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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dystrophin constitutes approximately 5% of the cytoskeletal protein of skeletal muscle sarcolemma, suggesting that dystrophin could play a major structural role in skeletal muscle. We have presented evidence for the existence of a large oligomeric complex containing dystrophin, a 59 kDa triplet, a 25 kDa protein and four sarcolemmal glycoproteins with apparent M(r) of 156 kDa, 50 kDa, 43 kDa and 35 kDa. All components of the dystrophin-glycoprotein complex were localized to the skeletal muscle sarcolemma. Dystrophin, the 156 kDa and 59 kDa dystrophin-associated protein were found to be peripheral membrane proteins while the 50 kDa, 43 kDa, 35 kDa and 25 kDa dystrophin-associated proteins were confirmed as integral membrane proteins. The primary sequences of the 43 kDa and 156 kDa dystrophin-associated glycoproteins have been established by recombinant DNA techniques. Both the 43 and 156 kDa dystrophin-associated glycoproteins are encoded by a single 5.8 kb mRNA which is expressed in a variety of tissues in addition to skeletal muscle. The 156 kDa dystrophin-associated glycoprotein binds laminin, a well characterized component of the extracellular matrix. Finally, the dystrophin-glycoprotein complex is specifically and greatly reduced in Duchenne-afflicted and mdx mouse skeletal muscle, suggesting that the loss of dystrophin-associated proteins is due to the absence of dystrophin and not due to secondary effects of muscle fibre degradation. Taken together, these data support the hypothesis that the absence of dystrophin leads to a loss of the linkage between the subsarcolemmal cytoskeleton and extracellular matrix and that this may initiate muscle fibre necrosis.
Mol Cell Biol Hum Dis Ser 1993
PMID:Dystrophin-associated glycoproteins: their possible roles in the pathogenesis of Duchenne muscular dystrophy. 811 38

PCR amplification has enabled a variety of studies to be performed on the murine dystrophin transcripts. Figure 7.12 displays a summary of the features of the murine dystrophin mRNA that have been described in this article. The location of the mutation in the original mdx mouse is indicated, as are the different spliced forms of the dystrophin transcript. Also shown are the location of various PCR primer binding sites that were used to deduce the alternative splicing pattern of the gene. It is likely that conventional cloning efforts aimed at identifying the variety of dystrophin spliced forms would have taken years to perform, particularly since several of the isoforms are expressed at levels significantly below the estimated 0.02% of total mRNA that dystrophin represents in skeletal muscle (Hoffman et al., 1987a, b). Amplification of dystrophin mRNA simplifies scanning methods for the identification of DNA sequence variations. Attempts to re-isolate and sequence the 14 kb cDNA to determine the mutation in separate strains of mdx mice are not likely to be time or cost effective. PCR enables these types of questions to be answered in a relatively short period of time, and similar types of analyses can be applied to human DMD tissues. Knowledge of the transcript diversity displayed by the dystrophin gene will enable the role of these separate isoforms to be addressed. Despite considerable effort by a variety of laboratories over the last five years, the precise functional role played by dystrophin remains unclear, and it can only be assumed that the separate isoforms act to modulate the functional role of dystrophin in separate tissues or in response to differing physiological states. PCR amplification of the dystrophin isoforms has enabled the variable regions of the transcript to be subcloned (Bies et al., 1992). These clones have been used to reintroduce the variable regions into full-length mini-gene expression vectors, which are currently being tested for functional activity through the generation of transgenic mdx mice. The transgenic mice can be easily identified through the PCR-ASO assays described in this article, and the reverse transcriptase PCR assays will enable a detailed analysis of the expression pattern of the introduced mini-genes. It is hoped that such analyses will further attempts to determine the feasibility of using gene therapy as a treatment for DMD/BMD.
Mol Cell Biol Hum Dis Ser 1993
PMID:PCR analysis of muscular dystrophy in mdx mice. 811 39

