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The cochlea’s ability to discriminate sound frequencies is facilitated by a special topography along its longitudinal axis known as tonotopy. Auditory hair cells located at the base of the cochlea respond to high-frequency sounds, whereas hair cells at the apex respond to lower frequencies. Gradual changes in morphological and physiological features along the length of the cochlea determine each region’s frequency selectivity, but it remains unclear how tonotopy is established during cochlear development. Recently, sonic hedgehog (SHH) was proposed to initiate the establishment of tonotopy by conferring regional identity to the primordial cochlea. Here, using mouse genetics, we provide in vivo evidence that regional identity in the embryonic cochlea acts as a framework upon which tonotopy-specific properties essential for frequency selectivity in the mature cochlea develop. We found that follistatin (FST) is required for the maintenance of apical cochlear identity, but dispensable for its initial induction. In a fate-mapping analysis, we found that FST promotes expansion of apical cochlear cells, contributing to the formation of the apical cochlear domain. SHH, in contrast, is required both for the induction and maintenance of apical identity. In the absence of FST or SHH, mice produce a short cochlea lacking its apical domain. This results in the loss of apex-specific anatomical and molecular properties and low-frequency-specific hearing loss.

Background and Objectives Several studies have shown that three single nucleotide polymorphisms (SNPs) in the TAS2R38 gene demonstrate a strong association with the ability to sense the bitter taste of phenylthiocarbamide (PTC) in. We have previously reported about TAS2R38 genotypes in normal volunteers. The aim of this study was to investigate the role TAS2R38 gene plays in taste disorder by examining SNPs in the TAS2R38 gene in taste disorder patients.Subjects and Method Ninety-four patients with taste dysfunction from multiple etiologies were enrolled. The genotypes were defined by identifying SNPs on the TAS2R38 gene. The proportion of different TAS2R38 genotypes in the group was compared with that in the normal volunteers of our previous study. The whole mouth taste threshold tests were performed and the thresholds were compared among the three different genotypic groups.Results The proportion of each diplotype in taste disorder patients were as follows: PAV/ PAV 36.2% (34/94), PAV/AVI 34.0% (32/94), and AVI/AVI 29.8% (28/94). The proportion of AVI/AVI type was higher in the group than in the normal volunteers (p=0.031). The detection and recognition thresholds of all four basic tastes were increased in the order of PAV/PAV, PAV/AVI, and AVI/AVI genotypes.Conclusion The proportion of AVI/AVI homozygous was significantly higher in taste disorder patients than in the normal volunteers. Our findings suggest that the genotypes of TAS2R38 may represent one of the risk factors responsible for the development of taste disorders.

Background Cisplatin (CP) is an effective anticancer drug broadly used for various types of cancers, but it has shown ototoxicity that results from oxidative stress. Berberine has been reported for its anti-oxidative stress suggesting its therapeutic potential for many diseases such as colitis, diabetes, and vascular dementia. Objective Organ of Corti of postnatal day 3 mouse cochlear explants were used to compare hair cells after the treatment with cisplatin alone or with berberine chloride (BC) followed by CP. Methods We investigated the potential of the anti-oxidative effect of BC against the cisplatin-induced ototoxicity. We observed a reduced aberrant bundle of stereocilia in hair cells in CP with BC pre-treated group. Caspase-3 immunofluorescence and TUNEL assay supported the hypothesis that BC attenuates the apoptotic signals induced by CP. Reactive oxygen species level in the mitochondria were investigated by MitoSOX Red staining and the mitochondrial membrane potentials were compared by JC-1 assay. Results BC decreased ROS generation with preserved mitochondrial membrane potentials in mitochondria as well as reduced DNA fragmentation in hair cells. In summary, our data indicate that BC might act as antioxidant against CP by reducing the stress in mitochondria resulting in cell survival. Conclusion Our result suggests the therapeutic potential of BC for prevention of the detrimental effect of CP-induced ototoxicity.

