MEMBERS OF THE SYNDECAN FAMILY OF HEPARAN-SULFATE PROTEOGLYCANS ARE EXPRESSED IN DISTINCT CELL-SPECIFIC, TISSUE-SPECIFIC, AND DEVELOPMENT-SPECIFIC PATTERNS

The syndecans are a gene family of four transmembrane heparan sulfate proteoglycans that bind, via their HS chains, diverse components of th e cellular microenvironment. To evaluate the expression of the individ ual syndecans, we prepared cDNA probes to compare mRNA levels in vario us adult mouse tissues and cultured mouse cells representing various e pithelial, fibroblastic, endothelial, and neural cell types and B cell s at various stages of differentiation. We also prepared antibody prob es to assess whether the extracellular domains of the individual synde cans are shed into the conditioned media of cultured cells. Our result s show that all cells and tissues studied, except B-stem cells, expres s at least one syndecan family member; most cells and tissues express multiple syndecans. However, each syndecan family member is expressed selectively in cell-, tissue-, and development-specific patterns. The extracellular domain of all syndecan family members is shed as an inta ct proteoglycan. Thus, most, if not all, cells acquire a distinctive r epertoire of the four syndecan family members as they differentiate, r esulting is selective patterns of expression that likely reflect disti nct functions.