gene therapies

2026-09-04 | POU4F3 variants are prevalent in Chinese patients with autosomal dominant non-syndromic hearing loss and concurrent tinnitus

POU4F3 (DFNA15) is an established causative gene for autosomal dominant non-syndromic hearing loss (ADNSHL); however, its mutational spectrum in the Chinese population remains incompletely characterized. This study aimed to expand the mutational spectrum of POU4F3 in the Chinese population, to characterize the clinical phenotypes of affected individuals, to describe the proportion of POU4F3 -related families in this referral cohort, and to summarize the global reporting distribution of pathogenic POU4F3 variants in ADNSHL. Among 83 unrelated ADNSHL families evaluated at two tertiary referral centers, nine families harboring POU4F3 variants were identified through whole-exome sequencing and validated by Sanger sequencing with co-segregation analysis. Comprehensive audiological assessments, including pure-tone audiometry, extended high-frequency audiometry, and tinnitus evaluation, were performed on all available family members. Variants were classified according to ACMG/AMP guidelines. Genotype–phenotype correlations were analyzed by integrating data from our cohort with 43 previously published variants. Nine distinct POU4F3 variants were identified, including four novel variants (c.149_152dup, c.687_688delCA, c.704 C > T, and c.709_710delTC) and five previously reported variants (c.371 C > A, c.592 C > A, c.706 C > T, c.952G > A, and EX1-EX2E Del). POU4F3 variants accounted for 10.8% (9/83) of families in this referral cohort, a relatively high proportion compared with those reported in selected European (6.5%), Japanese (2.5%), and Korean (2.4%) cohorts; however, direct comparisons should be interpreted cautiously because of differences in ascertainment, testing strategies, and referral settings. Among 35 confirmed variant carriers, penetrance was complete (100%). Subjective tinnitus was reported by 60.0% (21/35) of affected individuals, with 45.0% (9/20) developing tinnitus prior to measurable hearing loss (lead time range: 0–27 years). Audiometric profiling showed predominantly mid-to-high-frequency sensorineural hearing loss and an age-associated cross-sectional pattern, ranging from milder high-frequency impairment in younger individuals to severe-to-profound broadband loss in older individuals. Exploratory genotype–phenotype analysis suggested that truncating variants may be associated with earlier-onset and more severe hearing loss, whereas missense variants within core DNA-binding domains showed greater phenotypic variability. A compilation of data from the published literature ClinVar identified 82 pathogenic/likely pathogenic POU4F3 variants; 59 (72.0%) were associated with East Asian reports, although this apparent geographic concentration may partly reflect ascertainment and reporting practices. This study identifies four novel POU4F3 variants and shows that POU4F3 variants account for a relatively high proportion of ADNSHL families in this Chinese referral cohort. Consequently, these findings support prioritizing POU4F3 within ADNSHL gene panels, particularly for Chinese and East Asian populations presenting with compatible phenotypes. Furthermore, we propose a literature-informed clinical framework in which the combination of familial ADNSHL, progressive sloping sensorineural hearing loss, and accompanying tinnitus may serve as a practical clinical clue to facilitate early detection, genetic counseling, and timely intervention planning for future gene therapies; prospective validation of this framework is warranted.

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2026-05-30 | Mouse models and translational research progress of hereditary vestibular dysfunction.

BackgroundHereditary vestibular dysfunctions (HVDs) are a group of diseases caused by genetic mutations, characterized by congenital or progressive vestibular dysfunction, often accompanied by hearing loss or other systemic damages. These diseases are divided into syndromic (e.g., Usher syndrome, CHARGE syndrome) and non-syndromic types, involving mutations in key genes such as MYO7A, COCH, SLC26A4, TMC1, etc. Although clinical phenotypes vary, the pathogenesis is complex, traditional diagnostic methods are limited, and effective treatments are lacking. Mouse models are important tools for studying hereditary vestibular dysfunction, providing critical platforms for understanding disease mechanisms, developing diagnostic biomarkers, and treatment strategies.MethodsThis review systematically searched English and Chinese literature in databases including PubMed, Web of Science, Embase, and CNKI from January 2000 to April 2026. The search strategy combined Medical Subject Headings (MeSH) terms and free-text keywords, including "hereditary vestibular dysfunction," "mouse models," "gene therapy," "CRISPR-Cas9," "Usher syndrome," "translational research," "biomarkers," "Meniere disease," and "International Mouse Phenotyping Consortium." Inclusion criteria were: (1) peer-reviewed articles on hereditary vestibular dysfunction mouse models; (2) studies reporting genetic mechanisms, pathophysiology, or therapeutic interventions; and (3) English or Chinese language publications. Exclusion criteria were: (1) non-peer-reviewed conference abstracts or preprints and (2) studies without clear genetic or phenotypic characterization. Two authors independently screened titles, abstracts, and full texts, with disagreements resolved by consensus. The review focuses on analyzing the applications of spontaneous mutation models, genetic engineering models, CRISPR technology-based models, and knockout models from the International Mouse Phenotype Consortium (IMPC) in disease mechanism research and treatment development.ResultsIn recent years, significant progress has been made in hereditary vestibular dysfunction mouse model research. Spontaneous mutation models like Myo6 and Cdh23 mutant mice have revealed the key role of cytoskeletal and cell junctions in vestibular function. Genetic engineering models have successfully simulated a variety of diseases, including Usher syndrome, ion channel defects, and vestibular development abnormalities, elucidating the molecular mechanisms of TMC1/2 mechanosensory channels, SLC26A4 ion transport, and vestibular system development genes. The application of CRISPR-Cas9 technology has greatly improved model construction efficiency and precision. These models have shown positive results in gene therapy, gene editing, and drug treatment research. AAV-mediated gene replacement therapy, CRISPR gene repair, and new drugs such as α1-antitrypsin have all achieved positive outcomes in mouse models. Biomarker studies based on multi-omics techniques have identified potential diagnostic markers such as Slc17a6 and BDNF.ConclusionMouse models play an irreplaceable role in the study of hereditary vestibular dysfunction, providing a solid foundation for elucidating disease mechanisms, improving diagnostic methods, and developing treatment strategies. Although clinical translation still faces challenges such as species differences, delivery efficiency, and treatment windows, with the continuous development of gene editing technology, nano-delivery systems, and multi-omics techniques, personalized diagnosis and treatment for hereditary vestibular dysfunction are expected to be realized, bringing new hope to patients.

