexin 26 (Cx26), a protein critically involved in cell-cell signaling in the inner ear and skin. Lack of non-toxic drugs with defined mechanisms of action poses a serious obstacle to therapeutic interventions for diseases caused by mutant connexins. In particular, molecules that specifically modulate connexin hemichannel function without affecting gap junction channels are considered of primary importance for the study of connexin hemichannel role in physiological as well as pathological conditions. Monoclonal antibodies developed in the last three decades have become the most important class of therapeutic biologicals. Recombinant methods permit rapid selection and improvement of monoclonal antibodies from libraries with large diversity.Methods: By screening a combinatorial library of human single-chain fragment variable (scFv) antibodies expressed in phage, we identified a candidate that binds an extracellular epitope of Cx26. We characterized antibody action using a variety of biochemical and biophysical assays in HeLa cells, organotypic cultures of mouse cochlea and human keratinocyte-derived cells.Results: We determined that the antibody is a remarkably efficient, non-toxic, and completely reversible inhibitor of hemichannels formed by connexin 26 and does not affect direct cell-cell communication via gap junction channels. Importantly, we also demonstrate that the antibody efficiently inhibits hyperative mutant Cx26 hemichannels implicated in autosomal dominant non-syndromic hearing impairment accompanied by keratitis and hystrix-like ichthyosis-deafness (KID/HID) syndrome. We solved the crystal structure of the antibody, identified residues that are critical for binding and used molecular dynamics to uncover its mechanism of action.Conclusions: Although further studies will be necessary to validate the effect of the antibody in vivo, the methodology described here can be extended to select antibodies against hemichannels composed by other connexin isoforms and, consequently, to target other pathologies associated with hyperactive hemichannels. Our study highlights the potential of this approach and identifies connexins as therapeutic targets addressable by screening phage display libraries expressing human randomized antibodies.

Phenotypic Heterogeneity in a DFNA20/26 family segregating a novel ACTG1 mutation.

BackgroundGenetic factors play an important role in hearing loss, contributing to approximately 60 % of cases of congenital hearing loss. Autosomal dominant deafness accounts for approximately 20 % of cases of hereditary hearing loss. Diseases with autosomal dominant inheritance often show pleiotropy, different degrees of penetrance, and variable expressivity.MethodsA three-generation Chinese family with autosomal dominant nonsyndromic hearing impairment (ADNSHI) was enrolled in this study. Audiometric data and blood samples were collected from the family. In total, 129 known human deafness genes were sequenced using next-generation sequencing (NGS) to identify the responsible gene mutation in the family. Whole Exome Sequencing (WES) was performed to exclude any other variant that cosegregated with the phenotype.ResultsThe age of onset of the affected family members was the second decade of life. The condition began with high-frequency hearing impairment in all family members excluding III:2. The novel ACTG1 c.638A > G (p.K213R) mutation was found in all affected family members and was not found in the unaffected family members. A heterozygous c.638A > G mutation in ACTG1 and homozygous c.109G > A (p.V37I) mutation in GJB2 were found in III:2, who was born with hearing loss. The WES result concurred with that of targeted sequencing of known deafness genes.ConclusionsThe novel mutation p.K213R in ACTG1 was found to be co-segregated with hearing loss and the genetic cause of ADNSHI in this family. A homozygous mutation associated with recessive inheritance only rarely co-acts with a dominant mutation to result in hearing loss in a dominant family. In such cases, the mutations in the two genes, as in ACTG1 and GJB2 in the present study, may result in a more severe phenotype. Targeted sequencing of known deafness genes is one of the best choices to identify the genetic cause in hereditary hearing loss families.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0333-1) contains supplementary material, which is available to authorized users.

P.1.i.015 Impulsive aggression in misophonia: results from a functional magnetic resonance imaging study

Linkage to an interval overlapping the DFNA10 locus on chromosome 6q22–23 was found through genome wide linkage analysis in a seven-generation Swedish family segregating postlingual, autosomal dominant nonsyndromic sensorineural hearing impairment. A novel heterozygous frame-shift mutation (c.579_580insTACC, p.(Asp194Tyrfs*52)) in EYA4 was identified that truncates the so-called variable region of the protein. The mutation is predicted to result in haploinsufficiency of the EYA4 product. No evidence for dilated cardiomyopathy was found in the family, contrasting to a previous family with a deletion resulting in a similar truncation in the variable region.A highly variable age of onset was seen in the mutation carriers. For assessment of the aetiology of this variability, clinical and audiometric data analyses were performed. The affected family members all had similar cross-sectional and longitudinal deterioration of pure tone average (PTA) once the process of hearing deterioration had started, and no gender, parent-of-origin or family branch differences on PTA could be found. Age at onset varied between the family branches. In summary, this is the ninth published genetically verified DFNA10 family. The results imply that unidentified factors, genetic or environmental, other than the EYA4 mutation, are of importance for the age at onset of DFNA10, and that mutation early in the variable region of the EYA4 protein can occur in the absence of dilated cardiomyopathy.

