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

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.

Pubmed ID: 20510926


  • Kitajiri S
  • Sakamoto T
  • Belyantseva IA
  • Goodyear RJ
  • Stepanyan R
  • Fujiwara I
  • Bird JE
  • Riazuddin S
  • Riazuddin S
  • Ahmed ZM
  • Hinshaw JE
  • Sellers J
  • Bartles JR
  • Hammer JA
  • Richardson GP
  • Griffith AJ
  • Frolenkov GI
  • Friedman TB



Publication Data

May 28, 2010

Associated Grants

  • Agency: Wellcome Trust, Id: 071394/Z/03/Z
  • Agency: NIDCD NIH HHS, Id: R00 DC009287
  • Agency: NIDCD NIH HHS, Id: R01 DC004314
  • Agency: NIDCD NIH HHS, Id: R01 DC004314
  • Agency: NIDCD NIH HHS, Id: R01 DC008861
  • Agency: NIDCD NIH HHS, Id: R01 DC009434
  • Agency: NIDCD NIH HHS, Id: R01DC008861
  • Agency: NIDCD NIH HHS, Id: R01DC009434
  • Agency: Intramural NIH HHS, Id: ZIA DC000039-13
  • Agency: Intramural NIH HHS, Id: ZIA DC000048-12

Mesh Terms

  • Actin Cytoskeleton
  • Animals
  • Deafness
  • Hair Cells, Auditory, Inner
  • Humans
  • Mechanotransduction, Cellular
  • Mice
  • Mice, Knockout
  • Microfilament Proteins
  • Molecular Sequence Data