GTPase activator for the Rho-type GTPases. As a GCM1 downstream effector, it is involved in placental development and positively regulates trophoblast cells migration. It regulates cytoskeletal remodeling by controlling the activity of Rho GTPases including RHOA, CDC42 and RAC1. Palmitoylated. Probably palmitoylated by ZDHHC3 and ZDHHC7. SYDE1 knockout results in small fetuses and aberrant phenotypes in the placental-yolk sac barrier, maternal-trophoblast interface, and placental vascularization. Placental abnormalities include cystic dysplasia and apoptosis in the spongiotrophoblast layer, decreased or absent vascularization in the labyrinthine layer, defective barrier between fetal and maternal blood circulation, and reduced invasiveness of primary trophoblast cells.