Dystrophin is a high molecular weight protein present at low abundance in skeletal, cardiac and smooth muscle and in trace amounts in brain. In skeletal muscle, dystrophin is uniformly distributed along the inner surface of the plasma membrane. Biochemical fractionation studies have shown that all detectable skeletal muscle dystrophin is tightly associated with a complex of wheat germ agglutinin (WGA)-binding and concanavalin A (Con A) binding sarcolemmal glycoproteins. Absence of dystrophin is the primary biochemical defect in patients with Duchenne muscular dystrophy and leads to segmental necrosis of their skeletal myofibers. Although present in similar amounts in normal cardiac and skeletal muscle, the absence of dystrophin from cardiac muscle has less severe effects on the survival of cardiac cells. We have therefore examined whether there are differences in the properties of cardiac and skeletal dystrophin. We report that in contrast to skeletal muscle, cardiac dystrophin is distributed between distinct pools: a soluble cytoplasmic pool, a membrane-bound pool not associated with WGA-binding glycoproteins and a membrane-bound pool associated with WGA-binding glycoproteins. Cardiac dystrophin was not associated with any Con A binding glycoproteins. Immunohistochemical localization studies in isolated ventricular myocytes reveal a distinct punctate staining pattern for dystrophin, approximating to the level of the transverse tubule/Z-line and contrasting with the uniform sarcolemmal staining reported for skeletal muscle fibers. The distinct properties of cardiac dystrophin suggest unique roles for this protein in cardiac versus skeletal muscle function.
Mol Cell Biochem 1994 Jan 12
PMID:Dystrophin predominantly localizes to the transverse tubule/Z-line regions of single ventricular myocytes and exhibits distinct associations with the membrane. 819 Jan 21

Duchenne and mdx muscle tissues lack dystrophin where it normally interacts with glycoproteins in the sarcolemma. Intracellular free calcium ([Ca2+]i) is elevated in Duchenne and mdx myotubes and is correlated with abnormally active calcium-specific leak channels in dystrophic myotubes. We fused Duchenne human and normal mouse myoblasts and identified heterokaryon myotubes by Hoechst 33342 staining to measure the degree to which dystrophin introduced by normal nuclei could incorporate throughout the myotube at the sarcolemma and restore normal calcium homeostasis. Dystrophin expression in myotubes was determined by immunofluorescence and confocal laser scanning microscopy. Dystrophin was expressed at the sarcolemma in normal mouse and heterokaryon myotubes, but not in Duchenne myotubes. In heterokaryons, extensive dystrophin localization occurred at the sarcolemma even where only Duchenne nuclei were present, indicating that dystrophin does not exhibit nuclear domains. Heterokaryon, normal mouse and Duchenne myotube [Ca2+]i was measured using fura-2 and fluorescence ratio imaging. Heterokaryon and normal mouse myotubes were found to maintain similar levels of [Ca2+]i. In contrast, Duchenne myotubes had significantly higher [Ca2+]i (p < 0.001). Furthermore, the ability of heterokaryons to maintain normal [Ca2+]i did not depend on greater numbers of normal nuclei than Duchenne being present in the myotube. These results support the view that dystrophin expression in heterokaryons allows for efficient control of [Ca2+]i.
Mol Biol Cell 1993 Sep
PMID:Heterokaryon myotubes with normal mouse and Duchenne nuclei exhibit sarcolemmal dystrophin staining and efficient intracellular free calcium control. 825 98

Dystroglycan is a novel laminin binding component of the dystrophin-glycoprotein complex which provides a linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. Here we report the cDNA and genomic structure of human dystroglycan. The human dystroglycan is encoded by a single gene (DAG1) mapped to chromosome 3 band p21. The coding sequence is organized into two exons, separated by a large intron. The predicted amino acid sequence of human and rabbit dystroglycan are 93% identical with predicted glycosylation sites being conserved. Human dystroglycan is expressed in a variety of fetal and adult tissues. Our data suggest that muscle and non-muscle isoforms of dystroglycan differ by carbohydrate moieties but not protein sequence. Therefore, we hypothesize that variable glycosylation of the conserved protein core might modulate laminin binding. The relationship of dystroglycan to human diseases is discussed.
Hum Mol Genet 1993 Oct
PMID:Human dystroglycan: skeletal muscle cDNA, genomic structure, origin of tissue specific isoforms and chromosomal localization. 826 18

Utrophin and dystrophin are highly homologous proteins which are reciprocally expressed in DMD (Duchenne muscular dystrophy) muscle. The remarkable similarity of these proteins suggests that they may play a similar cellular role in some circumstances; if this were the case then utrophin may be capable of replacing dystrophin in DMD patients. In this paper we show that the genomic structure of the utrophin gene is similar to the dystrophin gene, further exemplifying the relatedness of the two genes and their gene products. We have constructed a 1.25 Mb contig of eight yeast artificial chromosome (YAC) clones covering the utrophin gene located on chromosome 6q24. Utrophin is encoded by multiple small exons spanning approximately 900 kb. The distribution of exons within the genomic DNA has similarities to that of the dystrophin gene. In contrast to dystrophin, the utrophin gene has a long 5' untranslated region composed of two exons and a cluster of unmethylated, rare-cutting restriction enzyme sites at the 5' end of the gene. Similarities between the genomic structure suggest that utrophin and dystrophin arose through an ancient duplication event involving a large region of genomic DNA.
Hum Mol Genet 1993 Nov
PMID:The utrophin and dystrophin genes share similarities in genomic structure. 828 Nov 35

