PathwayStep6207 PathwayStep6208 Regulation of Commissural axon pathfinding by Slit and Robo Authored: Garapati, P V, 2008-09-05 06:02:05 Commissural axons project to the floor plate, attracted by the interaction of their DCC receptors with netrin1 produced by floor plate cells. The axons are insensitive to the repulsive action of slit despite expression of repulsive slit receptors (Robo1 and Robo2) because they also express Robo3, a slit receptor that suppresses the activity of Robo1 and Robo2. Once an axon enters the floor plate, however, it must be efficiently expelled on the contralateral side. Based on studies in Xenopus neurons and by yeast two hybrid screens it is observed that the attractive response of the axons to netrins is silenced by activation of Robo. Slit bound Robo binds to DCC, preventing it from transducing an attractive response to netrin. A switch from attraction to repulsion allows commissural axons to enter and then leave the CNS midline. Upon crossing the midline, commissural axons downregulate expression of Robo3 and increases expression of Robo1/Robo2. Edited: Garapati, P V, 2008-09-05 06:02:05 Pubmed17029581 Reactome Database ID Release 43428542 Reactome, http://www.reactome.org ReactomeREACT_19376 Reviewed: Kidd, T, 2009-08-18 Robo3 antagonizes Robo1/Robo2 to allow floor plate crossing Proteolytic processing of Slit