Deafness Gene Mutations Research Articles

Novel compound heterozygous variants in MARVELD2 causing autosomal recessive hearing loss in two Chinese families.

Hereditary hearing loss is an important component of congenital hearing loss. MARVELD2 (OMIM ID:610572), located in the DFNB49 locus, which encodes a tight junction protein tricellulin playing an important role in the sensory epithelial barrier of the inner ear, may contribute to nonsyndromic autosomal recessive hereditary hearing loss. Two Han Chinese pedigrees with hearing loss underwent clinical and genetic analyses. Variants were detected by targeted next-generation sequencing and sequencing data were compared with the Human Genome Reference (GRCh 37/hg 19) to identify mutant genes and loci. Furthermore, online tools such as RDDC, SpliceAI, and REVEL were used to predict risks from different variants. Both two probands failed neonatal hearing screening and were diagnosed with sensorineural hearing loss. A total of 3 mutations were detected in the two families, c.1331+1G>A, c.1325A>G, and c.782G>A. According to ACMG/AMP guidelines, they were judged to be pathogenic, uncertain significance, and uncertain significance, respectively. These findings contribute to a better understanding of the relationship between different variants of MARVELD2 and hearing. This could further expand the spectrum of deafness gene mutations and contribute to deafness patient management and genetic counseling.

Heterozygous variants in transmembrane channel-like 1 gene cause autosomal recessive nonsyndromic hearing loss.

Autosomal recessive non-syndromic hearing loss (ARNSHL) can cause severe or very severe pre-speech hearing loss. Transmembrane channel-like 1 (TMC1) gene is the sixth deafness gene discovered, but the precise extent of its protein structure and function is unknown. First, history collection, audiology examination and imaging examination were performed on the proband and his family members. Peripheral blood of proband and family members was collected, genomic DNA was extracted, exon high-throughput sequencing technology was used to detect the deafness gene mutation of the proband, and Sanger sequencing was performed to verify the TMC1 gene of the proband's parents. The proband was born with hearing impairment, normal tympanic function, inability to induce acoustic reflex in both ears (acoustic reflex threshold is 100 dBHL), and severe sensorineural deafness. One of his sisters has severe sensorineural hearing loss, and neither his parents nor his other sister is hearing impaired. High-throughput sequencing of the proband identified mutations at c.741+3_741+6delAAGT (splicing) and c.884C>T (p.A295V) of the TMC1 gene, two of which were heterozygous mutations. Sanger sequencing confirmed that the c.884C > T mutation was inherited from the mother, while the c.741+3_741+6delAAGT mutation was derived from the father. Prediction of amino acid function suggested that both mutations were pathogenic mutations. In conclusion, we found a new pathogenic complex heterozygous mutation of the TMC1 gene, which enriched the mutation spectrum of the TMC1 gene and provided a basis for genetic counseling and prenatal diagnosis of ARNSHL.

A novel method for detecting nine hotspot mutations of deafness genes in one tube

Deafness is a common sensory disorder. In China, approximately 70% of hereditary deafness originates from four common deafness-causing genes: GJB2, SLC26A4, GJB3, and MT-RNR1. A single-tube rapid detection method based on 2D-PCR technology was established for nine mutation sites in the aforementioned genes, and Sanger sequencing was used to verify its reliability and accuracy. The frequency of hotspot mutations in deafness genes was analysed in 116 deaf students. 2D-PCR identified 27 genotypes of nine loci according to the melting curve of the FAM, HEX, and Alexa568 fluorescence channels. Of the 116 deaf patients, 12.9% (15/116) carried SLC26A4 mutations, including c.919-2A > G and c.2168A > G (allele frequencies, 7.3% and 2.2%, respectively). The positivity rate (29.3%; 34/116) was highest for GJB2 (allele frequency, 15.9% for c.235delC, 6.0% for c.299_300delAT, and 2.6% for c.176-191del16). Sanger sequencing confirmed the consistency of results between the detection methods based on 2D-PCR and DNA sequencing. Common pathogenic mutations in patients with non-syndromic deafness in Changzhou were concentrated in GJB2 (c.235delC, c.299_300delAT, and c.176-191del16) and SLC26A4 (c.919-2A > G and c.2168 A > G). 2D-PCR is an effective method for accurately and rapidly identifying deafness-related genotypes using a single-tube reaction, and is superior to DNA sequencing, which has a high cost and long cycle.

