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Chiang WY, Yu HW, Wu MC, Huang YM, Chen YQ, Lin JW, Liu YW, You LR, Chiou A, Kuo JC. Matrix mechanics regulates muscle regeneration by modulating kinesin-1 activity. Biomaterials 2024; 308:122551. [PMID: 38593710 DOI: 10.1016/j.biomaterials.2024.122551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 03/22/2024] [Accepted: 03/25/2024] [Indexed: 04/11/2024]
Abstract
Sarcopenia, a prevalent muscle disease characterized by muscle mass and strength reduction, is associated with impaired skeletal muscle regeneration. However, the influence of the biomechanical properties of sarcopenic skeletal muscle on the efficiency of the myogenic program remains unclear. Herein, we established a mouse model of sarcopenia and observed a reduction in stiffness within the sarcopenic skeletal muscle in vivo. To investigate whether the biomechanical properties of skeletal muscle directly impact the myogenic program, we established an in vitro system to explore the intrinsic mechanism involving matrix stiffness control of myogenic differentiation. Our findings identify the microtubule motor protein, kinesin-1, as a mechano-transduction hub that senses and responds to matrix stiffness, crucial for myogenic differentiation and muscle regeneration. Specifically, kinesin-1 activity is positively regulated by stiff matrices, facilitating its role in transporting mitochondria and enhancing translocation of the glucose transporter GLUT4 to the cell surface for glucose uptake. Conversely, the softer matrices significantly suppress kinesin-1 activity, leading to the accumulation of mitochondria around nuclei and hindering glucose uptake by inhibiting GLUT4 membrane translocation, consequently impairing myogenic differentiation. The insights gained from the in-vitro system highlight the mechano-transduction significance of kinesin-1 motor proteins in myogenic differentiation. Furthermore, our study confirms that enhancing kinesin-1 activity in the sarcopenic mouse model restores satellite cell expansion, myogenic differentiation, and muscle regeneration. Taken together, our findings provide a potential target for improving muscle regeneration in sarcopenia.
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Affiliation(s)
- Wan-Yu Chiang
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Helen Wenshin Yu
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Ming-Chung Wu
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Yi-Man Huang
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Yin-Quan Chen
- Cancer and Immunology Research Center, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Jong-Wei Lin
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Yen-Wenn Liu
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Li-Ru You
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Arthur Chiou
- Institute of Biophotonics, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Jean-Cheng Kuo
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan; Cancer and Immunology Research Center, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan.
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2
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Singh AK, Rai A, Weber A, Posern G. miRNA mediated downregulation of cyclase-associated protein 1 (CAP1) is required for myoblast fusion. Front Cell Dev Biol 2022; 10:899917. [PMID: 36246999 PMCID: PMC9562714 DOI: 10.3389/fcell.2022.899917] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Accepted: 09/14/2022] [Indexed: 11/13/2022] Open
Abstract
Myoblast fusion is essential for the formation, growth, and regeneration of skeletal muscle, but the molecular mechanisms that govern fusion and myofiber formation remain poorly understood. Past studies have shown an important role of the actin cytoskeleton and actin regulators in myoblast fusion. The Cyclase-Associated Proteins (CAP) 1 and 2 recently emerged as critical regulators of actin treadmilling in higher eukaryotes including mammals. Whilst the role of CAP2 in skeletal muscle development and function is well characterized, involvement of CAP1 in this process remains elusive. Here we report that CAP1, plays a critical role in cytoskeletal remodeling during myoblast fusion and formation of myotubes. Cap1 mRNA and protein are expressed in both murine C2C12 and human LHCN-M2 myoblasts, but their abundance decreases during myogenic differentiation. Perturbing the temporally controlled expression of CAP1 by overexpression or CRISPR-Cas9 mediated knockout impaired actin rearrangement, myoblast alignment, expression of profusion molecules, differentiation into multinucleated myotubes, and myosin heavy chain expression. Endogenous Cap1 expression is post-transcriptionally downregulated during differentiation by canonical myomiRs miR-1, miR-133, and miR-206, which have conserved binding sites at the 3′ UTR of the Cap1 mRNA. Deletion of the endogenous 3′ UTR by CRISPR-Cas9 in C2C12 cells phenocopies overexpression of CAP1 by inhibiting myotube formation. Our findings implicates Cap1 and its myomiR-mediated downregulation in the myoblast fusion process and the generation of skeletal muscle.
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Affiliation(s)
- Anurag Kumar Singh
- Institute for Physiological Chemistry, Medical Faculty, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
- Department of Internal Medicine I, University Hospital Halle, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
- *Correspondence: Anurag Kumar Singh, ; Guido Posern,
| | - Amrita Rai
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Anja Weber
- Institute for Physiological Chemistry, Medical Faculty, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Guido Posern
- Institute for Physiological Chemistry, Medical Faculty, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
- *Correspondence: Anurag Kumar Singh, ; Guido Posern,
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3
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Grifell-Junyent M, Baum JF, Välimets S, Herrmann A, Paulusma CC, López-Marqués RL, Günther Pomorski T. CDC50A is required for aminophospholipid transport and cell fusion in mouse C2C12 myoblasts. J Cell Sci 2022; 135:jcs258649. [PMID: 34664668 PMCID: PMC10405909 DOI: 10.1242/jcs.258649] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 09/02/2021] [Indexed: 11/20/2022] Open
Abstract
Myoblast fusion is essential for the formation of multinucleated muscle fibers and is promoted by transient changes in the plasma membrane lipid distribution. However, little is known about the lipid transporters regulating these dynamic changes. Here, we show that proliferating myoblasts exhibit an aminophospholipid flippase activity that is downregulated during differentiation. Deletion of the P4-ATPase flippase subunit CDC50A (also known as TMEM30A) results in loss of the aminophospholipid flippase activity and compromises actin remodeling, RAC1 GTPase membrane targeting and cell fusion. In contrast, deletion of the P4-ATPase ATP11A affects aminophospholipid uptake without having a strong impact on cell fusion. Our results demonstrate that myoblast fusion depends on CDC50A and may involve multiple CDC50A-dependent P4-ATPases that help to regulate actin remodeling.
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Affiliation(s)
- Marta Grifell-Junyent
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Julia F. Baum
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Silja Välimets
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Andreas Herrmann
- Institut für Biologie, Molekulare Biophysik, IRI Life Sciences, Humboldt-Universität zu Berlin, Invalidenstrasse 42, 10115 Berlin, Germany
| | - Coen C. Paulusma
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology and Metabolism, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Rosa L. López-Marqués
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Thomas Günther Pomorski
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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4
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Szabo K, Varga D, Vegh AG, Liu N, Xiao X, Xu L, Dux L, Erdelyi M, Rovo L, Keller-Pinter A. Syndecan-4 affects myogenesis via Rac1-mediated actin remodeling and exhibits copy-number amplification and increased expression in human rhabdomyosarcoma tumors. Cell Mol Life Sci 2022; 79:122. [PMID: 35128576 PMCID: PMC8818642 DOI: 10.1007/s00018-021-04121-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 12/14/2021] [Accepted: 12/29/2021] [Indexed: 12/18/2022]
Abstract
Skeletal muscle demonstrates a high degree of regenerative capacity repeating the embryonic myogenic program under strict control. Rhabdomyosarcoma is the most common sarcoma in childhood and is characterized by impaired muscle differentiation. In this study, we observed that silencing the expression of syndecan-4, the ubiquitously expressed transmembrane heparan sulfate proteoglycan, significantly enhanced myoblast differentiation, and fusion. During muscle differentiation, the gradually decreasing expression of syndecan-4 allows the activation of Rac1, thereby mediating myoblast fusion. Single-molecule localized superresolution direct stochastic optical reconstruction microscopy (dSTORM) imaging revealed nanoscale changes in actin cytoskeletal architecture, and atomic force microscopy showed reduced elasticity of syndecan-4-knockdown cells during fusion. Syndecan-4 copy-number amplification was observed in 28% of human fusion-negative rhabdomyosarcoma tumors and was accompanied by increased syndecan-4 expression based on RNA sequencing data. Our study suggests that syndecan-4 can serve as a tumor driver gene in promoting rabdomyosarcoma tumor development. Our results contribute to the understanding of the role of syndecan-4 in skeletal muscle development, regeneration, and tumorigenesis.