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2026-05-27 | Recent Progress in Mechanism-Based Therapies for GJB2-Related Hearing Loss.

GJB2-associated hearing loss is the most common form of non-syndromic hereditary deafness worldwide. However, it exhibits significant heterogeneity in terms of both clinical presentation and biological basis. This review focuses on mechanism-oriented therapeutic strategies for GJB2-associated hearing loss, investigating how different types of GJB2 variants correspond to distinct clinical phenotypes and underlying pathogenic mechanisms, and aims to determine appropriate treatments. Current evidence suggests that GJB2-associated hearing loss is not solely caused by channel dysfunction resulting from gap junction defects, but rather the result of multiple pathological processes, including impaired GJB2 transcriptional regulation, cochlear developmental abnormalities, sensory epithelial degeneration and secondary damage pathways such as inflammation. Consequently, emerging therapeutic approaches can be viewed as interventions targeting specific mechanisms, including gene therapy, restoration of protein transport and pharmacological modulation of damage to the cochlear microenvironment. Overall, this review highlights the importance of aligning therapeutic strategies with specific GJB2 variants, underlying pathogenic mechanisms, and the developmental window during which cochlear injury remains biologically reversible.

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2026-05-04 | Population-Specific Mutational Spectrum of Autosomal Recessive Nonsyndromic Hearing Loss in Croatian Roma: Implications for Clinical Genetics.

Hearing impairment is a highly prevalent sensory disorder resulting from a variety of causes. A high proportion of autosomal recessive non-syndromic hearing impairment is linked to the GJB2 (OMIM 121011) gene which encodes for a gap junction protein, connexin-26. Alterations of genes that encode for connexins can lead to changes in cell ion content and cause hearing impairment. GJB2 gene polymorphisms (c.71G>A, p.Trp24*rs104894396; c.457G>A, p.Val153Ile, rs111033186; c.380G>A, p.Arg127His, rs111033196; c.109G>A, p.Val37Ile, rs72474224; and c.269T>C, p.Leu90Pro, rs80338945) were analyzed in the Roma population of Croatia. Loci were genotyped using the KASP method. Altered alleles were detected on the loci c.71G>A, c.457G>A and c.380G>A and statistically significant differences in allele frequencies were noticed. Furthermore, in comparison to worldwide populations, the Roma population also shows statistically significant difference in allele frequency of these loci. This study reveals marked genetic differentiation among Croatian Roma particularly with respect to the c.71G>A variant. Characterizing such population-specific mutational heterogeneity is crucial for the accurate prevention, diagnosis, and clinical management of autosomal recessive nonsyndromic hearing loss.

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2026-04-19 | Gene editing of the GJB2 locus in porcine embryos using CRISPR/Cas9 and cytosine base editors: toward a model of congenital deafness.

Mutations in the GJB2 gene, which encodes Connexin 26 (Cx26), are responsible for the majority of cases of non-syndromic congenital hearing loss in humans. While murine GJB2 knockout models have provided mechanistic insight, anatomical and physiological differences limit their translational relevance. Pigs represent a valuable large-animal model because their auditory anatomy and maturation closely resemble those of humans. This study compared two genome-editing approaches to disrupt GJB2 in porcine oocytes before fertilization: (1) electroporation with CRISPR/Cas9 ribonucleoprotein and (2) microinjection with cytosine base editor (BE3) and single-guide RNAs (sgRNAs). Electroporation produced high mutation rates (70–90%) across three concentrations of Cas9/sgRNA but yielded mostly heterozygous or mosaic blastocysts, with limited homozygous knockouts (< 4%). BE3 achieved precise cytosine-to-thymine conversions that introduced premature stop codons, reaching up to 47% total editing and 20% homozygous nonsense alleles. However, blastocyst formation declined at higher component concentrations. Overall, BE3 produced more predictable mutations than conventional CRISPR/Cas9, although embryo developmental competence was dose-dependent. Both methods effectively targeted GJB2 and demonstrated feasibility of pre-fertilization genome editing in porcine oocytes. These findings establish the groundwork for generating GJB2-deficient pigs as translational models of Cx26-related congenital deafness and for future evaluation of gene-therapy strategies in a large-animal system.

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small molecules

2026-09-09 | Case Report: Persistent isolated hyperhomocysteinemia in an adolescent with celiac disease and homozygous MTHFR c.665C>T polymorphism: a multifactorial disturbance of one-carbon metabolism.

