Fig. 2.

Proliferating progenitors in the vomeronasal organ (VNO) exhibit sensory neuron morphology. (a) Imaging of knob layer on the luminal surface of the VNO sensory epithelium of a doublecortin (Dcx)-DsRed/OMP-GFP double transgenic mouse (top panels). DsRed⁺ knobs intermingle within the more mature population of GFP⁺ vomeronasal sensory neurons (VSNs). Scale bar, 20 μm. DsRed⁺ axonal processes (second panels) are detected and extend towards the accessory olfactory bulb (AOB) together with mature GFP⁺ fibers. Scale bar, 50 μm. Medial view of the caudal part of the olfactory bulb (third panels) where the axons from the VNO bend off laterally towards the AOB. GFP expression in VSNs is markedly lower than in the main olfactory epithelium and therefore axon bundles from the VNO appear as substantially darker. In DsRed images, VSN axon bundles are easily identified by their conspicuous parallel alignment. Scale bar, 100 μm. Sagittal view of AOB glomeruli (bottom panel). DsRed⁺ axons originating in the nerve layer terminate in several glomeruli (dotted circles), visualized by OMP-GFP fluorescence. Scale bar, 20 μm. (b) Density measurements of DsRed⁺ and GFP⁺ knobs reveal a sparser density of immature knobs compared to the mature population. (c) Quantification of randomly sampled knobs shows that double-labeled GFP/DsRed⁺ knobs represent 12.14 % of the total GFP⁺ knob population. Values in (b) and (c) were calculated using 12 areas from six Dxc-DsRed/OMP-GFP mice; mean ± standard deviation (SD) = 1.41 ± 0.72 DsRed and 11.25 ± 1.55 OMP-GFP knobs per 100 μm². DsRed-GFP/GFP ratio = 12.14 %, 2,649 double positive knobs