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

Morphological, morphometrical, histoenzymological, immunocytochemical and biochemical analysis were performed on muscle biopsies taken from patients suffering from tunisian autosomal recessive Duchenne-like muscular dystrophy (TDLMD) selected both by Duchenne-like clinical criteria and by the presence of normal dystrophin. Data were compared to that obtained from DMD biopsies characterized by the absence of dystrophin. The distribution of myosin heavy chain isoforms, desmin, vimentin and titin were determined in type I and type II muscle fibers. The protein pattern appeared to be less affected in TDLMD than in DMD biopsies. The regenerating fibers were mainly but not exclusively type IIC; a noticeable percentage of both type I and type II fibers coexpressed fast and slow MHC isoforms in TDLMD. This percentage was lower than in DMD. The expression of embryonic, fetal, and fast/slow myosin isoforms in type IIC fibers in TDLMD and DMD suggest different fiber type transformations in these two diseases.
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PMID:Expression of myosin isoforms and of desmin, vimentin and titin in Tunisian Duchenne-like autosomal recessive muscular dystrophy. 806 3

A genome scan with highly polymorphic markers has established linkage for tibial muscular dystrophy (TMD), a recently described late onset distal myopathy, to a novel myopathy locus on chromosome 2q31. The mode of inheritance in TMD is autosomal dominant and the typical symptom of ankle dorsiflexion weakness appears in the fourth to seventh decade. Weakness of lower leg muscles is slowly progressive eventually causing a moderate foot drop. Overall disability usually remains mild even in elderly patients and walking ability is preserved throughout the patient's lifetime. The main target of the disease, the tibial anterior muscle, shows progressive dystrophic changes with rimmed vacuoles at the early stages and complete replacement pathology at later stages of the disease. The linkage studies in four different TMD families revealed a common core haplotype with a set of markers on the chromosome 2q31 locus. This indicates one major ancient founder mutation for TMD in Finland. There is one superior candidate gene on the 2q31 locus, the gene encoding a giant protein titin, expressed in heart and skeletal muscle.
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PMID:Tibial muscular dystrophy--from clinical description to linkage on chromosome 2q31. 967 87

The striated muscle sarcomeres are highly organized structures composed of actin (thin) and myosin (thick) filaments that slide past each other during contraction. The integrity of sarcomeres is controlled by a set of structural proteins, among which are titin, a giant molecule that contains several immunoglobulin (Ig)-like domains and associates with thin and thick filaments, and [alpha]-actinin, an actin cross-linking protein. Mutations in several sarcomeric and sarcolemmal proteins have been shown to result in muscular dystrophy and cardiomyopathy. On the other hand, the disease genes underlying several disease forms remain to be identified. Here we describe a novel 57 kDa cytoskeletal protein, myotilin. Its N-terminal sequence is unique, but the C-terminal half contains two Ig-like domains homologous to titin. Myotilin is expressed in skeletal and cardiac muscle, it co-localizes with [alpha]-actinin in the sarcomeric I--bands and directly interacts with [alpha]-actinin. The human myotilin gene maps to chromosome 5q31 between markers AFM350yB1 and D5S500. The locus of a dominantly inherited limb-girdle muscular dystrophy (LGMD1A) resides in an overlapping narrow segment, and a new type of distal myopathy with vocal cord and pharyngeal weakness (VCPMD) has been mapped to the same locus. The muscle specificity and apparent role as a sarcomeric structural protein raise the possibility that defects in the myotilin gene may cause muscular dystrophy.
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PMID:Myotilin, a novel sarcomeric protein with two Ig-like domains, is encoded by a candidate gene for limb-girdle muscular dystrophy. 1036 80

