Fast skeletal muscle regulatory light chain is required for fast and slow skeletal muscle development
Authors
Wang, YingcaiSzczesna-Cordary, Danuta
Craig, Roger W.
Diaz-Perez, Zoraida
Guzman, Georgianna
Miller, Todd
Potter, James D.
UMass Chan Affiliations
Department of Cell BiologyDocument Type
Journal ArticlePublication Date
2007-03-16Keywords
AnimalsAnimals, Newborn
Crosses, Genetic
Female
Fetal Heart
Gene Expression Regulation, Developmental
Genes, Lethal
Genotype
Male
Mice
Mice, Inbred C57BL
Mice, Knockout
Muscle Fibers, Fast-Twitch
Muscle Fibers, Slow-Twitch
Muscle, Skeletal
Myocardium
Myosin Light Chains
Polymerase Chain Reaction
Cell Biology
Metadata
Show full item recordAbstract
In skeletal muscle, the myosin molecule contains two sets of noncovalently attached low molecular weight proteins, the regulatory (RLC) and essential (ELC) light chains. To assess the functional and developmental significance of the fast skeletal isoform of the RLC (RLC-f), the murine fast skeletal RLC gene (Mylpf) was disrupted by homologous recombination. Heterozygotes containing an intronic neo cassette (RLC-/+) had approximately one-half of the amount of the RLC-f mRNA compared to wild-type (WT) mice but their muscles were histologically normal in both adults and neonates. In contrast, homozygous mice (RLC-/-) had no RLC-f mRNA or protein and completely lacked both fast and slow skeletal muscle. This was likely due to interference with mRNA processing in the presence of the neo cassette. These RLC-f null mice died immediately after birth, presumably due to respiratory failure since their diaphragms lacked skeletal muscle. The body weight of newborn RLC-f null mice was decreased 30% compared to heterozygous or WT newborn mice. The lack of skeletal muscle formation in the null mice did not affect the development of other organs including the heart. In addition, we found that WT mice did not express the ventricular/slow skeletal RLC isoform (RLC-v/s) until after birth, while it was expressed normally in the embryonic heart. The lack of skeletal muscle formation observed in RLC-f null mice indicates the total dependence of skeletal muscle development on the presence of RLC-f during embryogenesis. This observation, along with the normal function of the RLC-v/s in the heart, implicates a coupled, diverse pathway for RLC-v/s and RLC-f during embryogenesis, where RLC-v/s is responsible for heart development and RLC-f is necessary for skeletal muscle formation. In conclusion, in this study we demonstrate that the Mylpf gene is critically important for fast and slow skeletal muscle development.Source
FASEB J. 2007 Jul;21(9):2205-14. Epub 2007 Mar 13. Link to article on publisher's siteDOI
10.1096/fj.06-7538comPermanent Link to this Item
http://hdl.handle.net/20.500.14038/27658PubMed ID
17356007Related Resources
Link to Article in PubMedae974a485f413a2113503eed53cd6c53
10.1096/fj.06-7538com
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Orientation of myosin binding protein C in the cardiac muscle sarcomere determined by domain-specific immuno-EMLee, Kyounghwan; Harris, Samantha P.; Sadayappan, Sakthivel; Craig, Roger (2015-01-30)Myosin binding protein C is a thick filament protein of vertebrate striated muscle. The cardiac isoform [cardiac myosin binding protein C (cMyBP-C)] is essential for normal cardiac function, and mutations in cMyBP-C cause cardiac muscle disease. The rod-shaped molecule is composed primarily of 11 immunoglobulin- or fibronectin-like domains and is located at nine sites, 43nm apart, in each half of the A-band. To understand how cMyBP-C functions, it is important to know its structural organization in the sarcomere, as this will affect its ability to interact with other sarcomeric proteins. Several models, in which cMyBP-C wraps around, extends radially from, or runs axially along the thick filament, have been proposed. Our goal was to define cMyBP-C orientation by determining the relative axial positions of different cMyBP-C domains. Immuno-electron microscopy was performed using mouse cardiac myofibrils labeled with antibodies specific to the N- and C-terminal domains and to the middle of cMyBP-C. Antibodies to all regions of the molecule, except the C-terminus, labeled at the same nine axial positions in each half A-band, consistent with a circumferential and/or radial rather than an axial orientation of the bulk of the molecule. The C-terminal antibody stripes were slightly displaced axially, demonstrating an axial orientation of the C-terminal three domains, with the C-terminus closer to the M-line. These results, combined with previous studies, suggest that the C-terminal domains of cMyBP-C run along the thick filament surface, while the N-terminus extends toward neighboring thin filaments. This organization provides a structural framework for understanding cMyBP-C's modulation of cardiac muscle contraction.
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