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Lübke S, Braukmann C, Rexer KH, Cigoja L, Rout P, Önel SF. The Abl-interactor Abi suppresses the function of the BRAG2 GEF family member Schizo. Biol Open 2024; 13:bio058666. [PMID: 34897417 PMCID: PMC10810563 DOI: 10.1242/bio.058666] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 11/27/2021] [Indexed: 11/20/2022] Open
Abstract
Guanine nucleotide exchange factors (GEF) of the BRAG subfamily activate small Arf GTPases, which are pivotal regulators of intracellular membrane traffic and actin dynamics. Consequently, BRAG proteins have been implicated to regulate the surface levels of adhesive and signaling receptors. However, not much is known about the mechanism leading to the regulation of these surface proteins. In this study, we found that the Drosophila BRAG GEF Schizo interacts physically with the Abl-interactor (Abi). schizo mutants display severe defects in myoblast fusion during syncytial muscle formation and show increased amounts of the cell adhesion protein N-cadherin. We demonstrate that the schizo myoblast fusion phenotype can be rescued by the expression of the Schizo GEF (Sec7) and membrane-binding (pleckstrin homology) domain. Furthermore, the expression of the Sec7-PH domain in a wild-type background decreases the amounts of N-cadherin and impairs myoblast fusion. These findings support the notion that the Sec7-PH domain serves as a constitutive-active form of Schizo. Using a yeast-two hybrid assay, we show that the SH3 domain of Abi interacts with the N-terminal region of Schizo. This region is also able to bind to the cytodomain of the cell adhesion molecule N-cadherin. To shed light on the function of Schizo and Abi in N-cadherin removal, we employed epistasis experiments in different developmental contexts of Drosophila. These studies point towards a new model for the regulation of Schizo. We propose that the binding of Abi to the N-terminal part of Schizo antagonizes Schizo function to inhibit N-cadherin removal.
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Affiliation(s)
- Stefanie Lübke
- Fachbereich Medizin, Department for Molecular Cell Physiology, Institute for Physiology and Pathophysiology, Philipps-Universität Marburg, Emil-Mannkopff-Str. 2, 35037 Marburg, Germany
- Fachbereich Biologie, Department for Developmental Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany
| | - Carina Braukmann
- Fachbereich Biologie, Department for Developmental Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
| | - Karl-Heinz Rexer
- Fachbereich Biologie, Department for Biodiversity of Plants, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
| | - Lubjinka Cigoja
- Fachbereich Biologie, Department for Developmental Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
| | - Pratiti Rout
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany
- Fachbereich Biologie, Department for Molecular Embryology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
| | - Susanne F. Önel
- Fachbereich Medizin, Department for Molecular Cell Physiology, Institute for Physiology and Pathophysiology, Philipps-Universität Marburg, Emil-Mannkopff-Str. 2, 35037 Marburg, Germany
- Fachbereich Biologie, Department for Developmental Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps-Universität Marburg, Marburg, Germany
- Fachbereich Biologie, Department for Molecular Embryology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35043 Marburg, Germany
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2
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Li S, Wang Z, Chen M, Xiao Y, Min J, Hu M, Tang J, Hong L. ArfGAP3 regulates vesicle transport and glucose uptake in myoblasts. Cell Signal 2023; 103:110551. [PMID: 36476390 DOI: 10.1016/j.cellsig.2022.110551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 11/19/2022] [Accepted: 11/30/2022] [Indexed: 12/12/2022]
Abstract
Skeletal muscle injuries are common, and damaged myofibers are repaired through proliferation and differentiation of muscle satellite cells. GLUT4 is enriched in GLUT4 storage vesicles (GSVs) and plays a crucial role in the maintenance of muscle function. ArfGAP3 regulates the vesicle transport especially for COPI coat assembly, but its effects on GSVs and the repair process after skeletal muscle injury remains unclear. In this study, datasets related to skeletal muscle injury and myoblast differentiation GSE469, GSE5413, GSE45577 and GSE108040 were retrieved through the GEO database and the expression of heptameric coat protein complex I (COPI) and Golgi vesicle transport-related genes in various datasets, as well as the expression correlation between ArfGAP2, ArfGAP3 and COPI-related genes COPA, COPB1, COPB2, COPE, COPZ1, COPZ2 were analyzed. The results suggested that ArfGAP3 was expressed in the process of repair after skeletal muscle injury and myoblast differentiation and that ArfGAP3 was positively correlated with COPI-related genes. In vitro experimental results showed that ArfGAP3 was colocalized with COPA, COPB, COPG protein, and GLUT4 in C2C12 myoblasts. After the downregulation of ArfGAP3 expression, intracellular vesicle transport, and glucose uptake were blocked, the proliferation of myoblasts under low glucose culture conditions was impaired, the proportion of apoptosis increased, and myotube differentiation was impaired. In summary, ArfGAP3 regulates COPI-associated vesicle and GSVs transport and affects the proliferation and differentiation ability of myoblasts by influencing glucose uptake, thereby modulating the repair process after skeletal muscle injury.
