Recently, using mass spectrometry and nuclear magnetic resonance �Cbased structural analyses, the group of Kevin Campbell identified a phosphorylated O-mannosyl glycan on recombinant a-DG, which was required for laminin binding. This phosphorylation occurs on the O-linked mannose of a-DG. Further work from the Lance Wells�� laboratory demonstrated that a-DG is mannosylated at 9 residues, while GalNAcylation occurs at 14 sites. LARGE is a putative glycosyltransferase mutated in the myodystrophy mouse and in patients affected by MDC1D, one of the dystroglycanopathy variants associated with skeletal muscle and structural brain involvement. Sequence analysis predicts LARGE to contain two catalytic domains. The first domain is related to MG132 Proteasome inhibitor bacterial aglycosyltransferases, while the second is most closely related to human b-1,3-Nacetylglucosaminyltransferase, required for synthesis of the poly-N-acetyllactosamine backbone n found on N- and O-glycans. Although neither of these structures is present on a-DG, there is strong evidence that LARGE plays a pivotal role in the functional glycosylation of a- DG. Firstly, the N-terminal domain of a-DG interacts directly with LARGE and this association is a requirement for physiological glycosylation. Secondly, the forced Fingolimod Src-bcr-Abl inhibitor overexpression of LARGE in mouse skeletal muscle, as well as cultured human and mouse cell lines, results in increased expression of functionally glycosylated a-DG and a corresponding increase in its binding capacity for laminin and other ligands. Moreover, the overexpression of LARGE generates highly glycosylated a-DG in cell lines derived from patients with a dystroglycanopathy, irrespective of the underlying gene defect. While the precise nature of the LARGE induced glycosylation remains undetermined, it has been suggested that LARGE requires mannosylated a-DG to exert its action. Furthermore LARGE gene transfer experiments achieved a-DG hyperglycosylation in animal models of fukutin and PomGnt1 related muscular dystrophies, thus LARGE overexpression can presumably activate alternative pathways resulting in functional a-DG glycosylation in these models. None of the other enzymes responsible for dystroglycanopathies has a similar effect; however we have previously demonstrated that the overexpression of the LARGE paralog GYLTL1B is equally capable of hyperglycosylating a-DG in cultured cells ; mutations in this gene have not yet been associated with a human pathology. The presence of alternative pathways of a-DG glycosylation opens new avenues for the development of therapies in dystroglycanopathies.