Muscular dystrophy with myositis (mdm) is a recessive mouse mutation that causes severe and progressive muscular degeneration. Here we report the identification of the mdm mutation as a complex rearrangement that includes a deletion and a LINE insertion in the titin (Ttn) gene. Mutant allele-specific splicing results in the deletion of 83 amino acids from the N2A region of TTN, a domain thought to bind calpain-3 (CAPN3) the product of the human limb-girdle muscular dystrophy type 2A (LGMD2A) gene. The Ttn(mdm) mutant mouse may serve as a model for human tibial muscular dystrophy, which maps to the TTN locus at 2q31 and shows a secondary reduction of CAPN3 similar to that observed in mdm skeletal muscle. This is the first demonstration that a mutation in Ttn is associated with muscular dystrophy and provides a novel animal model to test for functional interactions between TTN and CAPN3.
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PMID:The muscular dystrophy with myositis (mdm) mouse mutation disrupts a skeletal muscle-specific domain of titin. 1182 83

Tibial muscular dystrophy (TMD) is an autosomal dominant late-onset distal myopathy linked to chromosome 2q31. The linked region includes the giant TTN gene, which encodes the central sarcomeric protein, titin. We have previously shown a secondary calpain-3 defect to be associated with TMD, which further underscored that titin is the candidate. We now report the first mutations in TTN to cause a human skeletal-muscle disease, TMD. In Mex6, the last exon of TTN, a unique 11-bp deletion/insertion mutation, changing four amino acid residues, completely cosegregated with all tested 81 Finnish patients with TMD in 12 unrelated families. The mutation was not found in 216 Finnish control samples. In a French family with TMD, a Leu-->Pro mutation at position 293,357 in Mex6 was discovered. Mex6 is adjacent to the known calpain-3 binding site Mex5 of M-line titin. Immunohistochemical analysis using two exon-specific antibodies directed to the M-line region of titin demonstrated the specific loss of carboxy-terminal titin epitopes in the TMD muscle samples that we studied, thus implicating a functional defect of the M-line titin in the genesis of the TMD disease phenotype.
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PMID:Tibial muscular dystrophy is a titinopathy caused by mutations in TTN, the gene encoding the giant skeletal-muscle protein titin. 1214 47

We report a Belgian family with autosomal dominant, late-onset, distal myopathy with selective foot extensor muscle involvement of the lower legs. Linkage to the tibial muscular dystrophy (TMD) locus 2q31 was not evident at first because of incomplete disease penetrance in a 50-year-old asymptomatic family member. An abnormal tibialis anterior muscle biopsy established her subclinical status and linkage of the family to the TMD locus. Mutation analysis showed a disease-specific, heterozygous point mutation in the last exon, Mex6, of the titin gene. This is the third mutation found in TMD and the second European family with TMD outside the Finnish population, suggesting that titinopathies may occur in various populations.
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PMID:Tibial muscular dystrophy in a Belgian family. 1289 79

Titin, the biggest single (poly) peptide found in humans, and throughout nature so far, was long considered as a good candidate for inherited muscle diseases. However, disease-causing defects were not known until recently, when this central sarcomeric protein was associated with human skeletal tibial muscular dystrophy (TMD/LGMD2J), dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Several mutations in different parts of titin have now been identified and more are expected. Spontaneous mouse and zebrafish mutants have also been reported. Experimental knock-outs are not viable, even in cases where just a c-terminal part of the gene was silenced, telling something of the basic importance of titin for life. In this article we review the current known structure and functions of this elementary molecule with some emphasis on the only defects so far known to cause human skeletal muscle disease, mutations in the c-terminal M-line part of titin.
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PMID:The role of titin in muscular disorders. 1457 68

