This gene encodes a protein that contains Dbl (DH) and pleckstrin (PH) homology domains and is similar to the Rho family of small GTP-binding proteins. The encoded protein specifically binds to the Rho family GTPase Cdc42Hs and can stimulate the GDP-GTP exchange of the isoprenylated form of Cdc42Hs. It also stimulates the mitogen activated protein kinase cascade leading to c-Jun kinase SAPK/JNK1 activation. Defects in this gene are the cause of faciogenital dysplasia and X-linked mental retardation, syndromatic 16.,FGD1,AAS,FGDY,MRXS16,ZFYVE3,FYVE,Signal Transduction,G protein signaling,G-Protein-Coupled Receptors(GPCR),Cell Biology & Developmental Biology,Cytoskeleton,Microfilaments,FGD1