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Hu H, Li J, Gagen CS, Gray NW, Zhang Z, Qi Y, Zhang P. Conditional knockout of protein O-mannosyltransferase 2 reveals tissue-specific roles of O-mannosyl glycosylation in brain development. J Comp Neurol 2011; 519:1320-37. [PMID: 21452199 DOI: 10.1002/cne.22572] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The meninges produce essential signaling molecules and major protein components of the pial basement membrane during normal brain development. Disruptions in the pial basement membrane underlie neural ectopia seen in those congenital muscular dystrophies (CMDs) caused by mutations in genes involved in O-mannosyl glycosylation. In mammals, biosynthesis of O-mannosyl glycans is initiated by a complex of mutually indispensable protein O-mannosyltransferases 1 and 2 (POMT1 and 2). To study the roles of O-mannosylation in brain development we generated a conditional allele of POMT2. POMT2 nulllizygosity resulted in embryonic lethality because of a defective Reichert's membrane. Brain-specific deletion of POMT2 resulted in hypoglycosylation of α-dystroglycan (DG) and abolished laminin binding activity. The effect of POMT2 deletion on brain development was dependent on timing, as earlier deletion resulted in more severe phenotypes. Multiple brain malformations including overmigration of neocortical neurons and migration failure of granule cells in the cerebellum were observed. Immunofluorescence staining and transmission electron microscopy revealed that these migration defects were closely associated with disruptions in the pial basement membrane. Interestingly, POMT2 deletion in the meninges (and blood vessels) did not disrupt the development of the neocortex. Thus, normal brain development requires protein O-mannosylation activity in neural tissue but not the meninges. These results suggest that gene therapy should be directed to the neural tissue instead of the meninges.
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Affiliation(s)
- Huaiyu Hu
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, New York 13210, USA.
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202
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Saito F, Saito-Arai Y, Nakamura-Okuma A, Ikeda M, Hagiwara H, Masaki T, Shimizu T, Matsumura K. Secretion of N-terminal domain of α-dystroglycan in cerebrospinal fluid. Biochem Biophys Res Commun 2011; 411:365-9. [PMID: 21741360 DOI: 10.1016/j.bbrc.2011.06.150] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 06/23/2011] [Indexed: 11/20/2022]
Abstract
α-Dystroglycan (α-DG) plays crucial roles in maintaining the stability of cells. We demonstrated previously that the N-terminal domain of α-DG (α-DG-N) is secreted by cultured cells into the culture medium. In the present study, to clarify its function in vivo, we generated a monoclonal antibody against α-DG-N and investigated the secretion of α-DG-N in human cerebrospinal fluid (CSF). Interestingly, we found that a considerable amount of α-DG-N was present in CSF. α-DG-N in CSF was a sialylated glycoprotein with both N- and O-linked glycan. These observations suggest that secreted α-DG-N may be transported via CSF and have yet unidentified effects on the nervous system.
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Affiliation(s)
- Fumiaki Saito
- Department of Neurology, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan.
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203
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Labelle-Dumais C, Dilworth DJ, Harrington EP, de Leau M, Lyons D, Kabaeva Z, Manzini MC, Dobyns WB, Walsh CA, Michele DE, Gould DB. COL4A1 mutations cause ocular dysgenesis, neuronal localization defects, and myopathy in mice and Walker-Warburg syndrome in humans. PLoS Genet 2011; 7:e1002062. [PMID: 21625620 PMCID: PMC3098190 DOI: 10.1371/journal.pgen.1002062] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 03/18/2011] [Indexed: 01/10/2023] Open
Abstract
Muscle-eye-brain disease (MEB) and Walker Warburg Syndrome (WWS) belong to a spectrum of autosomal recessive diseases characterized by ocular dysgenesis, neuronal migration defects, and congenital muscular dystrophy. Until now, the pathophysiology of MEB/WWS has been attributed to alteration in dystroglycan post-translational modification. Here, we provide evidence that mutations in a gene coding for a major basement membrane protein, collagen IV alpha 1 (COL4A1), are a novel cause of MEB/WWS. Using a combination of histological, molecular, and biochemical approaches, we show that heterozygous Col4a1 mutant mice have ocular dysgenesis, neuronal localization defects, and myopathy characteristic of MEB/WWS. Importantly, we identified putative heterozygous mutations in COL4A1 in two MEB/WWS patients. Both mutations occur within conserved amino acids of the triple-helix-forming domain of the protein, and at least one mutation interferes with secretion of the mutant proteins, resulting instead in intracellular accumulation. Expression and posttranslational modification of dystroglycan is unaltered in Col4a1 mutant mice indicating that COL4A1 mutations represent a distinct pathogenic mechanism underlying MEB/WWS. These findings implicate a novel gene and a novel mechanism in the etiology of MEB/WWS and expand the clinical spectrum of COL4A1-associated disorders. Muscle-eye-brain disease (MEB) and Walker-Warburg Syndrome (WWS) are devastating childhood diseases that belong to a subgroup of congenital muscular dystrophies (CMDs) characterized by ocular dysgenesis, neuronal migration defects, and congenital myopathy. Genetic studies have revealed a number of genes involved in the etiology of CMDs, and subsequent studies show that alterations in dystroglycan glycosylation underlie MEB/WWS. However, over half of MEB/WWS patients do not have mutations in known genes encoding glycosyltransferases, suggesting that other genes are involved. Here, we describe a novel and genetically complex mouse model for MEB/WWS and identify putative heterozygous mutations in COL4A1 in two MEB/WWS patients. We identify a novel gene implicated in the etiology of MEB/WWS, provide evidence of mechanistic heterogeneity for this subgroup of congenital muscular dystrophies, and develop an assay to test the functional significance of putative COL4A1 mutations. Our findings represent the first evidence for a dominant mutation leading to MEB/WWS–like diseases and expand the spectrum of clinical disorders resulting from Col4a1/COL4A1 mutations.
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Affiliation(s)
- Cassandre Labelle-Dumais
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - David J. Dilworth
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - Emily P. Harrington
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - Michelle de Leau
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - David Lyons
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
| | - Zhyldyz Kabaeva
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - M. Chiara Manzini
- Division of Genetics and The Manton Center for Orphan Disease Research, Children's Hospital Boston, Howard Hughes Medical Institute, and Harvard Medical School, Boston, Massachusetts, United States of America
| | - William B. Dobyns
- Departments of Human Genetics, Neurology, and Pediatrics, University of Chicago, Chicago, Illinois, United States of America
| | - Christopher A. Walsh
- Division of Genetics and The Manton Center for Orphan Disease Research, Children's Hospital Boston, Howard Hughes Medical Institute, and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Daniel E. Michele
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Douglas B. Gould
- Departments of Ophthalmology and Anatomy, Institute for Human Genetics, University of California San Francisco School of Medicine, San Francisco, California, United States of America
- * E-mail:
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204
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Zhang Z, Zhang P, Hu H. LARGE expression augments the glycosylation of glycoproteins in addition to α-dystroglycan conferring laminin binding. PLoS One 2011; 6:e19080. [PMID: 21533062 PMCID: PMC3080415 DOI: 10.1371/journal.pone.0019080] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2010] [Accepted: 03/27/2011] [Indexed: 12/03/2022] Open
Abstract
Mutations in genes encoding glycosyltransferases (and presumed glycosyltransferases) that affect glycosylation and extracellular matrix binding activity of α-dystroglycan (α-DG) cause congenital muscular dystrophies (CMDs) with central nervous system manifestations. Among the identified genes, LARGE is of particular interest because its overexpression rescues glycosylation defects of α-DG in mutations of not only LARGE but also other CMD-causing genes and restores laminin binding activity of α-DG. It is not known whether LARGE protein glycosylates other proteins in addition to α-DG. In this study, we overexpressed LARGE in DG-deficient cells and analyzed glycosylated proteins by Western blot analysis. Surprisingly, overexpression of LARGE in α-DG-deficient cells led to glycosylation dependent IIH6C4 and VIA4-1 immunoreactivity, despite the prevailing view that these antibodies only recognize glycosylated α-DG. Furthermore, the hyperglycosylated proteins in LARGE-overexpressing cells demonstrated the functional capacity to bind the extracellular matrix molecule laminin and promote laminin assembly at the cell surface, an effect that was blocked by IIH6C4 antibodies. These results indicate that overexpression of LARGE catalyzes the glycosylation of at least one other glycoprotein in addition to α-DG, and that this glycosylation(s) promotes laminin binding activity.
