Prevalence of mutations in GJB2, SLC26A4, and mtDNA in children with severe or profound sensorineural hearing loss in southwestern China

Low frequency of SLC26A4 c.919-2A > G variant among patients with nonsyndromic hearing loss in Yunnan of Southwest China

BACKGROUND

Gene variants are responsible for more than half of hearing loss, particularly in nonsyndromic hearing loss (NSHL). The most common pathogenic variant in SLC26A4 gene found in East Asian populations is c.919-2A > G followed by c.2168A > G (p.H723R). This study was to evaluate their variant frequencies in patients with NSHL from special education schools in nine different areas of Southwest China's Yunnan.

METHODS

We performed molecular characterization by PCR-products directly Sanger sequencing of the SLC26A4 c.919-2AG and c.2168 A > G variants in 1167 patients with NSHL including 533 Han Chinese and 634 ethnic minorities.

RESULTS

The SLC26A4 c.919-2A > G variant was discovered in 8 patients with a homozygous state (0.69%) and twenty-five heterozygous (2.14%) in 1167 patients with NSHL. The total carrier rate of the c.919-2A > G variant was found in Han Chinese patients with 4.50% and ethnic minority patients with 1.42%. A significant difference existed between the two groups (P < 0.05). The c.919-2A > G allele variant frequency was ranged from 3.93% in Kunming to zero in Lincang and Nvjiang areas of Yunnan. We further detected the SLC26A4 c.2168 A > G variant in this cohort with one homozygotes (0.09%) and seven heterozygotes (0.60%), which was detected in Baoshan, Honghe, Licang and Pu`er areas. Between Han Chinese group (0.94%) and ethnic minority group (0.47%), there was no statistical significance (P > 0.05). Three Han Chinese patients (0.26%) carried compound heterozygosity for c.919-2A > G and c.2168 A > G.

CONCLUSION

These data suggest that the variants in both SLC26A4 c.919-2A > G and c.2168 A > G were relatively less frequencies in this cohort compared to the average levels in most regions of China, as well as significantly lower than that in Han-Chinese patients. These results broadened Chinese population genetic information resources and provided more detailed information for regional genetic counselling for Yunnan.

A novel intronic variant causing aberrant splicing identified in two deaf Chinese siblings with enlarged vestibular aqueducts

OBJECTIVE

We aimed to evaluate the genotype-phenotype relationship in two Chinese family members with enlarged vestibular aqueduct (EVA).

METHODS

We collected blood samples and clinical data from each pedigree family member. Genomic DNA was isolated from peripheral leukocytes using standard methods. Targeted next-generation sequencing and Sanger sequencing were performed to find the pathogenic mutation in this family. Minigene assays were used to verify whether the novel intronic mutation SLC26A4c.765+4A>G influenced mRNA splicing.

RESULTS

Hearing loss in the patients with EVA was diagnosed using auditory tests and imaging examinations. Two pathogenic mutations, c.765+4A>G and c.919-2A>G were detected in SLC26A4. In vitro minigene analysis confirmed that c.765+4A>G variant could cause aberrant splicing, resulting in skipping over exon 6.

CONCLUSIONS

The SLC26A4c.765+4A>G mutation is the causative variant in the Chinese family with EVA. Particular attention should be paid to intronic variants.

The correlation between deafness progression and SLC26A4 mutations in enlarged vestibular aqueduct patients

BACKGROUND

The relationship between the hearing phenotype and the SLC26A4 mutation in enlarged vestibular aqueduct cases has not been fully elucidated.

OBJECTIVES

To detect SLC26A4 mutation in a group of cases with enlarged vestibular aqueduct who received cochlear implantation and to analyze the correlation between the SLC26A4 genotype and the progression of deafness.

MATERIALS AND METHODS

Twenty-nine enlarged vestibular aqueduct patients were selected. Using the Sanger sequence to analyze SLC26A4 gene mutations. The 29 cases were divided into group A (carrying the c.919-2A > G mutation) and group B (not carrying the c.919-2A > G mutation). The difference in the duration of deafness was analyzed between the two groups.

RESULTS

The detection rate of the c.1174A > T mutation in the postlingual deafness group was 37.5%, higher than that in the prelingual deafness group (0%). The difference in the duration of deafness between groups A and B was not statistically significant by the Mann-Whitney U test (p > 0.05).

