G.P.321: A new monoclonal antibody against human alpha-dystroglycan has potential diagnostic applications

We have generated novel monoclonal antibodies (mAbs) against alpha-dystroglycan to immunolabel the sarcolemma in human muscle biopsies. For one of these, DAG-6F4, a seven amino-acid epitope, PNQRPEL, was identified using phage-displayed peptides and is located immediately after the highly-glycosylated mucin domain of alpha-dystroglycan. On western blots of recombinant alpha-dystroglycan, epitope accessibility was reduced, but not entirely prevented, by glycosylation. DAG-6F4 immunolabelling was markedly reduced in muscle biopsies from Duchenne muscular dystrophy patients consistent with a disruption in the dystroglycan complex. In a range of dystroglycanopathy patients with reduced/altered glycosylation, staining by DAG-6F4 was generally less reduced than staining by IIH6 (an antibody commonly used to identify glycosylated alpha-dystroglycan), though the extent of the differences between the two antibodies varied between different patients, some biopsies showing reductions in core protein as well as its glycosylation. A second mAb, DAG-3H9, gave similar results, but recognised a different epitope, GDRAP, closer to the C-terminus. There are currently few antibodies available against core alpha-dystroglycan, so DAG-6F4 represents a useful addition to the antibody repertoire for evaluating the dystroglycan complex in neuromuscular disorders.