Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q00604 (X-linked)
 16,883 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DMD and BMD are now understood at the genetic, biochemical, and molecular levels. At the genetic level, both disorders result from mutations of the X-linked gene encoding dystrophin. At the biochemical level, DMD results from the deficiency of a large protein called dystrophin, whereas BMD results when dystrophin is present, though abnormal in either amount or molecular structure. To date, thousands of patients have been analyzed for mutations of the dystrophin gene in peripheral blood DNA or alterations of the dystrophin protein in muscle tissue. The severity of the clinical phenotype of these patients has been compared with their dystrophin gene mutations and corresponding dystrophin protein alterations, revealing an unexpectedly high degree of correlation. Thus, information derived from the molecular analysis (DNA or protein) of a particular patient provides a "molecular diagnosis," which is highly predictive of the clinical course that patient can be expected to follow. Because molecular diagnoses are independent of the patient's age, they provide a prognosis for the large majority of muscular dystrophy patients even before clinical symptoms of their disease become apparent. Such prognostic molecular diagnoses have proven particularly valuable when the patient is an isolated case, with no family history for the disorder. Prenatal genetic diagnosis of DMD or BMD may involve use of Southern blot or PCR techniques to search for a deletion in the DNA of at-risk fetuses or more complicated family linkage studies using intragenic and flanking RFLPs. More recently, assay of dystrophin content in fetal skeletal or cardiac muscle from at-risk abortuses has been accomplished, allowing definitive discrimination of affected and normal fetuses in cases in which deletion analyses and family DNA studies were equivocal. In utero fetal skeletal muscle biopsy for dystrophin protein assay has actually been accomplished in at least one at-risk pregnancy in which family DNA studies were uninformative. Dystrophin was present in skeletal muscle from this 20-week-old male fetus, and the pregnancy continued, resulting in the term birth of a healthy male infant. The future holds exciting opportunities for neonatal screening and treatment of these devastating neuromuscular diseases.
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PMID:Duchenne and Becker muscular dystrophies: genetics, prenatal diagnosis, and future prospects. 228 31

The dystrophin gene has been mapped to a pair of microchromosomes in Gallus domesticus. In situ hybridization using a pool of biotinylated human cDNA probes allowed detection of this huge single-copy sequence without having to employ isotopic labeling. The autosomal nature of the DMD gene in chicken is supported by molecular data from quantitative Southern blot analysis and is in sharp contrast to that in all eutherian mammals studied, where it is a characteristically X-linked locus. With previous data taken into consideration, these results should prove significant in understanding the evolution of sex chromosomes during speciation as well as highlighting the importance of avian microchromosomes.
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PMID:The dystrophin gene is autosomally located on a microchromosome in chicken. 228 74

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD), a much milder form of the disease where the age of onset can sometimes be as late as the third or fourth decade of life, are caused by mutations in the same X-linked gene, a 14 kilobase (kb) transcript which is spread over more than 2 megabases of the human X chromosome. The corresponding protein, dystrophin, has a relative molecular mass of 400,000. Most mutations causing DMD and BMD are deletions and deletions associated with both phenotypes are observed throughout the gene sequence. This observation led to the suggestion that DMD patients possess deletions that disrupt the reading frame of the protein, whereas BMD patients have deletions that retain the translational reading frame and enable the muscle cells to produce altered dystrophin products. This theory is supported by immunoblotting studies, which show that DMD patients lack dystrophin in their muscle cells or that dystrophin is present at very low levels, whereas BMD patients produce a protein with reduced abundance or abnormal size. Here we describe a deletion of the dystrophin gene in a family segregating for very mild BMD, one member of which was still ambulant at age 61 years, which removes a central part of the dystrophin gene encompassing 5,106 base pairs of coding sequence, almost half the coding information. Immunological analysis of muscle from one of the patients demonstrates that this mutation results in the production of a truncated polypeptide localized correctly in the muscle cell. These results are particularly significant in the context of gene therapy which, if it is ever envisaged, would be facilitated by the replacement of the very large dystrophin gene with a more manipulatable mini-gene construct.
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PMID:Very mild muscular dystrophy associated with the deletion of 46% of dystrophin. 240 10

Duchenne muscular dystrophy (DMD) is a human X-linked biochemical defect resulting in the progressive wasting of skeletal muscle of affected individuals. It is the most common and is considered to be the most devastating of the muscular dystrophies, affecting about 1 in 3,500 live-born males. The gene that, when defective, results in this disorder was recently isolated. Using the cloned complementary DNA sequences corresponding to the DMD gene, antibodies have been produced that react with a protein species of relative molecular mass (Mr) approximately 400,000 (400K) which was absent in two DMD-affected individuals and in mdx mice. This protein species is called dystrophin because of its identification by molecular-genetic analysis of affected individuals. Here we show that dystrophin is associated with the triadic junctions in skeletal muscle, and is therefore probably involved with Ca2+ homoeostasis. We also show that the approximately 450K ryanodine receptor/sarcoplasmic reticulum Ca2+ channel, which has the large size and subcellular distribution characteristics of dystrophin, is an immunologically distinct protein species.
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PMID:Subcellular fractionation of dystrophin to the triads of skeletal muscle. 244 3