Contains fulltext : 243959.pdf (Publisher’s version ) (Closed access) PURPOSE: The ClinGen Variant Curation Expert Panels (VCEPs) provide disease-specific rules for accurate variant interpretation. Using the hearing loss-specific American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines, the Hearing Loss VCEP (HL VCEP) illustrates the utility of expert specifications in variant interpretation. METHODS: A total of 157 variants across nine HL genes, previously submitted to ClinVar, were curated by the HL VCEP. The curation process involved collecting published and unpublished data for each variant by biocurators, followed by bimonthly meetings of an expert curation subgroup that reviewed all evidence and applied the HL-specific ACMG/AMP guidelines to reach a final classification. RESULTS: Before expert curation, 75% (117/157) of variants had single or multiple variants of uncertain significance (VUS) submissions (17/157) or had conflicting interpretations in ClinVar (100/157). After applying the HL-specific ACMG/AMP guidelines, 24% (4/17) of VUS and 69% (69/100) of discordant variants were resolved into benign (B), likely benign (LB), likely pathogenic (LP), or pathogenic (P). Overall, 70% (109/157) variants had unambiguous classifications (B, LB, LP, P). We quantify the contribution of the HL-specified ACMG/AMP codes to variant classification. CONCLUSION: Expert specification and application of the HL-specific ACMG/AMP guidelines effectively resolved discordant interpretations in ClinVar. This study highlights the utility of ClinGen VCEPs in supporting more consistent clinical variant interpretation.

Hereditary spastic paraplegia (HSP) is a heterogeneous inherited disorder that manifests with lower extremity weakness and spasticity. HSP can be inherited by autosomal dominant, autosomal recessive, and X-linked inheritance patterns. Recent studies have shown that, although rare, mutations in a single gene can lead to multiple patterns of inheritance of HSP. We enrolled the HSP family showing autosomal dominant inheritance and performed genetic study to find the cause of phenotype in this family. We recruited five members of a Korean family as study participants. Four of the five family members had pure HSP. Part of the family members underwent whole-exome sequencing (WES) to identify the causative mutation. As the result of WES and Sanger sequencing analysis, a novel missense mutation (c.452 C > T, p.Ala151Val) of ERLIN2 gene was identified as the cause of the autosomal dominant HSP in the family. Our study suggests that the ERLIN2 gene leads to both autosomal recessive and autosomal dominant patterns of inheritance in HSP. Moreover, autosomal dominant HSP caused by ERLIN2 appears to cause pure HSP in contrast to autosomal recessive ERLIN2 related complicated HSP (SPG18).

Drug-induced hearing loss is a major type of acquired sensorineural hearing loss. Cisplatin and aminoglycoside antibiotics have been known to cause ototoxicity, and excessive accumulation of intracellular reactive oxygen species (ROS) are suggested as the common major pathology of cisplatin- and aminoglycoside antibiotics-induced ototoxicity. Fursultiamine, also called thiamine tetrahydrofurfuryl disulfide, is a thiamine disulfide derivative that may have antioxidant effects. To evaluate whether fursultiamine can prevent cisplatin- and kanamycin-induced ototoxicity, we investigated their preventive potential using mouse cochlear explant culture system. Immunofluorescence staining of mouse cochlear hair cells showed that fursultiamine pretreatment reduced cisplatin- and kanamycin-induced damage to both inner and outer hair cells. Fursultiamine attenuated mitochondrial ROS accumulation as evidenced by MitoSOX Red staining and restored mitochondrial membrane potential in a JC-1 assay. In addition, fursultiamine pretreatment reduced active caspase-3 and TUNEL signals after cisplatin or kanamycin treatment, indicating that fursultiamine decreased apoptotic hair cell death. This study is the first to show a protective effect of fursultiamine against cisplatin- and aminoglycoside antibiotics-induced ototoxicity. Our results suggest that fursultiamine could act as an antioxidant and anti-apoptotic agent against mitochondrial oxidative stress.in cochlear hair cells.

Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system has ushered in a new era of gene therapy. In this study, we aimed to demonstrate precise CRISPR/Cas9-mediated genome editing of the splicing mutation c.919-2A > G in intron 7 of the SLC26A4 gene, which is the second most common causative gene of congenital hearing loss. We designed candidate single-guide RNAs (sgRNAs) aimed to direct the targeting of Staphylococcus aureus Cas9 to either exon 7 or exon 8 of SLC26A4. Several of the designed sgRNAs showed targeting activity, with average indel efficiencies ranging from approximately 14% to 25%. The usage of dual sgRNAs delivered both into Neuro2a cells and primary mouse embryonic fibroblasts resulted in the successful removal of large genomic fragments within the target locus. We subsequently evaluated genome editing in the presence of artificial donor templates to induce precise target modification via homology-directed repair. Using this approach, two different donor plasmids successfully introduced silent mutations within the c.919-2A region of Slc26a4 without evident off-target activities. Overall, these results indicate that CRISPR/Cas9-mediated correction of mutations in the Slc26a4 gene is a feasible therapeutic option for restoration of hearing loss.

Targeting specific cell types in the mammalian inner ear is important for treating genetic hearing loss due to the different cell type-specific functions. Adeno-associated virus (AAV) is an efficient in vivo gene transfer vector, and it has demonstrated promise for treating genetic hearing loss. Although more than 100 AAV serotypes have been identified, few studies have investigated whether AAV can be distributed to specific inner ear cell types. Here we screened three EGFP-AAV reporter constructs (serotypes DJ, DJ8, and PHP.B) in the neonatal mammalian inner ear by injection via the round window membrane to determine the cellular specificity of the AAV vectors. Sensory hair cells, supporting cells, cells in Reissner’s membrane, interdental cells, and root cells were successfully transduced. Hair cells in the cochlear sensory epithelial region were the most frequently transduced cell type by all tested AAV serotypes. The recombinant DJ serotype most effectively transduced a range of cell types at a high rate. Our findings provide a basis for improving treatment of hereditary hearing loss using targeted AAV-mediated gene therapy. Keywords: gene therapy, genetic hearing loss, inner ear, adeno-associated virus, serotype

Rationale: Mutations of SLC26A4 that abrogate pendrin, expressed in endolymphatic sac, cochlea and vestibule, are known to cause autosomal recessive sensorineural hearing loss with enlargement of the membranous labyrinth. This is the first study to demonstrate the feasibility of gene therapy for pendrin-related hearing loss. Methods: We used a recombinant viral vector to transfect Slc26a4 cDNA into embryonic day 12.5 otocysts of pendrin-deficient knock-out (Slc26a4∆/∆ ) and pendrin-deficient knock-in (Slc26a4tm1Dontuh/tm1Dontuh ) mice. Results: Local gene-delivery resulted in spatially and temporally limited pendrin expression, prevented enlargement, failed to restore vestibular function, but succeeded in the restoration of hearing. Restored hearing phenotypes included normal hearing as well as sudden, fluctuating, and progressive hearing loss. Conclusion: Our study illustrates the feasibility of gene therapy for pendrin-related hearing loss, suggests differences in the requirement of pendrin between the cochlea and the vestibular labyrinth, and documents that insufficient pendrin expression during late embryonal and early postnatal development of the inner ear can cause sudden, fluctuating and progressive hearing loss without obligatory enlargement of the membranous labyrinth.

Significance Auditory neuropathy spectrum disorder (ANSD) is a confounding auditory disease in which the subjects respond to sound but have difficulties in speech discrimination. Herein, we examined two Asian families with hereditary late-age–onset ANSD. By linkage analysis and exome sequencing, we identified the TMEM43-p.(Arg372Ter) variant as the etiology of the disease. To examine the mechanism of TMEM43 on ANSD, we generated a knock-in mouse with the p.(Arg372Ter) variant that recapitulated the progressive hearing loss phenotype of the two families. We discovered that variation in TMEM43 impairs the connexin-linked function of mediating passive conductance current in cochlear glial cells. Based on the pathology involving cochlear glial cells, we performed cochlear implant on the human patients, and their speech discrimination ability was restored., Genes that are primarily expressed in cochlear glia-like supporting cells (GLSs) have not been clearly associated with progressive deafness. Herein, we present a deafness locus mapped to chromosome 3p25.1 and an auditory neuropathy spectrum disorder (ANSD) gene, TMEM43, mainly expressed in GLSs. We identify p.(Arg372Ter) of TMEM43 by linkage analysis and exome sequencing in two large Asian families segregating ANSD, which is characterized by inability to discriminate speech despite preserved sensitivity to sound. The knock-in mouse with the p.(Arg372Ter) variant recapitulates a progressive hearing loss with histological abnormalities in GLSs. Mechanistically, TMEM43 interacts with the Connexin26 and Connexin30 gap junction channels, disrupting the passive conductance current in GLSs in a dominant-negative fashion when the p.(Arg372Ter) variant is introduced. Based on these mechanistic insights, cochlear implant was performed on three subjects, and speech discrimination was successfully restored. Our study highlights a pathological role of cochlear GLSs by identifying a deafness gene and its causal relationship with ANSD.

