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. 2011 May 25;31(21):7920–7926. doi: 10.1523/JNEUROSCI.2460-10.2011

Figure 1.

Figure 1.

Robo-2 is expressed in OSNs innervating the dorsal region of the olfactory bulb and is required for the targeting of axons from subsets of OSNs. A, Schematic representation of the pattern of innervation of the olfactory bulb by OSNs. OSNs located in the dorsal region of the OE innervate the dorsal part of the OB. In the dorsal OE, OSNs expressing class I ORs, such as MOR1–3 or S50, send their axons to the DI region of the OB, while OSNs expressing class II ORs, such as MOR174–9 or M72, innervate the DII region of the OB. B, C, Fluorescent in situ hybridization of coronal sections of olfactory epithelium isolated from E18 embryos with cRNA probes specific for robo-2 (B, B″, C, C″), MOR1–3 (B′, B″), and MOR174–9 (C′, C″). OSNs expressing the class I OR, MOR1–3, or the class II OR, MOR174–9, are located in the dorsomedial region of the OE and express robo-2. Scale bar, 100 μm. D–I, Whole-mount X-gal-stained or fluorescent views of MOR1–3-expressing (D, E) and S50-expressing (F–I) OSN projections in adult control (D, F, H) and robo-2lox/lox; OMP-Cre (E, G, I) mice. MOR1–3-expressing OSN axons target to one or two glomeruli in the most dorsal region of the OB (D, E) (arrowheads). S50-expressing axons innervate glomeruli in the dorsal (F, G) and medial (H, I) regions of the OB (arrowheads). The location of MOR1–3 and S50-positive glomeruli appear unchanged in robo-2lox/lox; OMP-Cre mice (E, G, I). n = 4 controls and 4 robo-2lox/lox; OMP-Cre. Scale bars, 500 μm. D, Dorsal; V, ventral; L, lateral; M, medial. J–O, Whole-mount X-gal-stained or fluorescent views of MOR174–9- (J–M) or M72- (N, O) expressing OSN projections in adult control (J, L, N) and robo-2lox/lox; OMP-Cre (K, M, O) mice. MOR174–9-expressing OSN axons innervate one or two glomeruli on the lateral (J, K) and medial (L, M) sides of the OB (arrowheads). The location of some of these glomeruli appears shifted toward the ventral part of the OB in most robo-2lox/lox; OMP-Cre mice analyzed when compared to controls. M72-expressing OSN axons innervate one glomerulus on the dorsal (N) and medial (not shown) regions of the OB (arrowheads). In robo-2lox/lox; OMP-Cre mice, two glomeruli are consistently observed in the dorsal region of the OB (O). High-magnification views of M72-positive glomeruli are shown in N′, N″, O′, and O″. n = 5 control; MOR174–9-GFP, 3 control; M72-tau-lacZ, 5 robo-2lox/lox; OMP-Cre; MOR174–9-GFP, and 3 robo-2lox/lox; OMP-Cre; M72-tau-lacZ mice. The dorsal limit of the OB is indicated by a white dashed line in J–M. Scale bars, 500 μm. D, Dorsal; V, ventral; L, lateral; M, medial.