Lymphocytic beta-adrenoceptor levels, receptor binding affinity, lymphocytic basal and isoproterenol-stimulated cyclic AMP (cAMP) production and plasma catecholamine levels were studied in 49 patients with neuromuscular diseases and in 10 healthy subjects. Patients with X-linked muscular dystrophy (Duchenne, 13 patients; Becker, 4 patients) showed a significant reduction in lymphocytic beta-adrenoceptor densities (35.9 +/- 2.2 fmol/mg protein vs. 49.6 +/- 3.6 fmol/mg, controls; P less than 0.02), whereas the receptor levels for the patients with spinal muscular atrophy (15), polymyositis (10) and for Duchenne carriers (7) did not differ significantly from the corresponding levels for the control subjects. The reduction in the beta-adrenoceptor density was not correlated with the physical disability of the patients. Lymphocytic beta-adrenoceptor affinity (KD) and basal and isoproterenol-stimulated cAMP levels were all comparable to control subjects' values. Catecholamine levels showed mild inconsistent elevations in various patient groups. The results suggest that reduction in cellular beta-adrenoceptors is characteristic of X-linked muscular dystrophies. Its relationship to the basic gene defect is unknown.
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PMID:Lymphocytic beta-adrenergic receptors in X-linked muscular dystrophy. 255 75

Using the data from daughters of known carriers and from age-paired controls, we present a method for estimating the mean and variance of creatine kinase (CK) and pyruvate kinase (PK) in pre-menarchal and early adolescent Duchenne muscular dystrophy (DMD) carriers. CK and PK means and variances were estimated for different age ranges; it is shown that among DMD carriers the levels of both enzymes decrease linearly with age. A discriminant analysis was further performed for the estimation of biochemical risks favouring the diagnosis of heterozygosity for possible young carriers. The use of this method may also be applicable for other X-linked conditions in which the detection of heterozygotes is probabilistic.
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PMID:Estimates of conditional heterozygosity risks for young females in Duchenne muscular dystrophy. 258 32

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are two allelic forms of an X-linked muscle disorder exhibiting phenotypic heterogeneity. We studied 49 individuals clinically diagnosed as having classic DMD, female DMD, mild DMD "outliers," and BMD. The patients' DNA was analyzed and alterations detected were correlated with particular phenotypes. We found that 14 of 32 classic DMD patients have an internal deletion in the same, relatively small, region of the gene; therefore this region may undergo deletions at a higher rate than the remainder of the gene. We could detect no alterations in the DNA in the remaining 18 patients. Selected patients from both groups failed to show muscle dystrophin. Seven of 11 patients with a mild DMD or BMD phenotype showed deletions at the 5' end of the gene. The other 4 patients failed to show deletions. Three of the patients with both a mild phenotype and a deletion at the 5' end had normal or low amounts of a dystrophin of smaller molecular weight. Patients with classic DMD who had a detectable deletion had a milder clinical course than those without. Contrary to a previous report, no patient in the population of clinically precisely defined DMD boys showed a deletion at the 5' end; thus, the outlier and BMD patients may be genetically different from boys with classic DMD. This correlation may be of diagnostic and prognostic significance.
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PMID:Genetic abnormalities in Duchenne and Becker dystrophies: clinical correlations. 264 85

Clonal myogenic cell cultures were established from a potential heterozygote for a mutant Duchenne muscular dystrophy (DMD) gene who was also heterozygous for isozymes of the X-linked enzyme glucose-6-phosphate dehydrogenase. Previous tissue culture studies of this muscle donor demonstrated equal proliferative capacity of myoblasts that had lyonized either the paternal or maternal X-chromosome, indicating that mutation of the DMD gene does not affect growth of myoblasts. If this muscle donor were a gonadal mosaic, this conclusion would be incorrect. In the present study, only those myogenic colonies expressing the glucose-6-phosphate dehydrogenase-A isozyme were found to express dystrophin, indicating that this woman was indeed a heterozygote for DMD. By documenting dystrophin deficiency in a specific population of myogenic cells from this woman, we verify our previous conclusion regarding the normal proliferative capacity of DMD myoblasts. Somatic cell testing of dystrophin expression may offer an alternative to established genetic carrier tests for those women in whom deletions of the DMD are not detectable, whose pedigree structure does not permit linkage analysis, or in whom standard phenotypic analyses are ambiguous.
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PMID:Dystrophin analysis in clonal myoblasts derived from a Duchenne muscular dystrophy carrier. 265 63

The aim of the present report was to estimate the proportion of autosomal recessive (AR) inheritance among families with affected males diagnosed as Duchenne muscular dystrophy (DMD) in which X-linked inheritance could not be confirmed. A total of 470 families was studied: 20 with at least one affected girl with "Duchenne-like" phenotype and 450 with only affected boys. Based on the number of families with at least one affected girl and the number of patients per sibship among these pedigrees, the proportion of families with DMD inherited as an AR trait was estimated at 6.8%. It is also estimated that 2.5-4% of male isolated patients diagnosed as DMD may have the AR form, which could be one possible explanation for the inconsistent results between clinical diagnosis and dystrophin assessment in one case recently reported.
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PMID:Estimate of the proportion of Duchenne muscular dystrophy with autosomal recessive inheritance. 265 92

X-linked DMD is a serious condition characterized by progressive muscle wasting and weakness and death ensues in the late teens or early twenties. There is considerable clinical variability even within families and some suggestions of genetic heterogeneity. Though skeletal muscle is primarily involved, other tissues are also affected including cardiac and smooth muscle. Other abnormalities include mental retardation, thymus hyperplasia and possibly certain endocrinological changes. The responsible locus is at Xp21 and the gene product is a very large protein (dystrophin) which is normally localised to muscle cell membranes. It is hypothesised that its absence in DMD may result in instability of the muscle cell membrane with resultant ingress of calcium, an increase in intracellular calcium, and cell death. An understanding of this pathway is important in devising an effective treatment.
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PMID:Clinical and molecular studies in Duchenne muscular dystrophy. 266 10


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