Based on studies in mice, ROBO1 binds semaphorin receptor NRP1. Other NRP1-binding proteins, such as NRP2, Plexin A1 and Plexin A2, also co-immunoprecipitate with ROBO1, but it is thought that the direct interaction involves ROBO1 and NRP1 only. ROBO1 binds to NRP1 via Ig1and Ig2 domains in the extracellular region of ROBO1. Interaction with ROBO1 may increase the stability of NRP1 and NRP1-associated proteins, or increase their abundance at the plasma membrane. Semaphorins direct the migration of cortical interneurons, and mice deficient in Robo1 function show reduced responsiveness of cortical interneurons to semaphorins (Hernandez-Miranda et al. 2011).