GGT1 and schizophrenia: Bioinformatic assessment of multiple genetic datasets has identified differential gene expression of prenylation-associated enzymes in schizophrenia that varies by brain region and cortical layer.118 Three enzyme complexes catalyze protein prenylation: farnesyltransferase (FT), geranylgeranyltransferase I (GGT-1), and Rab geranylgeranyltransferase (RGGT; also called geranylgeranyltransferase II).