Phosphatidylinositol glycan anchor biosynthesis (PIG) genes, characterized extensively in humans, are involved in the synthesis of glycosylphosphatidylinositols (GPI) and their transfer to proteins to act as a lipid bilayer anchor. GPI is synthesized in the endoplasmic reticulum and is attached to the carboxyl terminus of a protein that has a GPI-attachment signal sequence. (Adapted from FBrf0220328, PMID:11102867 and PMID:19883648).