Deafness genetic mutation spectrum in nonsyndromic hearing impairment associated with enlarged vestibular aqueducts / 中国康复理论与实践

ObjectiveTo investigate the deafness genetic mutation spectrum in nonsyndromic hearing impairment (NSHI) associated with enlarged vestibular aqueducts (EVA). MethodsFrom October, 2015 to August, 2016, 85 patients with NSHI from Hubei Yichang Special Education School were examined with temporal bone CT, and 20 deafness-related gene mutations in GJB2, GJB3, SLC26A4 and mtDNA 12S rRNA were detected with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. ResultsA total of 31 patients were found EVA with temporal bone CT. Compared with non-EVA patients, the proportion of deafness-related gene mutations was more in patients with EVA (χ2 = 11.160, P = 0.001), especially for c.919-2A>G mutation of SLC26A4 (χ2 = 23.870, P < 0.001). ConclusionThe deafness gene mutation spectrum is different in NSHI patients with or without EVA. It is needed to optimize genetic testing scheme for deafness for early diagnosis and intervention of NSHI associated with EVA.

Analysis of Genetic Variations in Connexin 26 ( GJB2 ) Gene among Nonsyndromic Hearing Impairment: Familial Study.

Objective The goal of this research was to investigate the gap junction beta 2 ( GJB2 ) gene mutations associated with nonsyndromic hearing loss individuals in North Karnataka, India. Materials and Methods For this study, patients with sensorineural genetic hearing abnormalities and a family history of deafness were included. A total of 35 patients from 20 families have been included in the study. The patient's DNA was isolated from peripheral blood samples. The GJB2 gene coding region was analyzed through Sanger sequencing. Results There is no changes in the first exon of the GJB2 gene. Nine different variants were recorded in second exon of the targeted gene. W24X and W77X are two nonsense mutations and three polymorphisms viz. R127H, V153I, and I33T were reported along with four 3'-UTR variants. A total (9/20) of 45% of families have been identified with mutations in the targeted gene. Conclusion GJB2 mutations were identified in 19 deaf-mute patients (19/35), and 13 patients were homozygous for the mutations identified in our study cohort. In our study, W24X mutation was found to be the pathogenic with a high percentage, prompting further evaluation of the other genes, along with the study of additional genetic or external causes in the families, which is essential.

Autosomal Dominantly Inherited GREB1L Variants in Individuals with Profound Sensorineural Hearing Impairment.

Congenital hearing impairment is a sensory disorder that is genetically highly heterogeneous. By performing exome sequencing in two families with congenital nonsyndromic profound sensorineural hearing loss (SNHL), we identified autosomal dominantly inherited missense variants [p.(Asn283Ser); p.(Thr116Ile)] in GREB1L, a neural crest regulatory molecule. The p.(Thr116Ile) variant was also associated with bilateral cochlear aplasia and cochlear nerve aplasia upon temporal bone imaging, an ultra-rare phenotype previously seen in patients with de novo GREB1L variants. An important role of GREB1L in normal ear development has also been demonstrated by greb1l-/- zebrafish, which show an abnormal sensory epithelia innervation. Last, we performed a review of all disease-associated variation described in GREB1L, as it has also been implicated in renal, bladder and genital malformations. We show that the spectrum of features associated with GREB1L is broad, variable and with a high level of reduced penetrance, which is typically characteristic of neurocristopathies. So far, seven GREB1L variants (14%) have been associated with ear-related abnormalities. In conclusion, these results show that autosomal dominantly inherited variants in GREB1L cause profound SNHL. Furthermore, we provide an overview of the phenotypic spectrum associated with GREB1L variants and strengthen the evidence of the involvement of GREB1L in human hearing.

Intracellular Chloride Channels: Novel Biomarkers in Diseases.

Ion channels are integral membrane proteins present on the plasma membrane as well as intracellular membranes. In the human genome, there are more than 400 known genes encoding ion channel proteins. Ion channels are known to regulate several cellular, organellar, and physiological processes. Any mutation or disruption in their function can result in pathological disorders, both common or rare. Ion channels present on the plasma membrane are widely acknowledged for their role in various biological processes, but in recent years, several studies have pointed out the importance of ion channels located in intracellular organelles. However, ion channels located in intracellular organelles are not well-understood in the context of physiological conditions, such as the generation of cellular excitability and ionic homeostasis. Due to the lack of information regarding their molecular identity and technical limitations of studying them, intracellular organelle ion channels have thus far been overlooked as potential therapeutic targets. In this review, we focus on a novel class of intracellular organelle ion channels, Chloride Intracellular Ion Channels (CLICs), mainly documented for their role in cardiovascular, neurophysiology, and tumor biology. CLICs have a single transmembrane domain, and in cells, they exist in cytosolic as well as membranous forms. They are predominantly present in intracellular organelles and have recently been shown to be localized to cardiomyocyte mitochondria as well as exosomes. In fact, a member of this family, CLIC5, is the first mitochondrial chloride channel to be identified on the molecular level in the inner mitochondrial membrane, while another member, CLIC4, is located predominantly in the outer mitochondrial membrane. In this review, we discuss this unique class of intracellular chloride channels, their role in pathologies, such as cardiovascular, cancer, and neurodegenerative diseases, and the recent developments concerning their usage as theraputic targets.

A Genomic and Protein-Protein Interaction Analyses of Nonsyndromic Hearing Impairment in Cameroon Using Targeted Genomic Enrichment and Massively Parallel Sequencing.