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5
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Hammers DW, Hart CC, Matheny MK, Heimsath EG, Lee YI, Hammer JA, Cheney RE, Sweeney HL. Filopodia powered by class x myosin promote fusion of mammalian myoblasts. eLife 2021; 10:e72419. [PMID: 34519272 PMCID: PMC8500716 DOI: 10.7554/elife.72419] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Accepted: 09/13/2021] [Indexed: 12/30/2022] Open
Abstract
Skeletal muscle fibers are multinucleated cellular giants formed by the fusion of mononuclear myoblasts. Several molecules involved in myoblast fusion have been discovered, and finger-like projections coincident with myoblast fusion have also been implicated in the fusion process. The role of these cellular projections in muscle cell fusion was investigated herein. We demonstrate that these projections are filopodia generated by class X myosin (Myo10), an unconventional myosin motor protein specialized for filopodia. We further show that Myo10 is highly expressed by differentiating myoblasts, and Myo10 ablation inhibits both filopodia formation and myoblast fusion in vitro. In vivo, Myo10 labels regenerating muscle fibers associated with Duchenne muscular dystrophy and acute muscle injury. In mice, conditional loss of Myo10 from muscle-resident stem cells, known as satellite cells, severely impairs postnatal muscle regeneration. Furthermore, the muscle fusion proteins Myomaker and Myomixer are detected in myoblast filopodia. These data demonstrate that Myo10-driven filopodia facilitate multinucleated mammalian muscle formation.
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MESH Headings
- Animals
- Cell Differentiation
- Cell Fusion
- Cell Line
- Cell Proliferation
- Disease Models, Animal
- Humans
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mice, Inbred C57BL
- Mice, Inbred mdx
- Mice, Knockout
- Muscle Development
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Muscle Proteins/genetics
- Muscle Proteins/metabolism
- Muscular Dystrophy, Duchenne/genetics
- Muscular Dystrophy, Duchenne/metabolism
- Muscular Dystrophy, Duchenne/pathology
- Myoblasts, Skeletal/metabolism
- Myoblasts, Skeletal/pathology
- Myosins/genetics
- Myosins/metabolism
- Pseudopodia/genetics
- Pseudopodia/metabolism
- Regeneration
- Satellite Cells, Skeletal Muscle/metabolism
- Satellite Cells, Skeletal Muscle/pathology
- Time Factors
- Mice
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Affiliation(s)
- David W Hammers
- Department of Pharmacology & Therapeutics, University of Florida College of MedicineGainesvilleUnited States
- University of Florida Myology InstituteGainesvilleUnited States
| | - Cora C Hart
- Department of Pharmacology & Therapeutics, University of Florida College of MedicineGainesvilleUnited States
- University of Florida Myology InstituteGainesvilleUnited States
| | - Michael K Matheny
- Department of Pharmacology & Therapeutics, University of Florida College of MedicineGainesvilleUnited States
- University of Florida Myology InstituteGainesvilleUnited States
| | - Ernest G Heimsath
- Department of Cell Biology & Physiology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of MedicineChapel HillUnited States
| | - Young il Lee
- Department of Pharmacology & Therapeutics, University of Florida College of MedicineGainesvilleUnited States
- University of Florida Myology InstituteGainesvilleUnited States
| | - John A Hammer
- Cell Biology and Physiology Center, National Heart, Lung and Blood InstituteBethesdaUnited States
| | - Richard E Cheney
- Department of Cell Biology & Physiology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of MedicineChapel HillUnited States
| | - H Lee Sweeney
- Department of Pharmacology & Therapeutics, University of Florida College of MedicineGainesvilleUnited States
- University of Florida Myology InstituteGainesvilleUnited States
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Dexamethasone accelerates muscle regeneration by modulating kinesin-1-mediated focal adhesion signals. Cell Death Discov 2021; 7:35. [PMID: 33597503 PMCID: PMC7889929 DOI: 10.1038/s41420-021-00412-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/27/2020] [Accepted: 10/30/2020] [Indexed: 01/11/2023] Open
Abstract
During differentiation, skeletal muscle develops mature multinucleated muscle fibers, which could contract to exert force on a substrate. Muscle dysfunction occurs progressively in patients with muscular dystrophy, leading to a loss of the ability to walk and eventually to death. The synthetic glucocorticoid dexamethasone (Dex) has been used therapeutically to treat muscular dystrophy by an inhibition of inflammation, followed by slowing muscle degeneration and stabilizing muscle strength. Here, in mice with muscle injury, we found that Dex significantly promotes muscle regeneration via promoting kinesin-1 motor activity. Nevertheless, how Dex promotes myogenesis through kinesin-1 motors remains unclear. We found that Dex directly increases kinesin-1 motor activity, which is required for the expression of a myogenic marker (muscle myosin heavy chain 1/2), and also for the process of myoblast fusion and the formation of polarized myotubes. Upon differentiation, kinesin-1 mediates the recruitment of integrin β1 onto microtubules allowing delivery of the protein into focal adhesions. Integrin β1-mediated focal adhesion signaling then guides myoblast fusion towards a polarized morphology. By imposing geometric constrains via micropatterns, we have proved that cell adhesion is able to rescue the defects caused by kinesin-1 inhibition during the process of myogenesis. These discoveries reveal a mechanism by which Dex is able to promote myogenesis, and lead us towards approaches that are more efficient in improving skeletal muscle regeneration.
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7
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Vajanthri K, Sidu R, Mahto S. Micropatterning and Alignment of Skeletal Muscle Myoblasts Using Microflowed Plasma Process. Ing Rech Biomed 2020. [DOI: 10.1016/j.irbm.2019.08.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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8
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Actomyosin contractility scales with myoblast elongation and enhances differentiation through YAP nuclear export. Sci Rep 2019; 9:15565. [PMID: 31664178 PMCID: PMC6820726 DOI: 10.1038/s41598-019-52129-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 10/10/2019] [Indexed: 01/14/2023] Open
Abstract
Skeletal muscle fibers are formed by the fusion of mononucleated myoblasts into long linear myotubes, which differentiate and reorganize into multinucleated myofibers that assemble in bundles to form skeletal muscles. This fundamental process requires the elongation of myoblasts into a bipolar shape, although a complete understanding of the mechanisms governing skeletal muscle fusion is lacking. To address this question, we consider cell aspect ratio, actomyosin contractility and the Hippo pathway member YAP as potential regulators of the fusion of myoblasts into myotubes. Using fibronectin micropatterns of different geometries and traction force microscopy, we investigated how myoblast elongation affects actomyosin contractility. Our findings indicate that cell elongation enhances actomyosin contractility in myoblasts, which regulate their actin network to their spreading area. Interestingly, we found that the contractility of cell pairs increased after their fusion and raise on elongated morphologies. Furthermore, our findings indicate that myoblast elongation modulates nuclear orientation and triggers cytoplasmic localization of YAP, increasing evidence that YAP is a key regulator of mechanotransduction in myoblasts. Taken together, our findings support a mechanical model where actomyosin contractility scales with myoblast elongation and enhances the differentiation of myoblasts into myotubes through YAP nuclear export.
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9
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Dephosphorylation of HDAC4 by PP2A-Bδ unravels a new role for the HDAC4/MEF2 axis in myoblast fusion. Cell Death Dis 2019; 10:512. [PMID: 31273193 PMCID: PMC6609635 DOI: 10.1038/s41419-019-1743-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 06/03/2019] [Accepted: 06/11/2019] [Indexed: 11/14/2022]
Abstract
Muscle formation is controlled by a number of key myogenic transcriptional regulators that govern stage-specific gene expression programs and act as terminal effectors of intracellular signaling pathways. To date, the role of phosphatases in the signaling cascades instructing muscle development remains poorly understood. Here, we show that a specific PP2A-B55δ holoenzyme is necessary for skeletal myogenesis. The primary role of PP2A-B55δ is to dephosphorylate histone deacetylase 4 (HDAC4) following myocyte differentiation and ensure repression of Myocyte enhancer factor 2D (MEF2D)-dependent gene expression programs during myogenic fusion. As a crucial HDAC4/MEF2D target gene that governs myocyte fusion, we identify ArgBP2, an upstream inhibitor of Abl, which itself is a repressor of CrkII signaling. Consequently, cells lacking PP2A-B55δ show upregulation of ArgBP2 and hyperactivation of CrkII downstream effectors, including Rac1 and FAK, precluding cytoskeletal and membrane rearrangements associated with myoblast fusion. Both in vitro and in zebrafish, loss-of-function of PP2A-B55δ severely impairs fusion of myocytes and formation of multinucleated muscle fibers, without affecting myoblast differentiation. Taken together, our results establish PP2A-B55δ as the first protein phosphatase to be involved in myoblast fusion and suggest that reversible phosphorylation of HDAC4 may coordinate differentiation and fusion events during myogenesis.
