scholarly journals Titin isoform size is not correlated with thin filament length in rat skeletal muscle

2014 ◽  
Vol 5 ◽  
Author(s):  
Marion L. Greaser ◽  
Jonathan M. Pleitner
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Filament Length ◽  
Rat Skeletal Muscle

scholarly journals Thin filaments are not of uniform length in rat skeletal muscle.

1983 ◽  
Vol 96 (1) ◽  
pp. 100-103 ◽  
Author(s):  
L Traeger ◽  
M A Goldstein
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Fast Muscle ◽  
Filament Length ◽  
Rat Skeletal Muscle ◽  
Adult Rats ◽  
Thin Filaments ◽  
Filament Assembly ◽  
Old Rats ◽  
Two Stages

The variation in thin filament length was investigated in slow and fast muscle from adult and neonatal rats. Soleus (slow) muscle from adult, 3-, 7-, and 9-d-old rats, and extensor digitorum longus (EDL; fast) muscle from adult rats were serially cross-sectioned. The number of thin filaments per 0.06 microns2 (TF#) was counted for individual myofibrils followed from the H zone of one sarcomere, through the I-Z-I region, to the H zone of an adjacent sarcomere TF# was pooled by distance from the Z band or AI junction. In both adult muscles, thin filament length varied from 0.18 to 1.20 microns, with approximately 25% of the thin filaments less than 0.7 microns in length. In 7- and 9-d soleus, thin filament length ranged from 0.18 to 1.08 microns; except for the longest (0.18 to 1.20 microns) filaments, the distribution of thin filament lengths was similar to that in adult muscle. In 3-d soleus, thin filament length was more uniform, with less than 5% of the filaments shorter than 0.7 microns. In all neonatal muscles, there were approximately 15% fewer thin filaments per unit area as compared to adult muscles. We conclude: (a) In rat skeletal muscle, thin filaments are not of uniform length, ranging in length from 0.18 to 1.20 microns. (b) There may be two stages of thin filament assembly in neonatal muscle: between 3 and 7 d when short thin filaments may be preferentially or synthesized or inserted near the Z-band, and between 9 d and adult when thin filaments of all lengths may be synthesized or inserted into the myofibril.

scholarly journals Reduced thin filament length in nebulin-knockout skeletal muscle alters isometric contractile properties

2009 ◽  
Vol 296 (5) ◽  
pp. C1123-C1132 ◽  
Author(s):  
David S. Gokhin ◽  
Marie-Louise Bang ◽  
Jianlin Zhang ◽  
Ju Chen ◽  
Richard L. Lieber
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Expression Patterns ◽  
Nemaline Myopathy ◽  
Myosin Heavy Chain Isoforms ◽  
Filament Length ◽  
Force Transmission ◽  
Thin Filaments ◽  
Tension Properties ◽  
Tension Curves

Nebulin (NEB) is a large, rod-like protein believed to dictate actin thin filament length in skeletal muscle. NEB gene defects are associated with congenital nemaline myopathy. The functional role of NEB was investigated in gastrocnemius muscles from neonatal wild-type (WT) and NEB knockout (NEB-KO) mice, whose thin filaments have uniformly shorter lengths compared with WT mice. Isometric stress production in NEB-KO skeletal muscle was reduced by 27% compared with WT skeletal muscle on postnatal day 1 and by 92% on postnatal day 7, consistent with functionally severe myopathy. NEB-KO muscle was also more susceptible to a decline in stress production during a bout of 10 cyclic isometric tetani. Length-tension properties in NEB-KO muscle were altered in a manner consistent with reduced thin filament length, with length-tension curves from NEB-KO muscle demonstrating a 7.4% narrower functional range and an optimal length reduced by 0.13 muscle lengths. Expression patterns of myosin heavy chain isoforms and total myosin content did not account for the functional differences between WT and NEB-KO muscle. These data indicate that NEB is essential for active stress production, maintenance of functional integrity during cyclic activation, and length-tension properties consistent with a role in specifying normal thin filament length. Continued analysis of NEB's functional properties will strengthen the understanding of force transmission and thin filament length regulation in skeletal muscle and may provide insights into the molecular processes that give rise to nemaline myopathy.

scholarly journals Tropomodulin is associated with the free (pointed) ends of the thin filaments in rat skeletal muscle.

1993 ◽  
Vol 120 (2) ◽  
pp. 411-420 ◽  
Author(s):  
V M Fowler ◽  
M A Sussmann ◽  
P G Miller ◽  
B E Flucher ◽  
M P Daniels
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Spatial Organization ◽  
Membrane Skeleton ◽  
Filament Length ◽  
Human Erythrocyte Membrane ◽  
Thin Filaments ◽  
Muscle Tropomyosin ◽  
Immunofluorescence Labeling ◽  
Pointed End

The length and spatial organization of thin filaments in skeletal muscle sarcomeres are precisely maintained and are essential for efficient muscle contraction. While the major structural components of skeletal muscle sarcomeres have been well characterized, the mechanisms that regulate thin filament length and spatial organization are not well understood. Tropomodulin is a new, 40.6-kD tropomyosin-binding protein from the human erythrocyte membrane skeleton that binds to one end of erythrocyte tropomyosin and blocks head-to-tail association of tropomyosin molecules along actin filaments. Here we show that rat psoas skeletal muscle contains tropomodulin based on immunoreactivity, identical apparent mobility on SDS gels, and ability to bind muscle tropomyosin. Results from immunofluorescence labeling of isolated myofibrils at resting and stretched lengths using anti-erythrocyte tropomodulin antibodies indicate that tropomodulin is localized at or near the free (pointed) ends of the thin filaments; this localization is not dependent on the presence of myosin thick filaments. Immunoblotting of supernatants and pellets obtained after extraction of myosin from myofibrils also indicates that tropomodulin remains associated with the thin filaments. 1.2-1.6 copies of muscle tropomodulin are present per thin filament in myofibrils, supporting the possibility that one or two tropomodulin molecules may be associated with the two terminal tropomyosin molecules at the pointed end of each thin filament. Although a number of proteins are associated with the barbed ends of the thin filaments at the Z disc, tropomodulin is the first protein to be specifically located at or near the pointed ends of the thin filaments. We propose that tropomodulin may cap the tropomyosin polymers at the pointed end of the thin filament and play a role in regulating thin filament length.

