A missense mutation in myosin VIIA prevents aminoglycoside accumulation in early postnatal cochlear hair cells.

Myosin VIIA is expressed by sensory hair cells in the inner ear and proximal tubule cells in the kidney, the two primary targets of aminoglycoside antibiotics. Using cochlear cultures prepared from early postnatal Myo7a6J mice with a missense mutation in the head region of the myosin VIIA molecule we show that this myosin is required for aminoglycoside accumulation in cochlear hair cells. Hair cells in homozygous mutant Myo7a6J cochlear cultures have disorganized hair bundles, but are otherwise morphologically normal and transduce. However, and in contrast to hair cells from heterozygous Myo7a6J cultures, the homozygous Myo7a6J hair cells do not accumulate [3H]gentamicin and do not exhibit an ototoxic response on exposure to aminoglycoside. Possible roles for myosin VIIA in the process of aminoglycoside accumulation are discussed.