Recently, reports in the literature have connected mutations in B3GNT1 with congenital muscular dystrophies (Buysse et al., 2013; Czeschik et al., 2013; Shaheen et al., 2013) and specifically to the defective glycosylation of α-dystroglycan (Jae et al., 2013) even though no O-mannose glycan structures containing a β3-GlcNAc have yet to be elucidated (Praissman and Wells, 2014). Here, DAG1 is linked to muscular dystrophy.