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Affiliation(s)
- Suting Li
- Department of Gynecology and Obstetrics, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, People's Republic of China
| | - Zhi Wang
- Department of Gynecology and Obstetrics, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, People's Republic of China
| | - Mao Chen
- Department of Gynecology and Obstetrics, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, People's Republic of China
| | - Ya Xiao
- Department of Gynecology and Obstetrics, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, People's Republic of China
| | - Jie Min
- Department of Gynecology and Obstetrics, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, People's Republic of China
| | - Ming Hu
- Department of Gynecology and Obstetrics, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, People's Republic of China
| | - Jianming Tang
- Department of Gynecology and Obstetrics, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, People's Republic of China
| | - Li Hong
- Department of Gynecology and Obstetrics, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, People's Republic of China.
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Drosophila melanogaster: A Model System to Study Distinct Genetic Programs in Myoblast Fusion. Cells 2022; 11:cells11030321. [PMID: 35159130 PMCID: PMC8834112 DOI: 10.3390/cells11030321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 11/25/2022] Open
Abstract
Muscle fibers are multinucleated cells that arise during embryogenesis through the fusion of mononucleated myoblasts. Myoblast fusion is a lifelong process that is crucial for the growth and regeneration of muscles. Understanding the molecular mechanism of myoblast fusion may open the way for novel therapies in muscle wasting and weakness. Recent reports in Drosophila and mammals have provided new mechanistic insights into myoblast fusion. In Drosophila, muscle formation occurs twice: during embryogenesis and metamorphosis. A fundamental feature is the formation of a cell–cell communication structure that brings the apposing membranes into close proximity and recruits possible fusogenic proteins. However, genetic studies suggest that myoblast fusion in Drosophila is not a uniform process. The complexity of the players involved in myoblast fusion can be modulated depending on the type of muscle that is formed. In this review, we introduce the different types of multinucleated muscles that form during Drosophila development and provide an overview in advances that have been made to understand the mechanism of myoblast fusion. Finally, we will discuss conceptual frameworks in cell–cell fusion in Drosophila and mammals.
