1
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Gentile GM, Gamarra JR, Engels NM, Blue RE, Hoerr I, Wiedner HJ, Hinkle ER, Cote JL, Leverence E, Mills CA, Herring LE, Tan X, Giudice J. The synaptosome-associated protein 23 (SNAP23) is necessary for proper myogenesis. FASEB J 2022; 36:e22441. [PMID: 35816155 PMCID: PMC9836321 DOI: 10.1096/fj.202101627rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 06/17/2022] [Accepted: 06/24/2022] [Indexed: 01/14/2023]
Abstract
Vesicle-mediated transport is necessary for maintaining cellular homeostasis and proper signaling. The synaptosome-associated protein 23 (SNAP23) is a member of the SNARE protein family and mediates the vesicle docking and membrane fusion steps of secretion during exocytosis. Skeletal muscle has been established as a secretory organ; however, the role of SNAP23 in the context of skeletal muscle development is still unknown. Here, we show that depletion of SNAP23 in C2C12 mouse myoblasts reduces their ability to differentiate into myotubes as a result of premature cell cycle exit and early activation of the myogenic transcriptional program. This effect is rescued when cells are seeded at a high density or when cultured in conditioned medium from wild type cells. Proteomic analysis of collected medium indicates that SNAP23 depletion leads to a misregulation of exocytosis, including decreased secretion of the insulin-like growth factor 1 (IGF1), a critical protein for muscle growth, development, and function. We further demonstrate that treatment of SNAP23-depleted cells with exogenous IGF1 rescues their myogenic capacity. We propose that SNAP23 mediates the secretion of specific proteins, such as IGF1, that are important for achieving proper differentiation of skeletal muscle cells during myogenesis. This work highlights the underappreciated role of skeletal muscle as a secretory organ and contributes to the understanding of factors necessary for myogenesis.
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Affiliation(s)
- Gabrielle M. Gentile
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jennifer R. Gamarra
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nichlas M. Engels
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - R. Eric Blue
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Isabel Hoerr
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Hannah J. Wiedner
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Emma R. Hinkle
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jessica L. Cote
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Elise Leverence
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Christine A. Mills
- UNC Proteomics Core Facility, Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Laura E. Herring
- UNC Proteomics Core Facility, Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Xianming Tan
- Department of Biostatistics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jimena Giudice
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- McAllister Heart Institute, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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2
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Fujise K, Noguchi S, Takeda T. Centronuclear Myopathy Caused by Defective Membrane Remodelling of Dynamin 2 and BIN1 Variants. Int J Mol Sci 2022; 23:ijms23116274. [PMID: 35682949 PMCID: PMC9181712 DOI: 10.3390/ijms23116274] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 05/31/2022] [Accepted: 06/01/2022] [Indexed: 02/01/2023] Open
Abstract
Centronuclear myopathy (CNM) is a congenital myopathy characterised by centralised nuclei in skeletal myofibers. T-tubules, sarcolemmal invaginations required for excitation-contraction coupling, are disorganised in the skeletal muscles of CNM patients. Previous studies showed that various endocytic proteins are involved in T-tubule biogenesis and their dysfunction is tightly associated with CNM pathogenesis. DNM2 and BIN1 are two causative genes for CNM that encode essential membrane remodelling proteins in endocytosis, dynamin 2 and BIN1, respectively. In this review, we overview the functions of dynamin 2 and BIN1 in T-tubule biogenesis and discuss how their dysfunction in membrane remodelling leads to CNM pathogenesis.
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Affiliation(s)
- Kenshiro Fujise
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520-8001, USA;
| | - Satoru Noguchi
- National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), Tokyo 187-8502, Japan;
| | - Tetsuya Takeda
- Department of Biochemistry, Faculty of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Shikata-cho 2-5-1, Kita-ku, Okayama 700-8558, Japan
- Correspondence: ; Tel.: +81-86-235-7125; Fax: +81-86-235-7126
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3
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Espinosa KG, Geissah S, Groom L, Volpatti J, Scott IC, Dirksen RT, Zhao M, Dowling JJ. Characterization of a novel zebrafish model of SPEG-related centronuclear myopathy. Dis Model Mech 2022; 15:275324. [PMID: 35293586 PMCID: PMC9118044 DOI: 10.1242/dmm.049437] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 03/08/2022] [Indexed: 01/03/2023] Open
Abstract
Centronuclear myopathy (CNM) is a congenital neuromuscular disorder caused by pathogenic variation in genes associated with membrane trafficking and excitation–contraction coupling (ECC). Bi-allelic autosomal-recessive mutations in striated muscle enriched protein kinase (SPEG) account for a subset of CNM patients. Previous research has been limited by the perinatal lethality of constitutive Speg knockout mice. Thus, the precise biological role of SPEG in developing skeletal muscle remains unknown. To address this issue, we generated zebrafish spega, spegb and spega;spegb (speg-DKO) mutant lines. We demonstrated that speg-DKO zebrafish faithfully recapitulate multiple phenotypes associated with CNM, including disruption of the ECC machinery, dysregulation of calcium homeostasis during ECC and impairment of muscle performance. Taking advantage of zebrafish models of multiple CNM genetic subtypes, we compared novel and known disease markers in speg-DKO with mtm1-KO and DNM2-S619L transgenic zebrafish. We observed Desmin accumulation common to all CNM subtypes, and Dnm2 upregulation in muscle of both speg-DKO and mtm1-KO zebrafish. In all, we establish a new model of SPEG-related CNM, and identify abnormalities in this model suitable for defining disease pathomechanisms and evaluating potential therapies. This article has an associated First Person interview with the joint first authors of the paper. Summary: We created a novel zebrafish Speg mutant model of centronuclear myopathy that recapitulates key features of the human disorder and provides insight into pathomechanisms of the disease.
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Affiliation(s)
- Karla G Espinosa
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Medical Science Building, Room 4386, 1 King's College Cir, Toronto, ON M5S 1A8, Canada
| | - Salma Geissah
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Medical Science Building, Room 4386, 1 King's College Cir, Toronto, ON M5S 1A8, Canada
| | - Linda Groom
- Department of Pharmacology and Physiology, University of Rochester Medical Centre, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Jonathan Volpatti
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Ian C Scott
- Department of Molecular Genetics, University of Toronto, Medical Science Building, Room 4386, 1 King's College Cir, Toronto, ON M5S 1A8, Canada.,Program for Development and Stem Cell Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Centre, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Mo Zhao
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada
| | - James J Dowling
- Program for Genetics and Genome Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Medical Science Building, Room 4386, 1 King's College Cir, Toronto, ON M5S 1A8, Canada.,Department of Pediatrics, University of Toronto, Room 1436D, 555 University Avenue, Toronto, ON M5G 1X8, Canada
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4
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Hinkle ER, Wiedner HJ, Torres EV, Jackson M, Black AJ, Blue RE, Harris SE, Guzman BB, Gentile GM, Lee EY, Tsai YH, Parker J, Dominguez D, Giudice J. Alternative splicing regulation of membrane trafficking genes during myogenesis. RNA (NEW YORK, N.Y.) 2022; 28:523-540. [PMID: 35082143 PMCID: PMC8925968 DOI: 10.1261/rna.078993.121] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/17/2021] [Indexed: 06/14/2023]
Abstract
Alternative splicing transitions occur during organ development, and, in numerous diseases, splicing programs revert to fetal isoform expression. We previously found that extensive splicing changes occur during postnatal mouse heart development in genes encoding proteins involved in vesicle-mediated trafficking. However, the regulatory mechanisms of this splicing-trafficking network are unknown. Here, we found that membrane trafficking genes are alternatively spliced in a tissue-specific manner, with striated muscles exhibiting the highest levels of alternative exon inclusion. Treatment of differentiated muscle cells with chromatin-modifying drugs altered exon inclusion in muscle cells. Examination of several RNA-binding proteins revealed that the poly-pyrimidine tract binding protein 1 (PTBP1) and quaking regulate splicing of trafficking genes during myogenesis, and that removal of PTBP1 motifs prevented PTBP1 from binding its RNA target. These findings enhance our understanding of developmental splicing regulation of membrane trafficking proteins which might have implications for muscle disease pathogenesis.