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Affiliation(s)
- Zhen Zhang
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, New York, United States of America
| | - Peng Zhang
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, New York, United States of America
| | - Huaiyu Hu
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, New York, United States of America
- * E-mail:
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205
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Takahashi H, Kanesaki H, Igarashi T, Kameya S, Yamaki K, Mizota A, Kudo A, Miyagoe-Suzuki Y, Takeda S, Takahashi H. Reactive gliosis of astrocytes and Müller glial cells in retina of POMGnT1-deficient mice. Mol Cell Neurosci 2011; 47:119-30. [PMID: 21447391 DOI: 10.1016/j.mcn.2011.03.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 03/05/2011] [Accepted: 03/21/2011] [Indexed: 11/19/2022] Open
Abstract
Protein O-linked mannose beta1, 2-N-acetylglucosaminyltransferase 1 (POMGnT1) is an enzyme that catalyzes the transfer of N-acetylglucosamine to O-mannose of glycoproteins. Alpha-dystroglycan, a substrate of POMGnT1, is concentrated around the blood vessels, in the outer plexiform layer (OPL), and in the inner limiting membrane (ILM) of the retina. Mutations of the POMGnT1 gene in humans cause muscle-eye-brain (MEB) disease. Several ocular abnormalities including retinal dysplasia, ERG abnormalities, and retinal detachments have been reported in patients with MEB. We have analyzed the eyes of POMGnT1-deficient mice, generated by standard gene targeting technique, to study the retinal abnormalities. Clinical examination of adult mutant mice revealed a high incidence (81% by 12-months-of-age) of retinal detachments. Sheathing of the retinal vessels and the presence of ectopic fibrous tissues around the optic nerve head were also found. Histological examinations showed focal retinal detachment associated with GFAP immunopositivity. The ILM of the mutant mice was disrupted with ectopic cells near the disruptions. The expression of Dp71, a shorter isoform of dystrophin, was severely reduced in the ILM and around retinal blood vessels of POMGnT1-deficient mice. The expression of Dp427, Dp260, Dp140 were also reduced in the OPL of the mutant mice. Electroretinographic (ERG) analyses showed reduced a- and b-wave amplitudes. Examinations of flat mounts revealed abnormal vascular network associated with highly irregular astrocytic processes. In addition, ER-TR7-positive fibrous tissue was found closely associated with reactive astrocytes especially around the optic nerve head. Our results suggest that altered glycosylation of alpha-DG may be responsible for the reactive gliosis and reticular fibrosis in the retina, and the subsequent developments of retinal dysplasia, abnormal ERGs, and retinal detachment in the mutant mice.
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Affiliation(s)
- Hisatomo Takahashi
- Department of Ophthalmology, Nippon Medical School Chiba Hokusoh Hospital, 1715 Kamagari, Inzai, Chiba 270-1694, Japan
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206
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Stalnaker SH, Aoki K, Lim JM, Porterfield M, Liu M, Satz JS, Buskirk S, Xiong Y, Zhang P, Campbell KP, Hu H, Live D, Tiemeyer M, Wells L. Glycomic analyses of mouse models of congenital muscular dystrophy. J Biol Chem 2011; 286:21180-90. [PMID: 21460210 DOI: 10.1074/jbc.m110.203281] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dystroglycanopathies are a subset of congenital muscular dystrophies wherein α-dystroglycan (α-DG) is hypoglycosylated. α-DG is an extensively O-glycosylated extracellular matrix-binding protein and a key component of the dystrophin-glycoprotein complex. Previous studies have shown α-DG to be post-translationally modified by both O-GalNAc- and O-mannose-initiated glycan structures. Mutations in defined or putative glycosyltransferase genes involved in O-mannosylation are associated with a loss of ligand-binding activity of α-DG and are causal for various forms of congenital muscular dystrophy. In this study, we sought to perform glycomic analysis on brain O-linked glycan structures released from proteins of three different knock-out mouse models associated with O-mannosylation (POMGnT1, LARGE (Myd), and DAG1(-/-)). Using mass spectrometry approaches, we were able to identify nine O-mannose-initiated and 25 O-GalNAc-initiated glycan structures in wild-type littermate control mouse brains. Through our analysis, we were able to confirm that POMGnT1 is essential for the extension of all observed O-mannose glycan structures with β1,2-linked GlcNAc. Loss of LARGE expression in the Myd mouse had no observable effect on the O-mannose-initiated glycan structures characterized here. Interestingly, we also determined that similar amounts of O-mannose-initiated glycan structures are present on brain proteins from α-DG-lacking mice (DAG1) compared with wild-type mice, indicating that there must be additional proteins that are O-mannosylated in the mammalian brain. Our findings illustrate that classical β1,2-elongation and β1,6-GlcNAc branching of O-mannose glycan structures are dependent upon the POMGnT1 enzyme and that O-mannosylation is not limited solely to α-DG in the brain.
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Affiliation(s)
- Stephanie H Stalnaker
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602-4712, USA
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207
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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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208
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Hara Y, Balci-Hayta B, Yoshida-Moriguchi T, Kanagawa M, Beltrán-Valero de Bernabé D, Gündeşli H, Willer T, Satz JS, Crawford RW, Burden SJ, Kunz S, Oldstone MBA, Accardi A, Talim B, Muntoni F, Topaloğlu H, Dinçer P, Campbell KP. A dystroglycan mutation associated with limb-girdle muscular dystrophy. N Engl J Med 2011; 364:939-46. [PMID: 21388311 PMCID: PMC3071687 DOI: 10.1056/nejmoa1006939] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dystroglycan, which serves as a major extracellular matrix receptor in muscle and the central nervous system, requires extensive O-glycosylation to function. We identified a dystroglycan missense mutation (Thr192→Met) in a woman with limb-girdle muscular dystrophy and cognitive impairment. A mouse model harboring this mutation recapitulates the immunohistochemical and neuromuscular abnormalities observed in the patient. In vitro and in vivo studies showed that the mutation impairs the receptor function of dystroglycan in skeletal muscle and brain by inhibiting the post-translational modification, mediated by the glycosyltransferase LARGE, of the phosphorylated O-mannosyl glycans on α-dystroglycan that is required for high-affinity binding to laminin.
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Affiliation(s)
- Yuji Hara
- Department of Molecular Physiology and Biophysics, University of Iowa Roy J and Lucille A Carver College of Medicine, Iowa City, USA
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209
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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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210
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Hu Y, Li ZF, Wu X, Lu Q. Large induces functional glycans in an O-mannosylation dependent manner and targets GlcNAc terminals on alpha-dystroglycan. PLoS One 2011; 6:e16866. [PMID: 21347376 PMCID: PMC3036717 DOI: 10.1371/journal.pone.0016866] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Accepted: 01/17/2011] [Indexed: 11/19/2022] Open
Abstract
Alpha-dystroglycan (α-DG) is a ubiquitously expressed receptor for extracellular matrix proteins and some viruses, and plays a pivotal role in a number of pathological events, including cancer progression, muscular dystrophies, and viral infection. The O-glycans on α-DG are essential for its ligand binding, but the biosynthesis of the functional O-glycans remains obscure. The fact that transient overexpression of LARGE, a putative glycosyltransferase, up-regulates the functional glycans on α-DG to mediate its ligand binding implied that overexpression of LARGE may be a novel strategy to treat disorders with hypoglycosylation of α-DG. In this study, we focus on the effects of stable overexpression of Large on α-DG glycosylation in Chinese hamster ovary (CHO) cell and its glycosylation deficient mutants. Surprisingly, stable overexpression of Large in an O-mannosylation null deficient Lec15.2 CHO cells failed to induce the functional glycans on α-DG. Introducing the wild-type DPM2 cDNA, the deficient gene in the Lec15.2 cells, fully restored the Large-induced functional glycosylation, suggesting that Large induces the functional glycans in a DPM2/O-mannosylation dependent manner. Furthermore, stable overexpression of Large can effectively induce functional glycans on N-linked glycans in the Lec8 cells and ldlD cells growing in Gal deficient media, in both of which circumstances galactosylation are deficient. In addition, supplement of Gal to the ldlD cell culture media significantly reduces the amount of functional glycans induced by Large, suggested that galactosylation suppresses Large to induce the functional glycans. Thus our results revealed a mechanism by which Large competes with galactosyltransferase to target GlcNAc terminals to induce the functional glycans on α-DG.
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Affiliation(s)
- Yihong Hu
- Neurology Department, McColl-Lockwood Laboratory for Muscular Dystrophy Research, Cannon Research Center, Carolinas Medical Center, Charlotte, North Carolina, United States of America
| | - Zhi-fang Li
- Neurology Department, McColl-Lockwood Laboratory for Muscular Dystrophy Research, Cannon Research Center, Carolinas Medical Center, Charlotte, North Carolina, United States of America
| | - Xiaohua Wu
- Neurology Department, McColl-Lockwood Laboratory for Muscular Dystrophy Research, Cannon Research Center, Carolinas Medical Center, Charlotte, North Carolina, United States of America
- * E-mail:
| | - Qilong Lu
- Neurology Department, McColl-Lockwood Laboratory for Muscular Dystrophy Research, Cannon Research Center, Carolinas Medical Center, Charlotte, North Carolina, United States of America
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211
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What disorders of cortical development tell us about the cortex: one plus one does not always make two. Curr Opin Genet Dev 2011; 21:333-9. [PMID: 21288712 PMCID: PMC3139684 DOI: 10.1016/j.gde.2011.01.006] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 12/29/2010] [Accepted: 01/04/2011] [Indexed: 12/31/2022]
Abstract
The unique size and complexity of the human cerebral cortex are achieved via a long and precisely regulated developmental process controlling neurogenesis, neuronal migration and differentiation. Traditionally, disorders of cortical development have been classified on the basis of the most obvious defects in one of these developmental steps. However, the more we learn about the cellular biological roles of genes that are essential for cortical development, the more we realize that these functions map onto molecular processes, but not so cleanly onto anatomical processes. Essential genes might be involved in both proliferation and migration as well as differentiation, reflecting roles for underlying molecular mechanisms in different phases of development and causing a stunning variety of cortical defects.