Hyperhomocysteinemia in adolescence typically prompts investigation for classical inborn errors of sulfur amino acid metabolism, including cystathionine β-synthase deficiency and cobalamin-dependent remethylation disorders. However, persistent elevations may also arise from interactions between common genetic polymorphisms and acquired nutritional conditions that alter one-carbon metabolism. We report an 18-year-old male with type 1 diabetes mellitus, celiac disease on a strict gluten-free diet, congenital unilateral sensorineural hearing loss, and persistent isolated hyperhomocysteinemia. At age 16, he presented with an acute visual field disturbance and right occipital cortical MRI changes suggestive of ischemia. Plasma homocysteine was persistently between 50 and 65 μmol/L.Extensive metabolic and genetic investigations, including targeted gene panels, whole-exome and research whole-genome sequencing, mitochondrial DNA sequencing, mitochondrial complex activities in fibroblasts, and fibroblast complementation, excluded classical homocystinuria and remethylation defects. Sequential trials of pyridoxine, hydroxocobalamin, and high-dose betaine produced modest or transient improvement. Re-analysis of exome data showed homozygosity for the common MTHFR c.665C>T (p.Ala222Val) variant. Family testing revealed that his father (TT) and mother (CT) had normal homocysteine (10.9 and 10.4 μmol/L), indicating that MTHFR TT alone is insufficient to cause a biochemical phenotype and functions as a susceptibility factor. Combined oral methylfolate (1,000 µg daily) and vitamin B12 (cyanocobalamin 1,000 µg daily) reduced homocysteine from 66 to 24.6 μmol/L in 8 weeks. This case illustrates multifactorial hyperhomocysteinemia arising from interactions between celiac disease-related micronutrient vulnerability and reduced MTHFR activity. Recognition of gene-nutrient interactions is important when classical metabolic disorders are excluded and may guide targeted therapy.

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2026-08-14 | The ZBTB16/CUL3/ROC1 ubiquitin ligase drives the degradation of pathogenic pendrin (SLC26A4) protein variants.

Pathogenic sequence alterations in the SLC26A4 gene, which encodes the solute carrier SLC26A4/pendrin, lead to Pendred syndrome and non-syndromic autosomal recessive deafness type B4 (DFNB4), two of the most common forms of hearing loss worldwide. Many pathogenic SLC26A4 protein variants exhibit reduced cellular levels due to ubiquitin-proteasome system (UPS)-mediated degradation, and UPS inhibition rescues their plasma membrane expression and ion transport function. However, the underlying molecular mechanisms remain unclear and may involve interactions with novel molecular partners. A candidate SLC26A4 protein partner was found by a yeast two-hybrid screening. The biological significance of this interaction has been studied by immunohistochemistry and co-localization in the mouse inner ear and kidney, co-immunoprecipitation of endogenous and recombinant proteins, Liquid Chromatography-Tandem Mass Spectrometry, and Fluorescence Resonance Energy Transfer. We identified the zinc finger and BTB domain-containing protein ZBTB16 as a novel SLC26A4-interacting partner. ZBTB16 co-localized with SLC26A4 in the outer sulcus and spiral prominence epithelial cells of the mouse cochlea and in the apical membrane of non-alpha non-beta intercalated cells of the distal nephron. ZBTB16 was found to be part of a ubiquitin-ligase complex comprising the scaffold protein Cullin 3 and the ubiquitin ligase RocI, and to bind with its C-terminal zinc finger region a unique amino acid sequence within the C-terminal Sulfate Transporter and Anti-Sigma factor Antagonist (STAS) domain of SLC26A4. This direct molecular interaction leads to increased site- and variant-specific ubiquitination and accelerated degradation of SLC26A4. Finally, using AI-based structure prediction, we provide an atomistic model of the complete SLC26A4/ZBTB16/Cullin 3/RocI complex in agreement with our experimental results. These findings describe a primary mechanism of SLC26A4 regulation in the inner ear and kidney and of SLC26A4 loss of function in Pendred syndrome and deafness DFNB4, and identify potential novel molecular targets for therapeutic intervention.

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2026-06-09 | Quinazoline alleviates inner ear damage by enhancing the proliferation and differentiation of neural stem cells.

Neural stem cell (NSC) transplantation exerts therapeutic effects on inner ear damage and pretreatment with quinazoline compounds may further enhance this efficacy. This study aimed to investigate whether quinazoline alleviates inner ear damage by enhancing the proliferation and differentiation of NSCs. Forty Hartley guinea pigs were randomly assigned to four groups. Hippocampal NSCs isolated from neonatal guinea pigs were pretreated with quinazoline and transplanted into animals with cisplatin-induced hearing loss. Evaluations included NSC proliferation and differentiation, auditory brainstem response (ABR) thresholds and miR-183 expression in cochlear tissues. Quinazoline pretreatment significantly enhanced NSC proliferation and differentiation (P<0.05). After transplantation, the group receiving quinazoline-pretreated NSCs showed a significantly lower ABR threshold (reflecting an approximately 10 dB improvement in hearing recovery) than the group receiving untreated NSCs (P<0.05). This was accompanied by more pronounced structural repair of the cochlea and a significant upregulation of miR-183 expression (P<0.05). Quinazoline promotes the repair of inner ear injury by enhancing the proliferation and differentiation of NSCs, a mechanism that appears to be associated with the upregulation of miR-183 expression.

