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The Effect of Glypican-1 Glycosaminoglycan Chains on Turkey Myogenic Satellite Cell Proliferation, Differentiation, and Fibroblast Growth Factor 2 Responsiveness¹

X. Zhang^*, C. Liu^*, K. E. Nestor^*, D. C. McFarland and S. G. Velleman^*,2

^* Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691; and Department of Animal and Range Sciences, South Dakota State University, Brookings 57007

² Corresponding author: velleman.1{at}osu.edu

The glypicans are a family of cell-surface heparan sulfate proteoglycans consisting of a core protein covalently attached with glycosaminoglycans (GAG). Only glypican-1 is expressed in skeletal muscle and increases in expression during myoblast differentiation. Previous studies have suggested that glypican-1 influences fibroblast growth factor 2 (FGF2) signaling pathway by its heparan sulfate chains. Fibroblast growth factor 2 is a potent stimulator of muscle cell proliferation and an intense inhibitor of differentiation. To investigate the functional contribution of each GAG chain attachment site, a turkey glypican-1 full length cDNA (1,650 bp, Gen-Bank accession number AY551002) was cloned into the pCMS-EGFP vector and mutated at 2 or all 3 potential GAG attachment sites at Ser₄₈₃, Ser₄₈₅, and Ser₄₈₇ to obtain 1-chain and no-chain mutants, respectively. The unmutated glypican-1, 1-chain, and no-chain mutants, and the pCMS-EGFP vector without an insert were transfected into turkey myogenic satellite cells. The transfected cell cultures were assayed for cell proliferation, differentiation, and FGF2 responsiveness. The overexpression of glypican-1 increased FGF2 responsiveness during proliferation compared with the 1-chain, no-chain mutants, and the pCMS-EGFP vector without an insert, but there was no significant interaction between FGF2 and glypican-1. The overexpression of glypican-1 also increased differentiation but did not affect proliferation when compared with the 1-chain, no-chain mutants, and the pCMS-EGFP vector without an insert. To support the overexpression data, glypican-1 expression was reduced using a small interfering RNA against turkey glypican-1. Inhibition of glypican-1 expression decreased myogenic satellite cell proliferation, differentiation, and FGF2 responsiveness during proliferation. These data indicate that glypican-1 function requires the GAG chain attachment sites for myogenic satellite cell FGF2 responsiveness during proliferation and to affect the process of differentiation.

Key Words: glypican • glycosaminoglycan • satellite cell • muscle • turkey

¹ Salary and research support was provided by state and federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University, and to SGV from the Cooperative State Research, Education, and Extension Service, USDA under Agreement number 2003-35206-13696. Research support to SGV and DCM was provided by the Midwest Poultry Research Consortium and represents collaborative research between SGV and DCM as part of USDA Cooperative State Research, Education, and Extension Service multistate project NC 1131.