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212
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Abstract
During the last 10 years it has become apparent that a significant subset of inherited muscular dystrophy is caused by errors in the glycosylation of α-dystroglycan. Many of these dystrophies are also associated with abnormalities of the central nervous system. Dystroglycan has to be fully glycosylated in order bind to its ligands. To date, six genes have been shown to be essential for functional dystroglycan glycosylation and most, if not all, of these genes act in the formation of O-mannosyl glycans. Genetic heterogeneity indicates that other genes are involved in this pathway. Identification of these additional genes would increase our understanding of this specific and essential glycosylation pathway.
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213
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Dwyer ND, Manning DK, Moran JL, Mudbhary R, Fleming MS, Favero CB, Vock VM, O'Leary DDM, Walsh CA, Beier DR. A forward genetic screen with a thalamocortical axon reporter mouse yields novel neurodevelopment mutants and a distinct emx2 mutant phenotype. Neural Dev 2011; 6:3. [PMID: 21214893 PMCID: PMC3024922 DOI: 10.1186/1749-8104-6-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 01/07/2011] [Indexed: 12/02/2022] Open
Abstract
Background The dorsal thalamus acts as a gateway and modulator for information going to and from the cerebral cortex. This activity requires the formation of reciprocal topographic axon connections between thalamus and cortex. The axons grow along a complex multistep pathway, making sharp turns, crossing expression boundaries, and encountering intermediate targets. However, the cellular and molecular components mediating these steps remain poorly understood. Results To further elucidate the development of the thalamocortical system, we first created a thalamocortical axon reporter line to use as a genetic tool for sensitive analysis of mutant mouse phenotypes. The TCA-tau-lacZ reporter mouse shows specific, robust, and reproducible labeling of thalamocortical axons (TCAs), but not the overlapping corticothalamic axons, during development. Moreover, it readily reveals TCA pathfinding abnormalities in known cortical mutants such as reeler. Next, we performed an unbiased screen for genes involved in thalamocortical development using random mutagenesis with the TCA reporter. Six independent mutant lines show aberrant TCA phenotypes at different steps of the pathway. These include ventral misrouting, overfasciculation, stalling at the corticostriatal boundary, and invasion of ectopic cortical cell clusters. An outcross breeding strategy coupled with a genomic panel of single nucleotide polymorphisms facilitated genetic mapping with small numbers of mutant mice. We mapped a ventral misrouting mutant to the Emx2 gene, and discovered that some TCAs extend to the olfactory bulbs in this mutant. Mapping data suggest that other lines carry mutations in genes not previously known for roles in thalamocortical development. Conclusions These data demonstrate the feasibility of a forward genetic approach to understanding mammalian brain morphogenesis and wiring. A robust axonal reporter enabled sensitive analysis of a specific axon tract inside the mouse brain, identifying mutant phenotypes at multiple steps of the pathway, and revealing a new aspect of the Emx2 mutant. The phenotypes highlight vulnerable choice points and latent tendencies of TCAs, and will lead to a refined understanding of the elements and interactions required to form the thalamocortical system. See Commentary: http://www.biomedcentral.com/1741-7007/9/1
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Affiliation(s)
- Noelle D Dwyer
- Howard Hughes Medical Institute, Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA, USA.
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214
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Rivier F, Mercier M, Hugon G, Mornet D, Echenne B. Distrofie muscolari congenite. Neurologia 2011. [DOI: 10.1016/s1634-7072(11)70572-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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215
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216
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Barros CS, Franco SJ, Müller U. Extracellular matrix: functions in the nervous system. Cold Spring Harb Perspect Biol 2011; 3:a005108. [PMID: 21123393 DOI: 10.1101/cshperspect.a005108] [Citation(s) in RCA: 260] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
An astonishing number of extracellular matrix glycoproteins are expressed in dynamic patterns in the developing and adult nervous system. Neural stem cells, neurons, and glia express receptors that mediate interactions with specific extracellular matrix molecules. Functional studies in vitro and genetic studies in mice have provided evidence that the extracellular matrix affects virtually all aspects of nervous system development and function. Here we will summarize recent findings that have shed light on the specific functions of defined extracellular matrix molecules on such diverse processes as neural stem cell differentiation, neuronal migration, the formation of axonal tracts, and the maturation and function of synapses in the peripheral and central nervous system.
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Affiliation(s)
- Claudia S Barros
- The Scripps Research Institute, Department of Cell Biology, Dorris Neuroscience Center, La Jolla, California 92037, USA
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Brockington M, Torelli S, Sharp PS, Liu K, Cirak S, Brown SC, Wells DJ, Muntoni F. Transgenic overexpression of LARGE induces α-dystroglycan hyperglycosylation in skeletal and cardiac muscle. PLoS One 2010; 5:e14434. [PMID: 21203384 PMCID: PMC3010994 DOI: 10.1371/journal.pone.0014434] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Accepted: 12/01/2010] [Indexed: 01/11/2023] Open
Abstract
Background LARGE is one of seven putative or demonstrated glycosyltransferase enzymes defective in a common group of muscular dystrophies with reduced glycosylation of α-dystroglycan. Overexpression of LARGE induces hyperglycosylation of α-dystroglycan in both wild type and in cells from dystroglycanopathy patients, irrespective of their primary gene defect, restoring functional glycosylation. Viral delivery of LARGE to skeletal muscle in animal models of dystroglycanopathy has identical effects in vivo, suggesting that the restoration of functional glycosylation could have therapeutic applications in these disorders. Pharmacological strategies to upregulate Large expression are also being explored. Methodology/Principal Findings In order to asses the safety and efficacy of long term LARGE over-expression in vivo, we have generated four mouse lines expressing a human LARGE transgene. On observation, LARGE transgenic mice were indistinguishable from the wild type littermates. Tissue analysis from young mice of all four lines showed a variable pattern of transgene expression: highest in skeletal and cardiac muscles, and lower in brain, kidney and liver. Transgene expression in striated muscles correlated with α-dystroglycan hyperglycosylation, as determined by immunoreactivity to antibody IIH6 and increased laminin binding on an overlay assay. Other components of the dystroglycan complex and extracellular matrix ligands were normally expressed, and general muscle histology was indistinguishable from wild type controls. Further detailed muscle physiological analysis demonstrated a loss of force in response to eccentric exercise in the older, but not in the younger mice, suggesting this deficit developed over time. However this remained a subclinical feature as no pathology was observed in older mice in any muscles including the diaphragm, which is sensitive to mechanical load-induced damage. Conclusions/Significance This work shows that potential therapies in the dystroglycanopathies based on LARGE upregulation and α-dystroglycan hyperglycosylation in muscle should be safe.
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Affiliation(s)
- Martin Brockington
- Dubowitz Neuromuscular Centre, University College London (UCL) Institute of Child Health and Great Ormond Street Hospital, London, United Kingdom
| | - Silvia Torelli
- Dubowitz Neuromuscular Centre, University College London (UCL) Institute of Child Health and Great Ormond Street Hospital, London, United Kingdom
| | - Paul S. Sharp
- Department of Cellular and Molecular Neuroscience, Imperial College, London, United Kingdom
| | - Ke Liu
- Department of Cellular and Molecular Neuroscience, Imperial College, London, United Kingdom
| | - Sebahattin Cirak
- Dubowitz Neuromuscular Centre, University College London (UCL) Institute of Child Health and Great Ormond Street Hospital, London, United Kingdom
| | - Susan C. Brown
- Department of Veterinary Basic Science, Royal Veterinary College, London, United Kingdom
| | - Dominic J. Wells
- Department of Cellular and Molecular Neuroscience, Imperial College, London, United Kingdom
- Department of Veterinary Basic Science, Royal Veterinary College, London, United Kingdom
| | - Francesco Muntoni
- Dubowitz Neuromuscular Centre, University College London (UCL) Institute of Child Health and Great Ormond Street Hospital, London, United Kingdom
- * E-mail:
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218
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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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219
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Lim BC, Ki CS, Kim JW, Cho A, Kim MJ, Hwang H, Kim KJ, Hwang YS, Park WY, Lim YJ, Kim IO, Lee JS, Chae JH. Fukutin mutations in congenital muscular dystrophies with defective glycosylation of dystroglycan in Korea. Neuromuscul Disord 2010; 20:524-30. [PMID: 20620061 DOI: 10.1016/j.nmd.2010.06.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 05/27/2010] [Accepted: 06/09/2010] [Indexed: 11/18/2022]
Abstract
This study was aimed to identify Fukutin (FKTN)-related congenital muscular dystrophies (CMD) with defective alpha-dystroglycan glycosylation in Korea and to discuss their genotype-phenotype spectrum focusing on detailed brain magnetic resonance imaging (MRI) findings. FKTN mutations were found in nine of the 12 CMD patients with defective alpha-dystroglycan glycosylation patients (75%). Two patients were homozygous for the Japanese founder retrotransposal insertion mutation. Seven patients were heterozygous for the retrotransposal insertion mutation, five of whom carried a novel intronic mutation that activates a pseudoexon between exons 5 and 6 (c.647+2084G>T). Compared with individuals that were homozygous for the retrotransposal insertion mutation, the seven heterozygotes for the retrotransposal insertion mutation, including five patients with the novel pseudoexon mutation, exhibited a more severe clinical phenotype in terms of motor abilities and more extensive brain MRI abnormalities (i.e., a wider distribution of cortical malformation and pons and cerebellar hypoplasia). FKTN mutations are the most common genetic cause of CMD with defective alpha-dystroglycan glycosylation in Korea. Compound heterozygosity of the retrotransposal insertion and the novel pseudoexon mutation is the most prevalent genotype in Korea and is associated with a more severe clinical and radiological phenotype compared with homozygosity for the retrotransposal insertion mutation.
