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LARGE glycans on dystroglycan function as a tunable matrix scaffold to prevent dystrophy
Journal article   Peer reviewed

LARGE glycans on dystroglycan function as a tunable matrix scaffold to prevent dystrophy

Matthew M Goddeeris, Biming Wu, David Venzke, Takako Yoshida-Moriguchi, Fumiaki Saito, Kiichiro Matsumura, Steven A Moore and Kevin P Campbell
Nature (London), Vol.503(7474), pp.136-140
11/07/2013
DOI: 10.1038/nature12605
PMCID: PMC3891507
PMID: 24132234

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Abstract

The dense glycan coat that surrounds every cell is essential for cellular development and physiological function 1 , and it is becoming appreciated that its composition is highly dynamic. Post-translational addition of the polysaccharide repeating unit [-3-xylose-α1,3-glucuronic acid-β1-] n by like-acetylglucosaminyltransferase (LARGE) is required for the glycoprotein dystroglycan to function as a receptor for proteins in the extracellular matrix 2 , 3 . Reductions in the amount of [-3-xylose-α1,3-glucuronic acid-β1-] n (hereafter referred to as LARGE-glycan) on dystroglycan result in heterogeneous forms of muscular dystrophy 4 . However, neither patient nor mouse studies has revealed a clear correlation between glycosylation status and phenotype 5 , 6 . This disparity can be attributed to our lack of knowledge of the cellular function of the LARGE-glycan repeat. Here we show that coordinated upregulation of Large and dystroglycan in differentiating mouse muscle facilitates rapid extension of LARGE-glycan repeat chains. Using synthesized LARGE-glycan repeats we show a direct correlation between LARGE-glycan extension and its binding capacity for extracellular matrix ligands. Blocking Large upregulation during muscle regeneration results in the synthesis of dystroglycan with minimal LARGE-glycan repeats in association with a less compact basement membrane, immature neuromuscular junctions and dysfunctional muscle predisposed to dystrophy. This was consistent with the finding that patients with increased clinical severity of disease have fewer LARGE-glycan repeats. Our results reveal that the LARGE-glycan of dystroglycan serves as a tunable extracellular matrix protein scaffold, the extension of which is required for normal skeletal muscle function.

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