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At least 19 recordsLinked to original sources
PubMed1994

Molecular organization at the glycoprotein-complex-binding site of dystrophin. Three dystrophin-associated proteins bind directly to the carboxy-terminal portion of dystrophin.

Direct interaction between the C-terminal portion of dystrophin and dystrophin-associated proteins was investigated. The binding of dystrophin to each protein was reconstituted by overlaying bacterially expressed dystrophin fusion proteins onto the blot membranes to which dystrophin-associated proteins were transferred after separation by SDS/PAGE with the following results. (a) Among the components of the glycoprotein complex which links dystrophin to the sarcolemma, a 43-kDa dystrophin-associated glycoprotein binds directly to dystrophin. Although at least one of the binding sites of this protein resides within the cysteine-rich domain of dystrophin, a contribution of additional amino acid residues within the first half of the C-terminal domain was also suggested for more secure binding. (b) Two other proteins also directly bind to dystrophin. Their binding sites are suggested to reside within the last half of the C-terminal domain which is alternatively spliced depending on the tissue type. Previously, based on the enzyme digestion experiments, we showed that the binding site for the glycoprotein complex on dystrophin is present within the cysteine-rich domain and the first half of the C-terminal domain [Suzuki, A., Yoshida, M., Yamamoto, H. & Ozawa, E. (1992) FEBS Lett. 308, 154-160]. Here, we have extended this work and found that the region which is involved in interaction with the complex is widely extended to the entire length of this part of the molecule. On the basis of the present results, we propose a model of molecular architecture at the binding site for the complex on dystrophin.

Antibodies↗
PubMed1995

Sarcolemmal expression of dystrophin C-terminus but reduced expression of 6q-dystrophin-related protein in two DMD patients with large deletions of the dystrophin gene.

Partial deletions of the dystrophin gene are the predominant genetic lesions in Duchenne (DMD) and Becker (BMD) muscular dystrophies. According to the reading frame hypothesis [1], any deletion disrupting the translational reading frame of the mRNA cannot result in expression of the dystrophin molecule and should lead to severe phenotypes of DMD. In contrast, deletions which maintain the reading frame across the deleted exons may give rise to truncated, semifunctional proteins and milder courses of the disease (i.e. BMD). Among the notable exceptions of this hypothesis are very large "in-frame" deletions by which functionally indispensable domains of the dystrophin molecule have been removed. Here, we report on two DMD patients with large intragenic in-frame deletions. Grossly truncated, but stable dystrophin molecules with preserved C-terminal domains were detected at the sarcolemma on cryosections in both patients. However, dystrophin organization on single-teased muscle fibers revealed disarrangement of the costameric pattern, if compared to normal skeletal muscle fibers. Compared to dystrophin-deficient DMD muscle, expression of chromosome-6-encoded dystrophin-related protein (DRP) was greatly diminished in skeletal muscle of both patients. We show, that loss of more than 50% of dystrophin seems to be deleterious for the protein's function and therefore, the extent of the deletions may have an impact on construction of dystrophin mini genes. Moreover, these findings shed new light on the functional significance of the C-terminal domain of dystrophin. They also suggest a negative correlation between sarcolemmal expression of the dystrophin C-terminus and DRP expression at the sarcolemma.

Blotting, Western↗
PubMedDate not supplied

Dystrophin and dystrophin-related protein (utrophin) distribution in normal and dystrophin-deficient skeletal muscles.

The respective localizations of dystrophin and dystrophin-related protein (DRP or utrophin) along the sarcolemmal membrane and at the neuromuscular junctions (NMJs) in normal and dystrophin-deficient skeletal muscles, were determined using confocal laser microscopy. The analysis was prompted by the recent availability of a new anti-utrophin mAb [Bewick et al. NeuroReport 1992; 3:857-860] and different mAbs that react with dystrphin or both dystrophin and utrophin. In dystrophin-deficient muscles, utrophin was expressed and detectable over large subcellular areas normally occupied by dystrophin along the sarcolemmal membranes and at the NMJs. Utrophin was expressed in a non-uniform, discontinuous way on the sarcolemmal membrane in dystrophin-deficient skeletal muscles, similar to dystrophin in normal muscle fibres. The respective distributions of both related muscle proteins and their positions relative to the alpha-bungarotoxin acetylcholine (ACh) receptor marker were determined. Double-staining experiments and superimposition of the confocal images showed that utrophin was more closely associated with ACh receptors than dystrophin at the NMJs in normal muscles. Utrophin distribution consequently differed from that of dystrophin.