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10
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Vajanthri KY, Sidu RK, Poddar S, Singh AK, Mahto SK. Combined substrate micropatterning and FFT analysis reveals myotube size control and alignment by contact guidance. Cytoskeleton (Hoboken) 2019; 76:269-285. [DOI: 10.1002/cm.21527] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 04/23/2019] [Accepted: 05/02/2019] [Indexed: 12/30/2022]
Affiliation(s)
- Kiran Yellappa Vajanthri
- Tissue Engineering and Biomicrofluidics Laboratory, School of Biomedical EngineeringIndian Institute of Technology (Banaras Hindu University) Varanasi Uttar Pradesh India
| | - Rakesh Kumar Sidu
- Tissue Engineering and Biomicrofluidics Laboratory, School of Biomedical EngineeringIndian Institute of Technology (Banaras Hindu University) Varanasi Uttar Pradesh India
| | - Suruchi Poddar
- Tissue Engineering and Biomicrofluidics Laboratory, School of Biomedical EngineeringIndian Institute of Technology (Banaras Hindu University) Varanasi Uttar Pradesh India
| | - Ashish Kumar Singh
- School of Biochemical EngineeringIndian Institute of Technology (Banaras Hindu University) Varanasi Uttar Pradesh India
| | - Sanjeev Kumar Mahto
- Tissue Engineering and Biomicrofluidics Laboratory, School of Biomedical EngineeringIndian Institute of Technology (Banaras Hindu University) Varanasi Uttar Pradesh India
- Center for Advanced Biomaterials and Tissue EngineeringIndian Institute of Technology (Banaras Hindu University) Varanasi Uttar Pradesh India
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11
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Blondelle J, Tallapaka K, Seto JT, Ghassemian M, Clark M, Laitila JM, Bournazos A, Singer JD, Lange S. Cullin-3 dependent deregulation of ACTN1 represents a new pathogenic mechanism in nemaline myopathy. JCI Insight 2019; 5:125665. [PMID: 30990797 PMCID: PMC6542616 DOI: 10.1172/jci.insight.125665] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 04/11/2019] [Indexed: 12/11/2022] Open
Abstract
Nemaline myopathy is a congenital neuromuscular disorder characterized by muscle weakness, fiber atrophy and presence of nemaline bodies within myofibers. However, the understanding of underlying pathomechanisms is lacking. Recently, mutations in KBTBD13, KLHL40 and KLHL41, three substrate adaptors for the E3-ubiquitin ligase Cullin-3, have been associated with early-onset nemaline myopathies. We hypothesized that deregulation of Cullin-3 and its muscle protein substrates may be responsible for the disease development. Using Cullin-3 knockout mice, we identified accumulation of non-muscle alpha-Actinins (ACTN1 and ACTN4) in muscles of these mice, which we also observed in KBTBD13 patients. Our data reveal that proper regulation of Cullin-3 activity and ACTN1 levels is essential for normal muscle and neuromuscular junction development. While ACTN1 is naturally downregulated during myogenesis, its overexpression in C2C12 myoblasts triggered defects in fusion, myogenesis and acetylcholine receptor clustering; features that we characterized in Cullin-3 deficient mice. Taken together, our data highlight the importance for Cullin-3 mediated degradation of ACTN1 for muscle development, and indicate a new pathomechanism for the etiology of myopathies seen in Cullin-3 knockout mice and nemaline myopathy patients.
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Affiliation(s)
- Jordan Blondelle
- Division of Cardiology, School of Medicine, UCSD, La Jolla, California, USA
| | - Kavya Tallapaka
- Division of Cardiology, School of Medicine, UCSD, La Jolla, California, USA
| | - Jane T. Seto
- Neuromuscular Research, Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Parkville, Victoria, Australia
| | - Majid Ghassemian
- Department of Chemistry and Biochemistry. UCSD, La Jolla, California, USA
| | - Madison Clark
- Division of Cardiology, School of Medicine, UCSD, La Jolla, California, USA
| | - Jenni M. Laitila
- Folkhälsan Research Center and Medicum, University of Helsinki, Helsinki, Finland
| | - Adam Bournazos
- Kids Neuroscience Centre, Kids Research, Children’s Hospital at Westmead, Sydney, New South Wales, Australia
- Discipline of Child and Adolescent Health, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Jeffrey D. Singer
- Department of Biology, Portland State University, Portland, Oregon, USA
| | - Stephan Lange
- Division of Cardiology, School of Medicine, UCSD, La Jolla, California, USA
- Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden
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12
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Myotube elasticity of an amyotrophic lateral sclerosis mouse model. Sci Rep 2018; 8:5917. [PMID: 29650983 PMCID: PMC5897453 DOI: 10.1038/s41598-018-24027-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/14/2018] [Indexed: 01/02/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects the motor system leading to generalized paralysis and death of patients. The understanding of early pathogenic mechanisms will help to define early diagnostics criteria that will eventually provide basis for efficient therapeutics. Early symptoms of ALS usually include muscle weakness or stiffness. Therefore, mechanical response of differentiated myotubes from primary cultures of mice, expressing the ALS-causing SOD1G93A mutation, was examined by atomic force microscopy. Simultaneous acquisition of topography and cell elasticity of ALS myotubes was performed by force mapping method, compared with healthy myotubes and supplemented with immunofluorescence and qRT-PCR studies. Wild type myotubes reveal a significant difference in elasticity between a narrow and a wide population, consistent with maturation occurring with higher actin expression relative to myosin together with larger myotube width. However, this is not true for SOD1G93A expressing myotubes, where a significant shift of thin population towards higher elastic modulus values was observed. We provide evidence that SOD1 mutant induces structural changes that occurs very early in muscle development and well before symptomatic stage of the disease. These findings could significantly contribute to the understanding of the role of skeletal muscle in ALS pathogenesis.
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13
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Kneppers A, Verdijk L, de Theije C, Corten M, Gielen E, van Loon L, Schols A, Langen R. A novel in vitro model for the assessment of postnatal myonuclear accretion. Skelet Muscle 2018; 8:4. [PMID: 29444710 PMCID: PMC5813369 DOI: 10.1186/s13395-018-0151-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Accepted: 01/26/2018] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Due to the post-mitotic nature of myonuclei, postnatal myogenesis is essential for skeletal muscle growth, repair, and regeneration. This process is facilitated by satellite cells through proliferation, differentiation, and subsequent fusion with a pre-existing muscle fiber (i.e., myonuclear accretion). Current knowledge of myogenesis is primarily based on the in vitro formation of syncytia from myoblasts, which represents aspects of developmental myogenesis, but may incompletely portray postnatal myogenesis. Therefore, we aimed to develop an in vitro model that better reflects postnatal myogenesis, to study the cell intrinsic and extrinsic processes and signaling involved in the regulation of postnatal myogenesis. METHODS Proliferating C2C12 myoblasts were trypsinized and co-cultured for 3 days with 5 days differentiated C2C12 myotubes. Postnatal myonuclear accretion was visually assessed by live cell time-lapse imaging and cell tracing by cell labeling with Vybrant® DiD and DiO. Furthermore, a Cre/LoxP-based cell system was developed to semi-quantitatively assess in vitro postnatal myonuclear accretion by the conditional expression of luciferase upon myoblast-myotube fusion. Luciferase activity was assessed luminometrically and corrected for total protein content. RESULTS Live cell time-lapse imaging, staining-based cell tracing, and recombination-dependent luciferase activity, showed the occurrence of postnatal myonuclear accretion in vitro. Treatment of co-cultures with the myogenic factor IGF-I (p < 0.001) and the cytokines IL-13 (p < 0.05) and IL-4 (p < 0.001) increased postnatal myonuclear accretion, while the myogenic inhibitors cytochalasin D (p < 0.001), myostatin (p < 0.05), and TNFα (p < 0.001) decreased postnatal myonuclear accretion. Furthermore, postnatal myonuclear accretion was increased upon recovery from electrical pulse stimulation-induced fiber damage (p < 0.001) and LY29004-induced atrophy (p < 0.001). Moreover, cell type-specific siRNA-mediated knockdown of myomaker in myoblasts (p < 0.001), but not in myotubes, decreased postnatal myonuclear accretion. CONCLUSIONS We developed a physiologically relevant, sensitive, high-throughput cell system for semi-quantitative assessment of in vitro postnatal myonuclear accretion, which can be used to mimic physiological myogenesis triggers, and can distinguish the cell type-specific roles of signals and responses in the regulation of postnatal myogenesis. As such, this method is suitable for both basal and translational research on the regulation of postnatal myogenesis, and will improve our understanding of muscle pathologies that result from impaired satellite cell number or function.