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Affiliation(s)
- Emma R Hinkle
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Curriculum in Genetics and Molecular Biology (GMB), The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Hannah J Wiedner
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Curriculum in Genetics and Molecular Biology (GMB), The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Eduardo V Torres
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Micaela Jackson
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Adam J Black
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - R Eric Blue
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Sarah E Harris
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Bryan B Guzman
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Gabrielle M Gentile
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Curriculum in Genetics and Molecular Biology (GMB), The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Eunice Y Lee
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Yi-Hsuan Tsai
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Joel Parker
- Curriculum in Genetics and Molecular Biology (GMB), The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Daniel Dominguez
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Jimena Giudice
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Curriculum in Genetics and Molecular Biology (GMB), The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- McAllister Heart Institute, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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5
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Molecular and cellular basis of genetically inherited skeletal muscle disorders. Nat Rev Mol Cell Biol 2021; 22:713-732. [PMID: 34257452 PMCID: PMC9686310 DOI: 10.1038/s41580-021-00389-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2021] [Indexed: 02/06/2023]
Abstract
Neuromuscular disorders comprise a diverse group of human inborn diseases that arise from defects in the structure and/or function of the muscle tissue - encompassing the muscle cells (myofibres) themselves and their extracellular matrix - or muscle fibre innervation. Since the identification in 1987 of the first genetic lesion associated with a neuromuscular disorder - mutations in dystrophin as an underlying cause of Duchenne muscular dystrophy - the field has made tremendous progress in understanding the genetic basis of these diseases, with pathogenic variants in more than 500 genes now identified as underlying causes of neuromuscular disorders. The subset of neuromuscular disorders that affect skeletal muscle are referred to as myopathies or muscular dystrophies, and are due to variants in genes encoding muscle proteins. Many of these proteins provide structural stability to the myofibres or function in regulating sarcolemmal integrity, whereas others are involved in protein turnover, intracellular trafficking, calcium handling and electrical excitability - processes that ensure myofibre resistance to stress and their primary activity in muscle contraction. In this Review, we discuss how defects in muscle proteins give rise to muscle dysfunction, and ultimately to disease, with a focus on pathologies that are most common, best understood and that provide the most insight into muscle biology.
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6
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Gutiérrez-Pérez P, Santillán EM, Lendl T, Wang J, Schrempf A, Steinacker TL, Asparuhova M, Brandstetter M, Haselbach D, Cochella L. miR-1 sustains muscle physiology by controlling V-ATPase complex assembly. SCIENCE ADVANCES 2021; 7:eabh1434. [PMID: 34652942 PMCID: PMC8519577 DOI: 10.1126/sciadv.abh1434] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 08/23/2021] [Indexed: 05/13/2023]
Abstract
Muscle function requires unique structural and metabolic adaptations that can render muscle cells selectively vulnerable, with mutations in some ubiquitously expressed genes causing myopathies but sparing other tissues. We uncovered a muscle cell vulnerability by studying miR-1, a deeply conserved, muscle-specific microRNA whose ablation causes various muscle defects. Using Caenorhabditis elegans, we found that miR-1 represses multiple subunits of the ubiquitous vacuolar adenosine triphosphatase (V-ATPase) complex, which is essential for internal compartment acidification and metabolic signaling. V-ATPase subunits are predicted miR-1 targets in animals ranging from C. elegans to humans, and we experimentally validated this in Drosophila. Unexpectedly, up-regulation of V-ATPase subunits upon miR-1 deletion causes reduced V-ATPase function due to defects in complex assembly. These results reveal V-ATPase assembly as a conserved muscle cell vulnerability and support a previously unknown role for microRNAs in the regulation of protein complexes.
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Affiliation(s)
- Paula Gutiérrez-Pérez
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, 1030 Vienna, Austria
| | - Emilio M. Santillán
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, 1030 Vienna, Austria
| | - Thomas Lendl
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Jingkui Wang
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Anna Schrempf
- Research Center for Molecular Medicine of the Austrian Academy of Sciences, 1090 Vienna, Austria
| | | | - Mila Asparuhova
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Marlene Brandstetter
- Electron Microscopy Facility, Vienna BioCenter Core Facilities GmbH, Vienna, Austria
| | - David Haselbach
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Luisa Cochella
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
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7
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Smith L, Fabian L, Al-Maawali A, Noche RR, Dowling JJ. De novo phosphoinositide synthesis in zebrafish is required for triad formation but not essential for myogenesis. PLoS One 2020; 15:e0231364. [PMID: 32804943 PMCID: PMC7430711 DOI: 10.1371/journal.pone.0231364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 08/01/2020] [Indexed: 11/18/2022] Open
Abstract
Phosphoinositides (PIPs) and their regulatory enzymes are key players in many cellular processes and are required for aspects of vertebrate development. Dysregulated PIP metabolism has been implicated in several human diseases, including a subset of skeletal myopathies that feature structural defects in the triad. The role of PIPs in skeletal muscle formation, and particularly triad biogenesis, has yet to be determined. CDP-diacylglycerol-inositol 3-phosphatidyltransferase (CDIPT) catalyzes the formation of phosphatidylinositol, which is the base of all PIP species. Loss of CDIPT should, in theory, result in the failure to produce PIPs, and thus provide a strategy for establishing the requirement for PIPs during embryogenesis. In this study, we generated cdipt mutant zebrafish and determined the impact on skeletal myogenesis. Analysis of cdipt mutant muscle revealed no apparent global effect on early muscle development. However, small but significant defects were observed in triad size, with T-tubule area, inter terminal cisternae distance and gap width being smaller in cdipt mutants. This was associated with a decrease in motor performance. Overall, these data suggest that myogenesis in zebrafish does not require de novo PIP synthesis but does implicate a role for CDIPT in triad formation.
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Affiliation(s)
- Lindsay Smith
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Ontario Institute for Cancer Research, Toronto, Ontario, Canada
| | - Lacramioara Fabian
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Almundher Al-Maawali
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Genetics, College of Medicine and Health Sciences, Sultan Qaboos University & Sultan Qaboos University Hospital, Muscat, Oman
| | - Ramil R. Noche
- Zebrafish Genetics and Disease Models Core Facility, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - James J. Dowling
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Division of Neurology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Departments of Paediatrics and Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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8
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Blue RE, Curry EG, Engels NM, Lee EY, Giudice J. How alternative splicing affects membrane-trafficking dynamics. J Cell Sci 2018; 131:jcs216465. [PMID: 29769303 PMCID: PMC6031328 DOI: 10.1242/jcs.216465] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The cell biology field has outstanding working knowledge of the fundamentals of membrane-trafficking pathways, which are of critical importance in health and disease. Current challenges include understanding how trafficking pathways are fine-tuned for specialized tissue functions in vivo and during development. In parallel, the ENCODE project and numerous genetic studies have revealed that alternative splicing regulates gene expression in tissues and throughout development at a post-transcriptional level. This Review summarizes recent discoveries demonstrating that alternative splicing affects tissue specialization and membrane-trafficking proteins during development, and examines how this regulation is altered in human disease. We first discuss how alternative splicing of clathrin, SNAREs and BAR-domain proteins influences endocytosis, secretion and membrane dynamics, respectively. We then focus on the role of RNA-binding proteins in the regulation of splicing of membrane-trafficking proteins in health and disease. Overall, our aim is to comprehensively summarize how trafficking is molecularly influenced by alternative splicing and identify future directions centered on its physiological relevance.