CONCLUSIONS

The correlation between the SLC26A4 genotype and the duration of deafness in cases with enlarged vestibular aqueduct is not yet clear. However, the c.1174A > T mutation may be linked to delayed hearing loss and the progression of deafness may be relatively slow in some cases of c.919-2A > G mutation.

Analysis of GJB2 gene mutations spectrum and the characteristics of individuals with c.109G>A in Western Guangdong

BACKGROUND

GJB2 mutations are among the most important causes of deafness, and their prevalence varies greatly among different countries and ethnic groups. This study aimed to determine the pathogenic mutation spectrum of GJB2 in patients with nonsyndromic hearing loss (NSHL) in Western Guangdong and to explore the pathogenic characteristics of the c.109G>A locus.

METHODS

In total, 97 NSHL patients and 212 normal controls (NC) were included in this study. Genetic sequencing analyses were performed on GJB2.

RESULTS

In the NSHL group, the main pathogenic mutations in GJB2 were as follows: c.109G>A, c.235delC, and c.299_300delAT with allele frequencies of 9.28%, 4.12%, and 2.06%, respectively. c.109G>A was the most frequently detected pathogenic mutation in this region. In the NC group, the allele frequency of c.109G>A among 30-50 years old subjects was markedly lower than that among 0-30 years old subjects (5.31% vs. 11.11%, p < 0.05).

CONCLUSION

We found the pathogenic mutation spectrum of GJB2 in this region and showed that c.109G>A was the most common GJB2 mutation with unique characteristics, such as clinical phenotypic heterogeneity and delayed onset. Therefore, the c.109G>A mutation should be considered as an essential marker for routine genetic assessment of deafness, which can also be beneficial for preventing deafness.

The prevalence and risk factors for congenital hearing loss in neonates: A birth cohort study based on CHALLENGE study

OBJECTIVES

To determine the prevalence and risk factors of congenital hearing loss (HL) in neonates based on China Longitudinal Environmental, Genetic, and Economic Cohort (CHALLENGE cohort).

METHODS

Maternal and neonatal data were collected based on the CHALLENGE cohort study from July 2018 to September 2020. Total 7287 neonates underwent the universal newborn hearing screening (UNHS). Babies who did not pass the initial screening and the rescreening were given the formal audiological diagnosis for possible HL. The data was analyzed to find out the prevalence and risk factors for congenital HL in this cohort study.

RESULTS

The prevalence of congenital HL was 3.43‰, and temporary HL was 0.07‰ (5 neonates). The statistical data showed that risk factors, including craniofacial anomalies, neonatal intensive care unit (NICU) admission, family history and advanced maternal age (AMA), could be associated with congenital HL. Additionally, exchange transfusion, assisted ventilation and NICU admission, these three factors could be associated with congenital sensorineural HL (SNHL). Risk factors including craniofacial anomalies, NICU admission, family history and AMA might be contributed to congenital conductive HL(CHL).

CONCLUSION

There were several common risk factors could be contributed to congenital HL, which were consistent with previous studies. However, some risk factors were no longer causing congenital HL due to the improvement of medical treatment and prenatal care. This study has not only helped explain the status quo of the prevalence of congenital HL in China but also laid foundation for future studies.

Genetics of Inner Ear Malformations: A Review

Inner ear malformations are present in 20% of patients with sensorineural hearing loss. Although the first descriptions date to the 18th century, in recent years the knowledge about these conditions has experienced terrific improvement. Currently, most of these conditions have a rehabilitative option. Much less is known about the etiology of these anomalies. In particular, the evolution of genetics has provided new data about the possible relationship between inner ear malformations and genetic anomalies. In addition, in syndromic condition, the well-known presence of sensorineural hearing loss can now be attributed to the presence of an inner ear anomaly. In some cases, the presence of these abnormalities should be considered as a characteristic feature of the syndrome. The present paper aims to summarize the available knowledge about the possible relationships between inner ear malformations and genetic mutations.