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2026-05-27 | OSBPL2 deficiency impaired autophagy and induced apoptosis in auditory cells via AMPK-TFEB signalling pathway.

OSBPL2 was identified as a causal gene responsible for autosomal dominant non-syndromic hearing loss. Previous study revealed that OSBPL2-mediated AMPK signalling was crucial for cholesterol-homeostasis in inner ear. AMPK is the downstream component of a kinase cascade as the key regulator of autophagy, metabolism, cell growth and apoptosis, etc. In addition, OSBPL2 deficiency could lead to autophagy impairment in auditory cells, indicating the potential role of OSBPL2-mediated AMPK signalling in autophagy. In the present study, autophagy function was characterized in hair cells (HCs) of Osbpl2-knockout mice and in Osbpl2-knockdown HEI-OC1 cells. The results showed that OSBPL2 deficiency impaired autophagy by inhibiting AMPK-TFEB signalling, resulting in aberrant accumulation of lipid droplets and apoptosis in auditory cells, which could be partially reversed by trehalose treatment. This study revealed the implications of OSBPL2 for autophagy in auditory cell and contributed to elucidating the pathogenesis of OSBPL2 mutations in hearing loss.

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2026-02-13 | Myosin 7a is required for maintaining the transducing stereocilia and for force transmission to the MET channel during cochlear hair cell development.

Shaker-1 mice carry a spontaneous missense mutation in Myo7a (Myo7aSh1) that interferes with the motor function of MYO7A. Mutation in the orthologous gene in humans causes syndromic (Usher 1B) or non-syndromic forms of deafness. In hair cells, MYO7A is expressed throughout the stereocilia, where it has been implicated in tip-link tensioning required for gating the mechanoelectrical transducer (MET) channel and setting its resting open probability (Po). The Myo7aSh1 mutation progressively dysregulated the height of shorter stereocilia rows from the end of the first postnatal week onwards, associated with reduced MET current amplitude and hearing loss. Noise exposure exacerbated stereocilia dysfunction in Myo7aSh1/Sh1 mice. Following the onset of maturation, hair cells from Myo7aSh1/Sh1 mice showed normal resting Po and calcium sensitivity of the MET channel. In immature Myo7aSh1/Sh1 hair cells, the resting Po was very small or absent in comparison to control cells, but it was restored by changing the membrane lipid bilayer fluidity or thickness by depleting cholesterol or PIP2. Bundle stiffness in immature IHCs was not affected by the absence of functional MYO7A but decreased after their onset of maturation in both genotypes. Expression of a subset of genes was affected similarly in immature Myo7aSh1/Sh1 mice and in adult Myo7a conditional knockout mice, indicating a common response pathway in Myo7a-deficient mice. This study reveals that MET channel gating might differ depending on hair cell developmental stage, and MYO7A is likely to influence, albeit indirectly, force transmission via the lipid bilayer to the MET channel and maintenance of the shorter rows of transducing stereocilia. KEY POINTS: Shaker-1 mice carry a spontaneous missense mutation in the shaker-1 gene (Myo7aSh1) that interferes with the motor function of MYO7A, a protein expressed in hair-cell stereocilia. The absence of functional MYO7A (Myo7aSh1/Sh1 mice) caused a progressive dysregulation in the height of the shortest two rows of stereocilia and the consequent loss of mechanoelectrical transduction (MET) current. Although immature hair cells from Myo7aSh1/Sh1 mice exhibited a markedly reduced resting open probability of their MET channels, this was restored upon maturation or following depletion of cholesterol or PIP2 from the lipid bilayer. Hair-bundle stiffness was affected in immature inner hair cells from Myo7aSh1/Sh1 mice, suggesting that MYO7A is not required for establishing the resting tension of the tip links gating the MET channels. We conclude that MYO7A is crucial for the structural integrity of the MET complex and transport of key proteins required to transfer forces efficiently from the lipid bilayer to the MET channel.

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proteins

2026-06-04 | Tonotopic specialization of MYO7A isoforms in auditory hair cells.

Mutations in Myo7a cause Usher syndrome type 1B and non-syndromic deafness, but the precise function of MYO7A in sensory hair cells remains unclear. Using long-read sequencing, we identify and characterize a novel isoform, MYO7A-N, expressed in auditory hair cells alongside the canonical MYO7A-C. Isoform-specific knock-in mouse models reveal that inner hair cells primarily express MYO7A-C, while outer hair cells express both isoforms in opposing tonotopic gradients. Both isoforms are localized to the upper tip-link insertion site, consistent with a role in the tip link for mechanotransduction. Loss of MYO7A-N leads to outer hair cell degeneration and progressive hearing loss. Cryo-EM structures reveal isoform-specific differences at actomyosin interfaces, correlating with distinct ATPase activities. These findings reveal an unexpected layer of molecular diversity within the mechanotransduction machinery. We propose that MYO7A isoform specialization enables fine-tuning of tip-link tension, thus hearing sensitivity, and contributes to the frequency-resolving power of the cochlea.

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2024-08-05 | A human-specific cytotoxic neopeptide generated by the deafness gene Cingulin.

