The protein encoded by this gene is a Rho-like GTPase that switches between the active (GTP-bound) state and inactive (GDP-bound) state to regulate CDC42 and other genes. Defects in this gene are a cause of startle disease with epilepsy (STHEE), also known as hyperekplexia with epilepsy. Three transcript variants encoding different isoforms have been found for this gene.[provided by RefSeq, Mar 2010].