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Gamma-actin is required for cytoskeletal maintenance but not development.

Beta(cyto)-actin and gamma(cyto)-actin are ubiquitous proteins thought to be essential building blocks of the cytoskeleton in all non-muscle cells. Despite this widely held supposition, we show that gamma(cyto)-actin null mice (Actg1(-/-)) are viable. However, they suffer increased mortality and show progressive hearing loss during adulthood despite compensatory up-regulation of beta(cyto)-actin. The surprising viability and normal hearing of young Actg1(-/-) mice means that beta(cyto)-actin can likely build all essential non-muscle actin-based cytoskeletal structures including mechanosensory stereocilia of hair cells that are necessary for hearing. Although gamma(cyto)-actin-deficient stereocilia form normally, we found that they cannot maintain the integrity of the stereocilia actin core. In the wild-type, gamma(cyto)-actin localizes along the length of stereocilia but re-distributes to sites of F-actin core disruptions resulting from animal exposure to damaging noise. In Actg1(-/-) stereocilia similar disruptions are observed even without noise exposure. We conclude that gamma(cyto)-actin is required for reinforcement and long-term stability of F-actin-based structures but is not an essential building block of the developing cytoskeleton.

Pubmed ID: 19497859


  • Belyantseva IA
  • Perrin BJ
  • Sonnemann KJ
  • Zhu M
  • Stepanyan R
  • McGee J
  • Frolenkov GI
  • Walsh EJ
  • Friderici KH
  • Friedman TB
  • Ervasti JM


Proceedings of the National Academy of Sciences of the United States of America

Publication Data

June 16, 2009

Associated Grants

  • Agency: NIDCD NIH HHS, Id: DC004568
  • Agency: NIDCD NIH HHS, Id: F32 DC009539
  • Agency: NIDCD NIH HHS, Id: F32 DC009539
  • Agency: NIDCD NIH HHS, Id: F32 DC009539-02
  • Agency: NIAMS NIH HHS, Id: R01 AR049899
  • Agency: NIA NIH HHS, Id: T32 AG029796
  • Agency: Intramural NIH HHS, Id:

Mesh Terms

  • Actins
  • Animals
  • Cytoskeleton
  • Hearing Loss
  • Mice
  • Mice, Knockout
  • Microscopy, Electron, Scanning
  • Microscopy, Fluorescence