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Affiliation(s)
- Bung Chan Lim
- Department of Pediatrics, Seoul National University Children's Hospital, Seoul National University College of Medicine, Seoul, South Korea
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221
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Abstract
Glycosylation is the most common post-translational modification of proteins. Protein sequence data suggested that more than half of all proteins produced in mammalian cells are glycoproteins. Recent studies showed that glycans of secreted glycoproteins affect many protein properties, such as solubility, stability, protease sensitivity and polarity, whereas glycans on cell-surface glycoproteins are involved in various cellular functions, including cell-cell communication. Accordingly, the investigation of glycoprotein changes caused by aging is expected to help understand the aging process and to elucidate age-associated diseases. The present review will summarize our current knowledge of changes found in brain glycoproteins resulting from the aging process.
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Affiliation(s)
- Yuji Sato
- Molecular Glycobiology, Research Team for Mechanism of Aging, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo, Japan
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222
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Yis U, Uyanik G, Heck PB, Smitka M, Nobel H, Ebinger F, Dirik E, Feng L, Kurul SH, Brocke K, Unalp A, Özer E, Cakmakci H, Sewry C, Cirak S, Muntoni F, Hehr U, Morris-Rosendahl DJ. Fukutin mutations in non-Japanese patients with congenital muscular dystrophy: less severe mutations predominate in patients with a non-Walker-Warburg phenotype. Neuromuscul Disord 2010; 21:20-30. [PMID: 20961758 DOI: 10.1016/j.nmd.2010.08.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 08/27/2010] [Indexed: 11/16/2022]
Abstract
Six genes including POMT1, POMT2, POMGNT1, FKRP, Fukutin (FKTN) and LARGE encode proteins involved in the glycosylation of α-dystroglycan (α-DG). Abnormal glycosylation of α-DG is a common finding in Walker-Warburg syndrome (WWS), muscle-eye-brain disease (MEB), Fukuyama congenital muscular dystrophy (FCMD), congenital muscular dystrophy types 1C and 1D and some forms of autosomal recessive limb-girdle muscular dystrophy (LGMD2I, LGMD2K, LGMD2M), and is associated with mutations in the above genes. FCMD, caused by mutations in Fukutin (FKTN), is most frequent in Japan, but an increasing number of FKTN mutations are being reported outside of Japan. We describe four new patients with FKTN mutations and phenotypes ranging from: severe WWS in a Greek-Croatian patient, to congenital muscular dystrophy and cobblestone lissencephaly resembling MEB-FCMD in two Turkish patients, and limb-girdle muscular dystrophy and no mental retardation in a German patient. Four of the five different FKTN mutations have not been previously described.
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Affiliation(s)
- Uluc Yis
- Gaziantep Children's Hospital, Department of Pediatric Neurology, Gaziantep, Turkey
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223
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Bahi-Buisson N, Poirier K, Boddaert N, Fallet-Bianco C, Specchio N, Bertini E, Caglayan O, Lascelles K, Elie C, Rambaud J, Baulac M, An I, Dias P, des Portes V, Moutard ML, Soufflet C, El Maleh M, Beldjord C, Villard L, Chelly J. GPR56-related bilateral frontoparietal polymicrogyria: further evidence for an overlap with the cobblestone complex. ACTA ACUST UNITED AC 2010; 133:3194-209. [PMID: 20929962 DOI: 10.1093/brain/awq259] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
GPR56 mutations cause an autosomal recessive polymicrogyria syndrome that has distinctive radiological features combining bilateral frontoparietal polymicrogyria, white matter abnormalities and cerebellar hypoplasia. Recent investigations of a GPR56 knockout mouse model suggest that bilateral bifrontoparietal polymicrogyria shares some features of the cobblestone brain malformation and demonstrate that loss of GPR56 leads to a dysregulation of the maintenance of the pial basement membrane integrity in the forebrain and the rostral cerebellum. In light of these findings and other data in the literature, this study aimed to refine the clinical features with the first description of a foetopathological case and to define the range of cobblestone-like features in GPR56 bilateral bifrontoparietal polymicrogyria in a sample of 14 patients. We identified homozygous GPR56 mutations in 14 patients from eight consanguineous families with typical bilateral bifrontoparietal polymicrogyria and in one foetal case, out of 30 patients with bifrontoparietal polymicrogyria referred for molecular screening. The foetal case, which was terminated at 35 weeks of gestation in view of suspicion of Walker Warburg syndrome, showed a cobblestone-like lissencephaly with a succession of normal, polymicrogyric and 'cobblestone-like' cortex with ectopic neuronal overmigration, agenesis of the cerebellar vermis and hypoplastic cerebellar hemispheres with additional neuronal overmigration in the pons and the cerebellar cortex. The 14 patients with GPR56 mutations (median 8.25 years, range 1.5-33 years) were phenotypically homogeneous with a distinctive clinical course characterized by pseudomyopathic behaviour at onset that subsequently evolved into severe mental and motor retardation. Generalized seizures (12/14) occurred later with onset ranging from 2.5 to 10 years with consistent electroencephalogram findings of predominantly anterior bursts of low amplitude α-like activity. Neuroimaging demonstrated a common phenotype with bilateral frontoparietally predominant polymicrogyria (13/13), cerebellar dysplasia with cysts mainly affecting the superior vermis (11/13) and patchy to diffuse myelination abnormalities (13/13). Additionally, the white matter abnormalities showed a peculiar evolution from severe hypomyelination at 4 months to patchy lesions later in childhood. Taken as a whole, these observations collectively demonstrate that GPR56 bilateral bifrontoparietal polymicrogyria combines all the features of a cobblestone-like lissencephaly and also suggest that GRP56-related defects produce a phenotypic continuum ranging from bilateral bifrontoparietal polymicrogyria to cobblestone-like lissencephaly.
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Affiliation(s)
- Nadia Bahi-Buisson
- Service de Neurologie pédiatrique, Assistance Publique-Hôpitaux de Paris (AP-HP), hôpital Necker, Paris, France.
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224
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Kanagawa M, Omori Y, Sato S, Kobayashi K, Miyagoe-Suzuki Y, Takeda S, Endo T, Furukawa T, Toda T. Post-translational maturation of dystroglycan is necessary for pikachurin binding and ribbon synaptic localization. J Biol Chem 2010; 285:31208-16. [PMID: 20682766 DOI: 10.1074/jbc.m110.116343] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pikachurin, the most recently identified ligand of dystroglycan, plays a crucial role in the formation of the photoreceptor ribbon synapse. It is known that glycosylation of dystroglycan is necessary for its ligand binding activity, and hypoglycosylation is associated with a group of muscular dystrophies that often involve eye abnormalities. Because little is known about the interaction between pikachurin and dystroglycan and its impact on molecular pathogenesis, here we characterize the interaction using deletion constructs and mouse models of muscular dystrophies with glycosylation defects (Large(myd) and POMGnT1-deficient mice). Pikachurin-dystroglycan binding is calcium-dependent and relatively less sensitive to inhibition by heparin and high NaCl concentration, as compared with other dystroglycan ligand proteins. Using deletion constructs of the laminin globular domains in the pikachurin C terminus, we show that a certain steric structure formed by the second and the third laminin globular domains is necessary for the pikachurin-dystroglycan interaction. Binding assays using dystroglycan deletion constructs and tissue samples from Large-deficient (Large(myd)) mice show that Large-dependent modification of dystroglycan is necessary for pikachurin binding. In addition, the ability of pikachurin to bind to dystroglycan prepared from POMGnT1-deficient mice is severely reduced, suggesting that modification of the GlcNAc-β1,2-branch on O-mannose is also necessary for the interaction. Immunofluorescence analysis reveals a disruption of pikachurin localization in the photoreceptor ribbon synapse of these model animals. Together, our data demonstrate that post-translational modification on O-mannose, which is mediated by Large and POMGnT1, is essential for pikachurin binding and proper localization, and suggest that their disruption underlies the molecular pathogenesis of eye abnormalities in a group of muscular dystrophies.