scholarly journals Tropomodulin 1 directly controls thin filament length in both wild-type and tropomodulin 4-deficient skeletal muscle

Development ◽  
2015 ◽  
Vol 142 (24) ◽  
pp. 4351-4362 ◽  
Author(s):  
D. S. Gokhin ◽  
J. Ochala ◽  
A. A. Domenighetti ◽  
V. M. Fowler
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Filament Length ◽  
Wild Type

scholarly journals Thin Filament Length in Mouse Skeletal Muscle and its Relationship to Differential Splicing of Nebulin

2011 ◽  
Vol 100 (3) ◽  
pp. 587a ◽  
Author(s):  
Danielle Buck ◽  
Paola Tonino ◽  
Adam Hoying ◽  
Henk Granzier
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Filament Length ◽  
Differential Splicing ◽  
Mouse Skeletal Muscle

Transition in the thin-filament arrangement in rat skeletal muscle

1983 ◽  
Vol 4 (3) ◽  
pp. 353-366 ◽  
Author(s):  
Laurel Traeger ◽  
John M. Mackenzie ◽  
Henry F. Epstein ◽  
Margaret A. Goldstein
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Rat Skeletal Muscle

scholarly journals Tropomodulin 1 directly controls thin filament length in both wild-type and tropomodulin 4-deficient skeletal muscle

2016 ◽  
Vol 129 (1) ◽  
pp. e1.2-e1.2 ◽  
Author(s):  
David S. Gokhin ◽  
Julien Ochala ◽  
Andrea A. Domenighetti ◽  
Velia M. Fowler
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Filament Length ◽  
Wild Type

scholarly journals New Insights into the Structural Roles of Nebulin in Skeletal Muscle

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Coen A. C. Ottenheijm ◽  
Henk Granzier
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Force Production ◽  
Nemaline Myopathy ◽  
Structure And Function ◽  
Filament Length ◽  
Thin Filaments ◽  
Muscle Structure ◽  
And Function

One important feature of muscle structure and function that has remained relatively obscure is the mechanism that regulates thin filament length. Filament length is an important aspect of muscle function as force production is proportional to the amount of overlap between thick and thin filaments. Recent advances, due in part to the generation of nebulin KO models, reveal that nebulin plays an important role in the regulation of thin filament length. Another structural feature of skeletal muscle that is not well understood is the mechanism involved in maintaining the regular lateral alignment of adjacent sarcomeres, that is, myofibrillar connectivity. Recent studies indicate that nebulin is part of a protein complex that mechanically links adjacent myofibrils. Thus, novel structural roles of nebulin in skeletal muscle involve the regulation of thin filament length and maintaining myofibrillar connectivity. When these functions of nebulin are absent, muscle weakness ensues, as is the case in patients with nemaline myopathy with mutations in nebulin. Here we review these new insights in the role of nebulin in skeletal muscle structure.

scholarly journals Thin-filament length correlates with fiber type in human skeletal muscle

2012 ◽  
Vol 302 (3) ◽  
pp. C555-C565 ◽  
Author(s):  
David S. Gokhin ◽  
Nancy E. Kim ◽  
Sarah A. Lewis ◽  
Heinz R. Hoenecke ◽  
Darryl D. D'Lima ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Thin Filament ◽  
Fiber Type ◽  
Pectoralis Major Muscle ◽  
Thick Filament ◽  
Fiber Types ◽  
Filament Length ◽  
Orthopedic Rehabilitation

Force production in skeletal muscle is proportional to the amount of overlap between the thin and thick filaments, which, in turn, depends on their lengths. Both thin- and thick-filament lengths are precisely regulated and uniform within a myofibril. While thick-filament lengths are essentially constant across muscles and species (∼1.65 μm), thin-filament lengths are highly variable both across species and across muscles of a single species. Here, we used a high-resolution immunofluorescence and image analysis technique (distributed deconvolution) to directly test the hypothesis that thin-filament lengths vary across human muscles. Using deltoid and pectoralis major muscle biopsies, we identified thin-filament lengths that ranged from 1.19 ± 0.08 to 1.37 ± 0.04 μm, based on tropomodulin localization with respect to the Z-line. Tropomodulin localized from 0.28 to 0.47 μm further from the Z-line than the NH2-terminus of nebulin in the various biopsies, indicating that human thin filaments have nebulin-free, pointed-end extensions that comprise up to 34% of total thin-filament length. Furthermore, thin-filament length was negatively correlated with the percentage of type 2X myosin heavy chain within the biopsy and shorter in type 2X myosin heavy chain-positive fibers, establishing the existence of a relationship between thin-filament lengths and fiber types in human muscle. Together, these data challenge the widely held assumption that human thin-filament lengths are constant. Our results also have broad relevance to musculoskeletal modeling, surgical reattachment of muscles, and orthopedic rehabilitation.

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