Adolescent↗
PubMed1995

A severe muscular dystrophy patient with an internally deleted very short (110 kD) dystrophin: presence of the binding site for dystrophin-associated glycoprotein (DAG) may not be enough for physiological function of dystrophin.

We report a 4-yr and 5-month-old boy with severe clinical features of an early-onset Duchenne muscular dystrophy, who had a very short (110 kDa) dystrophin at the sarcolemma. The patient had a large deletion (exons 2-44) of the dystrophin gene which was predicted to cause a reading frame shift. Sequence analysis of dystrophin mRNA in muscle revealed an alternatively spliced gene product from exons 1 to 51 that caused restoration of the reading frame, in addition to an mRNA corresponding to the DNA deletion. A consistent result was obtained by immunocytochemical analysis of muscle; i.e. positive staining for dystrophin at the sarcolemma using antibodies against the C-terminus, cysteine-rich region and last three of 24 repeat units of the central rod-domain, but not for the remaining antibodies for dystrophin that recognize the N-terminal and proximal rod-domains. Immunostaining for dystrophin-associated glycoproteins (DAGs: 43 and 50 K) and merosin were preserved. Utrophin staining was positive but fainter than other DMD muscles. These results suggest that an extremely short dystrophin lacking the entire actin-binding site in the N-terminus cannot function properly even if the protein possesses the putative DAG-binding cysteine-rich and the C-terminal domains, and still has an ability to associate with sarcolemmal membrane.

Base Sequence↗
PubMed1998

A dystrophin missense mutation showing persistence of dystrophin and dystrophin-associated proteins yet a severe phenotype.

A muscle biopsy from an X-linked muscular dystrophy pedigree showed normal dystrophin and dystrophin-associated proteins. Linkage to multiple markers within the dystrophin gene (LOD=2.7, theta=0) indicated a primary dystrophinopathy. Sequencing of the entire dystrophin RNA revealed a single missense mutation (D3335H) in the unique carboxyl-terminal domain. This is the first report showing that a relatively severe dystrophinopathy can occur despite the correct localization of dystrophin and dystrophin-associated proteins.

Amino Acid Sequence↗
PubMed1994

Apo-dystrophin-1 and apo-dystrophin-2, products of the Duchenne muscular dystrophy locus: expression during mouse embryogenesis and in cultured cell lines.

Two promoters in the distal half of the Duchenne Muscular Dystrophy gene drive transcription of mRNAs which have novel first exons and encode the shortened forms of dystrophin, apo-dystrophin-1 (Dp71) and apo-dystrophin-2 (Dp116). Apo-dystrophin-1 has a G + C rich promoter and is expressed in a wide range of cell types, whilst apo-dystrophin-2 is confined to peripheral nerve and brain. We have isolated and sequenced the unique 5' exon of rat apo-dystrophin-2 mRNA. Conceptual translation of this sequence indicates that apo-dystrophin-2 contains a unique 23 amino acid terminal peptide. Using specific probes derived from sequences at the 5' ends of apo-dystrophin-1 and apo-dystrophin-2 we have determined the expression of these two mRNAs during mouse embryonic development by RNA in situ hybridization. In contrast to full-length dystrophin, neither of these short dystrophin transcripts appear before organogenesis is well established. Apo-dystrophin-1 mRNA is detected in midline cells of the ventral neural tube and later, in the ependymal cells lining the ventricles of the brain. These results suggest that apo-dystrophin-1 mRNA is associated with glial cells in the CNS. Apo-dystrophin-1 transcripts are also abundant in the teeth primordia throughout their development. In contrast apo-dystrophin-2 mRNA is largely undetectable during development, although transcripts are seen in the newborn brain. Western blots of late human fetal tissue extracts confirm that apo-dystrophin-2 is most abundant in brain and analysis of RNA and protein in cultured cell lines reveal expression of apo-dystrophin-1 and apo-dystrophin-2 in glioma cells.

Animals↗
PubMed1995

Genetic and biochemical normalization in female carriers of Duchenne muscular dystrophy: evidence for failure of dystrophin production in dystrophin-competent myonuclei.

