Limits...
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.

Show MeSH

Related in: MedlinePlus

EBD staining on 7-μm cryosection of skeletal muscle  from four transgenic/mdx mice. The top portion of the picture  shows a model of the normal dystrophin gene. The femoral quadriceps muscle of the Dp71 mouse (20 wk old) revealed the same  amount of fiber damage in the EBD assay as the original mdx  mutant. Mice with a deletion of dystrophin exons 71–74 (17 wk  old) did not show significantly more dye uptake into the femoral  quadriceps muscle than seen in control animals. The Δ17-48  transgenic/mdx mouse (9 wk old), which has a deletion in the rod  domain of dystrophin, showed few dye-positive fibers in the  quadriceps femoris muscle. The Δ3-7 transgenic/mdx mouse (10  wk old), which has a deletion in the amino-terminal actin-binding  domain of dystrophin, showed dye-positive fibers in the diaphragm (Δ3-7), as well as in the quadriceps femoris muscle. Bar,  50 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2139791&req=5

Figure 5: EBD staining on 7-μm cryosection of skeletal muscle from four transgenic/mdx mice. The top portion of the picture shows a model of the normal dystrophin gene. The femoral quadriceps muscle of the Dp71 mouse (20 wk old) revealed the same amount of fiber damage in the EBD assay as the original mdx mutant. Mice with a deletion of dystrophin exons 71–74 (17 wk old) did not show significantly more dye uptake into the femoral quadriceps muscle than seen in control animals. The Δ17-48 transgenic/mdx mouse (9 wk old), which has a deletion in the rod domain of dystrophin, showed few dye-positive fibers in the quadriceps femoris muscle. The Δ3-7 transgenic/mdx mouse (10 wk old), which has a deletion in the amino-terminal actin-binding domain of dystrophin, showed dye-positive fibers in the diaphragm (Δ3-7), as well as in the quadriceps femoris muscle. Bar, 50 μm.

Mentions: To test the importance of distinct dystrophin domains for maintaining sarcolemmal integrity, we injected EBD into transgenic lines of mdx mice expressing different portions of the dystrophin molecule (Fig. 5). Intravenous injection of EBD into Dp71 mice led to incorporation of the tracer into skeletal muscles by visual inspection. The intensity and the extent of stained regions was similar to that of mdx mice. In contrast, Δ17-48 transgenic/mdx mice, which mimic the dystrophin mutation in an extremely mild case of Becker muscular dystrophy (England et al., 1990; Phelps et al., 1995), and Δ71-74 transgenic/mdx mice, which have been reported to show no dystrophic phenotype up to at least 2 yr of age (Rafael et al., 1994, 1996), did not demonstrate macroscopic dye uptake after intravenous injections. The Δ3-7 transgenic mdx mice, in which the expression of a full-length dystrophin construct deleted for the amino-terminal, actin-binding domain improves the mdx pathology to a mild “Becker-like” phenotype (Corrado et al., 1996), did take up EBD into skeletal muscle fibers. However, sarcolemmal damage in Δ3-7 transgenic/mdx mice, as assessed by EBD incorporation, appeared less severe than in the mdx or the Dp71 mice (Fig. 5). The femoral quadriceps muscle and the diaphragm were the only muscles in which dye accumulation was visually observed in Δ3-7 transgenic/mdx mice.


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

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

EBD staining on 7-μm cryosection of skeletal muscle  from four transgenic/mdx mice. The top portion of the picture  shows a model of the normal dystrophin gene. The femoral quadriceps muscle of the Dp71 mouse (20 wk old) revealed the same  amount of fiber damage in the EBD assay as the original mdx  mutant. Mice with a deletion of dystrophin exons 71–74 (17 wk  old) did not show significantly more dye uptake into the femoral  quadriceps muscle than seen in control animals. The Δ17-48  transgenic/mdx mouse (9 wk old), which has a deletion in the rod  domain of dystrophin, showed few dye-positive fibers in the  quadriceps femoris muscle. The Δ3-7 transgenic/mdx mouse (10  wk old), which has a deletion in the amino-terminal actin-binding  domain of dystrophin, showed dye-positive fibers in the diaphragm (Δ3-7), as well as in the quadriceps femoris muscle. Bar,  50 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: EBD staining on 7-μm cryosection of skeletal muscle from four transgenic/mdx mice. The top portion of the picture shows a model of the normal dystrophin gene. The femoral quadriceps muscle of the Dp71 mouse (20 wk old) revealed the same amount of fiber damage in the EBD assay as the original mdx mutant. Mice with a deletion of dystrophin exons 71–74 (17 wk old) did not show significantly more dye uptake into the femoral quadriceps muscle than seen in control animals. The Δ17-48 transgenic/mdx mouse (9 wk old), which has a deletion in the rod domain of dystrophin, showed few dye-positive fibers in the quadriceps femoris muscle. The Δ3-7 transgenic/mdx mouse (10 wk old), which has a deletion in the amino-terminal actin-binding domain of dystrophin, showed dye-positive fibers in the diaphragm (Δ3-7), as well as in the quadriceps femoris muscle. Bar, 50 μm.
Mentions: To test the importance of distinct dystrophin domains for maintaining sarcolemmal integrity, we injected EBD into transgenic lines of mdx mice expressing different portions of the dystrophin molecule (Fig. 5). Intravenous injection of EBD into Dp71 mice led to incorporation of the tracer into skeletal muscles by visual inspection. The intensity and the extent of stained regions was similar to that of mdx mice. In contrast, Δ17-48 transgenic/mdx mice, which mimic the dystrophin mutation in an extremely mild case of Becker muscular dystrophy (England et al., 1990; Phelps et al., 1995), and Δ71-74 transgenic/mdx mice, which have been reported to show no dystrophic phenotype up to at least 2 yr of age (Rafael et al., 1994, 1996), did not demonstrate macroscopic dye uptake after intravenous injections. The Δ3-7 transgenic mdx mice, in which the expression of a full-length dystrophin construct deleted for the amino-terminal, actin-binding domain improves the mdx pathology to a mild “Becker-like” phenotype (Corrado et al., 1996), did take up EBD into skeletal muscle fibers. However, sarcolemmal damage in Δ3-7 transgenic/mdx mice, as assessed by EBD incorporation, appeared less severe than in the mdx or the Dp71 mice (Fig. 5). The femoral quadriceps muscle and the diaphragm were the only muscles in which dye accumulation was visually observed in Δ3-7 transgenic/mdx mice.

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