Myosin heavy chain composition of single fibres from normal human muscle.
Ontology highlight
ABSTRACT:
SUBMITTER: Biral D
PROVIDER: S-EPMC1148850 | biostudies-other | 1988 Feb
REPOSITORIES: biostudies-other
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Project description:The myosin heavy-chain (MHC) isoform pattern was studied by biochemical methods in the slow-twitch (soleus) and fast-twitch (gastrocnemius) muscles of adult rats during atrophy after tenotomy and recovery after tendon regeneration. The tenotomized slow muscle atrophied more than the tenotomized fast muscle. During the 12 days after tenotomy the total MHC content decreased by about 85% in the slow muscle, and only by about 35% in the fast muscle. In the slow muscle the ratio of MHC-1 to MHC-2A(2S) remained almost unchanged, showing that similar diminution of both isoforms occurs. In the fast muscle the MHC-2A/MHC-2B ratio decreased, showing the loss of MHC-2A mainly. After tendon regeneration, the slow muscle recovered earlier than the fast muscle. Full recovery of the muscles was not observed until up to 4 months later. The embryonic MHC, which seems to be expressed in denervated adult muscle fibres, was not detected by immunoblotting in the tenotomized muscles during either atrophy or recovery after tendon regeneration. The influence of tenotomy and denervation on expression of the MHC isoforms is compared. The results show that: (a) MHC-1 and MHC-2A(2S) are very sensitive to tenotomy, whereas MHC-2B is much less sensitive; (b) expression of the embryonic MHC in adult muscle seems to be inhibited by the intact neuromuscular junction.
| S-EPMC1130913 | biostudies-other
Project description:Hybridization in situ with riboprobes to the myosin heavy-chain slow isoform showed that, in the rat soleus muscle, the myosin heavy-chain mRNA was distributed throughout the myofibres. There was greater density of autoradiographic grains in the subsarcolemmal regions of the fibres, but there was also a considerable number of grains in the core myofibrillar region of the fibres. Microdensitometry showed that the grain density in the myofibrillar region was approximately half that in the subsarcolemmal rim; this would correspond to some 70% of the mRNA being present in the myofibrillar region. The results are consistent with the hypothesis that myosin is synthesized on polyribosomes present in the intermyofibrillar cytoplasm.
| S-EPMC1151581 | biostudies-other
Project description:Protein arginylation is a posttranslational modification with an emerging global role in the regulation of actin cytoskeleton. To test the role of arginylation in the skeletal muscle, we generated a mouse model with Ate1 deletion driven by the skeletal muscle-specific creatine kinase (Ckmm) promoter. Ckmm-Ate1 mice were viable and outwardly normal; however, their skeletal muscle strength was significantly reduced in comparison to controls. Mass spectrometry of isolated skeletal myofibrils showed a limited set of proteins, including myosin heavy chain, arginylated on specific sites. Atomic force microscopy measurements of contractile strength in individual myofibrils and isolated myosin filaments from these mice showed a significant reduction of contractile forces, which, in the case of myosin filaments, could be fully rescued by rearginylation with purified Ate1. Our results demonstrate that arginylation regulates force production in muscle and exerts a direct effect on muscle strength through arginylation of myosin.
| S-EPMC4126752 | biostudies-literature
Project description:PurposeMuscle contractile phenotype is affected during immobilization. Myosin heavy chain (MHC) isoforms are the major determinant of the muscle contractile phenotype. We therefore sought to evaluate the effects of muscle immobilization on both the MHC composition at single-fibre level and the mitogen-activated protein kinases (MAPK), a family of intracellular signaling pathways involved in the stress-induced muscle plasticity.MethodsThe distal tendon of female Wistar rat Peroneus Longus (PL) was cut and fixed to the adjacent bone at neutral muscle length. Four weeks after the surgery, immobilized and contralateral PL were dissociated and the isolated fibres were sampled to determine MHC composition. Protein kinase 38 (p38), extracellular signal-regulated kinases (ERK1/2), and c-Jun- NH2-terminal kinase (JNK) phosphorylations were measured in 6- and 15-day immobilized and contralateral PL.ResultsMHC distribution in immobilized PL was as follows: I = 0%, IIa = 11.8 ± 2.8%, IIx = 53.0 ± 6.1%, IIb = 35.3 ± 7.3% and I = 6.1 ± 3.9%, IIa = 22.1 ± 3.4%, IIx = 46.6 ± 4.5%, IIb = 25.2 ± 6.6% in contralateral muscle. The MHC composition in immobilized muscle is consistent with a faster contractile phenotype according to the Hill's model of the force-velocity relationship. Immobilized and contralateral muscles displayed a polymorphism index of 31.1% (95% CI 26.1-36.0) and 39.3% (95% CI 37.0-41.5), respectively. Significant increases in p38 and JNK phosphorylation were observed following 6 and 15 days of immobilization.ConclusionsSingle muscle immobilization at neutral length induces a shift of MHC composition toward a faster contractile phenotype and decreases the polymorphic profile of single fibres. Activation of p38 and JNK could be a potential mechanism involved in these contractile phenotype modifications during muscle immobilization.
