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Tan RL, Sciandra F, Hübner W, Bozzi M, Reimann J, Schoch S, Brancaccio A, Blaess S. The missense mutation C667F in murine β-dystroglycan causes embryonic lethality, myopathy and blood-brain barrier destabilization. Dis Model Mech 2024; 17:dmm050594. [PMID: 38616731 PMCID: PMC11212641 DOI: 10.1242/dmm.050594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 04/08/2024] [Indexed: 04/16/2024] Open
Abstract
Dystroglycan (DG) is an extracellular matrix receptor consisting of an α- and a β-DG subunit encoded by the DAG1 gene. The homozygous mutation (c.2006G>T, p.Cys669Phe) in β-DG causes muscle-eye-brain disease with multicystic leukodystrophy in humans. In a mouse model of this primary dystroglycanopathy, approximately two-thirds of homozygous embryos fail to develop to term. Mutant mice that are born undergo a normal postnatal development but show a late-onset myopathy with partially penetrant histopathological changes and an impaired performance on an activity wheel. Their brains and eyes are structurally normal, but the localization of mutant β-DG is altered in the glial perivascular end-feet, resulting in a perturbed protein composition of the blood-brain and blood-retina barrier. In addition, α- and β-DG protein levels are significantly reduced in muscle and brain of mutant mice. Owing to the partially penetrant developmental phenotype of the C669F β-DG mice, they represent a novel and highly valuable mouse model with which to study the molecular effects of β-DG functional alterations both during embryogenesis and in mature muscle, brain and eye, and to gain insight into the pathogenesis of primary dystroglycanopathies.
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Affiliation(s)
- Rui Lois Tan
- Neurodevelopmental Genetics, Institute of Reconstructive Neurobiology, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Francesca Sciandra
- Institute of Chemical Sciences and Technologies ‘Giulio Natta’ (SCITEC)-CNR, 00168 Rome, Italy
| | - Wolfgang Hübner
- Biomolecular Photonics, Faculty of Physics, Bielefeld University, 33615 Bielefeld, Germany
| | - Manuela Bozzi
- Institute of Chemical Sciences and Technologies ‘Giulio Natta’ (SCITEC)-CNR, 00168 Rome, Italy
- Dipartimento di Scienze Biotecnologiche di Base, Cliniche Intensivologiche e Perioperatorie. Sezione di Biochimica. Università Cattolica del Sacro Cuore di Roma, 00168 Rome, Italy
| | - Jens Reimann
- Department of Neurology, Neuromuscular Diseases Section, University Hospital Bonn, 53127 Bonn, Germany
| | - Susanne Schoch
- Synaptic Neuroscience Team, Institute of Neuropathology, Medical Faculty, University of Bonn, 53127 Bonn, Germany
| | - Andrea Brancaccio
- Institute of Chemical Sciences and Technologies ‘Giulio Natta’ (SCITEC)-CNR, 00168 Rome, Italy
- School of Biochemistry, University Walk, University of Bristol, Bristol BS8 1TD, UK
| | - Sandra Blaess
- Neurodevelopmental Genetics, Institute of Reconstructive Neurobiology, Medical Faculty, University of Bonn, 53127 Bonn, Germany
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2
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Koff M, Monagas-Valentin P, Novikov B, Chandel I, Panin V. Protein O-mannosylation: one sugar, several pathways, many functions. Glycobiology 2023; 33:911-926. [PMID: 37565810 PMCID: PMC10859634 DOI: 10.1093/glycob/cwad067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 07/23/2023] [Accepted: 07/31/2023] [Indexed: 08/12/2023] Open
Abstract
Recent research has unveiled numerous important functions of protein glycosylation in development, homeostasis, and diseases. A type of glycosylation taking the center stage is protein O-mannosylation, a posttranslational modification conserved in a wide range of organisms, from yeast to humans. In animals, protein O-mannosylation plays a crucial role in the nervous system, whereas protein O-mannosylation defects cause severe neurological abnormalities and congenital muscular dystrophies. However, the molecular and cellular mechanisms underlying protein O-mannosylation functions and biosynthesis remain not well understood. This review outlines recent studies on protein O-mannosylation while focusing on the functions in the nervous system, summarizes the current knowledge about protein O-mannosylation biosynthesis, and discusses the pathologies associated with protein O-mannosylation defects. The evolutionary perspective revealed by studies in the Drosophila model system are also highlighted. Finally, the review touches upon important knowledge gaps in the field and discusses critical questions for future research on the molecular and cellular mechanisms associated with protein O-mannosylation functions.
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Affiliation(s)
- Melissa Koff
- Department of Biochemistry and Biophysics, AgriLife Research, Texas A&M University, College Station, College Station, TX 77843, United States
| | - Pedro Monagas-Valentin
- Department of Biochemistry and Biophysics, AgriLife Research, Texas A&M University, College Station, College Station, TX 77843, United States
| | - Boris Novikov
- Department of Biochemistry and Biophysics, AgriLife Research, Texas A&M University, College Station, College Station, TX 77843, United States
| | - Ishita Chandel
- Department of Biochemistry and Biophysics, AgriLife Research, Texas A&M University, College Station, College Station, TX 77843, United States
| | - Vladislav Panin
- Department of Biochemistry and Biophysics, AgriLife Research, Texas A&M University, College Station, College Station, TX 77843, United States
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3
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Esapa CT, McIlhinney RAJ, Waite AJ, Benson MA, Mirzayan J, Piko H, Herczegfalvi Á, Horvath R, Karcagi V, Walter MC, Lochmüller H, Rizkallah PJ, Lu QL, Blake DJ. Misfolding of fukutin-related protein (FKRP) variants in congenital and limb girdle muscular dystrophies. Front Mol Biosci 2023; 10:1279700. [PMID: 38161385 PMCID: PMC10755465 DOI: 10.3389/fmolb.2023.1279700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 11/16/2023] [Indexed: 01/03/2024] Open
Abstract
Fukutin-related protein (FKRP, MIM ID 606596) variants cause a range of muscular dystrophies associated with hypo-glycosylation of the matrix receptor, α-dystroglycan. These disorders are almost exclusively caused by homozygous or compound heterozygous missense variants in the FKRP gene that encodes a ribitol phosphotransferase. To understand how seemingly diverse FKRP missense mutations may contribute to disease, we examined the synthesis, intracellular dynamics, and structural consequences of a panel of missense mutations that encompass the disease spectrum. Under non-reducing electrophoresis conditions, wild type FKRP appears to be monomeric whereas disease-causing FKRP mutants migrate as high molecular weight, disulfide-bonded aggregates. These results were recapitulated using cysteine-scanning mutagenesis suggesting that abnormal disulfide bonding may perturb FKRP folding. Using fluorescence recovery after photobleaching, we found that the intracellular mobility of most FKRP mutants in ATP-depleted cells is dramatically reduced but can, in most cases, be rescued with reducing agents. Mass spectrometry showed that wild type and mutant FKRP differentially associate with several endoplasmic reticulum (ER)-resident chaperones. Finally, structural modelling revealed that disease-associated FKRP missense variants affected the local environment of the protein in small but significant ways. These data demonstrate that protein misfolding contributes to the molecular pathophysiology of FKRP-deficient muscular dystrophies and suggest that molecules that rescue this folding defect could be used to treat these disorders.
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Affiliation(s)
| | | | - Adrian J. Waite
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | | | - Jasmin Mirzayan
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Henriett Piko
- Department of Internal Medicine and Oncology, Semmelweis University, Budapest, Hungary
| | - Ágnes Herczegfalvi
- Semmelweis University Pediatric Center Tűzoltó Street Unit, Budapest, Hungary
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Veronika Karcagi
- National Institute of Environmental Health, Department of Molecular Genetics and Diagnostics, Istenhegyi Genetic Diagnostic Centre, Budapest, Hungary
| | - Maggie C. Walter
- Friedrich-Baur-Institute at the Department of Neurology, University Hospital, Munich, Germany
| | - Hanns Lochmüller
- Children’s Hospital of Eastern Ontario Research Institute, Division of Neurology, Department of Medicine, The Ottawa Hospital, and Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
| | - Pierre J. Rizkallah
- Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Qi L. Lu
- McColl-Lockwood Laboratory for Muscular Dystrophy Research, Carolinas Medical Center, Charlotte, United States
| | - Derek J. Blake
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
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4
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Skeletal Muscle Cells Derived from Induced Pluripotent Stem Cells: A Platform for Limb Girdle Muscular Dystrophies. Biomedicines 2022; 10:biomedicines10061428. [PMID: 35740450 PMCID: PMC9220148 DOI: 10.3390/biomedicines10061428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 05/27/2022] [Accepted: 06/09/2022] [Indexed: 11/16/2022] Open
Abstract
Limb girdle muscular dystrophies (LGMD), caused by mutations in 29 different genes, are the fourth most prevalent group of genetic muscle diseases. Although the link between LGMD and its genetic origins has been determined, LGMD still represent an unmet medical need. Here, we describe a platform for modeling LGMD based on the use of human induced pluripotent stem cells (hiPSC). Thanks to the self-renewing and pluripotency properties of hiPSC, this platform provides a renewable and an alternative source of skeletal muscle cells (skMC) to primary, immortalized, or overexpressing cells. We report that skMC derived from hiPSC express the majority of the genes and proteins that cause LGMD. As a proof of concept, we demonstrate the importance of this cellular model for studying LGMDR9 by evaluating disease-specific phenotypes in skMC derived from hiPSC obtained from four patients.
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5
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Boyd A, Montandon M, Wood AJ, Currie PD. FKRP directed fibronectin glycosylation: A novel mechanism giving insights into muscular dystrophies? Bioessays 2022; 44:e2100270. [PMID: 35229908 DOI: 10.1002/bies.202100270] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 02/12/2022] [Accepted: 02/16/2022] [Indexed: 12/15/2022]
Abstract
The recently uncovered role of Fukutin-related protein (FKRP) in fibronectin glycosylation has challenged our understanding of the basis of disease pathogenesis in the muscular dystrophies. FKRP is a Golgi-resident glycosyltransferase implicated in a broad spectrum of muscular dystrophy (MD) pathologies that are not fully attributable to the well-described α-Dystroglycan hypoglycosylation. By revealing a new role for FKRP in the glycosylation of fibronectin, a modification critical for the development of the muscle basement membrane (MBM) and its associated muscle linkages, new possibilities for understanding clinical phenotype arise. This modification involves an interaction between FKRP and myosin-10, a protein involved in the Golgi organization and function. These observations suggest a FKRP nexus exists that controls two critical aspects to muscle fibre integrity, both fibre stability at the MBM and its elastic properties. This review explores the new potential disease axis in the context of our current knowledge of muscular dystrophies.
