Clinical Application of the 4K-3D Exoscope System in Cochlear Implantation.

PURPOSE: To evaluate a system for otomicrosurgery based on 4K three-dimensional (3D) exoscope technology and apply it to cochlear implantation. METHODS: An open stereoscopic vision-based surgical system, which differs from traditional surgical microscopes, was created by utilizing 4K stereo imaging technology and combining it with low-latency 4K ultra-high-definition 3D display. The system underwent evaluation based on 57 cochlear implantation operations, three designed microscopic manipulations, and a questionnaire survey. RESULTS: The surgical images displayed by the 4K-3D exoscope system (4K-3D-ES) are stereoscopic, clear, and smooth. The use of 4K-3D-ES in cochlear implantation is not inferior to traditional microscopes in terms of intraoperative bleeding and surgical complications, and the surgical duration is not slower or may even be faster than when using traditional microscopes. The results of micromanipulation experiments conducted on 16 students also confirmed this and demonstrated that 4K-3D-ES can be easily adapted. Furthermore, additional advantages of 4K-3D-ES were gathered. Significantly enlarged and high-definition stereoscopic images contribute to the visualization of finer anatomical microstructures such as chordae tympani, ensuring safer surgery. Users feel more comfortable in their necks, shoulders, waists, and backs. Real-time shared stereoscopic view for multiple people, convenient for collaboration and teaching. The ear endoscope and 4K-3D-ES enable seamless switching on the same screen. High-definition 3D images and videos can be saved with just one click, making future publication and communication convenient. CONCLUSION: The feasibility and safety of 4K-3D-ES for cochlear implantation surgery have been demonstrated. The 4K-3D-ES also offers numerous unique advantages and holds clinical application and promotional value.

Addition of an affected family member to a previously ascertained autosomal recessive nonsyndromic hearing loss pedigree and systematic phenotype-genotype analysis of splice-site variants in MYO15A.

Pathogenic variants in MYO15A are known to cause autosomal recessive nonsyndromic hearing loss (ARNSHL), DFNB3. We have previously reported on one ARNSHL family including two affected siblings and identified MYO15A c.5964+3G > A and c.8375 T > C (p.Val2792Ala) as the possible deafness-causing variants. Eight year follow up identified one new affected individual in this family, who also showed congenital, severe to profound sensorineural hearing loss. By whole exome sequencing, we identified a new splice-site variant c.5531+1G > C (maternal allele), in a compound heterozygote with previously identified missense variant c.8375 T > C (p.Val2792Ala) (paternal allele) in MYO15A as the disease-causing variants. The new affected individual underwent unilateral cochlear implantation at the age of 1 year, and 5 year follow-up showed satisfactory speech and language outcomes. Our results further indicate that MYO15A-associated hearing loss is good candidates for cochlear implantation, which is in accordance with previous report. In light of our findings and review of the literatures, 58 splice-site variants in MYO15A are correlated with a severe deafness phenotype, composed of 46 canonical splice-site variants and 12 non-canonical splice-site variants.

Analysis of the genotype-phenotype correlation of MYO15A variants in Chinese non-syndromic hearing loss patients.

