UMLS:C0026850 - FACTA Search

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

The sarcoglycan complex has been well characterized in striated muscle, and defects in its components are associated with muscular dystrophy and cardiomyopathy. Here, we have characterized the smooth muscle sarcoglycan complex. By examination of embryonic muscle lineages and biochemical fractionation studies, we demonstrated that epsilon-sarcoglycan is an integral component of the smooth muscle sarcoglycan complex along with beta- and delta-sarcoglycan. Analysis of genetically defined animal models for muscular dystrophy supported this conclusion. The delta-sarcoglycan-deficient cardiomyopathic hamster and mice deficient in both dystrophin and utrophin showed loss of the smooth muscle sarcoglycan complex, whereas the complex was unaffected in alpha-sarcoglycan null mice in agreement with the finding that alpha-sarcoglycan is not expressed in smooth muscle cells. In the cardiomyopathic hamster, the smooth muscle sarcoglycan complex, containing epsilon-sarcoglycan, was fully restored following intramuscular injection of recombinant delta-sarcoglycan adenovirus. Together, these results demonstrate a tissue-dependent variation in the sarcoglycan complex and show that epsilon-sarcoglycan replaces alpha-sarcoglycan as an integral component of the smooth muscle dystrophin-glycoprotein complex. Our results also suggest a molecular basis for possible differential smooth muscle dysfunction in sarcoglycan-deficient patients.
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PMID:epsilon-sarcoglycan replaces alpha-sarcoglycan in smooth muscle to form a unique dystrophin-glycoprotein complex. 1048 49

Limb girdle muscular dystrophy (LGMD) 2F is caused by mutations in the delta-sarcoglycan (SG) gene. Previously, we have shown successful application of a recombinant adeno-associated virus (AAV) vector for genetic and biochemical rescue in the Bio14.6 hamster, a homologous animal model for LGMD 2F (J. Li et al., Gene Ther. 6:74-82, 1999). In this report, we show efficient and long-term delta-SG expression accompanied by nearly complete recovery of physiological function deficits after a single-dose AAV vector injection into the tibialis anterior muscle of the dystrophic hamsters. AAV vector treatment led to more than 97% recovery in muscle strength for both the specific twitch force and the specific tetanic force, when compared to the age-matched control. Vector treatment also prevented pathological muscle hypertrophy and resulted in normal muscle weight and size. Finally, vector-treated muscle showed substantial improvement of the histopathology. This is the first report of successful functional rescue of an entire muscle after AAV-mediated gene delivery. This report also demonstrates the feasibility of in vivo gene therapy for LGMD patients by using AAV vectors.
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PMID:Full functional rescue of a complete muscle (TA) in dystrophic hamsters by adeno-associated virus vector-directed gene therapy. 1062 54

Mutations in genes encoding for the sarcoglycans, a subset of proteins within the dystrophin-glycoprotein complex, produce a limb-girdle muscular dystrophy phenotype; however, the precise role of this group of proteins in the skeletal muscle is not known. To understand the role of the sarcoglycan complex, we looked for sarcoglycan interacting proteins with the hope of finding novel members of the dystrophin-glycoprotein complex. Using the yeast two-hybrid method, we have identified a skeletal muscle-specific form of filamin, which we term filamin 2 (FLN2), as a gamma- and delta-sarcoglycan interacting protein. In addition, we demonstrate that FLN2 protein localization in limb-girdle muscular dystrophy and Duchenne muscular dystrophy patients and mice is altered when compared with unaffected individuals. Previous studies of filamin family members have determined that these proteins are involved in actin reorganization and signal transduction cascades associated with cell migration, adhesion, differentiation, force transduction, and survival. Specifically, filamin proteins have been found essential in maintaining membrane integrity during force application. The finding that FLN2 interacts with the sarcoglycans introduces new implications for the pathogenesis of muscular dystrophy.
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PMID:Filamin 2 (FLN2): A muscle-specific sarcoglycan interacting protein. 1062 22