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Zhu KC, Liu BS, Guo HY, Zhang N, Guo L, Jiang SG, Zhang DC. Functional analysis of two MyoDs revealed their role in the activation of myomixer expression in yellowfin seabream (Acanthopagrus latus) (Hottuyn, 1782). Int J Biol Macromol 2020; 156:1081-1090. [PMID: 31756488 DOI: 10.1016/j.ijbiomac.2019.11.139] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 10/11/2019] [Accepted: 11/17/2019] [Indexed: 11/24/2022]
Abstract
Myoblast determination protein (MyoD), a muscle-specific basic helix-loop-helix (bHLH) transcription factor, plays a pivotal role in regulating skeletal muscle growth and development. However, the regulation mechanism of MyoD has not been determined in marine fishes. In the present study, we isolated the MyoD1 (AlMyoD1) and MyoD2 (AlMyoD2) genomic sequences and analyzed the expression patterns in different tissues of yellowfin seabream (Acanthopagrus latus). The open reading frame (ORF) sequences of AlMyoD1 and AlMyoD2 encoded 297 and 271 amino acids possessing three common characteristic domains, respectively, containing a myogenic basic domain, a bHLH domain, and a ser-rich region (helix III). Phylogenetic and genome structure analyses exhibited classic phylogeny and highly conserved exon/intron architecture. Furthermore, the AlMyoD1 and AlMyoD2 transcription levels were higher in white muscle than in the other tissues. In order to further study AlMyoD function in muscle, promoter sequence analysis found that several E-box binding sites were present. Additionally, binding sites of Almyomixer involved in mammal myoblast fusion, which expression was also the highest in white muscle, were found in the promoter of AlMyoD. Pomoter activity assays further confirmed that both AlMyoD1 and AlMyoD2 can dramatically activate Almyomixer expression, and the AlMyoD1 M2 and AlMyoD2 M5 E-box binding sites were functionally important for Almyomixer transcription based on mutation analysis and electrophoretic mobile shift assays (EMSA). In summary, two MyoDs play a core role in Almyomixer regulation and may promote myofibre formation during muscle development and growth by regulating Almyomixer expression.
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Affiliation(s)
- Ke-Cheng Zhu
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 510300 Guangzhou, Guangdong Province, PR China; Guangdong Provincial Engineer Technology Research Center of Marine Biological Seed Industry, Guangzhou, Guangdong Province, PR China; Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Guangzhou, Guangdong Province, PR China
| | - Bao-Suo Liu
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 510300 Guangzhou, Guangdong Province, PR China; Guangdong Provincial Engineer Technology Research Center of Marine Biological Seed Industry, Guangzhou, Guangdong Province, PR China; Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Guangzhou, Guangdong Province, PR China
| | - Hua-Yang Guo
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 510300 Guangzhou, Guangdong Province, PR China; Guangdong Provincial Engineer Technology Research Center of Marine Biological Seed Industry, Guangzhou, Guangdong Province, PR China; Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Guangzhou, Guangdong Province, PR China
| | - Nan Zhang
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 510300 Guangzhou, Guangdong Province, PR China; Guangdong Provincial Engineer Technology Research Center of Marine Biological Seed Industry, Guangzhou, Guangdong Province, PR China; Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Guangzhou, Guangdong Province, PR China
| | - Liang Guo
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 510300 Guangzhou, Guangdong Province, PR China; Guangdong Provincial Engineer Technology Research Center of Marine Biological Seed Industry, Guangzhou, Guangdong Province, PR China; Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Guangzhou, Guangdong Province, PR China
| | - Shi-Gui Jiang
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 510300 Guangzhou, Guangdong Province, PR China; Guangdong Provincial Engineer Technology Research Center of Marine Biological Seed Industry, Guangzhou, Guangdong Province, PR China; Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Guangzhou, Guangdong Province, PR China
| | - Dian-Chang Zhang
- Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 510300 Guangzhou, Guangdong Province, PR China; Guangdong Provincial Engineer Technology Research Center of Marine Biological Seed Industry, Guangzhou, Guangdong Province, PR China; Guangdong Provincial Key Laboratory of Fishery Ecology and Environment, Guangzhou, Guangdong Province, PR China.
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Abstract
Cell-cell fusion is indispensable for creating life and building syncytial tissues and organs. Ever since the discovery of cell-cell fusion, how cells join together to form zygotes and multinucleated syncytia has remained a fundamental question in cell and developmental biology. In the past two decades, Drosophila myoblast fusion has been used as a powerful genetic model to unravel mechanisms underlying cell-cell fusion in vivo. Many evolutionarily conserved fusion-promoting factors have been identified and so has a surprising and conserved cellular mechanism. In this review, we revisit key findings in Drosophila myoblast fusion and highlight the critical roles of cellular invasion and resistance in driving cell membrane fusion.
