Class III myosins shape the auditory hair bundles by limiting microvilli and stereocilia growth.

International audienceThe precise architecture of hair bundles, the arrays of mechanosensitive microvilli-like stereocilia crowning the auditory hair cells, is essential to hearing. Myosin IIIa, defective in the late-onset deafness form DFNB30, has been proposed to transport espin-1 to the tips of stereocilia, thereby promoting their elongation. We show that Myo3a(-/-)Myo3b(-/-) mice lacking myosin IIIa and myosin IIIb are profoundly deaf, whereas Myo3a-cKO Myo3b(-/-) mice lacking myosin IIIb and losing myosin IIIa postnatally have normal hearing. Myo3a(-/-)Myo3b(-/-) cochlear hair bundles display robust mechanoelectrical transduction currents with normal kinetics but show severe embryonic abnormalities whose features rapidly change. These include abnormally tall and numerous microvilli or stereocilia, ungraded stereocilia bundles, and bundle rounding and closure. Surprisingly, espin-1 is properly targeted to Myo3a(-/-)Myo3b(-/-) stereocilia tips. Our results uncover the critical role that class III myosins play redundantly in hair-bundle morphogenesis; they unexpectedly limit the elongation of stereocilia and of subsequently regressing microvilli, thus contributing to the early hair bundle shaping

Hypervulnerability to Sound Exposure through Impaired Adaptive Proliferation of Peroxisomes

A deficiency in pejvakin, a protein of unknown function, causes a strikingly heterogeneous form of human deafness. Pejvakin-deficient (Pjvk(-/-)) mice also exhibit variable auditory phenotypes. Correlation between their hearing thresholds and the number of pups per cage suggest a possible harmful effect of pup vocalizations. Direct sound or electrical stimulation show that the cochlear sensory hair cells and auditory pathway neurons of Pjvk(-/-) mice and patients are exceptionally vulnerable to sound. Subcellular analysis revealed that pejvakin is associated with peroxisomes and required for their oxidative-stress-induced proliferation. Pjvk(-/-) cochleas display features of marked oxidative stress and impaired antioxidant defenses, and peroxisomes in Pjvk(-/-) hair cells show structural abnormalities after the onset of hearing. Noise exposure rapidly upregulates Pjvk cochlear transcription in wild-type mice and triggers peroxisome proliferation in hair cells and primary auditory neurons. Our results reveal that the antioxidant activity of peroxisomes protects the auditory system against noise-induced damage

Combination of pejvakin and LC3B for treating hearing losses

publication date: 2020-05-28; filing date: 2018-11-19The balance between peroxisome biogenesis and degradation is crucial for redox cell homeostasis. The present invention is based on the findings that pejvakin is involved in the early and rapid selective autophagic degradation of peroxisome (pexophagy) in auditory hair cells subjected to sound overstimulation, by interacting with the autophagosome-associated protein MAP1LC3B. It is here demonstrated that it is possible to completely restore sound-induced pexophagy and to prevent oxidative stress in Pjvk-/- auditory hair cells by transducing in same the Pejvakin and MAP1LC3B proteins together. Thus, the present invention relates to compositions containing these two proteins, or gene vectors encoding same, as well as their therapeutic use for preventing and/or treating presbycusis, noise-induced hearing-loss or sudden sensorineural hearing loss or auditory damages induced by acoustic trauma or ototoxic substances, or hereditary hearing loss due to an altered expression level of Pejvakin or to an altered DFNB59 gene expression, in a subject in need thereof

Defect in the gene encoding the EAR/EPTP domain-containing protein TSPEAR causes DFNB98 profound deafness.

International audienceWe report a consanguineous Iranian family affected by congenital profound sensorineural deafness segregating in an autosomal recessive mode. Auditory tests implicated at least a cochlear defect in these patients. We mapped the deafness, autosomal recessive (DFNB) locus involved by linkage analysis to a 4.8 Mb region at chromosome 21q22.3-qter. Exclusion of the DFNB8/10 gene TMPRSS3, located in this chromosomal interval, led us to identify a new deafness locus, DFNB98. Whole exome sequencing allowed us to identify a homozygous frame-shifting mutation (c.1726G>T+c.1728delC) in the gene TSPEAR (thrombospondin-type laminin G domain and EAR repeats). This truncating mutation (p.V576LfsX37) impeded the secretion of the encoded protein by cells transfected with the mutated gene. Alternative splicing of TSPEAR transcripts predict two protein isoforms, 522 and 669 amino acids in length, both of which would be affected by the mutation. These isoforms are composed of a thrombospondin-type laminin G (TSP) domain followed by seven tandemly organized epilepsy-associated repeats (EARs), probably forming a β-propeller domain. Tspear is expressed in a variety of murine tissues. Only the larger Tspear transcript was found in the cochlea, and the protein was detected by immunofluorescence at the surface of the hair bundles of sensory cells. The mammalian EAR protein family includes six known members. Defects in four of them, i.e. Lgi1, Lgi2, Vlgr1 and, we show here, TSPEAR, cause disorders with auditory features: epilepsy, which can include auditory features in humans; audiogenic seizures in animals; and/or hearing impairments in humans and mice. These observations demonstrate that EAR-containing proteins are essential for the development and function of the auditory system