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Affiliation(s)
- Motoi Kanagawa
- Division of Neurology/Molecular Brain Science, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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225
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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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226
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Hu H, Candiello J, Zhang P, Ball SL, Cameron DA, Halfter W. Retinal ectopias and mechanically weakened basement membrane in a mouse model of muscle-eye-brain (MEB) disease congenital muscular dystrophy. Mol Vis 2010; 16:1415-28. [PMID: 20680099 PMCID: PMC2913139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Accepted: 07/23/2010] [Indexed: 10/28/2022] Open
Abstract
PURPOSE Some forms of congenital muscular dystrophy are associated with cortical and retinal dysplasias. Protein O-mannose N-acetylglucosaminyltransferase 1 (POMGnT1) knockout mice, one of the mouse models of muscular dystrophy, exhibit a thinner retina with reduced density of retinal ganglion cells. This study is aimed to further characterize the knockout retina, with special emphasis on the inner limiting membrane, the basement membrane of the retina. METHODS Immunofluorescence staining and transmission electron microscopy were used to analyze the retinas. Atomic force microscopy was performed on the inner limiting membrane preparations to examine their mechanical properties. RESULTS The inner limiting membrane of the knockout mice exhibited frequent breaks with protrusions of the Müller glial processes and ectopic placement of retinal ganglion cells into the vitreous humor. Disruptions in inner limiting membrane integrity developmentally precede the cellular abnormalities. Regions of disrupted inner limiting membrane were also associated with molecular abnormalities of Müller glia that included diminished presence of the integral membrane proteins Kir4.1 (an inwardly rectifying potassium channel) and aquaporin-4. When measured with atomic force microscopy, the POMGnT1 knockout mouse inner limiting membrane (ILM) exhibited significantly reduced Young's modulus and is therefore mechanically weaker than the ILM from controls. CONCLUSIONS Deficiency of POMGnT1-mediated glycosylation of dystroglycan is implicated in reduced stiffness of the ILM. The weakened ILM results in the disruption of the membrane and subsequent reduction in retinal integrity.
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Affiliation(s)
- Huaiyu Hu
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY
| | - Joseph Candiello
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA
| | - Peng Zhang
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY
| | - Sherry L. Ball
- Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH
| | - David A. Cameron
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY
| | - Willi Halfter
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA
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227
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Ueyama M, Akimoto Y, Ichimiya T, Ueda R, Kawakami H, Aigaki T, Nishihara S. Increased apoptosis of myoblasts in Drosophila model for the Walker-Warburg syndrome. PLoS One 2010; 5:e11557. [PMID: 20644630 PMCID: PMC2903483 DOI: 10.1371/journal.pone.0011557] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Accepted: 06/17/2010] [Indexed: 11/18/2022] Open
Abstract
Walker-Warburg syndrome, a progressive muscular dystrophy, is a severe disease with various kinds of symptoms such as muscle weakness and occasional seizures. The genes of protein O-mannosyltransferases 1 and 2 (POMT1 and POMT2), fukutin, and fukutin-related protein are responsible for this syndrome. In our previous study, we cloned Drosophila orthologs of human POMT1 and POMT2 and identified their activity. However, the mechanism of onset of this syndrome is not well understood. Furthermore, little is known about the behavioral properties of the Drosophila POMT1 and POMT2 mutants, which are called rotated abdomen (rt) and twisted (tw), respectively. First, we performed various kinds of behavioral tests and described in detail the muscle structures by using these mutants. The mutant flies exhibited abnormalities in heavy exercises such as climbing or flight but not in light movements such as locomotion. Defective motor function in mutants appeared immediately after eclosion and was exaggerated with aging. Along with motor function, muscle ultrastructure in the tw mutant was altered, as seen in human patients. We demonstrated that expression of RNA interference (RNAi) for the rt gene and the tw mutant was almost completely lethal and semi-lethal, respectively. Flies expressing RNAi had reduced lifespans. These findings clearly demonstrate that Drosophila POMT mutants are models for human muscular dystrophy. We then observed a high density of myoblasts with an enhanced degree of apoptosis in the tw mutant, which completely lost enzymatic activity. In this paper, we propose a novel mechanism for the development of muscular dystrophy: POMT mutation causes high myoblast density and position derangement, which result in apoptosis, muscle disorganization, and muscle cell defects.
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Affiliation(s)
- Morio Ueyama
- Department of Bioinformatics, Soka University, Hachioji, Tokyo, Japan
| | - Yoshihiro Akimoto
- Department of Anatomy, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Tomomi Ichimiya
- Department of Bioinformatics, Soka University, Hachioji, Tokyo, Japan
| | - Ryu Ueda
- Invertebrate Genetics Laboratory, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Hayato Kawakami
- Department of Anatomy, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Toshiro Aigaki
- Department of Biological Science, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Shoko Nishihara
- Department of Bioinformatics, Soka University, Hachioji, Tokyo, Japan
- * E-mail:
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228
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Avsar-Ban E, Ishikawa H, Manya H, Watanabe M, Akiyama S, Miyake H, Endo T, Tamaru Y. Protein O-mannosylation is necessary for normal embryonic development in zebrafish. Glycobiology 2010; 20:1089-102. [PMID: 20466645 DOI: 10.1093/glycob/cwq069] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Two distinct cDNAs corresponding to two zebrafish protein O-mannosyltransferase genes, zPOMT1 and zPOMT2, were cloned from early developmental embryos. Gene expression analysis revealed that zPOMT1 and zPOMT2 were expressed in similar patterns during early embryonic development and in all adult tissues. To study the regulation of zPOMT1 and zPOMT2 mRNA distribution during zebrafish embryogenesis, we injected enhanced green fluorescent protein (EGFP) mRNA fused to the 3'untranslated regions of each zPOMT gene. The distribution of EGFP resulting from the two constructs was similar. Injection of antisense morpholino oligonucleotides of zPOMT1 and zPOMT2 resulted in several severe phenotypes-including bended body, edematous pericaridium and abnormal eye pigmentation. Immunohistochemistry using anti-glycosylated alpha-dystroglycan antibody (IIH6) and morphological analysis revealed that the phenotypes of zPOMT2 knockdown were more severe than those of zPOMT1 knockdown, even though the IIH6 reactivity was lost in both zPOMT1 and zPOMT2 morphants. Finally, only when both zPOMT1 and zPOMT2 were expressed in human embryonic kidney 293T cells were high levels of protein O-mannosyltransferase activity detected, indicating that both zPOMT1 and zPOMT2 were required for full enzymatic activity. Moreover, either heterologous combination, zPOMT1 and human POMT2 (hPOMT2) or hPOMT1 and zPOMT2, resulted in enzymatic activity in cultured cells. These results indicate that the protein O-mannosyltransferase machinery in zebrafish and humans is conserved and suggest that zebrafish may be useful for functional studies of protein O-mannosylation.
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Affiliation(s)
- Eriko Avsar-Ban
- Department of Life Science, Mie University Graduate School of Bioresources, 1577 Kurimamachiya, Tsu, Mie 514-8507, Japan
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229
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Reed UC. Congenital muscular dystrophy. Part II: a review of pathogenesis and therapeutic perspectives. ARQUIVOS DE NEURO-PSIQUIATRIA 2010; 67:343-62. [PMID: 19547838 DOI: 10.1590/s0004-282x2009000200035] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 03/14/2009] [Indexed: 11/22/2022]
Abstract
The congenital muscular dystrophies (CMDs) are a group of genetically and clinically heterogeneous hereditary myopathies with preferentially autosomal recessive inheritance, that are characterized by congenital hypotonia, delayed motor development and early onset of progressive muscle weakness associated with dystrophic pattern on muscle biopsy. The clinical course is broadly variable and can comprise the involvement of the brain and eyes. From 1994, a great development in the knowledge of the molecular basis has occurred and the classification of CMDs has to be continuously up dated. In the last number of this journal, we presented the main clinical and diagnostic data concerning the different subtypes of CMD. In this second part of the review, we analyse the main reports from the literature concerning the pathogenesis and the therapeutic perspectives of the most common subtypes of CMD: MDC1A with merosin deficiency, collagen VI related CMDs (Ullrich and Bethlem), CMDs with abnormal glycosylation of alpha-dystroglycan (Fukuyama CMD, Muscle-eye-brain disease, Walker Warburg syndrome, MDC1C, MDC1D), and rigid spine syndrome, another much rare subtype of CMDs not related with the dystrophin/glycoproteins/extracellular matrix complex.