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Affiliation(s)
- Donghoon M Lee
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA;
| | - Elizabeth H Chen
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA;
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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6
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Abstract
Cell-cell fusion is a fundamental process underlying fertilization, development, regeneration and physiology of metazoans. It is a multi-step process involving cell recognition and adhesion, actin cytoskeletal rearrangements, fusogen engagement, lipid mixing and fusion pore formation, ultimately resulting in the integration of two fusion partners. Here, we focus on the asymmetric actin cytoskeletal rearrangements at the site of fusion, known as the fusogenic synapse, which was first discovered during myoblast fusion in Drosophila embryos and later also found in mammalian muscle and non-muscle cells. At the asymmetric fusogenic synapse, actin-propelled invasive membrane protrusions from an attacking fusion partner trigger actomyosin-based mechanosensory responses in the receiving cell. The interplay between the invasive and resisting forces generated by the two fusion partners puts the fusogenic synapse under high mechanical tension and brings the two cell membranes into close proximity, promoting the engagement of fusogens to initiate fusion pore formation. In this Cell Science at a Glance article and the accompanying poster, we highlight the molecular, cellular and biophysical events at the asymmetric fusogenic synapse using Drosophila myoblast fusion as a model.
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Affiliation(s)
- Ji Hoon Kim
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Elizabeth H Chen
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA .,Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA
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RNAi Screen in Tribolium Reveals Involvement of F-BAR Proteins in Myoblast Fusion and Visceral Muscle Morphogenesis in Insects. G3-GENES GENOMES GENETICS 2019; 9:1141-1151. [PMID: 30733382 PMCID: PMC6469413 DOI: 10.1534/g3.118.200996] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In a large-scale RNAi screen in Tribolium castaneum for genes with knock-down phenotypes in the larval somatic musculature, one recurring phenotype was the appearance of larval muscle fibers that were significantly thinner than those in control animals. Several of the genes producing this knock-down phenotype corresponded to orthologs of Drosophila genes that are known to participate in myoblast fusion, particularly via their effects on actin polymerization. A new gene previously not implicated in myoblast fusion but displaying a similar thin-muscle knock-down phenotype was the Tribolium ortholog of Nostrin, which encodes an F-BAR and SH3 domain protein. Our genetic studies of Nostrin and Cip4, a gene encoding a structurally related protein, in Drosophila show that the encoded F-BAR proteins jointly contribute to efficient myoblast fusion during larval muscle development. Together with the F-Bar protein Syndapin they are also required for normal embryonic midgut morphogenesis. In addition, Cip4 is required together with Nostrin during the profound remodeling of the midgut visceral musculature during metamorphosis. We propose that these F-Bar proteins help govern proper morphogenesis particularly of the longitudinal midgut muscles during metamorphosis.
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Valer FB, Machado MCR, Silva-Junior RMP, Ramos RGP. Expression of Hbs, Kirre, and Rst during Drosophila ovarian development. Genesis 2018; 56:e23242. [PMID: 30114331 DOI: 10.1002/dvg.23242] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Revised: 07/22/2018] [Accepted: 07/23/2018] [Indexed: 12/16/2022]
Abstract
The Irre cell-recognition module (IRM) is a group of evolutionarily conserved and structurally related transmembrane glycoproteins of the immunoglobulin superfamily. In Drosophila melanogaster, it comprises the products of the genes roughest (rst; also known as irreC-rst), kin-of-irre (kirre; also known as duf), sticks-and-stones (sns), and hibris (hbs). In this model organism, the behavior of this group of proteins as a partly redundant functional unit mediating selective cell recognition was demonstrated in a variety of developmental contexts, but their possible involvement in ovarian development and oogenesis has not been investigated, notwithstanding the fact that some rst mutant alleles are also female sterile. Here, we show that IRM genes are dynamically and, to some extent, coordinately transcribed in both pupal and adult ovaries. Additionally, the spatial distribution of Hbs, Kirre, and Rst proteins indicates that they perform cooperative, although largely nonredundant, functions. Finally, phenotypical characterization of three different female sterile rst alleles uncovered two temporally separated and functionally distinct requirements for this locus in ovarian development: one in pupa, essential for the organization of peritoneal and epithelial sheaths that maintain the structural integrity of the adult organ and another, in mature ovarioles, needed for the progression of oogenesis beyond stage 10.
