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Query: UMLS:C0026850 (muscular dystrophy)
 5,870 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

There has been a recent explosion in the identification of neuromuscular diseases caused by mutations in genes that affect carbohydrate metabolism or protein glycosylation. A number of these findings relate to defects in the glycosylation of alpha dystroglycan. Alpha dystroglycan is an essential component of the dystrophin-glycoprotein complex, and aberrant glycosylation of alpha dystroglycan is associated with multiple forms of muscular dystrophy in mice and humans. We review the evidence that defects in dystroglycan glycosylation cause muscular dystrophy. In addition, we review evidence that glycobiology is important in other disorders that affect muscle, including hereditary inclusion body myopathy type II and congenital disorders of glycosylation. Finally, we discuss the long-term potential of glycotherapies for muscle disorders.
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PMID:Glycobiology of neuromuscular disorders. 1273

Dystroglycan is a cell surface receptor involved in the pathogenesis of muscular dystrophy, and plays a critical role in the assembly and homeostasis of basement membranes. Since data about the amphibian homologue are limited, we have cloned the full-length dystroglycan cDNAs from the frog Xenopus laevis. Using in situ hybridization, we show that mRNA expression is dynamic, particularly in the notochord at the end of gastrulation and during neurulation, suggesting that the protein might play unexplored roles in the specification and/or formation of this tissue. Subsequently, the transcripts are detected in the otic vesicle, the developing brain, and in mesenchymal cells of the visceral arches, as well as in pharyngeal endoderm, the pronephros, pronephric ducts, proctodaeum and the somites.
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PMID:Cloning and expression patterns of dystroglycan during the early development of Xenopus laevis. 1273 43

Walker-Warburg syndrome (WWS) is an autosomal recessive disorder characterized by congenital muscular dystrophy, structural eye abnormalities and severe brain malformations. We performed an immunohistochemical and electron microscopy study of a muscle biopsy from a patient affected by WWS carrying a homozygous frameshift mutation in O-mannosyltransferase 1 gene (POMT1). alpha-Dystroglycan glycosylated epitope was not detected in muscle fibers and intramuscular peripheral nerves. Laminin alpha2 chain and perlecan were reduced in muscle fibers and well preserved in intramuscular peripheral nerves. The basal lamina in several muscle fibers showed discontinuities and detachment from the plasmalemma. Most nuclei, including myonuclei and satellite cell nuclei, showed detachment or complete absence of peripheral heterochromatin from the nuclear envelope. Apoptotic changes were detected in 3% of muscle fibers. The particular combination of basal lamina and nuclear changes may suggest that a complex pathogenetic mechanism, affecting several subcellular compartments, underlies the degenerative process in WWS muscle.
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PMID:Extracellular matrix and nuclear abnormalities in skeletal muscle of a patient with Walker-Warburg syndrome caused by POMT1 mutation. 1275 35

We report a two-year-old Caucasian boy who had neonatal seizures and was found to have bilateral occipito-temporal polymicrogyria on neonatal brain MRI. The child had no additional neurological abnormality other than the neonatal seizures, but serum CK was found to be elevated (5 - 7 times normal values) and the muscle biopsy showed evidence of early muscular dystrophy. Detailed protein and genetic studies did not allow the identification of a known form of muscular dystrophy. The boy has been followed regularly and he currently has mild global developmental delay but no clinical signs of muscle involvement. The association of polymicrogyria and muscular dystrophy is known to occur in Fukuyama and Walker Warburg muscular dystrophies, in muscle-eye-brain disease and in some patients with merosin deficient CMD. However the absence of weakness and of eye involvement, the normal expression of merosin and alpha dystroglycan and the pattern of brain involvement make it very unlikely that the child is affected by one of these forms. As the pattern of brain involvement and the muscle pathology is not typical of one of the forms of neuronal migration disorders secondary to a known gene defect, we suspect that the combination of muscle and brain involvement found in this child is not coincidental. Our findings suggest that serum CK should be determined in children with undiagnosed polymicrogyria, even in the absence of weakness. This may lead to an expansion of our understanding of muscle dystrophies and cortical dysplasias.
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PMID:Occipito-temporal polymicrogyria and subclinical muscular dystrophy. 1277 31

