Mouse SDC4 is a ubiquitous transmembrane proteoglycan which belongs to the syndecan proteoglycan family. SDC4 is a cell surface proteoglycan that bears heparan sulfate. The four vertebrate syndecans, Syndecan-1 through -4, have similar short cytoplasmic domains and extracellular portions that diverge, except for HS attachment sites. Structurally diverse side chains add considerably to the size of the core proteins and serve as binding sites for growth factors, cytokines, and extracellular matrix proteins. Syndecans are present as homodimers or multimers, and are often expressed in developmental and cell type-specific patterns. It is expressed highly in liver, kidney and lung. SDC4 localizes to the focal adhesions of adherent cells and binds to a range of extracellular ligands, including growth factors and extracellular-matrix proteins. Through its extracellular domain, syndecan-4 cooperates with adhesion molecules and binds matrix components relevant for cell migration. As a heparan sulfate proteoglycan, SDC4 works as a coreceptor for various growth factors. Syn4 deficiency limits neointimal formation after vascular injury by regulating vascular smooth muscle cells (VSMCs) proliferation and vascular progenitor cells (VPCs) mobilization. SDC4 have an array of functions including regulating cell growth, differentiation, and adhesion.