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

The most common form of adult muscular dystrophy, myotonic dystrophy (DM), is caused by the abnormal expansion of the CTG repeat, located in the 3' UTR of the DM gene. The expanded-CTG allele often presents as a diffused band on Southern blot analysis, suggesting somatic mosaicism. In order to study the somatic instability of the CTG repeat, we have investigated the dynamics of the size heterogeneity of the CTG expansion. Size heterogeneity is shown as a smear on Southern blot and is measured by the midpeak-width ratio of the expanded allele to the normal sized allele. The ratio is also corrected for compression in the higher-molecular-weight region. It is found that the size heterogeneity of the expanded-CTG repeats, of 173 DM patients, correlates well with the age of the patient (r = .81, P << .001). The older patients show larger size variation. This correlation is independent of the sex of either the patient or the transmitting parent. The size heterogeneity of the expansion, based on age groups, is also dependent on the size of the expanded trinucleotide repeat. However, obvious size heterogeneity is not observed in congenital cases, regardless of the size of expansion. Comparison of individual patient samples collected at two different times has confirmed that the degree of size heterogeneity increases with age and has revealed a subtle but definite upward shift in the size of the expanded-CTG allele. The progression of the CTG repeat toward larger expansion with age is further confirmed by small-pool PCR assay that resolved the heterogeneous fragments into discrete bands.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Somatic heterogeneity of the CTG repeat in myotonic dystrophy is age and size dependent. 782 66

Sarcoglycanopathies, affecting the dystrophin-associated sarcoglycan (SG) complex, are a heterogeneous group of neuromuscular disorders. A subgroup of these disorders, limb-girdle muscular dystrophy type 2C (LGMD2C) is an autosomal recessive disorder, clinically manifested as an early onset, severe Duchenne-like muscular dystrophy. LGMD2C is caused by mutations in the gamma-SG gene, localized on 13q12. Recently, a number of mutations have been described in that gene, among which C283Y, a "private" Gypsy mutation (eight codons before the 3' end of the gene) is detected. In this article, we report on a single-strand conformation polymorphism (SSCP) method for fast C283Y mutation detection, using direct dry blood spot amplification. The method permits a large number of samples to be easily screened. To check heterozygote carriers of C283Y mutation among Gypsy population in Bulgaria, the SSCP analysis was applied on 400 Gypsy newborns from northeast Bulgaria. Our results show 2.25% of heterozygosity, which means that 1 in 50 Gypsies carries the mutation. Moreover, new SSCP migration patterns were detected that revealed two polymorphisms still unavailable in the literature. One of these changes was 984G-->A, leading to substitution of conserved serine at position 287 with asparagine and the second one is 1049C-->G at the 3' UTR (untranslated region). The present data could help the understanding the role of these sequences for the protein function.
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PMID:C283Y mutation and other C-terminal nucleotide changes in the gamma-sarcoglycan gene in the Bulgarian Gypsy population. 1044 57

We systematically screened the whole coding region of 18 male muscular dystrophy patients whose clinical, histological and laboratory findings suggest Becker muscular dystrophy (present but abnormal dystrophin). No systematic mutation study of a cohort of patients with dystrophin of normal quality but abnormal quantity has been published. The complete coding sequence of the dystrophin gene (11 kb) of each patient was subjected to an automated sequence analysis by using muscle biopsy RNA; 535 bp of the gene promoter and 5'UTR were likewise sequenced. We identified seven disease-causing mutations (40%). Six were novel, including missense, nonsense, small deletion and splice site mutations. Sixty percent (11/18) of patients with decreased quantities of normal molecular weight dystrophin showed no mutation, but most of them had a family history highly suggestive of X-linked inheritance, suggesting transcription or translational deleterious affection, i.e. outside what was screened. Quantitative multiplex fluorescence polymerase chain studies of mutation-negative patients showed normal levels of dystrophin mRNA. In three patients, there was some reduction of the transcript suggesting a deleterious undetected gene change resulted in the reduction of RNA levels. Our data address important structure/function and genotype/phenotype correlations and it suggests that dystrophin protein studies must be interpreted with caution in deletion-negative male muscular dystrophy patients.
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PMID:DNA sequence analysis for structure/function and mutation studies in Becker muscular dystrophy. 1595 89

