Unconventional myosins in inner-ear sensory epithelia

Tama Hasson, Peter Barr-Gillespie, Jesus A. Garcia, Richard B. MacDonald, Yi Dong Zhao, Ann G. Yee, Mark S. Mooseker, David P. Corey

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Abstract

To understand how cells differentially use the dozens of myosin isozymes present in each genome, we examined the distribution of four unconventional myosin isozymes in the inner ear, a tissue that is particularly reliant on actin-rich structures and unconventional myosin isozymes. Of the four isozymes, each from a different class, three are expressed in the hair cells of amphibia and mammals. In stereocilia, constructed of cross-linked F-actin filaments, myosin-Iβ is found mostly near stereociliary tips, myosin-VI is largely absent, and myosin-VIIa colocalizes with cross-links that connect adjacent stereocilia. In the cuticular plate, a meshwork of actin filaments, myosin-Iβ is excluded, myosin-VI is concentrated, and modest amounts of myosin-VIIa are present. These three myosin isozymes are excluded from other actin-rich domains, including the circumferential actin belt and the cortical actin network. A member of a fourth class, myosin-V, is not expressed in hair cells but is present at high levels in afferent nerve cells that innervate hair cells. Substantial amounts of myosins-Iβ, -VI, and -VIIa are located in a pericuticular necklace that is largely free of F-actin, squeezed between (but not associated with) actin of the cuticular plate and the circumferential belt. Our localization results suggest specific functions for three hair-cell myosin isozymes. As suggested previously, myosin-Iβ probably plays a role in adaptation; concentration of myosin-VI in cuticular plates and association with stereociliary rootlets suggest that this isozyme participates in rigidly anchoring stereocilia; and finally, colocalization with cross-links between adjacent stereocilia indicates that myosin-VIIa is required for the structural integrity of hair bundles.

Original languageEnglish (US)
Pages (from-to)1287-1307
Number of pages21
JournalJournal of Cell Biology
Volume137
Issue number6
DOIs
Publication statusPublished - Jun 16 1997
Externally publishedYes

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ASJC Scopus subject areas

  • Cell Biology

Cite this

Hasson, T., Barr-Gillespie, P., Garcia, J. A., MacDonald, R. B., Zhao, Y. D., Yee, A. G., ... Corey, D. P. (1997). Unconventional myosins in inner-ear sensory epithelia. Journal of Cell Biology, 137(6), 1287-1307. https://doi.org/10.1083/jcb.137.6.1287