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Animal models for muscular dystrophy show different patterns of sarcolemmal disruption.

Straub V, Rafael JA, Chamberlain JS, Campbell KP - J. Cell Biol. (1997)

Bottom Line: However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue.One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage.Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.

View Article: PubMed Central - PubMed

Affiliation: Department of, Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.

ABSTRACT
Genetic defects in a number of components of the dystrophin-glycoprotein complex (DGC) lead to distinct forms of muscular dystrophy. However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue. One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage. Using tracer molecules, we compared sarcolemmal integrity in animal models for muscular dystrophy and in muscular dystrophy patient samples. Evans blue, a low molecular weight diazo dye, does not cross into skeletal muscle fibers in normal mice. In contrast, mdx mice, a dystrophin-deficient animal model for Duchenne muscular dystrophy, showed significant Evans blue accumulation in skeletal muscle fibers. We also studied Evans blue dispersion in transgenic mice bearing different dystrophin mutations, and we demonstrated that cytoskeletal and sarcolemmal attachment of dystrophin might be a necessary requirement to prevent serious fiber damage. The extent of dye incorporation in transgenic mice correlated with the phenotypic severity of similar dystrophin mutations in humans. We furthermore assessed Evans blue incorporation in skeletal muscle of the dystrophia muscularis (dy/dy) mouse and its milder allelic variant, the dy2J/dy2J mouse, animal models for congenital muscular dystrophy. Surprisingly, these mice, which have defects in the laminin alpha2-chain, an extracellular ligand of the DGC, showed little Evans blue accumulation in their skeletal muscles. Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.

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Immunohistochemical staining of 7-μm cryosection from normal human  skeletal muscle, DMD skeletal muscle, and skeletal muscle from patients with laminin α2 chain–deficient CMD  with antibodies against human IgG and IgM. The  plasma proteins showed intracellular fiber staining in  the quadriceps femoris muscle from DMD biopsies, indicating loss of membrane integrity. Positive staining of  grouped fibers was only detected in DMD patients. The  antibody against human IgG  did not show the same staining intensity as the antibody  against human IgM. Interestingly, not all IgG-positive fibers took up IgM molecules  (arrow), indicating different  sizes of membrane disruptions. This observation was  confirmed on serial sections  throughout the damaged area.  Bar 50, μm.
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Figure 8: Immunohistochemical staining of 7-μm cryosection from normal human skeletal muscle, DMD skeletal muscle, and skeletal muscle from patients with laminin α2 chain–deficient CMD with antibodies against human IgG and IgM. The plasma proteins showed intracellular fiber staining in the quadriceps femoris muscle from DMD biopsies, indicating loss of membrane integrity. Positive staining of grouped fibers was only detected in DMD patients. The antibody against human IgG did not show the same staining intensity as the antibody against human IgM. Interestingly, not all IgG-positive fibers took up IgM molecules (arrow), indicating different sizes of membrane disruptions. This observation was confirmed on serial sections throughout the damaged area. Bar 50, μm.

Mentions: To test whether the findings in the animal models could be reproduced in patients with DMD and laminin α2 chain– deficient CMD, we tested cryosections from diagnostic biopsies with antibodies against IgG and IgM. In three out of eight needle biopsies from DMD patients, we found IgG- and IgM-positive muscle fibers (Fig. 8). The globulin-positive fibers showed the same grouping pattern as that described for the mdx mice. On normal human muscle sections, IgG and IgM were detected only in the endo- and perimysium (Fig. 8). Interestingly, not all IgG-positive fibers in DMD patients showed IgM uptake into the cytoplasm (Fig. 8, arrow), possibly because of the different sizes of the molecules. This finding was confirmed by looking at serial sections of the biopsy samples. In the biopsies of eight patients with laminin α2 chain–deficient CMD, we never found grouped fibers with positive staining for Igs. Two of the CMD patients had a deletion in the LAMA2 gene similar to the dy2J mice and were previously characterized (Allamand et al., 1997). Single fibers with an intracellular staining signal for Igs were detected on CMD biopsies and showed morphological features of necrosis.