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Affiliation(s)
- R Eric Blue
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ennessa G Curry
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nichlas M Engels
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Eunice Y Lee
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jimena Giudice
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- McAllister Heart Institute, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology (GMB), The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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9
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Giudice J, Loehr JA, Rodney GG, Cooper TA. Alternative Splicing of Four Trafficking Genes Regulates Myofiber Structure and Skeletal Muscle Physiology. Cell Rep 2017; 17:1923-1933. [PMID: 27851958 DOI: 10.1016/j.celrep.2016.10.072] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Revised: 09/02/2016] [Accepted: 10/20/2016] [Indexed: 11/16/2022] Open
Abstract
During development, transcriptional and post-transcriptional networks are coordinately regulated to drive organ maturation. Alternative splicing contributes by producing temporal-specific protein isoforms. We previously found that genes undergoing splicing transitions during mouse postnatal heart development are enriched for vesicular trafficking and membrane dynamics functions. Here, we show that adult trafficking isoforms are also expressed in adult skeletal muscle and hypothesize that striated muscle utilizes alternative splicing to generate specific isoforms required for function of adult tissue. We deliver morpholinos into flexor digitorum brevis muscles in adult mice to redirect splicing of four trafficking genes to the fetal isoforms. The splicing switch results in multiple structural and functional defects, including transverse tubule (T-tubule) disruption and dihydropyridine receptor alpha (DHPR) and Ryr1 mislocalization, impairing excitation-contraction coupling, calcium handling, and force generation. The results demonstrate a previously unrecognized role for trafficking functions in adult muscle tissue homeostasis and a specific requirement for the adult splice variants.
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Affiliation(s)
- Jimena Giudice
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA; Department of Cell Biology and Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; McAllister Heart Institute, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - James A Loehr
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - George G Rodney
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Thomas A Cooper
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA; Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX 77030, USA; Department of Molecular & Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
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10
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González-Jamett AM, Baez-Matus X, Olivares MJ, Hinostroza F, Guerra-Fernández MJ, Vasquez-Navarrete J, Bui MT, Guicheney P, Romero NB, Bevilacqua JA, Bitoun M, Caviedes P, Cárdenas AM. Dynamin-2 mutations linked to Centronuclear Myopathy impair actin-dependent trafficking in muscle cells. Sci Rep 2017; 7:4580. [PMID: 28676641 PMCID: PMC5496902 DOI: 10.1038/s41598-017-04418-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 05/16/2017] [Indexed: 12/20/2022] Open
Abstract
Dynamin-2 is a ubiquitously expressed GTP-ase that mediates membrane remodeling. Recent findings indicate that dynamin-2 also regulates actin dynamics. Mutations in dynamin-2 cause dominant centronuclear myopathy (CNM), a congenital myopathy characterized by progressive weakness and atrophy of skeletal muscles. However, the muscle-specific roles of dynamin-2 affected by these mutations remain elusive. Here we show that, in muscle cells, the GTP-ase activity of dynamin-2 is involved in de novo actin polymerization as well as in actin-mediated trafficking of the glucose transporter GLUT4. Expression of dynamin-2 constructs carrying CNM-linked mutations disrupted the formation of new actin filaments as well as the stimulus-induced translocation of GLUT4 to the plasma membrane. Similarly, mature muscle fibers isolated from heterozygous knock-in mice that harbor the dynamin-2 mutation p.R465W, an animal model of CNM, exhibited altered actin organization, reduced actin polymerization and impaired insulin-induced translocation of GLUT4 to the sarcolemma. Moreover, GLUT4 displayed aberrant perinuclear accumulation in biopsies from CNM patients carrying dynamin-2 mutations, further suggesting trafficking defects. These results suggest that dynamin-2 is a key regulator of actin dynamics and GLUT4 trafficking in muscle cells. Our findings also support a model in which impairment of actin-dependent trafficking contributes to the pathological mechanism in dynamin-2-associated CNM.
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Affiliation(s)
- Arlek M González-Jamett
- Centro Interdisciplinario de Neurociencia de Valparaíso. Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile. .,Programa de Farmacología Molecular y Clinica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
| | - Ximena Baez-Matus
- Centro Interdisciplinario de Neurociencia de Valparaíso. Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - María José Olivares
- Centro Interdisciplinario de Neurociencia de Valparaíso. Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Fernando Hinostroza
- Centro Interdisciplinario de Neurociencia de Valparaíso. Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.,Doctorado en Ciencias, mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - Maria José Guerra-Fernández
- Centro Interdisciplinario de Neurociencia de Valparaíso. Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Jacqueline Vasquez-Navarrete
- Centro Interdisciplinario de Neurociencia de Valparaíso. Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Mai Thao Bui
- Université Sorbonne, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, Paris, France.,Centre de référence de Pathologie Neuromusculaire Paris-Est, Institut de Myologie, GHU Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, GH Pitié-Salpêtrière, Paris, France
| | - Pascale Guicheney
- INSERM, UMR_S1166, Sorbonne Universités, UPMC Univ Paris 06, UMR_S1166, Institute of Cardiometabolism and Nutrition (ICAN), Paris, France
| | - Norma Beatriz Romero
- Université Sorbonne, UPMC Univ Paris 06, INSERM UMRS974, CNRS FRE3617, Center for Research in Myology, Paris, France.,Centre de référence de Pathologie Neuromusculaire Paris-Est, Institut de Myologie, GHU Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, GH Pitié-Salpêtrière, Paris, France
| | - Jorge A Bevilacqua
- Programa de Anatomía y Biología del Desarrollo, ICBM, Facultad de Medicina, Departamento de Neurología y Neurocirugía, Hospital Clínico Universidad de Chile, Universidad de Chile, Santiago, Chile
| | - Marc Bitoun
- Research Center for Myology, UPMC Univ Paris 06 and INSERM UMRS 974, Institute of Myology, Paris, France
| | - Pablo Caviedes
- Programa de Farmacología Molecular y Clinica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
| | - Ana M Cárdenas
- Centro Interdisciplinario de Neurociencia de Valparaíso. Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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Moustaq L, Smaczynska-de Rooij II, Palmer SE, Marklew CJ, Ayscough KR. Insights into dynamin-associated disorders through analysis of equivalent mutations in the yeast dynamin Vps1. MICROBIAL CELL 2016; 3:147-158. [PMID: 28357347 PMCID: PMC5349089 DOI: 10.15698/mic2016.04.490] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The dynamins represent a superfamily of proteins that have been shown to function
in a wide range of membrane fusion and fission events. An increasing number of
mutations in the human classical dynamins, Dyn-1 and Dyn-2 has been reported,
with diseases caused by these changes ranging from Charcot-Marie-Tooth disorder
to epileptic encephalopathies. The budding yeast, Saccharomyces
cerevisiae expresses a single dynamin-related protein that
functions in membrane trafficking, and is considered to play a similar role to
Dyn-1 and Dyn-2 during scission of endocytic vesicles at the plasma membrane.