Genes that are primarily expressed in cochlear glia-like supporting cells (GLSs) have not been clearly associated with progressive deafness. Herein, we present a deafness locus mapped to chromosome 3p25.1 and an auditory neuropathy spectrum disorder (ANSD) gene, TMEM43, mainly expressed in GLSs. We identify p.(Arg372Ter) of TMEM43 by linkage analysis and exome sequencing in two large Asian families segregating ANSD, which is characterized by inability to discriminate speech despite preserved sensitivity to sound. The knock-in mouse with the p.(Arg372Ter) variant recapitulates a progressive hearing loss with histological abnormalities in GLSs. Mechanistically, TMEM43 interacts with the Connexin26 and Connexin30 gap junction channels, disrupting the passive conductance current in GLSs in a dominant-negative fashion when the p.(Arg372Ter) variant is introduced. Based on these mechanistic insights, cochlear implant was performed on three subjects, and speech discrimination was successfully restored. Our study highlights a pathological role of cochlear GLSs by identifying a deafness gene and its causal relationship with ANSD.

Simple Summary In this study, we confirmed the changes in hearing function and inner ear structure over a long period of time in DBA/2 mice, a laboratory animal model suitable for studying hearing loss. We believe that our study is the first to report findings regarding hearing function and structural changes in DBA/2 mice aged ≥34 weeks. These results are of significance for researchers and the scientific community using laboratory animal models. Abstract DBA/2 mice are a well-known animal model for hearing loss developed due to intrinsic properties of these animals. However, results on the phenotype of hearing loss in DBA/2 mice have been mainly reported at an early stage in mice aged ≤7 weeks. Instead, the present study evaluated the hearing ability at 5, 13, and 34 weeks of age using DBA/2korl mice. Auditory brainstem response test was performed at 8–32 KHz at 5, 13, and 34 weeks of age, and hearing loss was confirmed to be induced in a time-dependent manner. In addition, histopathological evaluation at the same age confirmed the morphological damage of the cochlea. The findings presented herein are the results of the long-term observation of the phenotype of hearing loss in DBA/2 mice and can be useful in studies related to aging-dependent hearing loss.

Genes that are primarily expressed in cochlear glia-like supporting cells (GLSs) have never been clearly associated with progressive deafness. Herein, we present a novel deafness locus mapped to chromosome 3p25.1 and a new auditory neuropathy spectrum disorder (ANSD) gene TMEM43 mainly expressed in GLSs. We identify p.R372X of TMEM43 by linkage analysis and exome sequencing in two large Asian families. The knock-in (KI) mouse with p.R372X mutation recapitulates a progressive hearing loss with histological abnormalities exclusively in GLSs. Mechanistically, TMEM43 interacts with Cx26 and Cx30 gap junction channels, disrupting the passive conductance current in GLSs in a dominant-negative fashion when the p.R372X mutation is introduced. Based on the mechanistic insights, cochlear implant was performed on two patients and speech discrimination was successfully restored. Our study highlights a pathological role of cochlear GLSs by identifying a novel deafness gene and its causal relationship with ANSD.