Muscular dystrophy with myositis (mdm) is a recessive mouse mutation that is caused by a small deletion in the giant elastic muscle protein titin. Homozygous mdm/mdm mice develop a progressive muscular dystrophy, leading to death at approximately 2 months of age. We surveyed the transcriptomes of skeletal muscles from 24 day old homozygous mdm/mdm and +/+ wild-type mice, an age when MDM animals have normal passive and active tensions and sarcomeric structure. Of the 12488 genes surveyed (U74 affymetrix array), 75 genes were twofold to 30-fold differentially expressed, including CARP (cardiac ankyrin repeat protein), ankrd2/Arpp (a CARP-like protein) and MLP (muscle LIM protein), all of which associate with the titin filament system. The four genes most strongly affected (eightfold to 30-fold change) were all members of the CARP-regulated Nkx-2.5-dependent signal pathway, and CARP mRNA level was 30-fold elevated in MDM skeletal muscle tissues. The CARP protein overexpressed in MDM became associated with the I-band region of the sarcomere. The mdm mutation excises the C-terminal portion of titin's N2A region, abolishing its interaction with p94/calpain-3 protease. Thus, the composition of the titin N2A protein complex is altered in MDM by incorporation of CARP and loss of p94/calpain-3. These changes were absent from the following control tissues (1). cardiac muscles from homozygous mdm/mdm animals, (2). skeletal and cardiac muscle from heterozygous mdm/+ animals, and (3). dystrophic muscles from MDX mice. Thus, the altered composition of the titin N2A complex is specific for the titin-based skeletal muscular dystrophy in MDM.
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PMID:Induction and myofibrillar targeting of CARP, and suppression of the Nkx2.5 pathway in the MDM mouse with impaired titin-based signaling. 1474 Dec 10

Distal myopathies are a heterogeneous group of genetic disorders characterized clinically by progressive muscular weakness and atrophy beginning in the hands or feet, and pathologically by myopathic changes in skeletal muscles. Five distinct distal myopathies are identified, among them four have been recently defined by their gene and causative mutations. They are classified according to age at onset, mode of inheritance, and muscle groups initially involved into the following: Laing myopathy (infancy onset, autosomal dominant inheritance, onset in anterior compartment of legs) caused by mutations in a myosin gene (MYH7) on chromosome 14q; Nonaka myopathy (early adult onset, autosomal recessive inheritance, onset in anterior compartment of legs), identical to quadriceps-sparing familial inclusion myopathy, caused by mutations in the GNE gene on chromosome 9p-q; Miyoshi myopathy (early adult onset, autosomal recessive inheritance, onset in posterior compartment of legs) caused by mutations in the dysferlin gene on chromosome 2p; Welander myopathy (late adult onset, autosomal dominant inheritance, onset in hands) linked to chromosome 2p; Udd/Markesbery-Griggs myopathy (late adult onset, autosomal dominant inheritance, onset in anterior compartment of legs) caused by mutations in the titin gene on chromosome 2q. Except for Miyoshi myopathy, which has a striking elevated serum creatine kinase level and the typical findings of muscular dystrophy, most of the distal myopathies have normal or midly elevated creatine kinase levels and share the common pathologic feature of rimmed vacuoles.
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PMID:[Distal myopathies]. 1503 79

The limb-girdle muscular dystrophies are a diverse group of muscle-wasting disorders characteristically affecting the large muscles of the pelvic and shoulder girdles. Molecular genetic analyses have demonstrated causative mutations in the genes encoding a disparate collection of proteins involved in all aspects of muscle cell biology. Muscular dystrophy includes a spectrum of disorders caused by loss of the linkage between the extracellular matrix and the actin cytoskeleton. Within this are the forms of limb-girdle muscular dystrophy caused by deficiencies of the sarcoglycan complex and by aberrant glycosylation of alpha-dystroglycan caused by mutations in the fukutin-related protein gene. However, other forms of this disease have distinct pathophysiological mechanisms. For example, deficiency of dysferlin disrupts sarcolemmal membrane repair, whilst loss of calpain-3 may exert its pathological influence either by perturbation of the IkappaBalpha/NF-kappaB pathway, or through calpain-dependent cytoskeletal remodelling. Caveolin-3 is implicated in numerous cell-signalling pathways and involved in the biogenesis of the T-tubule system. Alterations in the nuclear lamina caused by mutations in laminA/C, sarcomeric changes in titin, telethonin or myotilin at the Z-disc, and subtle changes in the extracellular matrix proteins laminin-alpha2 or collagen VI can all lead to a limb-girdle muscular dystrophy phenotype, although the specific pathological mechanisms remain obscure. Differential diagnosis of these disorders requires the careful application of a broad range of disciplines: clinical assessment, immunohistochemistry and immunoblotting using a panel of antibodies and extensive molecular genetic analyses.
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PMID:Limb-girdle muscular dystrophies--from genetics to molecular pathology. 1504 7


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