Large parts of the dynamin protein are highly conserved across species and this
has enabled us in this study to select a number of disease causing mutations and
to generate equivalent mutations in Vps1. We have then studied these mutants
using both cellular and biochemical assays to ascertain functions of the protein
that have been affected by the changes. Specifically, we demonstrate that the
Vps1-G397R mutation (Dyn-2 G358R) disrupts protein oligomerization, Vps1-A447T
(Dyn-1 A408T) affects the scission stage of endocytosis, while Vps1-R298L (Dyn-1
R256L) affects lipid binding specificity and possibly an early stage in
endocytosis. Overall, we consider that the yeast model will potentially provide
an avenue for rapid analysis of new dynamin mutations in order to understand the
underlying mechanisms that they disrupt
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Affiliation(s)
- Laila Moustaq
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | | | - Sarah E Palmer
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | | | - Kathryn R Ayscough
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
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12
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Demonbreun AR, Biersmith BH, McNally EM. Membrane fusion in muscle development and repair. Semin Cell Dev Biol 2015; 45:48-56. [PMID: 26537430 PMCID: PMC4679555 DOI: 10.1016/j.semcdb.2015.10.026] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 10/15/2015] [Indexed: 12/16/2022]
Abstract
Mature skeletal muscle forms from the fusion of skeletal muscle precursor cells, myoblasts. Myoblasts fuse to other myoblasts to generate multinucleate myotubes during myogenesis, and myoblasts also fuse to other myotubes during muscle growth and repair. Proteins within myoblasts and myotubes regulate complex processes such as elongation, migration, cell adherence, cytoskeletal reorganization, membrane coalescence, and ultimately fusion. Recent studies have identified cell surface proteins, intracellular proteins, and extracellular signaling molecules required for the proper fusion of muscle. Many proteins that actively participate in myoblast fusion also coordinate membrane repair. Here we will review mammalian membrane fusion with specific attention to proteins that mediate myoblast fusion and muscle repair.
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13
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Holler CJ, Davis PR, Beckett TL, Platt TL, Webb RL, Head E, Murphy MP. Bridging integrator 1 (BIN1) protein expression increases in the Alzheimer's disease brain and correlates with neurofibrillary tangle pathology. J Alzheimers Dis 2015; 42:1221-7. [PMID: 25024306 DOI: 10.3233/jad-132450] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Recent genome wide association studies have implicated bridging integrator 1 (BIN1) as a late-onset Alzheimer's disease (AD) susceptibility gene. There are at least 15 different known isoforms of BIN1, with many being expressed in the brain including the longest isoform (iso1), which is brain-specific and localizes to axon initial segments and nodes of Ranvier. It is currently unknown what role BIN1 plays in AD. We analyzed BIN1 protein expression from a large number (n = 71) of AD cases and controls from five different brain regions (hippocampus, inferior parietal cortex, inferior temporal cortex, frontal cortex (BA9), and superior and middle temporal gyri). We found that the amount of the largest isoform of BIN1 was significantly reduced in the AD brain compared to age-matched controls, and smaller BIN1 isoforms were significantly increased. Further, BIN1 was significantly correlated with the amount of neurofibrillary tangle (NFT) pathology but not with either diffuse or neuritic plaques, or with the amount of amyloid-β peptide. BIN1 is known to be abnormally expressed in another human disease, myotonic dystrophy, which also features prominent NFT pathology. These data suggest that BIN1 is likely involved in AD as a modulator of NFT pathology, and that this role may extend to other human diseases that feature tau pathology.
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Affiliation(s)
- Christopher J Holler
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Paulina R Davis
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA Department of Molecular and Biomedical Pharmacology, University of Kentucky, Lexington, KY, USA
| | - Tina L Beckett
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Thomas L Platt
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Robin L Webb
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Elizabeth Head
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA Department of Molecular and Biomedical Pharmacology, University of Kentucky, Lexington, KY, USA
| | - M Paul Murphy
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA University of Kentucky Center for Muscle Biology, University of Kentucky, Lexington, KY, USA
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14
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Chin YH, Lee A, Kan HW, Laiman J, Chuang MC, Hsieh ST, Liu YW. Dynamin-2 mutations associated with centronuclear myopathy are hypermorphic and lead to T-tubule fragmentation. Hum Mol Genet 2015. [PMID: 26199319 DOI: 10.1093/hmg/ddv285] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Skeletal muscle requires adequate membrane trafficking and remodeling to maintain its normal structure and functions. Consequently, many human myopathies are caused by mutations in membrane trafficking machinery. The large GTPase dynamin-2 (Dyn2) is best known for catalyzing membrane fission during clathrin-mediated endocytosis (CME), which is critical for cell signaling and survival. Despite its ubiquitous expression, mutations of Dyn2 are associated with two tissue-specific congenital disorders: centronuclear myopathy (CNM) and Charcot-Marie-Tooth (CMT) neuropathy. Several disease models for CNM-Dyn2 have been established to study its pathogenic mechanism; yet the cellular and biochemical effects of these mutations are still not fully understood. Here we comprehensively compared the biochemical activities of disease-associated Dyn2 mutations and found that CNM-Dyn2 mutants are hypermorphic with enhanced membrane fission activity, whereas CMT-Dyn2 is hypomorphic. More importantly, we found that the expression of CNM-Dyn2 mutants does not impair CME in myoblast, but leads to T-tubule fragmentation in both C2C12-derived myotubes and Drosophila body wall muscle. Our results demonstrate that CNM-Dyn2 mutants are gain-of-function mutations, and their primary effect in muscle is T-tubule disorganization, which explains the susceptibility of muscle to Dyn2 hyperactivity.
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Affiliation(s)
- Yu-Han Chin
- Institute of Molecular Medicine, College of Medicine
| | - Albert Lee
- Department of Chemistry, College of Science and
| | - Hung-Wei Kan
- Graduate Institute of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China
| | | | | | - Sung-Tsang Hsieh
- Graduate Institute of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China
| | - Ya-Wen Liu
- Institute of Molecular Medicine, College of Medicine,
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15
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Dohrn N, Le VQ, Petersen A, Skovbo P, Pedersen IS, Ernst A, Krarup H, Petersen MB. ECEL1 mutation causes fetal arthrogryposis multiplex congenita. Am J Med Genet A 2015; 167A:731-43. [PMID: 25708584 DOI: 10.1002/ajmg.a.37018] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 01/28/2015] [Indexed: 12/14/2022]
Abstract
Arthrogryposis multiplex congenita (AMC) is a descriptor for the clinical finding of congenital fixation of multiple joints. We present a consanguineous healthy couple with two pregnancies described with AMC due to characteristic findings on ultrasonography of fixated knee extension and reduced fetal movement at the gestational age of 13 weeks + 2 days and 12 weeks + 4 days. Both pregnancies were terminated and postmortem examinations were performed. The postmortem examinations confirmed AMC and suggested a diagnosis of centronuclear myopathy (CNM) due to characteristic histological findings in muscle biopsies. Whole exome sequencing (WES) was performed on all four individuals and the outcome was filtered by application of multiple filtration parameters satisfying a recessive inheritance pattern. Only one gene, ECEL1, was predicted damaging and had previously been associated with neuromuscular disease or AMC. The variant found ECEL1 is a missense mutation in a highly conserved residue and was predicted pathogenic by prediction software. The finding expands the molecular basis of congenital contractures and the phenotypic spectrum of ECEL1 mutations. The histological pattern suggestive of CNM in the fetuses can expand the spectrum of genes causing CNM, as we propose that mutations in ECEL1 can cause CNM or a condition similar to this. Further investigation of this is needed and we advocate that future patients with similar clinical presentation or proven ECEL1 mutations are examined with muscle biopsy. Secondly, this study illustrates the great potential of the clinical application of WES in couples with recurrent abortions or stillborn neonates.
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Affiliation(s)
- N Dohrn
- Department of Clinical Genetics, Aalborg University Hospital, Aalborg, Denmark
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16
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Abstract
Centronuclear myopathy is a lethal muscle disease. The most severe form of the disease, X-linked centronuclear myopathy, is due to mutations in the gene encoding myotubularin (MTM1), while mutations in dynamin 2 (DNM2) and amphiphysin 2/BIN1 (AMPH2) cause milder forms of myopathy. MTM1 is a lipid phosphatase, and mutations that disrupt this activity cause severe muscle wasting. In this issue of the JCI, Cowling and colleagues report on their finding of increased DNM2 levels in human and mouse muscle with MTM1 mutations. Partial reduction of Dnm2 in mice harboring Mtm1 mutations remarkably rescued muscle wasting and lethality, and this effect was muscle specific. DNM2 regulates membrane trafficking through vesicular scission, and it is presumed that reducing this activity accounts for improved outcome in X-linked centronuclear myopathy.