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Affiliation(s)
- Andrew Boyd
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Margo Montandon
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Alasdair J Wood
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia
| | - Peter D Currie
- Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia.,EMBL Australia, Monash University, Clayton, Victoria, Australia
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6
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Kanagawa M. Dystroglycanopathy: From Elucidation of Molecular and Pathological Mechanisms to Development of Treatment Methods. Int J Mol Sci 2021; 22:ijms222313162. [PMID: 34884967 PMCID: PMC8658603 DOI: 10.3390/ijms222313162] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 12/02/2021] [Accepted: 12/03/2021] [Indexed: 01/13/2023] Open
Abstract
Dystroglycanopathy is a collective term referring to muscular dystrophies with abnormal glycosylation of dystroglycan. At least 18 causative genes of dystroglycanopathy have been identified, and its clinical symptoms are diverse, ranging from severe congenital to adult-onset limb-girdle types. Moreover, some cases are associated with symptoms involving the central nervous system. In the 2010s, the structure of sugar chains involved in the onset of dystroglycanopathy and the functions of its causative gene products began to be identified as if they were filling the missing pieces of a jigsaw puzzle. In parallel with these discoveries, various dystroglycanopathy model mice had been created, which led to the elucidation of its pathological mechanisms. Then, treatment strategies based on the molecular basis of glycosylation began to be proposed after the latter half of the 2010s. This review briefly explains the sugar chain structure of dystroglycan and the functions of the causative gene products of dystroglycanopathy, followed by introducing the pathological mechanisms involved as revealed from analyses of dystroglycanopathy model mice. Finally, potential therapeutic approaches based on the pathological mechanisms involved are discussed.
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Affiliation(s)
- Motoi Kanagawa
- Department of Cell Biology and Molecular Medicine, Graduate School of Medicine, Ehime University, 454 Shitsukawa, Toon 791-0295, Ehime, Japan
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7
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Brown SC, Fernandez-Fuente M, Muntoni F, Vissing J. Phenotypic Spectrum of α-Dystroglycanopathies Associated With the c.919T>a Variant in the FKRP Gene in Humans and Mice. J Neuropathol Exp Neurol 2021; 79:1257-1264. [PMID: 33051673 DOI: 10.1093/jnen/nlaa120] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mutations in the fukutin-related protein gene, FKRP, are the most frequent single cause of α-dystroglycanopathy. Rare FKRP mutations are clinically not well characterized. Here, we review the phenotype associated with the rare c.919T>A mutation in FKRP in humans and mice. We describe clinical and paraclinical findings in 6 patients, 2 homozygous, and 4-compound heterozygous for c.919T>A, and compare findings with a mouse model we generated, which is homozygous for the same mutation. In patients, the mutation at the homozygous state is associated with a severe congenital muscular dystrophy phenotype invariably characterized by severe multisystem disease and early death. Compound heterozygous patients have a severe limb-girdle muscular dystrophy phenotype, loss of ambulation before age 20 and respiratory insufficiency. In contrast, mice homozygous for the same mutation show no symptoms or signs of muscle disease. Evidence therefore defines the FKRP c.919T>A as a very severe mutation in humans. The huge discrepancy between phenotypes in humans and mice suggests that differences in protein folding/processing exist between human and mouse Fkrp. This emphasizes the need for more detailed structural analyses of FKRP and shows the challenges of developing appropriate animal models of dystroglycanopathies that mimic the disease course in humans.
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Affiliation(s)
- Susan C Brown
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | | | - Francesco Muntoni
- Dubowitz Neuromuscular Centre, UCL Great Ormond Street Institute of Child Health & Great Ormond Street Hospital, London, UK and National Institute for Health Research Great Ormond Street Hospital Biomedical Research Centre, UCL Great Ormond Street Institute of Child Health, London
| | - John Vissing
- Copenhagen Neuromuscular Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
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Ferent J, Zaidi D, Francis F. Extracellular Control of Radial Glia Proliferation and Scaffolding During Cortical Development and Pathology. Front Cell Dev Biol 2020; 8:578341. [PMID: 33178693 PMCID: PMC7596222 DOI: 10.3389/fcell.2020.578341] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 09/08/2020] [Indexed: 01/14/2023] Open
Abstract
During the development of the cortex, newly generated neurons migrate long-distances in the expanding tissue to reach their final positions. Pyramidal neurons are produced from dorsal progenitors, e.g., radial glia (RGs) in the ventricular zone, and then migrate along RG processes basally toward the cortex. These neurons are hence dependent upon RG extensions to support their migration from apical to basal regions. Several studies have investigated how intracellular determinants are required for RG polarity and subsequent formation and maintenance of their processes. Fewer studies have identified the influence of the extracellular environment on this architecture. This review will focus on extracellular factors which influence RG morphology and pyramidal neuronal migration during normal development and their perturbations in pathology. During cortical development, RGs are present in different strategic positions: apical RGs (aRGs) have their cell bodies located in the ventricular zone with an apical process contacting the ventricle, while they also have a basal process extending radially to reach the pial surface of the cortex. This particular conformation allows aRGs to be exposed to long range and short range signaling cues, whereas basal RGs (bRGs, also known as outer RGs, oRGs) have their cell bodies located throughout the cortical wall, limiting their access to ventricular factors. Long range signals impacting aRGs include secreted molecules present in the embryonic cerebrospinal fluid (e.g., Neuregulin, EGF, FGF, Wnt, BMP). Secreted molecules also contribute to the extracellular matrix (fibronectin, laminin, reelin). Classical short range factors include cell to cell signaling, adhesion molecules and mechano-transduction mechanisms (e.g., TAG1, Notch, cadherins, mechanical tension). Changes in one or several of these components influencing the RG extracellular environment can disrupt the development or maintenance of RG architecture on which neuronal migration relies, leading to a range of cortical malformations. First, we will detail the known long range signaling cues impacting RG. Then, we will review how short range cell contacts are also important to instruct the RG framework. Understanding how RG processes are structured by their environment to maintain and support radial migration is a critical part of the investigation of neurodevelopmental disorders.
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Affiliation(s)
- Julien Ferent
- Inserm, U 1270, Paris, France.,Sorbonne University, UMR-S 1270, IFM, Paris, France.,Institut du Fer á Moulin, Paris, France
| | - Donia Zaidi
- Inserm, U 1270, Paris, France.,Sorbonne University, UMR-S 1270, IFM, Paris, France.,Institut du Fer á Moulin, Paris, France
| | - Fiona Francis
- Inserm, U 1270, Paris, France.,Sorbonne University, UMR-S 1270, IFM, Paris, France.,Institut du Fer á Moulin, Paris, France
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9
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Vaubourg C, Gicquel E, Richard I, Lostal W, Bellec J. Minimal Consequences of CMAH and DBA/2 Backgrounds on a FKRP Deficient Model. J Neuromuscul Dis 2020; 8:785-793. [PMID: 32925084 DOI: 10.3233/jnd-200487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Muscular dystrophies (MD) are a large group of genetic diseases characterized by a progressive loss of muscle. The Latent TGFβ Binding Protein 4 (LTBP4) in the DBA/2 background and the Cytidine Monophosphate-sialic Acid Hydroxylase (CMAH) proteins were previously identified as genetic modifiers in severe MD. OBJECTIVE We investigated whether these modifiers could also influence a mild phenotype such as the one observed in a mouse model of Limb-Girdle MD2I (LGMD2I). METHODS The FKRPL276I mouse model was backcrossed onto the DBA/2 background, and in separate experiments the Cmah gene was inactivated in FKRPL276I mice by crossing with a Cmah-/- mouse and selecting the double-mutants. The mdx mouse was used as control for these two genome modifications. Consequences at the histological level as well as quantification of expression level by RT-qPCR of genes relevant for muscular dystrophy were then performed. RESULTS We observed minimal to no effect of the DBA/2 background on the mild FKRPL276I mouse phenotype, while this same background was previously shown to increase inflammation and fibrosis in the mdx mouse. Similarly, the Cmah-/- deletion had no observable effect on the FKRPL276I mouse phenotype whereas it was seen to increase features of regeneration in mdx mice. CONCLUSIONS These modifiers were not observed to impact the severity of the presentation of the mild FKRPL276I model. An interesting association of the CMAH modifier with the regeneration process in the mdx model was seen and sheds new light on the influence of this protein on the dystrophic phenotype.
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Affiliation(s)
- Camille Vaubourg
- Généthon, Evry, France.,Université Paris-Saclay, Univ Evry, Inserm, Généthon, Integrare research unit UMR_S951, 91000, Evry, France
| | - Evelyne Gicquel
- Généthon, Evry, France.,Université Paris-Saclay, Univ Evry, Inserm, Généthon, Integrare research unit UMR_S951, 91000, Evry, France
| | - Isabelle Richard
- Généthon, Evry, France.,Université Paris-Saclay, Univ Evry, Inserm, Généthon, Integrare research unit UMR_S951, 91000, Evry, France
| | - William Lostal
- Généthon, Evry, France.,Université Paris-Saclay, Univ Evry, Inserm, Généthon, Integrare research unit UMR_S951, 91000, Evry, France
| | - Jessica Bellec
- Généthon, Evry, France.,Université Paris-Saclay, Univ Evry, Inserm, Généthon, Integrare research unit UMR_S951, 91000, Evry, France
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10
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Kim J, Lana B, Torelli S, Ryan D, Catapano F, Ala P, Luft C, Stevens E, Konstantinidis E, Louzada S, Fu B, Paredes‐Redondo A, Chan AWE, Yang F, Stemple DL, Liu P, Ketteler R, Selwood DL, Muntoni F, Lin Y. A new patient-derived iPSC model for dystroglycanopathies validates a compound that increases glycosylation of α-dystroglycan. EMBO Rep 2019; 20:e47967. [PMID: 31566294 PMCID: PMC6832011 DOI: 10.15252/embr.201947967] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 08/24/2019] [Accepted: 08/29/2019] [Indexed: 12/24/2022] Open
Abstract
Dystroglycan, an extracellular matrix receptor, has essential functions in various tissues. Loss of α-dystroglycan-laminin interaction due to defective glycosylation of α-dystroglycan underlies a group of congenital muscular dystrophies often associated with brain malformations, referred to as dystroglycanopathies. The lack of isogenic human dystroglycanopathy cell models has limited our ability to test potential drugs in a human- and neural-specific context. Here, we generated induced pluripotent stem cells (iPSCs) from a severe dystroglycanopathy patient with homozygous FKRP (fukutin-related protein gene) mutation. We showed that CRISPR/Cas9-mediated gene correction of FKRP restored glycosylation of α-dystroglycan in iPSC-derived cortical neurons, whereas targeted gene mutation of FKRP in wild-type cells disrupted this glycosylation. In parallel, we screened 31,954 small molecule compounds using a mouse myoblast line for increased glycosylation of α-dystroglycan. Using human FKRP-iPSC-derived neural cells for hit validation, we demonstrated that compound 4-(4-bromophenyl)-6-ethylsulfanyl-2-oxo-3,4-dihydro-1H-pyridine-5-carbonitrile (4BPPNit) significantly augmented glycosylation of α-dystroglycan, in part through upregulation of LARGE1 glycosyltransferase gene expression. Together, isogenic human iPSC-derived cells represent a valuable platform for facilitating dystroglycanopathy drug discovery and therapeutic development.
