B4GAT1 and neuromuscular disease caused by qualitative or quantitative defects of alpha-dystroglycan: To date, at least fourteen genes have been recognized as causative of dystroglycanopathies: POMT1, FKTN, POMGNT1, CRPPA, DAG1, GMPPB, POMK, RXYLT1, POMT2, FKRP, LARGE1, B4GAT1, B3GALNT2, and POMGNT2. These genes mostly encode known or putative glycosyltransferases involved in the glycosylation of DAG1.