title: Glycomic analyses of mouse models of congenital muscular dystrophy.
abstract: Dystroglycanopathies are a subset of congenital muscular dystrophies wherein α-dystroglycan (α-DG) is hypoglycosylated. α-DG is an extensively O-glycosylated extracellular matrix-binding protein and a key component of the dystrophin-glycoprotein complex. Previous studies have shown α-DG to be post-translationally modified by both O-GalNAc- and O-mannose-initiated glycan structures. Mutations in defined or putative glycosyltransferase genes involved in O-mannosylation are associated with a loss of ligand-binding activity of α-DG and are causal for various forms of congenital muscular dystrophy. In this study, we sought to perform glycomic analysis on brain O-linked glycan structures released from proteins of three different knock-out mouse models associated with O-mannosylation (POMGnT1, LARGE (Myd), and DAG1(-/-)). Using mass spectrometry approaches, we were able to identify nine O-mannose-initiated and 25 O-GalNAc-initiated glycan structures in wild-type littermate control mouse brains. Through our analysis, we were able to confirm that POMGnT1 is essential for the extension of all observed O-mannose glycan structures with β1,2-linked GlcNAc. Loss of LARGE expression in the Myd mouse had no observable effect on the O-mannose-initiated glycan structures characterized here. Interestingly, we also determined that similar amounts of O-mannose-initiated glycan structures are present on brain proteins from α-DG-lacking mice (DAG1) compared with wild-type mice, indicating that there must be additional proteins that are O-mannosylated in the mammalian brain. Our findings illustrate that classical β1,2-elongation and β1,6-GlcNAc branching of O-mannose glycan structures are dependent upon the POMGnT1 enzyme and that O-mannosylation is not limited solely to α-DG in the brain.
authors: Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602-4712, USA.
authors: Stephanie H
authors: SH
authors: Stalnaker
authors: Kazuhiro
authors: K
authors: Aoki
authors: Jae-Min
authors: JM
authors: Lim
authors: Mindy
authors: M
authors: Porterfield
authors: Mian
authors: M
authors: Liu
authors: Jakob S
authors: JS
authors: Satz
authors: Sean
authors: S
authors: Buskirk
authors: Yufang
authors: Y
authors: Xiong
authors: Peng
authors: P
authors: Zhang
authors: Kevin P
authors: KP
authors: Campbell
authors: Huaiyu
authors: H
authors: Hu
authors: David
authors: D
authors: Live
authors: Michael
authors: M
authors: Tiemeyer
authors: Lance
authors: L
authors: Wells
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002241:Carbohydrates / Q000737:chemistry; D004195:Disease Models, Animal; D049030:Dystroglycans / Q000737:chemistry; D005700:Galactosyltransferases / Q000737:chemistry; D054794:Glycomics / Q000379:methods*; D006031:Glycosylation; D008358:Mannose / Q000737:chemistry; D051379:Mice; D018345:Mice, Knockout; D009136:Muscular Dystrophies / Q000151:congenital / Q000378:metabolism*; D009154:Mutation; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics*; D011134:Polysaccharides / Q000737:chemistry
chemical_list: D002241:Carbohydrates; D011134:Polysaccharides; D049030:Dystroglycans; D005700:Galactosyltransferases; D017351:N-Acetylglucosaminyltransferases; C443106:protein O-mannose beta-1,2-N-acetylglucosaminyltransferase; D008358:Mannose