Participates in O-mannosyl glycosylation by catalyzing the addition of N-acetylglucosamine to O-linked mannose on glycoproteins (PubMed:11709191, PubMed:27493216, PubMed:28512129). Catalyzes the synthesis of the GlcNAc(beta1-2)Man(alpha1-)O-Ser/Thr moiety on alpha-dystroglycan and other O-mannosylated proteins, providing the necessary basis for the addition of further carbohydrate moieties (PubMed:11709191, PubMed:27493216). Is specific for alpha linked terminal mannose and does not have MGAT3,

Golgi apparatus membrane

Muscular dystrophy-dystroglycanopathy congenital with brain and eye anomalies A3

An autosomal recessive disorder characterized by congenital muscular dystrophy, ocular abnormalities, cobblestone lissencephaly, and cerebellar and pontine hypoplasia. Patients present severe congenital myopia, congenital glaucoma, pallor of the optic disks, retinal hypoplasia, intellectual disability, hydrocephalus, abnormal electroencephalograms, generalized muscle weakness and myoclonic jerks. Included diseases are the more severe Walker-Warburg syndrome and the slightly less severe muscle-eye-brain disease.