Fig. 2. Robo1 and Robo2 expression in the forebrain. Robo1 and Robo2 expression was examined using antibodies specific for each receptor. (A-D) In rostral sections, Robo1 protein was highly expressed on callosal axons at E17 (A, coronal view; arrow in C; C is a higher power view of A), whereas Robo2 staining is very faint (B, coronal view at E17; arrow in D; D is a higher power view of B). (E,F) In more caudal regions, Robo1 is expressed on the hippocampal commissure (HC) and on the corpus callosum (CC) (E, horizontal view at E17); Robo2 is expressed on the nigrostriatal pathway (NSP), the internal capsule (IC) and the optic tract (OT) (F, coronal view at E17). Scale bar in A: 200 µm for A,B,E,F; in C, 100 µm for C,D.