The glycosyltransferase loci MGAT5 (encoding alpha-1,6-mannosylglycoprotein 6-beta-N-acetylglucosaminyltransferase) and MGAT1 have been implicated in the pathogenesis of type 1 diabetes through N-glycan branching and its impact on T cell activation [14, 22]. The gene discussed is MGAT5; the disease is type 1 diabetes mellitus.