Accumulation of mutant proteins in cells can induce proteinopathies and cause functional damage to organs. Recently, the Cingulin (CGN) protein has been shown to maintain the morphology of cuticular plates of inner ear hair cells and a frameshift mutation in CGN causes autosomal dominant non-syndromic hearing loss. Here, we find that the mutant CGN proteins form insoluble aggregates which accumulate intracellularly and lead to cell death. Expression of the mutant CGN in the inner ear results in severe hair cell death and hearing loss in mice, resembling the auditory phenotype in human patients. Interestingly, a human-specific residue (V1112) in the neopeptide generated by the frameshift mutation is critical for the aggregation and cytotoxicity of the mutant human CGN. Moreover, the expression of heat shock factor 1 (HSF1) decreases the accumulation of insoluble mutant CGN aggregates and rescues cell death. In summary, these findings identify mutant-specific toxic polypeptides as a disease-causing mechanism of the deafness mutation in CGN, which can be targeted by the expression of the cell chaperone response regulator HSF1.

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2024-06-05 | Genetic heterogeneity in hereditary hearing loss: Potential role of kinociliary protein TOGARAM2.

Hearing loss (HL) is a heterogenous trait with pathogenic variants in more than 200 genes that have been discovered in studies involving small and large HL families. Over one-third of families with hereditary HL remain etiologically undiagnosed after screening for mutations in the recognized genes. Genetic heterogeneity complicates the analysis in multiplex families where variants in more than one gene can be causal in different individuals even in the same sibship. We employed exome or genome sequencing in at least two affected individuals with congenital or prelingual-onset, severe to profound, non-syndromic, bilateral sensorineural HL from four multiplex families. Bioinformatic analysis was performed to identify variants in known and candidate deafness genes. Our results show that in these four families, variants in a single HL gene do not explain HL in all affected family members, and variants in another known or candidate HL gene were detected to clarify HL in the entire family. We also present a variant in TOGARAM2 as a potential cause underlying autosomal recessive non-syndromic HL by showing its presence in a family with HL, its expression in the cochlea and the localization of the protein to cochlear hair cells. Conclusively, analyzing all affected family members separately can serve as a good source for the identification of variants in known and novel candidate genes for HL.

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2024-02-07 | The dynamics of actin protrusions can be controlled by tip-localized myosin motors.

Class III myosins localize to inner ear hair cell stereocilia and are thought to be crucial for stereocilia length regulation. Mutations within the motor domain of MYO3A that disrupt its intrinsic motor properties have been associated with non-syndromic hearing loss, suggesting that the motor properties of MYO3A are critical for its function within stereocilia. In this study, we investigated the impact of a MYO3A hearing loss mutation, H442N, using both in vitro motor assays and cell biological studies. Our results demonstrate the mutation causes a dramatic increase in intrinsic motor properties, actin-activated ATPase and in vitro actin gliding velocity, as well as an increase in actin protrusion extension velocity. We propose that both "gain of function" and "loss of function" mutations in MYO3A can impair stereocilia length regulation, which is crucial for stereocilia formation during development and normal hearing. Furthermore, we generated chimeric MYO3A constructs that replace the MYO3A motor and neck domain with the motor and neck domain of other myosins. We found that duty ratio, fraction of ATPase cycle myosin is strongly bound to actin, is a critical motor property that dictates the ability to tip localize within filopodia. In addition, in vitro actin gliding velocities correlated extremely well with filopodial extension velocities over a wide range of gliding and extension velocities. Taken together, our data suggest a model in which tip-localized myosin motors exert force that slides the membrane tip-ward, which can combat membrane tension and enhance the actin polymerization rate that ultimately drives protrusion elongation.

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2021-02-03 | Exosomes mediate sensory hair cell protection in the inner ear.

Hair cells, the mechanosensory receptors of the inner ear, are responsible for hearing and balance. Hair cell death and consequent hearing loss are common results of treatment with ototoxic drugs, including the widely used aminoglycoside antibiotics. Induction of heat shock proteins (HSPs) confers protection against aminoglycoside-induced hair cell death via paracrine signaling that requires extracellular heat shock 70-kDa protein (HSP70). We investigated the mechanisms underlying this non-cell-autonomous protective signaling in the inner ear. In response to heat stress, inner ear tissue releases exosomes that carry HSP70 in addition to canonical exosome markers and other proteins. Isolated exosomes from heat-shocked utricles were sufficient to improve survival of hair cells exposed to the aminoglycoside antibiotic neomycin, whereas inhibition or depletion of exosomes from the extracellular environment abolished the protective effect of heat shock. Hair cell-specific expression of the known HSP70 receptor TLR4 was required for the protective effect of exosomes, and exosomal HSP70 interacted with TLR4 on hair cells. Our results indicate that exosomes are a previously undescribed mechanism of intercellular communication in the inner ear that can mediate nonautonomous hair cell survival. Exosomes may hold potential as nanocarriers for delivery of therapeutics against hearing loss.

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cell therapies

2025-06-04 | A novel BCAP31 variant associated with nonsyndromic auditory neuropathy spectrum disorder: mitochondrial dysfunction, cisplatin sensitivity, and amenability to mitochondrial transplantation.

