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Enhanced expression of the alpha 7 beta 1 integrin reduces muscular dystrophy and restores viability in dystrophic mice.

Burkin DJ, Wallace GQ, Nicol KJ, Kaufman DJ, Kaufman SJ - J. Cell Biol. (2001)

Bottom Line: Therefore, the molecular continuity between the extracellular matrix and cell cytoskeleton is essential for the structural and functional integrity of skeletal muscle.Concomitant with the increase in the alpha 7 chain, its heterodimeric partner, beta 1D, was also increased in the transgenic animals.This suggests that enhanced expression of the alpha 7 beta 1 integrin may provide a novel approach to treat DMD and other muscle diseases that arise due to defects in the dystrophin glycoprotein complex.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois 61801, USA.

ABSTRACT
Muscle fibers attach to laminin in the basal lamina using two distinct mechanisms: the dystrophin glycoprotein complex and the alpha 7 beta 1 integrin. Defects in these linkage systems result in Duchenne muscular dystrophy (DMD), alpha 2 laminin congenital muscular dystrophy, sarcoglycan-related muscular dystrophy, and alpha 7 integrin congenital muscular dystrophy. Therefore, the molecular continuity between the extracellular matrix and cell cytoskeleton is essential for the structural and functional integrity of skeletal muscle. To test whether the alpha 7 beta 1 integrin can compensate for the absence of dystrophin, we expressed the rat alpha 7 chain in mdx/utr(-/-) mice that lack both dystrophin and utrophin. These mice develop a severe muscular dystrophy highly akin to that in DMD, and they also die prematurely. Using the muscle creatine kinase promoter, expression of the alpha 7BX2 integrin chain was increased 2.0-2.3-fold in mdx/utr(-/-) mice. Concomitant with the increase in the alpha 7 chain, its heterodimeric partner, beta 1D, was also increased in the transgenic animals. Transgenic expression of the alpha 7BX2 chain in the mdx/utr(-/-) mice extended their longevity by threefold, reduced kyphosis and the development of muscle disease, and maintained mobility and the structure of the neuromuscular junction. Thus, bolstering alpha 7 beta 1 integrin-mediated association of muscle cells with the extracellular matrix alleviates many of the symptoms of disease observed in mdx/utr(-/-) mice and compensates for the absence of the dystrophin- and utrophin-mediated linkage systems. This suggests that enhanced expression of the alpha 7 beta 1 integrin may provide a novel approach to treat DMD and other muscle diseases that arise due to defects in the dystrophin glycoprotein complex. A video that contrasts kyphosis, gait, joint contractures, and mobility in mdx/utr(-/-) and alpha 7BX2-mdx/utr(-/-) mice can be accessed at http://www.jcb.org/cgi/content/full/152/6/1207.

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Structure of the NMJ in 5-wk-old wild-type, mdx/utr−/−, and α7BX2-mdx/utr−/− mice. (Left) En face views of AChRs in the postsynaptic membrane detected with rhodamine-labeled α-bungarotoxin. In wild-type mice, the junctions appear continuous, folded, and uninterrupted. In mdx/utr−/− mice, the distribution of AChRs is discontinuous and organized into discrete boutons. The organization of the postsynaptic membrane in α7BX2-mdx/utr−/− transgenic mice has a more continuous (normal) pattern. (Right) Ultrastructural changes in the NMJ. The postsynatic membrane of wild-type mice is highly folded (arrowheads). In contrast, mdx/utr−/− mice have little or no membrane folding. Expression of the α7BX2 transgene in mdx/utr−/− mice results in a postsynaptic membrane with partially restored folding (arrowheads). Bar, 1 μm.
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Figure 10: Structure of the NMJ in 5-wk-old wild-type, mdx/utr−/−, and α7BX2-mdx/utr−/− mice. (Left) En face views of AChRs in the postsynaptic membrane detected with rhodamine-labeled α-bungarotoxin. In wild-type mice, the junctions appear continuous, folded, and uninterrupted. In mdx/utr−/− mice, the distribution of AChRs is discontinuous and organized into discrete boutons. The organization of the postsynaptic membrane in α7BX2-mdx/utr−/− transgenic mice has a more continuous (normal) pattern. (Right) Ultrastructural changes in the NMJ. The postsynatic membrane of wild-type mice is highly folded (arrowheads). In contrast, mdx/utr−/− mice have little or no membrane folding. Expression of the α7BX2 transgene in mdx/utr−/− mice results in a postsynaptic membrane with partially restored folding (arrowheads). Bar, 1 μm.

Mentions: Endogeneous mouse immunoglobulin was blocked before the addition of monoclonal antibodies using 60 μg/ml goat anti–mouse monovalent Fabs (Jackson ImmunoResearch Laboratories) in 1% horse serum in PBS for 30 min at room temperature. Slides were then washed three times for 5 min in 1% horse serum in PBS. Primary antibodies were added for 1 h at room temperature. Slides were washed three times for 5 min in 1% horse serum in PBS. Primary antibodies were detected with a 1:100 dilution of FITC-labeled donkey anti–mouse or anti–rabbit antibody in 1% horse serum in PBS. Slides were mounted using Vectorshield mountant (Vector Laboratories). Localization of the antibody was observed with a ZEISS Photomicroscope III. Images were acquired with a Sony DXC9000 color video CCD camera using SiteCam software and a ZEISS Axiocam digital camera (see Fig. 10).