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Affiliation(s)
- Jihee Kim
- Centre for Genomics and Child HealthBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
- Stem Cell LaboratoryNational Bowel Research CentreBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
| | - Beatrice Lana
- Centre for Genomics and Child HealthBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
- Stem Cell LaboratoryNational Bowel Research CentreBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
| | - Silvia Torelli
- UCL Great Ormond Street Institute of Child HealthLondonUK
| | - David Ryan
- Wellcome Sanger InstituteHinxtonCambridgeUK
| | | | - Pierpaolo Ala
- UCL Great Ormond Street Institute of Child HealthLondonUK
| | - Christin Luft
- MRC Laboratory for Molecular Cell BiologyUniversity College LondonLondonUK
| | | | - Evangelos Konstantinidis
- Centre for Genomics and Child HealthBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
- Stem Cell LaboratoryNational Bowel Research CentreBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
| | | | - Beiyuan Fu
- Wellcome Sanger InstituteHinxtonCambridgeUK
| | - Amaia Paredes‐Redondo
- Centre for Genomics and Child HealthBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
- Stem Cell LaboratoryNational Bowel Research CentreBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
| | - AW Edith Chan
- The Wolfson Institute for Biomedical ResearchUniversity College LondonLondonUK
| | | | | | - Pentao Liu
- Wellcome Sanger InstituteHinxtonCambridgeUK
| | - Robin Ketteler
- MRC Laboratory for Molecular Cell BiologyUniversity College LondonLondonUK
| | - David L Selwood
- The Wolfson Institute for Biomedical ResearchUniversity College LondonLondonUK
| | - Francesco Muntoni
- UCL Great Ormond Street Institute of Child HealthLondonUK
- NIHR Biomedical Research Centre at Great Ormond Street HospitalLondonUK
| | - Yung‐Yao Lin
- Centre for Genomics and Child HealthBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
- Stem Cell LaboratoryNational Bowel Research CentreBlizard Institute, Barts and the London School of Medicine and DentistryQueen Mary University of LondonLondonUK
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11
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Bailey EC, Alrowaished SS, Kilroy EA, Crooks ES, Drinkert DM, Karunasiri CM, Belanger JJ, Khalil A, Kelley JB, Henry CA. NAD+ improves neuromuscular development in a zebrafish model of FKRP-associated dystroglycanopathy. Skelet Muscle 2019; 9:21. [PMID: 31391079 PMCID: PMC6685180 DOI: 10.1186/s13395-019-0206-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 07/17/2019] [Indexed: 01/26/2023] Open
Abstract
Background Secondary dystroglycanopathies are muscular dystrophies that result from mutations in genes that participate in Dystroglycan glycosylation. Glycosylation of Dystroglycan is essential for muscle fibers to adhere to the muscle extracellular matrix (myomatrix). Although the myomatrix is disrupted in a number of secondary dystroglycanopathies, it is unknown whether improving the myomatrix is beneficial for these conditions. We previously determined that either NAD+ supplementation or overexpression of Paxillin are sufficient to improve muscle structure and the myomatrix in a zebrafish model of primary dystroglycanopathy. Here, we investigate how these modulations affect neuromuscular phenotypes in zebrafish fukutin-related protein (fkrp) morphants modeling FKRP-associated secondary dystroglycanopathy. Results We found that NAD+ supplementation prior to muscle development improved muscle structure, myotendinous junction structure, and muscle function in fkrp morphants. However, Paxillin overexpression did not improve any of these parameters in fkrp morphants. As movement also requires neuromuscular junction formation, we examined early neuromuscular junction development in fkrp morphants. The length of neuromuscular junctions was disrupted in fkrp morphants. NAD+ supplementation prior to neuromuscular junction development improved length. We investigated NMJ formation in dystroglycan (dag1) morphants and found that although NMJ morphology is disrupted in dag1 morphants, NAD+ is not sufficient to improve NMJ morphology in dag1 morphants. Ubiquitous overexpression of Fkrp rescued the fkrp morphant phenotype but muscle-specific overexpression only improved myotendinous junction structure. Conclusions These data indicate that Fkrp plays an early and essential role in muscle, myotendinous junction, and neuromuscular junction development. These data also indicate that, at least in the zebrafish model, FKRP-associated dystroglycanopathy does not exactly phenocopy DG-deficiency. Paxillin overexpression improves muscle structure in dag1 morphants but not fkrp morphants. In contrast, NAD+ supplementation improves NMJ morphology in fkrp morphants but not dag1 morphants. Finally, these data show that muscle-specific expression of Fkrp is insufficient to rescue muscle development and homeostasis. Electronic supplementary material The online version of this article (10.1186/s13395-019-0206-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Erin C Bailey
- School of Biology and Ecology, University of Maine, Orono, ME, 04469, USA.,Graduate School of Biomedical Sciences and Engineering, University of Maine, 217 Hitchner Hall, Orono, ME, 04469, USA
| | | | - Elisabeth A Kilroy
- Graduate School of Biomedical Sciences and Engineering, University of Maine, 217 Hitchner Hall, Orono, ME, 04469, USA
| | - Emma S Crooks
- School of Biology and Ecology, University of Maine, Orono, ME, 04469, USA
| | - Daisy M Drinkert
- Molecular and Biomedical Sciences, University of Maine, Orono, ME, 04469, USA
| | - Chaya M Karunasiri
- School of Biology and Ecology, University of Maine, Orono, ME, 04469, USA.,Present Address: Tufts University School of Medicine, Boston, MA, 02111, USA
| | - Joseph J Belanger
- School of Biology and Ecology, University of Maine, Orono, ME, 04469, USA.,Present Address: Lake Erie College of Osteopathic Medicine, Erie, PA, 16509, USA
| | - Andre Khalil
- Chemical and Biomedical Engineering, University of Maine, Orono, ME, 04469, USA.,Graduate School of Biomedical Sciences and Engineering, University of Maine, 217 Hitchner Hall, Orono, ME, 04469, USA
| | - Joshua B Kelley
- Molecular and Biomedical Sciences, University of Maine, Orono, ME, 04469, USA.,Graduate School of Biomedical Sciences and Engineering, University of Maine, 217 Hitchner Hall, Orono, ME, 04469, USA
| | - Clarissa A Henry
- School of Biology and Ecology, University of Maine, Orono, ME, 04469, USA. .,Graduate School of Biomedical Sciences and Engineering, University of Maine, 217 Hitchner Hall, Orono, ME, 04469, USA.
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12
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Brancaccio A. A molecular overview of the primary dystroglycanopathies. J Cell Mol Med 2019; 23:3058-3062. [PMID: 30838779 PMCID: PMC6484290 DOI: 10.1111/jcmm.14218] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 01/22/2019] [Accepted: 01/23/2019] [Indexed: 01/17/2023] Open
Abstract
Dystroglycan is a major non-integrin adhesion complex that connects the cytoskeleton to the surrounding basement membranes, thus providing stability to skeletal muscle. In Vertebrates, hypoglycosylation of α-dystroglycan has been strongly linked to muscular dystrophy phenotypes, some of which also show variable degrees of cognitive impairments, collectively termed dystroglycanopathies. Only a small number of mutations in the dystroglycan gene, leading to the so called primary dystroglycanopathies, has been described so far, as opposed to the ever-growing number of identified secondary or tertiary dystroglycanopathies (caused by genetic abnormalities in glycosyltransferases or in enzymes involved in the synthesis of the carbohydrate building blocks). The few mutations found within the autonomous N-terminal domain of α-dystroglycan seem to destabilise it to different degrees, without influencing the overall folding and targeting of the dystroglycan complex. On the contrary other mutations, some located at the α/β interface of the dystroglycan complex, seem to be able to interfere with its maturation, thus compromising its stability and eventually leading to the intracellular engulfment and/or partial or even total degradation of the dystroglycan uncleaved precursor.
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Affiliation(s)
- Andrea Brancaccio
- School of Biochemistry, University of Bristol, Bristol, UK.,Istituto di Chimica del Riconoscimento Molecolare - CNR c/o Università Cattolica del Sacro Cuore, Roma, Italy
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13
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Francisco R, Pascoal C, Marques-da-Silva D, Morava E, Gole GA, Coman D, Jaeken J, Dos Reis Ferreira V. Keeping an eye on congenital disorders of O-glycosylation: A systematic literature review. J Inherit Metab Dis 2019; 42:29-48. [PMID: 30740740 DOI: 10.1002/jimd.12025] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Congenital disorders of glycosylation (CDG) are a rapidly growing family comprising >100 genetic diseases. Some 25 CDG are pure O-glycosylation defects. Even among this CDG subgroup, phenotypic diversity is broad, ranging from mild to severe poly-organ/system dysfunction. Ophthalmic manifestations are present in 60% of these CDG. The ophthalmic manifestations in N-glycosylation-deficient patients have been described elsewhere. The present review documents the spectrum and incidence of eye disorders in patients with pure O-glycosylation defects with the aim of assisting diagnosis and management and promoting research.
