Atypical OSN axon innervation of MOR23 glomerulus in BACE1-/- OBs. Coronal sections of OBs from 60 day-old MOR23-GFP; BACE1+/+ (A-D) and MOR23-GFP; BACE1-/- (E-H) mice were immunostained with anti-BACE1 antibody and imaged for BACE1 (red; A, E), GFP (green; B, F), and DAPI for periglomerular cell nuclei (blue; C, G) by laser scanning confocal microscopy. Three-color image merges are shown in (D, H). Robust GFP fluorescence is observed in OSN axons and terminals in MOR23 glomeruli (B, F). Note that largely individual BACE1-/- OSN axons enter the MOR23 glomerulus from multiple directions and orientations (F, H), while most BACE1+/+ OSN axons penetrate the MOR23 glomerulus as a bundle perpendicular to the glomerular layer (B, D), suggesting that BACE1 deficiency results in abnormal glomerular innervation. Scale bar in (H) = 100 μm.