βcyto-Actin and γcyto-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 γcyto-actin null mice (Actg1-/-) are viable. However, they suffer increased mortality and show progressive hearing loss during adulthood despite compensatory up-regulation of βcyto- actin. The surprising viability and normal hearing of young Actg1-/- mice means that βcyto-actin can likely build all essential non-muscle actin-based cytoskeletal structures including mechanosensory stereocilia of hair cells that are necessary for hearing. Although γcyto-actin-deficient stereocilia form normally, we found that they cannot maintain the integrity of the stereocilia actin core. In the wild-type, γcyto-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 γcyto-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.
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Jun 16 2009|
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