Enhanced expression of the alpha 7 beta 1 integrin reduces muscular dystrophy and restores viability in dystrophic mice.

Burkin DJ, Wallace GQ, Nicol KJ, Kaufman DJ, Kaufman SJ - J. Cell Biol. (2001)

Structure of the NMJ in 5-wk-old wild-type, mdx/utr−/−, and α7BX2-mdx/utr−/− mice. (Left) En face views of AChRs in the postsynaptic membrane detected with rhodamine-labeled α-bungarotoxin. In wild-type mice, the junctions appear continuous, folded, and uninterrupted. In mdx/utr−/− mice, the distribution of AChRs is discontinuous and organized into discrete boutons. The organization of the postsynaptic membrane in α7BX2-mdx/utr−/− transgenic mice has a more continuous (normal) pattern. (Right) Ultrastructural changes in the NMJ. The postsynatic membrane of wild-type mice is highly folded (arrowheads). In contrast, mdx/utr−/− mice have little or no membrane folding. Expression of the α7BX2 transgene in mdx/utr−/− mice results in a postsynaptic membrane with partially restored folding (arrowheads). Bar, 1 μm.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199213&req=5

Figure 10: Structure of the NMJ in 5-wk-old wild-type, mdx/utr−/−, and α7BX2-mdx/utr−/− mice. (Left) En face views of AChRs in the postsynaptic membrane detected with rhodamine-labeled α-bungarotoxin. In wild-type mice, the junctions appear continuous, folded, and uninterrupted. In mdx/utr−/− mice, the distribution of AChRs is discontinuous and organized into discrete boutons. The organization of the postsynaptic membrane in α7BX2-mdx/utr−/− transgenic mice has a more continuous (normal) pattern. (Right) Ultrastructural changes in the NMJ. The postsynatic membrane of wild-type mice is highly folded (arrowheads). In contrast, mdx/utr−/− mice have little or no membrane folding. Expression of the α7BX2 transgene in mdx/utr−/− mice results in a postsynaptic membrane with partially restored folding (arrowheads). Bar, 1 μm.
Mentions: Endogeneous mouse immunoglobulin was blocked before the addition of monoclonal antibodies using 60 μg/ml goat anti–mouse monovalent Fabs (Jackson ImmunoResearch Laboratories) in 1% horse serum in PBS for 30 min at room temperature. Slides were then washed three times for 5 min in 1% horse serum in PBS. Primary antibodies were added for 1 h at room temperature. Slides were washed three times for 5 min in 1% horse serum in PBS. Primary antibodies were detected with a 1:100 dilution of FITC-labeled donkey anti–mouse or anti–rabbit antibody in 1% horse serum in PBS. Slides were mounted using Vectorshield mountant (Vector Laboratories). Localization of the antibody was observed with a ZEISS Photomicroscope III. Images were acquired with a Sony DXC9000 color video CCD camera using SiteCam software and a ZEISS Axiocam digital camera (see Fig. 10).

Bottom Line: Therefore, the molecular continuity between the extracellular matrix and cell cytoskeleton is essential for the structural and functional integrity of skeletal muscle.Concomitant with the increase in the alpha 7 chain, its heterodimeric partner, beta 1D, was also increased in the transgenic animals.This suggests that enhanced expression of the alpha 7 beta 1 integrin may provide a novel approach to treat DMD and other muscle diseases that arise due to defects in the dystrophin glycoprotein complex.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Structural Biology, University of Illinois, Urbana, Illinois 61801, USA.

ABSTRACT
Muscle fibers attach to laminin in the basal lamina using two distinct mechanisms: the dystrophin glycoprotein complex and the alpha 7 beta 1 integrin. Defects in these linkage systems result in Duchenne muscular dystrophy (DMD), alpha 2 laminin congenital muscular dystrophy, sarcoglycan-related muscular dystrophy, and alpha 7 integrin congenital muscular dystrophy. Therefore, the molecular continuity between the extracellular matrix and cell cytoskeleton is essential for the structural and functional integrity of skeletal muscle. To test whether the alpha 7 beta 1 integrin can compensate for the absence of dystrophin, we expressed the rat alpha 7 chain in mdx/utr(-/-) mice that lack both dystrophin and utrophin. These mice develop a severe muscular dystrophy highly akin to that in DMD, and they also die prematurely. Using the muscle creatine kinase promoter, expression of the alpha 7BX2 integrin chain was increased 2.0-2.3-fold in mdx/utr(-/-) mice. Concomitant with the increase in the alpha 7 chain, its heterodimeric partner, beta 1D, was also increased in the transgenic animals. Transgenic expression of the alpha 7BX2 chain in the mdx/utr(-/-) mice extended their longevity by threefold, reduced kyphosis and the development of muscle disease, and maintained mobility and the structure of the neuromuscular junction. Thus, bolstering alpha 7 beta 1 integrin-mediated association of muscle cells with the extracellular matrix alleviates many of the symptoms of disease observed in mdx/utr(-/-) mice and compensates for the absence of the dystrophin- and utrophin-mediated linkage systems. This suggests that enhanced expression of the alpha 7 beta 1 integrin may provide a novel approach to treat DMD and other muscle diseases that arise due to defects in the dystrophin glycoprotein complex. A video that contrasts kyphosis, gait, joint contractures, and mobility in mdx/utr(-/-) and alpha 7BX2-mdx/utr(-/-) mice can be accessed at http://www.jcb.org/cgi/content/full/152/6/1207.

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Related in: MedlinePlus