ROBO1, a 170-200 kDa protein, is a member of the ROBO family of guidance molecules. It functions as a repulsive molecule that prevents axons from crossing the midline in the developing central nervous system （CNS）. ROBO1 regulates the responsiveness to Netrin-1 and Semaphorin 3A and 3F by forming cis complexes with Neuropilin-1, Neuropilin-2, Plexin A1, DCC, and FLRT3.
Additionally, ROBO1 is expressed in developing ductal epithelia, where its binding to Slit2 limits branching morphogenesis. The interaction between ROBO1 and Slit2 can also suppress tumorigenesis, enhance VEGF-induced angiogenesis, and enhance CXCL12-induced T cell chemotaxis by associating with CXCR4.