BACKGROUND: Mutations in the MYO15A gene are a widely recognized cause of autosomal recessive non-syndromic sensorineural hearing loss (NSHL) globally. Here, we examined the role and the genotype-phenotype correlation of MYO15A variants in a cohort of Chinese NSHL cases. METHODS: Eighty-one cases with evidenced MYO15A variants from the 2263 Chinese NSHL cases, who underwent next-generation sequencing (NGS), were enrolled in the study. We investigated the association of MYO15A variants with the severity, progression and age of onset of hearing loss, as well as compared it to the previous reports in different nationalities. The cases were divided into groups according to the number of truncating variants: 2 truncating, 1 truncating and 1 non-truncating, 2 non-truncating variants, and compared the severity of HL among the groups. RESULTS: MYO15A accounted for 3.58% (81/2263) of all NSHL cases. We analyzed 81 MYO15A-related NSHL cases, 73 of whom were with congenital bilateral, symmetric or severe-to-profound hearing loss (HL), however, 2 of them had a postlingual, asymmetric, mild or moderate HL. There were 102 variants identified in all MYO15A structural domains, 76.47% (78/102) of whom were novel. The most common types of detected variants were missense (44/102, 43.14%), followed by frameshift (27/102, 26.47%), nonsense (14/102, 13.72%), splice site (10/102, 9.80%), in frame (4/102, 3.92%), non-coding (2/102, 1.96%) and synonymous (1/102, 0.98%). The most recurrent variant c.10245_10247delCTC was detected in 12 cases. We observed that the MYO15A variants, located in its N-terminal, motor and FERM domains, led to partial deafness with better residual hearing at low frequencies. There were 34 cases with biallelic truncating variants, 37 cases with monoallelic truncating variants, and 13 cases with biallelic non-truncating variants. The biallelic non-truncating variants group had the least number of cases (12/81), and most of them (10/12) were with profound NSHL. CONCLUSIONS: MYO15A is a major gene responsible for NSHL in China. Cases with MYO15A variants mostly showed early-onset, symmetric, severe-to-profound hearing loss. This study is by far the largest focused on the evaluation of the genotype-phenotype correlations among the variants in the MYO15A gene and its implication in the outcome of NSHL. The biallelic non-truncating MYO15A variants commonly caused profound HL, and the cases with one or two truncating MYO15A variants tended to increase the risk of HL. Nevertheless, further investigations are needed to clarify the causes for the variable severities and progression rates of hearing loss and the detected MYO15A variants in these cases.

Transcriptome analysis of the early stage ifnlr1-mutant zebrafish indicates the immune response to auditory dysfunction.

BACKGROUND: IFNLR1 has been recently identified to be related to autosomal dominant nonsyndromic sensorineural hearing loss (ADNSHL). It is reported to be expressed in the inner ear of mice and the lateral line of zebrafish. However, it remains unclear how defects in this gene lead to hearing loss. OBJECTIVES: To elucidate the global gene expression changes in zebrafish when the expression of ifnlr1 is downregulated. METHODS: Transcriptome analysis was performed on ifnlr1 morpholino knockdown zebrafish and the control zebrafish using RNA-seq technology. RESULTS: The results show that 262 differentially expressed genes (DEGs) were up-regulated while 146 DEGs were down-regulated in the E4I4-Mo zebrafish larvae compared to the control-Mo. Six pathways were significantly enriched, including steroid biosynthesis pathway, adipocytokine signaling pathway, cytokine-cytokine receptor interaction pathway, p53 signaling pathway, AGE-RAGE signaling pathway in diabetic complications, and terpenoid backbone biosynthesis pathway. Among them, three pathways (steroid biosynthesis pathway, cytokine-cytokine receptor interaction pathway and p53 signaling pathway) are immune-associated. CONCLUSIONS: The transcriptome analysis results contribute to the groundwork for future research on the pathogenesis of IFNLR1-associated hearing loss.

Identification of TMPRSS3 as a Significant Contributor to Autosomal Recessive Hearing Loss in the Chinese Population.

Hereditary hearing loss is characterized by a high degree of genetic heterogeneity. Mutations in the TMPRSS3 (transmembrane protease, serine 3) gene cause prelingual (DFNB10) or postlingual (DFNB8) deafness. In our previous study, three pathogenic mutations in TMPRSS3 were identified in one Chinese family. To evaluate the importance of TMPRSS3 mutations in recessive deafness among the Chinese, we screened 150 autosomal recessive nonsyndromic hearing loss (ARNSHL) families and identified 6 that carried seven causative TMPRSS3 mutations, including five novel mutations (c.809T>A, c.1151T>G, c.1204G>A, c.1244T>C, and c.1250G>A) and two previously reported mutations (c.323-6G>A and c.916G>A). Each of the five novel mutations was classified as severe, by both age of onset and severity of hearing loss. Together with our previous study, six families were found to share one pathogenic mutation (c.916G>A, p.Ala306Thr). To determine whether this mutation arose from a common ancestor, we analyzed six short tandem repeat (STR) markers spanning the TMPRSS3 gene. In four families, we observed linkage disequilibrium between p.Ala306Thr and STR markers. Our results indicate that mutations in TMPRSS3 account for about 4.6% (7/151) of Chinese ARNSHL cases lacking mutations in SLC26A4 or GJB2 and that the recurrent TMPRSS3 mutation p.Ala306Thr is likely to be a founder mutation.