Hearing impairment (HI) is one of the leading causes of disability in the world, impacting the social, economic, and psychological well-being of the affected individual. This is particularly true in sub-Saharan Africa, which carries one of the highest burdens of this condition. Despite this, there are limited data on the most prevalent genes or mutations that cause HI among sub-Saharan Africans. Next-generation technologies, such as targeted genomic enrichment and massively parallel sequencing, offer new promise in this context. This study reports, for the first time to the best of our knowledge, on the prevalence of novel mutations identified through a platform of 116 HI genes (OtoSCOPE®), among 82 African probands with HI. Only variants OTOF NM_194248.2:c.766-2A>G and MYO7A NM_000260.3:c.1996C>T, p.Arg666Stop were found in 3 (3.7%) and 5 (6.1%) patients, respectively. In addition and uniquely, the analysis of protein-protein interactions (PPI), through interrogation of gene subnetworks, using a custom script and two databases (Enrichr and PANTHER), and an algorithm in the igraph package of R, identified the enrichment of sensory perception and mechanical stimulus biological processes, and the most significant molecular functions of these variants pertained to binding or structural activity. Furthermore, 10 genes (MYO7A, MYO6, KCTD3, NUMA1, MYH9, KCNQ1, UBC, DIAPH1, PSMC2, and RDX) were identified as significant hubs within the subnetworks. Results reveal that the novel variants identified among familial cases of HI in Cameroon are not common, and PPI analysis has highlighted the role of 10 genes, potentially important in understanding HI genomics among Africans.

[Mutation analysis of GJB2 gene in 1 822 patients with nonsyndromic hearing loss in Zhejiang Province].

Objective:To analyze the genetic characteristics in nonsyndromic hearing impairment (NSHL) patients in Zhejiang province.Method:Peripheral blood samples were obtained from 1822 NSHL patients and 467 normal hearing controls in Zhejiang province. We carried out a systematic mutational screening of GJB2 gene in these subjects by amplifying the coding region of GJB2 gene and sequencing directly.Result:Thirty kinds of mutation were identified, including eleven pathogenic mutations, one hypomorphic allele, sixteen polymorphic mutations and two novel mutations. The c.235delC mutation was the most prevalent pathogenic mutation in this cohort (18.50%), and the rate of allele mutation was 12.16%. The frequency of c.299_300delAT,c.176_191del16,c.512_513insAACG,c.35delG,c.283G>A,c.427C>T,c.35insG,c.439G>A,c.571T>C,c.139G>T mutations were decreased in turn.Conclusion:c.235delC mutation is the hot spot of GJB2 gene mutation in NSHL patients in Zhejiang province and the most common mutational pattern is frame-shift mutation. The discovery of novel mutations enriches the spectrum and frequency of variants in GJB2 gene.

Genetic and clinical analysis of nonsyndromic hearing impairment in pediatric and adult cases.

Previous studies have linked GJB2 gene and mitochondrial DNA (mtDNA) mutations to nonsyndromic hearing impairment (NSHI), but no study in China has yet investigated these mutations across all age groups. To fill the gap, this study ascertained 263 patients with NSHI between ages 2 months and 60 years and analyzed the presence of GJB2 gene and mtDNA A1555G/C1494T mutations by polymerase chain reaction (PCR) and DNA sequencing. A total of 20 types of mutations were detected for the GJB2 gene. The GJB2 gene and mtDNA A1555G/C1494T mutations were detected in 18.63 and 11.41% cases, respectively. At the first hospital visit, GJB2 gene mutations were detected in 5.97% of adult patients (>18 years) and 22.96% pediatric patients (<18 years) (χ2 =9.506, p = 0.002), and mtDNA A1555G/C1494T mutations were detected in 31.34% of adult patients and 4.59% of pediatric patients (χ2 = 35.359, p <0.001). When patients were classified by age at onset of deafness, significantly more (20.68%) pediatric patients had GJB2 gene mutations than did adult patients (0.0%) (χ2 = 4.685; p = 0.006). Mitochondrial DNA A1555G/C1494T mutations were detected in 15.38% of adult-onset and 8.86% pediatric-onset patients, respectively. Interestingly, most GJB2 gene mutation carriers experienced NSHI onset within the first year of life (65.31%), while mtDNA A1555G/C1494T mutation carriers experienced onset at any age. Therefore, GJB2 gene mutations appear to contribute to congenital deafness, while mtDNAA1555G/C1494T mutations contribute mainly to acquired deafness in Chinese individuals. Both newborn hearing screening and genetic testing are important to diagnose and treat deafness.

Detection and risk analysis of hereditary deafness / 国际生物医学工程杂志

Hereditary hearing impairment is caused by genetic defects and is a common clinical disease. Since the lack of efficient treatment method, genetic counseling is more important in this field. It provides information about inherited disorders and focuses on assessment and interpretation of the risk for occurrence of genetic conditions in the family. Presented in this paper are classification of hereditary hearing impairment and methods to perform probability analysis using features of pathogenic genes and information of pedigree.

Study of mitochondrial DNA A1555G mutation among nonsyndromic hearing impairment in Chinese population / 中华检验医学杂志

Objective To study the prevalence of the mtDNA A1555G gene mutation in Chinese population with nonsyndromic hearing impairment.Methods PCR-RFLP,directional sequencing of PCR products were applied in 325 patients with nonsyndromic hearing impairment and 50 normal controls.Results The mutation rate of the mtDNA A1555G was 14.5% (47/325),28 of 47 cases were homozygosis,19 of 47 cases were heterozygosis.The same mutation was not detected in the control subjects.Conclusion The mutation rate of the mtDNA A1555G is relatively high in the Chinese NSHI patients,the mutation type includes both heterozygosis and homozygosis.