Cell surface proteoglycan that may bear both heparan sulfate and chondroitin sulfate. The multiple functional domains provide potential sites for mediating the adhesive cell-matrix interactions and cytoskeletal reorganization involved in limb chondrogenesis. Interaction with other matrix ligands as well as phosphorylation and shedding of the ectodomain might be involved in cell shape changes that occur during chondrogenesis. Furthermore, shedding of the ectodomain might break the adhesive interactions that promoted condensation, thus facilitating the deposition of cartilage matrix molecules. Proximal chondrogenic central core of embryonic limb buds where cartilage differentiation is being initiated. Expressed in high amounts at the onset of limb cartilage differentiation. O-glycosylated within the Thr/Ser-rich region which could interact with lectin domains on other molecules. Belongs to the syndecan proteoglycan family.