Heparan sulfate proteoglycans in Drosophila morphogenesis

Heparan sulfate proteoglycans (HSPGs) are involved in a wide variety of molecular recognition events at the cell surface such as growth factor signaling, cell adhesion, viral entry, and tumor metastasis. The functions of these molecules have long been analyzed through biochemical approaches. In recent years, developmental genetics of model organisms including the fruitfly Drosophila melanogaster have revealed that HSPGs have crucial roles in tissue assembly during development. In this review, 1 summarize our knowledge of the roles of one of the Drosophila HSPG core-protein genes, division abnormally delayed (dally), in morphogenesis. Genetic studies have demonstrated that dally is required for signal transduction systems mediated by two growth factors, Decapentaplegic, a member of TGF-β superfamily, and Wingless, a Wnt-related factor. Dally functions in two distinct signaling pathways are tightly controlled in a tissue- or cell type-specific manner. The possibility that the ligand-specificity of Dally is controlled by modification of HS fine structures will be discussed.