Homozyous mice are viable and fertile. They develop severe muscular dystrophy and cardiomyopathy with focal areas of necrosis. Severe dystrophic changes including necrosis, dystrophic calcification, fatty infiltration, central nucleation, fibrosis, atrophy and hypertrophy are detected in diaphragm and calf/thigh muscle. Some of these changes occur in 4-week-old animals and accumulate with age. At 20 weeks of age, several regions of focal myocardial necrosis have been observed; small areas of necrotic myocardiocytes may be observed as early as 9 weeks of age. At 30 weeks of age, large areas of fibrosis are detected. Sarcoglycan-sarcospan and dystroglycan complexes are disrupted in skeletal, cardiac, and smooth muscle membranes. Loss of the sarcoglycan-sarcospan complex in vascular smooth muscle results in vascular irregularities in heart, diaphragm, and kidneys. Vascular constrictions in skeletal muscle, cardiac muscle and kidneys is observed. Epsilon-sarcoglycan (SGCE) is also reduced in membrane preparations of striated and smooth muscle. Northern blot analysis of skeletal muscle with an exon 6 probe reveals no transcript in the skeletal muscle of homozygous mice. This mutant mouse strain represents a model that may be useful in studies of muscular dystrophy, cardiomyopathy, and smooth muscle dysfunction.
