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Disruption of the dystrophin-glycoprotein complex in the cardiomyopathic hamster
S L Roberds1, J M Ervasti, R D Anderson
1Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City 52242.
Insights
Defects in dystrophin-associated proteins, particularly the 50-kDa glycoprotein, are linked to cardiomyopathy in hamsters. This disruption of the dystrophin-glycoprotein complex may cause heart and skeletal muscle cell death.
Area of Science:
- Cardiovascular Biology
- Muscle Physiology
- Molecular Genetics
Background:
- Cardiomyopathies encompass diverse primary cardiac diseases with often unclear origins.
- Hereditary cardiomyopathies can stem from genetic defects, such as those in the dystrophin gene seen in muscular dystrophy.
- Dystrophin-associated proteins form a complex linking the cytoskeleton to the extracellular matrix, crucial for muscle integrity.
Purpose of the Study:
- To investigate the role of dystrophin-associated proteins in a specific strain of cardiomyopathic hamsters (BIO 14.6).
- To determine if deficiencies in dystrophin-associated proteins contribute to the observed cardiomyopathy and myopathy in these animals.
- To explore the potential link between the dystrophin-glycoprotein complex and myocyte necrosis.
Main Methods:
- Biochemical analysis of dystrophin-associated protein levels in cardiac and skeletal muscles of BIO 14.6 hamsters.
- Comparison of protein expression patterns between affected hamsters and healthy controls.
- Assessment of the structural integrity of the dystrophin-glycoprotein complex.
Main Results:
- A specific deficiency of the 50-kDa dystrophin-associated glycoprotein was identified in both cardiac and skeletal muscles of BIO 14.6 hamsters.
- While other dystrophin-associated proteins were preserved in skeletal muscle, the dystrophin-dystroglycan linkage was disrupted.
- All dystrophin-associated proteins showed reduced abundance in the hearts of cardiomyopathic hamsters, correlating with disease severity.
Conclusions:
- Disruption of the dystrophin-glycoprotein complex is implicated in the pathogenesis of cardiomyopathy and myopathy in BIO 14.6 hamsters.
- The specific deficiency of the 50-kDa dystrophin-associated glycoprotein may be a key factor in cardiac and skeletal muscle cell death.
- These findings suggest that abnormalities in the dystrophin-associated protein complex can lead to diverse forms of cardiomyopathy.
Abstract:
Cardiomyopathies are a diverse group of primary cardiac diseases, most of which have a poorly understood etiology. One type of hereditary cardiomyopathy is caused by defects in the dystrophin gene in Duchenne and Becker muscular dystrophy patients. Our laboratory has identified a complex of dystrophin-associated proteins in skeletal and cardiac muscle which span the sarcolemma, linking the subsarcolemmal cytoskeleton to the extracellular matrix. The absence of dystrophin in Duchenne muscular dystrophy patients leads to the loss of dystrophin-associated proteins in both skeletal and cardiac muscle, suggesting that a primary loss of one or more dystrophin-associated proteins might lead to other forms of cardiomyopathy. Here we report the specific deficiency of the 50-kDa dystrophin-associated glycoprotein in cardiac and skeletal muscles of the BIO 14.6 strain of cardiomyopathic hamsters, which experience both autosomal recessive cardiomyopathy and myopathy. Other dystrophin-associated proteins are well preserved in myopathic hamster skeletal muscle, but the link between dystrophin and dystroglycan is disrupted. All dystrophin-associated proteins are decreased in abundance in the cardiomyopathic hamster heart, perhaps explaining why the cardiomyopathy is more severe than the myopathy. Thus, the disruption of the dystrophin-glycoprotein complex may play a role in skeletal and cardiac myocyte necrosis of the cardiomyopathic hamster.