Mutation analysis of GJB2, SLC26A4, GJB3 and mtDNA12SrRNA genes in 251 non-syndromic hearing loss patients in Fujian, China

ObjectivesThe molecular etiology of non-syndromic hearing loss (NSHL) in Southeastern China (Fujian) has not been precisely identified. our study selected patients with NSHL and analyzed their causative genes, which helped to improve the accuracy of the diagnosis of hereditary hearing loss (HHL) and its treatment. Methods251 unrelated patients who attended the otolaryngology clinic of Fujian Maternal and Child Health Hospital with hearing loss were enrolled to our study. All patients had genetic tests and listening tests, of which 251 were diagnosed with NSHL. In addition, we used whole-exome sequencing (WES) in a patient who has a significant family history of HHL but negative for gene chip testing, as well as in his family members. ResultAmong of 251 patients, Nucleotide changes were found in 63 cases (25.09%), including 34 located in GJB2(13.5%, including 235delC and 299_300delAT), 13 located in SLC26A4(5.18%, including c.919-2G > A and 2168 A > G), 1 located in GJB3(0.4%,538C > T) and 16 located in mtDNA12SrRNA (6.37%,1555 A > G). In addition, we discuss the process of identifying novel PLS1 mutations from 251 patients. ConclusionOur results demonstrate the conventional deafness gene mutation in 251 NSHL patients in Fujian, China. Compared with the other area of China, we have a lower detection rate, but GJB2 235delC remains the most common mutation in Fujian. In addition, we discuss the process of discovering novel mutation locus for deafness, which provides an understanding for deafness diagnosis and genetic testing.

Report of rare and novel mutations in candidate genes in a cohort of hearing-impaired patients.

BackgroundMany hearing‐impaired patients carry mutations in rare or novel genes undetected in regular genetic hot regions/genes screening.MethodsWe collected clinical and genetic data from subjects with hearing loss who visited our department for genetic counseling. Next‐generation sequencing was conducted after 154 deafness‐related genes were captured using a designed genes panels in 14 unrelated families (37 participants). The results were filtered and assessed with in silico tools, in combination with pedigree mapping.ResultsTen mutations in regular deafness genes (GJB2, SLC26A4) and uncommon genes (OTOF, MYO7A, MYO15A, and KARS) were detected, which constituted 57.2% of yielded rate. In particular, two patients with nonsyndromic deafness carried biallelic KARS mutations. In addition, we identified an unreported digenic mutational inheritance in GRP98/USH2A genes in a proband with isolated hearing loss. Functional analyses and molecular modeling suggested the damaging consequence of these variants on encoded proteins. According to the variant pathogenicity guidelines, the 17 identified variants in total were classified as “pathogenic” or “likely pathogenic.”ConclusionThe candidate mutations in deafness genes were suggested to be co‐segregated in at least 57.2% of the studied pedigrees. This is the new report of rare/novel mutations causing inherited hearing loss in Chinese.

Concurrent Hearing and Genetic Screening among Newborns in Ningbo, China.

Objective To detect the carrier rates of deafness gene variants in populations in Ningbo and analyze the risk of hereditary hearing loss through concurrent hearing and genetic screening tests. Methods Two thousand one hundred and seventy-four newborns were enrolled from November 2018 to August 2019. All subjects underwent hearing screening and newborn deafness genetic screening with 15 variants in 4 genes, and the positive sites were simultaneously verified by sequencing. Results The total carrier rate of genetic variants in Ningbo reached 4.32%, when GJB2 c.235delC was the variant with the highest prevalence (2.12%), approximately accounting for 48.9% of the total carrier frequency. The carrier frequency of SLC26A4 c.919-2A>G was 0.87%, while the most common variant in mitochondrial DNA (mtDNA) MT-RNR1 gene was m.1555A>G, and its carrier frequency was 0.184%. In the OAE testing, 92 newborns passing hearing screening were tested positively for variants in 4 genes, and 2 of 42 newborns who failed in the first hearing test were found to mutate in 4 genes. Conclusion Herein, the results concerning the carrier rates for deafness gene mutations of Ningbo population are reported. Our study is beneficial to the insight into the deafness genomic epidemiology for deafness genes in Ningbo population and provides the reference for healthcare in Ningbo.

Multi-Center in-Depth Screening of Neonatal Deafness Genes: Zhejiang, China.