A novel mutation of EYA4 in a large Chinese family with autosomal dominant middle-frequency sensorineural hearing loss by targeted exome sequencing.

The middle-frequency sensorineural hearing loss (MFSNHL) is rare among hereditary non-syndromic hearing loss. To date, only three genes are reported to be associated with MFSNHL, including TECTA, EYA4 and COL11A2. In this report, we analyzed and explored the clinical audiological characteristics and the causative gene of a Chinese family named HG-Z087 with non-syndromic autosomal dominant inherited MFSNHL. Clinical audiological characteristics and inheritance pattern of a family were evaluated, and pedigree was drawn based on medical history investigation. Our results showed that the Chinese family was characterized by late onset, progressive, non-sydromic autosomal dominant MFSNHL. Targeted exome sequencing, conducted using DNA samples of an affected member in this family, revealed a novel heterozygous missense mutation c.1643C>G in exon 18 of EYA4, causing amino-acid (aa) substitution Arg for Thr at a conserved position aa-548. The p.T548R mutation related to hearing loss in the selected Chinese family was validated by Sanger sequencing. However, the mutation was absent in control group containing 100 DNA samples from normal Chinese families. In conclusion, we identified the pathogenic gene and found that the novel missense mutation c.1643C>G (p.T548R) in EYA4 might have caused autosomal dominant non-syndromic hearing impairment in the selected Chinese family.

Phenotypic variability in a seven-generation Swedish family segregating autosomal dominant hearing impairment due to a novel EYA4 frameshift mutation

Linkage to an interval overlapping the DFNA10 locus on chromosome 6q22–23 was found through genome wide linkage analysis in a seven-generation Swedish family segregating postlingual, autosomal dominant nonsyndromic sensorineural hearing impairment. A novel heterozygous frame-shift mutation (c.579_580insTACC, p.(Asp194Tyrfs*52)) in EYA4 was identified that truncates the so-called variable region of the protein. The mutation is predicted to result in haploinsufficiency of the EYA4 product. No evidence for dilated cardiomyopathy was found in the family, contrasting to a previous family with a deletion resulting in a similar truncation in the variable region.A highly variable age of onset was seen in the mutation carriers. For assessment of the aetiology of this variability, clinical and audiometric data analyses were performed. The affected family members all had similar cross-sectional and longitudinal deterioration of pure tone average (PTA) once the process of hearing deterioration had started, and no gender, parent-of-origin or family branch differences on PTA could be found. Age at onset varied between the family branches. In summary, this is the ninth published genetically verified DFNA10 family. The results imply that unidentified factors, genetic or environmental, other than the EYA4 mutation, are of importance for the age at onset of DFNA10, and that mutation early in the variable region of the EYA4 protein can occur in the absence of dilated cardiomyopathy.

A Novel MYO6 Splice Site Mutation Causes Autosomal Dominant Sensorineural Hearing Loss Type DFNA22 with a Favourable Outcome after Cochlear Implantation

Mutations in MYO6 encoding an atypical myosin motor protein important for inner ear hair cell function have been associated with autosomal recessive (DFNB37) and autosomal dominant (DFNA22) types of hearing loss in a few families worldwide. After genome-wide linkage analysis, we identified a novel MYO6 mutation at the splice acceptor site of exon 7 (c.554-1G>A) in an extended German family with autosomal dominant postlingual non-syndromic hearing impairment. Analysis of blood-derived cDNA revealed different aberrantly spliced mRNAs caused by the mutation, which are predicted to severely interfere with protein function. Two of the family members underwent cochlear implantation at ages 53 and 65. Here, we present detailed clinical data of this family which suggest a favourable outcome of cochlear implantation in hearing-impaired individuals with a MYO6 mutation.

