Rods of actin filaments in type I hair cells of the Shaker-2 mouse.

The shaker-2 mouse with inherited inner ear disease suffers from deafness and a shaking-waltzing behavior. The hair cell type I in cristae ampullares and maculae utriculi show a specific pathology, featuring fusion of the stereocilia and presence of a rod-shaped inclusion body. The inclusion body is composed of filaments that could be identified as the protein actin by the method of decoration with subfragment S-1 of myosin. The functional polarity was determined, and S-1 fragments were found to point apically, that is, from the nucleus up toward the cuticular plate. These observations are identical to those earlier described in the waltzing guinea pig. It is concluded that the identical pathology at a cellular level in two different species may indicate a pathologic disorder in a process fundamental to the normal development of this type of hair cell.