Muscle Disease: The Muscular Dystrophies

Department of Medicine, Section of Cardiology, University of Chicago, Chicago, Illinois 60637, USA.
Annual Review of Pathology Mechanisms of Disease (Impact Factor: 18.75). 02/2007; 2(1):87-109. DOI: 10.1146/annurev.pathol.2.010506.091936
Source: PubMed


Dystrophic muscle disease can occur at any age. Early- or childhood-onset muscular dystrophies may be associated with profound loss of muscle function, affecting ambulation, posture, and cardiac and respiratory function. Late-onset muscular dystrophies or myopathies may be mild and associated with slight weakness and an inability to increase muscle mass. The phenotype of muscular dystrophy is an endpoint that arises from a diverse set of genetic pathways. Genes associated with muscular dystrophies encode proteins of the plasma membrane and extracellular matrix, and the sarcomere and Z band, as well as nuclear membrane components. Because muscle has such distinctive structural and regenerative properties, many of the genes implicated in these disorders target pathways unique to muscle or more highly expressed in muscle. This chapter reviews the basic structural properties of muscle and genetic mechanisms that lead to myopathy and muscular dystrophies that affect all age groups.

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    • "The mutation leads to progressive myopathy and muscle weakness coupled with cycles of muscle degeneration. Death eventually occurs due to severe respiratory and/or cardiac failure at approximately 20–30years of age [4], [5]. There is currently no effective cure for DMD [6]–[8]. "
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    ABSTRACT: Duchenne muscular dystrophy (DMD), one of the most common and lethal genetic disorders, and the mdx mouse myopathies are caused by a lack of dystrophin protein. These dystrophic muscles contain sporadic clusters of dystrophin-expressing revertant fibers (RFs), as detected by immunohistochemistry. RFs are known to arise from muscle precursor cells with spontaneous exon skipping (alternative splicing) and clonally expand in size with increasing age through the process of muscle degeneration/regeneration. The expansion of revertant clusters is thought to represent the cumulative history of muscle regeneration and proliferation of such precursor cells. However, the precise mechanisms by which RFs arise and expand are poorly understood. Here, to test the effects of mutation types and aging on RF expansion and muscle regeneration, we examined the number of RFs in mdx mice (containing a nonsense mutation in exon 23) and mdx52 mice (containing deletion mutation of exon 52) with the same C57BL/6 background at 2, 6, 12, and 18months of age. Mdx mice displayed a significantly higher number of RFs compared to mdx52 mice in all age groups, suggesting that revertant fiber expansion largely depends on the type of mutation and/or location in the gene. A significant increase in the expression and clustering levels of RFs was found beginning at 6months of age in mdx mice compared with mdx52 mice. In contrast to the significant expansion of RFs with increasing age, the number of centrally nucleated fibers and embryonic myosin heavy chain-positive fibers (indicative of cumulative and current muscle regeneration, respectively) decreased with age in both mouse strains. These results suggest that mutation types and aging differently affect revertant fiber expansion in mdx and mdx52 mice.
    Full-text · Article · Jul 2013 · PLoS ONE
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    • "Duchenne Muscular Dystrophy (DMD) is the most common X-linked degenerative muscle disease. The diagnostic marker for DMD is the absence of the cytoskeletal protein dystrophin, which plays a major structural role in muscle by providing stability to the sarcolemma during muscle contractions [1]. DMD still lacks an effective cure; although different therapeutic strategies for DMD are currently being explored [2-6], a variety of drawbacks has significantly delayed their clinical translation. "
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    ABSTRACT: Background Duchenne muscular dystrophy (DMD) is the most common X-linked muscle degenerative disease and it is due to the absence of the cytoskeletal protein dystrophin. Currently there is no effective treatment for DMD. Among the different strategies for achieving a functional recovery of the dystrophic muscle, the upregulation of the dystrophin-related gene utrophin is becoming more and more feasible. Results We have previously shown that the zinc finger-based artificial transcriptional factor “Jazz” corrects the dystrophic pathology in mdx mice by upregulating utrophin gene expression. Here we describe a novel artificial transcription factor, named “UtroUp”, engineered to further improve the DNA-binding specificity. UtroUp has been designed to recognise an extended DNA target sequence on both the human and mouse utrophin gene promoters. The UtroUp DNA-binding domain contains six zinc finger motifs in tandem, which is able to recognise an 18-base-pair DNA target sequence that statistically is present only once in the human genome. To achieve a higher transcriptional activation, we coupled the UtroUp DNA-binding domain with the innovative transcriptional activation domain, which was derived from the multivalent adaptor protein Che-1/AATF. We show that the artificial transcription factor UtroUp, due to its six zinc finger tandem motif, possesses a low dissociation constant that is consistent with a strong affinity/specificity toward its DNA-binding site. When expressed in mammalian cell lines, UtroUp promotes utrophin transcription and efficiently accesses active chromatin promoting accumulation of the acetylated form of histone H3 in the utrophin promoter locus. Conclusions This novel artificial molecule may represent an improved platform for the development of future applications in DMD treatment.
    Full-text · Article · Jan 2013 · BMC Molecular Biology
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    • "These connections occur both along the axis of contraction at the myotendinous junction (MTJ), where the muscle inserts into a fibrous tendon that attaches to the bony skeleton, and radially at specialized membrane domains like the costameres [1, 2], where the muscle attaches to surrounding fibrous sheaths called the endomysium and the perimysium. The importance of muscle-ECM connections to muscle structure and function is evident from the number of myopathies and muscular dystrophies, including Duchenne muscular dystrophy, that result from disturbance of the multiprotein complexes that support the linkage [3]. "
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    ABSTRACT: During development, skeletal myoblasts differentiate into myocytes and skeletal myotubes with mature contractile structures that are precisely oriented with respect to surrounding cells and tissues. Establishment of this highly ordered structure requires reciprocal interactions between the differentiating myocytes and the surrounding extracellular matrix to form correctly positioned and well-organized attachments from the skeletal muscle to the bony skeleton. Using the developing zebrafish embryo as a model, we examined the relationship between new myofibril assembly and the organization of the membrane domains involved in cell-extracellular matrix interactions. We determined that depletion of obscurin, a giant muscle protein, resulted in irregular cell morphology and disturbed extracellular matrix organization during skeletal muscle development. The resulting impairment of myocyte organization was associated with disturbance of the internal architecture of the myocyte suggesting that obscurin participates in organizing the internal structure of the myocyte and translating those structural cues to surrounding cells and tissues.
    Full-text · Article · Nov 2011 · BioMed Research International
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