Prevention and/or treatment of hearing loss or impairment

publication date: 2016-08-25; filing date: 2016-02-19The present invention relates to the use of gasdermin, in particular of gasdermin A, gasdermin B, gasdermin C, gasdermin D, DFNA5 or DFNB59 (or pejvakin), and more particularly pejvakin for modulating cellular redox homeostasis. A particularly preferred use of gasdermin, in particular of gasdermin A, gasdermin B, gasdermin C, gasdermin D, DFNA5 or DFNB59 (or pejvakin), and more particularly pejvakin in the context of the present invention is as an antioxidant. The present invention also concerns a virally-mediated gene therapy for restoring genetically-impaired auditory and vestibular functions in subjects suffering from an Usher syndrome. More precisely, this gene therapy takes advantage of an AAV2/8 vector expressing at least one USH1 gene product, preferably SANS

Mutations in CDC14A, Encoding a Protein Phosphatase Involved in Hair Cell Ciliogenesis, Cause Autosomal-Recessive Severe to Profound Deafness

International audienceBy genetic linkage analysis in a large consanguineous Iranian family with eleven individuals affected by severe to profound congenital deafness, we were able to define a 2.8 Mb critical interval (at chromosome 1p21.2-1p21.1) for an autosomal-recessive nonsyndromic deafness locus (DFNB). Whole-exome sequencing allowed us to identify a CDC14A biallelic nonsense mutation, c.1126C>T (p.Arg376∗), which was present in the eight clinically affected individuals still alive. Subsequent screening of 115 unrelated individuals affected by severe or profound congenital deafness of unknown genetic cause led us to identify another CDC14A biallelic nonsense mutation, c.1015C>T (p.Arg339∗), in an individual originating from Mauritania. CDC14A encodes a protein tyrosine phosphatase. Immunofluorescence analysis of the protein distribution in the mouse inner ear showed a strong labeling of the hair cells’ kinocilia. By using a morpholino strategy to knockdown cdc14a in zebrafish larvae, we found that the length of the kinocilia was reduced in inner-ear hair cells. Therefore, deafness caused by loss-of-function mutations in CDC14A probably arises from a morphogenetic defect of the auditory sensory cells’ hair bundles, whose differentiation critically depends on the proper growth of their kinocilium

The paralysé (par) mouse neurological mutation maps to a 9 Mbp (4 cM) interval of mouse chromosome 18

The Paralysé mutation is a spontaneous neuromuscular mutation, first observed in 1980 at the Pasteur Institute, which is transmitted by the autosomal recessive par allele. Affected homozygote par/par mice rarely survive beyond 16 days of age and at the end of their life they are emaciated and completely paralyzed. Several concordant histological and physiological observations indicate that mutant mice might be good models for studying early-onset human motor neuron diseases such as spinal muscular atrophy. Linkage analysis using a set of molecular markers and two F2 crosses indicate that the mutation maps to mouse chromosome 18 in a region spanning 4 cM (or 9 megabase pairs, Mbp) between the microsatellites D18Mit140 and D18Mit33. These results positioned the par locus in a region homologous to human chromosome 18p11.22 to 18q21.32

Noise-induced hearing loss due to pejvakin defect: from pathogenesis to treatment

Mutations of PJVK, which encodes pejvakin, a protein of unknown function present only in vertebrates, cause the DFNB59 recessive form of sensorineural hearing impairment. In the first patients described, the impairment was restricted to neurons of the auditory pathway, as demonstrated by the combination of abnormal auditory brainstem responses (ABRs) with decreased wave amplitudes and increased inter- wave latencies. However, some DFNB59 patients were found to have a cochlear dysfunction, as shown by an absence of the otoacoustic emissions (OAEs). These patients had truncating mutations of PJVK, whereas the previously identified patients had missense mutations (p.T54I or p.R183W). However, the identification of patients also carrying the p.R183W missense mutation but lacking OAEs refuted any straightforward connection between the nature of the PJVK mutation and the hearing phenotype. The severity of deafness in DFNB59 patients varies from moderate to profound, and may even be progressive in some patients, suggesting that extrinsic factors may influence the hearing phenotype. We investigated the role of pejvakin, with the aim of determining the origin of the phenotypic variability of the DFNB59 form of deafness. Our study of Pjvk knockout mouse models and of patients revealed an unprecedented hypervulnerability of auditory hair cells and neurons to sound- exposure, accounting for phenotypic variability. We found that pejvakin is a peroxisome-associated protein involved in the oxidative stress-induced proliferation of this organelle. Pejvakin-deficient mice revealed the key role of peroxisomes in the redox homeostasis of the auditory system and in the protection against noise-induced hearing loss.ANR – NKTH “HearDeafTreat” 2010-INTB- 1402-01; French state program ‘‘Investissements d’Avenir’’ (ANR-10-LABX-65)