Reduced climbing and increased slipping adaptation in cochlear hair cells of mice with Myo7a mutations.

Mutations in Myo7a cause hereditary deafness in mice and humans. We describe the effects of two mutations, Myo7a(6J) and Myo7a(4626SB), on mechano-electrical transduction in cochlear hair cells. Both mutations result in two major functional abnormalities that would interfere with sound transduction. The hair bundles need to be displaced beyond their physiological operating range for mechanotransducer channels to open. Transducer currents also adapt more strongly than normal to excitatory stimuli. We conclude that myosin VIIA participates in anchoring and holding membrane-bound elements to the actin core of the stereocilium. Myosin VIIA is therefore required for the normal gating of transducer channels.