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Affiliation(s)
- Rita Francisco
- UCIBIO, Departamento Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Lisbon, Portugal
- Portuguese Association for CDG, Lisbon, Portugal
- CDG & Allies - Professionals and Patient Associations International Network (CDG & Allies - PPAIN), Lisbon, Portugal
| | - Carlota Pascoal
- UCIBIO, Departamento Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Lisbon, Portugal
- Portuguese Association for CDG, Lisbon, Portugal
- CDG & Allies - Professionals and Patient Associations International Network (CDG & Allies - PPAIN), Lisbon, Portugal
| | - Dorinda Marques-da-Silva
- UCIBIO, Departamento Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Lisbon, Portugal
- Portuguese Association for CDG, Lisbon, Portugal
- CDG & Allies - Professionals and Patient Associations International Network (CDG & Allies - PPAIN), Lisbon, Portugal
| | - Eva Morava
- CDG & Allies - Professionals and Patient Associations International Network (CDG & Allies - PPAIN), Lisbon, Portugal
- Center for Metabolic Disease, KU Leuven, Leuven, Belgium
| | - Glen A Gole
- CDG & Allies - Professionals and Patient Associations International Network (CDG & Allies - PPAIN), Lisbon, Portugal
- Discipline of Paediatrics and Child Health, University of Queensland, Queensland Children's Hospital, Brisbane, Queensland, Australia
| | - David Coman
- CDG & Allies - Professionals and Patient Associations International Network (CDG & Allies - PPAIN), Lisbon, Portugal
- Department of Metabolic Medicine, The Lady Cilento Children's Hospital, Brisbane, Queensland, Australia
| | - Jaak Jaeken
- CDG & Allies - Professionals and Patient Associations International Network (CDG & Allies - PPAIN), Lisbon, Portugal
- Center for Metabolic Disease, KU Leuven, Leuven, Belgium
| | - Vanessa Dos Reis Ferreira
- Portuguese Association for CDG, Lisbon, Portugal
- CDG & Allies - Professionals and Patient Associations International Network (CDG & Allies - PPAIN), Lisbon, Portugal
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14
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Nickolls AR, Bönnemann CG. The roles of dystroglycan in the nervous system: insights from animal models of muscular dystrophy. Dis Model Mech 2018; 11:11/12/dmm035931. [PMID: 30578246 PMCID: PMC6307911 DOI: 10.1242/dmm.035931] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Dystroglycan is a cell membrane protein that binds to the extracellular matrix in a variety of mammalian tissues. The α-subunit of dystroglycan (αDG) is heavily glycosylated, including a special O-mannosyl glycoepitope, relying upon this unique glycosylation to bind its matrix ligands. A distinct group of muscular dystrophies results from specific hypoglycosylation of αDG, and they are frequently associated with central nervous system involvement, ranging from profound brain malformation to intellectual disability without evident morphological defects. There is an expanding literature addressing the function of αDG in the nervous system, with recent reports demonstrating important roles in brain development and in the maintenance of neuronal synapses. Much of these data are derived from an increasingly rich array of experimental animal models. This Review aims to synthesize the information from such diverse models, formulating an up-to-date understanding about the various functions of αDG in neurons and glia of the central and peripheral nervous systems. Where possible, we integrate these data with our knowledge of the human disorders to promote translation from basic mechanistic findings to clinical therapies that take the neural phenotypes into account. Summary: Dystroglycan is a ubiquitous matrix receptor linked to brain and muscle disease. Unraveling the functions of this protein will inform basic and translational research on neural development and muscular dystrophies.
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Affiliation(s)
- Alec R Nickolls
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.,Department of Neuroscience, Brown University, Providence, RI 02912, USA
| | - Carsten G Bönnemann
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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15
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Yu Q, Morales M, Li N, Fritz AG, Ruobing R, Blaeser A, Francois E, Lu QL, Nagaraju K, Spurney CF. Skeletal, cardiac, and respiratory muscle function and histopathology in the P448Lneo- mouse model of FKRP-deficient muscular dystrophy. Skelet Muscle 2018; 8:13. [PMID: 29625576 PMCID: PMC5889611 DOI: 10.1186/s13395-018-0158-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 03/20/2018] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Fukutin-related protein (FKRP) mutations are the most common cause of dystroglycanopathies known to cause both limb girdle and congenital muscular dystrophy. The P448Lneo- mouse model has a knock-in mutation in the FKRP gene and develops skeletal, respiratory, and cardiac muscle disease. METHODS We studied the natural history of the P448Lneo- mouse model over 9 months and the effects of twice weekly treadmill running. Forelimb and hindlimb grip strength (Columbus Instruments) and overall activity (Omnitech Electronics) assessed skeletal muscle function. Echocardiography was performed using VisualSonics Vevo 770 (FujiFilm VisualSonics). Plethysmography was performed using whole body system (ADInstruments). Histological evaluations included quantification of inflammation, fibrosis, central nucleation, and fiber size variation. RESULTS P448Lneo- mice had significantly increased normalized tissue weights compared to controls at 9 months of age for the heart, gastrocnemius, soleus, tibialis anterior, quadriceps, and triceps. There were no significant differences seen in forelimb or hindlimb grip strength or activity monitoring in P448Lneo- mice with or without exercise compared to controls. Skeletal muscles demonstrated increased inflammation, fibrosis, central nucleation, and variation in fiber size compared to controls (p < 0.05) and worsened with exercise. Plethysmography showed significant differences in respiratory rates and decreased tidal and minute volumes in P448Lneo- mice (p < 0.01). There was increased fibrosis in the diaphragm compared to controls (p < 0.01). Echocardiography demonstrated decreased systolic function in 9-month-old mutant mice (p < 0.01). There was increased myocardial wall thickness and mass (p < 0.001) with increased fibrosis in 9-month-old P448Lneo- mice compared to controls (p < 0.05). mRNA expression for natriuretic peptide type A (Nppa) was significantly increased in P448Lneo- mice compared to controls at 6 months (p < 0.05) and for natriuretic peptide type B (Nppb) at 6 and 9 months of age (p < 0.05). CONCLUSIONS FKRP-deficient P448Lneo- mice demonstrate significant deficits in cardiac and respiratory functions compared to control mice, and this is associated with increased inflammation and fibrosis. This study provides new functional outcome measures for preclinical trials of FKRP-related muscular dystrophies.
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Affiliation(s)
- Qing Yu
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, DC, USA
| | - Melissa Morales
- School of Pharmacy and Pharmaceutical Sciences, Binghamton University, State University of New York, Binghamton, NY, USA
| | - Ning Li
- School of Pharmacy and Pharmaceutical Sciences, Binghamton University, State University of New York, Binghamton, NY, USA
| | - Alexander G Fritz
- School of Pharmacy and Pharmaceutical Sciences, Binghamton University, State University of New York, Binghamton, NY, USA
| | - Ren Ruobing
- Department of Oncology, Ruijing Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Anthony Blaeser
- McColl-Lockwood Laboratory for Muscular Dystrophy Research, Department of Neurology, Carolinas Healthcare System, Charlotte, NC, USA
| | - Ershia Francois
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, DC, USA
| | - Qi-Long Lu
- McColl-Lockwood Laboratory for Muscular Dystrophy Research, Department of Neurology, Carolinas Healthcare System, Charlotte, NC, USA
| | - Kanneboyina Nagaraju
- School of Pharmacy and Pharmaceutical Sciences, Binghamton University, State University of New York, Binghamton, NY, USA
| | - Christopher F Spurney
- Children's National Heart Institute, Center for Genetic Medicine Research, Children's National Health System, Washington, DC, USA.
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16
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Genetics and mechanisms leading to human cortical malformations. Semin Cell Dev Biol 2018; 76:33-75. [DOI: 10.1016/j.semcdb.2017.09.031] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 09/21/2017] [Accepted: 09/21/2017] [Indexed: 02/06/2023]
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17
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Sciandra F, Scicchitano BM, Signorino G, Bigotti MG, Tavazzi B, Lombardi F, Bozzi M, Sica G, Giardina B, Blaess S, Brancaccio A. Evaluation of the effect of a floxed Neo cassette within the dystroglycan (Dag1) gene. BMC Res Notes 2017; 10:601. [PMID: 29157305 PMCID: PMC5696793 DOI: 10.1186/s13104-017-2926-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 11/10/2017] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVE Dystroglycan (DG) is an adhesion complex formed by two subunits, α-DG and β-DG. In skeletal muscle, DG is part of the dystrophin-glycoprotein complex that is crucial for sarcolemma stability and it is involved in a plethora of muscular dystrophy phenotypes. Due to the important role played by DG in skeletal muscle stability as well as in a wide variety of other tissues including brain and the peripheral nervous system, it is essential to investigate its genetic assembly and transcriptional regulation. RESULTS Herein, we analyze the effect of the insertion of a floxed neomycin (Neo) cassette within the 3' portion of the universally conserved IG1-intron of the DG gene (Dag1). We analyzed the transcription level of Dag1 and the expression of the DG protein in skeletal muscle of targeted mice compared to wild-type and we did not find any alterations that might be attributed to the gene targeting. However, we found an increase of the cross-sectional areas of tibialis anterior that might have some physiological significance that needs to be assessed in the future. Moreover, in targeted mice the skeletal muscle morphology and its regeneration capacity after injury did not show any evident alterations. We confirmed that the targeting of Dag1 with a floxed Neo-cassette did not produce any gross undesired effects.
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Affiliation(s)
- Francesca Sciandra
- Istituto di Chimica del Riconoscimento Molecolare (CNR), c/o Università Cattolica del Sacro Cuore, Rome, Italy
| | | | - Giulia Signorino
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Rome, Italy
| | | | - Barbara Tavazzi
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Francesca Lombardi
- Istituto di Clinica delle Malattie Infettive, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Manuela Bozzi
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Gigliola Sica
- Istituto di Istologia, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Bruno Giardina
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Sandra Blaess
- Neurodevelopmental Genetics, Institute of Reconstructive Neurobiology, Life and Brain Center, University of Bonn, Bonn, Germany
| | - Andrea Brancaccio
- Istituto di Chimica del Riconoscimento Molecolare (CNR), c/o Università Cattolica del Sacro Cuore, Rome, Italy
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD UK
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18
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Rehwaldt JD, Rodgers BD, Lin DC. Skeletal muscle contractile properties in a novel murine model for limb girdle muscular dystrophy 2i. J Appl Physiol (1985) 2017; 123:1698-1707. [PMID: 28860175 DOI: 10.1152/japplphysiol.00744.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Limb-girdle muscular dystrophy (LGMD) 2i results from mutations in fukutin-related protein and aberrant α-dystroglycan glycosylation. Although this significantly compromises muscle function and ambulation, the comprehensive characteristics of contractile dysfunction are unknown. Therefore, we quantified the in situ contractile properties of the medial gastrocnemius in young adult P448L mice, an affected muscle of a novel model of LGMD2i. Normalized maximal twitch force, tetanic force, and power were significantly smaller in P448L mice, compared with sex-matched, wild-type mice. These differences were consistent with the replacement of contractile fibers by passive tissue. The shape of the active force-length relationships were similar in both groups, regardless of sex, consistent with an intact sarcomeric structure in P448L mice. Passive force-length curves normalized to maximal isometric force were steeper in P448L mice, and passive elements contribute disproportionately more to total contractile force in P448L mice. Sex differences were mostly noted in the force-velocity curves, as normalized values for maximal and optimal velocities were significantly slower in P448L males, compared with wild-type, but not in P448L females. This suggests that the dystrophic phenotype, which may include possible changes in cross-bridge kinetics and fiber-type proportions, progresses more quickly in P448L males. These results together indicate that active force and power generation are compromised in both sexes of P448L mice, while passive forces increase. More importantly, the results identified several functional markers of disease pathophysiology that could aid in developing and assessment of novel therapeutics for LGMD2i and possibly other dystroglycanopathies as well. NEW & NOTEWORTHY Comprehensive assessments of muscle contractile function have, until now, never been performed in an animal model for any dystroglycanopathy. This study suggests that skeletal muscle contractile properties are significantly compromised in a recently developed model for limb-girdle muscular dystrophy 2i, the P448L mouse. It further identifies novel pathological markers of muscle function that are suitable for developing therapeutics and for better understanding of disease pathogenesis.