Cisplatin (CP) is a chemotherapeutic drug used to treat cancerous solid tumors, but it causes serious side effects, including ototoxicity. The major cause of CP-induced ototoxicity is increased levels of mitochondrial reactive oxygen species (ROS). In this study, we examined the effect of 2-Isopropyl-3H-naphtho(1,2-d)imidazole-4,5-dione (KL1333), a β-lapachone derivative, on CP-induced ototoxicity using ex vivo organotypic culture system of cochlea. Hair cell damages in CP-treated cochlear explants with or without KL1333 were compared by immunohistochemistry. CP-induced oxidative stress and the preventive effect of KL1333 were analyzed by measuring intracellular ROS levels and depolarization of mitochondrial membrane potential. Activation of apoptosis signaling pathway was detected using TUNEL assay and immunostaining of cleaved caspase-3. As the results, it was found that KL1333 pretreatment significantly decreased stereocilia degeneration and hair cell loss, and prevented an increase in mitochondrial ROS levels in response to CP. Immunohistochemical examinations of cochlear explants revealed greater caspase-3 immunopositivity in the CP group than in controls, while the KL1333 + CP group showed significantly less immunopositivity than the CP group (P < 0.05). Thus, it appeared that KL1333 protected hair cells in the organ of Corti from CP-induced apoptosis by decreasing mitochondrial damages due to the production of mitochondrial ROS. This study is the first report showed the preventive effect of KL1333 against CP-induced ototoxicity. Although further studies should be performed to determine if KL1333 could maintain anticancer effect of CP, our data cautiously suggests that the antioxidant KL1333 can be used as an effective anti-apoptotic agent to prevent ototoxicity caused by CP-induced oxidative stress, and may prove useful in preventing hearing loss caused by CP.

Outer hair cells (OHCs) play an essential role in hearing by acting as a nonlinear amplifier which helps the cochlea detect sounds with high sensitivity and accuracy. This nonlinear sound processing generates distortion products, which can be measured as distortion-product otoacoustic emissions (DPOAEs). The OHC stereocilia that respond to sound vibrations are connected by three kinds of extracellular links: tip links that connect the taller stereocilia to shorter ones and convey force to the mechanoelectrical transduction channels, tectorial membrane-attachment crowns (TM-ACs) that connect the tallest stereocilia to one another and to the overlying TM, and horizontal top connectors (HTCs) that link adjacent stereocilia. While the tip links have been extensively studied, the roles that the other two types of links play in hearing are much less clear, largely because of a lack of suitable animal models. Here, while analyzing genetic combinations of tubby mice, we encountered models missing both HTCs and TM-ACs or HTCs alone. We found that the tubby mutation causes loss of both HTCs and TM-ACs due to a mislocalization of stereocilin, which results in OHC dysfunction leading to severe hearing loss. Intriguingly, the addition of the modifier allele modifier of tubby hearing 1 in tubby mice selectively rescues the TM-ACs but not the HTCs. Hearing is significantly rescued in these mice with robust DPOAE production, indicating an essential role of the TM-ACs but not the HTCs in normal OHC function. In contrast, the HTCs are required for the resistance of hearing to damage caused by noise stress.

The-state-of-art CRISPR/Cas9 is one of the most powerful among the approaches being developed to rescue fundamental causes of gene-based inheritable diseases. Several strategies for delivering such genome editing materials have been developed, but the safety, efficacy over time, cost of production, and gene size limitations are still under debate and must be addressed to further improve applications. In this study, we evaluated branched forms of the polyethylenimine (PEI) - branched PEI 25 kDa (BPEI-25K) - and found that it could efficiently deliver CRISPR/Cas9 plasmids. Plasmid DNA expressing both guide RNA and Cas9 to target the Slc26a4 locus was successfully delivered into Neuro2a cells and meditated genome editing within the targeted locus. Our results demonstrated that BPEI-25K is a promising non-viral vector to deliver the CRISPR/Cas9 system in vitro to mediate targeted gene therapy, and these findings contribute to an understanding of CRISPR/Cas9 delivery that may enable development of successful in vivo techniques.

