Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1762617 (weakness)
 37,932 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myotonic dystrophies (DMs) are characterised by highly variable clinical manifestations consisting of muscle weakness and atrophy, and a wide spectrum of extramuscular manifestations. In both DM1 and DM2 forms, expanded nucleotide sequences cause the accumulation of mutant transcripts in the nucleus, thus deregulating the function of some RNA-binding proteins and providing a plausible explanation for the multifactorial phenotype of DM patients. However, at the skeletal muscle level, no mechanistic explanation for the muscle wasting has so far been proposed. We therefore performed a study in situ by immunoelectron microscopy on biceps brachii biopsies from DM1, DM2 and healthy subjects, providing the first ultrastructural evidence on the distribution of some nuclear ribonucleoprotein (RNP)-containing structures and molecular factors involved in pre-mRNA transcription and maturation in dystrophic myonuclei. Our results demonstrated an accumulation of splicing and cleavage factors in myonuclei of both DM1 and DM2 patients, suggesting an impairment of post-transcriptional pre-mRNA pathways. The transcription of the expanded sequences in DM myonuclei would therefore hamper functionality of the whole splicing machinery, slowing down the intranuclear molecular trafficking; this would reduce the capability of myonuclei to respond to anabolic stimuli thus contributing to muscle wasting.
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PMID:RNA processing is altered in skeletal muscle nuclei of patients affected by myotonic dystrophy. 2138 85

Myotonic dystrophy is the most common muscular dystrophy in adults and the first recognized example of an RNA-mediated disease. Congenital myotonic dystrophy (CDM1) and myotonic dystrophy of type 1 (DM1) or of type 2 (DM2) are caused by the expression of mutant RNAs containing expanded CUG or CCUG repeats, respectively. These mutant RNAs sequester the splicing regulator Muscleblind-like-1 (MBNL1), resulting in specific misregulation of the alternative splicing of other pre-mRNAs. We found that alternative splicing of the bridging integrator-1 (BIN1) pre-mRNA is altered in skeletal muscle samples of people with CDM1, DM1 and DM2. BIN1 is involved in tubular invaginations of membranes and is required for the biogenesis of muscle T tubules, which are specialized skeletal muscle membrane structures essential for excitation-contraction coupling. Mutations in the BIN1 gene cause centronuclear myopathy, which shares some histopathological features with myotonic dystrophy. We found that MBNL1 binds the BIN1 pre-mRNA and regulates its alternative splicing. BIN1 missplicing results in expression of an inactive form of BIN1 lacking phosphatidylinositol 5-phosphate-binding and membrane-tubulating activities. Consistent with a defect of BIN1, muscle T tubules are altered in people with myotonic dystrophy, and membrane structures are restored upon expression of the normal splicing form of BIN1 in muscle cells of such individuals. Finally, reproducing BIN1 splicing alteration in mice is sufficient to promote T tubule alterations and muscle weakness, a predominant feature of myotonic dystrophy.
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PMID:Misregulated alternative splicing of BIN1 is associated with T tubule alterations and muscle weakness in myotonic dystrophy. 2162 81

Myotonic dystrophies (DMs) are autosomal dominant disorders with multisystemic clinical features. DMs are categorized as DM1, caused by a (CTG)n expansion mutation in 19q13, and DM2, caused by a (CCTG)n expansion mutation in 3q21. The clinical features of DM2 are diffuse and proximal dominant weakness, wasting, myotonia, cardiac problems, cataracts, and insulinresistance. DM2 is milder than DM1. We compared the clinical features of both DMs and studied a Japanese patient with DM2 who had expansion mutations different from those usually attributed to the disease and originally discovered by European researchers. The detailed clinical features of the Japanese DM2 patient are described.
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PMID:[Myotonic dystrophy type 2]. 2206 67

Myotonic dystrophy type 1 and type 2 (DM1 and DM2) are genetic diseases in which mutant transcripts containing expanded CUG or CCUG repeats cause cellular dysfunction by altering the processing or metabolism of specific mRNAs and miRNAs. The toxic effects of mutant RNA are mediated partly through effects on proteins that regulate alternative splicing. Here we show that alternative splicing of exon 29 (E29) of Ca(V)1.1, a calcium channel that controls skeletal muscle excitation-contraction coupling, is markedly repressed in DM1 and DM2. The extent of E29 skipping correlated with severity of weakness in tibialis anterior muscle of DM1 patients. Two splicing factors previously implicated in DM1, MBNL1 and CUGBP1, participated in the regulation of E29 splicing. In muscle fibers of wild-type mice, the Ca(V)1.1 channel conductance and voltage sensitivity were increased by splice-shifting oligonucleotides that induce E29 skipping. In contrast to human DM1, expression of CUG-expanded RNA caused only a modest increase in E29 skipping in mice. However, forced skipping of E29 in these mice, to levels approaching those observed in human DM1, aggravated the muscle pathology as evidenced by increased central nucleation. Together, these results indicate that DM-associated splicing defects alter Ca(V)1.1 function, with potential for exacerbation of myopathy.
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PMID:Muscle weakness in myotonic dystrophy associated with misregulated splicing and altered gating of Ca(V)1.1 calcium channel. 2214 91

