Costameres are subsarcolemmal protein assemblies in striated muscle cells that physically couple force-generating sarcomeres with the sarcolemma. Costameres are clearly important for normal muscle function because several constituent proteins are the primary sites of defect in human muscular dystrophies and dilated cardiomyopathies. We previously demonstrated that the costameric cytoskeleton is enriched in non-muscle "cytoplasmic" ?cyto-actin and that muscle-specific ablation of ?cyto-actin causes a novel form of progressive myopathy. The major objective of this renewal is to elucidate the important, but poorly understood functions of both ?cyto- and ?cyto-actin isoforms in skeletal muscle. We will make use of novel conditional animal models and isoform-specific reagents generated by my group during the original project period to address several fundamental questions about cytoplasmic actins in normal skeletal muscle function and in human diseases of skeletal muscle tissue.
In aim 1, we will investigate the specific contribution of ?cyto-actin to the mechanical function of skeletal muscle, which may also shed light into the mechanism of contraction-induced injury of normal and dystrophin-deficient muscle.
In aim 2, the distinct and overlapping roles of ?cyto- and ?cyto- actins in developing and adult skeletal muscle, particularly in costameres, will be investigated through the characterization of mouse lines in which either ?cyto-actin, or ?cyto- and ?cyto-actins have been knocked out specifically in skeletal muscle.
In aim 3, we will test the hypothesized role for aberrant ?cyto-actin localization in the pathogenesis of spinal muscular atrophy both in vivo and in vitro. The results of the proposed studies will most definitively address the unique and important contributions of cytoplasmic actin isoforms to the function of normal and diseased skeletal muscle.
The sarcomeric actin isoforms are well known for their important role in contraction of skeletal and cardiac muscle. However, the roles of non-muscle cytoplasmic actin isoforms in the development/maintenance of specialized muscle structures and their contribution to diseases of skeletal muscle are also important, but remain poorly understood. Through rigorous characterization of skeletal muscle in genetically-modified lines of mice where one or both non-muscle cytoplasmic actins are selectively eliminated in combination with complementary experiments on isolated cells and proteins, the proposed studies will most definitively address the unique and important contributions of non-muscle cytoplasmic actin isoforms to the function of normal and diseased skeletal muscle. In particular, this project is highly relevant to understanding the pathological mechanism of Duchenne muscular dystrophy and spinal muscular atrophy.
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|Perrin, Benjamin J; Strandjord, Dana M; Narayanan, Praveena et al. (2013) ýý-Actin and fascin-2 cooperate to maintain stereocilia length. J Neurosci 33:8114-21|
|Cheever, Thomas R; Li, Bin; Ervasti, James M (2012) Restricted morphological and behavioral abnormalities following ablation of ?-actin in the brain. PLoS One 7:e32970|
|Zhang, Duan-Sun; Piazza, Valeria; Perrin, Benjamin J et al. (2012) Multi-isotope imaging mass spectrometry reveals slow protein turnover in hair-cell stereocilia. Nature 481:520-4|
|Bunnell, Tina M; Burbach, Brandon J; Shimizu, Yoji et al. (2011) ?-Actin specifically controls cell growth, migration, and the G-actin pool. Mol Biol Cell 22:4047-58|
|Perrin, Benjamin J; Sonnemann, Kevin J; Ervasti, James M (2010) ?-actin and ?-actin are each dispensable for auditory hair cell development but required for Stereocilia maintenance. PLoS Genet 6:e1001158|
|Bunnell, Tina M; Ervasti, James M (2010) Delayed embryonic development and impaired cell growth and survival in Actg1 null mice. Cytoskeleton (Hoboken) 67:564-72|
|Perrin, Benjamin J; Ervasti, James M (2010) The actin gene family: function follows isoform. Cytoskeleton (Hoboken) 67:630-4|
|Belyantseva, Inna A; Perrin, Benjamin J; Sonnemann, Kevin J et al. (2009) Gamma-actin is required for cytoskeletal maintenance but not development. Proc Natl Acad Sci U S A 106:9703-8|
|Jaeger, Michele A; Sonnemann, Kevin J; Fitzsimons, Daniel P et al. (2009) Context-dependent functional substitution of alpha-skeletal actin by gamma-cytoplasmic actin. FASEB J 23:2205-14|
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