For successful wound treatment, therapeutics must be delivered directly to the wound. Various issues restrict the delivery of antibiotics to wounds, including the barrier mannered by necrotic tissue and biofilms, which create an extracellular polymeric layer that impedes the efficient administration of therapeutics. For achieving break of the necrotic tissue barrier and biofilm, in addition, improving antibiotics penetration through a painless administration, we fabricated porous polymer coatings on microneedles (MNs) which had the ability of automatic “release” therapeutics in response to wound pH conditions. In the pores of the porous polymer film, the model drug was packed using aqueous gelatin porogen, and the porous layer was coated with a Eudragit S100 film to cap the pores to prevent drug leakage and provide a wound pH-responsive drug release. By combining the advantages of porous and pH-responsive polymer coatings, the coated MNs exhibited remarkably enhanced therapeutic results. This formulation showed both in vivo (in rats) and in vitro (in phosphate-buffered saline and in porcine skin) wound pH-sensitive drug release with rapid responsiveness. At healthy skin pH (pH 4.5), an insignificant release was noticed for MNs in the test media. However, drug release considerably increased when MNs were exposed to wound pH conditions (pH 7.5). The present study provides proof-of-concept evidence that developed MNs have the potential of enhanced treatment protocol for wound infections with the flexibility of coating materials and antimicrobials and offers significant scope for further variations and advancement.

Hereditary hearing loss (HHL) is a common genetically heterogeneous disorder, which follows Mendelian inheritance in humans. Because of this heterogeneity, the identification of the causative gene of HHL by linkage analysis or Sanger sequencing have shown economic and temporal limitations. With recent advances in next-generation sequencing (NGS) techniques, rapid identification of a causative gene via massively parallel sequencing is now possible. We recruited a Korean family with three generations exhibiting autosomal dominant inheritance of hearing loss (HL), and the clinical information about this family revealed that there are no other symptoms accompanied with HL. To identify a causative mutation of HL in this family, we performed whole-exome sequencing of 4 family members, 3 affected and an unaffected. As the result, A novel splicing mutation, c.763+1G>T, in the solute carrier family 17, member 8 (SLC17A8) gene was identified in the patients, and the genotypes of the mutation were co-segregated with the phenotype of HL. Additionally, this mutation was not detected in 100 Koreans with normal hearing. Via NGS, we detected a novel splicing mutation that might influence the hearing ability within the patients with autosomal dominant non-syndromic HL. Our data suggests that this technique is a powerful tool to discover causative genetic factors of HL and facilitate diagnoses of the primary cause of HHL.

Clusterin (CLU) is an extracellular chaperone protein that is implicated in diverse physiological and pathophysiological cellular processes. CLU expression is upregulated in response to cellular stress and under certain conditions, such as neurodegenerative disease and cancer. CLU primarily functions as a chaperone that exerts cytoprotective effects by removing cellular debris and misfolded proteins and also acts as a signaling molecule that regulates pro-survival pathways. Deafness is caused by genetic factors and various extrinsic insults, including ototoxic drugs, exposure to loud sounds and aging. Considering its cytoprotectivity, CLU may also mediate cellular defense mechanisms against hearing loss due to cellular stresses. To understand the function of CLU in the inner ear, we analyze CLU expression patterns in the mouse inner ear during development and in the adult stage. Results of quantitative real-time polymerase chain reaction analysis showed that Clu mRNA levels in the inner ear were increased during embryogenesis and were constantly expressed in the adult. Detailed spatial expression patterns of Clu both in the mRNA and protein levels were analyzed throughout various developmental stages via in situ hybridization and immunofluorescence staining. Clu expression was found in specific domains of developing inner ear starting from the otocyst stage, mainly adjacent to the prosensory domain of the cochlear epithelium. In the mature inner ear, Clu expression was observed in Deiter's cells and pillar cells of the organ of Corti, outer sulcus and in basal cells of the stria vascularis in the cochlea. These specific spatiotemporal expression patterns suggest the possible roles of CLU in inner ear development and in maintaining proper hearing function.