A novel in-frame insertion variant in the B-Cell Receptor-Associated Protein 31 (BCAP31) gene, which encodes a crucial ER membrane protein involved in the quality control and transport of transmembrane proteins, as well as in ER-mitochondria apoptotic signaling, was determined in a family demonstrating X-linked, recessive, nonsyndromic auditory neuropathy spectrum disorder (ANSD). Exome sequencing analysiswas followed by bioinformatics analysis to identify the cause of hearing loss in a family whose pedigree indicated an X-linked recessive mode of inheritance. Immunohistochemistry was performed to locate Bcap31 in the mouse cochlea. Mitochondrial function was evaluated by measuring intracellular ATP, ROS and mitochondrial membrane potential in control and patient-derived lymphoblastoid cells (LCLs) before and after the administration of mitochondria isolated from human umbilical cord mesenchymal stem cells (UC-MSCs). ANSD observed in our study is characterized by initial inner hair cell damage, followed by accelerated degeneration of cochlear outer hair cells. Functional studies of patient-derived LCLs revealed mitochondrial dysfunction, evidenced by increased ROS, reduced ATP levels, and decreased mitochondrial membrane potential compared with normal LCLs. Further, these cells demonstrated heightened sensitivity to cisplatin-induced apoptosis, as indicated by the increased proapoptotic gene expression. Notably, the administration of mitochondria isolated from umbilical cord mesenchymal stem cells significantly restored mitochondrial dysfunction and alleviated cisplatin-induced cytotoxicity in the patient-derived cells. These results indicate BCAP31 dysfunction as a potential cause of transient ANSD, progressing to sensorineural hearing loss through mitochondrial impairment. Furthermore, they highlighted the therapeutic potential of allogenic mitochondrial transplantation as a novel strategy for treating hearing loss with an underlying component of mitochondrial dysfunction. This study contributes to the understanding of BCAP31's role in auditory neuropathy and mitochondrial health.

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2025-03-07 | Characteristics and Prognosis of Patients With Non-Syndromic Sensorineural Hearing Loss Associated With Myo15a Mutations.

This study aims to investigate the characteristics of hearing loss associated with MYO15A mutations and to analyze the longitudinal prognosis over a 4-year period using different treatment modalities, including cochlear implants (CIs), hearing aids (HAs), and conservative management. A retrospective case review. A tertiary referral center. Sequencing was performed to recruit patients with potentially pathogenic MYO15A mutation-induced hearing loss. Audiological data, radiological imaging, and assessment of hearing and speech performance before and after different treatments were analyzed in combination with patients' genotypes. Sixteen patients with MYO15A mutation-induced deafness from 14 unrelated pedigrees were enrolled, carrying 5 previously unreported mutations: c.3660_3666delinsAA (p.Glu1221fs), c.4635delG (p.Val1545fs), c.6664A>G (p.Met2222Val), c.8215delG (p.Ala2739fs), and c.8897delG (p.Gly2966fs). Inner ear malformations were observed in 3 patients. CI recipients exhibited significant improvements in hearing and speech abilities 1-year post-implantation, while individuals using HAs showed a gradual improvement trend over a 4-year period. Notably, even those with bilateral cochlear aperture atresia achieved satisfactory hearing and speech outcomes following early CIs. Patients with MYO15A mutations who underwent CIs generally demonstrated earlier improvements in hearing and speech development compared to those using HAs. Early genetic detection and timely implementation of assistive acoustic stimulation are recommended for optimal outcomes.

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2024-09-13 | Hearing loss secondary to variants in the OTOF gene.

Genetic variants in the OTOF gene are responsible for non-syndromic hearing loss with an autosomal recessive inheritance pattern. The objective of our work was to evaluate the clinical characteristics of patients with biallelic pathogenic variants in OTOF and their evolution after treatment. A cohort of 124 patients with prelingual hearing loss, studied from 1996 to 2023, was included in this study. A genetic analysis was conducted to identify the type and frequency of variants in the OTOF gene and their relation to the clinical characteristics of the patients. The homozygous p. Gln829* variant in the OTOF gene was detected in 3 probands (2.4 %) of a group of 124 individuals with prelingual hearing loss. Another 6 family members to a total of 9 individuals were finally included. All presented with severe/profound bilateral sensorineural hearing loss of congenital onset. Three of these individuals were diagnosed with auditory neuropathy spectrum disorder. One individual passed the OAE test during the screening program, and since he did not have risk factors for hearing loss that would warrant ABR testing, this led to a delay in his hearing loss diagnosis. Four individuals underwent cochlear implants (three bilateral) with good functional outcomes in three of them. However, in 17 familial cases with heterozygous variants, either no hearing loss was observed or it was within the expected range for their age. Hearing loss secondary to the p.Gln829* variant of the OTOF gene is relatively rare in our medical area. Its presence in homozygosity is the cause of severe/profound bilateral prelingual sensorineural hearing loss, responsible for auditory neuropathy with a good response to cochlear implantation.

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2024-04-27 | Detailed Clinical Features of PTPRQ-Associated Hearing Loss Identified in a Large Japanese Hearing Loss Cohort.

The PTPRQ gene has been identified as one of the genes responsible for non-syndromic sensorineural hearing loss (SNHL), and assigned as DFNA73 and DFNB84. To date, about 30 causative PTPRQ variants have been reported to cause SNHL. However, the detailed clinical features of PTPRQ-associated hearing loss (HL) remain unclear. In this study, 15,684 patients with SNHL were enrolled and genetic analysis was performed using massively parallel DNA sequencing (MPS) for 63 target deafness genes. We identified 17 possibly disease-causing PTPRQ variants in 13 Japanese patients, with 15 of the 17 variants regarded as novel. The majority of variants identified in this study were loss of function. Patients with PTPRQ-associated HL mostly showed congenital or childhood onset. Their hearing levels at high frequency deteriorated earlier than that at low frequency. The severity of HL progressed from moderate to severe or profound HL. Five patients with profound or severe HL received cochlear implantation, and the postoperative sound field threshold levels and discrimination scores were favorable. These findings will contribute to a greater understanding of the clinical features of PTPRQ-associated HL and may be relevant in clinical practice.