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230
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Nakamura N, Lyalin D, Panin VM. Protein O-mannosylation in animal development and physiology: from human disorders to Drosophila phenotypes. Semin Cell Dev Biol 2010; 21:622-30. [PMID: 20362685 DOI: 10.1016/j.semcdb.2010.03.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 03/10/2010] [Accepted: 03/25/2010] [Indexed: 12/13/2022]
Abstract
Protein O-mannosylation has a profound effect on the development and physiology of mammalian organisms. Mutations in genes affecting O-mannosyl glycan biosynthesis result in congenital muscular dystrophies. The main pathological mechanism triggered by O-mannosylation defects is a compromised interaction of cells with the extracellular matrix due to abnormal glycosylation of alpha-dystroglycan. Hypoglycosylation of alpha-dystroglycan impairs its ligand-binding activity and results in muscle degeneration and failure of neuronal migration. Recent experiments revealed the existence of compensatory mechanisms that could ameliorate defects of O-mannosylation. However, these mechanisms remain poorly understood. O-mannosylation and dystroglycan pathway genes show remarkable evolutionary conservation in a wide range of metazoans. Mutations and downregulation of these genes in zebrafish and Drosophila result in muscle defects and degeneration, also causing neurological phenotypes, which suggests that O-mannosylation has similar functions in mammals and lower animals. Thus, future studies in genetically tractable model organisms, such as zebrafish and Drosophila, should help to reveal molecular and genetic mechanisms of mammalian O-mannosylation and its role in the regulation of dystroglycan function.
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Affiliation(s)
- Naosuke Nakamura
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, 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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232
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Yoshida-Moriguchi T, Yu L, Stalnaker SH, Davis S, Kunz S, Madson M, Oldstone MBA, Schachter H, Wells L, Campbell KP. O-mannosyl phosphorylation of alpha-dystroglycan is required for laminin binding. Science 2010; 327:88-92. [PMID: 20044576 DOI: 10.1126/science.1180512] [Citation(s) in RCA: 259] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Alpha-dystroglycan (alpha-DG) is a cell-surface glycoprotein that acts as a receptor for both extracellular matrix proteins containing laminin-G domains and certain arenaviruses. Receptor binding is thought to be mediated by a posttranslational modification, and defective binding with laminin underlies a subclass of congenital muscular dystrophy. Using mass spectrometry- and nuclear magnetic resonance (NMR)-based structural analyses, we identified a phosphorylated O-mannosyl glycan on the mucin-like domain of recombinant alpha-DG, which was required for laminin binding. We demonstrated that patients with muscle-eye-brain disease and Fukuyama congenital muscular dystrophy, as well as mice with myodystrophy, commonly have defects in a postphosphoryl modification of this phosphorylated O-linked mannose, and that this modification is mediated by the like-acetylglucosaminyltransferase (LARGE) protein. These findings expand our understanding of the mechanisms that underlie congenital muscular dystrophy.
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Affiliation(s)
- Takako Yoshida-Moriguchi
- Howard Hughes Medical Institute, University of Iowa Roy J. and Lucille A. Carver College of Medicine, 4283 Carver Biomedical Research Building, 285 Newton Road, Iowa City, IA 52242-1101, USA
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233
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Xiong H, Wang S, Kobayashi K, Jiang Y, Wang J, Chang X, Yuan Y, Liu J, Toda T, Fukuyama Y, Wu X. Fukutin gene retrotransposal insertion in a non-Japanese Fukuyama congenital muscular dystrophy (FCMD) patient. Am J Med Genet A 2010; 149A:2403-8. [PMID: 19842201 DOI: 10.1002/ajmg.a.33057] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Fukuyama-type congenital muscular dystrophy (FCMD) is an autosomal recessive disorder, characterized by severe muscular dystrophy associated with brain malformation. FCMD is the second most common form of muscular dystrophy and one of the most common autosomal recessive diseases among the Japanese population; however, no typical FCMD cases have been reported in any other population. In this study, we report on the first identification of a Chinese FCMD patient; our findings are supported by clinical, histological, and magnetic resonance imaging (MRI) evidence, as well as fukutin gene mutational analyses. The patient presented with neonatal hypotonia, seizures, and delayed motor and speech development. Additional testing revealed cerebral and cerebellar gyrus abnormalities with white matter signal intensity changes, elevated serum creatine kinase (CK) levels, and dystrophic skeletal muscle with alpha-dystroglycan hypoglycosylation, and normal beta-dystroglycan and merosin expression. Genetic analysis of the fukutin gene showed one copy with a Japanese founder 3-kilobase (kb) retrotransposal insertion in the 3'-non-coding region and the other copy with a known c.139C>T mutation. This is the first FCMD case reported in the Chinese population and the first case in which the 3-kb insertion has been found outside of the Japanese population. This report emphasizes the importance of considering the fukutin founder mutation for diagnostic purposes outside of Japan.
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Affiliation(s)
- Hui Xiong
- Department of Pediatrics, Peking University First Hospital, Beijing, China.
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234
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Fang W, Ding W, Wang B, Zhou H, Ouyang H, Ming J, Jin C. Reduced expression of the O-mannosyltransferase 2 (AfPmt2) leads to deficient cell wall and abnormal polarity in Aspergillus fumigatus. Glycobiology 2010; 20:542-52. [PMID: 20053626 DOI: 10.1093/glycob/cwp206] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Protein O-mannosyltransferases (PMTs) initiate O-mannosylation of secretory proteins, which are of fundamental importance in eukaryotes. The human fungal pathogen Aspergillus fumigatus possesses three genes encoding for PMTs, namely, Afpmt1, Afpmt2 and Afpmt4. We have previously shown that lack of AfPmt1 leads to a temperature-sensitive phenotype featured with severe defects in hyphal growth, conidiation, cell wall integrity and morphology at elevated temperatures. In this study, a conditional mutant P2 was constructed by replacing the native promoter of the Afpmt2 with the Aspergillus nidulans alcA promoter. Reduced expression of the Afpmt2 gene led to a lagged germination, retarded hyphal growth, reduced conidiation and defect in cell wall integrity; however, no temperature-sensitive growth was observed. Further analysis revealed that reduced expression of the Afpmt2 caused a failure of the actin re-arrangement. Our results suggest that Afpmt2 gene was required for growth and played a role distinct from that of the Afpmt1 in A. fumigatus.
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Affiliation(s)
- Wenxia Fang
- Key Laboratory of Systematic Mycology and Lichenology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China
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235
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Endo T, Manya H, Seta N, Guicheney P. POMGnT1, POMT1, and POMT2 mutations in congenital muscular dystrophies. Methods Enzymol 2010; 479:343-52. [PMID: 20816175 DOI: 10.1016/s0076-6879(10)79019-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Alpha-dystroglycanopathies are a group of rare inherited neuromuscular disorders characterized by reduced glycosylation of alpha-dystroglycan (alpha-DG). Mutations in six genes (POMT1, POMT2, POMGNT1, FKTN, FKRP, and LARGE) have been identified in patients with alpha-dystroglycanopathies. Due to an extremely broad clinical spectrum and relatively poor phenotype-genotype correlation, diagnosis of alpha-dystroglycanopathies is difficult and requires searching for mutations gene by gene. At present, of the six proteins involved on alpha-dystroglycanopathies, the function of the gene products is only known for POMT1, POMT2, and POMGnT1, all responsible for the O-mannosylglycan biosynthesis. This chapter describes the assay protocols to diagnose patients with alpha-dystroglycanopathy by measuring glycosyltransferase activity.
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Affiliation(s)
- Tamao Endo
- Molecular Glycobiology, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo, Japan
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236
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Nakamura N, Stalnaker SH, Lyalin D, Lavrova O, Wells L, Panin VM. Drosophila Dystroglycan is a target of O-mannosyltransferase activity of two protein O-mannosyltransferases, Rotated Abdomen and Twisted. Glycobiology 2009; 20:381-94. [PMID: 19969597 DOI: 10.1093/glycob/cwp189] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Recent studies highlighted an emerging possibility of using Drosophila as a model system for investigating the mechanisms of human congenital muscular dystrophies, called dystroglycanopathies, resulting from the abnormal glycosylation of alpha-dystroglycan. Several of these diseases are associated with defects in O-mannosylation, one of the most prominent types of alpha-dystroglycan glycosylation mediated by two protein O-mannosyltransferases. Drosophila appears to possess homologs of all essential components of the mammalian dystroglycan-mediated pathway; however, the glycosylation of Drosophila Dystroglycan (DG) has not yet been explored. In this study, we characterized the glycosylation of Drosophila DG using a combination of glycosidase treatments, lectin blots, trypsin digestion, and mass spectrometry analyses. Our results demonstrated that DG extracellular domain is O-mannosylated in vivo. We found that the concurrent in vivo activity of the two Drosophila protein O-mannosyltransferases, Rotated Abdomen and Twisted, is required for O-mannosylation of DG. While our experiments unambiguously determined some O-mannose sites far outside of the mucin-type domain of DG, they also provided evidence that DG bears a significant amount of O-mannosylation within its central region including the mucin-type domain, and that O-mannose can compete with O-GalNAc glycosylation of DG. We found that Rotated Abdomen and Twisted could potentiate in vivo the dominant-negative effect of DG extracellular domain expression on crossvein development, which suggests that O-mannosylation can modulate the ligand-binding activity of DG. Taken together these results demonstrated that O-mannosylation of Dystroglycan is an evolutionarily ancient mechanism conserved between Drosophila and humans, suggesting that Drosophila can be a suitable model system for studying molecular and genetic mechanisms underlying human dystroglycanopathies.
