IMMUNOGOLD LOCALIZATION OF THE 43-KDA DYSTROGLYCAN AT THE PLASMA-MEMBRANE IN CONTROL AND DYSTROPHIC HUMAN MUSCLE

Immunofluorescence and immunogold labelling were used to localise the 43-kDa dystrophin-associated glycoprotein (43DAG) of the dystrophingly coprotein complex in control and Duchenne muscular dystrophy (DMD) bio psies. In control muscle 43DAG was localised by immunofluorescence to the periphery of the fibre and, by immunogold, was further delimited t o the plasma membrane. The labelling was indistinguishable from that p reviously reported for the dystrophin C terminus [5]. Moreover, the di stance separating adjacent 43DAG labelling sites (120 nm mode) closely matched that separating dystrophin C-terminal sites. This is strong e vidence supporting Ervasti & Campbell's model in which the DAG complex is bound close to the C terminus of dystrophin and in which the DAG c omplexes are separated by approximately the length of the dystrophin r od [7, 12]. In DMD, where there is a 80-90 % reduction in the glycopro tein complex [16], a faint or locally patchy distribution of 43DAG was seen by immunofluorescence. Measurement of nearest-neighbour distance s after immunogold labelling showed that in DMD the 43DAG was more dis persed, which is further evidence that dystrophin is normally involved in anchoring the DAGs in the plasma membrane. This is significant bec ause the potential success of dystrophin gene therapy could depend not only on restoring dystrophin but also on restoring the lost DAGs.