Cisplatin (cis-diaminedichloridoplatinum(II), cis-[PtCl2(NH3)2]) is an effective chemotherapeutic agent in the treatment of several types of malignant solid tumors but its clinical use is associated with ototoxicity. Several studies have investigated the effect of antioxidants on cisplatin-induced ototoxicity in mice. The triazole KPR-A020 has been shown to play a protective role against mitochondrial dysfunction by reducing the production of mitochondrial reactive oxygen species (ROS). The effect of KPR-A020 on cisplatin-induced ototoxicity was examined using cultures of cochlear explants. Healthy mice were randomly divided into 4 groups: control, treated with cisplatin alone (CP), treated with cisplatin and KPR-A020 (CP + KPR-A020), and treated with KPR-A020 alone (KPR-A020). The cochlear explants were harvested for histological and immunohistochemical examinations. Biochemical analyses of the explants revealed that pre-treatment with KPR-A020 prevented an increase in mitochondrial ROS levels. Moreover, the CP + KPR-A020 group showed better hair cell survival than the CP group. Immunohistochemical examinations of cochlear explants stained with anti-caspase-3 revealed greater immunopositivity in the CP group. The CP + KPR-A020 group showed significantly less immunopositivity than the CP group (P < 0.05). Thus, it appears that KPR-A020 protects hair cells in the organ of Corti from cisplatin-induced toxicity by decreasing the production of mitochondrial ROS. The results of this study suggest that KPR-A020 can be used as an antioxidant and antiapoptotic agent to prevent hearing loss caused by cisplatin induced-oxidative stress.

Objectives We aimed to identify the causative mutation for siblings in a Korean family with nonsyndromic hearing loss (HL) and enlarged vestibular aqueduct (EVA). The siblings were a 19-year-old female with bilateral profound HL and an 11-year-old male with bilateral moderately severe HL. Methods We extracted genomic DNA from blood samples of the siblings with HL, their parents, and 100 controls. We performed mutation analysis for SLC26A4 using direct sequencing. Results The two siblings were compound heterozygotes with the novel mutation p.I713LfsX8 and the previously described mutation p.H723R. Their parents had heterozygous mono-allelic mutations. Father had p.I713LfsX8 mutation as heterozygous, and mother had p.H723R mutation as heterozygous. However, novel mutation p.I713LfsX8 was not detected in 100 unrelated controls. Conclusion Both mutations identified in this study were located in the sulfate transporter and anti-sigma factor antagonist domain, the core region for membrane targeting of SulP/SLC26 anion transporters, which strongly suggests that failure in membrane trafficking by SLC26A4 is a direct cause of HL in this family. Our study could therefore provide a foundation for further investigations elucidating the SLC26A4-related mechanisms of HL.

The mammalian inner ear is a complex organ responsible for balance and hearing. Sonic hedgehog (Shh), a member of the Hedgehog (Hh) family of secreted proteins, has been shown to play important roles in several aspects of inner ear development, including dorsoventral axial specification, cochlear elongation, tonotopic patterning, and hair cell differentiation. Hh proteins initiate a downstream signaling cascade by binding to the Patched 1 (Ptch1) receptor. Recent studies have revealed that other types of co-receptors can also mediate Hh signaling, including growth arrest-specific 1 (Gas1), cell-adhesion molecules-related/down-regulated by oncogenes (Cdon), and biregional Cdon binding protein (Boc). However, little is known about the role of these Hh co-receptors in inner ear development. In this study, we examined the expression patterns of Gas1, Cdon, and Boc, as well as that of Ptch1, in the developing mouse inner ear from otocyst (embryonic day (E) 9.5) until birth and in the developing middle ear at E15.5. Ptch1, a readout of Hh signaling, was expressed in a graded pattern in response to Shh signaling throughout development. Expression patterns of Gas1, Cdon, and Boc differed from that of Ptch1, and each Hh co-receptor was expressed in specific cells and domains in the developing inner and middle ear. These unique and differential expression patterns of Hh co-receptors suggest their roles in mediating various time- and space-specific functions of Shh during ear development.

