ABSTRACT
The waltzing guinea pig displays severe inner ear dysfunction that involves both an auditory and a vestibular manifestation. The aim of this study was to characterize a pathological tail-like extension of the vestibular hair cells, the cytocaud. Our data suggest that nearly all type I hair cells in the waltzing guinea pig have cytocauds, which appear as membrane-bound tails containing mitochondria and cytoplasm that proceed in a basal direction toward the basement membrane. The extensions either attach to the basement membrane or penetrate it, and further proceed into the extracellular matrix. A core made of a thick and long (30 microm) actin-rich structure supports the slender long process. The actin core has cross-links that are periodically placed along the length of the cytocaud. Our data suggest that the cytocauds in vestibular hair cells of the waltzing guinea pig are highly organized structures associated with a failure to detach from the basement membrane.