Myotonic dystrophy (DM1), the most common muscular dystrophy in adults, is caused by an expanded (CTG)n tract in the 3' UTR of the gene encoding myotonic dystrophy protein kinase (DMPK), which results in nuclear entrapment of the 'toxic' mutant RNA and interacting RNA-binding proteins (such as MBNL1) in ribonuclear inclusions. It is unclear if therapy aimed at eliminating the toxin would be beneficial. To address this, we generated transgenic mice expressing the DMPK 3' UTR as part of an inducible RNA transcript encoding green fluorescent protein (GFP). We were surprised to find that mice overexpressing a normal DMPK 3' UTR mRNA reproduced cardinal features of myotonic dystrophy, including myotonia, cardiac conduction abnormalities, histopathology and RNA splicing defects in the absence of detectable nuclear inclusions. However, we observed increased levels of CUG-binding protein (CUG-BP1) in skeletal muscle, as seen in individuals with DM1. Notably, these effects were reversible in both mature skeletal and cardiac muscles by silencing transgene expression. These results represent the first in vivo proof of principle for a therapeutic strategy for treatment of myotonic dystrophy by ablating or silencing expression of the toxic RNA molecules.
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PMID:Reversible model of RNA toxicity and cardiac conduction defects in myotonic dystrophy. 1694 Oct 4

Myotonic muscular dystrophy (DM1) is the most common inherited neuromuscular disorder in adults and is considered the first example of a disease caused by RNA toxicity. Using a reversible transgenic mouse model of RNA toxicity in DM1, we provide evidence that DM1 is associated with induced NKX2-5 expression. Transgene expression resulted in cardiac conduction defects, increased expression of the cardiac-specific transcription factor NKX2-5 and profound disturbances in connexin 40 and connexin 43. Notably, overexpression of the DMPK 3' UTR mRNA in mouse skeletal muscle also induced transcriptional activation of Nkx2-5 and its targets. In human muscles, these changes were specific to DM1 and were not present in other muscular dystrophies. The effects on NKX2-5 and its downstream targets were reversed by silencing toxic RNA expression. Furthermore, using Nkx2-5+/- mice, we show that NKX2-5 is the first genetic modifier of DM1-associated RNA toxicity in the heart.
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PMID:RNA toxicity in myotonic muscular dystrophy induces NKX2-5 expression. 1808 93

Walker-Warburg syndrome (WWS) is an autosomal recessive disorder characterized by congenital muscular dystrophy, brain malformations and structural abnormalities of the eye. We have studied two WWS patients born to non-consanguineous parents, and in both cases, we identified mutations in the fukutin gene responsible for this syndrome. One of the patients carries a homozygous-single nucleotide insertion that produces a frameshift, being this the first time that this insertion has been described in homozygosis and causing a WWS phenotype. The other patient carries two novel mutations, one being a point mutation that produces an amino acid substitution, while the other is a deletion in the 3'UTR that affects the polyadenylation signal of the fukutin gene. This deletion would probably result in the complete loss of the fukutin transcripts from this allele. This is the first time a mutation localized outside of the fukutin coding region has been identified as a cause of WWS.
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PMID:Two new patients bearing mutations in the fukutin gene confirm the relevance of this gene in Walker-Warburg syndrome. 1817 72

Myotonic dystrophy type 1 is caused by the expansion of a CTG repeat in the 3' UTR of the DMPK gene. A length exceeding 50 CTG triplets is pathogenic. Intermediate alleles with 35-49 triplets are not disease-causing but show instability in intergenerational transmissions. We report on the identification of multiple patients with different patterns of CCG and CTC interruptions in the DMPK CTG repeat tract that display unique intergenerational instability. In patients bearing interrupted expanded alleles, the location of the interruptions changed dramatically between generations and the repeats tended to contract. The phenotype for these patients corresponded to the classical form of the disease, but in some cases without muscular dystrophy and possibly with a later onset than expected. Symptomatic patients bearing interrupted intermediate length repeat tracts were also identified, although the role of the interruptions in their phenotype remains unclear. The identification of interruptions in the DMPK repeat has important consequences for molecular genetic testing where they can lead to false negative conclusions.
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PMID:Highly unstable sequence interruptions of the CTG repeat in the myotonic dystrophy gene. 1951 47

