1
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Koshorek J, de Macena Sobreira N, Saidha S. LAMA2-related muscular dystrophy mimicking multiple sclerosis. BMJ Case Rep 2022; 15:e249061. [PMID: 35868801 PMCID: PMC9316028 DOI: 10.1136/bcr-2022-249061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Laminin-alpha2-related muscular dystrophy (LAMA2-MD) is a genetic condition due to reduced LAMA2, a protein found throughout the nervous system. Late-onset LAMA2-MD may present with proximal muscle weakness, joint contractures, neuropathy, epilepsy and/or cardiorespiratory issues, and is less common than the neonatal form. We describe a novel phenotype of LAMA2-MD with progressive myelopathy and spinal cord abnormalities.A woman was referred for evaluation of multiple sclerosis (MS) with progressive gait difficulty and abnormal neuroimaging showing white matter abnormalities in the brain and spinal cord. Ancillary testing was not consistent with primary neuroinflammatory disorders, systemic autoimmunity or infection. Metabolic workup revealed low cyanocobalamin. Genetic testing identified two LAMA2-MD variants.Genetic disorders can mimic treatable neurological conditions. Chronic progressive course, involvement of the peripheral and central nervous systems, and confluent white matter abnormalities should be investigated with molecular testing that includes LAMA2 sequencing to ensure proper diagnosis and management.
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Affiliation(s)
- Jacqueline Koshorek
- Neuroimmunology and Neurological Infections, Johns Hopkins University, Baltimore, Maryland, USA
| | - Nara de Macena Sobreira
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Shiv Saidha
- Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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2
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Fabian L, Dowling JJ. Zebrafish Models of LAMA2-Related Congenital Muscular Dystrophy (MDC1A). Front Mol Neurosci 2020; 13:122. [PMID: 32742259 PMCID: PMC7364686 DOI: 10.3389/fnmol.2020.00122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 06/11/2020] [Indexed: 01/28/2023] Open
Abstract
LAMA2-related congenital muscular dystrophy (CMD; LAMA2-MD), also referred to as merosin deficient CMD (MDC1A), is a severe neonatal onset muscle disease caused by recessive mutations in the LAMA2 gene. LAMA2 encodes laminin α2, a subunit of the extracellular matrix (ECM) oligomer laminin 211. There are currently no treatments for MDC1A, and there is an incomplete understanding of disease pathogenesis. Zebrafish, due to their high degree of genetic conservation with humans, large clutch sizes, rapid development, and optical clarity, have emerged as an excellent model system for studying rare Mendelian diseases. They are particularly suitable as a model for muscular dystrophy because they contain at least one orthologue to all major human MD genes, have muscle that is similar to human muscle in structure and function, and manifest obvious and easily measured MD related phenotypes. In this review article, we present the existing zebrafish models of MDC1A, and discuss their contribution to the understanding of MDC1A pathomechanisms and therapy development.
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Affiliation(s)
- Lacramioara Fabian
- Program for Genetics and Genome Biology, Hospital for Sick Children, Toronto, ON, Canada
| | - James J Dowling
- Program for Genetics and Genome Biology, Hospital for Sick Children, Toronto, ON, Canada.,Division of Neurology, Hospital for Sick Children, Toronto, ON, Canada.,Departments of Pediatrics and Molecular Genetics, University of Toronto, Toronto, ON, Canada
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3
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Wood AJ, Cohen N, Joshi V, Li M, Costin A, Hersey L, McKaige EA, Manneken JD, Sonntag C, Miles LB, Siegel A, Currie PD. RGD inhibition of itgb1 ameliorates laminin-α2-deficient zebrafish fibre pathology. Hum Mol Genet 2020; 28:1403-1413. [PMID: 30566586 DOI: 10.1093/hmg/ddy426] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 11/15/2018] [Accepted: 11/22/2018] [Indexed: 01/27/2023] Open
Abstract
Deficiency of muscle basement membrane (MBM) component laminin-α2 leads to muscular dystrophy congenital type 1A (MDC1A), a currently untreatable myopathy. Laminin--α2 has two main binding partners within the MBM, dystroglycan and integrin. Integrins coordinate both cell adhesion and signalling; however, there is little mechanistic insight into integrin's function at the MBM. In order to study integrin's role in basement membrane development and how this relates to the MBM's capacity to handle force, an itgβ1.b-/- zebrafish line was created. Histological examination revealed increased extracellular matrix (ECM) deposition at the MBM in the itgβ1.b-/- fish when compared with controls. Surprisingly, both laminin and collagen proteins were found to be increased in expression at the MBM of the itgβ1.b-/- larvae when compared with controls. This increase in ECM components resulted in a decrease in myotomal elasticity as determined by novel passive force analyses. To determine if it was possible to control ECM deposition at the MBM by manipulating integrin activity, RGD peptide, a potent inhibitor of integrin-β1, was injected into a zebrafish model of MDC1A. As postulated an increase in laminin and collagen was observed in the lama2-/- mutant MBM. Importantly, there was also an improvement in fibre stability at the MBM, judged by a reduction in fibre pathology. These results therefore show that blocking ITGβ1 signalling increases ECM deposition at the MBM, a process that could be potentially exploited for treatment of MDC1A.
