Recessive deafness occurs sporadically in families sometimes skipping several generations. Most individuals with recessive deafness have hearing parents and may have brothers and sisters who can hear and others who are deaf. The sporadic nature of this type of deafness along with the lack of other physical characteristics have made identification of individuals with the same altered or mutated gene difficult to identify and study. These investigators used a mouse model to identify the new protein. Myo15 gene was recently discovered by his collaborators, Sally Camper, Ph.D., and graduate student Frank Probst, at the University of Michigan, also causing deafness in the shaker-2 mouse.
Myosins are a large family of proteins that are found in most human cells.
There are fourteen classes of myosin known as conventional and unconventional. One type of unconventional myosin, Myosin 7a, has previously been implicated in three other forms of deafness. These three types of deafness are Usher syndrome type 1 which is characterized by profound deafness from birth and severe balance problems, and a dominant as well as a recessive type of deafness that has so far only been identified in families from Tunisia. Mutation of another unconventional myosin, myosin 6, has been implicated in the deafness of another mouse model, the Snell's waltzer mouse. These hair cells reside in the cochlea of the inner ear and are involved in sensory transduction or the conversion of sound waves into electrical signals that are sent to the brain where meaning is attached to them.