Developmental study of the expression of dystrophin in cultured human muscle aneurally and innervated with fetal rat spinal cord

Abstract

So far there have been no developmental studies including the influences of innervation and contractile activity on the expression of dystrophin in cultured human muscle. We performed immunocytochemical studies of the localization of dystrophin on aneurally cultured non-contracting (AMs) and innervated continuously contracting cross-striated human nuscle fibers (ICMs) with fetal rat spinal cord from normal and Duchenne muscular dystrophy (DMD) biopsied muscles. In normal AMs, myoblasts and some immature AMs, myoblasts and some immature AMs showed negative staining of dystrophin, but many AMs had a patchy (discontinous) distribution of dystrophin in the subplasmalemmal region and with some granularity near the sarcolemma and in the deeper cytoplasm. In normal ICMs, dystrophin was localized continously at the inner aspect of the sarcolemmal membrane and some periodic dense patterns were detected in some areas. Both AMs and ICMs from DMD had negative staining of dystrophin. To investigate the muscle contractile activity on the distribution of dystrophin, were paralyzed ICMs with tetrodotoxin (TTX) for two weeks from the first appearance of muscle contractions. In paralyzed innervated muscles (PIMs), dystrophin remained in a patchy (discontinuous) pattern at the inner aspect of the plasmalemma similar to that in AMs. It is strongly suggested that muscle contractile activity plays an important role in the continous and even distribution of dystrophin at the sarcolemma during development.