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

We have investigated the expression, using immunohistochemistry, of beta- and gamma-sarcoglycans in the muscles of 20 patients in whom previous screening had revealed a deficiency of alpha-sarcoglycan. alpha-, beta- and gamma-sarcoglycans were absent in 7 patients and variably reduced in 8 patients, in 2 of whom beta-sarcoglycan was more reduced than the alpha- and gamma-proteins. In 5 other patients with variably reduced alpha- and beta-sarcoglycans, gamma-sarcoglycan was completely absent. In all patients the distribution of hyposthenia at disease onset was similar, and predominantly involved pelvic girdle muscles; however, the age at onset and rate of disease progression were highly variable. In severely compromised patients, the onset of disease was before 10 years of age and gamma-sarcoglycan or all three sarcoglycans were absent from muscles. Immunohistochemical analysis of sarcoglycans should be part of routine screening for muscle dystrophies to identify patients with sarcoglycanopathy. Gene analysis is necessary to identify the primary defect; however, sarcoglycan immunohistochemistry may be useful for indicating which gene to investigate. Further biochemical characterization of the interactions between these proteins is required to fully elucidate their roles in causing severe, moderate or mild muscular dystrophy.
 ...
PMID:Concomitant deficiency of beta- and gamma-sarcoglycans in 20 alpha-sarcoglycan (adhalin)-deficient patients: immunohistochemical analysis and clinical aspects. 922 27

Four of the currently recognized autosomal recessive limb-girdle muscular dystrophies (LGMD type 2C-F) are caused by mutations in the genes encoding components of the sarcoglycan complex. LGMD 2C, caused by mutations in gamma-sarcoglycan, is prevalent in northern Africa, especially in Tunisia, where this type of muscular dystrophy was originally described. Although the disease initially was assumed to be genetically homogeneous in this region, linkage to the alpha-sarcoglycan locus (LGMD 2D) has also been found. We have now identified the first Tunisian family with beta-sarcoglycanopathy (LGMD 2E), further adding to the genetic heterogeneity of autosomal recessive LGMD in this population. Direct sequencing of the beta-sarcoglycan gene revealed a homozygous mutation (G272-->T, Arg91Leu) in exon 3. This change affects the same arginine residue in the immediate extracellular domain of the protein that was mutated to a proline (G272-->C, Arg91Pro) in a Brazilian family with a severe form of the disease. Immunohistochemical analysis for the sarcoglycan complex demonstrates absence of the known components of the complex in both of these families. We postulate that the immediate extracellular domain of beta-sarcoglycan may be important for the assembly and/or maintenance of this complex, potentially mediated by disulfide-bond formation to another sarcoglycan via the single cysteine residue in that domain.
 ...
PMID:LGMD 2E in Tunisia is caused by a homozygous missense mutation in beta-sarcoglycan exon 3. 963 1

Limb girdle muscular dystrophy is a heterogeneous group of disorders. One autosomal recessive subtype, LGMD2C, has been linked to chromosome 13, and is caused by gamma-sarcoglycan deficiency in muscle. This report describes a novel missense mutation identified in a large consanguineous Dutch family with LGMD. This mutation leads to reduction of gamma-sarcoglycan, and gives rise to a childhood-onset, slowly-progressive dystrophy.
 ...
PMID:A novel gamma-sarcoglycan mutation causing childhood onset, slowly progressive limb girdle muscular dystrophy. 967 83