We studied 19 symptomatic female carriers of the Duchenne muscular dystrophy (DMD) gene. Most of these dystrophinopathy patients had had an erroneous or ambiguous diagnosis prior to dystrophin immunofluorescence testing. We assessed clinical severity by a standardized protocol, measured X-chromosome inactivation patterns in blood and muscle DNA, and quantitated the dystrophin protein content of muscle. We found that patients could be separated into two groups: those showing equal numbers of normal and mutant dystrophin genes in peripheral blood DNA ("random" X-inactivation), and those showing preferential use of the mutant dystrophin gene ("skewed" X-inactivation). In the random X-inactivation carriers, the clinical phenotype ranged from asymptomatic to mild disability, the dystrophin content of muscle was > 60% of normal, and there were only minor histopathologic changes. In the skewed X-inactivation patients, clinical manifestations ranged from mild to severe, but the patients with mild disease were young (5 to 10 years old). The low levels of dystrophin (< 30% on average) and the severe symptoms of the older patients suggested a poor prognosis for those with skewed X-inactivation, and they all showed morphologic changes of dystrophy. The random inactivation patients showed evidence of biochemical "normalization," with higher dystrophin content in muscle than predicted by the number of normal dystrophin genes. Seventy-nine percent of skewed X-inactivation patients (11/14) showed genetic "normalization," with proportionally more dystrophin-positive nuclei in muscle than in blood. In 65% of the skewed X-inactivation patients, dystrophin was not produced by dystrophin-positive nuclei; an average of 20% of myofiber nuclei were genetically dystrophin-positive but did not produce stable dystrophin. Biochemical normalization seems to be the main mechanism for rescue of fibers from dystrophin deficiency in the random X-inactivation patients. In the skewed X-inactivation patients, genetic normalization is active, but production failure of dystrophin by dystrophin-normal nuclei may counteract any effect of biochemical normalization. In the skewed X-inactivation patients, the remodeling of the muscle through cycles of degeneration and regeneration led to threefold increase in the number of dystrophin-competent nuclei in muscle myofibers (3.3 +/- 4.6), while dystrophin content was on the average 1.5-fold less then expected (-1.54 +/- 3.38). Our results permit more accurate prognistic assessment of isolated female dystrophinopathy patients and provide important data with which to estimate the potential effect of gene delivery (gene therapy) in DMD.

Adult↗
PubMed1996

Dystrophin-associated protein abnormalities in dystrophin-deficient muscle fibers from symptomatic and asymptomatic Duchenne/Becker muscular dystrophy carriers.

The absence of dystrophin in muscle fibers is associated with a major reduction in dystrophin-associated proteins (DAPs) and disruption of the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. We investigated the expression of the DAPs beta-dystroglycan, alpha-sarcoglycan, gamma-sarcoglycan and syntrophin as well as utrophin in the muscles of 13 Duchenne muscular dystrophy (DMD) carriers (with variable percentages of dystrophin-deficient fibers and with a range of clinical symptoms), 2 Becker muscular dystrophy (BMD) carriers (expressing a highly truncated protein in some fibers), 2 girls with a DMD-like phenotype, and 11 BMD carriers with almost normal dystrophin expression (reduced or patchy distribution in a few fibers only and rare dystrophin-deficient fibers). DAPs were highly reduced in all fibers lacking dystrophin in the DMD carriers, but were almost normal in the dystrophin-deficient fibers of the 2 BMD carriers with highly truncated dystrophin. In the 11 BMD carriers with nearly normal dystrophin, the few fibers with reduced or patchy dystrophin immunostaining also showed reduced DAP expression in correlation with dystrophin expression. Immunoblot for beta-dystroglycan and alpha-sarcoglycan confirmed the immunohistochemical findings. Utrophin expression was slightly increased in a proportion of fibers in the DMD and BMD carriers with dystrophin mosaicism. We found no correlation between utrophin expression and DAP expression. We conclude that absence or reduction of dystrophin in muscle fibers of DMD and BMD carriers causes a reduction of DAPs in the same fibers, as observed in DMD and BMD patients, while utrophin does not seem to play a role in DAP expression in adult muscle.

Adolescent↗
PubMed2001

Dynamic restoration of dystrophin to dystrophin-deficient myotubes.