Animal models for muscular dystrophy show different patterns of sarcolemmal disruption.

Straub V, Rafael JA, Chamberlain JS, Campbell KP - J. Cell Biol. (1997)

Immunohistochemical staining of 7-μm cryosection from normal human  skeletal muscle, DMD skeletal muscle, and skeletal muscle from patients with laminin α2 chain–deficient CMD  with antibodies against human IgG and IgM. The  plasma proteins showed intracellular fiber staining in  the quadriceps femoris muscle from DMD biopsies, indicating loss of membrane integrity. Positive staining of  grouped fibers was only detected in DMD patients. The  antibody against human IgG  did not show the same staining intensity as the antibody  against human IgM. Interestingly, not all IgG-positive fibers took up IgM molecules  (arrow), indicating different  sizes of membrane disruptions. This observation was  confirmed on serial sections  throughout the damaged area.  Bar 50, μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139791&req=5

Figure 8: Immunohistochemical staining of 7-μm cryosection from normal human skeletal muscle, DMD skeletal muscle, and skeletal muscle from patients with laminin α2 chain–deficient CMD with antibodies against human IgG and IgM. The plasma proteins showed intracellular fiber staining in the quadriceps femoris muscle from DMD biopsies, indicating loss of membrane integrity. Positive staining of grouped fibers was only detected in DMD patients. The antibody against human IgG did not show the same staining intensity as the antibody against human IgM. Interestingly, not all IgG-positive fibers took up IgM molecules (arrow), indicating different sizes of membrane disruptions. This observation was confirmed on serial sections throughout the damaged area. Bar 50, μm.
Mentions: To test whether the findings in the animal models could be reproduced in patients with DMD and laminin α2 chain– deficient CMD, we tested cryosections from diagnostic biopsies with antibodies against IgG and IgM. In three out of eight needle biopsies from DMD patients, we found IgG- and IgM-positive muscle fibers (Fig. 8). The globulin-positive fibers showed the same grouping pattern as that described for the mdx mice. On normal human muscle sections, IgG and IgM were detected only in the endo- and perimysium (Fig. 8). Interestingly, not all IgG-positive fibers in DMD patients showed IgM uptake into the cytoplasm (Fig. 8, arrow), possibly because of the different sizes of the molecules. This finding was confirmed by looking at serial sections of the biopsy samples. In the biopsies of eight patients with laminin α2 chain–deficient CMD, we never found grouped fibers with positive staining for Igs. Two of the CMD patients had a deletion in the LAMA2 gene similar to the dy2J mice and were previously characterized (Allamand et al., 1997). Single fibers with an intracellular staining signal for Igs were detected on CMD biopsies and showed morphological features of necrosis.

Bottom Line: However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue.One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage.Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.

View Article: PubMed Central - PubMed

Affiliation: Department of, Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.

ABSTRACT
Genetic defects in a number of components of the dystrophin-glycoprotein complex (DGC) lead to distinct forms of muscular dystrophy. However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue. One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage. Using tracer molecules, we compared sarcolemmal integrity in animal models for muscular dystrophy and in muscular dystrophy patient samples. Evans blue, a low molecular weight diazo dye, does not cross into skeletal muscle fibers in normal mice. In contrast, mdx mice, a dystrophin-deficient animal model for Duchenne muscular dystrophy, showed significant Evans blue accumulation in skeletal muscle fibers. We also studied Evans blue dispersion in transgenic mice bearing different dystrophin mutations, and we demonstrated that cytoskeletal and sarcolemmal attachment of dystrophin might be a necessary requirement to prevent serious fiber damage. The extent of dye incorporation in transgenic mice correlated with the phenotypic severity of similar dystrophin mutations in humans. We furthermore assessed Evans blue incorporation in skeletal muscle of the dystrophia muscularis (dy/dy) mouse and its milder allelic variant, the dy2J/dy2J mouse, animal models for congenital muscular dystrophy. Surprisingly, these mice, which have defects in the laminin alpha2-chain, an extracellular ligand of the DGC, showed little Evans blue accumulation in their skeletal muscles. Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.

Show MeSH
Related in: MedlinePlus