Glycosyltransferase-like protein LARGE (MIM:603590) is a bifunctional glycosyltransferase with both xylosyltransferase and beta-1,3-glucuronyltransferase activities involved in the biosynthesis of a phosphorylated O-mannosyl trisaccharide, a structure present in alpha-dystroglycan (DAG1; MIM:128239) which plays a key role in skeletal muscle function and regeneration. LARGE contains two substrate-specific GT-domains and belongs to the CAZy glycosyltransferase families GT8 and GT49. Defects in LARGE result in hypoglycosylation of DAG1 and cause several congenital muscular dystrophies (CMDs). Muscular dystrophy-dystroglycanopathy congenital with brain and eye anomalies A6 (MDDGA6; MIM:613154) is associated with brain anomalies, eye malformations, profound mental retardation, and death usually in the first years of life (Clement et al. 2008, Mercuri et al. 2009). Muscular dystrophy-dystroglycanopathy congenital with mental retardation B6 (MDDGB6; MIM:608840) is associated with profound mental retardation, white matter changes and structural brain abnormalities (Longman et al. 2003).