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17
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James NG, Digman MA, Ross JA, Barylko B, Wang L, Li J, Chen Y, Mueller JD, Gratton E, Albanesi JP, Jameson DM. A mutation associated with centronuclear myopathy enhances the size and stability of dynamin 2 complexes in cells. Biochim Biophys Acta Gen Subj 2013; 1840:315-21. [PMID: 24016602 DOI: 10.1016/j.bbagen.2013.09.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/31/2013] [Accepted: 09/03/2013] [Indexed: 12/17/2022]
Abstract
BACKGROUND Dynamin 2 (Dyn2) is a ~100kDa GTPase that assembles around the necks of nascent endocytic and Golgi vesicles and catalyzes membrane scission. Mutations in Dyn2 that cause centronuclear myopathy (CNM) have been shown to stabilize Dyn2 polymers against GTP-dependent disassembly in vitro. Precisely timed regulation of assembly and disassembly is believed to be critical for Dyn2 function in membrane vesiculation, and the CNM mutations interfere with this regulation by shifting the equilibrium toward the assembled state. METHODS In this study we use two fluorescence fluctuation spectroscopy (FFS) approaches to show that a CNM mutant form of Dyn2 also has a greater propensity to self-assemble in the cytosol and on the plasma membrane of living cells. RESULTS Results obtained using brightness analysis indicate that unassembled wild-type Dyn2 is predominantly tetrameric in the cytosol, although different oligomeric species are observed, depending on the concentration of expressed protein. In contrast, an R369W mutant identified in CNM patients forms higher-order oligomers at concentrations above 1μM. Investigation of Dyn2-R369W by Total Internal Reflection Fluorescence (TIRF) FFS reveals that this mutant forms larger and more stable clathrin-containing structures on the plasma membrane than wild-type Dyn2. CONCLUSIONS AND GENERAL SIGNIFICANCE These observations may explain defects in membrane trafficking reported in CNM patient cells and in heterologous systems expressing CNM-associated Dyn2 mutants.
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Affiliation(s)
- Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo Street, Biosciences 222, Honolulu, HI 96813, USA
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18
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Kierdaszuk B, Berdynski M, Karolczak J, Redowicz MJ, Zekanowski C, Kaminska AM. A novel mutation in the DNM2 gene impairs dynamin 2 localization in skeletal muscle of a patient with late onset centronuclear myopathy. Neuromuscul Disord 2013; 23:219-28. [PMID: 23374900 DOI: 10.1016/j.nmd.2012.12.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 10/23/2012] [Accepted: 12/13/2012] [Indexed: 10/27/2022]
Abstract
Centronuclear myopathies constitute a group of heterogeneous congenital myopathies characterized by the presence of abnormal, centrally located nuclei within muscle fibers. Centronuclear myopathies can be caused by mutations of several different genes, including DNM2, encoding dynamin 2 (DNM2) a large GTPase involved in membrane trafficking and endocytosis. We report a 52-year-old female with slowly progressive muscle weakness, and a family history of the disease. Clinical, morphological, biochemical and genetic analyses of the proband and her family members were performed, including analyses of the proband's muscle biopsy. A novel D614N mutation, located in the C-terminal region pleckstrin-homology (PH) domain of DNM2 was identified in the proband and four family members, who exhibited similar symptoms. The mutation was associated with profound changes in the localization of DNM2 in muscle fibers without significant changes in protein expression. Mutated DNM2 and proteins involved in the membrane trafficking or membrane compartments maintenance were dislocalized within the myofiber, and concentrated at centrally located nuclei. This novel causative mutation (D614N) within the DNM2 gene in a large Polish centronuclear myopathy family with a late age of overt clinical manifestation caused profound changes in DNM2 localization and impaired proper organization of myofibers, and skeletal muscle functioning.
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Affiliation(s)
- Biruta Kierdaszuk
- Department of Neurology, Medical University of Warsaw, 1a Banacha St., 02-097 Warsaw, Poland
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19
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Maurer M, Mary J, Guillaud L, Fender M, Pelé M, Bilzer T, Olby N, Penderis J, Shelton GD, Panthier JJ, Thibaud JL, Barthélémy I, Aubin-Houzelstein G, Blot S, Hitte C, Tiret L. Centronuclear myopathy in Labrador retrievers: a recent founder mutation in the PTPLA gene has rapidly disseminated worldwide. PLoS One 2012; 7:e46408. [PMID: 23071563 PMCID: PMC3465307 DOI: 10.1371/journal.pone.0046408] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 08/29/2012] [Indexed: 12/11/2022] Open
Abstract
Centronuclear myopathies (CNM) are inherited congenital disorders characterized by an excessive number of internalized nuclei. In humans, CNM results from ∼70 mutations in three major genes from the myotubularin, dynamin and amphiphysin families. Analysis of animal models with altered expression of these genes revealed common defects in all forms of CNM, paving the way for unified pathogenic and therapeutic mechanisms. Despite these efforts, some CNM cases remain genetically unresolved. We previously identified an autosomal recessive form of CNM in French Labrador retrievers from an experimental pedigree, and showed that a loss-of-function mutation in the protein tyrosine phosphatase-like A (PTPLA) gene segregated with CNM. Around the world, client-owned Labrador retrievers with a similar clinical presentation and histopathological changes in muscle biopsies have been described. We hypothesized that these Labradors share the same PTPLAcnm mutation. Genotyping of an international panel of 7,426 Labradors led to the identification of PTPLAcnm carriers in 13 countries. Haplotype analysis demonstrated that the PTPLAcnm allele resulted from a single and recent mutational event that may have rapidly disseminated through the extensive use of popular sires. PTPLA-deficient Labradors will help define the integrated role of PTPLA in the existing CNM gene network. They will be valuable complementary large animal models to test innovative therapies in CNM.
