We previously reported that a defect in O-mannosyl glycan is the primary cause of a group of congenital muscular dystrophies. Based on our pioneering findings, numerous studies have been performed and revealed various structures of O-mannosyl glycans. However, the glycan structure associated with muscular dystrophies remained unclear for a long time. Recently, we described the complete structure of an O-mannosyl glycan containing ribitol-phosphate (RboP), which had not previously been identified as a glycan component in mammals. In addition, its unique biosynthetic pathway was elucidated by identifying the functions of the gene products associated with muscular dystrophies. Here, we review recent findings regarding the mechanisms of O-mannosyl glycan biosynthesis in mammals.