Identification of Two Novel Compound Heterozygous PTPRQ Mutations Associated with Autosomal Recessive Hearing Loss in a Chinese Family.

Mutations in PTPRQ are associated with deafness in humans due to defects of stereocilia in hair cells. Using whole exome sequencing, we identified responsible gene of family 1572 with autosomal recessively non-syndromic hearing loss (ARNSHL). We also used DNA from 74 familial patients with ARNSHL and 656 ethnically matched control chromosomes to perform extended variant analysis. We identified two novel compound heterozygous missense mutations, c. 3125 A>G p.D1042G (maternal allele) and c.5981 A>G p.E1994G (paternal allele), in the PTPRQ gene, as the cause of recessively inherited sensorineural hearing loss in family 1572. Both variants co-segregated with hearing loss phenotype in family 1572, but were absent in 74 familial patients. Heterozygosity for c. 3125 A>G was identified in two samples from unaffected Chinese individuals (656 chromosomes). Therefore, the hearing loss in this family was caused by two novel compound heterozygous mutations in PTPRQ.

[Assessment of the curative effective of cochlear implantation in childer with GJB2-associated NSSNHL].

OBJECTIVE: To analyze the curative effect of CI in children with GJB2-associated NSSNHL. METHOD: The evaluations of curative effect with CI include auditory threshold, IT-MAIS/MAIS, CAP, SIR. MESP. The outcomes of 40 cases with GJB2-associated NSSNHI, were compared 80 patients with negative results of screening of gene mutation (control group). RESULT: In comparison with control group the auditory threshold in children with GJB2-associated NSSNIL is better, however had no significant difference in other tests (P > 0.05). CONCLUSION: CI could he performed on children with GJB2-associated NSSNHL. Postoperative outcomes of hearing and speech were satisfied.

Novel compound heterozygous mutations in the MYO15A gene in autosomal recessive hearing loss identified by whole-exome sequencing.

BACKGROUND: Inherited genetic defects play an important role in congenital hearing loss, contributing to about 60% of deafness occurring in infants. Hereditary nonsyndromic hearing loss is highly heterogeneous, and most patients with a presumed genetic etiology lack a specific molecular diagnosis. METHODS: By whole exome sequencing, we identified responsible gene of family 4794 with autosomal recessively nonsyndromic hearing loss (ARNSHL). We also used DNA from 56 Chinese familial patients with ARNSHL (autosomal recessive nonsyndromic hearing loss) and 108 ethnicity-matched negative samples to perform extended variants analysis. RESULTS: We identified MYO15A c.IVS25+3G>A and c.8375 T>C (p.V2792A) as the disease-causing mutations. Both mutations co-segregated with hearing loss in family 4794, but were absent in the 56 index patients and 108 ethnicity-matched controls. CONCLUSIONS: Our results demonstrated that the hearing loss of family 4794 was caused by novel compound heterozygous mutations in MYO15A.

[Prenatal genetic test and clinical guidance for 213 hereditary deaf families].

