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A R T I C L E Unconventional Myosins and the Genetics of
 

Summary: A R T I C L E
Unconventional Myosins and the Genetics of
Hearing Loss
THOMAS B. FRIEDMAN,* JAMES R. SELLERS, AND KAREN B. AVRAHAM
Mutations of the unconventional myosins genes encoding myosin VI, myosin VIIA and myosin XV cause
hearing loss and thus these motor proteins perform fundamental functions in the auditory system. A null
mutation in myosin VI in the congenitally deaf Snell's waltzer mice (Myo6sv
) results in fusion of stereocilia
and subsequent progressive loss of hair cells, beginning soon after birth, thus reinforcing the vital role of
cytoskeletal proteins in inner ear hair cells. To date, there are no human families segregating hereditary
hearing loss that show linkage to MYO6 on chromosome 6q13. The discovery that the mouse shaker1
(Myo7ash1
) locus encodes myosin VIIA led immediately to the identification of mutations in this gene in
Usher syndrome type 1B; subsequently, mutations in this gene were also found associated with recessive
and dominant nonsyndromic hearing loss (DFNB2 and DFNA11). Stereocilla of sh1 mice are severely disor-
ganized, and eventually degenerate as well. Myosin VIIA has been implicated in membrane trafficking
and/or endocytosis in the inner ear. Mutant alleles of a third unconventional myosin, myosin XV, are
associated with nonsyndromic, recessive, congenital deafness DFNB3 on human chromosome 17p11.2 and
deafness in shaker2 (Myo15sh2
) mice. In outer and inner hair cells, myosin XV protein is detectable in the

  

Source: Avraham, Karen - Department of Human Genetics and Molecular Medicine, Tel Aviv University

 

Collections: Biology and Medicine