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. 2007 Aug 22;27(34):9094–9104. doi: 10.1523/JNEUROSCI.2217-07.2007

Figure 7.

Figure 7.

Mistargeted axons of NQO-1-expressing olfactory sensory neurons innervate glomeruli in the ventral region of the olfactory bulb in slit and robo-2 mutant mice. Coronal sections at similar rostrocaudal levels of olfactory bulbs isolated from 8- to 12-week-old wild-type (A, E, I), slit-1−/− (B, F, J, M–O), slit-1−/−;slit-3−/− (C, G, K), and robo-2c/c;syn-1Cre/+ (D, H, L) mice stained with anti-NQO-1 (A–D, I–L, M–O), anti-OCAM (E–H, I–L, M, N), anti-SV2 (O), and Hoechst (A–O). In wild-type mice, NQO-1-expressing axons innervate glomeruli restricted to the dorsomedial region of the olfactory bulb (A, I), and OCAM-expressing axons innervate glomeruli in the ventrolateral region of the olfactory bulb (E, I). In slit-1−/− (B, J), slit-1−/−;slit-3−/− (C, K), and robo-2c/c;syn-1Cre/+ (D, L) mice, a subset of NQO-1-expressing axons are mistargeted to glomeruli in the ventral region of the olfactory bulb (arrows). NQO-1-expressing axons that target ectopically in the ventral region of the OB in slit-1−/− mice form both homogenous (arrowheads) and heterogenous (arrows) glomeruli (M, N) and are positive for the presynaptic marker SV2, suggesting that they form synapses (arrowheads) (O). n = 10 wild type, n = 14 slit-1−/−, n = 9 slit-1−/−;slit-3−/−, and n = 4 robo-2c/c;syn-1Cre/+. Scale bars: A–L, 250 μm; M–O, 140 μm. P–R, Scatter plots showing the mapping of the positions of NQO-1-positive glomeruli in the olfactory bulb of an adult wild-type (P), slit-1−/− (Q), and robo-2c/c;syn-1Cre/+ (R) mouse. The relative positions of glomeruli containing NQO-1-positive axons were assessed in olfactory bulb sections isolated over a rostrocaudal distance of 1000 μm starting at 800 μm from the tip of the olfactory bulb. Although NQO-1-positive glomeruli are absent in the ventral region of the olfactory bulb (180° angle) from a wild-type mouse, NQO-1-positive glomeruli are consistently observed in the most ventral region of the OB in slit-1−/− and robo-2c/c;syn-1Cre/+ mice. Shown are representative plots from a single olfactory bulb for each genotype (n = 4 olfactory bulbs from 2 mice of each genotype). D, Dorsal; V, ventral; L, lateral; M, medial.