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Affiliation(s)
- Anita Kneppers
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands.
| | - Lex Verdijk
- Department of Human Biology and Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Chiel de Theije
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Mark Corten
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Ellis Gielen
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Luc van Loon
- Department of Human Biology and Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Annemie Schols
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Ramon Langen
- Department of Respiratory Medicine, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands
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14
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O'Rourke AR, Lindsay A, Tarpey MD, Yuen S, McCourt P, Nelson DM, Perrin BJ, Thomas DD, Spangenburg EE, Lowe DA, Ervasti JM. Impaired muscle relaxation and mitochondrial fission associated with genetic ablation of cytoplasmic actin isoforms. FEBS J 2018; 285:481-500. [PMID: 29265728 DOI: 10.1111/febs.14367] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 11/06/2017] [Accepted: 12/13/2017] [Indexed: 12/28/2022]
Abstract
While α-actin isoforms predominate in adult striated muscle, skeletal muscle-specific knockouts (KOs) of nonmuscle cytoplasmic βcyto - or γcyto -actin each cause a mild, but progressive myopathy effected by an unknown mechanism. Using transmission electron microscopy, we identified morphological abnormalities in both the mitochondria and the sarcoplasmic reticulum (SR) in aged muscle-specific βcyto - and γcyto -actin KO mice. We found βcyto - and γcyto -actin proteins to be enriched in isolated mitochondrial-associated membrane preparations, which represent the interface between mitochondria and sarco-endoplasmic reticulum important in signaling and mitochondrial dynamics. We also measured significantly elongated and interconnected mitochondrial morphologies associated with a significant decrease in mitochondrial fission events in primary mouse embryonic fibroblasts lacking βcyto - and/or γcyto -actin. Interestingly, mitochondrial respiration in muscle was not measurably affected as oxygen consumption was similar in skeletal muscle fibers from 12 month-old muscle-specific βcyto - and γcyto -actin KO mice. Instead, we found that the maximal rate of relaxation after isometric contraction was significantly slowed in muscles of 12-month-old βcyto - and γcyto -actin muscle-specific KO mice. Our data suggest that impaired Ca2+ re-uptake may presage development of the observed SR morphological changes in aged mice while providing a potential pathological mechanism for the observed myopathy.
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Affiliation(s)
- Allison R O'Rourke
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN, USA
| | - Angus Lindsay
- Department of Rehabilitation Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Michael D Tarpey
- Department of Physiology, East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA
| | - Samantha Yuen
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Preston McCourt
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - D'anna M Nelson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Benjamin J Perrin
- Department of Biology, Indiana University-Purdue University Indianapolis, IN, USA
| | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Espen E Spangenburg
- Department of Physiology, East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC, USA
| | - Dawn A Lowe
- Department of Rehabilitation Medicine, University of Minnesota, Minneapolis, MN, USA
| | - James M Ervasti
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN, USA
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15
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Liu X, Liu Y, Zhao F, Hun T, Li S, Wang Y, Sun W, Wang W, Sun Y, Fan Y. Regulation of cell arrangement using a novel composite micropattern. J Biomed Mater Res A 2017; 105:3093-3101. [DOI: 10.1002/jbm.a.36157] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 06/16/2017] [Accepted: 07/07/2017] [Indexed: 12/12/2022]
Affiliation(s)
- Xiaoyi Liu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering; Beihang University; Beijing 100191 People's Republic of China
- State Key Laboratory of Transducer Technology; Chinese Academy of Sciences; Shanghai 200050 People's Republic of China
| | - Yaoping Liu
- Institute of Microelectronics, Peking University; Beijing 100871 People's Republic of China
| | - Feng Zhao
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering; Beihang University; Beijing 100191 People's Republic of China
- State Key Laboratory of Transducer Technology; Chinese Academy of Sciences; Shanghai 200050 People's Republic of China
| | - Tingting Hun
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering; Beihang University; Beijing 100191 People's Republic of China
- State Key Laboratory of Transducer Technology; Chinese Academy of Sciences; Shanghai 200050 People's Republic of China
| | - Shan Li
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering; Beihang University; Beijing 100191 People's Republic of China
- State Key Laboratory of Transducer Technology; Chinese Academy of Sciences; Shanghai 200050 People's Republic of China
| | - Yuguang Wang
- Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences; 100083 People's Republic of China
| | - Weijie Sun
- Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences; 100083 People's Republic of China
| | - Wei Wang
- Institute of Microelectronics, Peking University; Beijing 100871 People's Republic of China
- National Key Laboratory of Science and Technology on Micro/Nano Fabrication; Beijing 100871 China
- Innovation Center for Micro-Nano-electronics and Integrated System; Beijing 100871 China
| | - Yan Sun
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering; Beihang University; Beijing 100191 People's Republic of China
- State Key Laboratory of Transducer Technology; Chinese Academy of Sciences; Shanghai 200050 People's Republic of China
| | - Yubo Fan
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering; Beihang University; Beijing 100191 People's Republic of China
- National Research Center for Rehabilitation Technical Aids; Beijing 100176 People's Republic of China
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16
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Sasi Kumar K, Ramadhas A, Nayak S, Kaniyappan S, Dayma K, Radha V. C3G (RapGEF1), a regulator of actin dynamics promotes survival and myogenic differentiation of mouse mesenchymal cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2629-39. [DOI: 10.1016/j.bbamcr.2015.06.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 06/17/2015] [Accepted: 06/27/2015] [Indexed: 12/11/2022]
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17
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Grefte S, Wagenaars JAL, Jansen R, Willems PHGM, Koopman WJH. Rotenone inhibits primary murine myotube formation via Raf-1 and ROCK2. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1606-14. [PMID: 25827955 DOI: 10.1016/j.bbamcr.2015.03.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 03/04/2015] [Accepted: 03/19/2015] [Indexed: 11/30/2022]
Abstract
Rotenone (ROT) is a widely used inhibitor of complex I (CI), the first complex of the mitochondrial oxidative phosphorylation (OXPHOS) system. However, particularly at high concentrations ROT was also described to display off-target effects. Here we studied how ROT affected in vitro primary murine myotube formation. We demonstrate that myotube formation is specifically inhibited by ROT (10-100nM), but not by piericidin A (PA; 100nM), another CI inhibitor. At 100nM, both ROT and PA fully blocked myoblast oxygen consumption. Knock-down of Rho-associated, coiled-coil containing protein kinase 2 (ROCK2) and, to a lesser extent ROCK1, prevented the ROT-induced inhibition of myotube formation. Moreover, the latter was reversed by inhibiting Raf-1 activity. In contrast, ROT-induced inhibition of myotube formation was not prevented by knock-down of RhoA. Taken together, our results support a model in which ROT reduces primary myotube formation independent of its inhibitory effect on CI-driven mitochondrial ATP production, but via a mechanism primarily involving the Raf-1/ROCK2 pathway.
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Affiliation(s)
- Sander Grefte
- Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Jori A L Wagenaars
- Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Renate Jansen
- Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Peter H G M Willems
- Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Werner J H Koopman
- Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.
