101
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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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102
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Cowling BS, Chevremont T, Prokic I, Kretz C, Ferry A, Coirault C, Koutsopoulos O, Laugel V, Romero NB, Laporte J. Reducing dynamin 2 expression rescues X-linked centronuclear myopathy. J Clin Invest 2014; 124:1350-63. [PMID: 24569376 DOI: 10.1172/jci71206] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 11/21/2013] [Indexed: 12/29/2022] Open
Abstract
Centronuclear myopathies (CNM) are congenital disorders associated with muscle weakness and abnormally located nuclei in skeletal muscle. An autosomal dominant form of CNM results from mutations in the gene encoding dynamin 2 (DNM2), and loss-of-function mutations in the gene encoding myotubularin (MTM1) result in X-linked CNM (XLCNM, also called myotubular myopathy), which promotes severe neonatal hypotonia and early death. Currently, no effective treatments exist for XLCNM. Here, we found increased DNM2 levels in XLCNM patients and a mouse model of XLCNM (Mtm1(-/y)). Generation of Mtm1(-/y) mice that were heterozygous for Dnm2 revealed that reduction of DNM2 in XLCNM mice restored life span, whole-body strength, and diaphragm function and increased muscle strength. Additionally, classic CNM-associated histological features, including fiber atrophy and nuclei mispositioning, were absent or reduced. Ultrastructural analysis revealed improvement of sarcomere organization and triad structures. Skeletal muscle-specific decrease of Dnm2 during embryogenesis or in young mice after disease onset revealed that the rescue associated with downregulation of Dnm2 is cell autonomous and is able to stop and potentially revert XLCNM progression. These data indicate that MTM1 and DNM2 regulate muscle organization and force through a common pathway. Furthermore, despite DNM2 being a key mechanoenzyme, its reduction is beneficial for XLCNM and represents a potential therapeutic approach for patients.
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MESH Headings
- Animals
- Diaphragm/physiopathology
- Down-Regulation
- Dynamin II/genetics
- Dynamin II/metabolism
- Female
- Gene Expression
- Humans
- Male
- Mice
- Mice, Knockout
- Muscle Contraction
- Muscle Strength
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Myopathies, Structural, Congenital/metabolism
- Myopathies, Structural, Congenital/pathology
- Myopathies, Structural, Congenital/therapy
- Phenotype
- Protein Tyrosine Phosphatases, Non-Receptor/metabolism
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103
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Manring H, Abreu E, Brotto L, Weisleder N, Brotto M. Novel excitation-contraction coupling related genes reveal aspects of muscle weakness beyond atrophy-new hopes for treatment of musculoskeletal diseases. Front Physiol 2014; 5:37. [PMID: 24600395 PMCID: PMC3927072 DOI: 10.3389/fphys.2014.00037] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 01/18/2014] [Indexed: 12/16/2022] Open
Abstract
Research over the last decade strengthened the understanding that skeletal muscles are not only the major tissue in the body from a volume point of view but also function as a master regulator contributing to optimal organismal health. These new contributions to the available body of knowledge triggered great interest in the roles of skeletal muscle beyond contraction. The World Health Organization, through its Global Burden of Disease (GBD) report, recently raised further awareness about the key importance of skeletal muscles as the GDB reported musculoskeletal (MSK) diseases have become the second greatest cause of disability, with more than 1.7 billion people in the globe affected by a diversity of MSK conditions. Besides their role in MSK disorders, skeletal muscles are also seen as principal metabolic organs with essential contributions to metabolic disorders, especially those linked to physical inactivity. In this review, we have focused on the unique function of new genes/proteins (i.e., MTMR14, MG29, sarcalumenin, KLF15) that during the last few years have helped provide novel insights about muscle function in health and disease, muscle fatigue, muscle metabolism, and muscle aging. Next, we provide an in depth discussion of how these genes/proteins converge into a common function of acting as regulators of intracellular calcium homeostasis. A clear link between dysfunctional calcium homeostasis is established and the special role of store-operated calcium entry is analyzed. The new knowledge that has been generated by the understanding of the roles of previously unknown modulatory genes of the skeletal muscle excitation-contraction coupling (ECC) process brings exciting new possibilities for treatment of MSK diseases, muscle regeneration, and skeletal muscle tissue engineering. The next decade of skeletal muscle and MSK research is bound to bring to fruition applied knowledge that will hopefully offset the current heavy and sad burden of MSK diseases on the planet.
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Affiliation(s)
- Heather Manring
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center Columbus, OH, USA
| | - Eduardo Abreu
- Muscle Biology Research Group, School of Nursing and Health Studies, University of Missouri-Kansas City Kansas City, MO, USA
| | - Leticia Brotto
- Muscle Biology Research Group, School of Nursing and Health Studies, University of Missouri-Kansas City Kansas City, MO, USA
| | - Noah Weisleder
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center Columbus, OH, USA
| | - Marco Brotto
- Muscle Biology Research Group, School of Nursing and Health Studies, University of Missouri-Kansas City Kansas City, MO, USA ; Basic Medical Sciences Pharmacology, School of Medicine, University of Missouri-Kansas City Kansas City, MO, USA ; Basic Medical Sciences Pharmacology, School of Pharmacy, University of Missouri-Kansas City Kansas City, MO, USA
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104
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Smith LL, Gupta VA, Beggs AH. Bridging integrator 1 (Bin1) deficiency in zebrafish results in centronuclear myopathy. Hum Mol Genet 2014; 23:3566-78. [PMID: 24549043 DOI: 10.1093/hmg/ddu067] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Autosomal recessive centronuclear myopathy (CNM2), caused by mutations in bridging integrator 1 (BIN1), is a mildly progressive neuromuscular disorder characterized by abnormally centralized myonuclei and muscle weakness. BIN1 is important for membrane sensing and remodeling in vitro in different cell types. However, to fully understand the biological roles of BIN1 in vivo and to answer critical questions concerning the muscle-specific function of BIN1 in vertebrates, robust small animal models are required. In this study, we create and characterize a novel zebrafish model of CNM2 using antisense morpholinos. Immunofluorescence and histopathological analyses of Bin1-deficient zebrafish skeletal muscle reveal structural defects commonly reported in human CNM2 biopsies. Live imaging of zebrafish embryos shows defective calcium release in bin1 morphants, linking the presence of abnormal triads to impairments in intracellular signaling. RNA-mediated rescue assays demonstrate that knockdown of zebrafish bin1 can reliably examine the pathogenicity of novel BIN1 mutations in vivo. Finally, our results strongly suggest that the phosphoinositide-binding domain of BIN1, present only in skeletal muscle isoforms, may be more critical for muscle maturation and maintenance than for early muscle development. Overall, our data support that BIN1 plays an important role in membrane tubulation and may promote skeletal muscle weakness in CNM2 by disrupting machinery necessary for excitation-contraction coupling in vertebrate organisms. The reproducible phenotype of Bin1-deficient zebrafish, together with the generalized advantages of the teleost system, makes this model readily adaptable to high-throughput screening strategies and may be used to identify therapies for CNM2 and related neuromuscular diseases.
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Affiliation(s)
- Laura L Smith
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Vandana A Gupta
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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105
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Abstract
Phosphoinositides (PIs) are minor lipid components of cellular membranes that play critical roles in membrane dynamics, trafficking, and cellular signaling. Among the seven naturally occurring PIs, the monophosphate phosphatidylinositol 3-phosphate (PtdIns3P) and the bisphosphate phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P2] have been mainly associated with endosomes and endosomal functions. Metabolic labeling and HPLC analysis revealed that a bulk of PtdIns3P is constitutively present in cells, making it the only detectable product of the enzymes phosphoinositide 3-kinases in unstimulated, normal cells. The use of specific tagged-PtdIns3P-binding domains later demonstrated that this constitutive PtdIns3P accumulates in endosomes where it critically regulates trafficking and membrane dynamics.
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Affiliation(s)
- Tania Maffucci
- Inositide Signalling Group, Centre for Diabetes, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Marco Falasca
- Inositide Signalling Group, Centre for Diabetes, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom.
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106
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Smith LL, Beggs AH, Gupta VA. Analysis of skeletal muscle defects in larval zebrafish by birefringence and touch-evoke escape response assays. J Vis Exp 2013:e50925. [PMID: 24378748 DOI: 10.3791/50925] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Zebrafish (Danio rerio) have become a particularly effective tool for modeling human diseases affecting skeletal muscle, including muscular dystrophies, congenital myopathies, and disruptions in sarcomeric assembly, due to high genomic and structural conservation with mammals. Muscular disorganization and locomotive impairment can be quickly assessed in the zebrafish over the first few days post-fertilization. Two assays to help characterize skeletal muscle defects in zebrafish are birefringence (structural) and touch-evoked escape response (behavioral). Birefringence is a physical property in which light is rotated as it passes through ordered matter, such as the pseudo-crystalline array of muscle sarcomeres. It is a simple, noninvasive approach to assess muscle integrity in translucent zebrafish larvae early in development. Wild-type zebrafish with highly organized skeletal muscle appear very bright amidst a dark background when visualized between two polarized light filters, whereas muscle mutants have birefringence patterns specific to the primary muscular disorder they model. Zebrafish modeling muscular dystrophies, diseases characterized by myofiber degeneration followed by repeated rounds of regeneration, exhibit degenerative dark patches in skeletal muscle under polarized light. Nondystrophic myopathies are not associated with necrosis or regenerative changes, but result in disorganized myofibers and skeletal muscle weakness. Myopathic zebrafish typically show an overall reduction in birefringence, reflecting the disorganization of sarcomeres. The touch-evoked escape assay involves observing an embryo's swimming behavior in response to tactile stimulation. In comparison to wild-type larvae, mutant larvae frequently display a weak escape contraction, followed by slow swimming or other type of impaired motion that fails to propel the larvae more than a short distance. The advantage of these assays is that disease progression in the same fish type can be monitored in vivo for several days, and that large numbers of fish can be analyzed in a short time relative to higher vertebrates.
