Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026850 (muscular dystrophy)
 5,870 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dystrophin glycoprotein complex (DGC) is found at the plasma membrane of muscle cells, where it provides a link between the cytoskeleton and the extracellular matrix. A subcomplex within the DGC, the sarcoglycan complex, associates with dystrophin and mediates muscle membrane stability. Mutations in sarcoglycan genes lead to muscular dystrophy and cardiomyopathy in both humans and mice. In invertebrates, there are three sarcoglycan genes, while in mammals there are additional sarcoglycan genes that probably arose from gene duplication events. We identified a novel mammalian sarcoglycan, zeta-sarcoglycan, that is highly related to gamma-sarcoglycan and delta-sarcoglycan. We generated a zeta-sarcoglycan-specific antibody and found that zeta-sarcoglycan associated with other members of the sarcoglycan complex at the plasma membrane. Additionally, zeta-sarcoglycan was reduced at the membrane in muscular dystrophy, consistent with a role in mediating membrane stability. zeta-Sarcoglycan was also found as a component of the vascular smooth muscle sarcoglycan complex. Together, these data demonstrate that zeta-sarcoglycan is an integral component of the sarcoglycan complex and, as such, is important in the pathogenesis of muscular dystrophy.
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PMID:Zeta-sarcoglycan, a novel component of the sarcoglycan complex, is reduced in muscular dystrophy. 1218 67

nNOS, anchored to the sarcolemma through its interactions with the dystrophin-glycoprotein complex, is dramatically reduced in dystrophin-deficient mdx mice and Duchenne muscular dystrophy patients. Recent evidence suggests that loss of nNOS in dystrophin-deficient muscle may contribute significantly to the progression of muscle pathology through a variety of mechanisms. To investigate whether nNOS plays a role in other forms of muscular dystrophy, we analyzed protein expression of nNOS in several sarcoglycan-deficient animal models of muscular dystrophy as well as patients with primary mutations in the sarcoglycan genes. Primary mutations in alpha-, beta-, delta-, and gamma-sarcoglycan result in autosomal recessive limb girdle muscular dystrophy (AR-LGMD). We report that loss of the sarcoglycan-sarcospan complex in muscle causes a dramatic reduction in the levels of nNOS expression at the membrane, even in the presence of normal dystrophin and syntrophin expression. Furthermore, we show that expression of three out of four sarcoglycans is not sufficient to maintain nNOS at the sarcolemma. Our data suggest that loss of nNOS may contribute to muscle pathology in AR-LGMD with primary mutations in the sarcoglycans.
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PMID:Loss of sarcolemma nNOS in sarcoglycan-deficient muscle. 1240 21

While calf muscle hypertrophy is a striking diagnostic finding in sarcoglycanopathy, as it is in Duchenne and Becker muscular dystrophies, its pathogenetic mechanism remains unknown. gamma-Sarcoglycan, one of the subunits of the sarcoglycan complex, is the protein responsible for gamma-sarcoglycanopathy. To elucidate the pathogenetic mechanisms of muscle hypertrophy and degeneration in muscular dystrophy, we utilized a mutant mouse as a model animal. In this study, we generated gamma-sarcoglycan-deficient (gsg-/-) mice by gene targeting. The gsg-/- mice described here, similar to the gsg-/- mice reported previously (J Cell Biol 142 (1998) 1279), demonstrated skeletal and cardiac muscle degeneration. The limb, shoulder, and pelvic muscles of the gsg-/- mice exhibited progressive muscle hypertrophy and weakness with age, and the findings were similar to those seen in other mouse models for limb-girdle and Duchenne muscular dystrophy. We found that the number of muscle fibers increased with age, and most of the fibers in the hypertrophic muscle were centrally nucleated regenerating fibers. Therefore, muscle hypertrophy of the gsg-/- mice may result from an increase of the number of muscle fibers and probable fiber branching and may not be due to the pseudohypertrophy caused by fibrous and fat tissue replacement, as has been long supposed in muscular dystrophy. The muscle pathology became more 'dystrophic' in mice over 1 year of age when there was a marked variation in fiber size with interstitial fibrosis.
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PMID:Pathological analysis of muscle hypertrophy and degeneration in muscular dystrophy in gamma-sarcoglycan-deficient mice. 1260 1

Mutations in the dystrophin glycoprotein complex, and in particular the sarcoglycan subcomplex, lead to cardiomyopathy and muscular dystrophy. Mice with mutations in gamma-sarcoglycan or delta-sarcoglycan develop cardiomyopathy that is characterized by focal regions of tissue damage. These focally damaged regions constitute 0-5% of cardiac tissue. In cardiomyopathy arising from sarcoglycan mutations, we found that endothelial nitric oxide synthase (eNOS) was significantly increased in focally damaged cardiac myocytes. In addition, we noted that nitric oxide (NO) was also increased in regions of tissue damage and altered membrane permeability. In sarcoglycan mutant mice, regionally increased cardiac NO was associated with hypersensitivity to carbachol and decreased sensitivity to adrenergic stimulation. Inhibition of NO production in sarcoglycan mutant mice was associated with improved recovery after carbachol and isoproterenol infusion. These data provide a mechanism where regional, focal cardiac damage creates pathologic gradients of NO. Moreover, inhibition of nitric oxide synthase corrects defects that arise from pathologic NO gradients.
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PMID:Functional nitric oxide synthase mislocalization in cardiomyopathy. 1487 47