Muscular dystrophy is a heterogeneous genetic disease that affects skeletal and cardiac muscle. The genetic defects associated with muscular dystrophy include mutations in dystrophin and its associated glycoproteins, the sarcoglycans. Furthermore, defects in dystrophin have been shown to cause a disruption of the normal expression and localization of the sarcoglycan complex. Thus, abnormalities of sarcoglycan are a common molecular feature in a number of dystrophies. By combining biochemistry, molecular cell biology, and human and mouse genetics, a growing understanding of the sarcoglycan complex is emerging. Sarcoglycan appears to be an important, independent mediator of dystrophic pathology in both skeletal muscle and heart. The absence of sarcoglycan leads to alterations of membrane permeability and apoptosis, two shared features of a number of dystrophies. beta-sarcoglycan and delta-sarcoglycan may form the core of the sarcoglycan subcomplex with alpha- and gamma-sarcoglycan less tightly associated to this core. The relationship of epsilon-sarcoglycan to the dystrophin-glycoprotein complex remains unclear. Animals lacking alpha-, gamma- and delta-sarcoglycan have been described and provide excellent opportunities for further investigation of the function of sarcoglycan. Dystrophin with dystroglycan and laminin may be a mechanical link between the actin cytoskeleton and the extracellular matrix. By positioning itself in close proximity to dystrophin and dystroglycan, sarcoglycan may function to couple mechanical and chemical signals in striated muscle. Sarcoglycan may be an independent signaling or regulatory module whose position in the membrane is determined by dystrophin but whose function is carried out independent of the dystrophin-dystroglycan-laminin axis.
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PMID:Sarcoglycans in muscular dystrophy. 1067 64

The dystrophin-based membrane cytoskeleton of muscle fibers has emerged as a critical multi-protein complex which seems to impart structural integrity on the muscle fiber plasma membrane. Deficiency of dystrophin causes the most common types of muscular dystrophy, Duchenne and Becker muscular dystrophies. Muscular dystrophy patients showing normal dystrophin protein and gene analysis are generally isolated cases with a presumed autosomal recessive inheritance pattern (limb-girdle muscular dystrophy). Recently, linkage and candidate gene analyses have shown that some cases of limb-girdle muscular dystrophy can be caused by deficiency of other components of the dystrophin membrane cytoskeleton. The most recently identified component, delta-sarcoglycan, has been found to show mutations in a series of Brazilian muscular dystrophy patients. All patients were homozygous for a protein-truncating carboxy-terminal mutation, and showed a deficiency of the four sarcoglycan proteins. To determine if delta-sarcoglycan deficiency occurred in other world populations, to identify the range of mutations and clinical phenotypes, and to test for the biochemical consequences of delta-sarcoglycan gene mutations, we studied Duchenne-like and limb-girdle muscular dystrophy patients who we had previously shown not to exhibit gene mutations of dystrophin, alpha-, beta-, or gamma-sarcoglycan for delta-sarcoglycan mutations (n = 54). We identified two American patients with novel nonsense mutations of delta-sarcoglycan (W30X, R165X). One was apparently homozygous, and we show likely consanguinity through homozygosity for 13 microsatellite loci covering a 38 cM region of chromosome 5. The second was heterozygous. Both were girls who showed clinical symptoms consistent with Duchenne muscular dystrophy in males. Our data shows that delta-sarcoglycan deficiency occurs in other world populations, and that most or all patients show a deficiency of the entire sarcoglycan complex, adding support to the hypothesis that these proteins function as a tetrameric unit.
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PMID:Mutations in the delta-sarcoglycan gene are a rare cause of autosomal recessive limb-girdle muscular dystrophy (LGMD2). 1073 75