Limb-girdle muscular dystrophy type 2C (LGMD2C) is an autosomal recessive muscular dystrophy with primary gamma-sarcoglycan deficiency, generally associated with a severe clinical course. gamma-sarcoglycan, a 35kDa dystrophin-associated protein, is encoded by a single gene on chromosome 13q12. Six different mutations have been described in that gene, and it has been proved they are the origin of the disease. One of these mutations (C283Y), a G-->A transition in codon 283, was recently and exclusively identified in Gypsy patients from different European countries. We report the study of 11 LGMD2C unrelated Gypsy families (nine Spanish and two Portugese). The muscle biopsies of these patients showed a drastically decreased immunostaining with alpha and gamma-sarcoglycan antibodies. All the patients were homozygous for C283Y missense mutation, and all affected chromosomes (patients and heterozygous relatives) carried the allele 5 (112 bp) of the intragenic microsatellite D13S232. Unexpectedly, this allele is most frequent in the Caucasian population but not in the normal Gypsy population. The clinical severity of all patients demonstrates that the C283Y missense mutation in a homozygous state causes a severe LGMD2C (DMD-like). The elevated number of families ascertained let us assume that LGMD2C is prevalent in the Gypsy population, and that all the families have inherited a founding mutation.
 ...
PMID:Severe limb girdle muscular dystrophy in Spanish gypsies: further evidence for a founder mutation in the gamma-sarcoglycan gene. 978 Oct 48

The BIO14.6 hamster is an extensively used animal model of autosomal recessive cardiomyopathy and muscular dystrophy. Recently, a large deletion in the 5' end of the delta-sarcoglycan gene was found to be the primary genetic defect in the hamster. In the present investigation, we studied the effects of the delta-sarcoglycan deletion on transcription, expression, and function of the dystrophin-glycoprotein complex in skeletal and cardiac muscle. We demonstrated that in striated muscle the genetic defect leads to the complete deficiency of delta-sarcoglycan and a concomitant loss of alpha-, beta-, and gamma-sarcoglycan. In addition, absence of the sarcoglycan complex reduced the expression of alpha-dystroglycan in striated muscle fibers. These findings indicated that the primary defect in the BIO14.6 hamster leads to the dissociation of the dystroglycan complex from the sarcoglycan complex and disrupted anchorage of alpha-dystroglycan to the cell surface. Using intravenous injection of Evans blue dye as an in vivo tracer assay, we demonstrated that perturbation of the dystrophin-glycoprotein complex caused extensive fiber damage in skeletal and cardiac muscle of the BIO14.6 hamster. Based on our results, we propose that loss of delta-sarcoglycan results in the impairment of sarcolemmal integrity, finally leading to muscular dystrophy and cardiomyopathy.
 ...
PMID:Molecular pathogenesis of muscle degeneration in the delta-sarcoglycan-deficient hamster. 981 55

A group of 204 muscular dystrophy patients were screened for immunohistochemical and biochemical alpha-sarcoglycan defect and their DNA was analyzed for pathogenetic mutation in the four sarcoglycan genes. We identified 21 patients with alpha-, beta-, or gamma-sarcoglycan gene mutations. Patients with alpha-sarcoglycan gene mutations were clinically heterogeneous and showed either a rapid progressive or a late-onset slow course. In the slowly evolving group, a residual alpha-sarcoglycan protein was present, and its level correlated with a milder disease course and significant later inability to stand up from the floor (p < 0.00005). Most patients with beta- and gamma-sarcoglycan gene mutations presented a severe clinical course. There is a considerably different pattern of muscle involvement and disease course in these disorders, compared with dystrophinopathies.
 ...
PMID:The clinical spectrum of sarcoglycanopathies. 992 70

Mutations in the sarcoglycan genes cause autosomal-recessive muscular dystrophies. Because sarcoglycan genes and their protein products are highly expressed both in skeletal and cardiac muscle, patients with these mutations might be expected to be at risk to develop dilated cardiomyopathy. We therefore studied 13 patients with alpha-, beta-, gamma-sarcoglycan gene mutations by thorough cardiological assessment. Electrocardiographic or echocardiographic abnormalities were observed in about 30% of cases showing a severe course of muscular dystrophy. No correlation was found between the presence of cardiac abnormalities and the type of mutation or sarcoglycan gene involved. The cardiac involvement was never severe, but it may be detected in early stages of the muscle disease. The absence of overt cardiac dysfunction may be due to lower sarcoglycan protein expression in cardiac than skeletal muscle or to less sarcolemmal instability at the myocardial level, possibly related to the different distribution of forces generated by contraction of the myocardium with respect to proximal limb-girdle muscles.
 ...
PMID:Heart involvement in muscular dystrophies due to sarcoglycan gene mutations. 1020 82