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Affiliation(s)
- Naosuke Nakamura
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
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238
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Kawahara G, Guyon JR, Nakamura Y, Kunkel LM. Zebrafish models for human FKRP muscular dystrophies. Hum Mol Genet 2009; 19:623-33. [PMID: 19955119 PMCID: PMC2807370 DOI: 10.1093/hmg/ddp528] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Various muscular dystrophies are associated with the defective glycosylation of α-dystroglycan and are known to result from mutations in genes encoding glycosyltransferases. Fukutin-related protein (FKRP) was identified as a homolog of fukutin, the defective protein in Fukuyama-type congenital muscular dystrophy (FCMD), that is thought to function as a glycosyltransferase. Mutations in FKRP have been linked to a variety of phenotypes including Walker–Warburg syndrome (WWS), limb girdle muscular dystrophy (LGMD) 2I and congenital muscular dystrophy 1C (MDC1C). Zebrafish are a useful animal model to reveal the mechanism of these diseases caused by mutations in FKRP gene. Downregulating FKRP expression in zebrafish by two different morpholinos resulted in embryos which had developmental defects similar to those observed in human muscular dystrophies associated with mutations in FKRP. The FKRP morphants showed phenotypes involving alterations in somitic structure and muscle fiber organization, as well as defects in developing eye morphology. Additionally, they were found to have a reduction in α-dystroglycan glycosylation and a shortened myofiber length. Moreover, co-injection of fish or human FKRP mRNA along with the morpholino restored normal development, α-dystroglycan glycosylation and laminin binding activity of α-dystroglycan in the morphants. Co-injection of the human FKRP mRNA containing causative mutations found in human patients of WWS, MDC1C and LGMD2I could not restore their phenotypes significantly. Interestingly, these morphant fish having human FKRP mutations showed a wide phenotypic range similar to that seen in humans.
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Affiliation(s)
- Genri Kawahara
- Division of Genetics, Program in Genetics, Harvard Medical School, Children's Hospital, Boston, MA, USA
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239
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Barkovich AJ, Millen KJ, Dobyns WB. A developmental and genetic classification for midbrain-hindbrain malformations. Brain 2009; 132:3199-230. [PMID: 19933510 PMCID: PMC2792369 DOI: 10.1093/brain/awp247] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Revised: 08/04/2009] [Accepted: 08/21/2009] [Indexed: 01/30/2023] Open
Abstract
Advances in neuroimaging, developmental biology and molecular genetics have increased the understanding of developmental disorders affecting the midbrain and hindbrain, both as isolated anomalies and as part of larger malformation syndromes. However, the understanding of these malformations and their relationships with other malformations, within the central nervous system and in the rest of the body, remains limited. A new classification system is proposed, based wherever possible, upon embryology and genetics. Proposed categories include: (i) malformations secondary to early anteroposterior and dorsoventral patterning defects, or to misspecification of mid-hindbrain germinal zones; (ii) malformations associated with later generalized developmental disorders that significantly affect the brainstem and cerebellum (and have a pathogenesis that is at least partly understood); (iii) localized brain malformations that significantly affect the brain stem and cerebellum (pathogenesis partly or largely understood, includes local proliferation, cell specification, migration and axonal guidance); and (iv) combined hypoplasia and atrophy of putative prenatal onset degenerative disorders. Pertinent embryology is discussed and the classification is justified. This classification will prove useful for both physicians who diagnose and treat patients with these disorders and for clinical scientists who wish to understand better the perturbations of developmental processes that produce them. Importantly, both the classification and its framework remain flexible enough to be easily modified when new embryologic processes are described or new malformations discovered.
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Affiliation(s)
- A James Barkovich
- Neuroradiology Room L371, University of California at San Francisco, 505 Parnassus Avenue, San Francisco, CA 94143-0628, USA.
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240
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Lu PJ, Zillmer A, Wu X, Lochmuller H, Vachris J, Blake D, Chan YM, Lu QL. Mutations alter secretion of fukutin-related protein. Biochim Biophys Acta Mol Basis Dis 2009; 1802:253-8. [PMID: 19900540 DOI: 10.1016/j.bbadis.2009.10.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 10/12/2009] [Accepted: 10/30/2009] [Indexed: 11/27/2022]
Abstract
Mutations in the fukutin-related protein (FKRP) gene cause limb-girdle muscular dystrophy type 2I (LGMD2I) as well as other severe muscle disorders, including Walker-Warburg syndrome, muscle-eye-brain disease, and congenital muscular dystrophy type 1C. The FKRP gene encodes a putative glycosyltransferase, but its precise localization and functions have yet to be determined. In the present study, we demonstrated that normal FKRP is secreted into culture medium and mutations alter the pattern of secretion in CHO cells. L276I mutation associated with mild disease phenotype was shown to reduce the level of secretion whereas P448L and C318Y mutations associated with severe disease phenotype almost abolished the secretion. However, a truncated FKRP mutant protein lacking the entire C-terminal 185 amino acids due to the E310X nonsense mutation was able to secrete as efficiently as the normal FKRP. The N-terminal signal peptide sequence is apparently cleaved from the secreted FKRP proteins. Alteration of the secretion pathway by different mutations and spontaneous read-through of nonsense mutation may contribute to wide variations in phenotypes associated with FKRP-related diseases.
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Affiliation(s)
- Pei J Lu
- McColl-Lockwood Laboratory for Muscular Dystrophy Research, Neuromuscular/ALS Center, Carolinas Medical Center, 1000 Blythe Blvd. Charlotte, NC 28231, USA
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241
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Pilgram GSK, Potikanond S, Baines RA, Fradkin LG, Noordermeer JN. The roles of the dystrophin-associated glycoprotein complex at the synapse. Mol Neurobiol 2009; 41:1-21. [PMID: 19899002 PMCID: PMC2840664 DOI: 10.1007/s12035-009-8089-5] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Accepted: 10/15/2009] [Indexed: 12/30/2022]
Abstract
Duchenne muscular dystrophy is caused by mutations in the dystrophin gene and is characterized by progressive muscle wasting. A number of Duchenne patients also present with mental retardation. The dystrophin protein is part of the highly conserved dystrophin-associated glycoprotein complex (DGC) which accumulates at the neuromuscular junction (NMJ) and at a variety of synapses in the peripheral and central nervous systems. Many years of research into the roles of the DGC in muscle have revealed its structural function in stabilizing the sarcolemma. In addition, the DGC also acts as a scaffold for various signaling pathways. Here, we discuss recent advances in understanding DGC roles in the nervous system, gained from studies in both vertebrate and invertebrate model systems. From these studies, it has become clear that the DGC is important for the maturation of neurotransmitter receptor complexes and for the regulation of neurotransmitter release at the NMJ and central synapses. Furthermore, roles for the DGC have been established in consolidation of long-term spatial and recognition memory. The challenges ahead include the integration of the behavioral and mechanistic studies and the use of this information to identify therapeutic targets.
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Affiliation(s)
- Gonneke S K Pilgram
- Department of Molecular and Cell Biology, Leiden University Medical Center, The Netherlands
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242
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Manya H, Akasaka-Manya K, Nakajima A, Kawakita M, Endo T. Role of N-glycans in maintaining the activity of protein O-mannosyltransferases POMT1 and POMT2. J Biochem 2009; 147:337-44. [PMID: 19880378 DOI: 10.1093/jb/mvp170] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The complex of protein O-mannosyltransferase 1 (POMT1) and POMT2 catalyzes the initial step of O-mannosyl glycan biosynthesis. The mutations in either POMT1 or POMT2 can lead to Walker-Warburg syndrome, a congenital muscular dystrophy with abnormal neuronal migration. Here, we used three algorithms for predicting transmembrane helices to construct the secondary structural models of human POMT1 and POMT2. In these models, POMT1 and POMT2 have seven- and nine-transmembrane helices and contain four and five potential N-glycosylation sites, respectively. To determine whether these sites are actually glycosylated, we prepared mutant proteins that were defective in each site by site-directed mutagenesis. Three of the POMT1 sites and all of the POMT2 sites were found to be N-glycosylated, suggesting that these sites face the luminal side of the endoplasmic reticulum. Mutation of any single site did not significantly affect POMT activity, but mutations of all N-glycosylation sites of either POMT1 or POMT2 caused a loss of POMT activity. The loss of activity appeared to be due to the decreased hydrophilicity. These results suggest that the N-glycosylation of POMT1 and POMT2 is required for maintaining the conformation as well as the activity of the POMT1-POMT2 complex.
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Affiliation(s)
- Hiroshi Manya
- Glycobiology Research Group, Tokyo Metropolitan Institute of Gerontology, Foundation for Research on Aging and Promotion of Human Welfare, 35-2 Sakaecho, Itabashi-ku, Tokyo, Japan.
