Abstract
The stereocilia of the inner ear sensory cells contain the actin-binding protein radixin, encoded by RDX. Radixin is important for hearing but remains functionally obscure. To determine how radixin influences hearing sensitivity, we used a custom rapid imaging technique to visualize stereocilia motion while measuring electrical potential amplitudes during acoustic stimulation. Radixin inhibition decreased sound-evoked electrical potentials. Other functional measures, including electrically induced sensory cell motility and sound-evoked stereocilia deflections, showed a minor amplitude increase. These unique functional alterations demonstrate radixin as necessary for conversion of sound into electrical signals at acoustic rates. We identified patients with RDX variants with normal hearing at birth who showed rapidly deteriorating hearing during the first months of life. This may be overlooked by newborn hearing screening and explained by multiple disturbances in postnatal sensory cells. We conclude radixin is necessary for ensuring normal conversion of sound to electrical signals in the inner ear.
Highlights
The stereocilia of the inner ear sensory cells contain the actin-binding protein radixin, encoded by RDX
The protein radixin appears to be an important component of this machinery, since radixin-deficient mice are deaf[1] from an early age and biallelic variants in the human RDX gene is a cause of non-syndromic neurosensory hearing loss
Since the sensory outer hair cells must be intact for otoacoustic emissions to be generated, this ruled out peripheral hearing loss[13]
Summary
The stereocilia of the inner ear sensory cells contain the actin-binding protein radixin, encoded by RDX. Other functional measures, including electrically induced sensory cell motility and soundevoked stereocilia deflections, showed a minor amplitude increase These unique functional alterations demonstrate radixin as necessary for conversion of sound into electrical signals at acoustic rates. To determine the influence of radixin on cochlear amplification and sensory cell function, we used a custom rapid confocal imaging technique to examine stereocilia motion while recording the electrical potentials produced by the sensory cells during acoustic stimulation. The sound-evoked electrical potentials were substantially reduced despite other important functional measures, such as stereocilia deflections and electrically induced motility being intact This shows that radixin is necessary for the normal function of mechanically sensitive ion channels, allowing them to work at acoustic rates
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