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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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Genotyping transgenic α7BX2-mdx/utr−/− mice. (A) The α7BX2 transgene (tg) was detected by PCR using primers that amplify between the MCK promoter and the α7 cDNA sequence. Lanes 2 and 3 are positive for the MCK-α7BX2 transgene. (B) Southern blot analysis using a rat α7-specific probe of EcoRI- and KpnI-digested genomic DNA. The 7.1-kb band corresponding to the rat transgene construct is detected in lanes 4–6. A higher 14.2-kb transgene dimer was also detected. Samples in these lanes are from α7BX2-mdx/utr−/− mice. DNA in lanes 1–3 are from nontransgenic mice. (C) Determining the status of the utrophin gene by PCR. Only mutant utr alleles are detected in lanes 1 and 4, identifying utr−/− mice. One wild-type (wt) and one mutant allele are amplified in lane 2, identifying a utr+/− mouse. Lane 3 is wild-type at both utr loci. (D) Determining the status of the dystrophin gene by PCR. The mdx primer set detects the point mutation in the dystrophin gene, whereas the wt primers detect only the wild-type allele. Mouse 2 is wild-type at the dystrophin locus, mouse 3 is heterozygous (mdx/+), and mouse 4 is mdx. Lane 1 contains no DNA.
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Figure 1: Genotyping transgenic α7BX2-mdx/utr−/− mice. (A) The α7BX2 transgene (tg) was detected by PCR using primers that amplify between the MCK promoter and the α7 cDNA sequence. Lanes 2 and 3 are positive for the MCK-α7BX2 transgene. (B) Southern blot analysis using a rat α7-specific probe of EcoRI- and KpnI-digested genomic DNA. The 7.1-kb band corresponding to the rat transgene construct is detected in lanes 4–6. A higher 14.2-kb transgene dimer was also detected. Samples in these lanes are from α7BX2-mdx/utr−/− mice. DNA in lanes 1–3 are from nontransgenic mice. (C) Determining the status of the utrophin gene by PCR. Only mutant utr alleles are detected in lanes 1 and 4, identifying utr−/− mice. One wild-type (wt) and one mutant allele are amplified in lane 2, identifying a utr+/− mouse. Lane 3 is wild-type at both utr loci. (D) Determining the status of the dystrophin gene by PCR. The mdx primer set detects the point mutation in the dystrophin gene, whereas the wt primers detect only the wild-type allele. Mouse 2 is wild-type at the dystrophin locus, mouse 3 is heterozygous (mdx/+), and mouse 4 is mdx. Lane 1 contains no DNA.

Mentions: The presence of the rat α7 transgene was detected by both PCR and Southern blot analyses. Using MCKI and AATII primers, a 455-bp product was amplified only in transgenic mice (Fig. 1 A). Southern blot analysis produced a strong 7.1-kb band only in transgenic mice. This is the expected size of the EcoRI and KpnI digested MCK-α7BX2 construct (Fig. 1 B). A weak 14.2-kb band was also detected by Southern blot analysis, suggesting that a portion of the constructs had lost one of these restriction sites.


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)

Genotyping transgenic α7BX2-mdx/utr−/− mice. (A) The α7BX2 transgene (tg) was detected by PCR using primers that amplify between the MCK promoter and the α7 cDNA sequence. Lanes 2 and 3 are positive for the MCK-α7BX2 transgene. (B) Southern blot analysis using a rat α7-specific probe of EcoRI- and KpnI-digested genomic DNA. The 7.1-kb band corresponding to the rat transgene construct is detected in lanes 4–6. A higher 14.2-kb transgene dimer was also detected. Samples in these lanes are from α7BX2-mdx/utr−/− mice. DNA in lanes 1–3 are from nontransgenic mice. (C) Determining the status of the utrophin gene by PCR. Only mutant utr alleles are detected in lanes 1 and 4, identifying utr−/− mice. One wild-type (wt) and one mutant allele are amplified in lane 2, identifying a utr+/− mouse. Lane 3 is wild-type at both utr loci. (D) Determining the status of the dystrophin gene by PCR. The mdx primer set detects the point mutation in the dystrophin gene, whereas the wt primers detect only the wild-type allele. Mouse 2 is wild-type at the dystrophin locus, mouse 3 is heterozygous (mdx/+), and mouse 4 is mdx. Lane 1 contains no DNA.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 1: Genotyping transgenic α7BX2-mdx/utr−/− mice. (A) The α7BX2 transgene (tg) was detected by PCR using primers that amplify between the MCK promoter and the α7 cDNA sequence. Lanes 2 and 3 are positive for the MCK-α7BX2 transgene. (B) Southern blot analysis using a rat α7-specific probe of EcoRI- and KpnI-digested genomic DNA. The 7.1-kb band corresponding to the rat transgene construct is detected in lanes 4–6. A higher 14.2-kb transgene dimer was also detected. Samples in these lanes are from α7BX2-mdx/utr−/− mice. DNA in lanes 1–3 are from nontransgenic mice. (C) Determining the status of the utrophin gene by PCR. Only mutant utr alleles are detected in lanes 1 and 4, identifying utr−/− mice. One wild-type (wt) and one mutant allele are amplified in lane 2, identifying a utr+/− mouse. Lane 3 is wild-type at both utr loci. (D) Determining the status of the dystrophin gene by PCR. The mdx primer set detects the point mutation in the dystrophin gene, whereas the wt primers detect only the wild-type allele. Mouse 2 is wild-type at the dystrophin locus, mouse 3 is heterozygous (mdx/+), and mouse 4 is mdx. Lane 1 contains no DNA.
Mentions: The presence of the rat α7 transgene was detected by both PCR and Southern blot analyses. Using MCKI and AATII primers, a 455-bp product was amplified only in transgenic mice (Fig. 1 A). Southern blot analysis produced a strong 7.1-kb band only in transgenic mice. This is the expected size of the EcoRI and KpnI digested MCK-α7BX2 construct (Fig. 1 B). A weak 14.2-kb band was also detected by Southern blot analysis, suggesting that a portion of the constructs had lost one of these restriction sites.

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.

Show MeSH
Related in: MedlinePlus