OBJECTIVE: To summarize the workflow, strategy and experience of prenatal genetic test for deafness based on the 6-year clinical practice. METHODS: There were 213 families who received prenatal test from 2005 to 2011. Among the 213 families, 205 families had had one deaf child, including 204 couples with normal hearing and one couple of the deaf husband and normal wife, 8 families including 6 couples with normal hearing and 2 deaf couples, had no child before test. Genomic and mitochondrial DNA of each subject was extracted from whole blood. The etiology and recurrent risks in 212 families were confirmed by means of the genetic test of GJB2, SLC26A4 and mtDNA 12sRNA, but one family carried POU3F4 c.647G > A heterozygous mutation causing X-linked hereditary hearing impairment confirmed by pedigree study. The prenatal test was carried out during the pregnancy of all mothers from 11 to 30 weeks, and the following genetic information and counseling were supplied based on the results. RESULTS: The recurrent risk was 25% in 209 families, including 204 families with one deaf child and 5 families without child, among which all couples were GJB2 or SLC26A4 mutation carriers and deaf children were caused by homozygous or compound GJB2/SLC26A4 mutations; The recurrent risk was 50% in 3 families, the father and his child in one family had compound SLC26A4 mutations and the mother with heterozygous SLC26A4 mutation, the wife had POU3F4 c.647G > A heterozygous mutation in another one family, and the husband with compound SLC26A4 mutations and the wife with mtDNA A1555G mutation and heterozygous SLC26A4 mutation simultaneously happened in the rest one family; The recurrent risk was 100% in one family of the deaf couple who were both found to carry homozygous or compound GJB2 mutations, and the deaf wife got pregnant by artificial insemination with the sperm from the local Human Sperm Bank. 226 times of prenatal test were applied in all 213 families that 11 families of them received prenatal test twice, and one family received three times. 46 times of prenatal testing showed that the fetuses carried parental mutations simultaneously or the same mutations with probands; while 180 times of prenatal test showed that the fetuses carried only one parental mutation or did not carry any mutation from parents. The following visit showed that all of these 180 families had given birth to babies who were all revealed to have normal hearing by new born hearing screening test. CONCLUSIONS: Prenatal diagnosis for deafness assisted by genetic test can provide efficient information about offspring's hearing condition, and the normative workflow and precise strategy highly guarantee the safe and favorable implementation of prenatal diagnosis.

Extremely discrepant mutation spectrum of SLC26A4 between Chinese patients with isolated Mondini deformity and enlarged vestibular aqueduct.

BACKGROUND: Mutations in SLC26A4 cause Pendred syndrome (hearing loss with goiter) or DFNB4 (non-syndromic hearing loss with inner ear malformation, such as enlarged vestibular aqueduct or Mondini deformity). The relationship between mutations in SLC26A4 and Mondini deformity without enlarged vestibular aqueduct has not been studied in any Chinese deaf population. The purpose of this study was to assess whether mutations in the SLC26A4 gene cause Mondini deformity without an enlarged vestibular aqueduct (isolated Mondini deformity) in a Chinese population. METHODS: In total, 144 patients with sensorineural hearing loss were included and subjected to high-resolution temporal bone CT. Among them, 28 patients with isolated Mondini dysplasia (MD group), 50 patients with enlarged vestibular aqueduct with Mondini dysplasia (EVA with MD group), 50 patients with enlarged vestibular aqueduct without Mondini dysplasia (EVA group), and 16 patients with other types of inner ear malformations (IEM group) were identified. The coding exons of SLC26A4 were analyzed in all subjects. RESULTS: DNA sequence analysis of SLC26A4 was performed in all 144 patients. In the different groups, the detection rate of the SLC26A4 mutation differed. In the isolated MD group, only one single allelic mutation in SLC26A4 was found in one patient (1/28, 3.6%). In the EVA with MD group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0%) and three patients (3/50, 6.0%), respectively. Also, in the EVA group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0%) and three patients (3/50, 6.0%), respectively. These percentages were identical to those in the EVA plus MD group. Only two patients carried monoallelic mutations of the SLC26A4 gene in the IEM group (2/16, 12.5%). There were significant differences in the frequency of SLC26A4 mutation among the groups (P<0.001). The detection rate of SLC26A4 mutation in the isolated MD group was significantly lower than in the EVA group (with or without MD; P<0.001), and there was no significant difference in the detection rate of SLC26A4 between the MD group and IEM group (P>0.5). CONCLUSION: Although mutations in the SLC26A4 gene were frequently found in Chinese EVA patients with and without MD, there was no evidence to show a relationship between isolated MD and the SLC26A4 gene in the Chinese population examined. Hearing impairment in patients with isolated MD may be caused by factors other than mutations in the SLC26A4 gene.

[Analysis of positive rate of common genetic mutations in 1448 cases with different hearing phenotype].