Dystrophin domains are observed in myoblast transplantation experiments and in muscle fibers after somatic reversion in human Duchenne and mdx mouse muscular dystrophy. However, the formation and evolution of dystrophin-positive domains are not well established. Using a muscle satellite cell coculture system, we examined the dynamic restoration of dystrophin expression in dystrophin-deficient myotubes. The dystrophin-positive domains around source nuclei were clearly identified in hybrid myotubes. The occurrence of dystrophin domains was higher in myotubes differentiated from cocultures with a low concentration of normal wild-type satellite cells in relation to dystrophin-deficient satellite cells. At higher seeding ratios, the domain feature of dystrophin expression was more transitory and decreased as myotubes differentiated over time in culture. The average domain size initially increased with the addition of new nuclei by fusion early after differentiation of cocultures. However, separating dystrophin-positive domains according to their number of dystrophin-expressing contributory nuclei showed that diffusion of dystrophin contributed to domain elongation, even in early myotubes and later without fusion of additional nuclei. Diffusion occurred for all domains of one to six wild-type nuclei, and the diffusion rate was higher in domains with larger numbers of nuclei. This dynamic domain feature of dystrophin expression was also related to restoring the organization of dystrophin-associated proteins and acetylcholine receptors to hybrid myotubes. Factors regulating domain formation and diffusion therefore are important considerations in the design of strategies for both myoblast transplantation and gene therapy of Duchenne muscular dystrophy.

Animals↗
PubMed2006

Mini-dystrophin efficiently incorporates into the dystrophin protein complex in living cells.

Dystrophin is a critical muscle cell structural protein which when deficient results in Duchenne muscular dystrophy. Recently miniature versions of the dystrophin gene have been constructed that ameliorate the pathology in mouse models. To characterize mini-dystrophin's incorporation into the dystrophin protein complex in living cells, two fusion proteins were constructed where mini-dystrophin is fused to the N- or C-terminus of an enhanced green fluorescent protein reporter gene. Both fusion proteins correctly localize at the plasma membrane in vitro and in vivo. Live cell microscopy establishes that mini-dystrophin translocates directly to the PM of differentiating muscle cells, within 4 h of expression. Latrunculin A treatment, actin and beta-dystroglycan binding domain deletion constructs, and co-immunoprecipitation assays demonstrate that mini-dystrophin is firmly anchored to the sarcolemma primarily through its connections to beta-dystroglycan, mimicking effects seen with wild type dystrophin. Furthermore, point mutations made within the putative beta-dystroglycan anchoring ZZ domain of mini-dystrophin result in an ablation of beta-dystroglycan binding and a nuclear translocation of the protein. These results demonstrate that mini-dystrophin is efficiently bound and incorporated into the dystrophin protein complex, via beta-dystroglycan in living cells, similarly to the full length dystrophin protein.

Actins↗
PubMed1992

Localization of dystrophin and dystrophin-related protein at the electromotor synapse and neuromuscular junction in Torpedo marmorata.

The immunological identification of dystrophin isoforms at the neuromuscular junction and Torpedo marmorata electromotor synapse was attempted using various antibodies. A polyclonal antibody raised against electrophoretically purified dystrophin from T. marmorata electrocyte has been thoroughly investigated. This antibody recognized dystrophin in the electric tissue as well as sarcolemmal and synaptic neuromuscular junction dystrophin in all studies species (T. marmorata, rat, mice and human) at serum dilutions as high as 1:10,000. At variance, no staining of either the sarcolemma or neuromuscular junction was observed in Duchenne muscular dystrophy or mdx mice skeletal muscles. In these muscles, other members of the dystrophin superfamily, in particular the dystrophin-related protein(s) encoded by autosomal genes are present. These data thus demonstrate the specificity of our antibodies for dystrophin. Anti-dystrophin-related protein antibodies [Khurana et al. (1991) Neuromusc. Disorders 1, 185-194] which gave a strong immunostaining of the neuromuscular junction in various species, including T. marmorata, cross-reacted weakly with the postsynaptic membrane of the electrocyte. Taken together, these observations are in favor of the existence of a protein very homologous to dystrophin at the electromotor synapse in T. marmorata, whereas both dystrophin and dystrophin-related protein co-localize at the neuromuscular junction as in all species studied. The electrocyte thus offers the unique opportunity to study the interaction of dystrophin with components of the postsynaptic membrane.

Animals↗
PubMed2004

Long-term expression of full-length human dystrophin in transgenic mdx mice expressing internally deleted human dystrophins.

