Abstract
Sensory hair cells, the mechanoreceptors of the auditory and vestibular systems, harbor two specialized elaborations of the apical surface, the hair bundle and the cuticular plate. In contrast to the extensively studied mechanosensory hair bundle, the cuticular plate is not as well understood. It is believed to provide a rigid foundation for stereocilia motion, but specifics about its function, especially the significance of its integrity for long-term maintenance of hair cell mechanotransduction, are not known. We discovered that a hair cell protein called LIM only protein 7 (LMO7) is specifically localized in the cuticular plate and the cell junction. Lmo7 KO mice suffer multiple cuticular plate deficiencies, including reduced filamentous actin density and abnormal stereociliar rootlets. In addition to the cuticular plate defects, older Lmo7 KO mice develop abnormalities in inner hair cell stereocilia. Together, these defects affect cochlear tuning and sensitivity and give rise to late-onset progressive hearing loss.
Highlights
Sensory hair cells, the mechanoreceptors of the auditory and vestibular systems, harbor two specialized elaborations of the apical surface, the hair bundle and the cuticular plate
Subsequent immunolocalization analysis showed that LIM only protein 7 (LMO7) is expressed in the mouse inner ear and highly enriched in the sensory hair cells (Fig. 1d, e and Supplementary Fig. 1a)
Our investigation into the role of LMO7 provides a unique avenue into a better understanding of the significance of the cuticular plate for the performance of the hair cell and the cochlea
Summary
The mechanoreceptors of the auditory and vestibular systems, harbor two specialized elaborations of the apical surface, the hair bundle and the cuticular plate. In addition to the cuticular plate defects, older Lmo[7] KO mice develop abnormalities in inner hair cell stereocilia. Together, these defects affect cochlear tuning and sensitivity and give rise to late-onset progressive hearing loss. Two specialized structures at the apical surface of the hair cell, the hair bundle, and the cuticular plate, are essential for hair cell mechanotransduction[1,2,3,4,5,6,7]. Our studies show that in the hair cell, LMO7 is localized to the cuticular plate and intercellular junctions, where it plays a role in F-actin network organization. LMO7 is a hair cellenriched protein, with specific localization to the cuticular plate and the cell junctions
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