Fig. 4. Known and putative glycosyltransferases involved in the O-glycosylation pathway of -dystroglycan. The function of fukutin and FKRP is still unknown. Although it has not been excluded that LARGE and LARGE2 are involved in O-mannosylation of -dystroglycan, it is very likely that overexpression of these putative enzymes stimulates the synthesis of novel and still unknown O-linked sugar chains on the mucin domain of -dystroglycan by direct binding of LARGE to the N-terminal and the first half of the mucin domain.