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Affiliation(s)
- Laura L Smith
- Division of Genetics and Genomics, Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School
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107
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Gupta V, Ravenscroft G, Shaheen R, Todd E, Swanson L, Shiina M, Ogata K, Hsu C, Clarke N, Darras B, Farrar M, Hashem A, Manton N, Muntoni F, North K, Sandaradura S, Nishino I, Hayashi Y, Sewry C, Thompson E, Yau K, Brownstein C, Yu T, Allcock R, Davis M, Wallgren-Pettersson C, Matsumoto N, Alkuraya F, Laing N, Beggs A. Identification of KLHL41 Mutations Implicates BTB-Kelch-Mediated Ubiquitination as an Alternate Pathway to Myofibrillar Disruption in Nemaline Myopathy. Am J Hum Genet 2013; 93:1108-17. [PMID: 24268659 DOI: 10.1016/j.ajhg.2013.10.020] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 10/15/2013] [Accepted: 10/22/2013] [Indexed: 02/09/2023] Open
Abstract
Nemaline myopathy (NM) is a rare congenital muscle disorder primarily affecting skeletal muscles that results in neonatal death in severe cases as a result of associated respiratory insufficiency. NM is thought to be a disease of sarcomeric thin filaments as six of eight known genes whose mutation can cause NM encode components of that structure, however, recent discoveries of mutations in non-thin filament genes has called this model in question. We performed whole-exome sequencing and have identified recessive small deletions and missense changes in the Kelch-like family member 41 gene (KLHL41) in four individuals from unrelated NM families. Sanger sequencing of 116 unrelated individuals with NM identified compound heterozygous changes in KLHL41 in a fifth family. Mutations in KLHL41 showed a clear phenotype-genotype correlation: Frameshift mutations resulted in severe phenotypes with neonatal death, whereas missense changes resulted in impaired motor function with survival into late childhood and/or early adulthood. Functional studies in zebrafish showed that loss of Klhl41 results in highly diminished motor function and myofibrillar disorganization, with nemaline body formation, the pathological hallmark of NM. These studies expand the genetic heterogeneity of NM and implicate a critical role of BTB-Kelch family members in maintenance of sarcomeric integrity in NM.
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108
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Horstick EJ, Gibbs EM, Li X, Davidson AE, Dowling JJ. Analysis of embryonic and larval zebrafish skeletal myofibers from dissociated preparations. J Vis Exp 2013:e50259. [PMID: 24300240 DOI: 10.3791/50259] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The zebrafish has proven to be a valuable model system for exploring skeletal muscle function and for studying human muscle diseases. Despite the many advantages offered by in vivo analysis of skeletal muscle in the zebrafish, visualizing the complex and finely structured protein milieu responsible for muscle function, especially in whole embryos, can be problematic. This hindrance stems from the small size of zebrafish skeletal muscle (60 μm) and the even smaller size of the sarcomere. Here we describe and demonstrate a simple and rapid method for isolating skeletal myofibers from zebrafish embryos and larvae. We also include protocols that illustrate post preparation techniques useful for analyzing muscle structure and function. Specifically, we detail the subsequent immunocytochemical localization of skeletal muscle proteins and the qualitative analysis of stimulated calcium release via live cell calcium imaging. Overall, this video article provides a straight-forward and efficient method for the isolation and characterization of zebrafish skeletal myofibers, a technique which provides a conduit for myriad subsequent studies of muscle structure and function.
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Affiliation(s)
- Eric J Horstick
- Departments of Pediatrics and Neurology, University of Michigan
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109
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Gibbs EM, Davidson AE, Telfer WR, Feldman EL, Dowling JJ. The myopathy-causing mutation DNM2-S619L leads to defective tubulation in vitro and in developing zebrafish. Dis Model Mech 2013; 7:157-61. [PMID: 24135484 PMCID: PMC3882057 DOI: 10.1242/dmm.012286] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
DNM2 is a ubiquitously expressed GTPase that regulates multiple subcellular processes. Mutations in DNM2 are a common cause of centronuclear myopathy, a severe disorder characterized by altered skeletal muscle structure and function. The precise mechanisms underlying disease-associated DNM2 mutations are unresolved. We examined the common DNM2-S619L mutation using both in vitro and in vivo approaches. Expression of DNM2-S619L in zebrafish led to the accumulation of aberrant vesicular structures and to defective excitation-contraction coupling. Expression of DNM2-S619L in COS7 cells resulted in defective BIN1-dependent tubule formation. These data suggest that DNM2-S619L causes disease, in part, by interfering with membrane tubulation.
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Affiliation(s)
- Elizabeth M Gibbs
- Department of Neuroscience, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
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110
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Todd PK, Ackall FY, Hur J, Sharma K, Paulson HL, Dowling JJ. Transcriptional changes and developmental abnormalities in a zebrafish model of myotonic dystrophy type 1. Dis Model Mech 2013; 7:143-55. [PMID: 24092878 PMCID: PMC3882056 DOI: 10.1242/dmm.012427] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Myotonic dystrophy type I (DM1) is a multi-system, autosomal dominant disorder caused by expansion of a CTG repeat sequence in the 3′UTR of the DMPK gene. The size of the repeat sequence correlates with age at onset and disease severity, with large repeats leading to congenital forms of DM1 associated with hypotonia and intellectual disability. In models of adult DM1, expanded CUG repeats lead to an RNA toxic gain of function, mediated at least in part by sequestering specific RNA splicing proteins, most notably muscleblind-related (MBNL) proteins. However, the impact of CUG RNA repeat expression on early developmental processes is not well understood. To better understand early developmental processes in DM1, we utilized the zebrafish, Danio rerio, as a model system. Direct injection of (CUG)91 repeat-containing mRNA into single-cell embryos induces toxicity in the nervous system and muscle during early development. These effects manifest as abnormal morphology, behavioral abnormalities and broad transcriptional changes, as shown by cDNA microarray analysis. Co-injection of zebrafish mbnl2 RNA suppresses (CUG)91 RNA toxicity and reverses the associated behavioral and transcriptional abnormalities. Taken together, these findings suggest that early expression of exogenously transcribed CUG repeat RNA can disrupt normal muscle and nervous system development and provides a new model for DM1 research that is amenable to small-molecule therapeutic development.
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Affiliation(s)
- Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
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111
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Reifler A, Lenk GM, Li X, Groom L, Brooks SV, Wilson D, Bowerson M, Dirksen RT, Meisler MH, Dowling JJ. Murine Fig4 is dispensable for muscle development but required for muscle function. Skelet Muscle 2013; 3:21. [PMID: 24004519 PMCID: PMC3844516 DOI: 10.1186/2044-5040-3-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 07/29/2013] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Phosphatidylinositol phosphates (PIPs) are low-abundance phospholipids that participate in a range of cellular processes, including cell migration and membrane traffic. PIP levels and subcellular distribution are regulated by a series of lipid kinases and phosphatases. In skeletal muscle, PIPs and their enzymatic regulators serve critically important functions exemplified by mutations of the PIP phosphatase MTM1 in myotubular myopathy (MTM), a severe muscle disease characterized by impaired muscle structure and abnormal excitation-contraction coupling. FIG4 functions as a PIP phosphatase that participates in both the synthesis and breakdown of phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2). Mutation of FIG4 results in a severe neurodegenerative disorder in mice and a progressive peripheral polyneuropathy in humans. The effect of FIG4 mutation on skeletal muscle has yet to be examined. METHODS Herein we characterize the impact of FIG4 on skeletal muscle development and function using the spontaneously occurring mouse mutant pale tremor (plt), a mouse line with a loss of function mutation in Fig4. RESULTS In plt mice, we characterized abnormalities in skeletal muscle, including reduced muscle size and specific force generation. We also uncovered ultrastructural abnormalities and increased programmed cell death. Conversely, we detected no structural or functional abnormalities to suggest impairment of excitation-contraction coupling, a process previously shown to be influenced by PI(3,5)P2 levels. Conditional rescue of Fig4 mutation in neurons prevented overt muscle weakness and the development of obvious muscle abnormalities, suggesting that the changes observed in the plt mice were primarily related to denervation of skeletal muscle. On the basis of the ability of reduced FIG4 levels to rescue aspects of Mtmr2-dependent neuropathy, we evaluated the effect of Fig4 haploinsufficiency on the myopathy of Mtm1-knockout mice. Male mice with a compound Fig4+/-/Mtm1-/Y genotype displayed no improvements in muscle histology, muscle size or overall survival, indicating that FIG4 reduction does not ameliorate the Mtm1-knockout phenotype. CONCLUSIONS Overall, these data indicate that loss of Fig4 impairs skeletal muscle function but does not significantly affect its structural development.
