1. The FNIII domain #1 of Robo3 and EGF domains 1-3 of NELL2 are required to form the NELL2-Robo3 receptor-ligand complex, as determined by an alkaline phosphatase binding assay. Deletion of these domains abolishes complex formation. 2. Additional EGF domains of NELL2 beyond domains 1-3 may also contribute to complex formation, as decreased signal intensity was observed upon deletion of domains beyond 1-3. 3. Future work aims to further map the binding interaction between NELL2 and Robo3 by testing additional constructs and determining the specific amino acids required for complex formation using mutational analysis and protein crystallography.