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18
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Simionescu-Bankston A, Pichavant C, Canner JP, Apponi LH, Wang Y, Steeds C, Olthoff JT, Belanto JJ, Ervasti JM, Pavlath GK. Creatine kinase B is necessary to limit myoblast fusion during myogenesis. Am J Physiol Cell Physiol 2015; 308:C919-31. [PMID: 25810257 DOI: 10.1152/ajpcell.00029.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 03/19/2015] [Indexed: 11/22/2022]
Abstract
Myoblast fusion is critical for proper muscle growth and regeneration. During myoblast fusion, the localization of some molecules is spatially restricted; however, the exact reason for such localization is unknown. Creatine kinase B (CKB), which replenishes local ATP pools, localizes near the ends of cultured primary mouse myotubes. To gain insights into the function of CKB, we performed a yeast two-hybrid screen to identify CKB-interacting proteins. We identified molecules with a broad diversity of roles, including actin polymerization, intracellular protein trafficking, and alternative splicing, as well as sarcomeric components. In-depth studies of α-skeletal actin and α-cardiac actin, two predominant muscle actin isoforms, demonstrated their biochemical interaction and partial colocalization with CKB near the ends of myotubes in vitro. In contrast to other cell types, specific knockdown of CKB did not grossly affect actin polymerization in myotubes, suggesting other muscle-specific roles for CKB. Interestingly, knockdown of CKB resulted in significantly increased myoblast fusion and myotube size in vitro, whereas knockdown of creatine kinase M had no effect on these myogenic parameters. Our results suggest that localized CKB plays a key role in myotube formation by limiting myoblast fusion during myogenesis.
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Affiliation(s)
- Adriana Simionescu-Bankston
- Graduate Program in Biochemistry, Cell and Developmental Biology, Emory University School of Medicine, Atlanta, Georgia; Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - Christophe Pichavant
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - James P Canner
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - Luciano H Apponi
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - Yanru Wang
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - Craig Steeds
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
| | - John T Olthoff
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Joseph J Belanto
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - James M Ervasti
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Grace K Pavlath
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia; and
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19
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Lenhart KC, Becherer AL, Li J, Xiao X, McNally EM, Mack CP, Taylor JM. GRAF1 promotes ferlin-dependent myoblast fusion. Dev Biol 2014; 393:298-311. [PMID: 25019370 DOI: 10.1016/j.ydbio.2014.06.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 06/17/2014] [Accepted: 06/26/2014] [Indexed: 01/08/2023]
Abstract
Myoblast fusion (a critical process by which muscles grow) occurs in a multi-step fashion that requires actin and membrane remodeling; but important questions remain regarding the spatial/temporal regulation of and interrelationship between these processes. We recently reported that the Rho-GAP, GRAF1, was particularly abundant in muscles undergoing fusion to form multinucleated fibers and that enforced expression of GRAF1 in cultured myoblasts induced robust fusion by a process that required GAP-dependent actin remodeling and BAR domain-dependent membrane sculpting. Herein we developed a novel line of GRAF1-deficient mice to explore a role for this protein in the formation/maturation of myotubes in vivo. Post-natal muscles from GRAF1-depleted mice exhibited a significant and persistent reduction in cross-sectional area, impaired regenerative capacity and a significant decrease in force production indicative of lack of efficient myoblast fusion. A significant fusion defect was recapitulated in isolated myoblasts depleted of GRAF1 or its closely related family member GRAF2. Mechanistically, we show that GRAF1 and 2 facilitate myoblast fusion, at least in part, by promoting vesicle-mediated translocation of fusogenic ferlin proteins to the plasma membrane.
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Affiliation(s)
- Kaitlin C Lenhart
- Department of Pathology and Laboratory, Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Abby L Becherer
- Department of Pathology and Laboratory, Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Jianbin Li
- Department of Gene Therapy Molecular Pharmaceutics, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Xiao Xiao
- Department of Gene Therapy Molecular Pharmaceutics, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | | | - Christopher P Mack
- Department of Pathology and Laboratory, Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA; McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Joan M Taylor
- Department of Pathology and Laboratory, Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA; McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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20
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Myogenesis defect due to Toca-1 knockdown can be suppressed by expression of N-WASP. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1930-41. [PMID: 24861867 DOI: 10.1016/j.bbamcr.2014.05.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 05/15/2014] [Accepted: 05/16/2014] [Indexed: 01/09/2023]
Abstract
Skeletal muscle formation is a multistep process involving proliferation, differentiation, alignment and fusion of myoblasts to form myotubes which fuse with additional myoblast to form myofibers. Toca-1 (Transducer of Cdc42-dependent actin assembly), is an adaptor protein which activates N-WASP in conjunction with Cdc42 to facilitate membrane invagination, endocytosis and actin cytoskeleton remodeling. Expression of Toca-1 in mouse primary myoblasts and C2C12 myoblasts was up-regulated on day 1 of differentiation and subsequently down-regulated during differentiation. Knocking down Toca-1 expression in C2C12 cells (Toca-1(KD) cells) resulted in a significant decrease in myotube formation and expression of shRNA-resistant Toca-1 in Toca-1(KD) cells rescued the myogenic defect, suggesting that the knockdown was specific and Toca-1 is essential for myotube formation. Toca-1(KD) cells exhibited elongated spindle-like morphology, expressed myogenic markers (MyoD and MyHC) and localized N-Cadherin at cell periphery similar to control cells suggesting that Toca-1 is not essential for morphological changes or expression of proteins critical for differentiation. Toca-1(KD) cells displayed prominent actin fibers suggesting a defect in actin cytoskeleton turnover necessary for cell-cell fusion. Toca-1(KD) cells migrated faster than control cells and had a reduced number of vinculin patches similar to N-WASP(KO) MEF cells. Transfection of N-WASP-expressing plasmid into Toca-1(KD) cells restored myotube formation of Toca-1(KD) cells. Thus, our results suggest that Toca-1(KD) cells have defects in formation of myotubes probably due to reduced activity of actin cytoskeleton regulators such as N-WASP. This is the first study to identify and characterize the role of Toca-1 in myogenesis.
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21
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Cartwright S, Karakesisoglou I. Nesprins in health and disease. Semin Cell Dev Biol 2013; 29:169-79. [PMID: 24374011 DOI: 10.1016/j.semcdb.2013.12.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 11/29/2013] [Accepted: 12/15/2013] [Indexed: 01/20/2023]
Abstract
LINC (Linker of Nucleoskeleton and Cytoskeleton) complex is an evolutionary conserved structure that spans the entire nuclear envelope (NE), and integrates the nuclear interior with the cytoskeleton, in order to support a diverse array of fundamental biological processes. Key components of the LINC complex are the nesprins (Nuclear Envelope SPectrin Repeat proteINS) that were initially described as large integral NE proteins. However, nesprin genes are complex and generate many variants, which occupy various sub-cellular compartments suggesting additional functions. Hence, the potential involvement of nesprins in disease has expanded immensely on what we already know. That is, nesprins are implicated in diseases such as cancer, myopathies, arthrogryposis, neurological disorders and hearing loss. Here we review nesprins by providing an in depth account of their structure, molecular interactions and cellular functions with relevance to their potential roles in disease. Specifically, we speculate about possible pathomechanisms underlying nesprin-associated diseases.
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Affiliation(s)
- Sarah Cartwright
- School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, UK
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22
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Durcan PJ, Al-Shanti N, Stewart CE. Identification and characterization of novel Kirrel isoform during myogenesis. Physiol Rep 2013; 1:e00044. [PMID: 24303129 PMCID: PMC3835000 DOI: 10.1002/phy2.44] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 07/03/2013] [Indexed: 12/31/2022] Open
Abstract
Somatic cell fusion is an essential component of skeletal muscle development and growth and repair from injury. Additional cell types such as trophoblasts and osteoclasts also require somatic cell fusion events to perform their physiological functions. Currently we have rudimentary knowledge on molecular mechanisms regulating somatic cell fusion events in mammals. We therefore investigated during in vitro murine myogenesis a mammalian homolog, Kirrel, of the Drosophila Melanogaster genes Roughest (Rst) and Kin of Irre (Kirre) which regulate somatic muscle cell fusion during embryonic development. Our results demonstrate the presence of a novel murine Kirrel isoform containing a truncated cytoplasmic domain which we term Kirrel B. Protein expression levels of Kirrel B are inverse to the occurrence of cell fusion events during in vitro myogenesis which is in stark contrast to the expression profile of Rst and Kirre during myogenesis in Drosophila. Furthermore, chemical inhibition of cell fusion confirmed the inverse expression pattern of Kirrel B protein levels in relation to cell fusion events. The discovery of a novel Kirrel B protein isoform during myogenesis highlights the need for more thorough investigation of the similarities and potential differences between fly and mammals with regards to the muscle cell fusion process.