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Affiliation(s)
- Felipe Berti Valer
- Department of Cellular and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Maiaro Cabral Rosa Machado
- Department of Cellular and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
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Serrano A, Illgen J, Brandt U, Thieme N, Letz A, Lichius A, Read ND, Fleißner A. Spatio-temporal MAPK dynamics mediate cell behavior coordination during fungal somatic cell fusion. J Cell Sci 2018; 131:jcs.213462. [PMID: 29592970 DOI: 10.1242/jcs.213462] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 03/20/2018] [Indexed: 01/17/2023] Open
Abstract
Mitogen-activated protein kinases (MAPKs) are conserved regulators of proliferation, differentiation and adaptation in eukaryotic cells. Their activity often involves changes in their subcellular localization, indicating an important role for these spatio-temporal dynamics in signal transmission. A striking model illustrating these dynamics is somatic cell fusion in Neurospora crassa Germinating spores of this fungus rapidly alternate between signal sending and receiving, thereby establishing a cell-cell dialog, which involves the alternating membrane recruitment of the MAPK MAK-2 in both fusion partners. Here, we show that the dynamic translocation of MAK-2 is essential for coordinating the behavior of the fusion partners before physical contact. The activation and function of the kinase strongly correlate with its subcellular localization, indicating a crucial contribution of the MAPK dynamics in establishing regulatory feedback loops, which establish the oscillatory signaling mode. In addition, we provide evidence that MAK-2 not only contributes to cell-cell communication, but also mediates cell-cell fusion. The MAK-2 dynamics significantly differ between these two processes, suggesting a role for the MAPK in switching of the cellular program between communication and fusion.
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Affiliation(s)
- Antonio Serrano
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Julia Illgen
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Ulrike Brandt
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Nils Thieme
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Anja Letz
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
| | - Alexander Lichius
- Institute of Microbiology, University of Innsbruck, 6020 Innsbruck, Austria
| | - Nick D Read
- Manchester Fungal Infection Group, Division of Infection, Immunity and Respiratory Medicine, University of Manchester, Manchester M13 9NT, UK
| | - André Fleißner
- Institut für Genetik, Technische Universität Braunschweig, Spielmannstraße 7, 38106 Braunschweig, Germany
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Abstract
Cell-cell fusion is essential for fertilization and organ development. Dedicated proteins known as fusogens are responsible for mediating membrane fusion. However, until recently, these proteins either remained unidentified or were poorly understood at the mechanistic level. Here, we review how fusogens surmount multiple energy barriers to mediate cell-cell fusion. We describe how early preparatory steps bring membranes to a distance of ∼10 nm, while fusogens act in the final approach between membranes. The mechanical force exerted by cell fusogens and the accompanying lipidic rearrangements constitute the hallmarks of cell-cell fusion. Finally, we discuss the relationship between viral and eukaryotic fusogens, highlight a classification scheme regrouping a superfamily of fusogens called Fusexins, and propose new questions and avenues of enquiry.
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Affiliation(s)
- Javier M Hernández
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, D-44227 Dortmund, Germany
| | - Benjamin Podbilewicz
- Department of Biology, Technion - Israel Institute of Technology, Haifa 32000, Israel
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Deng S, Azevedo M, Baylies M. Acting on identity: Myoblast fusion and the formation of the syncytial muscle fiber. Semin Cell Dev Biol 2017; 72:45-55. [PMID: 29101004 DOI: 10.1016/j.semcdb.2017.10.033] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/25/2017] [Accepted: 10/30/2017] [Indexed: 12/25/2022]
Abstract
The study of Drosophila muscle development dates back to the middle of the last century. Since that time, Drosophila has proved to be an ideal system for studying muscle development, differentiation, function, and disease. As in humans, Drosophila muscle forms via a series of conserved steps, starting with muscle specification, myoblast fusion, attachment to tendon cells, interactions with motorneurons, and sarcomere and myofibril formation. The genes and mechanisms required for these processes share striking similarities to those found in humans. The highly tractable genetic system and imaging approaches available in Drosophila allow for an efficient interrogation of muscle biology and for application of what we learn to other systems. In this article, we review our current understanding of muscle development in Drosophila, with a focus on myoblast fusion, the process responsible for the generation of syncytial muscle cells. We also compare and contrast those genes required for fusion in Drosophila and vertebrates.
