The proper expression and function of several unconventional myosins are 
necessary for inner-ear function. Mutations in MYO7A and MYO15 cause deafness in 
humans, and mice. Whereas mutations in Myo6 cause inner-ear abnormalities in 
mice, as yet no human deafness has been found to the result of mutations in 
MYO6. In the mammalian inner ear there are at least nine different 
unconventional myosin isozymes expressed. Myosin 1 beta, VI, VIIa and probably 
XV are all expressed within a single cell in the inner ear, the hair cell. The 
myosin isozymes expressed in the hair cell all have unique domains of expression 
and in some areas, such as the pericuticular necklace, several domains overlap. 
This suggests that these myosins all have unique functions and that all are 
individually targeted within the hair cell. The mouse is proving to be a useful 
model organism for studying both human deafness and elucidating the normal 
functions of unconventional myosins in vivo.