PurposeThe conventional genetic screening for deafness involves 9–20 variants from four genes. This study expands screening to analyze the mutation types and frequency of hereditary deafness genes in Zhejiang, China, and explore the significance of in-depth deafness genetic screening in newborns.MethodsThis was a multi-centre study conducted in 5,120 newborns from 12 major hospitals in the East-West (including mountains and islands) of Zhejiang Province. Concurrent hearing and genetic screening was performed. For genetic testing, 159 variants of 22 genes were screened, including CDH23, COL11A1, DFNA5, DFNB59, DSPP, GJB2, GJB3, KCNJ10, MT-RNR1, MT-TL1, MT-TS1, MYO15A, MYO7A, OTOF, PCDH15, SLC26A4, SOX10, TCOF1, TMC1, USH1G, WFS1, and WHRN using next-generation sequencing. Newborns who failed to have genetic mutations or hearing screening were diagnosed audiologically at the age of 6 months.ResultsA total of 4,893 newborns (95.57%) have passed the initial hearing screening, and 7 (0.14%) have failed in repeated screening. Of these, 446 (8.71%) newborns carried at least one genetic deafness-associated variant. High-risk pathogenic variants were found in 11 newborns (0.21%) (nine homozygotes and two compound heterozygotes), and eight of these infants have passed the hearing screening. The frequency of mutations in GJB2, GJB3, SLC26A4, 12SrRNA, and TMC1 was 5.43%, 0.59%, 1.91%, 0.98%, and 0.02%, respectively. The positive rate of in-depth screening was significantly increased when compared with 20 variants in four genes of traditional testing, wherein GJB2 was increased by 97.2%, SLC26A4 by 21% and MT-RNR1 by 150%. The most common mutation variants were GJB2c.235delC and SLC26A4c.919-2A > G, followed by GJB2c.299_300delAT. Homoplasmic mutation in MT-RNR1 was the most common, including m.1555A > G, m.961T > C, m.1095T > C. All these infants have passed routine hearing screening. The positive rate of MT-RNR1 mutation was significantly higher in newborns with high-risk factors of maternal pregnancy.ConclusionThe positive rate of deafness gene mutations in the Zhejiang region is higher than that of the database, mainly in GJB2c.235delC, SLC26A4 c.919-2A > G, and m.1555A > G variants. The expanded genetic screening in the detection rate of diseasecausing variants was significantly improved. It is helpful in identifying high-risk children for follow-up intervention.

Pregestational screening of hereditary deafness genes carriers in 10,684 normal pregnant women in Zhuzhou, China.

Mutations in genes associated with deafness differ between ethnic groups and regions in China. In this study, we investigated the genes associated with deafness in pregnant women to analyze the distribution of mutations leading to deafness in Zhuzhou, China. A total of 10,684 pregnant women were enrolled in this study. DNA samples were collected to detect the 14 common mutations in deafness genes (at 108 sites). Prevalence of mutations in deafness genes in pregnant women with normal hearing in Zhuzhou was 4.92% (526/10,684). Among these 526 pregnant women with deafness gene mutations, the frequencies of mutated GJB2, GJB3, SLC26A4, and mtDNA 12S rRNA were 40.11, 7.22, 40.68, and 11.98%, respectively. The hotspots for mutations in the deafness genes were: c.235delC in GJB2 (31.18%), c.919-2A > G in SLC26A4 (18.44%), c.299_300delAT in GJB2 (5.70%), m.7444G > A in mtDNA 12S rRNA (5.70%), c.1229C > T in SLC26A4 (5.51%), m.1555A > G in mtDNA 12S rRNA (5.32%), accounting for 71.85%. Moreover, husbands of the 526 pregnant women who carried the deafness gene mutations were also included in the analysis to detect deafness gene mutations. Among the 526 husbands, 23 husbands carried mutations in deafness genes, accounting for 4.37%. The deafness gene mutations of the husbands and pregnant wives were not the same. In addition, the results of the neonatal follow-up hearing tests were all normal. Our study identified the prevalence of mutations in GJB2, SLC26A4, mtDNA 12S rRNA, and GJB3 genes in pregnant women from Zhuzhou, China.

Deafness Gene Mutations in Newborns in the Foshan Area of South China With Bloodspot-Based Genetic Screening Tests.