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Affiliation(s)
- Su Deng
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, United States
| | - Mafalda Azevedo
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, United States; Graduate Program in Basic and Applied Biology (GABBA), Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto, Portugal
| | - Mary Baylies
- Program in Developmental Biology, Sloan Kettering Institute, New York, NY 10065, United States.
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12
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Schejter ED. Myoblast fusion: Experimental systems and cellular mechanisms. Semin Cell Dev Biol 2016; 60:112-120. [DOI: 10.1016/j.semcdb.2016.07.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2016] [Revised: 07/11/2016] [Accepted: 07/12/2016] [Indexed: 12/18/2022]
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Hamp J, Löwer A, Dottermusch-Heidel C, Beck L, Moussian B, Flötenmeyer M, Önel SF. Drosophila Kette coordinates myoblast junction dissolution and the ratio of Scar-to-WASp during myoblast fusion. J Cell Sci 2016; 129:3426-36. [PMID: 27521427 PMCID: PMC5047678 DOI: 10.1242/jcs.175638] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 07/25/2016] [Indexed: 12/31/2022] Open
Abstract
The fusion of founder cells and fusion-competent myoblasts (FCMs) is crucial for muscle formation in Drosophila. Characteristic events of myoblast fusion include the recognition and adhesion of myoblasts, and the formation of branched F-actin by the Arp2/3 complex at the site of cell–cell contact. At the ultrastructural level, these events are reflected by the appearance of finger-like protrusions and electron-dense plaques that appear prior to fusion. Severe defects in myoblast fusion are caused by the loss of Kette (a homolog of Nap1 and Hem-2, also known as NCKAP1 and NCKAP1L, respectively), a member of the regulatory complex formed by Scar or WAVE proteins (represented by the single protein, Scar, in flies). kette mutants form finger-like protrusions, but the electron-dense plaques are extended. Here, we show that the electron-dense plaques in wild-type and kette mutant myoblasts resemble other electron-dense structures that are known to function as cellular junctions. Furthermore, analysis of double mutants and attempts to rescue the kette mutant phenotype with N-cadherin, wasp and genes of members of the regulatory Scar complex revealed that Kette has two functions during myoblast fusion. First, Kette controls the dissolution of electron-dense plaques. Second, Kette controls the ratio of the Arp2/3 activators Scar and WASp in FCMs. Summary: The Drosophila protein Kette is essential for myoblast fusion. It controls the dissolution of electron-dense plaques and the ratio of Scar and WASp proteins in fusion-competent myoblasts during fusion pore formation.
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Affiliation(s)
- Julia Hamp
- Philipps-Universität Marburg, FB Biologie, Entwicklungsbiologie, Karl-von-Frisch Str. 8, Marburg 35043, Germany
| | - Andreas Löwer
- Philipps-Universität Marburg, FB Biologie, Entwicklungsbiologie, Karl-von-Frisch Str. 8, Marburg 35043, Germany
| | | | - Lothar Beck
- Fachbereich Biologie, Spezielle Zoologie, Philipps-Universität Marburg, Karl-von-Frisch Str. 8, Marburg 35043, Germany
| | - Bernard Moussian
- Interfaculty Institute for Cell Biology, Section Animal Genetics, University of Tübingen, Tübingen 72076, Germany
| | - Matthias Flötenmeyer
- Max Planck Institute for Developmental Biology, Section Electron Microscopy, Tübingen 72076, Germany
| | - Susanne-Filiz Önel
- Philipps-Universität Marburg, FB Biologie, Entwicklungsbiologie, Karl-von-Frisch Str. 8, Marburg 35043, Germany
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14