Clinical aspects of an autosomal dominantly inherited hearing impairment linked to the DFNA60 locus on chromosome 2q23.1–2q23.3

A total of 64 loci for autosomal dominant non-syndromic hearing impairment have been described, and the causative genes have been identified for 24 of these. The present study reports on the clinical characteristics of an autosomal dominantly inherited hearing impairment that is linked to a region within the DFNA60 locus located on chromosome 2 in q22.1–24.1.A pedigree spanning four generations was established with 13 affected individuals. Linkage analysis demonstrated that the locus extended over a 2.96 Mb region flanked by markers D2S2335 and D2S2275. The audiograms mainly showed a distinctive U-shaped configuration. Deterioration of hearing started at a wide age range, from 12 to 40 years. Cross-sectional analysis showed rapid progression of hearing impairment from mild to severe, between the ages of 40 and 60 years, a phenomenon that is also observed in DFNA9 patients. The results of the individual longitudinal analyses were generally in line with those obtained by the cross-sectional analysis. Speech recognition scores related to the level of hearing impairment (PTA1,2,4 kHz) appeared to be fairly similar to those of presbyacusis patients. It is speculated that hearing impairment starting in mid-life, as shown by DFNA60 patients, could play a role in the development of presbyacusis. Furthermore, speech recognition did not deteriorate appreciably before the sixth decade of life. We conclude that DFNA60 should be considered in hearing impaired patients who undergo a rapid progression in middle age and are negative for DFNA9. Furthermore, cochlear implantation resulted in good rehabilitation in two DFNA60 patients.

C.359T>C mutation of the MYH14 gene in two autosomal dominant non-syndromic hearing impairment families with common ancestor

To identify the gene mutation for two Chinese families with autosomal dominant non-syndromic hearing impairment(NSHI). Two NSHI pedigrees with common ancestor were identified by clinical examination and family investigation. Linkage analysis was performed for all known NSHI loci, and all exons and exon-intron boundaries of the non-muscle myosin heavy chain 14 (MYH14) gene were amplified by PCR and sequenced. The disease-causing gene of these 2 pedigrees was fine mapped to the DFNA4 locus on 19q13.33. A heterozygous transition of c. 359T>C (p.S120L) in MYH14 gene was identified. The mutation was detected in all patients but not in normal members in the two families. It is the first report that mutation in MYH14 gene can cause dominant non-syndromic hearing impairment in Asian population, suggesting that MYH14 gene can be a disease-causing gene of Chinese patients with hearing impairment.

Vestibular Impairment in a Dutch DFNA15 Family with an L289F Mutation in POU4F3

Vestibular examination (electronystagmography with rotatory chair and caloric tests) was performed on 18 carriers and 1 phenocopy carrier in a Dutch family with autosomal dominant nonsyndromic DFNA15. This is the second DFNA15 family worldwide to have a novel L289F mutation in POU4F3. Vestibular involvement appeared to be present in 2 affected individuals according to their medical history. Vestibular examination results in an extended subset of L289F POU4F3 mutation carriers varied from normal to areflexia. DFNA15 is the third cochleovestibular disorder, after DFNA9 and DFNA11, in the autosomal dominant nonsyndromic hearing impairment.

Amino acid 572 in TMC1: hot spot or critical functional residue for dominant mutations causing hearing impairment

Two different missense mutations, p.D572N and p.D572H, affecting the same nucleotide and codon of the TMC1 gene were earlier reported to cause autosomal dominant hearing impairment at locus DFNA36 in two North American families. No other dominant mutations of human TMC1 have been published. We ascertained a third North American family segregating autosomal dominant nonsyndromic hearing impairment at the DFNA36 locus. We identified the p.D572N mutation of TMC1 co-segregating with hearing loss in our study family. A comparative haplotype analysis of linked single nucleotide polymorphisms and short tandem repeats in the two families segregating p.D572N was not consistent with a founder effect. These findings can be explained in two ways. Either nucleotide 1714 is a hot spot for mutations or, alternatively, missense mutations at this site confer a specific pathogenic gain-of-function or dominant-negative effect.

Novel ACTG1 mutation causing autosomal dominant non-syndromic hearing impairment in a Chinese family

The gamma-actin (ACTG1) gene is a cytoplasmic nonmuscle actin gene, which encodes a major cytoskeletal protein in the sensory hair cells of the cochlea. Mutations in ACTG1 were found to cause autosomal dominant, progressive, sensorineural hearing loss linked to the DFNA 20/26 locus on chromosome 17q25.3 in European and American families, respectively. In this study, a novel missense mutation (c.364A>G; p.I122V) co-segregated with the affected individuals in the family and did not exist in the unaffected family members and 150 unrelated normal controls. The alteration of residue Ile122 was predicted to damage its interaction with actin-binding proteins, which may cause disruption of hair cell organization and function. These findings strongly suggested that the I122V mutation in ACTG1 caused autosomal dominant non-syndromic hearing impairment in a Chinese family and expanded the spectrum of ACTG1 mutations causing hearing loss.