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Affiliation(s)
- Alasdair J Wood
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Naomi Cohen
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Veronica Joshi
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Mei Li
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Adam Costin
- Ramaciotti Centre for Electron Microscopy, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Lucy Hersey
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Emily A McKaige
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Jessica D Manneken
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Carmen Sonntag
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Lee B Miles
- Department of Physiology, Anatomy and Microbiology, Latrobe University, Melbourne (Bundoora), VIC, Australia
| | - Ashley Siegel
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia
| | - Peter D Currie
- Australian Regenerative Medicine Institute, Monash University, Innovation Walk, Clayton Campus, Wellington Road, Clayton, VIC, Australia.,Victorian Node, EMBL Australia, Clayton, VIC, Australia
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4
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Oliveira J, Gruber A, Cardoso M, Taipa R, Fineza I, Gonçalves A, Laner A, Winder TL, Schroeder J, Rath J, Oliveira ME, Vieira E, Sousa AP, Vieira JP, Lourenço T, Almendra L, Negrão L, Santos M, Melo-Pires M, Coelho T, den Dunnen JT, Santos R, Sousa M. LAMA2 gene mutation update: Toward a more comprehensive picture of the laminin-α2 variome and its related phenotypes. Hum Mutat 2018; 39:1314-1337. [PMID: 30055037 DOI: 10.1002/humu.23599] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Revised: 07/05/2018] [Accepted: 07/25/2018] [Indexed: 12/15/2022]
Abstract
Congenital muscular dystrophy type 1A (MDC1A) is one of the main subtypes of early-onset muscle disease, caused by disease-associated variants in the laminin-α2 (LAMA2) gene. MDC1A usually presents as a severe neonatal hypotonia and failure to thrive. Muscle weakness compromises normal motor development, leading to the inability to sit unsupported or to walk independently. The phenotype associated with LAMA2 defects has been expanded to include milder and atypical cases, being now collectively known as LAMA2-related muscular dystrophies (LAMA2-MD). Through an international multicenter collaborative effort, 61 new LAMA2 disease-associated variants were identified in 86 patients, representing the largest number of patients and new disease-causing variants in a single report. The collaborative variant collection was supported by the LOVD-powered LAMA2 gene variant database (https://www.LOVD.nl/LAMA2), updated as part of this work. As of December 2017, the database contains 486 unique LAMA2 variants (309 disease-associated), obtained from direct submissions and literature reports. Database content was systematically reviewed and further insights concerning LAMA2-MD are presented. We focus on the impact of missense changes, especially the c.2461A > C (p.Thr821Pro) variant and its association with late-onset LAMA2-MD. Finally, we report diagnostically challenging cases, highlighting the relevance of modern genetic analysis in the characterization of clinically heterogeneous muscle diseases.