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Affiliation(s)
- Aaron Reifler
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109-2200, USA
| | - Guy M Lenk
- Department of Human Genetics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
| | - Xingli Li
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
| | - Linda Groom
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Susan V Brooks
- Molecular and Integrative Physiology, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
| | - Desmond Wilson
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
| | - Michyla Bowerson
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
| | - James J Dowling
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
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112
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Jungbluth H, Wallgren-Pettersson C, Laporte JF. 198th ENMC International Workshop: 7th Workshop on Centronuclear (Myotubular) myopathies, 31st May - 2nd June 2013, Naarden, The Netherlands. Neuromuscul Disord 2013; 23:1033-43. [PMID: 24070817 DOI: 10.1016/j.nmd.2013.08.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 08/19/2013] [Indexed: 12/23/2022]
Affiliation(s)
- Heinz Jungbluth
- Department of Paediatric Neurology - Neuromuscular Service, Evelina Children's Hospital, St Thomas' Hospital, London, UK; Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section, London, UK; Clinical Neuroscience Division, King's College, London, UK
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113
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The myotubularin-amphiphysin 2 complex in membrane tubulation and centronuclear myopathies. EMBO Rep 2013; 14:907-15. [PMID: 23917616 DOI: 10.1038/embor.2013.119] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 06/04/2013] [Accepted: 07/18/2013] [Indexed: 11/09/2022] Open
Abstract
Myotubularin (MTM1) and amphiphysin 2 (BIN1) are two proteins mutated in different forms of centronuclear myopathy, but the functional and pathological relationship between these two proteins was unknown. Here, we identified MTM1 as a novel binding partner of BIN1, both in vitro and endogenously in skeletal muscle. Moreover, MTM1 enhances BIN1-mediated membrane tubulation, depending on binding and phosphoinositide phosphatase activity. BIN1 patient mutations induce a conformational change in BIN1 and alter its binding and regulation by MTM1. In conclusion, we identified the first molecular and functional link between MTM1 and BIN1, supporting a common pathological mechanism in different forms of centronuclear myopathy.
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114
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Gibbs EM, Horstick EJ, Dowling JJ. Swimming into prominence: the zebrafish as a valuable tool for studying human myopathies and muscular dystrophies. FEBS J 2013; 280:4187-97. [PMID: 23809187 DOI: 10.1111/febs.12412] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 06/07/2013] [Accepted: 06/20/2013] [Indexed: 11/28/2022]
Abstract
A new and exciting phase of muscle disease research has recently been entered. The application of next generation sequencing technology has spurred an unprecedented era of gene discovery for both myopathies and muscular dystrophies. Gene-based therapies for Duchenne muscular dystrophy have entered clinical trial, and several pathway-based therapies are doing so as well for a handful of muscle diseases. While many factors have aided the extraordinary developments in gene discovery and therapy development, the zebrafish model system has emerged as a vital tool in these advancements. In this review, we will highlight how the zebrafish has greatly aided in the identification of new muscle disease genes and in the recognition of novel therapeutic strategies. We will start with a general introduction to the zebrafish as a model, discuss the ways in which muscle disease can be modeled and analyzed in the fish, and conclude with observations from recent studies that highlight the power of the fish as a research tool for muscle disease.
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Affiliation(s)
- Elizabeth M Gibbs
- Departments of Neuroscience, Neurology and Pediatrics, University of Michigan Medical Center, Ann Arbor, MI, USA
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115
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Sloboda DD, Claflin DR, Dowling JJ, Brooks SV. Force measurement during contraction to assess muscle function in zebrafish larvae. J Vis Exp 2013. [PMID: 23912162 PMCID: PMC3846141 DOI: 10.3791/50539] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Zebrafish larvae provide models of muscle development, muscle disease and muscle-related chemical toxicity, but related studies often lack functional measures of muscle health. In this video article, we demonstrate a method to measure force generation during contraction of zebrafish larval trunk muscle. Force measurements are accomplished by placing an anesthetized larva into a chamber filled with a salt solution. The anterior end of the larva is tied to a force transducer and the posterior end of the larva is tied to a length controller. An isometric twitch contraction is elicited by electric field stimulation and the force response is recorded for analysis. Force generation during contraction provides a measure of overall muscle health and specifically provides a measure of muscle function. Although we describe this technique for use with wild-type larvae, this method can be used with genetically modified larvae or with larvae treated with drugs or toxicants, to characterize muscle disease models and evaluate treatments, or to study muscle development, injury, or chemical toxicity.
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Affiliation(s)
- Darcée D Sloboda
- Department of Biomedical Engineering, University of Michigan, Michigan, USA
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116
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Ha K, Buchan JG, Alvarado DM, McCall K, Vydyanath A, Luther PK, Goldsmith MI, Dobbs MB, Gurnett CA. MYBPC1 mutations impair skeletal muscle function in zebrafish models of arthrogryposis. Hum Mol Genet 2013; 22:4967-77. [PMID: 23873045 DOI: 10.1093/hmg/ddt344] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Myosin-binding protein C1 (MYBPC1) is an abundant skeletal muscle protein that is expressed predominantly in slow-twitch muscle fibers. Human MYBPC1 mutations are associated with distal arthrogryposis type 1 and lethal congenital contracture syndrome type 4. As MYBPC1 function is incompletely understood, the mechanism by which human mutations result in contractures is unknown. Here, we demonstrate using antisense morpholino knockdown, that mybpc1 is required for embryonic motor activity and survival in a zebrafish model of arthrogryposis. Mybpc1 morphant embryos have severe body curvature, cardiac edema, impaired motor excitation and are delayed in hatching. Myofibril organization is selectively impaired in slow skeletal muscle and sarcomere numbers are greatly reduced in mybpc1 knockdown embryos, although electron microscopy reveals normal sarcomere structure. To evaluate the effects of human distal arthrogryposis mutations, mybpc1 mRNAs containing the corresponding human W236R and Y856H MYBPC1 mutations were injected into embryos. Dominant-negative effects of these mutations were suggested by the resultant mild bent body curvature, decreased motor activity, as well as impaired overall survival compared with overexpression of wild-type RNA. These results demonstrate a critical role for mybpc1 in slow skeletal muscle development and establish zebrafish as a tractable model of human distal arthrogryposis.
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Shichiji M, Biancalana V, Fardeau M, Hogrel JY, Osawa M, Laporte J, Romero NB. Extensive morphological and immunohistochemical characterization in myotubular myopathy. Brain Behav 2013; 3:476-86. [PMID: 24381816 PMCID: PMC3869686 DOI: 10.1002/brb3.147] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 05/02/2013] [Accepted: 05/06/2013] [Indexed: 11/30/2022] Open
Abstract
The X-linked myotubular myopathy (XLMTM) also called X-linked centronuclear myopathy is a rare congenital myopathy due to mutations in the MTM 1 gene encoding myotubularin. The disease gives rise to a severe muscle weakness in males at birth. The main muscle morphological characteristics (significant number of small muscle fibers with centralized nuclei and type 1 fiber predominance) are usually documented, but the sequence of formation and maintenance of this particular morphological pattern has not been extensively characterized in humans. In this study, we perform a reevaluation of morphological changes in skeletal muscle biopsies in severe XLMTM. We correlate the pathologic features observed in the muscle biopsies of 15 newborns with MTM 1-mutations according to the "adjusted-age" at the time of muscle biopsy, focusing on sequential analysis in the early period of the life (from 34 weeks of gestation to 3 months of age). We found a similar morphological pattern throughout the period analyzed; the proportion of myofibers with central nuclei was high in all muscle biopsies, independently of the muscle type, the age of the newborns at time of biopsy and the specific MTM 1 mutation. We did not observe a period free of morphological abnormalities in human skeletal muscle as observed in myotubularin-deficient mouse models. In addition, this study demonstrated some features of delayed maturation of the muscle fibers without any increase in the number of satellite cells, associated with a marked disorganization of the muscle T-tubules and cytoskeletal network in the skeletal muscle fibers.
