DYSTROPHIN AND THE DYSTROPHIN-ASSOCIATED GLYCOPROTEIN, BETA-DYSTROGLYCAN, CO-LOCALIZE IN PHOTORECEPTOR SYNAPTIC COMPLEXES OF THE HUMAN RETINA

Mutations in the gene encoding for dystrophin, a membrane-associated c ytoskeletal protein of muscle and several non-muscle cells, are the ca use of Duchenne muscular dystrophy and Pecker muscular dystrophy. Pati ents suffering from Duchenne muscular dystrophy have recently been sho wn to display an abnormal b-wave of the electroretinogram, suggesting that dystrophin is important for normal retinal transmission. In the r etina, dystrophin has been localized in the outer plexiform layer wher e dystrophin co-localizes with postsynaptic markers of photoreceptor s ynaptic complexes. In the present study we addressed the question of w hether two major dystrophin-associted integral membrane proteins of th e muscular plasma membrane, beta-dystroglycan and adhalin, are also pr esent in photoreceptor synaptic complexes. By double immunostaining an d immunoblotting we show here that beta-dystroglycan is expressed in t he human retina where it co-localizes with dystrophin in photoreceptor synaptic complexes most likely on the postsynaptic side. Adhalin was not detected in the retina. Since beta-dystroglycan is a member of a t ransmembrane supramolecular complex thought to be important for differ entiation of the neuromuscular junction, it is an attractive hypothesi s that dystroglycan (linked to dystrophin) might also play a similar r ole in differentiation of the photoreceptor synapse. A further outcome of this study is that beta-dystroglycan is not only present in the ne uromuscular junction but also associated with a well-defined synaptic complex of the central nervous system. These findings indicate a more general role of this dystrophin-associated membrane protein in synapti c functions. Copyright (C) 1996 IBRO.