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Affiliation(s)
- Jorge Oliveira
- Unidade de Genética Molecular, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar do Porto, Porto, Portugal.,Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
| | | | - Márcio Cardoso
- Consulta de Doenças Neuromusculares e Serviço de Neurofisiologia, Departamento de Neurociências, Centro Hospitalar do Porto, Porto, Portugal
| | - Ricardo Taipa
- Unidade de Neuropatologia, Centro Hospitalar do Porto, Porto, Portugal
| | - Isabel Fineza
- Unidade de Neuropediatria, Centro de Desenvolvimento da Criança Luís Borges, Hospital Pediátrico de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal
| | - Ana Gonçalves
- Unidade de Genética Molecular, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar do Porto, Porto, Portugal.,Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
| | | | | | | | - Julie Rath
- PreventionGenetics, Marshfield, Wisconsin
| | - Márcia E Oliveira
- Unidade de Genética Molecular, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar do Porto, Porto, Portugal.,Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
| | - Emília Vieira
- Unidade de Genética Molecular, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar do Porto, Porto, Portugal.,Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal
| | - Ana Paula Sousa
- Consulta de Doenças Neuromusculares e Serviço de Neurofisiologia, Departamento de Neurociências, Centro Hospitalar do Porto, Porto, Portugal
| | - José Pedro Vieira
- Serviço de Neurologia, Hospital de Dona Estefânia, Centro Hospitalar de Lisboa Central, Lisboa, Portugal
| | - Teresa Lourenço
- Serviço de Genética Médica, Hospital de Dona Estefânia, Centro Hospitalar de Lisboa Central, Lisboa, Portugal
| | - Luciano Almendra
- Consulta de Doenças Neuromusculares, Hospitais da Universidade de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal
| | - Luís Negrão
- Consulta de Doenças Neuromusculares, Hospitais da Universidade de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal
| | - Manuela Santos
- Consulta de Doenças Neuromusculares e Serviço de Neuropediatria, Centro Hospitalar do Porto, Porto, Portugal
| | - Manuel Melo-Pires
- Unidade de Neuropatologia, Centro Hospitalar do Porto, Porto, Portugal
| | - Teresa Coelho
- Consulta de Doenças Neuromusculares e Serviço de Neurofisiologia, Departamento de Neurociências, Centro Hospitalar do Porto, Porto, Portugal
| | - Johan T den Dunnen
- Departments of Human Genetics and Clinical Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | - Rosário Santos
- Unidade de Genética Molecular, Centro de Genética Médica Dr. Jacinto Magalhães, Centro Hospitalar do Porto, Porto, Portugal.,Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal.,UCIBIO/REQUIMTE, Departamento de Ciências Biológicas, Laboratório de Bioquímica, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal
| | - Mário Sousa
- Unidade Multidisciplinar de Investigação Biomédica (UMIB), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal.,Departamento de Microscopia, Laboratório de Biologia Celular, Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal.,Centro de Genética da Reprodução Prof. Alberto Barros, Porto, Portugal
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5
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Thomasi ABD, Sonntag C, Pires DF, Zuidema D, Benci A, Currie PD, Wood AJ. A Low-Cost Pulse Generator for Exacerbating Muscle Fiber Detachment Phenotypes in Zebrafish. Zebrafish 2018; 15:420-424. [PMID: 29381425 DOI: 10.1089/zeb.2017.1512] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Muscle fiber detachment from myoseptal boundaries is a common finding in zebrafish models of muscular dystrophies. In some instances, there is a weakening of the interaction between muscle fiber and myosepta, which is yet to manifest as a fiber detachment phenotype. Therefore, to push the fiber detachment of muscle, mutant fish but not their wild-type siblings, beyond their binding threshold, a series of small electrical pulses can be applied to the larvae to create a maximal force contraction and ultimately fiber detachment. To do this, we built a digital pulse generator which delivers four 8 ms 30 V pulses in quick succession, and it has the advantage over older analog approaches to pulse generation because it improves accuracy and is appreciably less expensive. Our pulse generator significantly increases fiber detachment in the laminin-α2 deficient, congenital muscular dystrophy type 1a (MDC1a) model lama2-/- fish when compared with controls.