Genetic Determinants of Non-Syndromic Enlarged Vestibular Aqueduct: A Review

Hearing loss is the most common sensorial deficit in humans and one of the most common birth defects. In developed countries, at least 60% of cases of hearing loss are of genetic origin and may arise from pathogenic sequence alterations in one of more than 300 genes known to be involved in the hearing function. Hearing loss of genetic origin is frequently associated with inner ear malformations; of these, the most commonly detected is the enlarged vestibular aqueduct (EVA). EVA may be associated to other cochleovestibular malformations, such as cochlear incomplete partitions, and can be found in syndromic as well as non-syndromic forms of hearing loss. Genes that have been linked to non-syndromic EVA are SLC26A4, GJB2, FOXI1, KCNJ10, and POU3F4. SLC26A4 and FOXI1 are also involved in determining syndromic forms of hearing loss with EVA, which are Pendred syndrome and distal renal tubular acidosis with deafness, respectively. In Caucasian cohorts, approximately 50% of cases of non-syndromic EVA are linked to SLC26A4 and a large fraction of patients remain undiagnosed, thus providing a strong imperative to further explore the etiology of this condition.

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

Purpose

The 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.

Methods

This 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.

Results

A 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.

Conclusion

The 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.

Molecular diagnosis of non-syndromic hearing loss patients using a stepwise approach

Hearing loss is one of the most common birth disorders in humans, with an estimated prevalence of 1–3 in every 1000 newborns. This study investigates the molecular etiology of a hearing loss cohort using a stepwise strategy to effectively diagnose patients and address the challenges posed by the genetic heterogeneity and variable mutation spectrum of hearing loss. In order to target known pathogenic variants, multiplex PCR plus next-generation sequencing was applied in the first step; patients which did not receive a diagnosis from this were further referred for exome sequencing. A total of 92 unrelated patients with nonsyndromic hearing loss were enrolled in the study. In total, 64% (59/92) of the patients were molecularly diagnosed, 44 of them in the first step by multiplex PCR plus sequencing. Exome sequencing resulted in eleven diagnoses (23%, 11/48) and four probable diagnoses (8%, 4/48) among the 48 patients who were not diagnosed in the first step. The rate of secondary findings from exome sequencing in our cohort was 3% (2/58). This research presents a molecular diagnosis spectrum of 92 non-syndromic hearing loss patients and demonstrates the benefits of using a stepwise diagnostic approach in the genetic testing of nonsyndromic hearing loss.

Three years of follow-up of otodental syndrome in 3-year-old Chinese boy: a rare case report

BACKGROUND

Otodental syndrome is an exceptionally rare autosomal dominant condition characterized by a delayed eruption of posterior teeth, globodontia, lisping, and sensorineural hearing loss. In this case report, we reported a 3-year-old Chinese boy with the otodental syndrome.

CASE PRESENTATION

A 3-year-old Chinese boy was referred to our hospital with complaint of no eruption of primary canines and molars. Three years follow-up showed lately erupted bulbous primary canines with hypoplastic enamel spot, globe-shaped primary molars and sensorineural hearing loss at 4 and a half-year-old age. We diagnosed otodental syndrome in the patient's mother with hearing loss at 16-year-old age. Gene sequencing and analysis of deafness-related genes GJB2, GJB3, SLC26A4, and mtDNA did not reveal any mutation or SNPs in the patient and his mother.

CONCLUSIONS

This case report highlights the importance of detailed medical, dental, and family history examination, as well as multi-disciplinary teamwork for diagnosis and treatment of otodental syndrome.

Mutation analysis of common deafness-causing genes among 506 patients with nonsyndromic hearing loss from Wenzhou city, China

OBJECTIVES

The frequency and spectrum of mutations in deafness-causing genes differs significantly according to the ethnic population and region under investigation. The molecular etiology of nonsyndromic hearing loss (NSHL) in Wenzhou, China, has not yet been systematically elucidated. To provide accurate genetic testing and counseling in this area, we investigated the molecular etiology of NSHL in a deaf population from Wenzhou.

METHODS

A total 506 unrelated patients with NSHL were enrolled in this study. Nine hotspot mutations in four major deafness genes were investigated by sequencing (Group I: 187 patients enrolled between 2011 and 2015) or allele-specific PCR-based universal array (Group II: 319 patients enrolled between 2016 and 2017). The investigated genes included GJB2 (c.35delG, c.176_191del16, c.235delC, c.299-300delAT), SLC26A4 (c.2168A > G, c.919-2A > G), mtDNA 12SrRNA (m.1555A > G, m.1494C > T), and GJB3 (c.538C > T). Furthermore, whole coding region sequencing or improved multiplex ligation detection reaction (IMLDR) were performed for patients who carried mono-allelic variants of GJB2 and SLC26A4, in order to detect other mutations among these patients.