OBJECTIVE: To analyze the positive rate of common genetic mutations in Chinese non-syndromic sensorineural hearing loss groups with different hearing phenotype. METHOD: One thousand four hundred and forty-eight subjects with hearing test results received at least one of three genetic testings including: mutations in coding region of GJB2 and SLC26A4 with sequencing analysis and mitochondrial DNA C1494T/A1555G with microarray detection. Of 1448 subjects, 1333 have bilateral sensorineural hearing loss, 65 have unilateral hearing loss and 50 have normal hearing threshold even though they have high frequency hearing loss or family history. The informed consent of each subject was achieved. RESULT: Mutation positive rate of GJB2, SLC26A4 and mtDNA C1494T/ A1555G of 1448 subjects were 19.23%, 27.55%, 0.1% and 1.72% respectively. The positive rate of GJB2 and SLC26A4 mutations in bilateral hearing loss group (20.22%, 29.17%) was statistically significantly higher than unilateral group (0, 0) (P < 0.01). In bilateral hearing loss group, the positive rate of GJB2 mutations was highest in the profound group (24.67%), and then severe (22.33%), moderate (14.33%) and mild group (6.58%) (P < 0.01). The positive rate of SLC26A4 mutations was highest in the severe group (48.67%), and then profound (28.42%), moderate (21.16%) and mild (8.93%) (P < 0.01). CONCLUSION: The positive rate of GJB2 and SLC26A4 mutations is high in the groups with bilateral profound and severe sensorineural hearing loss, whose genetic testing should be put emphasis on. However, the genetic testing should be performed in patients with mild to moderate hearing impairment as well if necessary.

[Prenatal genetic counseling and instruction for deaf families by genetic test].

OBJECTIVE: Analyzed the molecular pathogenesis of probands by means of genetic test and assisted the local Family Planning Institute by providing prenatal genetic counseling and instruction for deaf families who eager to have more baby. METHODS: Total of forty-three deaf families were recruited by two institutes for family planning from Guangzhou and Weifang. Forty-two families had one deaf child with normal hearing parents. One family was that parents and their child were all deaf. Genetic testing of GJB2, SLC26A4 and mitochondrial DNA (mtDNA) 12SrRNA were firstly performed in probands and their parents, following medical history, physical examination, auditory test and CT scan of temporal bone were completed. And then the genetic information and instruction were provided to each deaf family. RESULTS: Fifteen of these 43 families had positive results of genetic test. In fifteen families, one family was confirmed that the parents and their child all carried homozygous GJB2 mutations and the recurrence risk was 100%. Twelve families were confirmed that the probands carried homozygous/compound GJB2 or SLC26A4 mutations while their parents were GJB2 or SLC26A4 carriers, and the recurrence risk was 25%. One family was confirmed that the proband, diagnosed with enlarged vestibular aqueduct syndrome (EVAS) by CT scan, carried heterozygous SLC26A4 mutation from the mother, and the recurrence risk was still 25% based on the hereditary pattern of EVAS although another SLC26A4 mutation from the father was not found. One family was confirmed that the proband carried a heterozygous GJB2 mutation from the mother and the possibility to be GJB2 carrier for offsprings was 50%. The rest 28 families were that all probands and their parents did not carry GJB2, SLC26A4 and mtDNA 12SrRNA pathological mutation. CONCLUSIONS: Genetic testing can provide more accurate and useful prenatal genetic counseling and instruction to deaf families. Meanwhile, it is an ideal way to develop a cooperative relationship with the institute for family planning.

[Sequencing analysis of whole SLC26A4 gene related to IVS7-2A > G mutation in 1552 moderate to profound sensorineural hearing loss patients in China].