Autosomal recessive limb girdle muscular dystrophies 2C-2F represent a family of diseases caused by primary mutations in the sarcoglycan genes. We show that sarcospan, a novel tetraspan-like protein, is also lost in patients with either a complete or partial loss of the sarcoglycans. In particular, sarcospan was absent in a gamma-sarcoglycanopathy patient with normal levels of alpha-, beta- and delta-sarcoglycan. Thus, it is likely that assembly of the complete, tetrameric sarcoglycan complex is a prerequisite for membrane targeting and localization of sarcospan. Based on our findings that sarcospan is integrally associated with the sarcoglycans, we screened >50 autosomal recessive muscular dystrophy cases for mutations in sarcospan. Although we identified three intragenic polymorphisms, we did not find any cases of muscular dystrophy associated with primary mutations in the sarcospan gene. Finally, we have identified an important case of limb girdle muscular dystrophy and cardiomyopathy with normal expression of sarcospan. This patient has a primary mutation in the gamma-sarcoglycan gene, which causes premature truncation of gamma-sarcoglycan without affecting assembly of the mutant gamma-sarcoglycan into a complex with alpha-, beta- and delta-sarcoglycan and sarcospan. This is the first demonstration that membrane expression of a mutant sarcoglycan-sarcospan complex is insufficient in preventing muscular dystrophy and cardiomyopathy and that the C-terminus of gamma-sarcoglycan is critical for the functioning of the entire sarcoglycan-sarcospan complex. These findings are important as they contribute to a greater understanding of the structural determinants required for proper sarcoglycan-sarcospan expression and function.
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PMID:Molecular and genetic characterization of sarcospan: insights into sarcoglycan-sarcospan interactions. 1094 31

Myogenic satellite cells were isolated from control and dystrophic hamster diaphragms to examine cellular mechanisms involved in the physiology of muscular dystrophy. The Bio 14.6 dystrophic hamster, which possesses a defect in the delta-sarcoglycan gene, develops biochemical and physical symptoms of Duchenne-like and limb girdle muscular dystrophies. Because primary cultures of the control and dystrophic satellite cells became extensively contaminated with non-myogenic cells during proliferation, cell clones were developed to provide pure cultures for study. Cell culture conditions were optimized with the use of Ham's F-12K medium containing 10% fetal bovine serum +5% horse serum + 10 ng/mL basic fibroblast growth factor + 50 microg/mL porcine gelatin. Proliferation rates of the two clonal cultures were similar between the two lines. Satellite cell-derived myotubes from both primary cultures and clones differed between control and dystrophic animals. Dystrophic myotubes tended to be long and narrow, while the control-derived myotubes were broader. Measurement of muscle-specific creatine kinase during differentiation revealed that the dystrophic myotubes possessed higher creatine kinase levels than control myotubes (up to 146-fold at 168 h). The results demonstrate that satellite cells can be isolated from the hamster and may provide a useful tool to study muscular dystrophies associated with defects in the sarcoglycan complex and the involvement of sarcoglycans in normal skeletal muscle growth and development.
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PMID:Isolation and characterization of myogenic satellite cells from the muscular dystrophic hamster. 1103 97

Models of the dystrophin-glycoprotein complex do not reconcile the novel sparing of extraocular muscle in muscular dystrophy. Extraocular muscle sparing in Duchenne muscular dystrophy implies the existence of adaptive properties in these muscles that may extend protection to other neuromuscular diseases. We studied the extraocular muscle morphology and dystrophin-glycoprotein complex organization in murine targeted deletion of the gamma-sarcoglycan (gsg(-/-)) and delta-sarcoglycan (dsg(-/-)) genes, two models of autosomal recessive limb girdle muscular dystrophy. In contrast to limb and diaphragm, the principal extraocular muscles were intact in gsg(-/-) and dsg(-/-) mice. However, central nucleated, presumptive regenerative, fibers were seen in the accessory extraocular muscles (retractor bulbi, levator palpebrae superioris) of both strains. Skeletal muscles of gsg(-/-) mice exhibited in vivo Evans Blue dye permeability, while the principal extraocular muscles did not. Disruption of gamma-sarcoglycan produced secondary displacement of alpha- and beta-sarcoglycans in the extraocular muscles. The intensity of immunofluorescence for dystrophin and alpha- and beta-dystroglycan also appeared to be slightly reduced. Utrophin localization was unchanged. The finding that sarcoglycan disruption was insufficient to elicit alterations in extraocular muscle suggests that loss of mechanical stability and increased sarcolemmal permeability are not inevitable consequences of mutations that disrupt the dystrophin-glycoprotein complex organization and must be accounted for in models of muscular dystrophy.
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PMID:Extraocular muscle is spared despite the absence of an intact sarcoglycan complex in gamma- or delta-sarcoglycan-deficient mice. 1125 78