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Segal D, Dhanyasi N, Schejter ED, Shilo BZ. Adhesion and Fusion of Muscle Cells Are Promoted by Filopodia. Dev Cell 2016; 38:291-304. [DOI: 10.1016/j.devcel.2016.07.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 05/10/2016] [Accepted: 07/13/2016] [Indexed: 12/22/2022]
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Deng S, Bothe I, Baylies M. Diaphanous regulates SCAR complex localization during Drosophila myoblast fusion. Fly (Austin) 2016; 10:178-86. [PMID: 27314572 DOI: 10.1080/19336934.2016.1195938] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
From Drosophila to man, multinucleated muscle cells form through cell-cell fusion. Using Drosophila as a model system, researchers first identified, and then demonstrated, the importance of actin cytoskeletal rearrangements at the site of fusion. These actin rearrangements at the fusion site are regulated by SCAR and WASp mediated Arp2/3 activation, which nucleates branched actin networks. Loss of SCAR, WASp or both leads to defects in myoblast fusion. Recently, we have found that the actin regulator Diaphanous (Dia) also plays a role both in organizing actin and in regulating Arp2/3 activity at the fusion site. In this Extra View article, we provide additional data showing that the Abi-SCAR complex accumulates at the fusion site and that excessive SCAR activity impairs myoblast fusion. Using constitutively active Dia constructs, we provide additional evidence that Dia functions upstream of SCAR activity to regulate actin dynamics at the fusion site and to localize the Abi-SCAR complex.
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Affiliation(s)
- Su Deng
- a Graduate Program in Physiology , Biophysics & Systems Biology, Weill Cornell Graduate School of Medical Sciences, Cornell University , New York , NY , USA
| | - Ingo Bothe
- b Program in Developmental Biology , Sloan Kettering Institute , New York , NY , USA
| | - Mary Baylies
- a Graduate Program in Physiology , Biophysics & Systems Biology, Weill Cornell Graduate School of Medical Sciences, Cornell University , New York , NY , USA.,b Program in Developmental Biology , Sloan Kettering Institute , New York , NY , USA
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16
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Dhanyasi N, Segal D, Shimoni E, Shinder V, Shilo BZ, VijayRaghavan K, Schejter ED. Surface apposition and multiple cell contacts promote myoblast fusion in Drosophila flight muscles. J Cell Biol 2016; 211:191-203. [PMID: 26459604 PMCID: PMC4602036 DOI: 10.1083/jcb.201503005] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Transmission EM methods reveal that cell–cell fusion of individual myoblasts with growing Drosophila flight muscles is a stepwise process in which the cell adhesion and branched actin machineries mediate tight apposition and formation of multiple contacts and pores between the surfaces of the fusing cells. Fusion of individual myoblasts to form multinucleated myofibers constitutes a widely conserved program for growth of the somatic musculature. We have used electron microscopy methods to study this key form of cell–cell fusion during development of the indirect flight muscles (IFMs) of Drosophila melanogaster. We find that IFM myoblast–myotube fusion proceeds in a stepwise fashion and is governed by apparent cross talk between transmembrane and cytoskeletal elements. Our analysis suggests that cell adhesion is necessary for bringing myoblasts to within a minimal distance from the myotubes. The branched actin polymerization machinery acts subsequently to promote tight apposition between the surfaces of the two cell types and formation of multiple sites of cell–cell contact, giving rise to nascent fusion pores whose expansion establishes full cytoplasmic continuity. Given the conserved features of IFM myogenesis, this sequence of cell interactions and membrane events and the mechanistic significance of cell adhesion elements and the actin-based cytoskeleton are likely to represent general principles of the myoblast fusion process.