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Affiliation(s)
| | - Carmen Sonntag
- 1 Australian Regenerative Medicine Institute, Monash University , Clayton, Victoria, Australia
| | - Danilo Fernando Pires
- 1 Australian Regenerative Medicine Institute, Monash University , Clayton, Victoria, Australia
| | - David Zuidema
- 2 Monash Facility for Instrumentation and Technology Development, Monash University , Clayton, Victoria, Australia
| | - Antonio Benci
- 2 Monash Facility for Instrumentation and Technology Development, Monash University , Clayton, Victoria, Australia
| | - Peter David Currie
- 1 Australian Regenerative Medicine Institute, Monash University , Clayton, Victoria, Australia
| | - Alasdair John Wood
- 1 Australian Regenerative Medicine Institute, Monash University , Clayton, Victoria, Australia
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6
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Sheikh MO, Halmo SM, Wells L. Recent advancements in understanding mammalian O-mannosylation. Glycobiology 2017; 27:806-819. [PMID: 28810660 PMCID: PMC6082599 DOI: 10.1093/glycob/cwx062] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 06/25/2017] [Accepted: 06/28/2017] [Indexed: 02/07/2023] Open
Abstract
The post-translational glycosylation of select proteins by O-linked mannose (O-mannose or O-man) is a conserved modification from yeast to humans and has been shown to be necessary for proper development and growth. The most well studied O-mannosylated mammalian protein is α-dystroglycan (α-DG). Hypoglycosylation of α-DG results in varying severities of congenital muscular dystrophies, cancer progression and metastasis, and inhibited entry and infection of certain arenaviruses. Defects in the gene products responsible for post-translational modification of α-DG, primarily glycosyltransferases, are the basis for these diseases. The multitude of clinical phenotypes resulting from defective O-mannosylation highlights the biomedical significance of this unique modification. Elucidation of the various O-mannose biosynthetic pathways is imperative to understanding a broad range of human diseases and for the development of novel therapeutics. In this review, we will focus on recent discoveries delineating the various enzymes, structures and functions associated with O-mannose-initiated glycoproteins. Additionally, we discuss current gaps in our knowledge of mammalian O-mannosylation, discuss the evolution of this pathway, and illustrate the utility and limitations of model systems to study functions of O-mannosylation.
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Affiliation(s)
- M Osman Sheikh
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
| | - Stephanie M Halmo
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
- Department of Biochemistry and Molecular Biology, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
| | - Lance Wells
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
- Department of Biochemistry and Molecular Biology, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
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7
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Development Aspects of Zebrafish Myotendinous Junction: a Model System for Understanding Muscle Basement Membrane Formation and Failure. CURRENT PATHOBIOLOGY REPORTS 2017. [DOI: 10.1007/s40139-017-0140-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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8
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Ryckebüsch L. [Potential of the zebrafish model to study congenital muscular dystrophies]. Med Sci (Paris) 2015; 31:912-9. [PMID: 26481031 DOI: 10.1051/medsci/20153110018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In order to better understand the complexity of congenital muscular dystrophies (CMD) and develop new strategies to cure them, it is important to establish new disease models. Due to its numerous helpful attributes, the zebrafish has recently become a very powerful animal model for the study of CMD. For some CMD, this vertebrate model is phenotypically closer to human pathology than the murine model. Over the last few years, researchers have developed innovative techniques to screen rapidly and on a large scale for muscle defects in zebrafish. Furthermore, new genome editing techniques in zebrafish make possible the identification of new disease models. In this review, the major attributes of zebrafish for CMD studies are discussed and the principal models of CMD in zebrafish are highlighted.