Myotonic dystrophy type 1 (DM1) is the most common form of muscular dystrophy in adults, affecting 1/8000 individuals. DM1 is a dominant disorder characterized by multisystemic clinical features affecting skeletal muscle, heart and the nervous and endocrine systems. DM1 is caused by an expansion of CTG trinucleotide repeats within the 3'-untranslated region (3'-UTR) of the DMPK gene. This repeat is polymorphic in normal individuals with alleles ranging from 5 to 37 in length. Repeats exceeding a threshold of approximately 50 and reaching up to a number of 4,000 result in disease. This review offers a detailed description of the scientific findings that have allowed the establishment of the molecular basis of the DM1 in the muscle and nervous systems. Currently, it is known that mutant DM1 transcript accumulates in the nucleus of muscle and neuronal cells sequestering nuclear proteins, such as splicing regulators and transcription factors to form nuclear foci that are observed under inmunofluorescence techniques. This event disturbs the expression of several muscular and neuronal genes impairing cell differentiation, which may explain the multiple symptoms of the disease. Finally, the main findings towards the development of a gene therapy for DM1 are discussed.
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PMID:[Pathogenesis of myotonic dystrophy type 1]. 2007 33

Myotonic dystrophy types 1 and 2 (DM1 and DM2) are forms of muscular dystrophy that share similar clinical and molecular manifestations, such as myotonia, muscle weakness, cardiac anomalies, cataracts, and the presence of defined RNA-containing foci in muscle nuclei. DM2 is caused by an expansion of the tetranucleotide CCTG repeat within the first intron of ZNF9, although the mechanism by which the expanded nucleotide repeat causes the debilitating symptoms of DM2 is unclear. Conflicting studies have led to two models for the mechanisms leading to the problems associated with DM2. First, a gain-of-function disease model hypothesizes that the repeat expansions in the transcribed RNA do not directly affect ZNF9 function. Instead repeat-containing RNAs are thought to sequester proteins in the nucleus, causing misregulation of normal cellular processes. In the alternative model, the repeat expansions impair ZNF9 function and lead to a decrease in the level of translation. Here we examine the normal in vivo function of ZNF9. We report that ZNF9 associates with actively translating ribosomes and functions as an activator of cap-independent translation of the human ODC mRNA. This activity is mediated by direct binding of ZNF9 to the internal ribosome entry site sequence (IRES) within the 5'UTR of ODC mRNA. ZNF9 can activate IRES-mediated translation of ODC within primary human myoblasts, and this activity is reduced in myoblasts derived from a DM2 patient. These data identify ZNF9 as a regulator of cap-independent translation and indicate that ZNF9 activity may contribute mechanistically to the myotonic dystrophy type 2 phenotype.
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PMID:ZNF9 activation of IRES-mediated translation of the human ODC mRNA is decreased in myotonic dystrophy type 2. 2017 32

DM1 (myotonic dystrophy type I) is a common form of muscular dystrophy that affects mainly adults. It is a disease that belongs to the group of defective RNA export diseases, since a major part of the pathogenic mechanism of the disease is the retention of the mutant transcripts in the cell nucleus. The presence of an expanded CUG trinucleotide repeat in the 3'-UTR (3'-untranslated region) of the DMPK (myotonic dystrophy protein kinase) gene causes the attraction of RNA-binding proteins by the nuclear-located mutant transcripts. As a result of the occupation of the RNA-binding proteins, there is defective mis-splicing of several cellular transcripts. This is believed to be a major pathogenic mechanism of the disease and any attempt to repair the activities of the RNA-binding proteins or target the mutant transcripts should be beneficial for the patients. Certain approaches have been described in the literature and they demonstrate progress in various directions. The purpose of the present review is to summarize the successful attempts to tackle the pathogenesis caused by nuclear retention of mutant transcripts in myotonic dystrophy and to discuss the possible gains from such approaches.
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PMID:Tackling the pathogenesis of RNA nuclear retention in myotonic dystrophy. 2069 Sep 4


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