DECREASED OSMOTIC STABILITY OF DYSTROPHIN-LESS MUSCLE-CELLS FROM THE MDX MOUSE

HUMAN X-linked Duchenne and Becker muscular dystrophies are due to defects in dystrophin, the product of an exceptionally large gene1,2. Although dystrophin has been characterized as a spectrin-like3 submembranous4 cytoskeletal protein, there is no experimental evidence for its function in the structural maintenance of muscle5. Current hypotheses attribute necrosis of hystrophin-less fibres in situ to mechanical weakening of the outer membrane6, to an excessive influx of Ca2+ ions7,8, or to a combination of these two mechanisms, possibly mediated by stretch-sensitive ion channels9. Using hypo-osmotic shock to determine stress resistance10 and a mouse model (mdx)11,12 for the human disease, we show that functional dystrophin contributes to the stability of both cultured myotubes and isolated mature muscle fibres.