ARHGAP20 is a potent GTPase-activating protein (GAP) and convert Rho-type GTPases into an inactive GDP-bound state. It contains a pleckstrin homology (PH) domain, a Ras-associating domain, a Rho-GAP domain and two Annexin-like (ANXL) repeats. ARHGAP20 is a direct downstream target of Rap1 in the neurite outgrowth while it's over expression leads to inactivation of Rho for promoting the neurite outgrowth in a Rap1-dependent manner. ARHGAP20 is a tumor suppressor gene and is inactivated by deletion in breast cancer and also by chromosomal translocation in B-cell chronic lymphocytic leukemia. Reports suggest that it may take part in rearrangements of the cytoskeleton and cell signaling events that occur during spermatogenesis. It is expressed predominantly in human brain, liver, ovary and spinal cord while low expression is found in lymph nodes and fetal liver.