Early development and degeneration of vestibular hair cells in bronx waltzer mutant mice.

In bronx waltzer mouse mutants, inner hair cells die at an early stage in their development, from around 17.5 days of gestation onwards. In contrast, outer hair cells appear to develop normally. Vestibular hair cells also degenerate, but the earliest signs of vestibular abnormalities have not yet been described. We looked at prenatal and early postnatal stages of vestibular development by scanning electron microscopy in the mutants, and established that vestibular hair cells (types I and II) never reach beyond the middle stages of differentiation (at least up to P2) and instead show signs of degeneration. Thus, it appears that the bronx waltzer gene product is required for the continued survival and differentiation of inner and vestibular hair cells past a set point in their development.