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Affiliation(s)
- Peter J Durcan
- Department of Physiological Sciences, Stellenbosch University Merriman avenue, Stellenbosch, 7600, Western Cape, South Africa ; Institute for Biomedical Research into Human movement, School of Healthcare Science, Manchester Metropolitan University Oxford road, M1 5GD, Manchester, U.K
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23
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Monge C, Saha N, Boudou T, Pózos-Vásquez C, Dulong V, Glinel K, Picart C. Rigidity-patterned polyelectrolyte films to control myoblast cell adhesion and spatial organization. ADVANCED FUNCTIONAL MATERIALS 2013; 23:3432-3442. [PMID: 25100929 PMCID: PMC4119880 DOI: 10.1002/adfm.201203580] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In vivo, cells are sensitive to the stiffness of their micro-environment and especially to the spatial organization of the stiffness. In vitro studies of this phenomenon can help to better understand the mechanisms of the cell response to spatial variations of the matrix stiffness. In this work, we design polelyelectrolyte multilayer films made of poly(L-lysine) and a photo-reactive hyaluronan derivative. These films can be photo-crosslinked through a photomask to create spatial patterns of rigidity. Quartz substrates incorporating a chromium mask are prepared to expose selectively the film to UV light (in a physiological buffer), without any direct contact between the photomask and the soft film. We show that these micropatterns are chemically homogeneous and flat, without any preferential adsorption of adhesive proteins. Three groups of pattern geometries differing by their shape (circles or lines), size (form 2 to 100 μm) or interspacing distance between the motifs are used to study the adhesion and spatial organization of myoblast cells. On large circular micropatterns, the cells form large assemblies that are confined to the stiffest parts. Conversely, when the size of the rigidity patterns is subcellular, the cells respond by forming protrusions. Finally, on linear micropatterns of rigidity, myoblasts align and their nuclei drastically elongate in specific conditions. These results pave the way for the study of the different steps of myoblast fusion in response to matrix rigidity in well-defined geometrical conditions.
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Affiliation(s)
- Claire Monge
- CNRS-UMR 5628, Laboratoire des Matériaux et du Génie Physique, CNRS et Institut Polytechnique de Grenoble, Université de Grenoble, 3 parvis L. Néel F-38016 Grenoble, France
| | - Naresh Saha
- CNRS-UMR 5628, Laboratoire des Matériaux et du Génie Physique, CNRS et Institut Polytechnique de Grenoble, Université de Grenoble, 3 parvis L. Néel F-38016 Grenoble, France; Institute of Condensed Matter & Nanosciences, Bio & Soft Matter division Croix du Sud 1, box L7.04.02 B-1348 Louvain-la-Neuve, Belgium
| | - Thomas Boudou
- CNRS-UMR 5628, Laboratoire des Matériaux et du Génie Physique, CNRS et Institut Polytechnique de Grenoble, Université de Grenoble, 3 parvis L. Néel F-38016 Grenoble, France
| | - Cuauhtemoc Pózos-Vásquez
- Institute of Condensed Matter & Nanosciences, Bio & Soft Matter division Croix du Sud 1, box L7.04.02 B-1348 Louvain-la-Neuve, Belgium
| | - Virginie Dulong
- Laboratoire Polymères, Biopolymères, Surfaces, CNRS-UMR 6270 Université de Rouen Bd Maurice de Broglie F-76821 Mont Saint Aignan, France
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24
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Ballester-Beltrán J, Lebourg M, Salmerón-Sánchez M. Dorsal and ventral stimuli in sandwich-like microenvironments. Effect on cell differentiation. Biotechnol Bioeng 2013; 110:3048-58. [DOI: 10.1002/bit.24972] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 05/29/2013] [Accepted: 05/31/2013] [Indexed: 12/16/2022]
Affiliation(s)
- José Ballester-Beltrán
- Center for Biomaterials and Tissue Engineering; Universitat Politècnica de València; Valencia 46022 Spain
| | - Myriam Lebourg
- Center for Biomaterials and Tissue Engineering; Universitat Politècnica de València; Valencia 46022 Spain
- CIBER de Bioingeniería; Biomateriales y Nanomedicina; Valencia 46022 Spain
| | - Manuel Salmerón-Sánchez
- Division of Biomedical Engineering, School of Engineering; University of Glasgow; Rankine Building, Oakfield Avenue Glasgow G12 8LT UK
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25
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Monge C, Ren K, Berton K, Guillot R, Peyrade D, Picart C. Engineering muscle tissues on microstructured polyelectrolyte multilayer films. Tissue Eng Part A 2012; 18:1664-76. [PMID: 22607460 DOI: 10.1089/ten.tea.2012.0079] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The use of surface coating on biomaterials can render the original substratum with new functionalities that can improve the chemical, physical, and mechanical properties as well as enhance cellular cues such as attachment, proliferation, and differentiation. In this work, we combined biocompatible polydimethylsiloxane (PDMS) with a biomimetic polyelectrolyte multilayer (PEM) film made of poly(L-lysine) and hyaluronic acid (PLL/HA) for skeletal muscle tissue engineering. By microstructuring PDMS in grooves of a different width (5, 10, 30, and 100 μm) and by modulating the stiffness of the (PLL/HA) films, we guided skeletal muscle cell differentiation into myotubes. We found optimal conditions for both the formation of parallel-oriented myotubes and their maturation. Significantly, the myoblasts were collectively prealigned to the grooves before their differentiation. Before fusion, the highest aspect ratio and orientation of nuclei were observed for the 5 and 10 μm wide micropatterns. The formation of myotubes was observed regardless of the size of the micropatterns, and we found that their typical width was 10-12 μm. Their maturation was characterized by the immunolabeling of type II isomyosin. The amount of myosin striation was not affected by the topography, except for the 5 μm wide micropatterns. We highlighted the spatial constraints that led to an important nuclei deformation and further impairment of maturation within the 5 μm grooves. Altogether, our results show that the PEM film combined with PDMS is a powerful tool that is used for skeletal muscle engineering. This work opens perspectives for the development of skeletal muscle tissue in contact with films containing bioactive peptides or growth factors as well as for the study of pathogenic myotubes.
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Affiliation(s)
- Claire Monge
- LMGP, CNRS UMR 5628 (LMGP), Grenoble Institute of Technology and CNRS, Grenoble Cedex, France
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26
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Doherty JT, Lenhart KC, Cameron MV, Mack CP, Conlon FL, Taylor JM. Skeletal muscle differentiation and fusion are regulated by the BAR-containing Rho-GTPase-activating protein (Rho-GAP), GRAF1. J Biol Chem 2011; 286:25903-21. [PMID: 21622574 DOI: 10.1074/jbc.m111.243030] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although RhoA activity is necessary for promoting myogenic mesenchymal stem cell fates, recent studies in cultured cells suggest that down-regulation of RhoA activity in specified myoblasts is required for subsequent differentiation and myotube formation. However, whether this phenomenon occurs in vivo and which Rho modifiers control these later events remain unclear. We found that expression of the Rho-GTPase-activating protein, GRAF1, was transiently up-regulated during myogenesis, and studies in C2C12 cells revealed that GRAF1 is necessary and sufficient for mediating RhoA down-regulation and inducing muscle differentiation. Moreover, forced expression of GRAF1 in pre-differentiated myoblasts drives robust muscle fusion by a process that requires GTPase-activating protein-dependent actin remodeling and BAR-dependent membrane binding or sculpting. Moreover, morpholino-based knockdown studies in Xenopus laevis determined that GRAF1 expression is critical for muscle development. GRAF1-depleted embryos exhibited elevated RhoA activity and defective myofibrillogenesis that resulted in progressive muscle degeneration, defective motility, and embryonic lethality. Our results are the first to identify a GTPase-activating protein that regulates muscle maturation and to highlight the functional importance of BAR domains in myotube formation.
