The function of POMGNT1 (protein O-linked mannose N-acetylglucosaminyltransferase 1 (beta 1,2-), ENSG00000085998) is as follows. 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, MGAT4, MGAT5, MGAT7 or MGAT8 activity. {ECO:0000269|PubMed:11709191, ECO:0000269|PubMed:11742540, ECO:0000269|PubMed:26908613, ECO:0000269|PubMed:27391550, ECO:0000269|PubMed:27493216, ECO:0000269|PubMed:28512129}.