title: Deletion of Drosophila muscle LIM protein decreases flight muscle stiffness and power generation.
abstract: Muscle LIM protein (MLP) can be found at the Z-disk of sarcomeres where it is hypothesized to be involved in sensing muscle stretch. Loss of murine MLP results in dilated cardiomyopathy, and mutations in human MLP lead to cardiac hypertrophy, indicating a critical role for MLP in maintaining normal cardiac function. Loss of MLP in Drosophila (mlp84B) also leads to muscle dysfunction, providing a model system to examine MLP's mechanism of action. Mlp84B-null flies that survive to adulthood are not able to fly or beat their wings. Transgenic expression of the mlp84B gene in the Mlp84B-null background rescues flight ability and restores wing beating ability. Mechanical analysis of skinned flight muscle fibers showed a 30% decrease in oscillatory power production and a slight increase in the frequency at which maximum power is generated for fibers lacking Mlp84B compared with rescued fibers. Mlp84B-null muscle fibers displayed a 25% decrease in passive, active, and rigor stiffness compared with rescued fibers, but no significant decrease in isometric tension generation was observed. Muscle ultrastructure of Mlp84B-null muscle fibers is grossly normal; however, the null fibers have a slight decrease, 11%, in thick filament number per unit cross-sectional area. Our data indicate that MLP contributes to muscle stiffness and is necessary for maximum work and power generation.
authors.affiliation: Department of Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute,, Troy, NY 12180, USA.
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Clark
authors.forename: Heather
authors.initials: H
authors.lastname: Lesage-Horton
authors.forename: Cuiping
authors.initials: C
authors.lastname: Zhao
authors.forename: Mary C
authors.initials: MC
authors.lastname: Beckerle
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Swank
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D004330:Drosophila / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029721:Drosophila Proteins / Q000172:deficiency* / Q000235:genetics; D005426:Flight, Animal; D017353:Gene Deletion; D005838:Genotype; D007537:Isometric Contraction; D060588:LIM Domain Proteins; D046529:Microscopy, Electron, Transmission; D018485:Muscle Fibers, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D009124:Muscle Proteins / Q000172:deficiency* / Q000235:genetics; D053580:Muscle Strength; D010641:Phenotype; D014921:Wings, Animal / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D029721:Drosophila Proteins; D060588:LIM Domain Proteins; C101416:Mlp84B protein, Drosophila; D009124:Muscle Proteins