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Affiliation(s)
- Minobu Shichiji
- Unité de Morphologie Neuromusculaire, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France ; Department of Pediatrics, Tokyo Woman's Medical University Tokyo, Japan
| | - Valérie Biancalana
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CNRS, UMR7104, INSERM, U964, Collège de France, Université de Strasbourg Illkirch, France ; Laboratoire Diagnostic Génétique, Faculté de Médecine - CHRU Strasbourg, France
| | - Michel Fardeau
- Unité de Morphologie Neuromusculaire, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France ; Groupe Hospitalier-Universitaire La Pitié-Salpêtrière, AP-HP, Centre de référence des maladies neuromusculaires Paris-Est, Paris, France
| | - Jean-Yves Hogrel
- UPMC-Paris6 UR76, INSERM UMR974, CNRS UMR 7215, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France
| | - Makiko Osawa
- Department of Pediatrics, Tokyo Woman's Medical University Tokyo, Japan
| | - Jocelyn Laporte
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CNRS, UMR7104, INSERM, U964, Collège de France, Université de Strasbourg Illkirch, France
| | - Norma Beatriz Romero
- Unité de Morphologie Neuromusculaire, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France ; Groupe Hospitalier-Universitaire La Pitié-Salpêtrière, AP-HP, Centre de référence des maladies neuromusculaires Paris-Est, Paris, France ; UPMC-Paris6 UR76, INSERM UMR974, CNRS UMR 7215, Institut de Myologie GHU La Pitié-Salpêtrière, Paris, France
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118
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Gupta VA, Hnia K, Smith LL, Gundry SR, McIntire JE, Shimazu J, Bass JR, Talbot EA, Amoasii L, Goldman NE, Laporte J, Beggs AH. Loss of catalytically inactive lipid phosphatase myotubularin-related protein 12 impairs myotubularin stability and promotes centronuclear myopathy in zebrafish. PLoS Genet 2013; 9:e1003583. [PMID: 23818870 PMCID: PMC3688503 DOI: 10.1371/journal.pgen.1003583] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 05/07/2013] [Indexed: 01/08/2023] Open
Abstract
X-linked myotubular myopathy (XLMTM) is a congenital disorder caused by mutations of the myotubularin gene, MTM1. Myotubularin belongs to a large family of conserved lipid phosphatases that include both catalytically active and inactive myotubularin-related proteins (i.e., "MTMRs"). Biochemically, catalytically inactive MTMRs have been shown to form heteroligomers with active members within the myotubularin family through protein-protein interactions. However, the pathophysiological significance of catalytically inactive MTMRs remains unknown in muscle. By in vitro as well as in vivo studies, we have identified that catalytically inactive myotubularin-related protein 12 (MTMR12) binds to myotubularin in skeletal muscle. Knockdown of the mtmr12 gene in zebrafish resulted in skeletal muscle defects and impaired motor function. Analysis of mtmr12 morphant fish showed pathological changes with central nucleation, disorganized Triads, myofiber hypotrophy and whorled membrane structures similar to those seen in X-linked myotubular myopathy. Biochemical studies showed that deficiency of MTMR12 results in reduced levels of myotubularin protein in zebrafish and mammalian C2C12 cells. Loss of myotubularin also resulted in reduction of MTMR12 protein in C2C12 cells, mice and humans. Moreover, XLMTM mutations within the myotubularin interaction domain disrupted binding to MTMR12 in cell culture. Analysis of human XLMTM patient myotubes showed that mutations that disrupt the interaction between myotubularin and MTMR12 proteins result in reduction of both myotubularin and MTMR12. These studies strongly support the concept that interactions between myotubularin and MTMR12 are required for the stability of their functional protein complex in normal skeletal muscles. This work highlights an important physiological function of catalytically inactive phosphatases in the pathophysiology of myotubular myopathy and suggests a novel therapeutic approach through identification of drugs that could stabilize the myotubularin-MTMR12 complex and hence ameliorate this disorder.
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Affiliation(s)
- Vandana A. Gupta
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Karim Hnia
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Inserm U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Laura L. Smith
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Stacey R. Gundry
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jessica E. McIntire
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Junko Shimazu
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jessica R. Bass
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Ethan A. Talbot
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Leonela Amoasii
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Inserm U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Nathaniel E. Goldman
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jocelyn Laporte
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Inserm U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Alan H. Beggs
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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119
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Böhm J, Vasli N, Maurer M, Cowling B, Shelton GD, Kress W, Toussaint A, Prokic I, Schara U, Anderson TJ, Weis J, Tiret L, Laporte J. Altered splicing of the BIN1 muscle-specific exon in humans and dogs with highly progressive centronuclear myopathy. PLoS Genet 2013; 9:e1003430. [PMID: 23754947 PMCID: PMC3675003 DOI: 10.1371/journal.pgen.1003430] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 02/18/2013] [Indexed: 11/29/2022] Open
Abstract
Amphiphysin 2, encoded by BIN1, is a key factor for membrane sensing and remodelling in different cell types. Homozygous BIN1 mutations in ubiquitously expressed exons are associated with autosomal recessive centronuclear myopathy (CNM), a mildly progressive muscle disorder typically showing abnormal nuclear centralization on biopsies. In addition, misregulation of BIN1 splicing partially accounts for the muscle defects in myotonic dystrophy (DM). However, the muscle-specific function of amphiphysin 2 and its pathogenicity in both muscle disorders are not well understood. In this study we identified and characterized the first mutation affecting the splicing of the muscle-specific BIN1 exon 11 in a consanguineous family with rapidly progressive and ultimately fatal centronuclear myopathy. In parallel, we discovered a mutation in the same BIN1 exon 11 acceptor splice site as the genetic cause of the canine Inherited Myopathy of Great Danes (IMGD). Analysis of RNA from patient muscle demonstrated complete skipping of exon 11 and BIN1 constructs without exon 11 were unable to promote membrane tubulation in differentiated myotubes. Comparative immunofluorescence and ultrastructural analyses of patient and canine biopsies revealed common structural defects, emphasizing the importance of amphiphysin 2 in membrane remodelling and maintenance of the skeletal muscle triad. Our data demonstrate that the alteration of the muscle-specific function of amphiphysin 2 is a common pathomechanism for centronuclear myopathy, myotonic dystrophy, and IMGD. The IMGD dog is the first faithful model for human BIN1-related CNM and represents a mammalian model available for preclinical trials of potential therapies. The intracellular organization of muscle fibers relies on a complex membrane system important for muscle structural organization, maintenance, contraction, and resistance to stress. Amphiphysin 2, encoded by BIN1, plays a central role in membrane sensing and remodelling and is involved in intracellular membrane trafficking in different cell types. The ubiquitously expressed BIN1, altered in centronuclear myopathy (CNM) and myotonic dystrophy (DM), possesses a muscle-specific exon coding for a phosphoinositide binding domain. We identified splice mutations affecting the muscle-specific BIN1 isoform in humans and dogs presenting a clinically and histopathologically comparable highly progressive centronuclear myopathy. Our functional and ultrastructural data emphasize the importance of amphiphysin 2 in membrane remodeling and suggest that the defective maintenance of the triad structure is a primary cause for the muscle weakness. The canine Inherited Myopathy of Great Danes is the first faithful mammalian model for investigating other potential pathological mechanisms underlying centronuclear myopathy and for testing therapeutic approaches.
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Affiliation(s)
- Johann Böhm
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France
- Inserm, U964, Illkirch, France
- CNRS, UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
- Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Nasim Vasli
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France
- Inserm, U964, Illkirch, France
- CNRS, UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
- Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Marie Maurer
- Université Paris-Est Créteil, CNM project, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- INRA, UMR955 de Génétique Fonctionnelle et Médicale, Maisons-Alfort, France
| | - Belinda Cowling
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France
- Inserm, U964, Illkirch, France
- CNRS, UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
- Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - G. Diane Shelton
- Department of Pathology, University of California at San Diego, La Jolla, California, United States of America
| | - Wolfram Kress
- Department of Human Genetics, Julius-Maximilian University, Würzburg, Germany
| | - Anne Toussaint
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France
- Inserm, U964, Illkirch, France
- CNRS, UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
- Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Ivana Prokic
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France
- Inserm, U964, Illkirch, France
- CNRS, UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
- Collège de France, Chaire de Génétique Humaine, Illkirch, France
| | - Ulrike Schara
- Department of Neuropediatrics, University of Essen, Essen, Germany
| | - Thomas James Anderson
- Institute of Comparative Medicine, Division of Companion Animal Sciences, University of Glasgow Veterinary School, Glasgow, United Kingdom
| | - Joachim Weis
- Institute of Neuropathology and JARA Brain Translational Medicine, RWTH Aachen University, Aachen, Germany
| | - Laurent Tiret
- Université Paris-Est Créteil, CNM project, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France
- INRA, UMR955 de Génétique Fonctionnelle et Médicale, Maisons-Alfort, France
| | - Jocelyn Laporte
- IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), Illkirch, France
- Inserm, U964, Illkirch, France
- CNRS, UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
- Collège de France, Chaire de Génétique Humaine, Illkirch, France
- * E-mail:
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120
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Gibbs EM, Clarke NF, Rose K, Oates EC, Webster R, Feldman EL, Dowling JJ. Neuromuscular junction abnormalities in DNM2-related centronuclear myopathy. J Mol Med (Berl) 2013; 91:727-37. [PMID: 23338057 DOI: 10.1007/s00109-013-0994-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 11/15/2012] [Accepted: 01/02/2013] [Indexed: 12/13/2022]
Abstract
Dynamin-2-related centronuclear myopathy (DNM2-CNM) is a clinically heterogeneous muscle disorder characterized by muscle weakness and centralized nuclei on biopsy. There is little known about the muscle dysfunction underlying this disorder, and there are currently no treatments. In this study, we establish a novel zebrafish model for DNM2-CNM by transiently overexpressing a mutant version of DNM2 (DNM2-S619L) during development. We show that overexpression of DNM2-S619L leads to pathological changes in muscle and a severe motor phenotype. We further demonstrate that the muscle weakness seen in these animals can be significantly alleviated by treatment with an acetylcholinesterase inhibitor. Based on these results, we reviewed the clinical history of five patients with two different DNM2-CNM mutations (S619L and E368K) and found electrophysiological evidence of abnormal neuromuscular transmission in two of the individuals. All five patients showed improved muscle strength and motor function, and/or reduced fatigability following acetylcholinesterase inhibitor treatment. Together, our results suggest that deficits at the neuromuscular junction may play an important role in the pathogenesis of DNM2-CNM and that treatments targeting this dysfunction can provide an effective therapy for patients with this disorder.
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Affiliation(s)
- Elizabeth M Gibbs
- Department of Neurology, Taubman Medical Research Institute, University of Michigan Medical Center, BSRB 5017, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA.
