Vilse/CrossGAP (CrGAP), a conserved Rac-specific GAP in Drosophila, is involved in Robo mediated repulsion. CrGAP directly interacts with Robo, both biochemically and genetically. The biochemical interaction is mediated by the WW domains in CrGAP and the CC2 motif of Robo.
The human homologue of Vilse/CrGAP, ARHGAP39 (also known as KIAA1688), was identified. ARHGAP39 shares 54.4% sequence identity with Drosophila CrGAP and is referred to as human Vilse/CrGAP protein (Lundstrom et al. 2004, Hu et al. 2005).