Duchenne and Becker muscular dystrophies (DMD/BMD) are caused by mutations in the human dystrophin gene. About two-thirds of DMD/BMD patients exhibit gross rearrangements in the gene whereas the mutations in the remaining one third are thought to be point mutations or minor structural lesions. By means of various progressive PCR-based techniques hitherto a number of point mutations has been described that in most cases should cause premature translational termination. These data indicate a particular functional importance for the C-terminal region of dystrophin and consequently for its gene products Dp 71 and Dp 116. To screen for microheterogeneities in this gene region we applied PCR-SSCP analysis to exons 60-79 of twenty-six DMD/BMD patients without detectable deletions. The study identified seven point mutations and one intron polymorphism. Six point mutations, found in DMD patients, should cause premature translational termination. One point mutation, identified in a BMD patient, results in an amino acid exchange. Five of the DMD patients bearing a point mutation are mentally retarded suggesting that a disruption of the translational reading frame in the C-terminal region is associated with this clinical finding in DMD cases. Therefore our data raise the possibility, that Dp 71 and/or Dp 116, the C-terminal translational products of dystrophin, may be causally involved in cases of mental retardation that are associated with DMD.
Hum Mol Genet 1993 Nov
PMID:Point mutations at the carboxy terminus of the human dystrophin gene: implications for an association with mental retardation in DMD patients. 828 Nov 50

The 70.8 kDa protein product of the distal part of the giant Duchenne muscular dystrophy (DMD) gene, Dp71, is expressed in many cell types and tissues. Anchored PCR, primer extension and functional analysis of transfected constructs were used to determine the 5' end of the mRNA and characterize the promoter of this major DMD gene product. The 5' untranslated region (5'UTR) of Dp71 is transcribed from a single exon; the promoter does not contain a TATA box, and has a very high GC content and several potential Sp1 binding sites. It is located more than 2000 kb 3' to the muscle and brain type dystrophin promoters and only 150 kb from the 3' end of the gene, suggesting that in most DMD patients the expression of Dp71 is unaffected.
Hum Mol Genet 1993 Nov
PMID:A housekeeping type promoter, located in the 3' region of the Duchenne muscular dystrophy gene, controls the expression of Dp71, a major product of the gene. 828 Nov 51

The presumptive rod domain of dystrophin contains a series of degenerate repeating sequences with homology to those of spectrin. To determine the relation of the implied structural repeating units to the sequence repeat (the phasing), recombinant fragments of the domain of dystrophin were prepared by expression in Escherichia coli. The phasing was established by identifying the minimum sequence element that would form a stable fold of high (approx. 75%) alpha-helicity: by contrast, incorrectly phased fragments had labile structure with an average alpha-helicity of about 40%. The isolated folded structural repeat showed high stability towards proteolysis and a urea-denaturation profile with a plateau at low denaturant concentration, indicative of a unique folded conformation. The phasing is consistent with a structure inferred from analysis of the amino acid sequence and also found in spectrin, in which each structural repeat comprises a three-stranded coiled-coil, made up of one short helix (approx. 30 residues) and the N and C-terminal halves of two separate long helices, such that each long helix participates in the formation of two contiguous structural units.
J Mol Biol 1994 Jan 28
PMID:conformation and phasing of dystrophin structural repeats. 830 89

At the cellular level, the primary pathology in Duchenne muscular dystrophy (DMD) is caused by deficiency of the sarcolemmal-associated protein, dystrophin, in the striated musculature. Here we describe the somatic transfer and long-term expression of a human dystrophin minigene corresponding to a mild Becker muscular dystrophy (BMD) phenotype in skeletal muscle tissues of the dystrophin-deficient mdx mouse by direct retroviral transduction. Following a single intramuscular injection of recombinant retrovirus, sarcolemmal expression of dystrophin was observed in an average of approximately 6% of myofibres in treated tibialis anterior muscles and was associated with activated reappearance of at least one component (43kD) of the dystrophin-glycoprotein membrane complex (DGC). Furthermore, expression of recombinant dystrophin was observed in muscle tissues up to 9 months after treatment and a significant enhancement of retrovirus-mediated myofibre transduction was obtained in mdx muscle undergoing experimentally-induced regeneration. The results clearly demonstrate that retroviral transduction of activated satellite cells in regenerating skeletal muscle is a feasible route for direct and stable dystrophin gene transfer into muscle tissues in vivo.
Hum Mol Genet 1993 Jun
PMID:Direct retroviral-mediated transfer of a dystrophin minigene into mdx mouse muscle in vivo. 835 91


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