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Affiliation(s)
- Marie Maurer
- CNM Project, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- UMR955 de Génétique Fonctionnelle et Médicale, Institut National de la Recherche Agronomique, Maisons-Alfort, France
| | - Jérôme Mary
- CNM Project, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- UMR955 de Génétique Fonctionnelle et Médicale, Institut National de la Recherche Agronomique, Maisons-Alfort, France
- Antagene, La Tour de Salvagny, France
| | - Laurent Guillaud
- CNM Project, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- UMR955 de Génétique Fonctionnelle et Médicale, Institut National de la Recherche Agronomique, Maisons-Alfort, France
| | - Marilyn Fender
- CNM Project, Pickett, Wisconsin, United States of America
| | - Manuel Pelé
- CNM Project, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- UMR955 de Génétique Fonctionnelle et Médicale, Institut National de la Recherche Agronomique, Maisons-Alfort, France
| | - Thomas Bilzer
- Institut für Neuropathologie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | - Natasha Olby
- College of Veterinary Medicine, Neurology Faculty, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Jacques Penderis
- College of Medical, Veterinary and Life Science, School of Veterinary Medicine, University of Glasgow, Glasgow, United Kingdom
| | - G. Diane Shelton
- Department of Pathology, University of California San Diego, La Jolla, California, United States of America
| | - Jean-Jacques Panthier
- CNM Project, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- UMR955 de Génétique Fonctionnelle et Médicale, Institut National de la Recherche Agronomique, Maisons-Alfort, France
- Mouse Functional Genetics URA2578, Centre National de la Recherche Scientifique, Institut Pasteur, Paris, France
| | - Jean-Laurent Thibaud
- Unité Propre de Recherche de Neurobiologie, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
| | - Inès Barthélémy
- Unité Propre de Recherche de Neurobiologie, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
| | - Geneviève Aubin-Houzelstein
- CNM Project, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- UMR955 de Génétique Fonctionnelle et Médicale, Institut National de la Recherche Agronomique, Maisons-Alfort, France
| | - Stéphane Blot
- Unité Propre de Recherche de Neurobiologie, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
| | - Christophe Hitte
- UMR6290, Centre National de la Recherche Scientifique, Institut de Génétique et Développement de Rennes, Université de Rennes1, Rennes, France
| | - Laurent Tiret
- CNM Project, Université Paris-Est Créteil, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- UMR955 de Génétique Fonctionnelle et Médicale, Institut National de la Recherche Agronomique, Maisons-Alfort, France
- * E-mail:
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20
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Schellenberg GD, Montine TJ. The genetics and neuropathology of Alzheimer's disease. Acta Neuropathol 2012; 124:305-23. [PMID: 22618995 DOI: 10.1007/s00401-012-0996-2] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 05/07/2012] [Accepted: 05/08/2012] [Indexed: 02/07/2023]
Abstract
Here we review the genetic causes and risks for Alzheimer's disease (AD). Early work identified mutations in three genes that cause AD: APP, PSEN1 and PSEN2. Although mutations in these genes are rare causes of AD, their discovery had a major impact on our understanding of molecular mechanisms of AD. Early work also revealed the ε4 allele of the APOE as a strong risk factor for AD. Subsequently, SORL1 also was identified as an AD risk gene. More recently, advances in our knowledge of the human genome, made possible by technological advances and methods to analyze genomic data, permit systematic identification of genes that contribute to AD risk. This work, so far accomplished through single nucleotide polymorphism arrays, has revealed nine new genes implicated in AD risk (ABCA7, BIN1, CD33, CD2AP, CLU, CR1, EPHA1, MS4A4E/MS4A6A, and PICALM). We review the relationship between these mutations and genetic variants and the neuropathologic features of AD and related disorders. Together, these discoveries point toward a new era in neurodegenerative disease research that impacts not only AD but also related illnesses that produce cognitive and behavioral deficits.
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Affiliation(s)
- Gerard D Schellenberg
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6100, USA.
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21
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Sakowski SA, Lunn JS, Busta AS, Oh SS, Zamora-Berridi G, Palmer M, Rosenberg AA, Philip SG, Dowling JJ, Feldman EL. Neuromuscular effects of G93A-SOD1 expression in zebrafish. Mol Neurodegener 2012; 7:44. [PMID: 22938571 PMCID: PMC3506515 DOI: 10.1186/1750-1326-7-44] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 08/26/2012] [Indexed: 12/11/2022] Open
Abstract
Background Amyotrophic lateral sclerosis (ALS) is a fatal disorder involving the degeneration and loss of motor neurons. The mechanisms of motor neuron loss in ALS are unknown and there are no effective treatments. Defects in the distal axon and at the neuromuscular junction are early events in the disease course, and zebrafish provide a promising in vivo system to examine cellular mechanisms and treatments for these events in ALS pathogenesis. Results We demonstrate that transient genetic manipulation of zebrafish to express G93A-SOD1, a mutation associated with familial ALS, results in early defects in motor neuron outgrowth and axonal branching. This is consistent with previous reports on motor neuron axonal defects associated with familial ALS genes following knockdown or mutant protein overexpression. We also demonstrate that upregulation of growth factor signaling is capable of rescuing these early defects, validating the potential of the model for therapeutic discovery. We generated stable transgenic zebrafish lines expressing G93A-SOD1 to further characterize the consequences of G93A-SOD1 expression on neuromuscular pathology and disease progression. Behavioral monitoring reveals evidence of motor dysfunction and decreased activity in transgenic ALS zebrafish. Examination of neuromuscular and neuronal pathology throughout the disease course reveals a loss of neuromuscular junctions and alterations in motor neuron innervations patterns with disease progression. Finally, motor neuron cell loss is evident later in the disease. Conclusions This sequence of events reflects the stepwise mechanisms of degeneration in ALS, and provides a novel model for mechanistic discovery and therapeutic development for neuromuscular degeneration in ALS.
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Affiliation(s)
- Stacey A Sakowski
- Department of Neurology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor 5017 AAT-BSRBMI, USA
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Dowling JJ, Joubert R, Low SE, Durban AN, Messaddeq N, Li X, Dulin-Smith AN, Snyder AD, Marshall ML, Marshall JT, Beggs AH, Buj-Bello A, Pierson CR. Myotubular myopathy and the neuromuscular junction: a novel therapeutic approach from mouse models. Dis Model Mech 2012; 5:852-9. [PMID: 22645112 PMCID: PMC3484867 DOI: 10.1242/dmm.009746] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Myotubular myopathy (MTM) is a severe congenital muscle disease characterized by profound weakness, early respiratory failure and premature lethality. MTM is defined by muscle biopsy findings that include centralized nuclei and disorganization of perinuclear organelles. No treatments currently exist for MTM. We hypothesized that aberrant neuromuscular junction (NMJ) transmission is an important and potentially treatable aspect of the disease pathogenesis. We tested this hypothesis in two murine models of MTM. In both models we uncovered evidence of a disorder of NMJ transmission: fatigable weakness, improved strength with neostigmine, and electrodecrement with repetitive nerve stimulation. Histopathological analysis revealed abnormalities in the organization, appearance and size of individual NMJs, abnormalities that correlated with changes in acetylcholine receptor gene expression and subcellular localization. We additionally determined the ability of pyridostigmine, an acetylcholinesterase inhibitor, to ameliorate aspects of the behavioral phenotype related to NMJ dysfunction. Pyridostigmine treatment resulted in significant improvement in fatigable weakness and treadmill endurance. In all, these results describe a newly identified pathological abnormality in MTM, and uncover a potential disease-modifying therapy for this devastating disorder.
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Affiliation(s)
- James J Dowling
- Department of Pediatrics, Taubman Medical Research Institute, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA.
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Oh E, Robinson I. Barfly: sculpting membranes at the Drosophila neuromuscular junction. Dev Neurobiol 2012; 72:33-56. [PMID: 21630471 DOI: 10.1002/dneu.20923] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The ability of a cell to change the shape of its membranes is intrinsic to many cellular functions. Proteins that can alter or recognize curved membrane structures and those that can act to recruit other proteins which stabilize the membrane curvature are likely to be essential in cell functions. The BAR (Bin, amphiphysin, RVS167 homology) domain is a protein domain that can either induce lipidic membranes to curve or can sense curved membranes. BAR domains are found in several proteins at neuronal synapses. We will review BAR domain structure and the role that BAR domain containing proteins play in regulating the morphology and function of the Drosophila neuromuscular junction. In flies the BAR domain containing proteins, endophilin and syndapin affect synaptic vesicle endocytosis, whereas CIP4, dRich, nervous wreck and syndapin affect synaptic morphology. We will review the growing evidence implicating mutations in BAR domain containing proteins being the cause of human pathologies.
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Affiliation(s)
- Eugene Oh
- Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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25
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Liu YW, Lukiyanchuk V, Schmid SL. Common membrane trafficking defects of disease-associated dynamin 2 mutations. Traffic 2011; 12:1620-33. [PMID: 21762456 DOI: 10.1111/j.1600-0854.2011.01250.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Dynamin (Dyn) is a multidomain and multifunctional GTPase best known for its essential role in clathrin-mediated endocytosis (CME). Dyn2 mutations have been linked to two human diseases, centronuclear myopathy (CNM) and Charcot-Marie-Tooth (CMT) disease. Paradoxically, although Dyn2 is ubiquitously expressed and essential for embryonic development, the disease-associated Dyn2 mutants are autosomal dominant, but result in slowly progressing and tissue-specific diseases. Thus, although the cellular defects that cause disease remain unclear, they are expected to be mild. To gain new insight into potential pathogenic mechanisms, we utilized mouse Dyn2 conditional knockout cells combined with retroviral-mediated reconstitution to mimic both heterozygous and homozygous states and characterized cellular phenotypes using quantitative assays for several membrane trafficking events. Surprisingly, none of the four mutants studied exhibited a defect in CME, but all were impaired in their ability to support p75/neurotrophin receptor export from the Golgi, the raft-dependent endocytosis of cholera toxin and the clathrin-independent endocytosis of epidermal growth factor receptor (EGFR). While it will be important to study these mutants in disease-relevant muscle and neuronal cells, given the importance of neurotrophic factors and lipid rafts in muscle physiology, we speculate that these common cellular defects might contribute to the tissue-specific diseases caused by a ubiquitously expressed protein.