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Project description:We show that a 2.6kb fragment of the muscle myosin heavy-chain gene (Mhc) of Drosophila melanogaster (containing 458 base pairs of upstream sequence, the first exon, the first intron and the beginning of the second exon) drives expression in all muscles. Comparison of the minimal promoter to Mhc genes of 10 Drosophila species identified putative regulatory elements in the upstream region and in the first intron. The first intron is required for expression in four small cells of the tergal depressor of the trochanter (jump) muscle and in the indirect flight muscle. The 3'-end of this intron is important for Mhc transcription in embryonic body wall muscle and contains AT-rich elements that are protected from DNase I digestion by nuclear proteins of Drosophila embryos. Sequences responsible for expression in embryonic, adult body wall and adult head muscles are present both within and outside the intron. Elements important for expression in leg muscles and in the large cells of the jump muscle flank the intron. We conclude that multiple transcriptional regulatory elements are responsible for Mhc expression in specific sets of Drosophila muscles.
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Project description:Myosin heavy chain-embryonic (MyHC-emb) is a skeletal muscle-specific contractile protein expressed during muscle development. Mutations in MYH3, the gene encoding MyHC-emb, lead to Freeman-Sheldon and Sheldon-Hall congenital contracture syndromes. Here, we characterize the role of MyHC-emb during mammalian development using targeted mouse alleles. Germline loss of MyHC-emb leads to neonatal and postnatal alterations in muscle fiber size, fiber number, fiber type and misregulation of genes involved in muscle differentiation. Deletion of Myh3 during embryonic myogenesis leads to the depletion of the myogenic progenitor cell pool and an increase in the myoblast pool, whereas fetal myogenesis-specific deletion of Myh3 causes the depletion of both myogenic progenitor and myoblast pools. We reveal that the non-cell-autonomous effect of MyHC-emb on myogenic progenitors and myoblasts is mediated by the fibroblast growth factor (FGF) signaling pathway, and exogenous FGF rescues the myogenic differentiation defects upon loss of MyHC-emb function in vitro Adult Myh3 null mice exhibit scoliosis, a characteristic phenotype exhibited by individuals with Freeman-Sheldon and Sheldon-Hall congenital contracture syndrome. Thus, we have identified MyHC-emb as a crucial myogenic regulator during development, performing dual cell-autonomous and non-cell-autonomous functions.This article has an associated 'The people behind the papers' interview.
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Project description:mRNA from 4 different muscles from control and Myosin heavy chain-embryonic knockout neonate mice were sequenced.
2020-03-08 | GSE100331 | GEO
Project description:To assess myosin heavy chain (MHC) plasticity in aging skeletal muscle with aerobic exercise training, MHC composition was measured at the messenger RNA (mRNA) level and protein level in mixed-muscle homogenates and single myofibers. Muscle samples were obtained from eight nonexercising women (70 ± 2 years) before and after 12 weeks of training (20-45 minutes of cycle exercise per session at 60%-80% heart rate reserve, three to four sessions per week). Training elevated MHC I mRNA (p < .10) and protein (p < .05) in mixed-muscle (54% ± 4% to 61% ± 2%) and single myofibers (42% ± 4% to 52% ± 3%). The increase in MHC I protein was positively correlated (p < .05) with improvements in whole muscle power. Training resulted in a general downregulation of MHC IIa and IIx at the mRNA and protein levels. The training-induced increase in MHC I protein and mRNA demonstrates the maintenance of skeletal muscle plasticity with aging. Furthermore, these data suggest that a shift toward an oxidative MHC phenotype may be beneficial for metabolic and functional health in older individuals.
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Project description:1. Six adult rabbit soleus muscles were analysed by isolating histochemically identified fibre pieces from freeze-dried serial cross-sections. 2. By the use of this method, four fibre types (I, IC, IIC and IIA) were identified and analysed micro-electrophoretically. 3. Type I fibres contained the slow myosin heavy chain HCI and the slow myosin light chains LC1s and LC2s. 4. Type IIA fibres contained the fast myosin HCIIa with the fast light chains and, in addition, either LC1s or both LC1s and LC2s. 5. The C fibres (IC and IIC) represented intermediate populations between types I and IIC (IC) and between IC and IIA (IIC). They contained varied ratios of HCI/HCIIa with both sets of fast and slow light chains. With regard to myosin composition and isoforms of other myofibrillar proteins (M- and C-proteins, alpha-tropomyosin, troponin I), IC fibres resembled type I and IIC fibres resembled type IIA. 6. The presence of various myosin light and heavy chains within a specific fibre suggests a multiplicity of isomyosins. Without consideration of LC1sa and LC1sb differences, at least 54 possible isomyosins can be derived: type I fibres contain one isomyosin, types IC and IIC 54 possible isomyosins, and type IIA up to 18.
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Project description:Avian myogenesis is partly characterized by commitment of distinct myoblast cell lineages to the formation of specific muscle fiber types. Previous studies have identified the transcription factor EMX2 as a regulator of slow myosin heavy chain 2 (MyHC2) gene expression in fast/slow primary muscle fibers. We report here the interaction of EMX2 with the slow MyHC2 transcriptional regulatory region in fast/slow embryonic muscle fibers. Promoter activity and electromobility shift assays localized the site of interaction of EMX2 with the slow MyHC2 gene within a defined binding site located between 3336 and 3326bp from the 3' end of the cloned slow MyHC2 DNA containing the transcriptional regulatory region. Using clonally-derived myoblasts stably committed to the formation of fast/slow muscle fibers, we also report the effect of altered EMX2 gene expression on genome-wide gene expression within these myoblasts. Increased EMX2 gene expression in fast/slow myoblasts caused altered gene expression of 1185 genes, indicating that EMX2 plays a central role in the gene expression profile of embryonic myoblasts.
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