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Cell. 2010 May 28;141(5):786-98. doi: 10.1016/j.cell.2010.03.049.

Actin-bundling protein TRIOBP forms resilient rootlets of hair cell stereocilia essential for hearing.

Author information

1
Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD 20850, USA.

Abstract

Inner ear hair cells detect sound through deflection of mechanosensory stereocilia. Each stereocilium is supported by a paracrystalline array of parallel actin filaments that are packed more densely at the base, forming a rootlet extending into the cell body. The function of rootlets and the molecules responsible for their formation are unknown. We found that TRIOBP, a cytoskeleton-associated protein mutated in human hereditary deafness DFNB28, is localized to rootlets. In vitro, purified TRIOBP isoform 4 protein organizes actin filaments into uniquely dense bundles reminiscent of rootlets but distinct from bundles formed by espin, an actin crosslinker in stereocilia. We generated mutant Triobp mice (Triobp(Deltaex8/Deltaex8)) that are profoundly deaf. Stereocilia of Triobp(Deltaex8/Deltaex8) mice develop normally but fail to form rootlets and are easier to deflect and damage. Thus, F-actin bundling by TRIOBP provides durability and rigidity for normal mechanosensitivity of stereocilia and may contribute to resilient cytoskeletal structures elsewhere.

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PMID:
20510926
PMCID:
PMC2879707
DOI:
10.1016/j.cell.2010.03.049
[Indexed for MEDLINE]
Free PMC Article

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