Myotonic dystrophy type 1 (DM1) and type 2 (DM2) are autosomal dominant disorders classically characterized by muscle weakness, myotonia, and early-onset cataracts. Patients may also experience dysfunction of the heart, brain, gastrointestinal, endocrine, skin, and respiratory systems. The pathogenesis of myotonic dystrophy is related to trinucleotide (DM1) and tetranucleotide (DM2) repeat expansions that produce toxic mutant mRNA with subsequent interference of RNA-splicing mechanisms. Optimal disease management includes symptomatic care, screens for asymptomatic disease, counseling, and a multidisciplinary approach. The authors review the pathogenesis, clinical features, diagnostic tests, and standard management of DM1 and DM2 and outline promising clinical research for patients with these disorders.
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PMID:Myotonic dystrophy: from bench to bedside. 2311 49

Myotonic dystrophies (DMs) are autosomal dominant disorders with multisystemic clinical features. DMs are categorized as DM1, caused by a (CTG)n expansion mutation in 19q13, and DM2, caused by a (CCTG)n expansion mutation in 3q21. Clinical feature of DM2 are diffuse and proximal dominant weakness, wasting, myotonia, cardiac problems, cataracts, insulin-resistance. DM2 is considered to milder form than DM1. Here We compared clinical feature in both DMs. We identified a Japanese patient with DM2 and showed clinical features same as a past report. But DM2 is clinically variable, further investigation of Japanese patients is needed in order to confirm these findings in Japan.
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PMID:[Myotonic dystrophy type 2]. 2319 85

We report an unusual case involving a patient with myotonia. A 57-year-old man had multisystemic symptoms including skeletal muscle weakness, atrophy and percussion myotonia, cataract, heart involved, gastrointestinal tract symptoms, and urinary incontinence. The electromyography revealed myotonic discharges. Muscle biopsy showed myopathic features and a striking number of ring fibers. It was genetically proven that the case was not myotonic dystrophy type 1 (DM1) or 2 (DM2). The case might be DM3 or an unusual case of unclassified myopathy with multisystemic damage.
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PMID:An unusual case with myotonia. 2346 22

Myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2) are multisystemic diseases that primarily affect skeletal muscle, causing myotonia, muscle atrophy, and muscle weakness. DM1 and DM2 pathologies are caused by expansion of CTG and CCTG repeats in non-coding regions of the genes encoding myotonic dystrophy protein kinase (DMPK) and zinc finger protein 9 (ZNF9) respectively. These expansions cause DM pathologies through accumulation of mutant RNAs that alter RNA metabolism in patients' tissues by targeting RNA-binding proteins such as CUG-binding protein 1 (CUGBP1) and Muscle blind-like protein 1 (MBNL1). Despite overwhelming evidence showing the critical role of RNA-binding proteins in DM1 and DM2 pathologies, the downstream pathways by which these RNA-binding proteins cause muscle wasting and muscle weakness are not well understood. This review discusses the molecular pathways by which DM1 and DM2 mutations might cause muscle atrophy and describes progress toward the development of therapeutic interventions for muscle wasting and weakness in DM1 and DM2. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.
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PMID:Molecular mechanisms of muscle atrophy in myotonic dystrophies. 2379 88

Myotonic dystrophy type 2 (DM2) is more common than DM1 in Europe and is considered a rare cause of myotonic dystrophies in Asia. Its clinical course is also milder with more phenotypic variability than DM1. We herein describe the first known Asian family (three affected siblings) with DM2 based on clinical and genetic analyses. Notably, two of the affected siblings were previously diagnosed with limb-girdle muscular dystrophy. Myotonia (the inability of the muscle to relax) was absent or only faintly present in these individuals. The third sibling had grip myotonia and is the first known Asian DM2 patient. The three DM2 siblings share several systemic characteristics, including late-onset, proximal-dominant muscle weakness, diabetes, cataracts and asthma. Repeat-primed PCR across the DM2 repeat revealed a characteristic ladder pattern of a CCTG expansion in all siblings. Southern blotting analysis identified the presence of 3400 repeats. Further DM2 studies in Asian populations are needed to define the clinical presentation of Asian DM2 and as yet unidentified phenotypic differences from Caucasian patients.
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PMID:Clinical and genetic analysis of the first known Asian family with myotonic dystrophy type 2. 2443 May 76

Myotonic dystrophy (DM) is the most common adult muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia and multiorgan involvement. To date two distinct forms caused by similar mutations have been identified. Myotonic dystrophy type 1 (DM1, Steinert's disease) was described more than 100 years ago and is caused by a (CTG)n expansion in DMPK, while myotonic dystrophy type 2 (DM2) was identified only 18 years ago and is caused by a (CCTG)n expansion in ZNF9/CNBP. When transcribed into CUG/CCUG-containing RNA, mutant transcripts aggregate as nuclear foci that sequester RNA-binding proteins, resulting in spliceopathy of downstream effector genes. Despite clinical and genetic similarities, DM1 and DM2 are distinct disorders requiring different diagnostic and management strategies. DM1 may present in four different forms: congenital, early childhood, adult onset and late-onset oligosymptomatic DM1. Congenital DM1 is the most severe form of DM characterized by extreme muscle weakness and mental retardation. In DM2 the clinical phenotype is extremely variable and there are no distinct clinical subgroups. Congenital and childhood-onset forms are not present in DM2 and, in contrast to DM1, myotonia may be absent even on EMG. Due to the lack of awareness of the disease among clinicians, DM2 remains largely underdiagnosed. The delay in receiving the correct diagnosis after onset of first symptoms is very long in DM: on average more than 5 years for DM1 and more than 14 years for DM2 patients. The long delay in the diagnosis of DM causes unnecessary problems for the patients to manage their lives and anguish with uncertainty of prognosis and treatment.
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PMID:Clinical aspects, molecular pathomechanisms and management of myotonic dystrophies. 2480 43


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