alpha-dystroglycan isoforms are differentially distributed in adult rat retina

alpha-Dystroglycan (alpha -DG) is a laminin/agrin receptor expressed in ske letal muscle as well as in nervous system and other tissues. Glycosylation of the core protein of alpha-DG; is extensive, variable from tissue to tiss ue, and functionally relevant. To address differential glycosylation of alp ha-DG in the retina, we have investigated the distribution of this protein using two different antibodies: 1B7 directed against the core protein of al pha-dystroglycan, and IIH6 directed against a carbohydrate moiety (Ervasti and Campbell [1993] J Cell Biol 122:809-823). Monoclonal antibody 1B7 recog nizes a broader band than IIH6, which seems to recognize only a subset of a lpha-DG forms in retina. These data reflect the existence of differentially glycosylated isoforms of alpha-DG. Monoclonal antibody 1B7 shows an extens ive staining for alpha-DG in the inner limiting membrane as well as in the ganglion cell and inner plexiform layers labeling Muller cell processes, wh ereas monoclonal antibody IIH6 staining is restricted to the inner limiting membrane and blood vessels. Our data indicate that there are distinct isof orms of alpha-DG that are localized in apposition to basal lamina in the in ner limiting membrane and blood vessels or within the parenchyma of the ret ina along Muller glia. Both isoforms are expressed in a Muller cell line in culture and coimmunoprecipitate with beta-dystroglycan. These data suggest that DGs may participate in organizing synapses and basement membrane asse mbly in the retina. (C) 2000 Wiley-Liss, Inc.