Anti-dystrophin Antibodies Research Articles

Dystrophin analysis in the differential diagnosis of autosomal recessive muscular dystrophy of childhood and Duchenne muscular dystrophy

We report 2 patients with childhood autosomal recessive muscular dystrophy. Both patients had slight muscle weakness without enlargement of the calf muscles or involvement of the facial muscles. Their clinical courses are static. Muscle histology revealed characteristic features of muscular dystrophy. Dystrophin was identifiable in the sarcolemma of both patients by immunocytochemical staining with an antidystrophin antibody. At an early age, immunocytochemical analysis with antidystrophin antibody was useful in distinguishing between childhood autosomal recessive and Duchenne muscular dystrophies.

Mosaic pattern of dystrophins in Duchenne muscular dystrophy

Dystrophin is the gene product affected in Duchenne muscular dystrophy (DMD). Dystrophin is demonstrably absent with immunocytochemical staining and undetectable by western blotting of DMD muscles. We report an isolated 7-year-old girl with DMD. Analysis of the patient's and her mother's DNA, with probes covering the DMD gene, disclosed no deletion. We have studied dystrophin in biopsied muscle from the patient using antidystrophin antibody in combination with immunofluorescence. Random presence of normal and dystrophin-deficient fibers were indicative of mosaic expression. Dystrophin immunocytochemistry may be useful for accurate diagnosis of affected females.

Localization and characterization of dystrophin in muscle biopsy specimens from Duchenne muscular dystrophy and various neuromuscular disorders.

Dystrophin, surmised to be the causative protein of Duchenne muscular dystrophy (DMD), was studied for its intracellular localization and characterization by immunostaining and Western blotting using antidystrophin antibodies. In normal controls and in patients with various neuromuscular diseases other than DMD and Becker's muscular dystrophy (BMD), dystrophin was detected homogeneously on the entire surface membrane of the muscle fibers, whereas it was absent in DMD patients and partially observed in BMD cases. The density of dystrophin was low in BMD and female DMD patients. In mouse skeletal and cardiac muscles, too, dystrophin localized in the muscle surface membrane, and its presence in the brain was also suggested. However, dystrophin was not detected in mdx mice. These data suggest that myofiber necrosis in DMD patients and mdx mice is likely to be the result of plasma membrane instability.

Dystrophin immunocytochemistry in muscle culture: detection of a carrier of Duchenne muscular dystrophy.

Dystrophin is the gene product which is affected in Duchenne muscular dystrophy (DMD). We studied differentiating clonal muscle cultures derived from normal muscle and from the mother of a DMD patient by immunocytochemistry, using anti-dystrophin antibody. While clonal cultures derived from normal muscle expressed dystrophin in all myotubes, two populations of myogenic cells could be demonstrated in muscle from this possible DMD carrier; in 13 clones the myotubes expressed dystrophin and in 7 clones dystrophin was undetectable. No DNA deletion, duplication or rearrangement was detected by Southern blot analysis of DNA from this family using cDNA probes. Thus, immunocytochemical analysis of clonal muscle cultures may be a useful method to determine whether mothers of DMD patients are carriers of the DMD mutation, especially in the absence of demonstrable gene defects.

Immunohistochemical dystrophin reaction in synaptic regions

To investigate the functional significance of dystrophin, we studied various tissues of control and mdx mice, and rats immunohistochemically, using anti-dystrophin antibodies. In control animals, we observed the immunohistochemical localization of dystrophin in synaptic regions such as neuromuscular junctions, the cornea and outer plexiform layer of the retina, the taste buds and neurons in the brain, as well as on the surface membrane of skeletal, cardiac and smooth muscle fibers. In mdx mice, dystrophin was absent from the surface membrane of muscle fibers and the outer plexiform layer of the retina. These results suggest that dystrophin plays an important physiological and/or structural role in the conduction system.

Electrophoretic studies of muscle proteins in Duchenne muscular dystrophy and other neuromuscular disorders--with special reference to the change of dystrophin.

We studied total SDS-solubilized muscle proteins (TMP) of Duchenne muscular dystrophy (DMD) and other neuromuscular disorders, with special attention to the change of dystrophin suspected of being the product of DMD locus. SDS gel electrophoresis of DMD patients showed an absence of band 5 and an extreme faintness of band 2 with a decrease of band 4', 5', and 5''. Immunoblot analysis, using anti-dystrophin antibodies (anti-30 kd and anti-60 kd polyclonals), showed an absence of dystrophin in all 6 DMD cases. In other neuromuscular disorders, there was no change of TMP, and dystrophin was clearly detectable. To elucidate the degenerative mechanism of DMD muscle, further studies, including the problem of clarifying the physiological role of dystrophin, are necessary.

Evidence for the association of dystrophin with the transverse tubular system in skeletal muscle.

Polyclonal antibodies to dystrophin (the protein product of the human Duchenne muscular dystrophy gene) were used to identify and characterize dystrophin in isolated triads from rabbit skeletal muscle. Anti-dystrophin antibodies recognize an approximately 400,000-Da protein in isolated triads or heavy microsomes from skeletal muscle. Treatment of heavy microsomes with buffers containing high salt or EDTA to remove peripheral or extrinsic membrane proteins does not remove dystrophin; however, treatment of intact triads with trypsin shows that dystrophin is extremely sensitive to mild proteolytic digestion. Isolation of junctional complexes from skeletal muscle triads indicates that dystrophin is tightly associated with the triadic junction. Fractionation of the triadic junction into junctional transverse tubular membranes and junctional sarcoplasmic reticulum membranes has shown that dystrophin is enriched in junctional transverse tubular membranes. Thus, our results suggest that dystrophin is a component of the triad junction which is exposed to the cytoplasm and embedded in or attached to the transverse tubular membrane.