Fig. 7. Neuropilin expression in Ac3^-/- and Ac^+/+ OSN axonal projections. (A) Sagittal section through the olfactory system of a P20 control mouse shows a strong neuropilin 1 expression in OSN axonal bundles (AB) and in the nerve layer (NL) of the olfactory bulb. The cribriform plate is shown with white dots. (B) Similar staining as in A, on an Ac3^-/- P20 mouse. No neuropilin 1 was detected in OSN axonal bundles and projections to the bulb. (C,D) Anti-neuropilin 1 staining (green) of Ac3^+/+ (C) and Ac3^-/- (D) olfactory bulb coronal sections. No neuropilin 1 staining is observed in Ac3^-/- nerve layer or glomeruli. NCAM-expressing OSN projections are in red. (E-J) Coronal sections of wild-type bulbs (P11) showing neuropilin 1 expression (red) in axonal projections corresponding to OSNs expressing the MOR23 odorant receptor (green). (E,H) DAPI staining. Both lateral (E-G) and medial (H-J) glomeruli are immunoreactive. (K-N) M72 (M) and P2 (K) glomeruli are respectively positive and negative for neuropilin 1 expression shown in N and L, respectively. Scale bars: 120 µm. Cp, cribriform plate; D, dorsal; Gl, glomerular layer; L, lateral; M, medial; NL, nerve layer; OB, olfactory bulb; V, ventral.