RESULTS

GJB2 mutations were detected in 22.92% (116/506) of the entire cohort and SLC26A4 mutations were found in 6.52% (33/506) of the cohort. GJB3 mutations were detected in 0.79% (4/506) of the cohort. The mutation rate of mitochondrial DNA 12SrRNA in our patients was 17.40% (88/506), including 17.00% (86/506) with the m.1555A > G mutation and 0.40% (2/506) with the m.1494C > T mutation. The allelic frequency of the c.235delC mutation was 14.62% (148/1012), which is significantly higher than that of c.109G > A (33/1012, 3.26%), c.299_300delAT (13/1012, 1.28%), and c.176_191del16 (6/1012, 0.59%). The most common pathogenic mutation of SLC26A4 was the c.919-2A > G mutation (37/1012, 3.66%), followed by c.2168A > G (6/1012, 0.59%), and c.1229C > T (4/1012, 0.40%). Moreover, five rare pathogenic variants of GJB2 and eight rare pathogenic variants of SLC26A4 were identified.

CONCLUSION

GJB2 is the primary deafness-causing gene in deaf patients from Wenzhou, China; this is consistent with what is observed in most Chinese populations. However, the surprisingly high rate of the m.1555A > G mutation (17.00%) in patients from Wenzhou was significantly higher than in other populations in China. These findings highlight the specificity of the common deafness-causing gene mutation spectrum in the Wenzhou area. This information may be of benefit for genetic counseling and risk assessment for deaf patients from this area.

Mutation spectrum and hotspots of the common deafness genes in 314 patients with nonsyndromic hearing loss in Heze area, China

Background: Although, half of the childhood deafness is genetically related, the molecular etiology of hearing impairment has not been demonstrated explicitly. In addition, the mutation spectrums of deafness genes vary among different areas and ethnics. Objectives: To know more about the mutation spectrums of deafness genes in China, we tested the mutations of three common deafness genes (GJB2, SLC26A4, and mtDNA12SrRNA) in a particular deafness population from Heze area. Materials and methods: SNPscan technology was utilized to perform mutation screening for these three common deafness genes in 314 nonsyndromic deaf patients from Heze area. Results: 38.21% (120/314) of these 314 patients with nonsyndromic hearing loss from Heze area were related to the genetic defects in these three deafness genes, including 20.06% (63/314) for GJB2, 15.29% (48/314) for SLC26A4, and 2.87% (9/314) for mtDNA12SrRNA. Furthermore, the mutation hotspots in three deaf genes were GJB2 235delC, SLC26A4 c.919-2A > G, and mtDNA12SrRNA 1555A > G, respectively, distinct from hotspots reported in other regions worldwide. Conclusion: Our results disclosed a special and unique mutation spectrum of these three common deaf genes in Heze deaf population.

Mutation analysis of common deafness genes among 1,201 patients with non-syndromic hearing loss in Shanxi Province

Background

Hearing impairment is one of most frequent birth defects, which affects nearly 1 in every 1,000 live births. However, the molecular etiology of non‐syndromic deafness in China is not well studied. Here, we have investigated the presence of mutations in three genes commonly mutated in non‐syndromic deafness patients in Shanxi Province, which has the highest frequency of birth defects in China.

Methods

In total, 1,201 unrelated non‐syndromic deafness patients and 300 healthy individuals were enrolled. The hearing ability was confirmed by audiologic evaluation. Three major deafness‐related genes (GJB2, SLC26A4 (PDS), and mtDNA 12S rRNA) of all individuals enrolled were analyzed by Sanger sequencing.

Results

The results showed that GJB2 mutations accounted for 21.23% (255/1,201) in the patient group, with c.235delC, a hotspot mutation, accounting for 10.99% (132/1,201). Moreover, 11 new GJB2 mutations were identified. SLC26A4 mutations accounted for 9.33% (112/1,201) in the patient group, with IVS7‐2A>G as the most prevalent mutation accounting for 4.75% (57/1,201). In addition, 15 patients (1.25%) were found to carry mtDNA 12S rRNA c.1555A>G mutation, while only two cases had the mtDNA 12S rRNA c.1494C>T.