Fukuyama-type congenital muscular dystrophy (FCMD), one of the most common autosomal-recessive disorders in Japan, is characterized by congenital muscular dystrophy associated with brain malformation due to a defect during neuronal migration. Through positional cloning, we previously identified the gene for FCMD, which encodes the fukutin protein. Here we report that chimeric mice generated using embryonic stem cells targeted for both fukutin alleles develop severe muscular dystrophy, with the selective deficiency of alpha-dystroglycan and its laminin-binding activity. In addition, these mice showed laminar disorganization of the cortical structures in the brain with impaired laminin assembly, focal interhemispheric fusion, and hippocampal and cerebellar dysgenesis. Further, chimeric mice showed anomaly of the lens, loss of laminar structure in the retina, and retinal detachment. These results indicate that fukutin is necessary for the maintenance of muscle integrity, cortical histiogenesis, and normal ocular development and suggest the functional linkage between fukutin and alpha-dystroglycan.
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PMID:Fukutin is required for maintenance of muscle integrity, cortical histiogenesis and normal eye development. 1278 52

Dystroglycan is a key complex between basal lamina laminin, extracellularly and membrano-cytoskeleton, intracellularly. The damage of this linkage is turned out to cause muscular dystrophies. Dystroglycan knockout is lethal. Dystroglycan-associated intracellular proteins such as dystrophin, dystrobrevin, sarcoglycans, plectin and caveolin-3 are responsible for causing severe (Duchenne type) and moderate forms (Becker, LGMDs). Laminin, dystroglycan-binding extracellular protein, is deficient in the most severe form of congenital muscular dystrophy with normal intelligence and eye. Recently, a remarkable progress is made in most severe forms of congenital muscular dystrophy with anomalies of brain and eye such as Fukuyama type (Japan) and muscle-eye-brain disease (Finland). The gene product for Fukuyama type, fukutin, belongs to a family of glycosylation enzymes in bacteria and yeast. Since alpha-dystroglycan contains 14-15 o-glycans, ser/thr-mannose 2-1 GlcNAc 4-1 Gal 3-2 Sial in the middle third mucin-domain and the sial-o-glycan is essential for laminin-binding, and since alpha-dystroglycan is defective in Fukuyama type sarcolemma with anti both sugar moiety- and peptide-antidodies, defective fukutin causes incomplete o-glycosylation of alpha-dystroglycan. In '02, it is clarified that a glycosylation enzyme, POMGnT1 which modifies GlcNAc onto ser/thr-mannose, is defective in 6 MEB patients. The loss of the enzyme activity is turned out to lose alpha-dystroglycan from sarcolemma of MEB. These data strongly suggests that o-glycosylation defect of alpha-dystroglycan causes the most severe congenital muscular dystrophy such as Fukuyama type, MEB and Walker Warburg syndrome.
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PMID:[Dystroglycan linkage and muscular dystrophy]. 1278 74

Walker-Warburg syndrome (WWS) is an autosomal recessive disorder characterized by the combined involvement of the central nervous and skeletal muscle systems. Although the molecular basis of WWS remains unknown, defects in the muscle fibre basal lamina are characteristic of other forms of congenital muscular dystrophy (CMD). In agreement with this, some forms of CMD, due to glycosyltransferase defects, display a reduction in the immunolabelling of alpha-dystroglycan, whilst beta-dystroglycan labelling appears normal. Here we describe an almost complete absence of alpha-dystroglycan using both immunohistochemistry and immunoblotting in two patients with WWS. In addition, there was a mild reduction of laminin-alpha 2. In contrast, immunohistochemical labelling of perlecan and collagen VI was normal. Linkage analysis excluded the recently identified POMT1 locus, responsible for a proportion of WWS cases. These results confirm that WWS is a genetically heterogeneous condition and suggest that disruption of the alpha-dystroglycan/laminin-alpha 2 axis in the basal lamina may play a role in the degeneration of muscle fibres in WWS-also in cases not due to POMT1 defects.
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PMID:Profound skeletal muscle depletion of alpha-dystroglycan in Walker-Warburg syndrome. 1278 39