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Affiliation(s)
- Jordan D Rehwaldt
- Voiland School of Chemical Engineering and Bioengineering, Washington State University , Pullman, Washington
| | - Buel D Rodgers
- Department of Animal Sciences, Washington State University , Pullman, Washington.,Washington Center for Muscle Biology, Washington State University , Pullman, Washington
| | - David C Lin
- Voiland School of Chemical Engineering and Bioengineering, Washington State University , Pullman, Washington.,Department of Integrative Physiology and Neuroscience, Washington State University , Pullman, Washington.,Washington Center for Muscle Biology, Washington State University , Pullman, Washington
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19
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Krebs MP, Collin GB, Hicks WL, Yu M, Charette JR, Shi LY, Wang J, Naggert JK, Peachey NS, Nishina PM. Mouse models of human ocular disease for translational research. PLoS One 2017; 12:e0183837. [PMID: 28859131 PMCID: PMC5578669 DOI: 10.1371/journal.pone.0183837] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 08/12/2017] [Indexed: 01/24/2023] Open
Abstract
Mouse models provide a valuable tool for exploring pathogenic mechanisms underlying inherited human disease. Here, we describe seven mouse models identified through the Translational Vision Research Models (TVRM) program, each carrying a new allele of a gene previously linked to retinal developmental and/or degenerative disease. The mutations include four alleles of three genes linked to human nonsyndromic ocular diseases (Aipl1tvrm119, Aipl1tvrm127, Rpgrip1tvrm111, RhoTvrm334) and three alleles of genes associated with human syndromic diseases that exhibit ocular phentoypes (Alms1tvrm102, Clcn2nmf289, Fkrptvrm53). Phenotypic characterization of each model is provided in the context of existing literature, in some cases refining our current understanding of specific disease attributes. These murine models, on fixed genetic backgrounds, are available for distribution upon request and may be useful for understanding the function of the gene in the retina, the pathological mechanisms induced by its disruption, and for testing experimental approaches to treat the corresponding human ocular diseases.
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Affiliation(s)
- Mark P. Krebs
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Gayle B. Collin
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Wanda L. Hicks
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Minzhong Yu
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio, United States of America
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, United States of America
| | | | - Lan Ying Shi
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Jieping Wang
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | | | - Neal S. Peachey
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio, United States of America
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, United States of America
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, United States of America
| | - Patsy M. Nishina
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
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20
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Booler HS, Pagalday-Vergara V, Williams JL, Hopkinson M, Brown SC. Evidence of early defects in Cajal-Retzius cell localization during brain development in a mouse model of dystroglycanopathy. Neuropathol Appl Neurobiol 2017; 43:330-345. [PMID: 28039900 DOI: 10.1111/nan.12376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 08/10/2016] [Accepted: 12/31/2016] [Indexed: 01/21/2023]
Abstract
AIMS The secondary dystroglycanopathies represent a heterogeneous group of congenital muscular dystrophies characterized by the defective glycosylation of alpha dystroglycan. These disorders are associated with mutations in at least 17 genes, including Fukutin-related protein (FKRP). At the severe end of the clinical spectrum there is substantial brain involvement, and cobblestone lissencephaly is highly suggestive of these disorders. The precise pathogenesis of this phenotype has, however, remained unclear with most attention focused on the disruption to the radial glial scaffold. Here, we set out to investigate whether lesions are apparent prior to the differentiation of the radial glia. METHODS A detailed investigation of the structural brain defects from embryonic day 10.5 (E10.5) up until the time of birth (P0) was undertaken in the Fkrp-deficient mice (FKRPKD ). Reelin, and downstream PI3K/Akt signalling pathways were analysed using Western blot. RESULTS We show that early basement membrane defects and neuroglial ectopia precede radial glial cell differentiation. Furthermore, we identify mislocalization of Cajal-Retzius cells which nonetheless is not associated with any apparent disruption to the reelin, and downstream PI3K/Akt signalling pathways. CONCLUSIONS These observations identify Cajal-Retzius cell mislocalization as an early event during the development of cortical defects thereby identifying an earlier onset and more complex pathogenesis than originally reported for the secondary dystroglycanopathies. Overall this study provides new insight into central nervous system involvement in this group of diseases.
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Affiliation(s)
- H S Booler
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - V Pagalday-Vergara
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - J L Williams
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - M Hopkinson
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - S C Brown
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
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21
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216th ENMC international workshop: Clinical readiness in FKRP related myopathies January 15–17, 2016 Naarden, The Netherlands. Neuromuscul Disord 2016; 26:717-724. [DOI: 10.1016/j.nmd.2016.08.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 08/19/2016] [Indexed: 11/22/2022]
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Transgenic Rescue of the LARGEmyd Mouse: A LARGE Therapeutic Window? PLoS One 2016; 11:e0159853. [PMID: 27467128 PMCID: PMC4965172 DOI: 10.1371/journal.pone.0159853] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 07/08/2016] [Indexed: 12/02/2022] Open
Abstract
LARGE is a glycosyltransferase involved in glycosylation of α-dystroglycan (α-DG). Absence of this protein in the LARGEmyd mouse results in α-DG hypoglycosylation, and is associated with central nervous system abnormalities and progressive muscular dystrophy. Up-regulation of LARGE has previously been proposed as a therapy for the secondary dystroglycanopathies: overexpression in cells compensates for defects in multiple dystroglycanopathy genes. Counterintuitively, LARGE overexpression in an FKRP-deficient mouse exacerbates pathology, suggesting that modulation of α-DG glycosylation requires further investigation. Here we demonstrate that transgenic expression of human LARGE (LARGE-LV5) in the LARGEmyd mouse restores α-DG glycosylation (with marked hyperglycosylation in muscle) and that this corrects both the muscle pathology and brain architecture. By quantitative analyses of LARGE transcripts we also here show that levels of transgenic and endogenous LARGE in the brains of transgenic animals are comparable, but that the transgene is markedly overexpressed in heart and particularly skeletal muscle (20–100 fold over endogenous). Our data suggest LARGE overexpression may only be deleterious under a forced regenerative context, such as that resulting from a reduction in FKRP: in the absence of such a defect we show that systemic expression of LARGE can indeed act therapeutically, and that even dramatic LARGE overexpression is well-tolerated in heart and skeletal muscle. Moreover, correction of LARGEmyd brain pathology with only moderate, near-physiological LARGE expression suggests a generous therapeutic window.
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Identification of a Post-translational Modification with Ribitol-Phosphate and Its Defect in Muscular Dystrophy. Cell Rep 2016; 14:2209-2223. [PMID: 26923585 DOI: 10.1016/j.celrep.2016.02.017] [Citation(s) in RCA: 157] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 12/25/2015] [Accepted: 01/28/2016] [Indexed: 11/21/2022] Open
Abstract
Glycosylation is an essential post-translational modification that underlies many biological processes and diseases. α-dystroglycan (α-DG) is a receptor for matrix and synaptic proteins that causes muscular dystrophy and lissencephaly upon its abnormal glycosylation (α-dystroglycanopathies). Here we identify the glycan unit ribitol 5-phosphate (Rbo5P), a phosphoric ester of pentose alcohol, in α-DG. Rbo5P forms a tandem repeat and functions as a scaffold for the formation of the ligand-binding moiety. We show that enzyme activities of three major α-dystroglycanopathy-causing proteins are involved in the synthesis of tandem Rbo5P. Isoprenoid synthase domain-containing (ISPD) is cytidine diphosphate ribitol (CDP-Rbo) synthase. Fukutin and fukutin-related protein are sequentially acting Rbo5P transferases that use CDP-Rbo. Consequently, Rbo5P glycosylation is defective in α-dystroglycanopathy models. Supplementation of CDP-Rbo to ISPD-deficient cells restored α-DG glycosylation. These findings establish the molecular basis of mammalian Rbo5P glycosylation and provide insight into pathogenesis and therapeutic strategies in α-DG-associated diseases.
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Kim J, Hopkinson M, Kavishwar M, Fernandez-Fuente M, Brown SC. Prenatal muscle development in a mouse model for the secondary dystroglycanopathies. Skelet Muscle 2016; 6:3. [PMID: 26900448 PMCID: PMC4759920 DOI: 10.1186/s13395-016-0073-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 01/05/2016] [Indexed: 12/17/2022] Open
Abstract
Background The defective glycosylation of α-dystroglycan is associated with a group of muscular dystrophies that are collectively referred to as the secondary dystroglycanopathies. Mutations in the gene encoding fukutin-related protein (FKRP) are one of the most common causes of secondary dystroglycanopathy in the UK and are associated with a wide spectrum of disease. Whilst central nervous system involvement has a prenatal onset, no studies have addressed prenatal muscle development in any of the mouse models for this group of diseases. In view of the pivotal role of α-dystroglycan in early basement membrane formation, we sought to determine if the muscle formation was altered in a mouse model of FKRP-related dystrophy. Results Mice with a knock-down in FKRP (FKRPKD) showed a marked reduction in α-dystroglycan glycosylation and reduction in laminin binding by embryonic day 15.5 (E15.5), relative to wild type controls. In addition, the total number of Pax7+ progenitor cells in the FKRPKD tibialis anterior at E15.5 was significantly reduced, and myotube cluster/myofibre size showed a significant reduction in size. Moreover, myoblasts isolated from the limb muscle of these mice at E15.5 showed a marked reduction in their ability to form myotubes in vitro. Conclusions These data identify an early reduction of laminin α2, reduction of myogenicity and depletion of Pax7+ progenitor cells which would be expected to compromise subsequent postnatal muscle growth and its ability to regenerate postnatally. These findings are of significance to the development of future therapies in this group of devastating conditions.
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Affiliation(s)
- Jihee Kim
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London, UK
| | - Mark Hopkinson
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London, UK
| | - Manoli Kavishwar
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London, UK
| | - Marta Fernandez-Fuente
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London, UK
| | - Susan Carol Brown
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London, UK
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Saunier M, Bönnemann CG, Durbeej M, Allamand V. 212th ENMC International Workshop: Animal models of congenital muscular dystrophies, Naarden, The Netherlands, 29-31 May 2015. Neuromuscul Disord 2016; 26:252-9. [PMID: 26948708 DOI: 10.1016/j.nmd.2016.02.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 02/08/2016] [Accepted: 02/09/2016] [Indexed: 12/18/2022]
Affiliation(s)
- M Saunier
- UPMC Univ Paris 06, Inserm UMRS974, CNRS FRE3617, Center for Research in Myology, Institut de Myologie, GH Pitié-Salpêtrière, Sorbonne Universités, F-75013 Paris, France
| | - C G Bönnemann
- National Institutes of Health, Neuromuscular and Neurogenetic Disorders of Childhood Section, Bethesda, MD, USA
| | - M Durbeej
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - V Allamand
- UPMC Univ Paris 06, Inserm UMRS974, CNRS FRE3617, Center for Research in Myology, Institut de Myologie, GH Pitié-Salpêtrière, Sorbonne Universités, F-75013 Paris, France.