Purpose The aim of this study was to determine the rate of deafness gene mutations in the Foshan area of South China. Method We enrolled the infants delivered in Foshan Maternity and Children's Healthcare Hospital. Deafness gene mutation was detected by HibriMax method. Our study tested 47,538 newborns within 3 days after birth, including 13 sites in four genes: GJB2 (c.35 del G, c.176 del 16, c.235 del C, c.299 del AT, c.155 del TCTG), GJB3 (c.583 C>T), SLC26A4 (c.2168 A>G, c.919-2 A>G, c.1299 C>T), and mtDNA 12S rRNA (m.1555 A>G, m.1494 C>T, m.12201 T>C, m.7445 A>G). The birth condition of infants was collected, including sex, low or high birth weight, twins, and premature delivery. Results In a total of 47,538 newborns, 1,415 were positively identified with deafness gene mutations. The total rate of the deafness gene mutation was 2.976%. The carrier rates of GJB2 (c.35 del G, c.176 del 16, c.235 del C, c.299 del AT, c.155 del TCTG), GJB3 (c.583 C>T), SLC26A4 (c.2168 A>G, c.919-2 A>G, c.1299 C>T), and mtDNA 12S rRNA (m.1555 A>G, m.1494 C>T, m.12201 T>C, m.7445 A>G) mutations were 0.000%, 0.048%, 1.422%, 0.185%, 0.000%, 0.076%, 0.116%, 0.755%, 0.160%, 0.187%, 0.021%, 0.000%, and 0.006%, respectively. Conclusions Our study showed that the c.235 del C GJB2 mutation was the leading deafness-related mutation in the Foshan area of South China. Deafness gene mutations screening in newborns detected by bloodspot-based genetic screening tests can help the diagnosis of newborn congenital hearing loss.

Cochlear Implantation From the Perspective of Genetic Background.

ABSTRACTWhile cochlear implantation (CI) technology has greatly improved over the past 40 years, one aspect of CI that continues to pose difficulties is the variability of outcomes due to numerous factors involved in postimplantation performance. The electric acoustic stimulation (EAS) system has expanded indications for CI to include patients with residual hearing, and is currently becoming a standard therapy for these patients. Genetic disorders are known to be the most common cause of congenital/early‐onset sensorineural hearing loss, and are also involved in a considerable proportion of cases of late‐onset hearing loss. There has been a great deal of progress in the identification of deafness genes over the last two decades. Currently, more than 100 genes have been reported to be associated with non‐syndromic hearing loss. Patients possessing a variety of deafness gene mutations have achieved satisfactory auditory performance after CI/EAS, suggesting that identification of the genetic background facilitates prediction of post‐CI/EAS performance. When the intra‐cochlear etiology is associated with a specific genetic background, there is a potential for good CI performance. Thus, it is essential to determine which region of the cochlea is affected by identifying the responsible genes. This review summarizes the genetic background of the patients receiving CI/EAS, and introduces detailed clinical data and CI/EAS outcomes in representative examples. Anat Rec, 303:563–593, 2020. © 2020 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Application of PCR reverse dot blot in non-syndromic deafness gene detection

Objective:To detect 20 common deafness gene mutations in non- syndromic deafness patients in China using PCR- RDB, and analyze and summarize the mutation data to explore the clinical value of this method. Method:The PCR- RDB and Sanger sequencing were used to detect 20 common mutations of four deafness genes（GJB2, GJB3, SLC26A4 and mtDNA） in 500 patients with non- syndromic hearing loss . The Sanger sequencing was used to compare the sensitivity, specificity, positive predictive value, negative predictive value, and total coincidence rate of the deafness mutation detected by PCR- RDB. Result:A total of 500 samples were detected. 147 wild- type samples, 81 homozygous mutant samples, 240 heterozygous mutant samples, 32 composite heterozygous mutant samples were detected using the PCR- RDB within the range of 20 gene mutations, which were identical to the Sanger sequencing results. GJB2 c.235delC and SLC26A4 c.919- 2 A>G are the most common hotspot mutations in this study, followed by mtDNA m. 1555 A>G. Compared with the Sanger sequencing method, the sensitivity, specificity, positive predictive value, negative predictive value, and total coincidence rate of the real- time fluorescence PCR melting curve method were 100%, and the Kappa value was one. Conclusion:PCR reverse dot-blot hybridization is a simple, rapid, sensitive and specific method for detecting 20 mutations of 4 common deafness genes in Chinese population, it is expected to be used in clinical detection of deafness genes in the future.

Congenital Middle Ear Malformation with Common Deafness Gene Mutation Analysis: A Review of 813 Profound Sensorineural Hearing Loss Child Patients.