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2023-06-30 | Defining developmental trajectories of prosensory cells in human inner ear organoids at single-cell resolution.

The inner ear sensory epithelia contain mechanosensitive hair cells and supporting cells. Both cell types arise from SOX2-expressing prosensory cells, but the mechanisms underlying the diversification of these cell lineages remain unclear. To determine the transcriptional trajectory of prosensory cells, we established a SOX2-2A-ntdTomato human embryonic stem cell line using CRISPR/Cas9, and performed single-cell RNA-sequencing analyses with SOX2-positive cells isolated from inner ear organoids at various time points between differentiation days 20 and 60. Our pseudotime analysis suggests that vestibular type II hair cells arise primarily from supporting cells, rather than bi-fated prosensory cells in organoids. Moreover, ion channel- and ion-transporter-related gene sets were enriched in supporting cells versus prosensory cells, whereas Wnt signaling-related gene sets were enriched in hair cells versus supporting cells. These findings provide valuable insights into how prosensory cells give rise to hair cells and supporting cells during human inner ear development, and may provide a clue to promote hair cell regeneration from resident supporting cells in individuals with hearing loss or balance disorders.

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2026-07-20 | Patient-Derived Inner Ear Organoids as a Disease Modeling and Therapy Validation Platform For Hereditary Inner Ear Disorders

Abstract Background Hereditary inner ear disorders comprise a highly heterogenous group of disorders and are a major cause of hearing and vestibular dysfunction. Despite advances in genetic diagnosis, the development of precision therapies has been limited by the lack of relevant and scalable human model systems that can accommodate the wide spectrum of disease-causing variants and support the evaluation of therapeutic interventions. We established patient-derived inner ear organoids (IEOs) as a platform to assess antisense oligonucleotide (ASO)-based therapeutic strategies for hereditary hearing loss. Methods Two representative genetic models were selected: recessive syndromic Usher syndrome type IIa ( USH2A ) and dominant non-syndromic DFNA9 ( COCH ). Human induced pluripotent stem cells (iPSCs) were generated from a patient carrying a homozygous pathogenic USH2A variant and a patient carrying a frequently occurring pathogenic COCH variant. In parallel, isogenic iPSC lines were created by introducing the same disease-causing variants into a healthy donor background. Following differentiation into IEOs, disease-associated transcript expression was evaluated. Splice-switching and RNase H1-mediated gapmer ASOs were assessed for target engagement. ASO biodistribution and cellular uptake was also examined in both IEOs and adult human vestibular tissue. Results Patient-derived and isogenic iPSCs were successfully differentiated into IEOs that recapitulated disease-associated transcript expression. ASOs showed efficient uptake into disease-relevant cell populations in both IEOs and adult human vestibular tissue. In USH2A -variant IEOs, splice-switching ASO treatment corrected aberrant splicing. In COCH -variant IEOs, gapmer ASO treatment reduced total COCH transcript levels, achieving up to 75% knockdown in patient-derived IEOs. Conclusions Patient-derived and isogenic variant IEOs provide a versatile and scalable human platform for evaluating ASO therapies for hereditary hearing loss. Their adaptability to diverse genetic variants, inheritance patterns, and ASO modalities makes them well suited to address the genetic heterogeneity of hereditary inner ear diseases and establishes IEOs as a broadly applicable preclinical model for rare hereditary inner ear diseases.

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2023-02-24 | A novel recessive mutation in OXR1 is identified in patient with hearing loss recapitulated by the knockdown zebrafish.

Hereditary hearing loss is a highly genetically heterogeneous disorder. More than 150 genes have been identified to link to human non-syndromic hearing impairment. To identify genetic mutations and underlying molecular mechanisms in affected individuals and families with congenital hearing loss, we recruited a cohort of 389 affected individuals in 354 families for whole-exome sequencing analysis. In this study, we report a novel homozygous missense variant (c.233A > G, p.Lys78Arg) in the OXR1 gene, which was identified in a 4-year-old girl with sensorineural hearing loss. OXR1 encodes Oxidation Resistance 1 and is evolutionarily conserved from zebrafish to human. We found that the ortholog oxr1b gene is expressed in the statoacoustic ganglion (SAG, a sensory ganglion of ear) and posterior lateral line ganglion (pLL) in zebrafish. Knockdown of oxr1b in zebrafish resulted in a significant developmental defect of SAG and pLL. This phenotype can be rescued by co-injection of wild-type human OXR1 mRNAs, but not mutant OXR1 (c.233A > G) mRNAs. OXR1-associated pathway analysis revealed that mutations of TBC1D24, a TLDc-domain-containing homolog gene of OXR1, have previously been identified in patients with hearing loss. Interestingly, mutations or knockout of OXR1 interacting molecules such as ATP6V1B1 and ESR1 are also associated with hearing loss in patients or animal models, hinting an important role of OXR1 and associated partners in cochlear development and hearing function.