One of the possible therapies for Duchenne muscular dystrophy (DMD) is the introduction of a functional copy of the dystrophin gene into the patient. For this approach to be effective, therapeutic levels and long-term expression of the protein need to be achieved. However, immune responses to the newly expressed dystrophin have been predicted, particularly in DMD patients who express no dystrophin or only very truncated versions. In a previous study, we demonstrated a strong humoral and cytotoxic immune response to human dystrophin in the mdx mouse. However, the mdx mouse was tolerant to murine dystrophin, possibly due to the endogenous expression of dystrophin in revertant fibres or the other nonmuscle dystrophin isoforms. In the present study, we delivered human and murine dystrophin plasmids by electrotransfer after hyaluronidase pretreatment to increase gene transfer efficiencies. Tolerance to murine dystrophin was still seen with this improved gene delivery. Tolerance to exogenous recombinant full-length human dystrophin was seen in mdx transgenic lines expressing internally deleted versions of human dystrophin. These results suggest that the presence of revertant fibres may prevent the development of serious immune responses in patients undergoing dystrophin gene therapy.

Animals↗
PubMed1993

Deficiency of dystrophin-associated proteins in Duchenne muscular dystrophy patients lacking COOH-terminal domains of dystrophin.

Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene, is a cytoskeletal protein tightly associated with a large oligomeric complex of sarcolemmal glycoproteins including dystroglycan, which provides a linkage to the extracellular matrix component, laminin. In DMD, the absence of dystrophin leads to a drastic reduction in all of the dystrophin-associated proteins, causing the disruption of the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix which, in turn, may render muscle cells susceptible to necrosis. The COOH-terminal domains (cysteine-rich and carboxyl-terminal) of dystrophin have been suggested to interact with the sarcolemmal glycoprotein complex. However, truncated dystrophin lacking these domains was reported to be localized to the sarcolemma in four DMD patients recently. Here we report that all of the dystrophin-associated proteins are drastically reduced in the sarcolemma of three DMD patients in whom dystrophin lacking the COOH-terminal domains was properly localized to the sarcolemma. Our results indicate that the COOH-terminal domains of dystrophin are required for the proper interaction of dystrophin with the dystrophin-associated proteins and also support our hypothesis that the loss of the dystrophin-associated proteins in the sarcolemma leads to severe muscular dystrophy even when truncated dystrophin is present in the subsarcolemmal cytoskeleton.

Biopsy↗
PubMed1998

Dystrophin acts as a transplantation rejection antigen in dystrophin-deficient mice: implication for gene therapy.

Duchenne muscular dystrophy is a lethal and common X-linked recessive disease caused by a defect in dystrophin. Normal myoblast transplantation and dystrophin gene transfer have been expected to correct the deficiency in the muscles, but their clinical application has been hampered by the limited preservation of dystrophin-positive myofibers. In this study we investigated the mechanism for immunologic rejection of normal C57BL/10 (B10) myoblasts transplanted into dystrophin-deficient mdx mice, an animal model of Duchenne muscular dystrophy. We found that mdx mice develop CTL specific for dystrophin itself, which were CD8 dominant and restricted by H-2Kb. We identified several antigenic peptides derived from dystrophin that bind to H-2Kb and are recognized by the mdx anti-B10 CTL. Immunologic tolerance against dystrophin was successfully induced by i.v. injection of these peptides before B10 myoblast transplantation, which resulted in sustained preservation of dystrophin-expressing myofibers in mdx mice. These results demonstrate that dystrophin is antigenic in dystrophin-deficient mice and that immunologic regimen would be necessary to achieve the persistent expression of introduced dystrophin in the muscles of dystrophin-deficient individuals.

Amino Acid Sequence↗
PubMed1993

Restoration of dystrophin-associated proteins in skeletal muscle of mdx mice transgenic for dystrophin gene.

Duchenne muscular dystrophy (DMD) patients and mdx mice are characterized by the absence of dystrophin, a membrane cytoskeletal protein. Dystrophin is associated with a large oligomeric complex of sarcolemmal glycoproteins, including dystroglycan which provides a linkage to the extracellular matrix component, laminin. The finding that all of the dystrophin-associated proteins (DAPs) are drastically reduced in DMD and mdx skeletal muscle supports the primary function of dystrophin as an anchor of the sarcolemmal glycoprotein complex to the subsarcolemmal cytoskeleton. These findings indicate that the efficacy of dystrophin gene therapy will depend not only on replacing dystrophin but also on restoring all of the DAPs in the sarcolemma. Here we have investigated the status of the DAPs in the skeletal muscle of mdx mice transgenic for the dystrophin gene. Our results demonstrate that transfer of dystrophin gene restores all of the DAPs together with dystrophin, suggesting that dystrophin gene therapy should be effective in restoring the entire dystrophin-glycoprotein complex.