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121
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Hendriks WJAJ, Pulido R. Protein tyrosine phosphatase variants in human hereditary disorders and disease susceptibilities. Biochim Biophys Acta Mol Basis Dis 2013; 1832:1673-96. [PMID: 23707412 DOI: 10.1016/j.bbadis.2013.05.022] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 05/14/2013] [Accepted: 05/16/2013] [Indexed: 12/18/2022]
Abstract
Reversible tyrosine phosphorylation of proteins is a key regulatory mechanism to steer normal development and physiological functioning of multicellular organisms. Phosphotyrosine dephosphorylation is exerted by members of the super-family of protein tyrosine phosphatase (PTP) enzymes and many play such essential roles that a wide variety of hereditary disorders and disease susceptibilities in man are caused by PTP alleles. More than two decades of PTP research has resulted in a collection of PTP genetic variants with corresponding consequences at the molecular, cellular and physiological level. Here we present a comprehensive overview of these PTP gene variants that have been linked to disease states in man. Although the findings have direct bearing for disease diagnostics and for research on disease etiology, more work is necessary to translate this into therapies that alleviate the burden of these hereditary disorders and disease susceptibilities in man.
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Affiliation(s)
- Wiljan J A J Hendriks
- Department of Cell Biology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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122
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Al-Qusairi L, Prokic I, Amoasii L, Kretz C, Messaddeq N, Mandel JL, Laporte J. Lack of myotubularin (MTM1) leads to muscle hypotrophy through unbalanced regulation of the autophagy and ubiquitin-proteasome pathways. FASEB J 2013; 27:3384-94. [PMID: 23695157 DOI: 10.1096/fj.12-220947] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mutations in the phosphoinositide phosphatase myotubularin (MTM1) results in X-linked myotubular/centronuclear myopathy (XLMTM), characterized by a severe decrease in muscle mass and strength in patients and murine models. However, the molecular mechanism involved in the muscle hypotrophy is unclear. Here we show that the IGF1R/Akt pathway is affected in Mtm1-deficient murine muscles, characterized by an increase in IGF1 receptor and Akt levels in both the presymptomatic and symptomatic phases. Moreover, up-regulation of atrogenes was observed in the presymptomatic phase of the myopathy, supporting overactivation of the ubiquitin-proteasome pathway. In parallel, the autophagy machinery was affected as indicated by the increase in the number of autophagosomes and of autophagy markers, such as LC3 and P62. However, phosphorylation of FOXO3a and mTOR were abnormal at late but not at early stages of the disease, suggesting that myotubularin acts both upstream in the IGF1R/Akt pathway and downstream on the balance between the autophagy and ubiquitin-proteasome pathways in vivo. Adeno-associated virus-mediated delivery of Mtm1 into Mtm1-null muscles rescued muscle mass and normalized the expression levels of IGF1 receptor, the ubiquitin-proteasome pathway, and autophagy markers. These data support the hypothesis that the unbalanced regulation of the ubiquitin proteasome pathway and the autophagy machinery is a primary cause of the XLMTM pathogenesis.
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Affiliation(s)
- Lama Al-Qusairi
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
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123
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Davidson AE, Siddiqui FM, Lopez MA, Lunt P, Carlson HA, Moore BE, Love S, Born DE, Roper H, Majumdar A, Jayadev S, Underhill HR, Smith CO, von der Hagen M, Hubner A, Jardine P, Merrison A, Curtis E, Cullup T, Jungbluth H, Cox MO, Winder TL, Abdel Salam H, Li JZ, Moore SA, Dowling JJ. Novel deletion of lysine 7 expands the clinical, histopathological and genetic spectrum of TPM2-related myopathies. ACTA ACUST UNITED AC 2013; 136:508-21. [PMID: 23413262 DOI: 10.1093/brain/aws344] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The β-tropomyosin gene encodes a component of the sarcomeric thin filament. Rod-shaped dimers of tropomyosin regulate actin-myosin interactions and β-tropomyosin mutations have been associated with nemaline myopathy, cap myopathy, Escobar syndrome and distal arthrogryposis types 1A and 2B. In this study, we expand the allelic spectrum of β-tropomyosin-related myopathies through the identification of a novel β-tropomyosin mutation in two clinical contexts not previously associated with β-tropomyosin. The first clinical phenotype is core-rod myopathy, with a β-tropomyosin mutation uncovered by whole exome sequencing in a family with autosomal dominant distal myopathy and muscle biopsy features of both minicores and nemaline rods. The second phenotype, observed in four unrelated families, is autosomal dominant trismus-pseudocamptodactyly syndrome (distal arthrogryposis type 7; previously associated exclusively with myosin heavy chain 8 mutations). In all four families, the mutation identified was a novel 3-bp in-frame deletion (c.20_22del) that results in deletion of a conserved lysine at the seventh amino acid position (p.K7del). This is the first mutation identified in the extreme N-terminus of β-tropomyosin. To understand the potential pathogenic mechanism(s) underlying this mutation, we performed both computational analysis and in vivo modelling. Our theoretical model predicts that the mutation disrupts the N-terminus of the α-helices of dimeric β-tropomyosin, a change predicted to alter protein-protein binding between β-tropomyosin and other molecules and to disturb head-to-tail polymerization of β-tropomyosin dimers. To create an in vivo model, we expressed wild-type or p.K7del β-tropomyosin in the developing zebrafish. p.K7del β-tropomyosin fails to localize properly within the thin filament compartment and its expression alters sarcomere length, suggesting that the mutation interferes with head-to-tail β-tropomyosin polymerization and with overall sarcomeric structure. We describe a novel β-tropomyosin mutation, two clinical-histopathological phenotypes not previously associated with β-tropomyosin and pathogenic data from the first animal model of β-tropomyosin-related myopathies.
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Affiliation(s)
- Ann E Davidson
- Department of Paediatrics, University of Michigan Medical Centre, Ann Arbor, MI 48109-2200, USA
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Elouarrat D, van der Velden YU, Jones DR, Moolenaar WH, Divecha N, Haramis APG. Role of phosphatidylinositol 5-phosphate 4-kinase α in zebrafish development. Int J Biochem Cell Biol 2013; 45:1293-301. [PMID: 23542014 DOI: 10.1016/j.biocel.2013.03.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/12/2013] [Accepted: 03/13/2013] [Indexed: 10/27/2022]
Abstract
Phosphatidylinositol 5-phosphate 4-kinases (PIP4Ks) phosphorylate phosphatidylinositol 5-phosphate (PI5P) to generate phosphatidylinositol 4,5-bisphosphate; their most likely function is the regulation of the levels of PI5P, a putative signalling intermediate. There are three mammalian PIP4Ks isoforms (α, β and γ), but their physiological roles remain poorly understood. In the present study, we identified the zebrafish orthologue (zPIP4Kα) of the high-activity human PIP4K α isoform and analyzed its role in embryonic development. RT-PCR analysis and whole-mount in situ hybridization experiments showed that zPIP4Kα is maternally expressed. At later embryonic stages, high PIP4Kα expression was detected in the head and the pectoral fins. Knockdown of zPIP4Kα by antisense morpholino oligonucleotides led to severe morphological abnormalities, including midbody winding defects at 48hpf. The abnormal phenotype could be rescued, at least in large part, by injection of human PIP4Kα mRNA. Our results reveal a key role for PIP4Kα and its activity in vertebrate tissue homeostasis and organ development.
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Affiliation(s)
- Dalila Elouarrat
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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125
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Amoasii L, Hnia K, Chicanne G, Brech A, Cowling BS, Müller MM, Schwab Y, Koebel P, Ferry A, Payrastre B, Laporte J. Myotubularin and PtdIns3P remodel the sarcoplasmic reticulum in muscle in vivo. J Cell Sci 2013; 126:1806-19. [PMID: 23444364 DOI: 10.1242/jcs.118505] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The sarcoplasmic reticulum (SR) is a specialized form of endoplasmic reticulum (ER) in skeletal muscle and is essential for calcium homeostasis. The mechanisms involved in SR remodeling and maintenance of SR subdomains are elusive. In this study, we identified myotubularin (MTM1), a phosphoinositide phosphatase mutated in X-linked centronuclear myopathy (XLCNM, or myotubular myopathy), as a key regulator of phosphatidylinositol 3-monophosphate (PtdIns3P) levels at the SR. MTM1 is predominantly located at the SR cisternae of the muscle triads, and Mtm1-deficient mouse muscles and myoblasts from XLCNM patients exhibit abnormal SR/ER networks. In vivo modulation of MTM1 enzymatic activity in skeletal muscle using ectopic expression of wild-type or a dead-phosphatase MTM1 protein leads to differential SR remodeling. Active MTM1 is associated with flat membrane stacks, whereas dead-phosphatase MTM1 mutant promotes highly curved cubic membranes originating from the SR and enriched in PtdIns3P. Overexpression of a tandem FYVE domain with high affinity for PtdIns3P alters the shape of the SR cisternae at the triad. Our findings, supported by the parallel analysis of the Mtm1-null mouse and an in vivo study, reveal a direct function of MTM1 enzymatic activity in SR remodeling and a key role for PtdIns3P in promoting SR membrane curvature in skeletal muscle. We propose that alteration in SR remodeling is a primary cause of X-linked centronuclear myopathy. The tight regulation of PtdIns3P on specific membrane subdomains may be a general mechanism to control membrane curvature.
