Single Administration of AAV‐m <i>Atp6v1b2</i> Gene Therapy Rescues Hearing and Vestibular Disorders Caused by <i>Atp6v1b2</i> ‐Induced Lysosomal Dysfunction in Hair Cells

Haploinsufficiency of the ATP6V1B2, a subunit of V-ATPases, underlies genetic disorders including Dominant deafness-onychodystrophy (DDOD), deafness, onychodystrophy, osteodystrophy, mental retardation and seizures (DOORS), and Zimmermann-Laband syndromes, all characterized by congenital hearing loss and onychodystrophy. Effective therapies for ATP6V1B2-associated hearing loss remain elusive. The study generates a hair cell-specific knockout mouse (Atp6v1b2^fl/fl;Atoh1^Cre/+) recapitulating the human phenotypes, with pathological features including hair cell loss and abnormal lysosomal morphology and function. To enhance therapeutic precision and minimize toxicity, an optimized adeno-associated virus-inner ear vector incorporating promoter enhancer 3 (AAV-ie-Eh3) is engineered. A single administration of AAV-ie-Eh3-mAtp6v1b2 into the scala media at postnatal days 0-2, prevented hair cell degeneration, restored lysosome morphology, and robustly rescued auditory and vestibular function for at least 24 weeks. The findings highlight the critical role of Atp6v1b2 in lysosomal function and demonstrate AAV-ie-Eh3 as a potent gene delivery tool for inner ear therapy. This study establishes a novel therapeutic paradigm for ATP6V1B2-associated hearing loss and vestibular dysfunction, with significant clinical potential.