There is increasing evidence that gamma-sarcoglycan is absent and other sarcoglycans are reduced in patients with the limb-girdle muscular dystrophy type 2C (LGMD2C) form of severe childhood autosomal recessive muscular dystrophy. In the present investigation, we combined microspectrofluorimetry and electron microscopy techniques to investigate the physiological function and the ultrastructure of control and LGMD2C myotubes. Results obtained from Ca2+ measurements showed that the resting level of the cytosolic free calcium ([Ca2+ ]i ) in control myotubes was 73+/-3.4 nmol/l (mean+/-se, n=35) and in LGMD2C myotubes was 69+/-4 nmol/l (n=44). Carbachol (CCh, 10 micromol/l ) induced a 335+/-10 nmol/l (n=8) rise in [Ca2+ ]i in control myotubes and 531.9+/-32 nmol/l (n=23) in LGMD2C myotubes. Similarly, elevations of [Ca2+ ]i by 35 mmol/l K+ were 324+/-32 nmol/l (n=8) in control myotubes and 442.8+/-24 nmol/l (n=22) in LGMD2C myotubes. Caffeine (10 mmol/l) activated similar [Ca2+]i peaks in control and LGMD2C myotubes but induced a biphasic response in LGMD2C in four out of 12 myotubes and only a monophasic response in control myotubes. The ultrastructural results showed that the plasma membrane was abnormally indented and convoluted in both the LGMD2C biopsy and the LGMD2C cultured myotubes. It is suggested that the reduction in components of the dystrophin-glycoprotein complex results in the instability and an increase in the surface area of the plasma membrane, which may result in a higher population of Ca2+ channels in the LGMD2C myotubes.
 ...
PMID:Calcium homeostasis and ultrastructural studies in a patient with limb girdle muscular dystrophy type 2C. 1041 66

In humans, mutations in the genes encoding components of the dystrophin-glycoprotein complex cause muscular dystrophy. Specifically, primary mutations in the genes encoding alpha-, beta-, gamma-, and delta-sarcoglycan have been identified in humans with limb-girdle muscular dystrophy. Mice lacking gamma-sarcoglycan develop progressive muscular dystrophy similar to human muscular dystrophy. Without gamma-sarcoglycan, beta- and delta-sarcoglycan are unstable at the muscle membrane and alpha-sarcoglycan is severely reduced. The expression and localization of dystrophin, dystroglycan, and laminin-alpha2, a mechanical link between the actin cytoskeleton and the extracellular matrix, appears unaffected by the loss of sarcoglycan. We assessed the functional integrity of this mechanical link and found that isolated muscles lacking gamma-sarcoglycan showed normal resistance to mechanical strain induced by eccentric muscle contraction. Sarcoglycan-deficient muscles also showed normal peak isometric and tetanic force generation. Furthermore, there was no evidence for contraction-induced injury in mice lacking gamma-sarcoglycan that were subjected to an extended, rigorous exercise regimen. These data demonstrate that mechanical weakness and contraction-induced muscle injury are not required for muscle degeneration and the dystrophic process. Thus, a nonmechanical mechanism, perhaps involving some unknown signaling function, likely is responsible for muscular dystrophy where sarcoglycan is deficient.
 ...
PMID:Muscle degeneration without mechanical injury in sarcoglycan deficiency. 1048 93

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.
 ...
PMID:Sarcoglycans in muscular dystrophy. 1067 64


<< Previous 1 2 3 4 5 Next >>