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Affiliation(s)
- Leonela Amoasii
- Department of Translational Medicine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, 67404 Illkirch, France
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126
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Two dynamin-2 genes are required for normal zebrafish development. PLoS One 2013; 8:e55888. [PMID: 23418470 PMCID: PMC3572173 DOI: 10.1371/journal.pone.0055888] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 01/07/2013] [Indexed: 01/28/2023] Open
Abstract
Dynamin-2 (DNM2) is a large GTPase involved in clathrin-mediated endocytosis and related trafficking pathways. Mutations in human DNM2 cause two distinct neuromuscular disorders: centronuclear myopathy and Charcot-Marie-Tooth disease. Zebrafish have been shown to be an excellent animal model for many neurologic disorders, and this system has the potential to inform our understanding of DNM2-related disease. Currently, little is known about the endogenous zebrafish orthologs to human DNM2. In this study, we characterize two zebrafish dynamin-2 genes, dnm2 and dnm2-like. Both orthologs are structurally similar to human DNM2 at the gene and protein levels. They are expressed throughout early development and in all adult tissues examined. Knockdown of dnm2 and dnm2-like gene products resulted in extensive morphological abnormalities during development, and expression of human DNM2 RNA rescued these phenotypes. Our findings suggest that dnm2 and dnm2-like are orthologs to human DNM2, and that they are required for normal zebrafish development.
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Joubert R, Vignaud A, Le M, Moal C, Messaddeq N, Buj-Bello A. Site-specific Mtm1 mutagenesis by an AAV-Cre vector reveals that myotubularin is essential in adult muscle. Hum Mol Genet 2013; 22:1856-66. [PMID: 23390130 DOI: 10.1093/hmg/ddt038] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Manipulation of the mouse genome by site-specific mutagenesis has been extensively used to study gene function and model human disorders. Mouse models of myotubular myopathy (XLMTM), a severe congenital muscular disorder due to loss-of-function mutations in the MTM1 gene, have been generated by homologous recombination and shown that myotubularin is essential for skeletal muscle. However, since the Mtm1 deletion occurred constitutively or shortly after birth in these mice, it is not known whether myotubularin is required during adulthood, an important issue in the context of not only muscle biology but also therapies. To delete the Mtm1 gene in adult muscle fibers, we constructed a recombinant adeno-associated vector (AAV) that expresses the Cre recombinase under the muscle-specific desmin promoter. We report that a single injection of this vector into muscles of 3-month-old Mtm1 conditional mice leads to a myotubular myopathy phenotype with myofiber atrophy, disorganization of organelle positioning, such as mitochondria and nuclei, T-tubule defects and severe muscle weakness. In addition, our results show that MTM1-related atrophy and dysfunction correlate with abnormalities in satellite cell number and markers of autophagy, protein synthesis and neuromuscular junction transmission. The expression level of atrogenes was also analyzed. Therefore, we provide a valuable tissue model that recapitulates the main features of the disease, and it is useful to study pathogenesis and evaluate therapeutic strategies. We establish the proof-of-concept that myotubularin is required for the proper function of skeletal muscle during adulthood, suggesting that therapies will be required for the entire life of XLMTM patients.
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Affiliation(s)
- Romain Joubert
- Department of Research and Development, Généthon, INSERM, Evry, France
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Lawlor MW, Armstrong D, Viola MG, Widrick JJ, Meng H, Grange RW, Childers MK, Hsu CP, O'Callaghan M, Pierson CR, Buj-Bello A, Beggs AH. Enzyme replacement therapy rescues weakness and improves muscle pathology in mice with X-linked myotubular myopathy. Hum Mol Genet 2013; 22:1525-38. [PMID: 23307925 DOI: 10.1093/hmg/ddt003] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
No effective treatment exists for patients with X-linked myotubular myopathy (XLMTM), a fatal congenital muscle disease caused by deficiency of the lipid phosphatase, myotubularin. The Mtm1δ4 and Mtm1 p.R69C mice model severely and moderately symptomatic XLMTM, respectively, due to differences in the degree of myotubularin deficiency. Contractile function of intact extensor digitorum longus (EDL) and soleus muscles from Mtm1δ4 mice, which produce no myotubularin, is markedly impaired. Contractile forces generated by chemically skinned single fiber preparations from Mtm1δ4 muscle were largely preserved, indicating that weakness was largely due to impaired excitation contraction coupling. Mtm1 p.R69C mice, which produce small amounts of myotubularin, showed impaired contractile function only in EDL muscles. Short-term replacement of myotubularin with a prototypical targeted protein replacement agent (3E10Fv-MTM1) in Mtm1δ4 mice improved contractile function and muscle pathology. These promising findings suggest that even low levels of myotubularin protein replacement can improve the muscle weakness and reverse the pathology that characterizes XLMTM.
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Affiliation(s)
- Michael W Lawlor
- Division of Genetics and Program in Genomics, The Manton Center for Orphan Disease Research, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
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Horstick EJ, Linsley JW, Dowling JJ, Hauser MA, McDonald KK, Ashley-Koch A, Saint-Amant L, Satish A, Cui WW, Zhou W, Sprague SM, Stamm DS, Powell CM, Speer MC, Franzini-Armstrong C, Hirata H, Kuwada JY. Stac3 is a component of the excitation-contraction coupling machinery and mutated in Native American myopathy. Nat Commun 2013; 4:1952. [PMID: 23736855 PMCID: PMC4056023 DOI: 10.1038/ncomms2952] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 04/30/2013] [Indexed: 11/09/2022] Open
Abstract
Excitation-contraction coupling, the process that regulates contractions by skeletal muscles, transduces changes in membrane voltage by activating release of Ca(2+) from internal stores to initiate muscle contraction. Defects in excitation-contraction coupling are associated with muscle diseases. Here we identify Stac3 as a novel component of the excitation-contraction coupling machinery. Using a zebrafish genetic screen, we generate a locomotor mutation that is mapped to stac3. We provide electrophysiological, Ca(2+) imaging, immunocytochemical and biochemical evidence that Stac3 participates in excitation-contraction coupling in muscles. Furthermore, we reveal that a mutation in human STAC3 is the genetic basis of the debilitating Native American myopathy (NAM). Analysis of NAM stac3 in zebrafish shows that the NAM mutation decreases excitation-contraction coupling. These findings enhance our understanding of both excitation-contraction coupling and the pathology of myopathies.
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Affiliation(s)
- Eric J. Horstick
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jeremy W. Linsley
- Cell and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - James J. Dowling
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Michael A. Hauser
- Departments of Medicine and Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
| | - Kristin K. McDonald
- Departments of Medicine and Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
| | - Allison Ashley-Koch
- Departments of Medicine and Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
| | - Louis Saint-Amant
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
- Departement de Pathologie et Biologie Cellulaire, Universite de Montreal, Montreal, Canada H3T 1J4
| | - Akhila Satish
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Wilson W. Cui
- Cell and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Weibin Zhou
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
- Life Science Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Shawn M. Sprague
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Demetra S. Stamm
- Department of Internal Medicine, University of California, Davis, Sacramento, CA 95817, USA
| | - Cynthia M. Powell
- Departments of Pediatrics and Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Marcy C. Speer
- Center for Human Genetics, Duke University, Durham, NC 27710, USA
| | - Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Hiromi Hirata
- National Institute of Genetics, Mishima 411-8540, Japan
| | - John Y. Kuwada
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
- Cell and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA
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Grange RW, Doering J, Mitchell E, Holder MN, Guan X, Goddard M, Tegeler C, Beggs AH, Childers MK. Muscle function in a canine model of X-linked myotubular myopathy. Muscle Nerve 2012; 46:588-91. [PMID: 22987702 DOI: 10.1002/mus.23463] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
INTRODUCTION We established a colony of dogs that harbor an X-linked MTM1 missense mutation.Muscle from affected male dogs exhibits reduction and altered localization of the MTM1 gene product, myotubularin, and provides a model analogous to X-linked myotubular myopathy (XLMTM). METHODS We studied hindlimb muscle function in age-matched canine XLMTM genotypes between ages 9 and 18 weeks. RESULTS By the end of the study, affected dogs produce only ∼15% of the torque generated by normals or carriers (0.023 ± 0.005 vs. 0.152 ± 0.007 and 0.154 ± 0.003 N-m/kg body mass, respectively, P < 0.05) and are too weak to stand unassisted. At this age, XLMTM dogs also demonstrate an abnormally low twitch:tetanus ratio, a right-shifted torque-frequency relationship and an increase in torque during repetitive stimulation (P < 0.05). CONCLUSIONS We hypothesize that muscle weakness results from impaired excitation-contraction (E-C) coupling. Interventions that improve E-C coupling might be translated from the XLMTM dog model to patients.