One of most important factors for messenger RNA (mRNA) transcription is the spliceosomal component U1 small nuclear RNA (snRNA), which recognizes 5' splicing donor sites at specific regions in pre-mRNA. Mutations in these sites disrupt U1 snRNA binding and cause abnormal splicing. In this study, we investigated mutations at splice sites in SLC26A4 (HGNC 8818), one of the major causative genes of hearing loss, which may result in the synthesis of abnormal pendrin, the channel protein encoded by the gene. Seventeen SLC26A4 variants with mutations in the U1 snRNA binding sites were assessed by minigene splicing assays, and 11 were found to result in abnormal splicing. Interestingly, eight of the 11 pathogenic mutations were intronic, suggesting the importance of conserved sequences at the intronic splice site. The application of modified U1 snRNA effectively rescued the abnormal splicing for most of these mutations. Although three were cryptic mutations, they were rescued by cotransfection of modified U1 snRNA and modified antisense oligonucleotides. Our results demonstrate the important role of snRNA in SLC26A4 mutations, suggesting the therapeutic potential of modified U1 snRNA and antisense oligonucleotides for neutralizing the pathogenic effect of the splice-site mutations that may result in hearing loss.

Ototoxicity, or adverse pharmacological effects on the inner ear or auditory nerve, is a common side effect of cisplatin, a platinum-based drug widely used in anticancer chemotherapy. Although the incidence of ototoxicity is high among patients that receive cisplatin therapy, there is currently no effective treatment for it. The generation of excessive reactive oxygen species (ROS) is considered to be the major cause of cisplatin-induced ototoxicity. C-phycocyanin (C-PC), a blue phycobiliprotein found in cyanobacteria and red algae, has antioxidant and anticancer activities in different experimental models in vitro and in vivo. Thus, we tested the ability of C-PC from Limnothrix sp. KNUA002 to protect auditory cells from cisplatin-induced ototoxicity in vitro. Pretreatment with C-PC from Limnothrix sp. KNUA002 inhibited apoptosis and protected mitochondrial function by preventing ROS accumulation in cisplatin-treated House Ear Institute-Organ of Corti 1 (HEI-OC1) cells, a mouse auditory cell line. Cisplatin increased the expression of Bax and reduced the expression of Bcl-2, which activate and inhibit, respectively, the mitochondrial apoptotic pathway in response to oxidative stress. Pretreatment with C-PC prior to cisplatin treatment caused the Bax and Bcl-2 levels to stay close to the levels in untreated control cells. Our results suggest that C-PC from Limnothrix sp. KNUA002 protects cells against cisplatin-induced cytotoxicity by inhibiting the mitochondrial apoptotic pathway.

Congenital nystagmus (CN) is a heterogeneous disease that shows variable clinical features. There are a few mutations that are known to cause CN. Among them, a PAX6 mutation is known to cause CN with an extremely high frequency of aniridia. Here, we report on a family with an autosomal dominant PAX6 mutation, c.214G > A (p.Gly72Ser.), who presented with CN in the absence of aniridia. This study describes detailed clinical findings, including videonystagmography and fundus photography findings and emphasizes the importance of screening for the PAX6 gene in patients who present with CN in the absence of aniridia, as this will further elucidate the known phenotypes of PAX6-related diseases.

PurposeProper interpretation of genomic variants is critical to successful medical decision making based on genetic testing results. A fundamental prerequisite to accurate variant interpretation is the clear understanding of the clinical validity of gene-disease relationships. The Clinical Genome Resource (ClinGen) has developed a semi-quantitative framework to assign clinical validity to gene-disease relationships.MethodsThe ClinGen Hearing Loss Gene Curation Expert Panel (HL GCEP) uses this framework to perform evidence-based curations of genes present on testing panels from 17 clinical laboratories in the Genetic Testing Registry. The HL GCEP curated and reviewed 142 genes and 164 gene-disease pairs, including 105 nonsyndromic and 59 syndromic forms of hearing loss.ResultsThe final outcome included 82 Definitive (50%), 12 Strong (7%), 25 Moderate (15%), 32 Limited (20%), 10 Disputed (6%), and 3 Refuted (2%) classifications. The summary of each curation is date stamped with the HL GCEP approval, is live, and will be kept up-to-date on the ClinGen website (https://search.clinicalgenome.org/kb/gene-validity).ConclusionThis gene curation approach serves to optimize the clinical sensitivity of genetic testing while reducing the rate of uncertain or ambiguous test results caused by the interrogation of genes with insufficient evidence of a disease link.