Initial Characterization of small Proteoglycans Synthesized by Embryonic Chick Leg Muscle-Associated Connective Tissues

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Abstract
Muscle development in the embryonic chick involves the interfacing of two different cell types: myogenic cells forming the contractile network and connective tissue cells which wrap this network into discrete morphologies. Previous reports from this laboratory detailed the characterization of large extracellular matrix proteoglycans synthesized by skeletal muscle. This report describes the initial characterization of small muscle-associated connective tissue proteoglycans synthesized in embryonic chick leg in ovo and by embryonic leg muscle-associated secondary fibroblasts in vitro by CsCl equilibrium density gradient centrifugation. Analysis of the D1 gradient fractions from the in ovo and in vitro material revealed that the proteoglycans were of relatively small size. These molecules eluted from Sepharose CL-2B through a Kav range of 0.6-0.8. Analysis of alkaline borohydride-released glycosaminoglycan chains by Sepharose CL-6B, Sephadex G-25, and thin layer chromatography demonstrated a mixture of three proteoglycan families composed of chondroitin sulfate, dermatan sulfate, and heparan sulfate glycosaminoglycans.