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Krag TO, Vissing J. A New Mouse Model of Limb-Girdle Muscular Dystrophy Type 2I Homozygous for the Common L276I Mutation Mimicking the Mild Phenotype in Humans. J Neuropathol Exp Neurol 2015. [DOI: 10.1093/jnen/74.12.1137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Small molecules enhance functional O-mannosylation of Alpha-dystroglycan. Bioorg Med Chem 2015; 23:7661-70. [PMID: 26652968 DOI: 10.1016/j.bmc.2015.11.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 10/30/2015] [Accepted: 11/12/2015] [Indexed: 12/23/2022]
Abstract
Alpha-dystroglycan (α-DG), a highly glycosylated receptor for extracellular matrix proteins, plays a critical role in many biological processes. Hypoglycosylation of α-DG results in various types of muscular dystrophies and is also highly associated with progression of majority of cancers. Currently, there are no effective treatments for those devastating diseases. Enhancing functional O-mannosyl glycans (FOG) of α-DG on the cell surfaces is a potential approach to address this unmet challenge. Based on the hypothesis that the cells can up-regulate FOG of α-DG in response to certain chemical stimuli, we developed a cell-based high-throughput screening (HTS) platform for searching chemical enhancers of FOG of α-DG from a large chemical library with 364,168 compounds. Sequential validation of the hits from a primary screening campaign and chemical works led to identification of a cluster of compounds that positively modulate FOG of α-DG on various cell surfaces including patient-derived myoblasts. These compounds enhance FOG of α-DG by almost ten folds, which provide us powerful tools for O-mannosylation studies and potential starting points for the development of drug to treat dystroglycanopathy.
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Booler HS, Williams JL, Hopkinson M, Brown SC. Degree of Cajal-Retzius Cell Mislocalization Correlates with the Severity of Structural Brain Defects in Mouse Models of Dystroglycanopathy. Brain Pathol 2015; 26:465-78. [PMID: 26306834 DOI: 10.1111/bpa.12306] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 08/23/2015] [Indexed: 12/19/2022] Open
Abstract
The secondary dystroglycanopathies are characterized by the hypoglycosylation of alpha dystroglycan, and are associated with mutations in at least 18 genes that act on the glycosylation of this cell surface receptor rather than the Dag1 gene itself. At the severe end of the disease spectrum, there are substantial structural brain defects, the most striking of which is often cobblestone lissencephaly. The aim of this study was to determine the gene-specific aspects of the dystroglycanopathy brain phenotype through a detailed investigation of the structural brain defects present at birth in three mouse models of dystroglycanopathy-the FKRP(KD) , which has an 80% reduction in Fkrp transcript levels; the Pomgnt1null , which carries a deletion of exons 7-16 of the Pomgnt1 gene; and the Large(myd) mouse, which carries a deletion of exons 5-7 of the Large gene. We show a rostrocaudal and mediolateral gradient in the severity of brain lesions in FKRP(KD) , and to a lesser extent Pomgnt1null mice. Furthermore, the mislocalization of Cajal-Retzius cells is correlated with the gradient of these lesions and the severity of the brain phenotype in these models. Overall these observations implicate gene-specific differences in the pathogenesis of brain lesions in this group of disorders.
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Affiliation(s)
- Helen S Booler
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - Josie L Williams
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - Mark Hopkinson
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
| | - Susan C Brown
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
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Humphrey EL, Lacey E, Le LT, Feng L, Sciandra F, Morris CR, Hewitt JE, Holt I, Brancaccio A, Barresi R, Sewry CA, Brown SC, Morris GE. A new monoclonal antibody DAG-6F4 against human alpha-dystroglycan reveals reduced core protein in some, but not all, dystroglycanopathy patients. Neuromuscul Disord 2015; 25:32-42. [DOI: 10.1016/j.nmd.2014.09.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 09/01/2014] [Accepted: 09/08/2014] [Indexed: 11/28/2022]
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Whitmore C, Morgan J. What do mouse models of muscular dystrophy tell us about the DAPC and its components? Int J Exp Pathol 2014; 95:365-77. [PMID: 25270874 PMCID: PMC4285463 DOI: 10.1111/iep.12095] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/16/2014] [Indexed: 12/17/2022] Open
Abstract
There are over 30 mouse models with mutations or inactivations in the dystrophin-associated protein complex. This complex is thought to play a crucial role in the functioning of muscle, as both a shock absorber and signalling centre, although its role in the pathogenesis of muscular dystrophy is not fully understood. The first mouse model of muscular dystrophy to be identified with a mutation in a component of the dystrophin-associated complex (dystrophin) was the mdx mouse in 1984. Here, we evaluate the key characteristics of the mdx in comparison with other mouse mutants with inactivations in DAPC components, along with key modifiers of the disease phenotype. By discussing the differences between the individual phenotypes, we show that the functioning of the DAPC and consequently its role in the pathogenesis is more complicated than perhaps currently appreciated.
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Affiliation(s)
- Charlotte Whitmore
- Dubowitz Neuromuscular Centre, Molecular Neurosciences Section, Developmental Neurosciences Programme, Institute of Child Health, University College LondonLondon, UK
| | - Jennifer Morgan
- Dubowitz Neuromuscular Centre, Molecular Neurosciences Section, Developmental Neurosciences Programme, Institute of Child Health, University College LondonLondon, UK
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Whitmore C, Fernandez-Fuente M, Booler H, Parr C, Kavishwar M, Ashraf A, Lacey E, Kim J, Terry R, Ackroyd MR, Wells KE, Muntoni F, Wells DJ, Brown SC. The transgenic expression of LARGE exacerbates the muscle phenotype of dystroglycanopathy mice. Hum Mol Genet 2013; 23:1842-55. [PMID: 24234655 DOI: 10.1093/hmg/ddt577] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations in fukutin-related protein (FKRP) underlie a group of muscular dystrophies associated with the hypoglycosylation of α-dystroglycan (α-DG), a proportion of which show central nervous system involvement. Our original FKRP knock-down mouse (FKRP(KD)) replicated many of the characteristics seen in patients at the severe end of the dystroglycanopathy spectrum but died perinatally precluding its full phenotyping and use in testing potential therapies. We have now overcome this by crossing FKRP(KD) mice with those expressing Cre recombinase under the Sox1 promoter. Owing to our original targeting strategy, this has resulted in the restoration of Fkrp levels in the central nervous system but not the muscle, thereby generating a new model (FKRP(MD)) which develops a progressive muscular dystrophy resembling what is observed in limb girdle muscular dystrophy. Like-acetylglucosaminyltransferase (LARGE) is a bifunctional glycosyltransferase previously shown to hyperglycosylate α-DG. To investigate the therapeutic potential of LARGE up-regulation, we have now crossed the FKRP(MD) line with one overexpressing LARGE and show that, contrary to expectation, this results in a worsening of the muscle pathology implying that any future strategies based upon LARGE up-regulation require careful management.
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Affiliation(s)
- Charlotte Whitmore
- Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK
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Blaeser A, Keramaris E, Chan YM, Sparks S, Cowley D, Xiao X, Lu QL. Mouse models of fukutin-related protein mutations show a wide range of disease phenotypes. Hum Genet 2013; 132:923-34. [PMID: 23591631 DOI: 10.1007/s00439-013-1302-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 03/28/2013] [Indexed: 11/26/2022]
Abstract
Dystroglycanopathies are characterized by a reduction in the glycosylation of alpha-dystroglycan (α-DG). A common cause for this subset of muscular dystrophies is mutations in the gene of fukutin-related protein (FKRP). FKRP mutations have been associated with a wide spectrum of clinical severity from severe Walker-Warburg syndrome and muscle-eye-brain disease with brain and eye defects to mild limb-girdle muscular dystrophy 2I with myopathy only. To examine the affects of FKRP mutations on the severity of the disease, we have generated homozygous and compound heterozygous mouse models with human mutations in the murine FKRP gene. P448Lneo+ and E310delneo+ mutations result in severe dystrophic and embryonic lethal phenotypes, respectively. P448Lneo+/E310delneo+ compound heterozygotes exhibit brain defects and severe muscular dystrophies with near absence of α-DG glycosylation. Removal of the Neo(r) cassette from the P448Lneo+ homozygous mice eliminates overt brain and eye defects, and reduces severity of dystrophic phenotypes. Furthermore, introduction of the common L276I mutation to generate transgenic L276Ineo+ homozygous and L276Ineo+/P448Lneo+ and L276Ineo+/E310delneo+ compound heterozygotes results in mice displaying milder dystrophies with reduced α-DG glycosylation and no apparent brain defects. Limited sampling and variation in functionally glycosylated α-DG levels between and within muscles may explain the difficulties in correlating FKRP expression levels with phenotype in clinics. The nature of individual mutations, expression levels and status of muscle differentiation all contribute to the phenotypic manifestation. These mutant FKRP mice are useful models for the study of disease mechanism(s) and experimental therapies.
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Affiliation(s)
- Anthony Blaeser
- McColl-Lockwood Laboratory for Muscular Dystrophy Research, Neuromuscular/ALS Center, Carolinas Medical Center, Charlotte, NC 28231, USA.
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Beedle AM, Turner AJ, Saito Y, Lueck JD, Foltz SJ, Fortunato MJ, Nienaber PM, Campbell KP. Mouse fukutin deletion impairs dystroglycan processing and recapitulates muscular dystrophy. J Clin Invest 2012; 122:3330-42. [PMID: 22922256 DOI: 10.1172/jci63004] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 06/21/2012] [Indexed: 11/17/2022] Open
Abstract
Dystroglycan is a transmembrane glycoprotein that links the extracellular basement membrane to cytoplasmic dystrophin. Disruption of the extensive carbohydrate structure normally present on α-dystroglycan causes an array of congenital and limb girdle muscular dystrophies known as dystroglycanopathies. The essential role of dystroglycan in development has hampered elucidation of the mechanisms underlying dystroglycanopathies. Here, we developed a dystroglycanopathy mouse model using inducible or muscle-specific promoters to conditionally disrupt fukutin (Fktn), a gene required for dystroglycan processing. In conditional Fktn-KO mice, we observed a near absence of functionally glycosylated dystroglycan within 18 days of gene deletion. Twenty-week-old KO mice showed clear dystrophic histopathology and a defect in glycosylation near the dystroglycan O-mannose phosphate, whether onset of Fktn excision driven by muscle-specific promoters occurred at E8 or E17. However, the earlier gene deletion resulted in more severe phenotypes, with a faster onset of damage and weakness, reduced weight and viability, and regenerating fibers of smaller size. The dependence of phenotype severity on the developmental timing of muscle Fktn deletion supports a role for dystroglycan in muscle development or differentiation. Moreover, given that this conditional Fktn-KO mouse allows the generation of tissue- and timing-specific defects in dystroglycan glycosylation, avoids embryonic lethality, and produces a phenotype resembling patient pathology, it is a promising new model for the study of secondary dystroglycanopathy.
