Fig. 1.

Activity-dependent Sema7A expression in OSN axons. a Distribution of Sema7A in the glomerular layer of the OB. OB sections of the WT at P5 were immunostained with anti-Sema7A and anti-OMP antibodies. Scale bar=25 μm. b Detection of Sema7A in the axon termini of OSNs. Immuno-electronmicroscopy identified Au-labeled Sema7A (arrows) in the pre-synaptic termini of OSN axons at P5. No Au signals were detected in the Sema7A KO. The number of signals per contact surface was counted (right). ^***p < 0.005 (Student’s t-test). Error bars indicate SD. n = 3 animals for each. Scale bar=300 nm. c Variable expression of Sema7A among different glomeruli. OB sections at P10 were immunostained with anti-Sema7A antibodies. EYFP-tagged rI7, ECFP-tagged MOR29A and EYFP-tagged MOR29B glomeruli were detected by immunostaining with anti-GFP antibodies. Scale bar=25 μm. d Activity-dependent Sema7A expression. Left, Down-regulation of Sema7A expression by uni-lateral naris occlusion. Mice were unilaterally occluded at P0. OE sections (P6) were analyzed by in situ hybridization. OB sections (P6) were analyzed by immunostaining with anti-Sema7A antibodies. (+) occluded, (−) unoccluded. Scale bars, 50 (upper), 100 (lower) μm. Middle, CNG-channel-dependent Sema7A expression. Duplicated glomeruli of rI7 in the heterozygous CNG-A2 KO were analyzed for Sema7A expression at P5. EYFP-tagged rI7 glomeruli were detected by immunostaining with anti-GFP antibodies. OB sections were immunostained with antibodies against CNG-A2 and Sema7A. Scale bar=25 μm. Right, OR-activity dependent Sema7A expression. A DRY-motif mutant of rI7 suppresses Sema7A expression because it does not generate cAMP. OE sections expressing the WT rI7 and DRY-motif mutant (RDY) were analyzed by in situ hybridization for Sema7A expression at P5. OSNs expressing the EYFP-tagged rI7 were detected by immunostaining with anti-GFP antibodies. Scale bar=10 μm. GL, glomerular layer