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Affiliation(s)
- Robert W Grange
- Department of Human Nutrition, Foods and Exercise, College of Agriculture & Life Sciences, Virginia Polytechnic and State University, Blacksburg, Virginia, USA 24060
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131
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Amoasii L, Bertazzi DL, Tronchère H, Hnia K, Chicanne G, Rinaldi B, Cowling BS, Ferry A, Klaholz B, Payrastre B, Laporte J, Friant S. Phosphatase-dead myotubularin ameliorates X-linked centronuclear myopathy phenotypes in mice. PLoS Genet 2012; 8:e1002965. [PMID: 23071445 PMCID: PMC3469422 DOI: 10.1371/journal.pgen.1002965] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 08/08/2012] [Indexed: 12/27/2022] Open
Abstract
Myotubularin MTM1 is a phosphoinositide (PPIn) 3-phosphatase mutated in X-linked centronuclear myopathy (XLCNM; myotubular myopathy). We investigated the involvement of MTM1 enzymatic activity on XLCNM phenotypes. Exogenous expression of human MTM1 in yeast resulted in vacuolar enlargement, as a consequence of its phosphatase activity. Expression of mutants from patients with different clinical progression and determination of PtdIns3P and PtdIns5P cellular levels confirmed the link between vacuolar morphology and MTM1 phosphatase activity, and showed that some disease mutants retain phosphatase activity. Viral gene transfer of phosphatase-dead myotubularin mutants (MTM1(C375S) and MTM1(S376N)) significantly improved most histological signs of XLCNM displayed by a Mtm1-null mouse, at similar levels as wild-type MTM1. Moreover, the MTM1(C375S) mutant improved muscle performance and restored the localization of nuclei, triad alignment, and the desmin intermediate filament network, while it did not normalize PtdIns3P levels, supporting phosphatase-independent roles of MTM1 in maintaining normal muscle performance and organelle positioning in skeletal muscle. Among the different XLCNM signs investigated, we identified only triad shape and fiber size distribution as being partially dependent on MTM1 phosphatase activity. In conclusion, this work uncovers MTM1 roles in the structural organization of muscle fibers that are independent of its enzymatic activity. This underlines that removal of enzymes should be used with care to conclude on the physiological importance of their activity.
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MESH Headings
- Animals
- Desmin/metabolism
- Disease Models, Animal
- Enzyme Activation/genetics
- Gene Expression
- Humans
- Male
- Mice
- Mice, Knockout
- Muscle Strength/genetics
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/ultrastructure
- Mutation
- Myopathies, Structural, Congenital/genetics
- Myopathies, Structural, Congenital/metabolism
- Phenotype
- Phosphatidylinositol Phosphates/metabolism
- Phosphoric Monoester Hydrolases/metabolism
- Protein Tyrosine Phosphatases, Non-Receptor/genetics
- Protein Tyrosine Phosphatases, Non-Receptor/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- Leonela Amoasii
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Dimitri L. Bertazzi
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
| | | | - Karim Hnia
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Gaëtan Chicanne
- INSERM, U1048 and Université Toulouse 3, I2MC, Toulouse, France
| | - Bruno Rinaldi
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
| | - Belinda S. Cowling
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
| | - Arnaud Ferry
- UMRS974, Université Pierre et Marie Curie, Paris, France
| | - Bruno Klaholz
- Department of Integrated Structural Biology, IGBMC, INSERM U964, CNRS UMR7104, Université de Strasbourg, Illkirch, France
| | - Bernard Payrastre
- INSERM, U1048 and Université Toulouse 3, I2MC, Toulouse, France
- CHU de Toulouse, Laboratoire d'Hématologie, Toulouse, France
- * E-mail: (SF); (JL); (BP)
| | - Jocelyn Laporte
- Department of Translational Medecine, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, Université de Strasbourg, Collège de France, Illkirch, France
- * E-mail: (SF); (JL); (BP)
| | - Sylvie Friant
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
- * E-mail: (SF); (JL); (BP)
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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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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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Majczenko K, Davidson A, Camelo-Piragua S, Agrawal P, Manfready R, Li X, Joshi S, Xu J, Peng W, Beggs A, Li J, Burmeister M, Dowling J. Dominant mutation of CCDC78 in a unique congenital myopathy with prominent internal nuclei and atypical cores. Am J Hum Genet 2012; 91:365-71. [PMID: 22818856 DOI: 10.1016/j.ajhg.2012.06.012] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 05/21/2012] [Accepted: 06/05/2012] [Indexed: 10/28/2022] Open
Abstract
Congenital myopathies are clinically and genetically heterogeneous diseases that typically present in childhood with hypotonia and weakness and are most commonly defined by changes observed in muscle biopsy. Approximately 40% of congenital myopathies are currently genetically unresolved. We identified a family with dominantly inherited congenital myopathy characterized by distal weakness and biopsy changes that included core-like areas and increased internalized nuclei. To identify the causative genetic abnormality in this family, we performed linkage analysis followed by whole-exome capture and next-generation sequencing. A splice-acceptor variant in previously uncharacterized CCDC78 was detected in affected individuals and absent in unaffected family members and > 10,000 controls. This variant alters RNA-transcript processing and results in a 222 bp in-frame insertion. CCDC78 is expressed in skeletal muscle, enriched in the perinuclear region and the triad, and found in intracellular aggregates in patient muscle. Modeling of the CCDC78 mutation in zebrafish resulted in changes mirroring the human disease that included altered motor function and abnormal muscle ultrastructure. Using a combination of linkage analysis, next-generation sequencing, and modeling in the zebrafish, we have identified a CCDC78 mutation associated with a unique myopathy with prominent internal nuclei and atypical cores.
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135
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Myotubularin-deficient myoblasts display increased apoptosis, delayed proliferation, and poor cell engraftment. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 181:961-8. [PMID: 22841819 DOI: 10.1016/j.ajpath.2012.05.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 05/09/2012] [Accepted: 05/22/2012] [Indexed: 12/22/2022]
Abstract
X-linked myotubular myopathy is a severe congenital myopathy caused by deficiency of the lipid phosphatase, myotubularin. Recent studies of human tissue and animal models have discovered structural and physiological abnormalities in myotubularin-deficient muscle, but the impact of myotubularin deficiency on myogenic stem cells within muscles is unclear. In the present study, we evaluated the viability, proliferative capacity, and in vivo engraftment of myogenic cells obtained from severely symptomatic (Mtm1δ4) myotubularin-deficient mice. Mtm1δ4 muscle contains fewer myogenic cells than wild-type (WT) littermates, and the number of myogenic cells decreases with age. The behavior of Mtm1δ4 myoblasts is also abnormal, because they engraft poorly into C57BL/6/Rag1null/mdx5cv mice and display decreased proliferation and increased apoptosis compared with WT myoblasts. Evaluation of Mtm1δ4 animals at 21 and 42 days of life detected fewer satellite cells in Mtm1δ4 muscle compared with WT littermates, and the decrease in satellite cells correlated with progression of disease. In addition, analysis of WT and Mtm1δ4 regeneration after injury detected similar abnormalities of satellite cell function, with fewer satellite cells, fewer dividing cells, and increased apoptotic cells in Mtm1δ4 muscle. These studies demonstrate specific abnormalities in myogenic cell number and behavior that may relate to the progression of disease in myotubularin deficiency, and may also be used to develop in vitro assays by which novel treatment strategies can be assessed.
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136
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Nance JR, Dowling JJ, Gibbs EM, Bönnemann CG. Congenital myopathies: an update. Curr Neurol Neurosci Rep 2012; 12:165-74. [PMID: 22392505 DOI: 10.1007/s11910-012-0255-x] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Congenital myopathy is a clinicopathological concept of characteristic histopathological findings on muscle biopsy in a patient with early-onset weakness. Three main categories are recognized within the classical congenital myopathies: nemaline myopathy, core myopathy, and centronuclear myopathy. Recent evidence of overlapping clinical and histological features between the classical forms and their different genetic entities suggests that there may be shared pathomechanisms between the congenital myopathies. Animal models, especially mouse and zebrafish, have been especially helpful in elucidating such pathomechanisms associated with the congenital myopathies and provide models in which future therapies can be investigated.
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Affiliation(s)
- Jessica R Nance
- Department of Neurology, Children's National Medical Center, Washington, DC 20010, USA
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137
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Myotubularin phosphoinositide phosphatases: cellular functions and disease pathophysiology. Trends Mol Med 2012; 18:317-27. [DOI: 10.1016/j.molmed.2012.04.004] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 04/10/2012] [Accepted: 04/12/2012] [Indexed: 11/23/2022]
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138
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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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139
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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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140
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Abstract
Proteins involved in membrane remodeling play an essential role in a plethora of cell functions including endocytosis and intracellular transport. Defects in several of them lead to human diseases. Myotubularins, amphiphysins, and dynamins are all proteins implicated in membrane trafficking and/or remodeling. Mutations in myotubularin, amphiphysin 2 (BIN1), and dynamin 2 lead to different forms of centronuclear myopathy, while mutations in myotubularin-related proteins cause Charcot-Marie-Tooth neuropathies. In addition to centronuclear myopathy, dynamin 2 is also mutated in a dominant form of Charcot-Marie-Tooth neuropathy. While several proteins from these different families are implicated in similar diseases, mutations in close homologues or in the same protein in the case of dynamin 2 lead to diseases affecting different tissues. This suggests (1) a common molecular pathway underlying these different neuromuscular diseases, and (2) tissue-specific regulation of these proteins. This review discusses the pathophysiology of the related neuromuscular diseases on the basis of animal models developed for proteins of the myotubularin, amphiphysin, and dynamin families. A better understanding of the common mechanisms between these neuromuscular disorders will lead to more specific health care and therapeutic approaches.