OBJECTIVE: To investigate the whole sequence of SLC26A4 gene among 1552 deaf students from 21 regions of China with SLC26A4 hot spot mutation IVS7-2A > G and analyze the epidemiological state of enlarged-vestibular-aqueduct-syndrome (EVAS) related hearing loss in China. METHODS: DNA was extracted from peripheral blood of 1552 students from deaf and dumb school of 21 regions in China. The nationality of the 1552 cases covers Han (1290 cases), Uigur (69 cases), Hui (37 cases), Mongolia (31 cases), Yi, Zhuang, Bai, Miao and other 13 nationalities (125 cases). Firstly, all subjects were analyzed for the hot spot mutation IVS7-2A > G by direct sequencing. Those carrying a single heterozygous IVS7-2A > G were given further analyzed for the probable second mutation in other exons except exon7 and exon8 of SLC26A4. One hundred and fifty cases with normal hearing were in the control group. RESULTS: The sequencing results revealed 197 cases carrying IVS7-2A > G, of whom 83 carrying IVS7-2A > G homozygous mutation, 114 carrying IVS7-2A > G heterozygous mutation. Of the 114 cases with heterozygous IVS7-2A > G, 78 cases were found to have another mutation and 36 cases were found no other mutation in SLC26A4. Of the 1552 cases, the percentage of cases carrying homozygous IVS7-2A > G and compound heterozygous mutations was 10.37% (161/1552). Of the 78 cases with SLC26A4 compound heterozygous mutations, the mutations except IVS7-2A > G were found mainly in exon 19, 10, 17, 15, 11 + 12, 14 and 3. Twenty-one novel SLC26A4 mutations were found. In the control group, there were only 3 cases carrying heterozygous IVS7-2A > G, and no other mutation in SLC26A4 was found. CONCLUSIONS: SLC26A4 mutations account for at least 10% of EVAS related hereditary hearing loss in China. It's of great importance to screen SLC26A4 gene for making aetiological diagnosis for deafness. The discovery of novel variants of SLC26A4 gene makes the mutational and polymorphic spectrum more plentiful in Chinese population. We also provide preliminary evidence for the hot spot areas of SLC26A4.

Distinct and novel SLC26A4/Pendrin mutations in Chinese and U.S. patients with nonsyndromic hearing loss.

Mutations of the human SLC26A4/PDS gene constitute the most common cause of syndromic and nonsyndromic hearing loss. Definition of the SLC26A4 mutation spectrum among different populations with sensorineural hearing loss is important for development of optimal genetic screening services for congenital hearing impairment. We screened for SLC26A4 mutations among Chinese and U.S. subjects with hearing loss, using denaturing HPLC (DHPLC) and direct DNA sequencing. Fifty-two of 55 Chinese subjects with deafness accompanied by enlargement of the vestibular aqueduct (EVA) exhibited at least one mutant SLC26A4 allele, whereas SLC26A4 mutations were found in only 2 of 116 deaf Chinese patients without EVA. The spectrum of SLC26A4 mutations differed among Chinese and U.S. subjects and included 10 previously unreported SLC26A4 variants: 4 in the Chinese population (p.E303Q, p.X329, p.X467, p.X573) and 6 in the U.S. population (p.V250A, p.D266N, p.F354S, p.D697A, p.K715N, p.E737D). Among the seven novel in-frame missense mutations, five encoded SLC26A4 proteins with substantially reduced Cl(-)/anion exchange activity as expressed and measured in Xenopus oocytes, but four of these were sufficiently active to allow study of anion selectivity. The only mutant polypeptide exhibiting complete loss of anion exchange function, p.E303Q, was expressed at or near the oocyte surface at near-wild-type levels. Two variants, p.F354S and p.E737D, displayed selective reduction in relative rate of Cl(-)/HCO(3)(-) exchange compared with similarly measured rates of Cl(-)/Cl(-) and Cl(-)/I(-) exchange. Our data show that mutation analysis of the SLC26A4 gene is of high diagnostic yield among subjects with deafness and bilateral EVA in both China and the U.S. However, the pathogenicity of monoallelic SLC26A4 gene variants in patients with hearing loss remains unclear in many instances.

[Etiologic analysis of severe to profound hearing loss patients from Chifeng city in Inner Mongolia].

