CHARACTERIZATION OF CHICKEN SYNDECAN-3 AS A HEPARAN-SULFATE PROTEOGLYCAN AND ITS EXPRESSION DURING EMBRYOGENESIS

Syndecan-3 is one of four identified members of a family of transmembr ane proteoglycans (the syndecans) that possess highly similar cytoplas mic and transmembrane domains and may function as extracellular matrix receptors and/or low affinity receptors for signaling molecules such as FGF. We previously reported the cloning of a partial cDNA for chick en syndecan-3. Here we report the isolation of a syndecan-3 cDNA conta ining additional 5' sequence which includes a potential methionine sta rt codon and putative signal sequence. In vitro translation of syndeca n-3 cDNA in the presence and absence of microsomes suggests that the p utative signal sequence is functional, suggesting that the cDNA may en compass the full coding sequence. We also identify syndecan-3 as a hep aran sulfate proteoglycan and report its expression pattern during chi cken embryogenesis using polyclonal antibodies raised against a recomb inant fusion protein. We detect abundant syndecan-3 expression in the developing brain and neural tube, including a striking expression in t he floor plate of the neural tube. During limb development, syndecan-3 is expressed in the distal mesenchymal cells of the limb bud which ar e undergoing outgrowth in response to the apical ectodermal ridge. Syn decan-3 is also transiently expressed during the formation of the prec artilage condensations of the skeletal elements of the limb and subseq uently in association with the differentiating osteoblasts of the peri osteum. Expression is also observed in several areas of tissue interac tions including the developing lens, otic vesicle, genital ridge, scle rotome, and feather buds. (C) 1995 Academic Press, Inc.