Conclusion

In our research, it was found that c.235delC in GJB2 and c.919‐2A>G (IVS7‐2A>G) in SLC26A4 were the highest frequency pathogenic variants in Shanxi Province. Taken together, our data will enrich the database of deafness mutations and will help clinical diagnosis, treatment, and genetic counseling of hearing impairment.

Prevalence of mutations in the GJB2, SLC26A4, GJB3, and MT-RNR1 genes in 103 children with sensorineural hearing loss in Shaoxing, China

Mutations in the GJB2, SLC26A4, GJB3, and MT-RNR1 genes are known to be a common cause of hearing loss. However, the frequency of hot-spot mutations and genotype-phenotype correlations in patients with sensorineural hearing loss (SNHL) has been less frequently reported. We conducted a study of 103 children-56 boys and 47 girls, aged 5 months to 9 years (mean: 4.1 yr)-with SNHL who underwent genetic screening for 20 hot-spot mutations of the GJB2, SLC26A4, GJB3, and MT-RNR1 genes. Mutations were detected by multiple-PCR-based MALDI-TOF MS assay. At least one mutated allele was detected in 48 patients (46.6%), and 30 patients (29.1%) carried pathogenic mutations. Among all the detected mutations, the most common were GJB2 c.235delC and SLC26A4 c.919-2A>G, with allele frequencies of 23.8 and 6.8%, respectively. At least one mutant allele of SLC26A4 was detected in the 13 patients who had an enlarged vestibular aqueduct (EVA). Almost half of the children with SNHL carried a common deafness-related mutation, and nearly one-third carried a pathogenic mutation. The mutations in SLC26A4 were prevalent and correlated strongly with EVA.

Genetic mutations in non-syndromic deafness patients in Hainan Province have a different mutational spectrum compared to patients from Mainland China

OBJECTIVES

To provide appropriate genetic testing and counseling for non-syndromic hearing impairment patients in Hainan Province, an island in the South China Sea.

METHODS

299 unrelated students with non-syndromic hearing loss who attended a special education school in Hainan Province were enrolled in this study. Three prominent deafness-related genes (GJB2, SLC26A4, and mtDNA 12S rRNA) were analyzed using Sanger sequencing.

RESULTS

GJB2 mutations were detected in 32.78% (98/299) of the entire cohort; however, only 5.69% (17/299) had two confirmed pathogenic mutations. The most common mutation observed in this population was c.109G > A in the GJB2 gene, with an allelic frequency of 15.05% (90/598), which is significantly higher than that reported in previous cohorts. A total of 16 patients had two confirmed pathogenic SLC26A4 gene mutations, and 16 patients had one. The IVS7-2A > G mutation was the most commonly observed, with an allelic frequency of 3.51% (21/598). Three patients had a m.1555A > G mutation in the mtDNA 12S rRNA gene.

CONCLUSIONS

These results reveal that genetic etiology occurred in 11.71% (35/299) of patients, suggesting that Hainan province have a different mutational spectrum compare to Mainland China in non-syndromic deafness patients, which provide useful information to genetic counseling in Hainan province.

Recent Advancements in the Regeneration of Auditory Hair Cells and Hearing Restoration

Neurosensory responses of hearing and balance are mediated by receptors in specialized neuroepithelial sensory cells. Any disruption of the biochemical and molecular pathways that facilitate these responses can result in severe deficits, including hearing loss and vestibular dysfunction. Hearing is affected by both environmental and genetic factors, with impairment of auditory function being the most common neurosensory disorder affecting 1 in 500 newborns, as well as having an impact on the majority of elderly population. Damage to auditory sensory cells is not reversible, and if sufficient damage and cell death have taken place, the resultant deficit may lead to permanent deafness. Cochlear implants are considered to be one of the most successful and consistent treatments for deaf patients, but only offer limited recovery at the expense of loss of residual hearing. Recently there has been an increased interest in the auditory research community to explore the regeneration of mammalian auditory hair cells and restoration of their function. In this review article, we examine a variety of recent therapies, including genetic, stem cell and molecular therapies as well as discussing progress being made in genome editing strategies as applied to the restoration of hearing function.

Navigating genetic diagnostics in patients with hearing loss

PURPOSE OF REVIEW

In the age of targeted genomic enrichment and massively parallel sequencing, there is no more efficient genetic testing method for the diagnosis of hereditary hearing loss. More clinical tests are on the market, which can make choosing good tests difficult.

