Multiple distinct O-Mannosylation pathways in eukaryotes

•Multiple O-Man glycosylation pathways exist in eukaryotes.•Yeast has a unique nucleocytosolic O-Man glycosylation pathway in lieu of the common eukaryotic O-GlcNAc nucleocytosolic pathway.•Cadherin and plexin superfamilies of proteins are major carriers of O-Man glycans.•Congenital disorders of glycosylation are caused by deficiencies in TMTCs.