Deafness gene variants play a key role in inner ear malformations. However, the relationship between congenital middle ear malformations and common deafness genes (GJB2, SLC26A4, and mtDNA) in profound sensorineural hearing loss (SNHL) child patients remains poorly investigated. Here we showed that there was no statistical significance in the total mutation frequency of the three common deafness genes in the middle ear malformation group (21.2%, 41/193) in comparison with the normal middle ear and inner ear group (21.0%, 116/553) (χ2 = 0.0061, p = 0.940). Moreover, the mutation ratio of GJB2 and SLC26A4 in the middle ear malformation group (18.7%, 36/193; 2.6%, 5/193) was not significantly different from that in the normal middle ear and inner ear group (17.7%, 98/553; 2.4%, 13/553) (χ2 = 0.084, p = 0.772; χ2 = 0.0000, p = 1.000). The mutation ratio of GJB2 235delC and GJB2 79G>A in the middle ear malformation group (8.8%, 17/193; 8.8%, 17/193) was almost the same to that in the normal middle ear and inner ear group (8.6%, 48/553; 6.7%, 37/553) (χ2 = 0.0030, p = 0.957; χ2 = 0.9556, p = 0.328). The high jugular bulb subgroup analysis also showed the same results. Our findings suggested that GJB2, SLC26A4, and mtDNA mutations might not be related to the middle ear malformations in profound SNHL child patients. Anat Rec, 303:594-599, 2020. © 2019 American Association for Anatomy.

A follow-up study of abnormal mutation in neonatal deafness gene screening

Objective: To screen, diagnose and follow up the abnormal mutation in the gene screening of neonatal deafness. Methods: A total of 24161 newborns born in Zhuhai Maternal and Child Health Hospital from February 1, 2015 to January 31, 2008 were screened for hearing and deafness genes, and audiological screening, diagnosis and 1-3 years follow-up were carried out for the newborns with positive gene screening. Results: There were 991 cases of deafness gene mutation (533 males and 458 females), and the rate of abnormal mutation was 4.10%(991/24 161). Among them, 921 cases were single heterozygous mutation, 130 cases were failed in primary hearing screening, 11 cases were failed in secondary hearing screening, 8 cases were abnormal in audiological diagnosis finally. In these 8 cases, 3 were diagnosed as otitis media and passed audiological follow-up after cure, 2 cases of single ear sensorineural injury caused by high-risk factors, passed after close audiological follow-up, and the other 3 cases were closely audiological follow-up while none of them were successfully sequenced. All of them were moderate to severe sensorineural deafness, 1 case was heterozygous mutation at 3 loci of GJB2(c.235delC,c.408C>A,c.134G>A), 1 case was heterozygous mutation at 2 loci of GJB2(c.235delC, c.109G>A), and 1 case was single heterozygous mutation of GJB2(c.235delC). The remaining 913 cases who passed the primary screening, secondary screening or hearing diagnosis were followed up for 1 to 3 years. Three cases of multiple heterozygous mutation were found in gene screening(2 cases were SLC26A4 2168A>G, IVS7-2A>G, 1 case was GJB2 c.176_191del 16bp, c.299_300del AT), all of them passed both primary and secondary hearing screening. In these 3 cases, the final audiological diagnosis was moderate sensorineural deafness in both ears, with no improvement in the follow-up of 1-3 years. There were 9 monogenic homozygous mutations, 7 failed in primary hearing screening, 3 failed in secondary hearing screening and also failed in audiological diagnosis and 1-3 years' audiological follow-up, all of whom were GJB2 c.235 del C homozygous mutations, and one of whom had a definite family history of deafness. The remaining 6 cases of homozygous mutation diagnosed by primary screening, secondary screening or hearing diagnosis were GJB2 c109G>A homozygous mutation, and passed the 1-3 years' hearing follow-up. 58 children with mtDNA mutations, including 2 with 12S rRNA 1494C>T homozygous mutation, 47 with 1555A>G homozygous mutation, and 9 with 1555A>G heterozygous mutation, all passed the primary or secondary hearing screening, and were instructed to ban ototoxic drugs for the whole life, and passed the 1-3 years' hearing follow-up. Conclusions: The audiological follow-up of children with monogenic heterozygous mutations in deafness gene screening is generally normal. In case of abnormality, the influencing factors such as otitis media should be excluded at first. In case of unexplained moderate to severe sensorineural deafness, the whole-gene sequencing should be performed to find possible pathogenic factors. The children with homozygous mutation or compound heterozygous mutation in gene screening, most of whom show different degrees of hearing loss, should be followed up for a long time, and provide parents with scientific and reasonable genetic counseling according to the mutation genes and loci,. The hearing of drug-induced deafness gene carriers is normal after birth. Parents should be advised to strengthen prevention and follow-up is generally enough.