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Affiliation(s)
- Nagaraju Dhanyasi
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka 560065, India Manipal University, Manipal, Karnataka 576104, India
| | - Dagan Segal
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eyal Shimoni
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Vera Shinder
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ben-Zion Shilo
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - K VijayRaghavan
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore, Karnataka 560065, India
| | - Eyal D Schejter
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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Kuckwa J, Fritzen K, Buttgereit D, Rothenbusch-Fender S, Renkawitz-Pohl R. A new level of plasticity: Drosophila smooth-like testes muscles compensate failure of myoblast fusion. Development 2015; 143:329-38. [PMID: 26657767 PMCID: PMC4725342 DOI: 10.1242/dev.126730] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 11/28/2015] [Indexed: 12/26/2022]
Abstract
The testis of Drosophila resembles an individual testis tubule of mammals. Both are surrounded by a sheath of smooth muscles, which in Drosophila are multinuclear and originate from a pool of myoblasts that are set aside in the embryo and accumulate on the genital disc later in development. These muscle stem cells start to differentiate early during metamorphosis and give rise to all muscles of the inner male reproductive system. Shortly before the genital disc and the developing testes connect, multinuclear nascent myotubes appear on the anterior tips of the seminal vesicles. Here, we show that adhesion molecules are distinctly localized on the seminal vesicles; founder cell (FC)-like myoblasts express Dumbfounded (Duf) and Roughest (Rst), and fusion-competent myoblast (FCM)-like cells mainly express Sticks and stones (Sns). The smooth but multinuclear myotubes of the testes arose by myoblast fusion. RNAi-mediated attenuation of Sns or both Duf and Rst severely reduced the number of nuclei in the testes muscles. Duf and Rst probably act independently in this context. Despite reduced fusion in all of these RNAi-treated animals, myotubes migrated onto the testes, testes were shaped and coiled, muscle filaments were arranged as in the wild type and spermatogenesis proceeded normally. Hence, the testes muscles compensate for fusion defects so that the myofibres encircling the adult testes are indistinguishable from those of the wild type and male fertility is guaranteed. Summary:Drosophila testes muscles arise from stem cells and can compensate for fusion defects to safeguard fertility; this plasticity may compensate for the observed lack of satellite cells in Drosophila.
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Affiliation(s)
- Jessica Kuckwa
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
| | - Katharina Fritzen
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
| | - Detlev Buttgereit
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
| | - Silke Rothenbusch-Fender
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
| | - Renate Renkawitz-Pohl
- Philipps-Universität Marburg, Fachbereich Biologie, Entwicklungsbiologie, Karl-von-Frisch Strasse 8, Marburg 35043, Germany
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18
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Functional Conservation of the Glide/Gcm Regulatory Network Controlling Glia, Hemocyte, and Tendon Cell Differentiation in Drosophila. Genetics 2015; 202:191-219. [PMID: 26567182 PMCID: PMC4701085 DOI: 10.1534/genetics.115.182154] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 11/03/2015] [Indexed: 12/21/2022] Open
Abstract
High-throughput screens allow us to understand how transcription factors trigger developmental processes, including cell specification. A major challenge is identification of their binding sites because feedback loops and homeostatic interactions may mask the direct impact of those factors in transcriptome analyses. Moreover, this approach dissects the downstream signaling cascades and facilitates identification of conserved transcriptional programs. Here we show the results and the validation of a DNA adenine methyltransferase identification (DamID) genome-wide screen that identifies the direct targets of Glide/Gcm, a potent transcription factor that controls glia, hemocyte, and tendon cell differentiation in Drosophila. The screen identifies many genes that had not been previously associated with Glide/Gcm and highlights three major signaling pathways interacting with Glide/Gcm: Notch, Hedgehog, and JAK/STAT, which all involve feedback loops. Furthermore, the screen identifies effector molecules that are necessary for cell-cell interactions during late developmental processes and/or in ontogeny. Typically, immunoglobulin (Ig) domain-containing proteins control cell adhesion and axonal navigation. This shows that early and transiently expressed fate determinants not only control other transcription factors that, in turn, implement a specific developmental program but also directly affect late developmental events and cell function. Finally, while the mammalian genome contains two orthologous Gcm genes, their function has been demonstrated in vertebrate-specific tissues, placenta, and parathyroid glands, begging questions on the evolutionary conservation of the Gcm cascade in higher organisms. Here we provide the first evidence for the conservation of Gcm direct targets in humans. In sum, this work uncovers novel aspects of cell specification and sets the basis for further understanding of the role of conserved Gcm gene regulatory cascades.
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