Progressive Degeneration of Stereocilia in Cochlear Hair Cells in Hearing-impaired Kuru² Mice

Abstract

Background: We previously isolated a mouse strain, kuru², which exhibits abnormal behavior and hearing impairment. To investigate the etiology of this impairment, the ultrastructure of the inner ear was examined. Materials and Methods: The morphologies of the cochlea and the vestibule of control (Jcl:ICR) and mutant mice were analyzed by electron microscopy. In some experiments, the mice were cross-mated and their offspring examined. Results: The mutant mice displayed progressive degeneration of the stereocilia in the cochlea. The stereocilia started to degenerate on post-natal day 10 and, subsequently, the hair bundles continued to degenerate. On day 18, degeneration of the stereocilia was complete. In contrast, the vestibule was intact. Discussion: Many mutant mice display hearing impairment. These mice demonstrate a characteristic morphology of the inner ear and, since correlations may be made with corresponding human diseases, the current results could contribute to the further understanding of hearing impairment mechanisms.