OBJECTIVE: To investigate the etiology of patients with severe to profound hearing loss and to identify the ratio of hereditary hearing loss in Chifeng area in Northern China. METHODS: DNA were extracted from peripheral blood of 134 deaf patients from Chifeng special educational school and 100 normal hearing controls in Northern China. Audiology examinations showed that all patients had severe to profound bilateral sensorineural hearing impairment. Sequence analysis of the whole coding areas of GJB2, GJB3, GJB6, SLC26A4, mtDNA12SrRNA and mtDNAtRNASer(UCN) were performed. Individuals carrying SLC26A4 mutation were given further temporal bone CT scan. RESULTS: The ratio of hearing loss related to genetic factors in this population was 60.45% (81/134). About 33.58% (45/134) of the patients were given accurate genetic diagnosis. GJB2 mutations were responsible for approximately 17.16% of the cases in ChiFeng area. By screening SLC26A4 followed by temporal bone CT scan, we diagnosed 20 cases of enlarged vestibular aqueduct (EVA) and/or other inner ear malformation. SLC26A4 mutations account for about 14.93% of the cases. The aminoglycoside-related mtDNA 1555A>G mutation accounted for 0.76% of the cases in Chifeng area. In addition, another 13.43% (18/134) of the cases carried heterozygous GJB2 mutation and their hearing loss may be related to GJB2. 6.72% (9/134) of the cases carried heterozygous SLC26A4 mutation who were not found EVA by temporal bone CT or not took CT examination for some reasons. However, their hearing loss may also be SLC26A4-related. About 2.24% (3/134) of the cases carried mtDNA 12SrRNA 1095 T>C which may also be an aminoglycoside-related mutation and very likely be the cause of hearing loss. GJB3 might participate in the pathomechanism of hearing loss in 1.49% (2/134) of the patients. GJB6 mutation was not detected in this population. CONCLUSIONS: The ratio of hearing loss related to genetic factors in the sample drawing population from Chifeng was 60.45% (81 cases). GJB2 is the most common gene and SLC26A4 is the second common gene next to GJB2 that cause deafness in this area.

Molecular etiology of hearing impairment in Inner Mongolia: mutations in SLC26A4 gene and relevant phenotype analysis.

BACKGROUND: The molecular etiology of hearing impairment in Chinese has not been thoroughly investigated. Study of GJB2 gene revealed that 30.4% of the patients with hearing loss in Inner Mongolia carried GJB2 mutations. The SLC26A4 gene mutations and relevant phenotype are analyzed in this study. METHODS: One hundred and thirty-five deaf patients were included. The coding exons of SLC26A4 gene were sequence analyzed in 111 patients, not including 22 patients carrying bi-allelic GJB2 mutations or one patient carrying a known GJB2 dominant mutation as well as one patient with mtDNA 1555A>G mutation. All patients with SLC26A4 mutations or variants were subjected to high resolution temporal bone CT scan and those with confirmed enlarged vestibular aqueduct and/or other inner ear malformation were then given further ultrasound scan of thyroid and thyroid hormone assays. RESULTS: Twenty-six patients (19.26%, 26/135) were found carrying SLC26A4 mutation. Among them, 17 patients with bi-allelic SLC26A4 mutations were all confirmed to have EVA or other inner ear malformation by CT scan. Nine patients were heterozygous for one SLC26A4 mutation, including 3 confirmed to be EVA or EVA and Mondini dysplasia by CT scan. The most common mutation, IVS7-2A>G, accounted for 58.14% (25/43) of all SLC26A4 mutant alleles. The shape and function of thyroid were confirmed to be normal by thyroid ultrasound scan and thyroid hormone assays in 19 of the 20 patients with EVA or other inner ear malformation except one who had cystoid change in the right side of thyroid. No Pendred syndrome was diagnosed. CONCLUSION: In Inner Mongolia, China, mutations in SLC26A4 gene account for about 12.6% (17/135) of the patients with hearing loss. Together with GJB2 (23/135), SLC26A4 are the two most commonly mutated genes causing deafness in this region. Pendred syndrome is not detected in this deaf population. We established a new strategy that detects SLC26A4 mutations prior to the temporal bone CT scan to find EVA and inner ear malformation patients. This model has a unique advantage in epidemiologic study of large deaf population.

Mutations at position 7445 in the precursor of mitochondrial tRNA(Ser(UCN)) gene in three maternal Chinese pedigrees with sensorineural hearing loss.