Missense mutations inPOU4F3cause autosomal dominant hearing impairment DFNA15 and affect subcellular localization and DNA binding

In a Dutch pedigree suffering from autosomal dominant nonsyndromic hearing impairment (ADNSHI), linkage was found to the locus for DFNA15, with a two-point logarithm of the odds (LOD) score of 5.1. Sequence analysis of the POU4F3 gene that is involved in DFNA15 revealed the presence of a missense mutation (c.865C>T), segregating with the deafness in this family. The mutation is predicted to result in the substitution of a phenylalanine residue for a leucine residue (p.L289F) in the POU homeodomain of the transcription factor POU4F3. Mutation analysis of the POU4F3 gene in 30 patients suffering from dominantly inherited hearing impairment revealed a second novel missense mutation (c.668T>C), resulting in the substitution of a proline for a leucine residue (p.L223P) within the POU-specific DNA-binding domain of the protein. In a computer model describing the structure of the two DNA-binding domains, the alterations are predicted to affect the tertiary structure of these domains. Transient transfection studies showed that whereas the wild-type POU4F3 is located almost exclusively in the nucleus, part of the mutant proteins was also present in the cytoplasm. In addition, both mutant proteins showed greatly reduced capability for binding to DNA as well as transcriptionally activating reporter gene expression. Together, our results describe the identification of the first missense mutations in POU4F3 causing DFNA15. Furthermore, mutations in this gene do not seem to be a rare cause of hearing impairment in the Dutch population, and the POU4F3 gene may thus be suitable for implementation in diagnostic testing.

Phenotypic Characterization of DFNA24: Prelingual Progressive Sensorineural Hearing Impairment

This article describes the hearing impairment (HI) phenotype which segregates in a large multi-generation Swiss-German family with autosomal dominant nonsyndromic HI. The locus segregating within this pedigree is located on chromosome 4q35-qter and is designated as DFNA24. For this pedigree, audiometric data on 25 hearing-impaired family members are available. It was demonstrated that within this kindred the HI is sensorineural, bilateral, prelingual in onset, and progressive throughout life. Age-related typical audiograms depict steeply down-sloping curves, with moderate high-frequency HI at birth, then steady progression to moderate HI in the low frequencies, severe HI at mid-frequencies and profound HI at high frequencies by age 70. Annual threshold deterioration was ∼0.5 dB/year at 1–2 kHz after correction for presbycusis.

Phenotype Determination Guides Swift Genotyping of a DFNA2/KCNQ4 Family With a Hot Spot Mutation (W276S)

Genotype a family trait with autosomal dominant nonsyndromic sensorineural hearing impairment guided only by the phenotype. Family study. Tertiary referral center. Fifteen family members. In the first phase, sequence analysis was performed on DNA isolated from buccal swabs of the proband and her daughter, guided by the phenotype based on audiometric data that were already available. After detection of the W276S missense mutation in the KCNQ4 gene in both patients, this finding was confirmed in the other affected family members. All participants completed a questionnaire, were clinically examined, and underwent standard pure-tone audiometry. The results were analyzed to refine the phenotypic features of the family trait. All clinically affected participants were carriers of the W276S hotspot mutation in exon 5 of the KCNQ4 gene on chromosome 1p34. Refined phenotypic features confirmed previously described phenotypes of DFNA2 families. Phenotype determination can be cost saving and very effective in detecting the genotype of autosomal dominant nonsyndromic hearing impairment, especially when phenotype analyses can be performed on data that are already available or easily collected.

Refinement of the DFNA4 locus to a 1.44 Mb region in 19q13.33.

Many forms of autosomal dominant non-syndromic hearing impairment are known. While the underlying gene defects and causative mutations have been discovered for some forms, the gene responsible for DFNA4 has remained elusive to date. Examination of a German four-generation kindred led to the identification of a 1.44 Mb map segment in contig NT_011109 as being the most likely DFNA4 candidate region in 19q13.33. The recombination breakpoints in this family and the intervals of two previously reported DFNA4 families allowed us to delineate a minimum consensus region between the markers D19S879 and D19S246. In our family, a maximum two-point LOD score of 4.5 was obtained at theta = 0 for the marker D19S867. Within the refined DFNA4 interval the public databases list more than 50 genes, from which several appear to be promising DFNA4 candidates due to similarities with animal models and with other causative genes involved in hearing disability.