The extracellular and JM domains of EphB1 are required for maximum efficiency in rerouting RGC axons ipsilaterally. A, Graph displaying the percentages of GFP+ ipsilateral (Ipsi) projections for GFP, EphB1, EphB2, EphB1ΔSAM, and the chimeric EphB1–EphB2 receptor constructs. EphB1 regions are labeled blue, and EphB2 regions are labeled red. ***Labeled columns are statistically identical, with all of these mutants having significantly higher GFP+ ipsilateral projections compared with GFP alone (p < 0.0001) and compared with labeled mutants (*p < 0.05). [One exception is WT EphB1, which had a significantly higher percentage of GFP+ uncrossed projections compared with EphB1-B2T300 and EphB1-B2T6 mutants (p < 0.05)]. *Labeled mutants are statistically identical, with all of these columns having significantly higher GFP+ ipsilateral projections compared with GFP alone (p < 0.05, except for EphB2-B1T6, which is not significantly different from GFP) and a significantly lower GFP+ ipsilateral projections compared with labeled mutants (***p < 0.05). Contra, Contralateral. Data represent mean ± SEM. ANOVA: F(9,121) = 13.59, p < 0.0001. Scale bars, 100 μm. B, Summary of EphB1 and EphB2 chimeric constructs and their ability to convert crossed RGCs to an uncrossed fate. Both the JM region and a portion of the extracellular domain (green domains on bottom bar) are required for maximal efficiency in giving rise to ipsilateral (Ipsi) projections.