Limb-girdle muscular dystrophy type 2C is an autosomal-recessive disorder caused by mutations in gamma-sarcoglycan encoding gene. This disease is characterized by childhood onset of progressive muscular dystrophy. Because of the clinical presentation, this disorder may be misdiagnosed as a dystrophinopathy. Two males (Patients A and B) from one Turkish family and one male (Patient C) from a Moroccan family had progressive walking disturbances for several years, exercise intolerance, and leg pains. Clinical examination revealed limb-girdle weakness and calf hypertrophy. Serum creatine kinase levels ranged from 1100 to 19000 U/L. The initial findings and course of the disease were less severe in Patient B compared with his brother (Patient A) at the same age. By means of immunohistochemistry on muscle biopsy all patients manifested reduced expression of alpha-, beta-, gamma-, and delta-sarcoglycans. DNA sequence analysis revealed a homozygous splice site mutation in exon 5 (IVS5+2T>C) in the Turkish family. In the patient from the Moroccan family a homozygous nonsense mutation in exon 2 (93G>A;Trp31X) was present. In conclusion, this report describes the clinical, histologic, and immunohistochemical characteristics of three children with limb-girdle muscular dystrophy type 2C. Two novel mutations in the gamma-sarcoglycan gene were present. We found phenotypic differences in two brothers.
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PMID:Novel mutations in three patients with LGMD2C with phenotypic differences. 1508 11

Disruption of the sarcoglycan complex leads to muscle membrane instability and muscular dystrophy in humans and mice. Through the dystrophin glycoprotein complex, sarcoglycan participates in connecting the internal cytoskeleton to the membrane and the extracellular matrix. Integrin alpha7beta1 is also a transmembrane protein of skeletal and cardiac muscle that similarly links the cytoskeleton to the extracellular matrix. Mice lacking integrin alpha7 develop mild muscle degeneration, while sarcoglycan mutant mice display overt muscle degeneration and muscular dystrophy. In sarcoglycan-deficient muscle, integrin alpha7 protein was upregulated at the plasma membrane. To ascertain whether integrin alpha7 upregulation compensates for the loss of the transmembrane sarcoglycan linkage in sarcoglycan-deficient muscle, we generated mice lacking both integrin alpha7 and gamma-sarcoglycan (gxi). These double-mutant gxi mice exhibit profound, rapid muscle degeneration leading to death before one month of age consistent with a weakened cellular attachment to the extracellular matrix. The regenerative capacity of gxi muscle was intact with increased embryonic myosin heavy chain expression, myofiber central nucleation and normal in vivo myoblast differentiation. Therefore, upregulation of integrin alpha7beta1 compensates as a transmembrane muscle cell attachment for sarcoglycan consistent with overlapping roles for sarcoglycan and integrins in mediating cytoskeletal-membrane-extracellular matrix interaction.
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PMID:Genetic compensation for sarcoglycan loss by integrin alpha7beta1 in muscle. 1525 20

Mutations in the genes encoding dystrophin and its associated proteins, the sarcoglycans, lead to muscular dystrophy in humans and in mouse models. In the presence of identical gene mutations, the muscular dystrophy phenotype can be highly variable. Using a mouse model of limb girdle muscular dystrophy engineered with a null allele of gamma-sarcoglycan, we bred the identical gamma-sarcoglycan mutation into four different genetic backgrounds. We found that the gamma-sarcoglycan mutation is least severe in the129SV/J (129) strain and most severe on the DBA 2J JAX (DBA) strain using quantitative measures of Evan's blue dye uptake, as a marker of membrane permeability defects, and hydroxyproline content, as a marker of fibrosis. In addition we show that the DBA mice are most severely affected regardless of gender and age. The enhanced phenotype observed in the DBA strain was not caused by exercise as the DBA mice scored the lowest in a voluntary activity test. The milder phenotype seen in the 129SV/J and C57B6/J strains suggests that these backgrounds contain modifier loci that partially suppress the muscular dystrophy phenotype. Identification of these modifier genes and the associated pathways may lead to novel therapeutic strategies.
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PMID:Genetic background influences muscular dystrophy. 1608 87

