Roundabout homologue 1 (Robo1) and Roundabout homologue 2 (Robo2) are receptors which cooperate to mediate the function of Slit proteins, used in guiding major forebrain projections during neuronal development. Robo1 is an axon guidance receptor and cell adhesion receptor, necessary in stimulating neurite outgrowths from Robo-positive neurons. Deficiencies in Robo1 can cause prominent axon pathfinding errors during neuronal cell migration.
Robo1 is activated by the Slit family of proteins, this results in a repulsive effect on glioma cell guidance in the developing brain. In bilaterally symmetrical nervous systems seen in vertebrae, the nervous system midline structures establish the partition between the two halves; Robo1 is essential in the crossing of the central nervous system midline, appearing as the controlling factor in midline crossing of axons.
Robo1 and Robo2 are used in separate, specialised processes in post midline crossing axons. Robo1 is needed to prevent axons from stalling immediately post crossing, whereas Robo2 is required for axons to project away from the floor plate and into the lateral funiculus.