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Affiliation(s)
- Ya-Wen Liu
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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26
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Liewluck T, Lovell TL, Bite AV, Engel AG. Sporadic centronuclear myopathy with muscle pseudohypertrophy, neutropenia, and necklace fibers due to a DNM2 mutation. Neuromuscul Disord 2011; 20:801-4. [PMID: 20817456 DOI: 10.1016/j.nmd.2010.07.273] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 05/24/2010] [Accepted: 07/20/2010] [Indexed: 10/19/2022]
Abstract
Dynamin 2 gene (DNM2) mutations result in an autosomal dominant centronuclear myopathy (CNM) and a Charcot-Marie-Tooth (CMT) neuropathy. DNM2-CMT but not DNM2-CNM patients were noted to have neutropenia. We here report a man with paravertebral muscles hypertrophy and mild neutropenia. His muscle biopsy was typical for CNM with additional "necklace" fibers. Sequencing of DNM2 revealed a known heterozygous c.1269C>T (p.Arg369Trp) mutation. Necklace fibers were considered as a pathological hallmark of late onset X-linked CNM due to mutations in MTM1 but have not been observed in DNM2-CNM. The findings broaden the features of DNM2-myopathy.
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Affiliation(s)
- Teerin Liewluck
- Department of Neurology and Muscle Research Laboratory, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
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27
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Kenniston JA, Lemmon MA. Dynamin GTPase regulation is altered by PH domain mutations found in centronuclear myopathy patients. EMBO J 2010; 29:3054-67. [PMID: 20700106 PMCID: PMC2944063 DOI: 10.1038/emboj.2010.187] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 07/14/2010] [Indexed: 01/18/2023] Open
Abstract
The large GTPase dynamin has an important membrane scission function in receptor-mediated endocytosis and other cellular processes. Self-assembly on phosphoinositide-containing membranes stimulates dynamin GTPase activity, which is crucial for its function. Although the pleckstrin-homology (PH) domain is known to mediate phosphoinositide binding by dynamin, it remains unclear how this promotes activation. Here, we describe studies of dynamin PH domain mutations found in centronuclear myopathy (CNM) that increase dynamin's GTPase activity without altering phosphoinositide binding. CNM mutations in the PH domain C-terminal α-helix appear to cause conformational changes in dynamin that alter control of the GTP hydrolysis cycle. These mutations either 'sensitize' dynamin to lipid stimulation or elevate basal GTPase rates by promoting self-assembly and thus rendering dynamin no longer lipid responsive. We also describe a low-resolution structure of dimeric dynamin from small-angle X-ray scattering that reveals conformational changes induced by CNM mutations, and defines requirements for domain rearrangement upon dynamin self-assembly at membrane surfaces. Our data suggest that changes in the PH domain may couple lipid binding to dynamin GTPase activation at sites of vesicle invagination.
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Affiliation(s)
- Jon A Kenniston
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - Mark A Lemmon
- Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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28
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Tajika Y, Takahashi M, Hino M, Murakami T, Yorifuji H. VAMP2 marks quiescent satellite cells and myotubes, but not activated myoblasts. Acta Histochem Cytochem 2010; 43:107-14. [PMID: 20824121 PMCID: PMC2930059 DOI: 10.1267/ahc.10010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Accepted: 06/29/2010] [Indexed: 01/25/2023] Open
Abstract
We examined the expression and intracellular localization of vesicle-associated membrane protein 2 (VAMP2) during the differentiation of skeletal muscle cells by immunofluorescence microscopy. In isolated single myofibers, VAMP2 was expressed in quiescent satellite cells, downregulated in proliferating myoblastic cells, and re-expressed with differentiation. In the myoblastic cell line C2C12, VAMP2 was expressed at a low level in the proliferating stage, and then increased after differentiation into myotubes. Based on these results, we propose that VAMP2 can be used as a molecular marker for both quiescent satellite cells and myotubes, but not for proliferating myoblasts. We also found the partial colocalization of VAMP2 with transferrin- or Rab11-labeled vesicles in myotubes, suggesting a role of VAMP2 in the trafficking of recycling endosomes.
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Affiliation(s)
- Yuki Tajika
- Department of Anatomy, Gunma University Graduate School of Medicine
| | - Maiko Takahashi
- Department of Anatomy, Gunma University Graduate School of Medicine
| | - Mizuki Hino
- Department of Anatomy, Gunma University Graduate School of Medicine
| | - Tohru Murakami
- Department of Anatomy, Gunma University Graduate School of Medicine
| | - Hiroshi Yorifuji
- Department of Anatomy, Gunma University Graduate School of Medicine
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29
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Parker S, Baylis HA. Overexpression of caveolins in Caenorhabditis elegans induces changes in egg-laying and fecundity. Commun Integr Biol 2010; 2:382-4. [PMID: 19907693 DOI: 10.4161/cib.2.5.8715] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 04/07/2009] [Indexed: 02/06/2023] Open
Abstract
Caveolae are small plasma membrane-associated invaginations that are enriched in proteins of the caveolin family in addition to, sphingolipids, glycosphingolipids and cholesterol. Caveolae have been implicated in several endocytic and trafficking mechanisms. Mutations in caveolins have been shown to cause disease and caveolae offer one site for pathogen entry. The Caenorhabditis elegans genome encodes two caveolins (cav-1 and cav-2); we have shown that these two proteins have distinct expression patterns. CAV-1 is found in the majority of cells in embryos and in the body-wall muscles, neurons and germ line of adult worms. CAV-2 is expressed in the intestine and is required for apical lipid trafficking. In the course of our studies, we generated several constructs to overexpress caveolins in C. elegans. Here we show that overexpression of cav-1 protects against the decrease in brood size associated with the effects of heat shock and the presence of extrachromosomal arrays in heat-shocked animals. Furthermore, we show that overexpression of cav-2 in the nervous system increases the rate of egg-laying and total number of eggs laid.
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Affiliation(s)
- Scott Parker
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK.
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Matsumoto H, Sasazaki S, Fujiwara A, Ichihara N, Kikuchi T, Mannen H. Accumulation of caveolin-3 protein is limited in damaged muscle in chicken muscular dystrophy. Comp Biochem Physiol A Mol Integr Physiol 2010; 157:68-72. [PMID: 20451648 DOI: 10.1016/j.cbpa.2010.04.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 04/28/2010] [Accepted: 04/29/2010] [Indexed: 01/08/2023]
Abstract
Members of the caveolin family are the main component of caveolae, and caveolin-3 is a muscle-specific protein. Caveolin-3 deficiency induces a muscular dystrophic phenotype, while its overexpression is also harmful to muscle cells. Increased caveolae were observed in chicken muscular dystrophy; however, the underlying mechanism causing the onset remains unclear. Therefore, the current study analyzes the expression of caveolin-3 and other caveola-related proteins in dystrophic chickens. Western blotting and semi-quantitative RT-PCR analysis revealed that (1) caveolin-3 is highly expressed in the damaged muscle of dystrophic chickens (7.12-fold); (2) the amount of caveolin-3 protein is regulated in posttranslational modification, since no significant increase is observed at the mRNA level (1.09-fold); and (3) the expression pattern of other caveola-related proteins is similar to that of caveolin-3. These results suggest that the accumulation of caveolin-3 protein may be associated with the causative process of chicken muscular dystrophy.