The prevalence of common genetic deafness related mutation detected by microarray and follow-up in pregnant women in Beijing

Objective To determine the distribution of common deafness gene mutations by microarray-PCR in pregnant women of Beijing, then explore their prevalence and clinical significance. Methods Totally 1 709 pregnant women were prospectively enrolled from the outpatients of Obstetrical Clinical from Peking University Peoples′ Hospital in this study from June 2016 to April 2018. Peripheral blood samples were obtained and DNA templates were extracted from all subjects. The coding region of the GJB2 gene(35del G, 235delC, 176-191del16, 299-300delAT), SLC26A4 gene (IVS7-2 A>G,2168A>G) , 12sRNA gene (1494C>T,1555A>G) and GJB3 gene (538 C>T) were detected by microarray-PCR. Meanwhile, 256 cases firstly recruited in this study were confirmed by Sanger sequencing. The analysis was performed to explore the distribution of deafness gene mutations and the subjects detected to be positive were further followed up until they had given birth to their babies. Results Among 1 709 pregnant women, 89 cases were found to be carrying at least one mutation sites(5.21%).Among them,83 cases were heterozygous mutation(35 cases of GJB2 235delC, 12 cases of GJB2 299-300delAT mutation, one case of GJB2 176-191del 16, 30 cases of SLC26A4 IVS 7-2 A>G, 3 cases of SLC26A4 2168 A>G and two cases of GJB3 538 C>T). There were one case of 235delC homozygous mutation and 2 cases of double mutations(IVS7 -2 A>G/GJB2 299-300delAT, IVS7 -2 A>G/GJB2 235delC). The positive rate of 235delC, 299-300delAT and 176-191del16 was 2.17%, 0.76% and 0.06%, respectively. As to SLC26A4, 1.87% of the pregnant women were carrying IVS 7-2 A>G and 0.18% for 2168 A>G. Two cases were detected carrying GJB3 C>T mutation and three for 12s RNA1555 A>G mutation, respectively. The results of microarray-PCR were identical to those of Sanger sequencing, with the coincidence of 100%.26 spouses of the 56 cases were followed up. Two proved to be carrier of the same gene mutation. One of their babies was born with normal hearing until the end of this research, while another baby was born deafness and implant cochlear when three month old. Conclusions GJB2 235delC and SLC26A4 IVS 7-2 A>G were the most prevalent mutations in pregnant women of Beijing, and it may provide guidance to eugenics and early clinical intervention. Key words: Microarray analysis; Deafness; Connexins; Sulfate transporters; Mutation; Sequence analysis, DNA; Follow-up studies

Advances in cochlear implantation for hereditary deafness caused by common mutations in deafness genes

Abstract The pathogenic factors of deafness are complex; more than 50% of cases are caused by genetic factors. Between 75% and 80% of cases of hereditary hearing impairment are autosomal recessive, 15% to 25% are autosomal dominant, and 1% to 2% are mitochondrial or X-linked. Cochlea implantation is the main method for treating severe and extremely severe bilateral sensorineural deafness and it is widely used in clinical treatment. As clinical cases of cochlea implantation accumulate, differences in the efficacy of implantation in individuals are emerging and attracting attention. In addition to residual hearing level, implantation age, and other factors, gene mutation is an important factor influencing postoperative rehabilitation in patients. With continuous progress in genetic testing technology for deafness, genetic diagnosis has become an important tool in preoperative evaluation and postoperative effect prediction in patients undergoing cochlear implantation. This article reviews the current status and future development of cochlear implantation in the treatment of hereditary deafness resulting from mutations in common deafness-causing genes.

Application of the real-time fluorescence PCR melting curve method in gene screening of non-syndromic hearing loss

Objective: To detect 20 common deafness gene mutations in non-syndromic hearing loss patients in China using the melting curve method, and analyze and summarize the mutation data to explore the clinical value of this method. Methods: The real-time fluorescence PCR melting curve method was used to detect 20 common mutations of four deafness genes(GJB2,GJB3,SLC26A4 and mtDNA) in 492 patients with non-syndromic hearing loss recruited between March 2014 and September 2016 from the Otolaryngology Department of Xiangya Hospital, Central South University(283 males and 209 females, the age ranged from 1 to 48 years old). The Sanger sequencing method was used to compare the sensitivity, specificity, positive predictive value, negative predictive value, and total coincidence rate of the deafness mutation detected by the real-time fluorescence PCR melting curve method. Results: A total of 492 samples were detected. 193 wild-type samples, 93 homozygous mutant samples, 145 heterozygous mutant samples, 59 composite heterozygous mutant samples and 2 samples with unknown mutations were detected using the real-time fluorescence PCR melting curve method within the range of 20 gene mutations, whichwere identical to the Sanger sequencing results.The two samples were detected as unknown mutations by the real-time fluorescent PCR melting curve method were confirmed by Sanger sequencing, including a composite heterozygous mutant sample and a homogenous mutation sample. GJB2 c.235delC and SLC26A4 c.919-2 A>G were the most common hotspot mutations in this study, followed by mtDNA m.1555 A>G. Compared with the Sanger sequencing method, the sensitivity, specificity, positive predictive value, negative predictive value, and total coincidence rate of the real-time fluorescence PCR melting curve method were 100%, the Youden's index was 1.0, and the Kappa value was 1. Conclusions: The real-time fluorescence PCR melting curve method is suitable for the detection of deafness gene mutations. It has the advantages in terms of simple, rapid, high sensitivity and strong specificity and can accurately detect the 20 gene mutations of 4 common deafness genes in Chinese population, which is expected to be used for the clinical detection of deafness genes in the future.