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Hes6 is required for actin cytoskeletal organization in differentiating C2C12 myoblasts. Exp Cell Res 2011; 317:1590-602. [PMID: 21501606 DOI: 10.1016/j.yexcr.2011.03.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 03/29/2011] [Accepted: 03/31/2011] [Indexed: 11/23/2022]
Abstract
Hes6 is a member of the hairy-enhancer-of-split family of transcription factors that regulate proliferating cell fate in development and is known to be expressed in developing muscle. Here we investigate its function in myogenesis in vitro. We show that Hes6 is a direct transcriptional target of the myogenic transcription factors MyoD and Myf5, indicating that it is integral to the myogenic transcriptional program. The localization of Hes6 protein changes during differentiation, becoming predominantly nuclear. Knockdown of Hes6 mRNA levels by siRNA has no effect on cell cycle exit or induction of myosin heavy chain expression in differentiating C2C12 myoblasts, but F-actin filament formation is disrupted and both cell motility and myoblast fusion are reduced. The knockdown phenotype is rescued by expression of Hes6 cDNA resistant to siRNA. These results define a novel role for Hes6 in actin cytoskeletal dynamics in post mitotic myoblasts.
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28
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Postel R, Ketema M, Kuikman I, de Pereda JM, Sonnenberg A. Nesprin-3 augments peripheral nuclear localization of intermediate filaments in zebrafish. J Cell Sci 2011; 124:755-64. [PMID: 21303928 DOI: 10.1242/jcs.081174] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The outer nuclear membrane protein nesprin-3 binds the cytoskeletal linker protein plectin, which are proposed to anchor the intermediate filaments to the nuclear envelope. To investigate the function of nesprin-3 in vivo, we used the zebrafish as a vertebrate model system. Zebrafish nesprin-3 is expressed at the nuclear envelope of epidermal and skeletal muscle cells during development. Unexpectedly, loss of nesprin-3 did not affect embryonic development, viability or fertility. However, nesprin-3-deficient zebrafish embryos showed a reduced concentration of intermediate filaments around the nucleus. Additional analysis revealed the presence of two nesprin-3 isoforms in zebrafish, nesprin-3α and nesprin-3β. Nesprin-3β is only expressed during early development and lacks seven amino acids in its first spectrin repeat that are crucial for plectin binding and recruitment to the nuclear envelope. These seven amino acids are highly conserved and we showed that residues R43 and L44 within this motif are required for plectin binding. Furthermore, several residues in the actin-binding domain of plectin that are crucial for binding to the integrin β4 subunit are also important for the binding to nesprin-3α, indicating partial overlapping binding sequences for nesprin-3α and integrin β4. All this shows that nesprin-3 is dispensable for normal development in zebrafish, but important for mediating the association of the intermediate filament system with the nucleus in vivo.
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Affiliation(s)
- Ruben Postel
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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29
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Abnormal actomyosin assembly in proliferating and differentiating myoblasts upon expression of a cytosolic DMPK isoform. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:867-77. [PMID: 21295081 DOI: 10.1016/j.bbamcr.2011.01.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Revised: 01/05/2011] [Accepted: 01/24/2011] [Indexed: 01/17/2023]
Abstract
DMPK, the product of the mutated gene in myotonic dystrophy type 1, belongs to the subfamily of Rho-associated serine-threonine protein kinases, whose members play a role in actin-based cell morphodynamics. Not much is known about the physiological role of differentially localized individual DMPK splice isoforms. We report here that prominent stellar-shaped stress fibers are formed during early and late steps of differentiation in DMPK-deficient myoblast-myotubes upon complementation with the short cytosolic DMPK E isoform. Expression of DMPK E led to an increased phosphorylation status of MLC2. We found no such effects with vectors that encode a mutant DMPK E which was rendered enzymatically inactive or any of the long C-terminally anchored DMPK isoforms. Presence of stellar structures appears associated with changes in cell shape and motility and a delay in myogenesis. Our data strongly suggest that cytosolic DMPK participates in remodeling of the actomyosin cytoskeleton in developing skeletal muscle cells. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.
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30
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Langhammer CG, Zahn JD, Firestein BL. Identification and quantification of skeletal myotube contraction and association in vitro by video microscopy. Cytoskeleton (Hoboken) 2010; 67:413-24. [PMID: 20506519 DOI: 10.1002/cm.20457] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Skeletal muscle is the largest tissue in the body by weight and plays many roles in maintaining homeostasis and health. Ex vivo cell-based experimental systems used to study muscle cell contraction, and others based on incorporation of cells into sensitive force transducers or electrophysiology equipment, are time-consuming, invasive, and not universally available, slowing the pace of research. Video microscopy provides a noninvasive way to record the contractile behavior of skeletal muscle cells in vitro. We have developed a numerical procedure using image processing and pattern recognition algorithms, that makes it possible to quantify contractile behavior of multiple myotubes simultaneously, based on video data. We examined the ability of the program to identify movement using a simplified graphical model of myotube contraction and found that the program's success is dependent on the morphology and movement characteristics of the objects. However, the program performs optimally over the types of motions approximating those observed in culture and identifies contracting myotubes in sample videomicrographs of muscle cells in vitro. This program quantifies contractility on a population level, can be adapted for use in laboratories capable of digital video capture from a microscope, and may be coupled with other experimental techniques to supplement existing research tools.
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Affiliation(s)
- Christopher G Langhammer
- Department of Biomedical Engineering, Rutgers University, Busch Campus, Piscataway, New Jersey 08854, USA
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31
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Pavlath GK. Spatial and functional restriction of regulatory molecules during mammalian myoblast fusion. Exp Cell Res 2010; 316:3067-72. [PMID: 20553712 DOI: 10.1016/j.yexcr.2010.05.025] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 05/21/2010] [Accepted: 05/21/2010] [Indexed: 10/19/2022]
Abstract
Myoblast fusion is a highly regulated process that is key for forming skeletal muscle during development and regeneration in mammals. Much remains to be understood about the molecular regulation of myoblast fusion. Some molecules that influence mammalian muscle fusion display specific cellular localization during myogenesis. Such molecules can be localized to the contact region between two fusing cells either in both cells or only in one of the cells. How distinct localization of molecules contributes to fusion is not clear. Further complexity exists as other molecules are functionally restricted to myoblasts at later stages of myogenesis to regulate their fusion with multinucleated myotubes. This review examines these three categories of molecules and discusses how spatial and functional restriction may contribute to the formation of a multinucleated cell. Understanding how and why molecules become restricted in location or function is likely to provide further insights into the mechanisms regulating mammalian muscle fusion.
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Affiliation(s)
- Grace K Pavlath
- Department of Pharmacology, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA.
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32
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Bach AS, Enjalbert S, Comunale F, Bodin S, Vitale N, Charrasse S, Gauthier-Rouvière C. ADP-ribosylation factor 6 regulates mammalian myoblast fusion through phospholipase D1 and phosphatidylinositol 4,5-bisphosphate signaling pathways. Mol Biol Cell 2010; 21:2412-24. [PMID: 20505075 PMCID: PMC2903670 DOI: 10.1091/mbc.e09-12-1063] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Here we show that ARF6 is associated with the multiproteic complex that contains M-cadherin, Trio, and Rac1 and accumulates at sites of myoblast fusion. ARF6 silencing inhibits the association of Trio and Rac1 with M-cadherin. Moreover, we demonstrate that ARF6 regulates myoblast fusion through Phospholipase D activation and PI(4,5)P2 production. Myoblast fusion is an essential step during myoblast differentiation that remains poorly understood. M-cadherin–dependent pathways that signal through Rac1 GTPase activation via the Rho-guanine nucleotide exchange factor (GEF) Trio are important for myoblast fusion. The ADP-ribosylation factor (ARF)6 GTPase has been shown to bind to Trio and to regulate Rac1 activity. Moreover, Loner/GEP100/BRAG2, a GEF of ARF6, has been involved in mammalian and Drosophila myoblast fusion, but the specific role of ARF6 has been not fully analyzed. Here, we show that ARF6 activity is increased at the time of myoblast fusion and is required for its implementation in mouse C2C12 myoblasts. Specifically, at the onset of myoblast fusion, ARF6 is associated with the multiproteic complex that contains M-cadherin, Trio, and Rac1 and accumulates at sites of myoblast fusion. ARF6 silencing inhibits the association of Trio and Rac1 with M-cadherin. Moreover, we demonstrate that ARF6 regulates myoblast fusion through phospholipase D (PLD) activation and phosphatidylinositol 4,5-bis-phosphate production. Together, these data indicate that ARF6 is a critical regulator of C2C12 myoblast fusion and participates in the regulation of PLD activities that trigger both phospholipids production and actin cytoskeleton reorganization at fusion sites.
