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Role of Myosin VI in the Differentiation of Cochlear Hair Cells

Summary: Role of Myosin VI in the Differentiation
of Cochlear Hair Cells
Tim Self,* Tama Sobe, Neal G. Copeland, Nancy A. Jenkins,
Karen B. Avraham, and Karen P. Steel*,1
*MRC Institute of Hearing Research, University Park, Nottingham NG7 2RD, United
Kingdom; Department of Human Genetics and Molecular Medicine, Sackler School
of Medicine, Tel Aviv University, Tel Aviv 69978, Israel; and Mammalian Genetics
Laboratory, ABL­Basic Research Program, National Cancer Institute­Frederick
Cancer Research and Development Center, Frederick, Maryland 21702
The mouse mutant Snell's waltzer (sv) has an intragenic deletion of the Myo6 gene, which encodes the unconventional
myosin molecule myosin VI (K. B. Avraham et al., 1995, Nat. Genet. 11, 369­375). Snell's waltzer mutants exhibit
behavioural abnormalities suggestive of an inner ear defect, including lack of responsiveness to sound, hyperactivity, head
tossing, and circling. We have investigated the effects of a lack of myosin VI on the development of the sensory hair cells
of the cochlea in these mutants. In normal mice, the hair cells sprout microvilli on their upper surface, and some of these
grow to form a crescent or V-shaped array of modified microvilli, the stereocilia. In the mutants, early stages of stereocilia
development appear to proceed normally because at birth many stereocilia bundles have a normal appearance, but in places
there are signs of disorganisation of the bundles. Over the next few days, the stereocilia become progressively more
disorganised and fuse together. Practically all hair cells show fused stereocilia by 3 days after birth, and there is extensive
stereocilia fusion by 7 days. By 20 days, giant stereocilia are observed on top of the hair cells. At 1 and 3 days after birth,
hair cells of mutants and controls take up the membrane dye FM1-43, suggesting that endocytosis occurs in mutant hair


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


Collections: Biology and Medicine