Mutational analysis of 117 patients with non-syndromic hearing loss

To determine the frequencies of deafness gene mutations among patients with non-syndromic hearing loss (NSHL) from northern Jiangsu province. A total of 117 patients with NSHL were enrolled. The coding region of GJB2 gene, IVS7-2A>G and 2168A>G mutations of SLC26A4 gene, and 1555A>G and 1494C>T mutations of mitochondrial DNA 12S rRNA were subjected to Sanger sequencing. Patients in whom no mutation was detected were further tested by targeted gene capture and high-throughput sequencing. Among the 117 patients, 86 (73.50%) were found to carry mutations. GJB2 gene mutations were found in 61 patients (52.14%), including 22 (18.80%) with homozygous mutations and 39 (33.33%) with heterozygous mutations. SLC26A4 gene mutations were found in 19 patients (16.24%), including 4 (3.42%) with homozygous mutations and 15 with heterozygous mutations (14.53%). Mitochondrial 12S rRNA gene mutation was found in 6 patients (5.13%). Targeted gene capture and high-throughput sequencing of 8 patients identified 4 further cases, including 1 with RDX gene 129_130del and 76_79del compound heterozygous mutations, 1 with OTOF gene 1274G>C homozygous mutation, 1 with SLC26A4 gene 919-2A>G and IVS16-6G>A compound heterozygous mutation, and 1 with SLC26A4 gene 919-2A>G and A1673T compound heterozygous mutation. The frequency of mutation among patients with NSHL from north Jiangsu was 73.50%, and GJB2 gene was most commonly mutated.

Mutation screening in non-syndromic hearing loss patients with cochlear implantation by massive parallel sequencing in Taiwan.

ObjectivesTo explore the molecular epidemiology of rare deafness genes in Taiwanese sensorineural hearing impairment (SNHI) patients with cochlear implantation (CI) by performing massive parallel sequencing (MPS) and correlating genetic factors and CI outcomes.MethodsWe enrolled 41 Taiwanese non-syndromic deafness patients with CI that lacked known mutations in common deafness genes. All probands were screened by a targeted exon amplification method that used massively parallel sequencing to screen a customized panel that included 40 relatively rare non-syndromic deafness genes.ResultsThirteen candidate variants in nine relatively rare deafness genes (MYO15A, TMC1, MYH14, MYO3A, ACTG1, COL11A2, DSPP, GRHL2, and WFS1) were identified in 24.4% (10/41) of the non-syndromic deafness probands with CI. According to the ACMG Standards and Guidelines, five variants in MYO15A and ACTG1 were classified as likely pathogenic variants. Two of three multi-generational pedigrees exhibiting deafness were analyzed for the segregation of the disorder with the possible disease-causing variants. Patients with variants detected in most of the identified variant-bearing genes showed relatively good CI outcomes.ConclusionsWe successfully identified candidate variants in partially deaf Taiwanese probands who lacked the known mutations in common deafness genes. Comparing the progress of hearing rehabilitation in CI patients with their apparent causative variants and the expression profiles of their altered genes allowed us to speculate on how alterations in specific gene sets may influence outcomes in hearing rehabilitation after CI.

Screening of hot-spot deafness gene mutations among 277 cochlear implantation patients in Sichuan province

