Figure 3.

Robo-2 is required for the targeting of MOR174–9-expressing OSN axons in the OB. A–J, Coronal sections of OBs isolated from control (A, D, G, H) and robo-2^lox/lox;OMP-Cre; MOR174–9-tau-GFP (B, C, E, F, I, J) mice stained with NQO-1 and GFP antibodies (A–J). NQO-1 antibodies stain axons of OSNs innervating the dorsal region of the OB. On the lateral side of the OB, a GFP-positive glomerulus is consistently observed in the dorsal region of the OB (A–C) and a second GFP-positive glomerulus is observed in approximately half of the OBs analyzed (14/28 controls and 18/25 robo-2^lox/lox; OMP-Cre) (D–F). In addition, a third glomerulus was observed more ventrally in two OBs from control mice and in six OBs from robo-2^lox/lox; OMP-Cre mice (shown in yellow on the scatter plot in K). On the medial side of the OB, all OBs analyzed contained at least one GFP-positive glomerulus (G, H) and the majority of OBs analyzed (19/27 for controls and 19/25 for robo-2^lox/lox; OMP-Cre mice) contained two GFP-positive glomeruli (H, J). Furthermore, a few OBs analyzed contained an additional GFP-positive glomerulus (2/28 controls and 6/27 robo-2^lox/lox; OMP-Cre). K, L, The relative positions of GFP-positive glomeruli in the dorsoventral axis of the OB on the lateral and medial sides of the OB were assessed and represented on scatter plots (K, L). Parameters are shown as mean ± SEM. The mean location of glomeruli innervated by MOR174–9-expressing axons on both the lateral and medial sides of the OB is shifted ventrally in robo-2^lox/lox; OMP-Cre. Note that the additional glomeruli observed in some bulbs (represented in yellow) were not included in the calculation of the mean. Sections containing glomeruli located close to the mean angle are shown in A, B, D, E, G–J. In C and F, sections with a more severe ventral shift in the location of the glomeruli are shown. ***p < 0.001. **p < 0.01. D, Dorsal; V, ventral; L, lateral; M, medial. Scale bar, 250 μm.