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141
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Tronchère H, Bolino A, Laporte J, Payrastre B. Myotubularins and associated neuromuscular diseases. ACTA ACUST UNITED AC 2012. [DOI: 10.2217/clp.12.7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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142
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Dowling JJ, Arbogast S, Hur J, Nelson DD, McEvoy A, Waugh T, Marty I, Lunardi J, Brooks SV, Kuwada JY, Ferreiro A. Oxidative stress and successful antioxidant treatment in models of RYR1-related myopathy. ACTA ACUST UNITED AC 2012; 135:1115-27. [PMID: 22418739 DOI: 10.1093/brain/aws036] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The skeletal muscle ryanodine receptor is an essential component of the excitation-contraction coupling apparatus. Mutations in RYR1 are associated with several congenital myopathies (termed RYR1-related myopathies) that are the most common non-dystrophic muscle diseases of childhood. Currently, no treatments exist for these disorders. Although the primary pathogenic abnormality involves defective excitation-contraction coupling, other abnormalities likely play a role in disease pathogenesis. In an effort to discover novel pathogenic mechanisms, we analysed two complementary models of RYR1-related myopathies, the relatively relaxed zebrafish and cultured myotubes from patients with RYR1-related myopathies. Expression array analysis in the zebrafish disclosed significant abnormalities in pathways associated with cellular stress. Subsequent studies focused on oxidative stress in relatively relaxed zebrafish and RYR1-related myopathy myotubes and demonstrated increased oxidant activity, the presence of oxidative stress markers, excessive production of oxidants by mitochondria and diminished survival under oxidant conditions. Exposure to the antioxidant N-acetylcysteine reduced oxidative stress and improved survival in the RYR1-related myopathies human myotubes ex vivo and led to significant restoration of aspects of muscle function in the relatively relaxed zebrafish, thereby confirming its efficacy in vivo. We conclude that oxidative stress is an important pathophysiological mechanism in RYR1-related myopathies and that N-acetylcysteine is a successful treatment modality ex vivo and in a vertebrate disease model. We propose that N-acetylcysteine represents the first potential therapeutic strategy for these debilitating muscle diseases.
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Affiliation(s)
- James J Dowling
- Department of Paediatrics, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA.
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143
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Sakowski SA, Lunn JS, Busta AS, Palmer M, Dowling JJ, Feldman EL. A novel approach to study motor neurons from zebrafish embryos and larvae in culture. J Neurosci Methods 2012; 205:277-82. [PMID: 22285259 DOI: 10.1016/j.jneumeth.2012.01.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 01/11/2012] [Accepted: 01/11/2012] [Indexed: 12/27/2022]
Abstract
Zebrafish are becoming increasingly popular models for examining the mechanisms of and treatments for neurological diseases. The available methods and technology to examine disease processes in vivo are increasing, however, detailed observations of subcellular structures and processes are complex in whole organisms. To address this need, we developed a primary motor neuron (MN) culture technique for utilization with zebrafish neurological disease models. Our protocol enables the culturing of cells from embryos older than 24h post-fertilization, at points after MN axonal development and outgrowth begins, which enables MN axons to develop in vivo in the context of the normal endogenous cues of the model organism, while also providing the accessibility of an in vitro system. When utilized with the increasing number of genetically modified or transgenic models of neurological diseases, this approach provides a novel tool for the examination of cellular and subcellular disease mechanisms, and offers a new platform for therapeutic discoveries in zebrafish.
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144
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Jungbluth H, Dowling JJ, Ferreiro A, Muntoni F. 182nd ENMC International Workshop: RYR1-related myopathies, 15-17th April 2011, Naarden, The Netherlands. Neuromuscul Disord 2012; 22:453-62. [PMID: 22226685 DOI: 10.1016/j.nmd.2011.12.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 12/04/2011] [Indexed: 11/15/2022]
Affiliation(s)
- Heinz Jungbluth
- Clinical Neuroscience Division, IOP, King's College, London, United Kingdom.
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145
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Abstract
The level and turnover of phosphoinositides (PIs) are tightly controlled by a large set of PI-specific enzymes (PI kinases and phosphatases). Mammalian PI phosphatases are conserved through evolution and among this large family the dual-specificity phosphatase (PTP/DSP) are metal-independent enzymes displaying the amino acid signature Cys-X5-Arg-Thr/Ser (CX5RT/S) in their active site. Such catalytic site characterizes the myotubularin 3-phosphatases that dephosphorylate PtdIns3P and PtdIns(3,5)P₂ and produce PtdIns5P. Substrates of myotubularins have been implicated in endocytosis and membrane trafficking while PtdIns5P may have a role in signal transduction. As a paradox, 6 of the 14 members of the myotubularin family lack enzymatic activity and are considered as dead phosphatases. Several myotubularins have been genetically linked to human diseases: MTM1 is mutated in the congenital myopathy X-linked centronuclear or myotubular myopathy (XLCNM) and MTMR14 (JUMPY) has been linked to an autosomal form of such disease, while MTMR2 and MTMR13 are mutated in Charcot-Marie-Tooth (CMT) neuropathies. Furthermore, recent evidences from genetic association studies revealed that several other myotubularins could be associated to chronic disorders such as cancer and obesity, highlighting their importance for human health. Here, we discuss cellular and physiological roles of myotubularins and their implication in human diseases, and we present potential pathological mechanisms affecting specific tissues in myotubularin-associated diseases.
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146
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Davies EM, Sheffield DA, Tibarewal P, Fedele CG, Mitchell CA, Leslie NR. The PTEN and Myotubularin phosphoinositide 3-phosphatases: linking lipid signalling to human disease. Subcell Biochem 2012; 58:281-336. [PMID: 22403079 DOI: 10.1007/978-94-007-3012-0_8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Two classes of lipid phosphatases selectively dephosphorylate the 3 position of the inositol ring of phosphoinositide signaling molecules: the PTEN and the Myotubularin families. PTEN dephosphorylates PtdIns(3,4,5)P(3), acting in direct opposition to the Class I PI3K enzymes in the regulation of cell growth, proliferation and polarity and is an important tumor suppressor. Although there are several PTEN-related proteins encoded by the human genome, none of these appear to fulfill the same functions. In contrast, the Myotubularins dephosphorylate both PtdIns(3)P and PtdIns(3,5)P(2), making them antagonists of the Class II and Class III PI 3-kinases and regulators of membrane traffic. Both phosphatase groups were originally identified through their causal mutation in human disease. Mutations in specific myotubularins result in myotubular myopathy and Charcot-Marie-Tooth peripheral neuropathy; and loss of PTEN function through mutation and other mechanisms is evident in as many as a third of all human tumors. This chapter will discuss these two classes of phosphatases, covering what is known about their biochemistry, their functions at the cellular and whole body level and their influence on human health.
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Affiliation(s)
- Elizabeth M Davies
- Division of Cell Signalling and Immunology, Wellcome Trust Biocentre, College of Life Sciences, University of Dundee, Dow Street, DD1 5EH, Dundee, Scotland, United Kingdom,
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147
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Hnia K, Kretz C, Amoasii L, Böhm J, Liu X, Messaddeq N, Qu CK, Laporte J. Primary T-tubule and autophagy defects in the phosphoinositide phosphatase Jumpy/MTMR14 knockout mice muscle. Adv Biol Regul 2012; 52:98-107. [PMID: 21930146 DOI: 10.1016/j.advenzreg.2011.09.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 09/06/2011] [Indexed: 05/31/2023]
Affiliation(s)
- Karim Hnia
- Department of Translational Medicine and Neurogenetics, IGBMC (Institut de Génétique et de Biologie Moléculaire et Cellulaire), 1, rue Laurent Fries, BP10142, 67404 Illkirch, France
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148
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Establishing clinical end points of respiratory function in large animals for clinical translation. Phys Med Rehabil Clin N Am 2011; 23:75-94, xi. [PMID: 22239876 DOI: 10.1016/j.pmr.2011.11.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Respiratory dysfunction due progressive weakness of the respiratory muscles, particularly the diaphragm, is a major cause of death in the neuromuscular disease (NMD) X-linked myotubular myopathy (XLMTM). Methods of respiratory assessment in patients are often difficult, especially in those who are mechanically ventilated. The naturally occuring XLMTM dog model exhibits a phenotype similar to that in patients and can be used to determine quantitative descriptions of dysfunction as clinical endpoints for treatment and the development of new therapies. In experiments using respiratory impedance plethysmography (RIP), XLMTM dogs challenged with the respiratory stimulant doxapram displayed significant changes indicative of diaphragmatic weakness.
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149
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Telfer WR, Nelson DD, Waugh T, Brooks SV, Dowling JJ. Neb: a zebrafish model of nemaline myopathy due to nebulin mutation. Dis Model Mech 2011; 5:389-96. [PMID: 22159874 PMCID: PMC3339832 DOI: 10.1242/dmm.008631] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Nemaline myopathy is one of the most common and severe non-dystrophic muscle diseases of childhood. Patients typically present in infancy with hypotonia, weakness, delayed motor development, and bulbar and respiratory difficulties. Mutations in six different genes are associated with nemaline myopathy, with nebulin mutations being the most common. No treatments or disease-modifying therapies have been identified for this disease. One of the major barriers to treatment development is the lack of models amenable to rapid and coordinated testing of potential therapeutic strategies. To overcome this barrier, we have characterized the first zebrafish model of nemaline myopathy. This model, termed neb, harbors a recessive mutation in the nebulin gene that results in decreased Nebulin protein levels, a severe motor phenotype and premature lethality. In addition to impaired motor function, neb zebrafish exhibit many of the features associated with human nemaline myopathy. These include impaired force generation, altered thin filament length and the presence of specific histopathological changes, including the formation of nemaline bodies. In summary, neb zebrafish mirror the genetic, clinical and pathological aspects of nemaline myopathy due to NEB mutation, and thus are an excellent model for future therapy development for this devastating disorder.
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Affiliation(s)
- William R Telfer
- Departments of Pediatrics, University of Michigan Medical Center, Ann Arbor, MI 48109-2200, USA
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150
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