GPC3 is a cell surface proteoglycan that bears heparan sulfate. This protein may be involved in the suppression/modulation of growth in the predominantly mesodermal tissues and organs, and may play a role in the modulation of IGF2 interactions with its receptor and thereby modulate its function. Members of the glypican-related integral membrane proteoglycan family contain a core protein anchored to the cytoplasmic membrane via a glycosyl phosphatidylinositol (GPI) linkage. These proteins may play a role in the control of cell division, growth regulation, and tumor predisposition. Deletion mutations in GPC3 are the cause of Simpson-Golabi-Behmel syndrome (SGBS), also known as Simpson dysmorphia syndrome (SDYS). SGBS is a condition characterized by pre- and postnatal overgrowth (gigantism) with visceral and skeletal anomalies.