A possible explanation is the occurrence of axon stalling within the floor plate. Commissural axons stall within the floor plate of the Robo1 KO, which means that fewer axons reach the ventral funiculus. However, we have shown that axon stalling does not occur in the floor-plate of the srGAP3 KO therefore axons extend into the ventral funiculus. If srGAP3 is involved in Robo1 mediated repulsion from the midline, then our data suggests that it is likely to be after commissural axons have left the floor-plate. As it has been shown that Robo1 and Robo2 are homophilic adhesion molecules that can interact with each other, it is possible that srGAP3 is not required for the Robo-mediated response to Slit but rather as a mediator of Robo/Robo interactions. Therefore, our observation that Robo1-positive axons run more medially in srGAP3 KO spinal cords compared to WT, might not result from a loss of responsiveness to Slit but rather indicate a difference in axonal fasciculation between Robo1 and Robo2-positive axons. In other words, expression of Robo2 might keep axons from extending medially but some axons expressing only Robo1 might not be repelled sufficiently by Slit but also require fasciculation with Robo2-positive axons for their lateral position. Thus, these axons will run more medially in the absence of Robo2 or in the absence of srGAP3. In conclusion, we have shown that srGAP3 can bind to the Slit receptors Robo1 and Robo2. We have also shown that srGAP3 co-localises with both Robo receptors in the post-crossing longitudinal axons tracts of the spinal cord. Unlike what has been reported in the Slit and Robo mutant mice, we observed no stalling of commissural axons within the floor plate. Instead, we observed a thickening of the ventral funiculus and a reduction of the lateral funiculus, which corresponds to the phenotype described for the Robo2 KO. However, the axons within the enlarged ventral funiculus were Robo1 but not Robo2 positive. We suggest that srGAP3 is involved in the lateral OAC-2 positioning of commissural axons within the ventrolateral funiculus, possibly downstream of Robo1. Monoclonal antibodies represent an important class of pharmaceutical bioOrg 37684 technology products and important research tools in chemistry and in life sciences. The advent of phage display library technology allowed the facile isolation of fully human antibodies from large combinatorial repertoires. While libraries were initially created starting from antibody genes isolated from natural sources, there has been a growing interest in the construction of rationally designed synthetic antibody libraries, in which individual library members incorporate structural features which are beneficial for practical applications.