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Affiliation(s)
- Lucile Ryckebüsch
- Division of biological sciences, university of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0380, La Jolla, États-Unis
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9
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Bajanca F, Gonzalez-Perez V, Gillespie SJ, Beley C, Garcia L, Theveneau E, Sear RP, Hughes SM. In vivo dynamics of skeletal muscle Dystrophin in zebrafish embryos revealed by improved FRAP analysis. eLife 2015; 4. [PMID: 26459831 PMCID: PMC4601390 DOI: 10.7554/elife.06541] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 09/10/2015] [Indexed: 12/30/2022] Open
Abstract
Dystrophin forms an essential link between sarcolemma and cytoskeleton, perturbation of which causes muscular dystrophy. We analysed Dystrophin binding dynamics in vivo for the first time. Within maturing fibres of host zebrafish embryos, our analysis reveals a pool of diffusible Dystrophin and complexes bound at the fibre membrane. Combining modelling, an improved FRAP methodology and direct semi-quantitative analysis of bleaching suggests the existence of two membrane-bound Dystrophin populations with widely differing bound lifetimes: a stable, tightly bound pool, and a dynamic bound pool with high turnover rate that exchanges with the cytoplasmic pool. The three populations were found consistently in human and zebrafish Dystrophins overexpressed in wild-type or dmd(ta222a/ta222a) zebrafish embryos, which lack Dystrophin, and in Gt(dmd-Citrine)(ct90a) that express endogenously-driven tagged zebrafish Dystrophin. These results lead to a new model for Dystrophin membrane association in developing muscle, and highlight our methodology as a valuable strategy for in vivo analysis of complex protein dynamics.
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Affiliation(s)
- Fernanda Bajanca
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom.,CNRS and Université Paul Sabatier, Toulouse, France
| | | | - Sean J Gillespie
- Department of Physics, University of Surrey, Guildford, United Kingdom
| | - Cyriaque Beley
- Université Versailles Saint-Quentin, Montigny-le-Bretonneux, France.,Laboratoire International Associé-Biologie appliquée aux handicaps neuromusculaires, Centre Scientifique de Monaco, Monaco, Monaco
| | - Luis Garcia
- Université Versailles Saint-Quentin, Montigny-le-Bretonneux, France.,Laboratoire International Associé-Biologie appliquée aux handicaps neuromusculaires, Centre Scientifique de Monaco, Monaco, Monaco
| | | | - Richard P Sear
- Department of Physics, University of Surrey, Guildford, United Kingdom
| | - Simon M Hughes
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom
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10
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Knappe S, Zammit PS, Knight RD. A population of Pax7-expressing muscle progenitor cells show differential responses to muscle injury dependent on developmental stage and injury extent. Front Aging Neurosci 2015; 7:161. [PMID: 26379543 PMCID: PMC4548158 DOI: 10.3389/fnagi.2015.00161] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 08/06/2015] [Indexed: 02/03/2023] Open
Abstract
Skeletal muscle regeneration in vertebrates occurs by the activation of quiescent progenitor cells that express pax7 to repair and replace damaged myofibers. We have developed a mechanical injury paradigm in zebrafish to determine whether developmental stage and injury size affect the regeneration dynamics of skeletal muscle. We found that both small focal injuries, and large injuries affecting the entire myotome, lead to expression of myf5 and myogenin, which was prolonged in older larvae, indicating a slower process of regeneration. We characterized the endogenous behavior of a population of muscle-resident Pax7-expressing cells using a pax7a:eGFP transgenic line and found that GFP+ cell migration in the myotome dramatically declined between 5 and 7 days post-fertilization (dpf). Following a small single myotome injury, GFP+ cells responded by extending processes, before migrating to the injured myofibers. Furthermore, these cells responded more rapidly to injury in 4 dpf larvae compared to 7 dpf. Interestingly, we did not see GFP+ myofibers after repair of small injuries, indicating that pax7a-expressing cells did not contribute to myofiber formation in this injury context. On the contrary, numerous GFP+ myofibers could be observed after an extensive single myotome injury. Both injury models were accompanied by an increased number of proliferating GFP+ cells, which was more pronounced in larvae injured at 4 dpf than 7 dpf. This indicates intriguing developmental differences, at these early ages. Our data also suggests an interesting disparity in the role that pax7a-expressing muscle progenitor cells play during skeletal muscle regeneration, which may reflect the extent of muscle damage.
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Affiliation(s)
- Stefanie Knappe
- Department of Craniofacial Development and Stem Cell Biology, Dental Institute, King's College London London, UK
| | - Peter S Zammit
- Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences and Medicine, King's College London London, UK
| | - Robert D Knight
- Department of Craniofacial Development and Stem Cell Biology, Dental Institute, King's College London London, UK
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