Npn-2-expressing cranial nerves are defective in sema3F null mice. a-d, Whole-mount immunostaining using neurofilament antibodies (2H3) of E10.5 and E11.5 wild-type embryos (a, c, respectively) and sema3F null embryos (b, d, respectively). The oculomotor nerve is severely defasciculated (arrow in b), and only a few trochlear axons exit the dorsal midline and project into the periphery in sema3F null mice (arrow in d). III, Oculomotor nerve; IV, trochlear nerve. For E10.5, n = 5(+/+), 9(+/-), and 7 (-/-). For E11.5, n = 4(+/+), 3(+/-), and 3 (-/-). Scale bar, 100 μm.