Gene Therapy for Hearing and Balance defects : How close are we ?

Since the initial report on hearing restoration by cochlear gene transfer in a mouse mutant defective for vesicular gluta-mate transporter-3 (VGLUT3-/-), a growing number of studies tackle similar objectives in the perspective of developing inner ear gene therapy in humans. This presentation will focus on our main approaches to inner ear gene therapy, including the prevention of noise-induced hearing loss and the restoration of balance in vestibulopathies. The first issue was addressed upon the finding that the mutations in the gene encoding pejvakin (Pjvk) result in an hy-pervulnerability to sound in mice and humans caused by a marked oxidative stress; this stress develops as a consequence of the defect in the adaptive peroxisome proliferation in response to noise exposure. The results of a comparative analysis of the prevention of noise-induced hearing loss by anti-oxidant drugs and adeno-associated virus (AAV) gene transfer of the murine Pjvk cDNA in Pjvk-/-mice will be discussed. The second issue was addressed in a mouse model for Usher syndrome of type 1G (USH 1G), that is characterized by congenital profound deafness, vestibular dysfunction, and retinitis pigmentosa. This gene encodes Sans, a scaffolding protein expressed in the cochlear and the vestibular hair-bundles. The results of the cure of hearing and vestibular disorders of Ush1g-/-mutant mice by an recombinant AAV2/8 carrying the Ush1g cDNA will be presented with a special focus on the vestibulopathy of the syndrome. Introduction The high prevalence/incidence of hearing loss (HL) in humans makes it the most common sensory defect. The majority of the cases are of genetic origin. Non-syndromic hereditary HL is extremely heterogeneous. Genetic approaches have been instrumental in deciphering genes that are crucial for auditory function. Goal Mapping and identification of the gene causing ARNSHL in a large consanguineous Tunisian family (FT13), and characterization of the function of the encoded protein. Methods We used NADf chip to screen for common North African HL-causing mutation in FT13. We performed genome-wide linkage analysis to map the causative gene. We performed whole-exome sequencing on patient DNA to identify homo-zygous variants in genes within the determined locus that would cause the disease. We screened a cohort of small Tunisian HL families searching for additional patients carrying the same variants. We studied the targeting properties of candidate proteins in cell lines and performed immunoflu-orescence on rat inner ear preparations to study their tissue and cellular localization. We used morpholino-based gene knockdown, live imaging, immunofluorescence, and electro-physiological …