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Affiliation(s)
- Aaron M Beedle
- Howard Hughes Medical Institute, Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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The dystrophin–glycoprotein complex in brain development and disease. Trends Neurosci 2012; 35:487-96. [DOI: 10.1016/j.tins.2012.04.004] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 04/03/2012] [Accepted: 04/15/2012] [Indexed: 11/23/2022]
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Muscular dystrophies due to glycosylation defects: diagnosis and therapeutic strategies. Curr Opin Neurol 2012; 24:437-42. [PMID: 21825985 DOI: 10.1097/wco.0b013e32834a95e3] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
PURPOSE OF REVIEW Dystroglycanopathies are a common group of diseases characterized by a reduction in α-dystroglycan glycosylation. This review discusses the recent novel discovery of additional dystroglycanopathy variants and progress in dystroglycanopathy animal models. RECENT FINDINGS Several novel glycosyltransferase genes have been found to be responsible for a dystroglycanopathy phenotype, and in addition recessive mutations in DAG1 have been identified for the first time in a primary dystroglycanopathy. Studies in dystroglycanopathy mouse models have clarified some aspects of the structural defects observed in the central nervous system and in the eye, whereas a study in zebrafish implicates unfolded protein response in the pathogenesis of two of the secondary dystroglycanopathies. SUMMARY Improved understanding of the molecular bases of dystroglycanopathies will lead to more precise diagnosis and genetic counseling; therapeutic strategies are being developed and tested in the preclinical models and it is hoped that these observations will pave the way to therapeutic interventions in humans.
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Ng R, Banks GB, Hall JK, Muir LA, Ramos JN, Wicki J, Odom GL, Konieczny P, Seto J, Chamberlain JR, Chamberlain JS. Animal models of muscular dystrophy. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 105:83-111. [PMID: 22137430 DOI: 10.1016/b978-0-12-394596-9.00004-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The muscular dystrophies (MDs) represent a diverse collection of inherited human disorders, which affect to varying degrees skeletal, cardiac, and sometimes smooth muscle (Emery, 2002). To date, more than 50 different genes have been implicated as causing one or more types of MD (Bansal et al., 2003). In many cases, invaluable insights into disease mechanisms, structure and function of gene products, and approaches for therapeutic interventions have benefited from the study of animal models of the different MDs (Arnett et al., 2009). The large number of genes that are associated with MD and the tremendous number of animal models that have been developed preclude a complete discussion of each in the context of this review. However, we summarize here a number of the more commonly used models together with a mixture of different types of gene and MD, which serves to give a general overview of the value of animal models of MD for research and therapeutic development.
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Affiliation(s)
- Rainer Ng
- Division of Medical Genetics, Department of Neurology, University of Washington, Seattle, Washington, USA
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37
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Patel K, Morgan J. 185th ENMC International Workshop: stem/precursor cells as a therapeutic strategy for muscular dystrophies 3-5 June 2011, Naarden, The Netherlands. Neuromuscul Disord 2011; 22:447-52. [PMID: 22130186 DOI: 10.1016/j.nmd.2011.09.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 09/29/2011] [Indexed: 01/06/2023]
Affiliation(s)
- Ketan Patel
- School of Biological Sciences, University of Reading, Hopkins Building, Reading RG6 6UB, UK
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Chan YM, Brown SC, Lu Q. Second International Workshop for Glycosylation Defects in Muscular Dystrophies, 11-12 November, 2010, Charlotte, USA. Brain Pathol 2011; 21:699-704. [DOI: 10.1111/j.1750-3639.2011.00494.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Abstract
Mutations in fukutin-related protein (FKRP) are responsible for a common group of muscular dystrophies ranging from adult onset limb girdle muscular dystrophies to severe congenital forms with associated structural brain involvement. The defining feature of this group of disorders is the hypoglycosylation of α-dystroglycan and its inability to effectively bind extracellular matrix ligands such as laminin α2. However, α-dystroglycan has the potential to interact with a number of laminin isoforms many of which are basement membrane/tissue specific and developmentally regulated. To further investigate this we evaluated laminin α-chain expression in the cerebral cortex and eye of our FKRP knock-down mouse (FKRP(KD)). These mice showed a marked disturbance in the deposition of laminin α-chains including α1, α2, α4, and α5, although only laminin α1- and γ1-chain mRNA expression was significantly upregulated relative to controls. Moreover, there was a diffuse pattern of laminin deposition below the pial surface which correlated with an abrupt termination of many of the radial glial cells. This along with the pial basement membrane defects, contributed to the abnormal positioning of both early- and late-born neurons. Defects in the inner limiting membrane of the eye were associated with a reduction of laminin α1 demonstrating the involvement of the α-dystroglycan:laminin α1 axis in the disease process. These observations demonstrate for the first time that a reduction in Fkrp influences the ability of tissue-specific forms of α-dystroglycan to direct the deposition of several laminin isoforms in the formation of different basement membranes.
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Wood AJ, Müller JS, Jepson CD, Laval SH, Lochmüller H, Bushby K, Barresi R, Straub V. Abnormal vascular development in zebrafish models for fukutin and FKRP deficiency. Hum Mol Genet 2011; 20:4879-90. [PMID: 21926082 DOI: 10.1093/hmg/ddr426] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Fukutin and fukutin-related protein (FKRP) are involved in the glycosylation of α-dystroglycan, a key receptor for basement membrane proteins. Aberrant α-dystroglycan glycosylation leads to a broad spectrum of disorders, ranging from limb girdle muscular dystrophy to Walker-Warburg syndrome. This is the first study investigating a role of fukutin and FKRP-mediated glycosylation in angiogenesis. Transgenic zebrafish expressing enhanced green fluorescent protein in blood vessels were treated with morpholino antisense oligonucleotides that blocked the expression of fukutin, FKRP and dystroglycan. All morphant fish showed muscle damage and vascular abnormalities at day 1 post-fertilization. Intersegmental vessels of somites failed to reach the dorsal longitudinal anastomosis and in more severe phenotypes retracted further or were in some cases even completely missing. In contrast, the eye vasculature was distorted in both fukutin and FKRP morphants, but not in dystroglycan morphants or control fish. The eye size was also smaller in the fukutin and FKRP morphants when compared with dystroglycan knockdown fish and controls. In general, the fukutin morphant fish had the most severe skeletal muscle and eye phenotype. Our findings suggest that fukutin and FKRP have functions that affect ocular development in zebrafish independently of dystroglycan. Despite anecdotal reports about vascular abnormalities in patients affected by dystroglycanopathies, the clinical relevance of such lesions remains unclear and should be subject to further review and investigations.
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Affiliation(s)
- Alasdair J Wood
- International Centre for Life, Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne NE1 3BZ, UK
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Godfrey C, Foley AR, Clement E, Muntoni F. Dystroglycanopathies: coming into focus. Curr Opin Genet Dev 2011; 21:278-85. [PMID: 21397493 DOI: 10.1016/j.gde.2011.02.001] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 01/20/2011] [Accepted: 02/04/2011] [Indexed: 11/18/2022]
Abstract
A common group of muscular dystrophies is associated with the aberrant glycosylation of α-dystroglycan. These clinically heterogeneous disorders, collectively termed dystroglycanopathies, are often associated with central nervous system and more rarely eye pathology. Defects in a total of eight putative and demonstrated glycosyltransferases or accessory proteins of glycosyltransferases have been shown to cause a dystroglycanopathy phenotype. In recent years the systematic analysis of large patient cohorts has uncovered a complex relationship between the underlying genetic defect and the resulting clinical phenotype. These studies have also drawn attention to the high proportion of patients that remain without a genetic diagnosis implicating novel genes in the pathogenesis of dystroglycanopathies. Recent glycomic analyses of α-dystroglycan have reported complex patterns of glycan composition and have uncovered novel glycan modifications. The exact glycan synthesis and modification pathways involved, as well as their role in ligand binding, remain only partially characterised. This review will focus on recent studies that have extended our knowledge of the mechanisms underlying dystroglycanopathies and have further characterised this patient population.
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Affiliation(s)
- Caroline Godfrey
- Dubowitz Neuromuscular Centre, UCL Institute of Child Health and the Great Ormond Street Hospital for Children, Guilford Street, University College London, United Kingdom
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Lin YY, White RJ, Torelli S, Cirak S, Muntoni F, Stemple DL. Zebrafish Fukutin family proteins link the unfolded protein response with dystroglycanopathies. Hum Mol Genet 2011; 20:1763-75. [PMID: 21317159 PMCID: PMC3071672 DOI: 10.1093/hmg/ddr059] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Allelic mutations in putative glycosyltransferase genes, fukutin and fukutin-related protein (fkrp), lead to a wide range of muscular dystrophies associated with hypoglycosylation of α-dystroglycan, commonly referred to as dystroglycanopathies. Defective glycosylation affecting dystroglycan–ligand interactions is considered to underlie the disease pathogenesis. We have modelled dystroglycanopathies in zebrafish using a novel loss-of-function dystroglycan allele and by inhibition of Fukutin family protein activities. We show that muscle pathology in embryos lacking Fukutin or FKRP is different from loss of dystroglycan. In addition to hypoglycosylated α-dystroglycan, knockdown of Fukutin or FKRP leads to a notochord defect and a perturbation of laminin expression before muscle degeneration. These are a consequence of endoplasmic reticulum stress and activation of the unfolded protein response (UPR), preceding loss of dystroglycan–ligand interactions. Together, our results suggest that Fukutin family proteins may play important roles in protein secretion and that the UPR may contribute to the phenotypic spectrum of some dystroglycanopathies in humans.