Animals↗
PubMed1993

Dystrophin and dystrophin-related protein expression in Torpedo marmorata electric organ.

The presence of different dystrophin-related protein forms was investigated in electric organ as compared to cardiac, white or red skeletal muscles from Torpedo marmorata. Two strategies were followed. First, we used specific C-terminal dystrophin and dystrophin-related protein monoclonal antibodies which we characterized in the present study. 400 kDa protein bands were detected in the tissues mentioned above with both specific types of antibodies. Second, we produced monoclonal antibodies raised against a dystrophin-enriched preparation from T. marmorata electric organ. Western blot and immunofluorescence analyses showed the tissue specificity of T. marmorata antibodies and allowed us to classify them as types I, II and III. Vessel walls and neuromuscular junctions were labeled with T. marmorata type II and III antibodies in human muscles (skeletal and smooth). Both approaches demonstrated that the T. marmorata electric organ contained different proteins related with dystrophin: a dystrophin form, a dystrophin-related protein form and a dystrophin-related protein isoform, homologous to the dystrophin-related protein present in muscle vessel walls and at the neuromuscular junctions of human tissues. The presence of dystrophin and dystrophin-related protein is finally discussed relative to their functions and organ specificities.

Animals↗
PubMed1989

Dystrophin diagnosis: comparison of dystrophin abnormalities by immunofluorescence and immunoblot analyses.

Immunoblot characterization and immunofluorescence localization of dystrophin are presented for 76 human patients with various neuromuscular diseases. Normal dystrophin (shown by immunoblotting) was invariably visualized as a continuous, peripheral membrane immunostaining of myofibers. Biochemical abnormalities of dystrophin (either lower or higher molecular weight dystrophin) resulted in patchy, discontinuous immunostaining, suggesting that the abnormal dystrophin proteins are not capable of creating a complete membrane cytoskeleton network. There was a very strong correlation of clinical diagnoses with the type of dystrophin abnormality; all Duchenne muscular dystrophy patient muscle contained no detectable dystrophin, Becker muscular dystrophy patient muscle had clearly abnormal dystrophin, and unrelated diseases showed normal dystrophin. However, a single patient of five carrying the diagnosis of Fukuyama dystrophy showed no detectable dystrophin and thus appeared to be a Duchenne dystrophy patient by the biochemical assays. We know of no other case of a patient with a disease thought to be unrelated to Duchenne/Becker dystrophy yet demonstrating dystrophin deficiency. Based on the data presented, we conclude that immunofluorescence is the best technique for the detection of female carriers of Duchenne dystrophy, whereas immunoblotting appears superior for the prognostic diagnosis of Becker muscular dystrophy.

Amino Acid Sequence↗
PubMed2004

The mouse dystrophin muscle enhancer-1 imparts skeletal muscle, but not cardiac muscle, expression onto the dystrophin Purkinje promoter in transgenic mice.

A subset of patients harboring mutations in the dystrophin gene suffer from X-linked dilated cardiomyopathy (XLCM), a familial heart disease that is not accompanied by any clinical signs of skeletal muscle myopathy. As the muscle (M) isoform of dystrophin is not expressed in these patients, the absence of skeletal muscle symptoms has been attributed to expression of the brain (B) and cerebellar Purkinje (CP) isoforms of dystrophin in skeletal, but not cardiac, muscles of XLCM patients. The compensatory mechanism of dystrophin B and CP promoter upregulation is not known but it has been suggested that the dystrophin muscle enhancer from intron 1, DME-1, may be important in this activity. Previous studies have shown that the presence of the DME-1 is essential for a significant increase in dystrophin B and CP promoter activity in skeletal muscle cells in culture. Here, we demonstrate that the mouse dystrophin CP promoter drives expression of a lacZ reporter gene specifically to the cerebellar Purkinje cell layer but not to skeletal or cardiac muscle of transgenic mice. However, if the mouse counterpart of DME-1 is present in the transgene construct, the dystrophin CP promoter is now activated in skeletal muscle, but not in cardiac muscle. Our findings provide in vivo evidence for the importance of the dystrophin muscle enhancer sequences in activating the dystrophin CP promoter in skeletal muscle. Furthermore, they provide support for the model in which muscle enhancers, like DME-1, activate the dystrophin B and CP promoters in skeletal muscle, but not in cardiac muscle, of XLCM patients.

Animals↗