RECENT FINDINGS

More and larger comprehensive genetic studies in patients with hearing loss have been published recently. They remind us of the importance of looking for both single nucleotide variation and copy number variation in all genes implicated in nonsyndromic hearing loss. They also inform us of how a patient's history and phenotype provide essential information in the interpretation of genetic data.

SUMMARY

Choosing the most comprehensive genetic test improves the chances of a genetic diagnosis and thereby impacts clinical care.

Genetic frequencies related to severe or profound sensorineural hearing loss in Inner Mongolia Autonomous Region

The aim was to study the frequencies of common deafness-related mutations and their contribution to hearing loss in different regions of Inner Mongolia. A total of 738 deaf children were recruited from five different ethnic groups of Inner Mongolia, including Han Chinese (n=486), Mongolian (n=216), Manchurian (n=24), Hui (n=6) and Daur (n=6). Nine common mutations in four genes (GJB2, SLC26A4, GJB3 and mitochondrial MT-RNR1 gene) were detected by allele-specific PCR and universal array. At least one mutated allele was detected in 282 patients. Pathogenic mutations were detected in 168 patients: 114 were homozygotes and 54 were compound heterozygotes. The 114 patients were carriers of only one mutated allele. The frequency of GJB2 variants in Han Chinese (21.0%) was higher than that in Mongolians (16.7%), but not significantly different. On the other hand, the frequency of SLC26A4 variants in Han Chinese (14.8%) was lower than that in Mongolians (19.4%), but also not significantly different. The frequency of patients with pathogenic mutations was different in Ulanqab (21.4%), Xilingol (40.0%), Chifeng (40.0%), Hulunbeier (30.0%), Hohhot (26.3%), and in Baotou (0%). In conclusion, the frequency of mutated alleles in deafness-related genes did not differ between Han Chinese and Mongolians. However, differences in the distribution of common deafness-related mutations were found among the investigated areas of Inner Mongolia.

Characterization of ATPase Activity of P2RX2 Cation Channel

P2X purinergic receptors are plasma membrane ATP-dependent cation channels that are broadly distributed in the mammalian tissues. P2RX2 is a modulator of auditory sensory hair cell mechanotransduction and plays an important role in hair cell tolerance to noise. In this study, we demonstrate for the first time in vitro and in cochlear neuroepithelium, that P2RX2 possesses the ATPase activity. We observed that the P2RX2 V60L human deafness mutation alters its ability to bind ATP, while the G353R has no effect on ATP binding or hydrolysis. A non-hydrolysable ATP assay using HEK293 cells suggests that ATP hydrolysis plays a significant role in the opening and gating of the P2RX2 ion channel. Moreover, the results of structural modeling of the molecule was in agreement with our experimental observations. These novel findings suggest the intrinsic ATPase activity of P2RX2 and provide molecular insights into the channel opening.

Effects of epigallocatechin-3-gallate on proliferation and differentiation of mouse cochlear neural stem cells: Involvement of PI3K/Akt signaling pathway

Since the majority of hearing impaired patients suffer from the significant loss of sensory hair cells and associated neurons, stem cell-based approaches hold great promise by replacing the damaged tissues in the ears. For instance, stem cells from the spiral ganglion could be isolated and expanded to regenerate neural structures of the inner ear. It is thus necessary to explore the potential procedures that may promote the proliferation and differentiation of such cochlear neural stem cells. In the present study, we study the effects of epigallocatechin-3-gallate (EGCG), a known antioxidant, for potential therapeutic use in NSC regeneration. At a non-toxic concentration, EGCG stimulated both proliferation and neurosphere formation in isolated mouse cochlear neural stem cell (NSC) in vitro. Specifically, the neural differentiation of NSC was promoted by EGCG treatment. The up-regulated neural function by EGCG was also supported by the increased calcium spike frequencies and enhanced neurite complexity in NSC-differentiated neurons. Finally, the induced neuron differentiation and Akt activation of cochlear NSC by EGCG were blocked by PI3 kinase inhibition. These data suggested that EGCG acts through phosphoinositide 3-kinase (PI3K)/Akt signaling in cochlea NSC to promote cell growth and neuron differentiation, which may be exploited for the treatment of hearing loss.