Objective:To investigate the spectrum and incidence of the hot-spot deafness gene mutations of 277 patients with cochlear implantation in Sichuan province, and to provide information of the prevention and treatment for clinical application. Method: The data of the hotspot deafness gene mutations screening of 277 patients with cochlear implantation was analyzed retrospectively. A deafness related gene mutations detection kit was used to detect 9 mutation sites in four deafness-associated genes,including GJB2(35delG,176del16,235delC,299delAT), GJB3(538C＞T),SLC26A4(2168A＞G, IVS7-2A＞G), Mitochondrial 12SrRNA(1494C＞T, 1555A＞G). Result: ① A total of 122 patients with hot-spot Deafness Gene Mutations were detected in 277 cochlear implantation patients(44.04%),among which there were 39 patients were GJB2235delC homozygous mutation(14.08%), 23 patients were GJB2 235delC heterozygous mutation(8.30%), 1 patient was GJB2 299delAT homozygous mutation(0.36%), 2 patients were GJB2 176del16& 235delC compound heterozygous mutation(0.72%), 13 patients were GJB2 235delC& 299delAT compound heterozygous mutation(4.69%), 2 patients were SLC26A4 2168A＞G heterozygous mutation(0.72%), 16 patients were SLC26A4 IVS7-2A＞G homozygous mutation(5.78%), 22 patient were SLC26A4 IVS7-2A＞G heterozygous mutation(7.94%), 1 patients was SLC26A4 2168A＞G& IVS7-2A＞G compound heterozygous mutation(0.36%), 2 patients were mitochondrial 12SrRNA gene 1555A＞G homogenous mutation(0.72%), 1 patient carried both GJB2 235delC homozygous mutation and SLC26A4 IVS7-2A＞G heterozygous mutation(0.36%). ②A total of 49 patients with LVAS were found in 277 cochlear implantation patients: including 15 patients with IVS7-2A＞G homozygous mutation(30.61%), 22 patients with IVS7-2A＞G heterozygous mutation(44.90%), 1 patient with 2168A＞G heterozygous mutation(2.04%), 1 patient with complex heterozygosis mutations of 2168A＞G and IVS7-2A＞G(2.04%), 1 patient with GJB2 235delC homozygous mutation(2.04%) and 1 patient with GJB2 235delC&299delAT compound heterozygous mutation(2.04%), and no hotspot deafness gene mutations were found in 8 patients. ③There were 40 out of 277 cochlear implantation patients with definite family history.There was no statistic difference of the detection rate of hot-spot deafness gene mutations between in patients with family deafness history (57.50%) and in patients without family deafness history (41.77%). ④A total of 273 patients with profound binaural deafness were found among 277 cochlear implantation patients. Three patients with profound deafness in right ear and severe deafness in left ear were found among 277 cochlear implantation patients.Two patients of three were SLC26A4 IVS7-2A＞G heterozygosis mutations, and one patient of three was GJB2 235delC heterozygosis mutations; 1 patient with profound deafness in left ear and severe deafness in right ear was found among 277 cochlear implantation patients,and was GJB2 235delC heterozygosis mutations. Conclusion:① The detection rate of hotspot deafness gene mutations in 277 cochlear implantation patients is 44.04%(122/277). GJB2 Mutation is the most common, SLC26A4 mutation takes the second place, mitochondrial 12SrRNAgene mutation is not common and GJB3 mutation is not found in this study.② SLC26A4 mutation may not be the sole pathogenic factor of LVAS. ③ The results of this study suggest that the genetic background of cochlear implants patients has little effect on the data of the hotspot deafness gene mutations screening.

Concurrent Hearing, Genetic, and Cytomegalovirus Screening in Newborns, Taiwan

To evaluate the feasibility and potential benefits of incorporating genetic and cytomegalovirus (CMV) screenings into the current newborn hearing screening (NHS) programs. Newborns were recruited prospectively from a tertiary hospital and a maternity clinic between May 2016 and December 2016 and were subjected to hearing screening, CMV screening, and genetic screening for 4 common mutations in deafness genes (p.V37I and c.235delC of GJB2 gene, c.919-2A>G of SLC26A4 gene, and the mitochondrial m.1555A>G). Infants with homozygous nuclear mutations or homoplasmic/heteroplasmic mitochondrial mutation (referred to as "conclusively positive genotypes") and those who tested positive for CMV received diagnostic audiologic evaluations. Of the total 1716 newborns enrolled, we identified 20 (1.2%) newborns with conclusively positive genotypes on genetic screening, comprising 15 newborns (0.9%) with GJB2 p.V37I/p.V37I and 5 newborns (0.3%) with m.1555A>G. Three (0.2%) newborns tested positive on CMV screening. Twelve of the 20 newborns (60%) with conclusively positive genotypes and all 3 newborns who tested positive for CMV (100%) passed NHS at birth. Diagnostic audiologic evaluations conducted at 3 months confirmed hearing impairment in 6 of the 20 infants (30%) with conclusively positive genotypes. This study confirms the feasibility of performing hearing, genetic, and CMV screenings concurrently in newborns and provides evidence that the incorporation of these screening tests could potentially identify an additional subgroup of infants with impaired hearing that might not be detected by the NHS programs.