SRGAP bound to ROBO's cytoplasmic tail increases the intrinsic GTPase activity of CDC42, converting the GTP-bound form of CDC42 into its GDP-bound form, therefore inactivating CDC42. Inactivation of CDC42 leads to a reduction in the activation of the Neuronal Wiskott-Aldrich Syndrome protein (NWASP), thus decreasing the level of the active Arp2/3 complex. Because active Arp2/3 promotes actin polymerization, the reduction of active CDC42 eventually decreases actin polymerization. SLIT regulates SRGAP interaction with ROBO1 and CDC42, increasing SRGAP binding to CDC42 (Wong et al. 2001, Li et al. 2006).