title: Structural and functional roles of desmin in mouse skeletal muscle during passive deformation.
abstract: Mechanical interactions between desmin and Z-disks, costameres, and nuclei were measured during passive deformation of single muscle cells. Image processing and continuum kinematics were used to quantify the structural connectivity among these structures. Analysis of both wild-type and desmin-null fibers revealed that the costamere protein talin colocalized with the Z-disk protein alpha-actinin, even at very high strains and stresses. These data indicate that desmin is not essential for mechanical coupling of the costamere complex and the sarcomere lattice. Within the sarcomere lattice, significant differences in myofibrillar connectivity were revealed between passively deformed wild-type and desmin-null fibers. Connectivity in wild-type fibers was significantly greater compared to desmin-null fibers, demonstrating a significant functional connection between myofibrils that requires desmin. Passive mechanical analysis revealed that desmin may be partially responsible for regulating fiber volume, and consequently, fiber mechanical properties. Kinematic analysis of alpha-actinin strain fields revealed that knockout fibers transmitted less shear strain compared to wild-type fibers and experienced a slight increase in fiber volume. Finally, linkage of desmin intermediate filaments to muscle nuclei was strongly suggested based on extensive loss of nuclei positioning in the absence of desmin during passive fiber loading.
authors.affiliation: Departments of Bioengineering and Orthopaedics, Biomedical Sciences Graduate Group, University of California and Veterans Administration Medical Centers, San Diego, California 92161, USA.
authors.forename: Sameer B
authors.initials: SB
authors.lastname: Shah
authors.forename: Jennifer
authors.initials: J
authors.lastname: Davis
authors.forename: Noah
authors.initials: N
authors.lastname: Weisleder
authors.forename: Ioanna
authors.initials: I
authors.lastname: Kostavassili
authors.forename: Andrew D
authors.initials: AD
authors.lastname: McCulloch
authors.forename: Evelyn
authors.initials: E
authors.lastname: Ralston
authors.forename: Yassemi
authors.initials: Y
authors.lastname: Capetanaki
authors.forename: Richard L
authors.initials: RL
authors.lastname: Lieber
mesh_terms: D000185:Actinin / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D055592:Biophysical Phenomena; D001703:Biophysics; D002467:Cell Nucleus / Q000378:metabolism; D003893:Desmin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007382:Intermediate Filaments; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D015233:Models, Statistical; D008962:Models, Theoretical; D018482:Muscle, Skeletal / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D009210:Myofibrils / Q000737:chemistry; D009995:Osmosis; D010641:Phenotype; D012518:Sarcomeres / Q000378:metabolism; D013314:Stress, Mechanical; D016608:Talin / Q000378:metabolism
chemical_list: D003893:Desmin; D016608:Talin; D000185:Actinin