Developmental regulation of proteoglycan synthesis and decorin expression during turkey embryonic skeletal muscle formation.

To delineate the role of proteoglycans in turkey skeletal muscle development, proteoglycan expression was examined in pectoral muscle from 14-, 20-, and 25-d-old embryos. Proteoglycans were separated by DEAE (diethylaminoethyl cellulose) anion exchange and molecular sieve chromatography. Glycosaminoglycan composition was measured by enzyme digestion and nitrous acid deamination. The proteoglycan decorin was analyzed at each of these stages of development for core protein size by polyacrylamide gel electrophoresis and for spatial distribution by immunohistochemistry. Chondroitin sulfate-containing proteoglycans were the predominant proteoglycans found throughout turkey embryonic skeletal muscle development. However, in 20- and 25-d-old pectoral muscle, higher levels of heparan and dermatan sulfate were observed compared with their values at 14 d. Two decorin core protein bands with molecular weights of 45 and 46 kDa were detected. Immunostaining for decorin showed that, as the connective tissue layers developed, decorin was localized in the perimysium and epimysium. These data indicate that turkey embryonic skeletal muscle proteoglycan expression is dynamic and changes from a matrix that is rich in a large chondroitin sulfate proteoglycan to one containing dermatan sulfate, heparan sulfate, and chondroitin sulfate proteoglycans, and suggests the presence of two forms of decorin.