We report here the clinical, genetic and molecular characterization of three Chinese pedigrees with nonsyndromic bilateral hearing loss. Clinical and genetic evaluations revealed the variable severity and age-of-onset in hearing impairment in these families. Strikingly, there were extremely low penetrances of hearing impairment in these Chinese families. Sequence analysis of the complete mitochondrial DNA (mtDNA) showed the known A7445C mutation in two pedigrees and the novel A7445T mutation in another pedigree, in addition to distinct sets of mtDNA polymorphisms belong to Asian haplogroups D4j and F4. Indeed, the A7445C or A7445T mutation in the CO1 and the precursor of tRNA(Ser(UCN)) genes was present in homoplasmy only in the maternal lineage of those pedigrees but not other members of these families and 164 Chinese controls. In fact, the A7445C or A7445T mutation results in a read-through of the stop condon AGA of the CO1 message on the H strand of mtDNA, thereby adding three amino acids (Ser-Gln-Lys) to the C-terminal of the polypeptide. However, the mutated polypeptide may retain a partial function. Alternatively, the A7445C or A7445T mutation is adjacent to the site of 3' end endonucleolytic processing of L-strand RNA precursor, spanning tRNA(Ser(UCN)) and ND6 mRNA. Thus, the A7445C or A7445T mutation may also cause a defect in the processing of the L-strand RNA precursor, thus causing mitochondrial dysfunctions. Furthermore, the occurrence of the mutations at position 7445 in these genetically unrelated subjects affected by hearing impairment strongly indicates that mutations at the position 7445 are involved in the pathogenesis of hearing impairment.

[Prenatal diagnosis for hereditary deaf families assisted by genetic testing].

OBJECTIVE: To provide prenatal diagnosis for deaf families, which the first child was confirmed to be hereditary deafness caused by gap junction beta-2 (GJB2) or SLC26A4 (PDS) mutation, to avoid another deaf birth in these families. METHODS: Eight deaf families joined in this study. Each family had one child with severe to profound hearing loss while parents had normal hearing except a deaf father from family 8; mothers had been pregnant for 6-28 weeks. Genetic testing of GJB2, SLC26A4 and mitochondrial DNA (mtDNA) A1555G mutation were firstly performed in probands and their parents whose DNA was extracted from peripheral blood, and then prenatal testing was carried out in the fetus whose DNA was extracted from different fetus materials depending on the time of gestation. RESULTS: The probands from family 1-4 were found to carry homozygous or compound GJB2 mutations while their parents carried corresponding heterozygous GJB2 mutations. The probands from family 5-8 and the deaf father from family 8 were found to carry compound SLC26A4 mutations while their parents and the mother from family 8 carried a single SLC26A4 mutation. Prenatal testing showed that the fetuses from family 1, 5, 8 only carried the paternal mutation and the fetuses from family 2, 3, 6 didn't carry any GJB2 or SLC26A4 mutations. The new born babies from these six families all had normal hearing revealed by new born hearing screening. However, the fetuses from family 4,7 carried the same mutations with probands in each family. The parents from family 4, 7 decide to terminate pregnancy. CONCLUSION: Prenatal diagnosis assisted by genetic testing can provide efficient information about hearing condition of their offsprings.

[Audiological and vestibular evaluation of new coagulation factor C homology mutation carriers in a Chinese family].

OBJECTIVE: To analyze the clinical features of audiological and vestibular function in a Chinese family with late onset autosomal dominant nonsyndromic sensorineural hearing loss. METHODS: Comprehensive audiological and vestibular evaluation including pure tone audiometry, auditory brainstem response (ABR), electrocochleogram (EcochG), oculomotor testing, caloric tests, rotational testing, computerized dynamic posturography and vestibular evoked myogenic potentials (VEMP) were conducted to identify the hearing and vestibular impairment. RESULTS: All affected family members shared sensorineural hearing loss with full penetrance starting between the second and fifth decade of life as a high frequency loss which progresses to a severe to profound loss at the sixth to seventh decade. The extensive vestibular evaluation indicated that all affected members performed normally in computerized dynamic posturography and caloric testing. Impairment of the saccular otolith in all of six affected members was suggested by results of the VEMP test. The velocity step test generated abnormal time constants and sinusoidal oscillation test generated abnormal gains and phase in affected members indicated that horizontal canal vestibular hyporeflexia in history. All affected subjects examined in this family showed completely normal ocular motor responses in oculomotor testing, including smooth pursuit, optokinetic nystagmus, gaze and saccade. CONCLUSIONS: The predominant feature of the Chinese DFNA9 family was that all the affected subjects harboring COCH mutation in the vWFA2 domain didn't suffer the vestibular symptoms during their life time and comprehensive vestibular assessment revealed only subtle vestibular hypofunction in affected members of this family. There is a genotype-phenotype correlation in DFNA9.