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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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Loss of membrane integrity is indicated by intracellular  staining of serum proteins. EBD-positive fibers in skeletal muscle  from mdx mice also showed positive staining with antibodies  against albumin on the same section. (A) Double staining for  EBD (a) and albumin (b) in an 8-wk-old mdx mouse. (B) Skeletal  muscle of 10-wk-old mice that were not injected with EBD were  studied for uptake of serum proteins into muscle fibers. Immunohistochemical staining of 7-μm femoral quadriceps cryosection  from uninjected normal and mdx mice with antibodies against  mouse IgG (a and b), mouse IgM (c and d), and mouse albumin  (e and f) showed accumulation of the serum markers in mdx skeletal muscle. No difference of protein uptake into muscle fibers  was detected between control and dy/dy mice. Bar, 50 μm.
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Figure 4: Loss of membrane integrity is indicated by intracellular staining of serum proteins. EBD-positive fibers in skeletal muscle from mdx mice also showed positive staining with antibodies against albumin on the same section. (A) Double staining for EBD (a) and albumin (b) in an 8-wk-old mdx mouse. (B) Skeletal muscle of 10-wk-old mice that were not injected with EBD were studied for uptake of serum proteins into muscle fibers. Immunohistochemical staining of 7-μm femoral quadriceps cryosection from uninjected normal and mdx mice with antibodies against mouse IgG (a and b), mouse IgM (c and d), and mouse albumin (e and f) showed accumulation of the serum markers in mdx skeletal muscle. No difference of protein uptake into muscle fibers was detected between control and dy/dy mice. Bar, 50 μm.

Mentions: The chief characteristic of the EBD is its ability to form a tight complex with serum albumin within seconds after its injection into the bloodstream (Reeve, 1957). In view of the tight association between EBD and albumin, areas of blue macroscopic staining were taken to represent regions of albumin uptake into muscle fibers. To demonstrate that EBD-positive muscle fibers in mdx mice do take up albumin, we stained cryosections for albumin. We could show that the same fibers that took up the dye were also positive for albumin staining (Fig. 4 A).


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

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

Loss of membrane integrity is indicated by intracellular  staining of serum proteins. EBD-positive fibers in skeletal muscle  from mdx mice also showed positive staining with antibodies  against albumin on the same section. (A) Double staining for  EBD (a) and albumin (b) in an 8-wk-old mdx mouse. (B) Skeletal  muscle of 10-wk-old mice that were not injected with EBD were  studied for uptake of serum proteins into muscle fibers. Immunohistochemical staining of 7-μm femoral quadriceps cryosection  from uninjected normal and mdx mice with antibodies against  mouse IgG (a and b), mouse IgM (c and d), and mouse albumin  (e and f) showed accumulation of the serum markers in mdx skeletal muscle. No difference of protein uptake into muscle fibers  was detected between control and dy/dy mice. Bar, 50 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 4: Loss of membrane integrity is indicated by intracellular staining of serum proteins. EBD-positive fibers in skeletal muscle from mdx mice also showed positive staining with antibodies against albumin on the same section. (A) Double staining for EBD (a) and albumin (b) in an 8-wk-old mdx mouse. (B) Skeletal muscle of 10-wk-old mice that were not injected with EBD were studied for uptake of serum proteins into muscle fibers. Immunohistochemical staining of 7-μm femoral quadriceps cryosection from uninjected normal and mdx mice with antibodies against mouse IgG (a and b), mouse IgM (c and d), and mouse albumin (e and f) showed accumulation of the serum markers in mdx skeletal muscle. No difference of protein uptake into muscle fibers was detected between control and dy/dy mice. Bar, 50 μm.
Mentions: The chief characteristic of the EBD is its ability to form a tight complex with serum albumin within seconds after its injection into the bloodstream (Reeve, 1957). In view of the tight association between EBD and albumin, areas of blue macroscopic staining were taken to represent regions of albumin uptake into muscle fibers. To demonstrate that EBD-positive muscle fibers in mdx mice do take up albumin, we stained cryosections for albumin. We could show that the same fibers that took up the dye were also positive for albumin staining (Fig. 4 A).

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