Semaphorin 3 and netrin-1 receptors are expressed by OPCs in vitro. A–D, ON explants from E16.5 OF1 mice were cultured for 48 hr and then immunolabeled with A2B5 mAb (A, C) and either anti-DCC (B) or anti-neuropilin-1 (D) antibodies. Almost all the migrating A2B5⁺ cells (A, C) express DCC (B) and neuropilin-1 (D).E, F, ON explants from E16.5neuropilin-2^+/−-lacZheterozygous mice were cultured for 48 hr and then immunolabeled with A2B5 (E) and anti-β-gal (F) antibodies. Scale bar: A,B, 40 μm; C, D, 25 μm;E, F, 10 μm.