A major consequence of muscular dystrophy is that increased membrane fragility leads to high calcium influx and results in muscle degeneration and myonecrosis. Prior reports have demonstrated that increased nitric oxide production via L-arginine treatment of normal and mdx mice resulted in increased expression of utrophin and increased activation of muscle satellite cells, which could ameliorate the dystrophic pathology. We delivered L-arginine to normal and mdx mice, and examined muscles for any functional changes associated with its administration. Treated mdx muscles were less susceptible to contraction-induced damage and exhibited a rightward shift of the force-frequency relationship. Immunoblotting revealed increases in utrophin and gamma-sarcoglycan in the treated muscles. There was also a decrease in Evans blue dye uptake, indicating a reduction in myonecrosis. However, there was no decrease in serum creatine kinase or the proportion of central nuclei, nor any improvement in specific force. Together, these results show that L-arginine treatment can be beneficial to mdx muscle function, perhaps through a combination of enhanced calcium handling and increased utrophin, thereby decreasing muscle degeneration.
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PMID:Systemic administration of L-arginine benefits mdx skeletal muscle function. 1611 42

Loss of the dystrophin glycoprotein complex (DGC) or a subset of its components can lead to muscular dystrophy. However, the patterns of symptoms differ depending on which proteins are affected. Absence of dystrophin leads to loss of the entire DGC and is associated with susceptibility to contractile injury. In contrast, muscles lacking gamma-sarcoglycan (gamma-SG) display little mechanical fragility and still develop severe pathology. Animals lacking dystrophin or gamma-SG were used to identify DGC components critical for sensing dynamic mechanical load. Extensor digitorum longus muscles from 7-wk-old normal (C57), dystrophin- null (mdx), and gamma-SG-null (gsg(-/-)) mice were subjected to a series of eccentric contractions, after which ERK1/2 phosphorylation levels were determined. At rest, both dystrophic strains had significantly higher ERK1 phosphorylation, and gsg(-/-) muscle also had heightened ERK2 phosphorylation compared with wild-type controls. Eccentric contractions produced a significant and transient increase in ERK1/2 phosphorylation in normal muscle, whereas the mdx strain displayed no significant proportional change of ERK1/2 phosphorylation after eccentric contraction. Muscles from gsg(-/-) mice had no significant increase in ERK1 phosphorylation; however, ERK2 phosphorylation was more robust than in C57 controls. The reduction in mechanically induced ERK1 phosphorylation in gsg(-/-) muscle was not dependent on age or severity of phenotype, because muscle from both young and old (age 20 wk) animals exhibited a reduced response. Immunoprecipitation experiments revealed that gamma-SG was phosphorylated in normal muscle after eccentric contractions, indicating that members of the DGC are modified in response to mechanical perturbation. This study provides evidence that the SGs are involved in the transduction of mechanical information in skeletal muscle, potentially unique from the entire DGC.
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PMID:Impact of sarcoglycan complex on mechanical signal transduction in murine skeletal muscle. 1616 59

Biglycan and decorin are small extracellular proteoglycans that interact with cytokines, whose activity they may modulate, and with matrix proteins, particularly collagens. To better understand their role in muscle fibrosis, we investigated expression of decorin and biglycan transcripts and protein in muscle of several forms of muscular dystrophy, and also expression of perlecan, an extracellular proteoglycan unrelated to collagen deposition. In Duchenne muscular dystrophy (DMD) and LAMA2-mutated congenital muscular dystrophy (MDC1A) we also quantitated transcript levels of the profibrotic cytokine TGF-beta1. We examined muscle biopsies from nine DMD patients, aged 2-8 years; 14 BMD (Becker muscular dystrophy) patients (nine aged 1-5 years; five aged 30-37 years); four MDC1A patients (aged 2-7 years); six dysferlin-deficient patients (aged 19-53 years) with mutation ascertained in two, and normal expression of proteins related to limb girdle muscular dystrophies in the others; 10 sarcoglycan-deficient patients: seven with alpha-sarcoglycan mutation, two with beta-sarcoglycan mutation and one with gamma-sarcoglycan mutation (five aged 8-15 years; five aged 26-43 years); and nine children (aged 1-6 years) and 12 adults (aged 16-61 years) suspected of neuromuscular disease, but who had normal muscle on biopsy. Biglycan mRNA levels varied in DMD and MDC1A depending on the quantitation method, but were upregulated in BMD, sarcoglycanopathies and dysferlinopathy. Decorin mRNA was significantly downregulated in DMD and MDC1A, whereas TGF-beta1 was significantly upregulated. Decorin mRNA was normal in paediatric BMD, but upregulated in adult BMD, sarcoglycanopathies and dysferlinopathy. Perlecan transcript levels were similar to those of age-matched controls in all disease groups. By immunohistochemistry, decorin and biglycan were mainly localized in muscle connective tissue; their presence increased in relation to increased fibrosis in all dystrophic muscle. By visual inspection, decorin bands on immunoblot did not differ from those of age-matched controls in all patient groups. However, when the intensity of the bands was quantitated against vimentin and normalized against sarcomeric actin, in DMD and MDC1A the ratio of band intensities was significantly lower than in age-matched controls. Variations in the transcript and protein levels of these proteoglycans in different muscular dystrophies probably reflect the variable disruption of extracellular matrix organization that occurs in these diseases. The significantly lowered decorin levels in DMD and MDC1A may be related to the increased TGF-beta1 levels, suggesting a therapeutic role of decorin in these severe dystrophies.
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PMID:Decorin and biglycan expression is differentially altered in several muscular dystrophies. 1618 58


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