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Affiliation(s)
- Hirokazu Matsumoto
- Laboratory of Animal Breeding and Genetics, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
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Dowling JJ, Low SE, Busta AS, Feldman EL. Zebrafish MTMR14 is required for excitation-contraction coupling, developmental motor function and the regulation of autophagy. Hum Mol Genet 2010; 19:2668-81. [PMID: 20400459 DOI: 10.1093/hmg/ddq153] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Myotubularins are a family of dual-specificity phosphatases that act to modify phosphoinositides and regulate membrane traffic. Mutations in several myotubularins are associated with human disease. Sequence changes in MTM1 and MTMR14 (also known as Jumpy) have been detected in patients with a severe skeletal myopathy called centronuclear myopathy. MTM1 has been characterized in vitro and in several model systems, while the function of MTMR14 and its specific role in muscle development and disease is much less well understood. We have previously reported that knockdown of zebrafish MTM1 results in significantly impaired motor function and severe histopathologic changes in skeletal muscle that are characteristic of human centronuclear myopathy. In the current study, we examine zebrafish MTMR14 using gene dosage manipulation. As with MTM1 knockdown, morpholino-mediated knockdown of MTMR14 results in morphologic abnormalities, a developmental motor phenotype characterized by diminished spontaneous contractions and abnormal escape response, and impaired excitation-contraction coupling. In contrast to MTM1 knockdown, however, muscle ultrastructure is unaffected. Double knockdown of both MTM1 and MTMR14 significantly impairs motor function and alters skeletal muscle ultrastructure. The combined effect of reducing levels of both MTMR14 and MTM1 is significantly more severe than either knockdown alone, an effect which is likely mediated, at least in part, by increased autophagy. In all, our results suggest that MTMR14 is required for motor function and, in combination with MTM1, is required for myocyte homeostasis and normal embryonic development.
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Affiliation(s)
- J J Dowling
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA.
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Jovic M, Sharma M, Rahajeng J, Caplan S. The early endosome: a busy sorting station for proteins at the crossroads. Histol Histopathol 2010; 25:99-112. [PMID: 19924646 DOI: 10.14670/hh-25.99] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Endocytosis marks the entry of internalized receptors into the complex network of endocytic trafficking pathways. Endocytic vesicles are rapidly targeted to a distinct membrane-bound endocytic organelle referred to as the early endosome. Despite the existence of numerous internalization routes, early endosomes (EE) serve as a focal point of the endocytic pathway. Sorting events initiated at this compartment determine the subsequent fate of internalized proteins and lipids, destining them either for recycling to the plasma membrane, degradation in lysosomes or delivery to the trans-Golgi network. Sorting of endocytic cargo to the latter compartments is accomplished through the formation of distinct microdomains within early endosomes, through the coordinate recruitment and assembly of the sorting machinery. An elaborate network of interactions between endocytic regulatory proteins ensures synchronized sorting of cargo to microdomains followed by morphological changes at the early endosomal membranes. Consequently, the cargo targeted either for recycling back to the plasma membrane, or for retrograde transport to the trans-Golgi network, localizes to newly-formed tubular membranes. With a high ratio of membrane surface to lumenal volume, these tubules effectively concentrate the recycling cargo, ensuring efficient transport out of the EE. Conversely, receptors sorted for degradation cluster at the flat clathrin lattices involved in invaginations of the limiting membrane, associating with newly formed intralumenal vesicles. In this review we will discuss the characteristics of early endosomes, their role in the regulation of endocytic transport, and their aberrant function in a variety of diseases.
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Affiliation(s)
- Marko Jovic
- Department of Biochemistry and Molecular Biology and Eppley Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5870, USA
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Dowling JJ, Vreede AP, Low SE, Gibbs EM, Kuwada JY, Bonnemann CG, Feldman EL. Loss of myotubularin function results in T-tubule disorganization in zebrafish and human myotubular myopathy. PLoS Genet 2009; 5:e1000372. [PMID: 19197364 PMCID: PMC2631153 DOI: 10.1371/journal.pgen.1000372] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Accepted: 01/07/2009] [Indexed: 11/26/2022] Open
Abstract
Myotubularin is a lipid phosphatase implicated in endosomal trafficking in vitro, but with an unknown function in vivo. Mutations in myotubularin cause myotubular myopathy, a devastating congenital myopathy with unclear pathogenesis and no current therapies. Myotubular myopathy was the first described of a growing list of conditions caused by mutations in proteins implicated in membrane trafficking. To advance the understanding of myotubularin function and disease pathogenesis, we have created a zebrafish model of myotubular myopathy using morpholino antisense technology. Zebrafish with reduced levels of myotubularin have significantly impaired motor function and obvious histopathologic changes in their muscle. These changes include abnormally shaped and positioned nuclei and myofiber hypotrophy. These findings are consistent with those observed in the human disease. We demonstrate for the first time that myotubularin functions to regulate PI3P levels in a vertebrate in vivo, and that homologous myotubularin-related proteins can functionally compensate for the loss of myotubularin. Finally, we identify abnormalities in the tubulo-reticular network in muscle from myotubularin zebrafish morphants and correlate these changes with abnormalities in T-tubule organization in biopsies from patients with myotubular myopathy. In all, we have generated a new model of myotubular myopathy and employed this model to uncover a novel function for myotubularin and a new pathomechanism for the human disease that may explain the weakness associated with the condition (defective excitation–contraction coupling). In addition, our findings of tubuloreticular abnormalities and defective excitation-contraction coupling mechanistically link myotubular myopathy with several other inherited muscle diseases, most notably those due to ryanodine receptor mutations. Based on our findings, we speculate that congenital myopathies, usually considered entities with similar clinical features but very disparate pathomechanisms, may at their root be disorders of calcium homeostasis. Congenital myopathies are inherited muscle conditions typically presenting in early childhood. They are individually rare, but as a group are likely as common as conditions such as muscular dystrophy. The zebrafish is an emerging experimental system for the study of myopathies. We have utilized the zebrafish to develop a model of myotubular myopathy, one of the most severe childhood muscle diseases and a condition whose pathogenesis is poorly understood. We have generated fish that have the characteristic behavioral and histological features of human myotubular myopathy. Using this model, we then made novel insights into the pathogenesis of myotubular myopathy, including the identification of abnormalities in the muscle tubulo-reticular system. We subsequently identified similar changes in muscle from patients with myotubular myopathy, corroborating the importance of our zebrafish findings. Because a functional tubulo-reticular complex is required for normal muscle contraction, we speculate that the weakness observed in myotubular myopathy is caused by breakdown of this network. In all, our study is the first to identify a potential pathomechanism to explain the clinical features of myotubular myopathy. Furthermore, by revealing abnormalities in the tubulo-reticular system, we provide a novel link between myotubular myopathy and several other congenital myopathies.
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MESH Headings
- Animals
- Disease Models, Animal
- Embryo, Nonmammalian/metabolism
- Fluorescent Antibody Technique
- Homeostasis
- Humans
- Muscle Fibers, Skeletal/pathology
- Muscle Fibers, Skeletal/ultrastructure
- Muscle, Skeletal/metabolism
- Mutation
- Myopathies, Structural, Congenital/etiology
- Myopathies, Structural, Congenital/metabolism
- Myopathies, Structural, Congenital/pathology
- Protein Tyrosine Phosphatases, Non-Receptor/genetics
- Protein Tyrosine Phosphatases, Non-Receptor/physiology
- Zebrafish/genetics
- Zebrafish/metabolism
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Affiliation(s)
- James J Dowling
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, Michigan, USA.
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