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Affiliation(s)
- Yung-Yao Lin
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
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Gupta V, Kawahara G, Gundry SR, Chen AT, Lencer WI, Zhou Y, Zon LI, Kunkel LM, Beggs AH. The zebrafish dag1 mutant: a novel genetic model for dystroglycanopathies. Hum Mol Genet 2011; 20:1712-25. [PMID: 21296866 DOI: 10.1093/hmg/ddr047] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In a forward genetic approach to identify novel genes for congenital muscle diseases, a zebrafish mutant, designated patchytail, was identified that exhibits degenerating muscle fibers with impaired motility behavior. Genetic mapping identified a genomic locus containing the zebrafish ortholog of the dystroglycan gene (DAG1). Patchytail fish contain a point mutation (c.1700T>A) in dag1, resulting in a missense change p.V567D. This change is associated with reduced transcripts and a complete absence of protein. The absence of α-dystroglycan and β-dystroglycan caused destabilization of dystroglycan complex, resulting in membrane damages. Membrane damage was localized on the extracellular matrix at myosepta as well as basement membrane between adjacent myofibers. These studies also identified structural abnormalities in triads at 3 days post fertilization (dpf) of dystroglycan-deficient muscles, significantly preceding sarcolemmal damage that becomes evident at 7 dpf. Immunofluorescence studies identified a subpopulation of dystroglycan that is expressed at t-tubules in normal skeletal muscles. In dag1-mutated fish, smaller and irregular-shaped t-tubule vesicles, as well as highly disorganized terminal cisternae of sarcoplasmic reticulum, were common. In addition to skeletal muscle defects, dag1-mutated fish have brain abnormalities and ocular defects in posterior as well as anterior chambers. These phenotypes of dystroglycan-deficient fish are highly reminiscent of the phenotypes observed in the human conditions muscle-eye-brain disease and Walker-Warburg syndrome. This animal model will provide unique opportunities in the understanding of biological functions of dystroglycan in a wide range of dystroglycanopathies, as disruption of this gene in higher vertebrates results in early embryonic lethality.
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Affiliation(s)
- Vandana Gupta
- Genomics Program and Division of Genetics, The Manton Center for Orphan Disease Research, Children's Hospital Boston, Boston, MA 02115, USA
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Post-Natal knockdown of fukutin-related protein expression in muscle by long-termRNA interference induces dystrophic pathology [corrected]. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 178:261-72. [PMID: 21224063 DOI: 10.1016/j.ajpath.2010.11.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 08/08/2010] [Accepted: 09/08/2010] [Indexed: 01/15/2023]
Abstract
Limb-girdle muscular dystrophy 2I (LGMD2I) is caused by mutations in the fukutin-related protein (FKRP) gene. Unlike its severe allelic forms, LGMD2I usually involves slower onset and milder course without defects in the central nervous system. The lack of viable animal models that closely recapitulate LGMD2I clinical phenotypes led us to use RNA interference technology to knock down FKRP expression via postnatal gene delivery so as to circumvent embryonic lethality. Specifically, an adeno-associated viral vector was used to deliver short hairpin (shRNA) genes to healthy ICR mice. Adeno-associated viral vectors expressing a single shRNA or two different shRNAs were injected one time into the hind limb muscles. We showed that FKRP expression at 10 months postinjection was reduced by about 50% with a single shRNA and by 75% with the dual shRNA cassette. Dual-cassette injection also reduced a-dystroglycan glycosylation and its affinity to laminin by up to 70% and induced α-dystrophic pathology, including fibrosis and central nucleation, in more than 50% of the myofibers at 10 months after injection. These results suggest that the reduction of approximately or more than 75% of the normal level of FKRP expression induces chronic dystrophic phenotypes in skeletal muscles. Furthermore, the restoration of about 25% of the normal FKRP level could be sufficient for LGMD2I therapy to correct the genetic deficiency effectively and prevent dystrophic pathology.
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Hu H, Li J, Zhang Z, Yu M. Pikachurin interaction with dystroglycan is diminished by defective O-mannosyl glycosylation in congenital muscular dystrophy models and rescued by LARGE overexpression. Neurosci Lett 2010; 489:10-5. [PMID: 21129441 DOI: 10.1016/j.neulet.2010.11.056] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 11/19/2010] [Accepted: 11/19/2010] [Indexed: 11/24/2022]
Abstract
Congenital muscular dystrophies (CMD) such as muscle-eye-brain disease caused by defective glycosylation of α-dystroglycan (α-DG) exhibit defective photoreceptor synaptic function. Mouse knockouts of dystroglycan and its extracellular matrix binding partner pikachurin recapitulate this phenotype. In this study, pikachurin-α-dystroglycan interactions in several mouse models of CMD were examined by pikachurin overlay experiments. The results show that hypoglycosylation of α-dystroglycan resulted in markedly reduced pikachurin-α-dystroglycan interactions. Expression of pikachurin is abolished at the outer plexiform layer of two mouse models, protein O-mannose N-acetylglucosaminyl transferase 1 (POMGnT1) knockout and Large(myd) mice. Overexpressing LARGE restored this interaction in POMGnT1 knockout cells. These results indicate that pikachurin interactions with α-dystroglycan and its localization at the photoreceptor ribbon synapse require normal glycosylation of α-dystroglycan.
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Affiliation(s)
- Huaiyu Hu
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY 13210, United States.
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Distinct functions of glial and neuronal dystroglycan in the developing and adult mouse brain. J Neurosci 2010; 30:14560-72. [PMID: 20980614 DOI: 10.1523/jneurosci.3247-10.2010] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cobblestone (type II) lissencephaly and mental retardation are characteristic features of a subset of congenital muscular dystrophies that include Walker-Warburg syndrome, muscle-eye-brain disease, and Fukuyama-type congenital muscular dystrophy. Although the majority of clinical cases are genetically undefined, several causative genes have been identified that encode known or putative glycosyltransferases in the biosynthetic pathway of dystroglycan. Here we test the effects of brain-specific deletion of dystroglycan, and show distinct functions for neuronal and glial dystroglycan. Deletion of dystroglycan in the whole brain produced glial/neuronal heterotopia resembling the cerebral cortex malformation in cobblestone lissencephaly. In wild-type mice, dystroglycan stabilizes the basement membrane of the glia limitans, thereby supporting the cortical infrastructure necessary for neuronal migration. This function depends on extracellular dystroglycan interactions, since the cerebral cortex developed normally in transgenic mice that lack the dystroglycan intracellular domain. Also, forebrain histogenesis was preserved in mice with neuron-specific deletion of dystroglycan, but hippocampal long-term potentiation was blunted, as is also the case in the Largemyd mouse, in which dystroglycan glycosylation is disrupted. Our findings provide genetic evidence that neuronal dystroglycan plays a role in synaptic plasticity and that glial dystroglycan is involved in forebrain development. Differences in dystroglycan glycosylation in distinct cell types of the CNS may contribute to the diversity of dystroglycan function in the CNS, as well as to the broad clinical spectrum of type II lissencephalies.
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Morgan JE, Zammit PS. Direct effects of the pathogenic mutation on satellite cell function in muscular dystrophy. Exp Cell Res 2010; 316:3100-8. [DOI: 10.1016/j.yexcr.2010.05.014] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Accepted: 05/03/2010] [Indexed: 12/14/2022]
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Chan YM, Keramaris-Vrantsis E, Lidov HG, Norton JH, Zinchenko N, Gruber HE, Thresher R, Blake DJ, Ashar J, Rosenfeld J, Lu QL. Fukutin-related protein is essential for mouse muscle, brain and eye development and mutation recapitulates the wide clinical spectrums of dystroglycanopathies. Hum Mol Genet 2010; 19:3995-4006. [PMID: 20675713 DOI: 10.1093/hmg/ddq314] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations in fukutin-related protein (FKRP) cause a common subset of muscular dystrophies characterized by aberrant glycosylation of alpha-dystroglycan (α-DG), collectively known as dystroglycanopathies. The clinical variations associated with FKRP mutations range from mild limb-girdle muscular dystrophy type 2I with predominantly muscle phenotypes to severe Walker-Warburg syndrome and muscle-eye-brain disease with striking structural brain and eye defects. In the present study, we have generated animal models and demonstrated that ablation of FKRP functions is embryonic lethal and that the homozygous-null embryos die before reaching E12.5. The homozygous knock-in mouse carrying the missense P448L mutation almost completely lacks functional glycosylation of α-DG in muscles and brain, validating the essential role of FKRP in the functional glycosylation of α-DG. However, the knock-in mouse survives and develops a wide range of structural abnormalities in the central nervous system, characteristics of neuronal migration defects. The brain and eye defects are highly reminiscent of the phenotypes seen in severe dystroglycanopathy patients. In addition, skeletal muscles develop progressive muscular dystrophy. Our results confirm that post-translational modifications of α-DG are essential for normal development of the brain and eyes. In addition, both the mutation itself and the levels of FKRP expression are equally critical for the survival of the animals. The exceptionally wide clinical spectrums recapitulated in the P448L mice also suggest the involvement of other factors in the disease progression. The mutant mouse represents a valuable model to further elucidate the functions of FKRP and develop therapies for FKRP-related muscular dystrophies.
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Affiliation(s)
- Yiumo Michael Chan
- McColl-Lockwood Laboratory for Muscular Dystrophy Research, Neuromuscular/ALS Center, Carolinas Medical Center, Charlotte, NC 28231, USA
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Van Reeuwijk J, Olderode-Berends MJW, Van den Elzen C, Brouwer OF, Roscioli T, Van Pampus MG, Scheffer H, Brunner HG, Van Bokhoven H, Hol FA. A homozygous FKRP start codon mutation is associated with Walker-Warburg syndrome, the severe end of the clinical spectrum. Clin Genet 2010; 78:275-81. [PMID: 20236121 DOI: 10.1111/j.1399-0004.2010.01384.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Dystroglycanopathies are a heterogeneous group of disorders caused by defects in the glycosylation pathway of alpha-dystroglycan. The clinical spectrum ranges from severe congenital muscular dystrophy with structural brain and eye involvement to a relatively mild adult onset limb-girdle muscular dystrophy without brain abnormalities and normal intelligence. Mutations have been identified in one of six putative or demonstrated glycosyltransferases. Many different FKRP mutations have been identified, which cover the complete clinical spectrum of dystroglycanopathies. In contrast to the other known genes involved in these disorders, genotype-phenotype correlations are not obvious for FKRP mutations. To date, no homozygous or compound heterozygous null mutations have been identified in FKRP, suggesting that null mutations in FKRP could result in embryonic lethality. We report a family with two siblings carrying a homozygous mutation in the start codon of FKRP that is likely to result in a loss of functional FKRP protein. The clinical phenotype of the patients was consistent with Walker-Warburg syndrome, the most severe disorder in the disease spectrum of dystroglycanopathies.
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Affiliation(s)
- J Van Reeuwijk
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Abstract
The muscular dystrophies are a group of neuromuscular disorders associated with muscle weakness and wasting, which in many forms can lead to loss of ambulation and premature death. A number of muscular dystrophies are associated with loss of proteins required for the maintenance of muscle membrane integrity, in particular with proteins that comprise the dystrophin-associated glycoprotein (DAG) complex. Proper glycosylation of O-linked mannose chains on alpha-dystroglycan, a DAG member, is required for the binding of the extracellular matrix to dystroglycan and for proper DAG function. A number of congenital disorders of glycosylation have now been described where alpha-dystroglycan glycosylation is altered and where muscular dystrophy is a predominant phenotype. Glycosylation is also increasingly being appreciated as a genetic modifier of disease phenotypes in many forms of muscular dystrophy and as a target for the development of new therapies. Here we will review the mouse models available for the study of this group of diseases and outline the methodologies required to describe disease phenotypes.
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