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2023-01-04 | Analysis of Serum Inflammatory Markers in Infants Under 6 Months of Age with Non-Syndromic Moderate and Severe Hearing Loss Associated with GJB2 Gene Mutations.

BACKGROUND The GJB2 gene is reported to be the main hereditary factor responsible for non-syndromic hearing impairment in infants. Several kinds of hearing loss have been linked to elevated inflammatory markers. This study aimed to evaluate serum levels of IL-2, IL-4, IL-6, IL-10, IL-17, alpha-TNF, and γ-IFN and the severity of hearing loss. MATERIAL AND METHODS Ninety newborns were divided into 3 groups: severe hearing impairment (31 infants), moderate hearing impairment (30 infants), and normal hearing (29 infants). Hearing screening was performed using otoacoustic emissions test. Mutations of the GJB2 gene were detected with Sanger sequencing. The patients had DNFB1 mutation. Seven blood inflammatory markers were tested using Cytometric Bead Array. We performed the t test to examine differences in expression of 7 inflammatory markers between sexes in the groups. The correlation between indicators within groups was studied using the Pearson correlation test. Correlation of different indicators among groups was studied using the Spearman correlation test. RESULTS When compared among the 3 groups (severe, moderate hearing impairment, and normal hearing group), we found that IL-10 had a positive correlation with the severity of GJB2-associated hearing loss, which was statistically significant (P<0.05). CONCLUSIONS This research aimed to assess the relationship of 7 serum inflammatory markers with GJB2-associated hearing loss in infants. Inflammatory marker IL-10 had a positive correlation with the severity of GJB2-associated infant hearing loss, and it might have the potential to become a future therapeutic target.

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2021-11-22 | Loss of miR-183/96 Alters Synaptic Strength via Presynaptic and Postsynaptic Mechanisms at a Central Synapse.

A point mutation in miR-96 causes non-syndromic progressive peripheral hearing loss and alters structure and physiology of the central auditory system. To gain further insight into the functions of microRNAs (miRNAs) within the central auditory system, we investigated constitutive Mir-183/96dko mice of both sexes. In this mouse model, the genomically clustered miR-183 and miR-96 are constitutively deleted. It shows significantly and specifically reduced volumes of auditory hindbrain nuclei, because of decreases in cell number and soma size. Electrophysiological analysis of the calyx of Held synapse in the medial nucleus of the trapezoid body (MNTB) demonstrated strongly altered synaptic transmission in young-adult mice. We observed an increase in quantal content and readily releasable vesicle pool size in the presynapse while the overall morphology of the calyx was unchanged. Detailed analysis of the active zones (AZs) revealed differences in its molecular composition and synaptic vesicle (SV) distribution. Postsynaptically, altered clustering and increased synaptic abundancy of the AMPA receptor subunit GluA1 was observed resulting in an increase in quantal amplitude. Together, these presynaptic and postsynaptic alterations led to a 2-fold increase of the evoked excitatory postsynaptic currents in MNTB neurons. None of these changes were observed in deaf Cldn14ko mice, confirming an on-site role of miR-183 and miR-96 in the auditory hindbrain. Our data suggest that the Mir-183/96 cluster plays a key role for proper synaptic transmission at the calyx of Held and for the development of the auditory hindbrain.SIGNIFICANCE STATEMENT The calyx of Held is the outstanding model system to study basic synaptic physiology. Yet, genetic factors driving its morphologic and functional maturation are largely unknown. Here, we identify the Mir-183/96 cluster as an important factor to regulate its synaptic strength. Presynaptically, Mir-183/96dko calyces show an increase in release-ready synaptic vesicles (SVs), quantal content and abundance of the proteins Bassoon and Piccolo. Postsynaptically, the quantal size as well as number and size of GluA1 puncta were increased. The two microRNAs (miRNAs) are thus attractive candidates for regulation of synaptic maturation and long-term adaptations to sound levels. Moreover, the different phenotypic outcomes of different types of mutations in the Mir-183 cluster corroborate the requirement of mutation-tailored therapies in patients with hearing loss.

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2019-12-02 | The microRNA-183/96/182 Cluster is Essential for Stereociliary Bundle Formation and Function of Cochlear Sensory Hair Cells.

The microRNA (miR)-183/96/182 cluster plays important roles in the development and functions of sensory organs, including the inner ear. Point-mutations in the seed sequence of miR-96 result in non-syndromic hearing loss in both mice and humans. However, the lack of a functionally null mutant has hampered the evaluation of the cluster's physiological functions. Here we have characterized a loss-of-function mutant mouse model (miR-183CGT/GT), in which the miR-183/96/182 cluster gene is inactivated by a gene-trap (GT) construct. The homozygous mutant mice show profound congenital hearing loss with severe defects in cochlear hair cell (HC) maturation, alignment, hair bundle formation and the checkboard-like pattern of the cochlear sensory epithelia. The stereociliary bundles retain an immature appearance throughout the cochlea at postnatal day (P) 3 and degenerate soon after. The organ of Corti of mutant newborn mice has no functional mechanoelectrical transduction. Several predicted target genes of the miR-183/96/182 cluster that are known to play important roles in HC development and function, including Clic5, Rdx, Ezr, Rac1, Myo1c, Pvrl3 and Sox2, are upregulated in the cochlea. These results suggest that the miR-183/96/182 cluster is essential for stereociliary bundle formation, morphogenesis and function of the cochlear HCs.

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