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243
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Park SH, Shin SY. Walker-Warburg Syndrome Manifesting as Leopard Spot Retinopathy, Retinal Detachment, and Microphthalmia. J Pediatr Ophthalmol Strabismus 2009. [PMID: 19791710 DOI: 10.3928/01913913-20090918-09] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 02/19/2009] [Indexed: 11/20/2022]
Abstract
Walker-Warburg syndrome, also known as HARD+/-E, is a congenital autosomal recessive disorder characterized by hydrocephalus, agyria, and retinal dysplasia, with or without encephalocele. The authors describe an infant with Walker-Warburg syndrome who presented with microphthalmia, retinal detachment, and leopard spot retinopathy.
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244
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Fernández-Álvarez A, Elías-Villalobos A, Ibeas JI. The O-mannosyltransferase PMT4 is essential for normal appressorium formation and penetration in Ustilago maydis. THE PLANT CELL 2009; 21:3397-412. [PMID: 19880800 PMCID: PMC2782298 DOI: 10.1105/tpc.109.065839] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 09/07/2009] [Accepted: 10/05/2009] [Indexed: 05/19/2023]
Abstract
In Saccharomyces cerevisiae, the PMT, KRE2/MNT1, and MNN1 mannosyltransferase protein families catalyze the steps of the O-mannosylation pathway, sequentially adding mannoses to target proteins. We have identified members of all three families and analyzed their roles in pathogenesis of the maize smut fungus Ustilago maydis. Furthermore, we have shown that PMT4, one of the three PMT family members in U. maydis, is essential for tumor formation in Zea mays. Significantly, PMT4 seems to be required only for pathogenesis and is dispensable for other aspects of the U. maydis life cycle. We subsequently show that the deletion of pmt4 results in a strong reduction in the frequency of appressorium formation, with the few appressoria that do form lacking the capacity to penetrate the plant cuticle. Our findings suggest that the O-mannosylation pathway plays a key role in the posttranslational modification of proteins involved in the pathogenic development of U. maydis. The fact that PMT homologs are not found in plants may open new avenues for the development of fungal control strategies. Moreover, the discovery of a highly specific requirement for a single O-mannosyltransferase should aid in the identification of the proteins directly involved in fungal plant penetration, thus leading to a better understanding of plant-fungi interactions.
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245
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Abstract
This article reviews key recent findings in the field of human cortical development. This development is divided into three major time-dependent phases: neural proliferation of inhibitory and excitatory neurons in spatially distinct regions, migration through multiple cellular boundaries, and maturation through morphologic changes that result in the elaboration of dendrites and axons and that establish the multitude of cellular contacts that underlie neuronal processing. Many of the neurocognitive disorders treated in the clinic can trace their origin to a disorder in one or more of these key steps. Along with this update, work is highlighted that offers a glimpse at the future of therapy for developmental brain disorders that can result from disorders of these cellular events.
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246
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Hewitt JE. Abnormal glycosylation of dystroglycan in human genetic disease. Biochim Biophys Acta Mol Basis Dis 2009; 1792:853-61. [DOI: 10.1016/j.bbadis.2009.06.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 06/05/2009] [Accepted: 06/10/2009] [Indexed: 10/20/2022]
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247
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Chang W, Winder TL, LeDuc CA, Simpson LL, Millar WS, Dungan J, Ginsberg N, Plaga S, Moore SA, Chung WK. Founder Fukutin mutation causes Walker-Warburg syndrome in four Ashkenazi Jewish families. Prenat Diagn 2009; 29:560-9. [PMID: 19266496 PMCID: PMC2735827 DOI: 10.1002/pd.2238] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Walker-Warburg syndrome (WWS) is a genetically heterogeneous congenital muscular dystrophy caused by abnormal glycosylation of alpha-dystroglycan (alpha-DG) that is associated with brain malformations and eye anomalies. The Fukutin (FKTN) gene, which causes autosomal recessively inherited WWS is most often associated with Fukuyama congenital muscular dystrophy in Japan. We describe the clinical features of four nonconsanguinous Ashkenazi Jewish families with WWS and identify the underlying genetic basis for WWS. METHOD We screened for mutations in POMGnT1, POMT1, POMT2, and FKTN, genes causing WWS, by dideoxy sequence analysis. RESULTS We identified an identical homozygous c.1167insA mutation in the FKTN gene on a common haplotype in all four families and identified 2/299 (0.7%) carriers for the c.1167insA mutation among normal American Ashkenazi Jewish adults. CONCLUSION These data suggest that the c.1167insA FKTN mutation described by us is a founder mutation that can be used to target diagnostic testing and carrier screening in the Ashkenazi Jewish population.
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Affiliation(s)
- Wendy Chang
- Division of Molecular Genetics, Department of Pediatrics, Columbia University Medical Center, New York, NY, USA.
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248
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Willger SD, Ernst JF, Alspaugh JA, Lengeler KB. Characterization of the PMT gene family in Cryptococcus neoformans. PLoS One 2009; 4:e6321. [PMID: 19633715 PMCID: PMC2711527 DOI: 10.1371/journal.pone.0006321] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 06/23/2009] [Indexed: 12/15/2022] Open
Abstract
Background Protein-O-mannosyltransferases (Pmt's) catalyze the initial step of protein-O-glycosylation, the addition of mannose residues to serine or threonine residues of target proteins. Methodology/Principal Findings Based on protein similarities, this highly conserved protein family can be divided into three subfamilies: the Pmt1 sub-family, the Pmt2 sub-family and the Pmt4 sub-family. In contrast to Saccharomyces cerevisiae and Candida albicans, but similar to filamentous fungi, three putative PMT genes (PMT1, PMT2, and PMT4) were identified in the genome of the human fungal pathogen Cryptococcus neoformans. Similar to Schizosaccharomyces pombe and C. albicans, C. neoformans PMT2 is an essential gene. In contrast, the pmt1 and pmt4 single mutants are viable; however, the pmt1/pmt4 deletions are synthetically lethal. Mutation of PMT1 and PMT4 resulted in distinct defects in cell morphology and cell integrity. The pmt1 mutant was more susceptible to SDS medium than wild-type strains and the mutant cells were enlarged. The pmt4 mutant grew poorly on high salt medium and demonstrated abnormal septum formation and defects in cell separation. Interestingly, the pmt1 and pmt4 mutants demonstrated variety-specific differences in the levels of susceptibility to osmotic and cell wall stress. Delayed melanin production in the pmt4 mutant was the only alteration of classical virulence-associated phenotypes. However, the pmt1 and pmt4 mutants showed attenuated virulence in a murine inhalation model of cryptococcosis. Conclusion/Significance These findings suggest that C. neoformans protein-O-mannosyltransferases play a crucial role in maintaining cell morphology, and that reduced protein-O-glycosylation leads to alterations in stress resistance, cell wall composition, cell integrity, and survival within the host.
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Affiliation(s)
- Sven D Willger
- Institut für Mikrobiologie, Molekulare Mykologie, Heinrich-Heine-Universität, Düsseldorf, Germany.
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249
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Production of heterologous proteins using the fission-yeast (Schizosaccharomyces pombe) expression system. Biotechnol Appl Biochem 2009; 53:227-35. [PMID: 19531030 DOI: 10.1042/ba20090048] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The fission yeast Schizosaccharomyces pombe is a particularly useful model for studying the function and regulation of genes from higher eukaryotes. The genome of Sc. pombe has been sequenced, and DNA microarray, proteome and transcriptome analyses have been carried out. Among the well-characterized yeast species, Sc. pombe is considered an attractive host for the production of heterologous proteins. Expression vectors for high-level expression in Sc. pombe have been developed and many foreign proteins have been successfully expressed. However, further improvements in the protein-expressing host systems are still required for the production of heterologous proteins involved in post-translational modification, metabolism and intracellular trafficking. This minireview focuses on recent advances in heterologous protein production by use of engineered fission-yeast strains.
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Molecular regulation of neuronal migration during neocortical development. Mol Cell Neurosci 2009; 42:11-22. [PMID: 19523518 DOI: 10.1016/j.mcn.2009.06.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Accepted: 06/03/2009] [Indexed: 11/21/2022] Open
Abstract
Neocortex, a distinct six-layered neural structure, is one of the most exquisite nerve tissues in the human body. Proper assembly of neocortex requires precise regulation of neuronal migration and abnormalities can result in severe neurological diseases. Three major types of neuronal migration have been implicated in corticogenesis: radial migration of excitatory neuron precursors and tangential migration of interneurons as well as Cajal-Retzius cells. In the past several years, significant progress has been made in understanding how these parallel events are regulated and coordinated during corticogenesis. New insights have been gained into regulation of radial neuron migration by the well-known Reelin signal. New pathways have also been identified that regulate radial as well as tangential migration. Equally important, better understandings have been obtained on the cellular and molecular mechanics of cell migration by both projection neurons and interneurons. These findings have not only enhanced our understanding of normal neuron migration but also revealed insights into the etiologies of several neurological diseases where these processes go awry.
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