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Affiliation(s)
- Anne-Sophie Bach
- Universités Montpellier 2 et 1, Centre de Recherche en Biochimie Macromoléculaire, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5237, Institut Fédératif de Recherche 122 1919 Route de Mende, 34293 Montpellier, France
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Guerin CM, Kramer SG. Cytoskeletal remodeling during myotube assembly and guidance: coordinating the actin and microtubule networks. Commun Integr Biol 2010; 2:452-7. [PMID: 19907716 DOI: 10.4161/cib.2.5.9158] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Accepted: 06/02/2009] [Indexed: 11/19/2022] Open
Abstract
The formation of a multinucleated muscle fiber from individual myoblasts is a complex morphological event that requires dramatic cytoskeletal rearrangements. This multistep process includes myoblast fusion, myotube migration and elongation, myotube target recognition, and finally attachment to form a stable adhesion complex. Many of the studies directed towards understanding the developmental process of muscle morphogenesis at the cellular level have relied on forward genetic screens in model systems such as Drosophila melanogaster for mutations affecting individual stages in myogenesis. Through the analyses of these gene products, proteins that regulate the actin or microtubule cytoskeleton have emerged as important players in each of these steps. We recently demonstrated that RacGAP50C, an essential protein that functions as a cytoskeletal regulator during cell division, also plays an important role in organizing the polarized microtubule network in the elongating myotube. Here we review the current literature regarding Drosophila myogenesis and illustrate several steps of muscle development with respect to the diverse roles that the cytoskeleton plays during this process. Furthermore, we discuss the significance of cytoskeletal coordination during these multiple steps.
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Affiliation(s)
- Colleen M Guerin
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USA
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34
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Ahmed WW, Wolfram T, Goldyn AM, Bruellhoff K, Rioja BA, Möller M, Spatz JP, Saif TA, Groll J, Kemkemer R. Myoblast morphology and organization on biochemically micro-patterned hydrogel coatings under cyclic mechanical strain. Biomaterials 2010; 31:250-8. [DOI: 10.1016/j.biomaterials.2009.09.047] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 09/11/2009] [Indexed: 10/20/2022]
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35
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Rochlin K, Yu S, Roy S, Baylies MK. Myoblast fusion: when it takes more to make one. Dev Biol 2009; 341:66-83. [PMID: 19932206 DOI: 10.1016/j.ydbio.2009.10.024] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Revised: 10/14/2009] [Accepted: 10/14/2009] [Indexed: 01/09/2023]
Abstract
Cell-cell fusion is a crucial and highly regulated event in the genesis of both form and function of many tissues. One particular type of cell fusion, myoblast fusion, is a key cellular process that shapes the formation and repair of muscle. Despite its importance for human health, the mechanisms underlying this process are still not well understood. The purpose of this review is to highlight the recent literature pertaining to myoblast fusion and to focus on a comparison of these studies across several model systems, particularly the fly, zebrafish and mouse. Advances in technical analysis and imaging have allowed identification of new fusion genes and propelled further characterization of previously identified genes in each of these systems. Among the cellular steps identified as critical for myoblast fusion are migration, recognition, adhesion, membrane alignment and membrane pore formation and resolution. Importantly, striking new evidence indicates that orthologous genes govern several of these steps across these species. Taken together, comparisons across three model systems are illuminating a once elusive process, providing exciting new insights and a useful framework of genes and mechanisms.
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Affiliation(s)
- Kate Rochlin
- Program in Developmental Biology, Sloan-Kettering Institute, New York, NY 10065, USA
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36
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Nowak SJ, Nahirney PC, Hadjantonakis AK, Baylies MK. Nap1-mediated actin remodeling is essential for mammalian myoblast fusion. J Cell Sci 2009; 122:3282-93. [PMID: 19706686 DOI: 10.1242/jcs.047597] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Myoblast fusion is crucial for the formation, growth, maintenance and regeneration of healthy skeletal muscle. Unfortunately, the molecular machinery, cell behaviors, and membrane and cytoskeletal remodeling events that govern fusion and myofiber formation remain poorly understood. Using time-lapse imaging approaches on mouse C2C12 myoblasts, we identify discrete and specific molecular events at myoblast membranes during fusion and myotube formation. These events include rearrangement of cell shape from fibroblast to spindle-like morphologies, changes in lamellipodial and filopodial extensions during different periods of differentiation, and changes in membrane alignment and organization during fusion. We find that actin-cytoskeleton remodeling is crucial for these events: pharmacological inhibition of F-actin polymerization leads to decreased lamellipodial and filopodial extensions and to reduced myoblast fusion. Additionally, shRNA-mediated inhibition of Nap1, a member of the WAVE actin-remodeling complex, results in accumulations of F-actin structures at the plasma membrane that are concomitant with a decrease in myoblast fusion. Our data highlight distinct and essential roles for actin cytoskeleton remodeling during mammalian myoblast fusion, provide a platform for cellular and molecular dissection of the fusion process, and suggest a functional conservation of Nap1-regulated actin-cytoskeleton remodeling during myoblast fusion between mammals and Drosophila.
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Affiliation(s)
- Scott J Nowak
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, USA
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37
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The small G-proteins Rac1 and Cdc42 are essential for myoblast fusion in the mouse. Proc Natl Acad Sci U S A 2009; 106:8935-40. [PMID: 19443691 DOI: 10.1073/pnas.0902501106] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Rac1 and Cdc42 are small G-proteins that regulate actin dynamics and affect plasma membrane protrusion and vesicle traffic. We used conditional mutagenesis in mice to demonstrate that Rac1 and Cdc42 are essential for myoblast fusion in vivo and in vitro. The deficit in fusion of Rac1 or Cdc42 mutant myoblasts correlates with a deficit in the recruitment of actin fibers and vinculin to myoblast contact sites. Comparison of the changes observed in mutant myogenic cells indicates that Rac1 and Cdc42 function in a nonredundant and not completely overlapping manner during the fusion process. Our genetic analysis demonstrates thus that the function of Rac in myoblast fusion is evolutionarily conserved from insects to mammals and that Cdc42, a molecule hitherto not implicated in myoblast fusion, is essential for the fusion of murine myoblasts.
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38
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Guerin CM, Kramer SG. RacGAP50C directs perinuclear gamma-tubulin localization to organize the uniform microtubule array required for Drosophila myotube extension. Development 2009; 136:1411-21. [PMID: 19297411 DOI: 10.1242/dev.031823] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The microtubule (MT) cytoskeleton is reorganized during myogenesis as individual myoblasts fuse into multinucleated myotubes. Although this reorganization has long been observed in cell culture, these findings have not been validated during development, and proteins that regulate this process are largely unknown. We have identified a novel postmitotic function for the cytokinesis proteins RacGAP50C (Tumbleweed) and Pavarotti as essential regulators of MT organization during Drosophila myogenesis. We show that the localization of the MT nucleator gamma-tubulin changes from diffuse cytoplasmic staining in mononucleated myoblasts to discrete cytoplasmic puncta at the nuclear periphery in multinucleated myoblasts, and that this change in localization depends on RacGAP50C. RacGAP50C and gamma-tubulin colocalize at perinuclear sites in myotubes, and in RacGAP50C mutants gamma-tubulin remains dispersed throughout the cytoplasm. Furthermore, we show that the mislocalization of RacGAP50C in pavarotti mutants is sufficient to redistribute gamma-tubulin to the muscle fiber ends. Finally, myotubes in RacGAP50C mutants have MTs with non-uniform polarity, resulting in multiple guidance errors. Taken together, these findings provide strong evidence that the reorganization of the MT network that has been observed in vitro plays an important role in myotube extension and muscle patterning in vivo, and also identify two molecules crucial for this process.
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Affiliation(s)
- Colleen M Guerin
- Department of Pathology and Laboratory Medicine, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USA
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