Deficiency of delta-sarcoglycan (delta-SG), a component of the dystrophin-glycoprotein complex, causes cardiomyopathy and skeletal muscle dystrophy in Bio14.6 hamsters. Using cultured myotubes prepared from skeletal muscle of normal and Bio14.6 hamsters (J2N-k strain), we investigated the possibility that the delta-SG deficiency may lead to alterations in ionic conductances, which may ultimately lead to myocyte damage. In cell-attached patches (with Ba(2+) as the charge carrier), an approximately 20-pS channel was observed in both control and Bio14.6 myotubes. This channel is also permeable to K(+) and Na(+) but not to Cl(-). Channel activity was increased by pressure-induced stretch and was reduced by GdCl(3) (>5 microM). The basal open probability of this channel was fourfold higher in Bio14.6 myotubes, with longer open and shorter closed times. This was mimicked by depolymerization of the actin cytoskeleton. In intact Bio14.6 myotubes, the unidirectional basal Ca(2+) influx was enhanced compared with control. This Ca(2+) influx was sensitive to GdCl(3), signifying that stretch-activated cation channels may have been responsible for Ca(2+) influx in Bio14.6 hamster myotubes. These results suggest a possible mechanism by which cell damage might occur in this animal model of muscular dystrophy.
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PMID:Stretch-activated cation channels in skeletal muscle myotubes from sarcoglycan-deficient hamsters. 1144 68

Dilated cardiomyopathy is one of the leading causes of heart failure and a primary cause for heart transplantation in patients below the age of 40 years. Despite major advances in diagnostic procedures such as examination of myocardial biopsies, the etiology remains unknown in many patients. Chronic inflammation or myocarditis and chronic alcohol abuse are considered two main etiologic factors in dilated cardiomyopathy. A third causal factor, namely genetic transmission of the disease, is at least as common as myocardial inflammation or toxic damage. Several prospective studies of relatives of patients with dilated cardiomyopathy proved that about 25-30% of all cases are of familial etiology. The most common mode of inheritance is autosomal dominant. Less frequently is the disease inherited as an X-chromosomal trait. Autosomal recessive and mitochondrial transmission is rare. The penetrance is highly variable and age dependent. Many relatives of patients with DCM show only minor cardiac abnormalities and it is unknown whether they progress to full cardiomyopathy in later life. Examination of families has identified so far eight disease genes, namely the dystrophin, tafazzin, cardiac actin, desmin, lamin A/C, delta- sarcoglycan, cardiac beta-myosin heavy chain, and cardiac troponin T gene. Certain mutations in lamin A/C cause conduction system disease and dilated cardiomyopathy, whereas other mutations cause in addition skeletal muscle myopathy. Dystrophin mutations are the cause of the rare X-linked dilated cardiomyopathy without skeletal muscle involvement and a progressive course in young men. Other mutations in the dystrophin gene, mainly deletions, are the cause of the muscular dystrophy Becker and Duchenne which also present with dilated cardiomyopathy. Mutations of the desmin, delta-sarcoglycan, the cardiac actin and beta-myosin heavy chain as well as the troponin T gene are known to cause autosomal dominant-dilated cardiomyopathy without other abnormalities. The infantile X-linked DCM is caused by mutations of the tafazzin gene. The onset of the disease is typically within the first year of life and death occurs usually in childhood. Most patients may in addition be characterized by skeletal myopathy, short stature, neutropenia and abnormal mitochondria, also referred to as Barth syndrome. Knowledge of the DCM disease genes led to the new hypothesis that dilated cardiomyopathy is a disease of the myocardial force generation or force transmission. Many more disease loci are known but the responsible disease genes are not yet identified. Better understanding of the expression and function of disease genes may eventually result in new diagnostic and therapeutic tools in order to improve the prognosis of this severe disorder.
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PMID:[Genetics of dilated cardiomyopathy]. 1151 75

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