[Mutations of the dystrophin gene in dilated cardiomyopathy]

X-linked dilated cardiomyopathy(XLDCM) is caused by mutations of the dystrophin gene, which was originally cloned as the responsible gene for Duchenne muscular dystrophy and Becker muscular dystrophy. Mutations due to XLDCM are centered on 5' end of the gene, especially M-promoter and the adjacent region. However, other mutations are dispersed and cannot be characterized. Three mechanisms have been proposed by which the involvement of cardiac muscle is so severe in spite of the lack of skeletal muscle symptoms; 1) up-regulation of B- and P-dystrophin in merely skeletal muscle compensating for the defect of M-dystrophin, 2) dysfunction of some parts of dystrophin specifically essential to cardiac muscle, 3) different expression patterns of mutant mRNA between cardiac and skeletal muscle.