Dystroglycan (DG) is an essential component of the dystrophin-glycoprotein complex, a molecular scaffold that links the extracellular matrix to the actin cytoskeleton. Dystroglycan protein is post-translationally cleaved into alpha dystroglycan, a highly glycosylated peripheral membrane protein, and beta dystroglycan, a transmembrane protein. Despite clear evidence of the importance of dystroglycan and its associated proteins in muscular dystrophy, the purpose of dystroglycan proteolysis is unclear. By introducing a point mutation at the normal site of proteolysis (serine 654 to alanine, DGS654A), we have created a dystroglycan protein that is severely inhibited in its cleavage. Transgenic expression of DGS654A in mouse skeletal muscles inhibited the expression of endogenously cleaved dystroglycan, while overexpression of wild type dystroglycan by similar amounts did not. DGS654A animals had increased serum creatine kinase activity and most muscles had increased numbers of central nuclei. Overexpression of wild type dystroglycan, by contrast, caused no dystrophy by these measures. Dystrophy in DGS654A muscles correlated with reduced binding of antibodies that recognize glycosylated forms of alpha dystroglycan. Lastly, neuromuscular junctions in DGS654A muscles were aberrant in structure. These data show that aberrant processing of the dystroglycan polypeptide causes muscular dystrophy and suggest that dystroglycan processing is important for the proper glycosylation of alpha dystroglycan.
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PMID:Inhibition of dystroglycan cleavage causes muscular dystrophy in transgenic mice. 1279 92

The cell biological hypothesis of Duchenne muscular dystrophy assumes that deficiency in the membrane cytoskeletal element dystrophin triggers a loss in surface glycoproteins, such as beta-dystroglycan, thereby rendering the sarcolemmal membrane more susceptible to micro-rupturing. Secondary changes in ion homeostasis, such as increased cytosolic Ca2+ levels and impaired luminal Ca2+ buffering, eventually lead to Ca2+-induced myonecrosis. However, individual muscle groups exhibit a graded pathological response during the natural time course of x-linked muscular dystrophy. The absence of the dystrophin isofom Dp427 does not necessarily result in a severe dystrophic phenotype in all muscle groups. In the dystrophic mdx animal model, extraocular and toe muscles are not as severely affected as limb muscles. Here, we show that the relative expression and sarcolemmal localization of the central trans-sarcolemmal linker of the dystrophin-glycoprotein complex, beta-dystroglycan, is preserved in mdx extraocular and toe fibres by means of two-dimensional immunoblotting and immunofluorescence microscopy. Thus, with respect to improving myology diagnostics, the relative expression levels of beta-dystroglycan appear to represent reliable markers for the severity of secondary changes in dystrophin-deficient fibres. Immunoblotting and enzyme assays revealed that mdx toe muscle fibres exhibit an increased expression and activity of the sarcoplasmic reticulum Ca2+-ATPase. Chemical crosslinking studies demonstrated impaired calsequestrin oligomerization in mdx gastrocnemius muscle indicating that abnormal calsequestrin clustering is involved in reduced Ca2+ buffering of the dystrophic sarcoplasmic reticulum. Previous studies have mostly attributed the sparing of certain mdx fibres to the special protective properties of small-diameter fibres. Our study suggests that the rescue of dystrophin-associated glycoproteins, and possibly the increased removal of cytosolic Ca2+ ions, might also play an important role in protecting muscle cells from necrotic changes.
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PMID:Comparative analysis of Dp427-deficient mdx tissues shows that the milder dystrophic phenotype of extraocular and toe muscle fibres is associated with a persistent expression of beta-dystroglycan. 1280 Sep 77

Dystroglycan (DG) plays a pivotal role within the dystrophin-glycoprotein complex (DGC) which represents a major factor for muscle fibre stability upon contraction. It has been shown that many muscular dystrophy phenotypes are caused by mutations of proteins belonging to or being associated with the DGC. Due to its prominent role for muscle stability, the detailed knowledge of DG structural and functional aspects should be considered of primary importance in order to develop new treatments for neuromuscular diseases.
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PMID:An adhesion molecule involved in muscular dystrophies: structural and functional analysis of dystroglycan domains. 1283 39


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