title: Length regulation of mechanosensitive stereocilia depends on very slow actin dynamics and filament-severing proteins.
abstract: Auditory sensory hair cells depend on stereocilia with precisely regulated lengths to detect sound. Since stereocilia are primarily composed of crosslinked, parallel actin filaments, regulated actin dynamics are essential for controlling stereocilia length. Here we assessed stereocilia actin turnover by monitoring incorporation of inducibly expressed β-actin-GFP in adult mouse hair cells in vivo and by directly measuring β-actin-GFP turnover in explants. Stereocilia actin incorporation is remarkably slow and restricted to filament barbed ends in a small tip compartment, with minimal accumulation in the rest of the actin core. Shorter rows of stereocilia, which have mechanically gated ion channels, show more variable actin turnover than the tallest stereocilia, which lack channels. Finally, the proteins ADF and AIP1, which both mediate actin filament severing, contribute to stereocilia length maintenance. Altogether, the data support a model whereby stereocilia actin cores are largely static, with dynamic regulation at the tips to maintain a critical length.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Praveena
authors.initials: P
authors.lastname: Narayanan
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Chatterton
authors.affiliation: Department of Medical Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ikeda
authors.affiliation: Department of Medical Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Sakae
authors.initials: S
authors.lastname: Ikeda
authors.affiliation: Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Corey
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Ervasti
authors.affiliation: Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46022, USA.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Perrin
mesh_terms: D008841:Actin Cytoskeleton / Q000502:physiology*; D000199:Actins / Q000502:physiology*; D000818:Animals; D003001:Cloning, Molecular; D005786:Gene Expression Regulation / Q000502:physiology; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D051379:Mice; D009925:Organ of Corti / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D000199:Actins