Fig. 2. Characterization of GC-D⁺ neurons in the MOE. (A) Whole-mount view of the turbinates of a GCD-ITL homozygous 3-week-old (3 wk) mouse after X-Gal staining. Labeled cell bodies can be seen on all turbinates, with a greater number situated towards the ventral aspects. The greatest accumulation is located at the caudal end of the MOE (arrow). Anterior. left, dorsal up. (B) Whole-mount view of the septal area of a GCD-ITL homozygous mouse (3 wk). A similar distribution pattern as in the turbinates is apparent. Labeled axons take a straight route towards the cribriform plate. A few labeled cells reside within the septal organ (asterisk). (C) Sections through the MOE of a GCL-ITL homozygous mouse (P10). Labeled cell bodies (arrows in left and middle panels) reside within the lower layers of the epithelium. The morphology of labeled cells is similar to that of conventional OSNs. Cells extend dendrites towards the lumen (asterisks in right panels) and axons towards the lamina propria (arrows in right panels). (D) High-magnification view of a GFP⁺ cell in a whole-mount of the MOE of a GCD-ITG homozygous mouse (3 wk). A typical neuronal morphology is apparent with a dendrite and dendritic knob (asterisk) and a long axon (arrows). Insert shows en face view of a dendritic knob with GFP⁺ cilia. (E) Sections through the MOE of a GCL-ITG/GCL-ITL double heterozygous mouse (P7). The cell body is positive for the intrinsic fluorescence of GFP (left panel) and ß-galactosidase immunofluorescence (middle panel). The combined image is shown on the right. Asterisk in middle and right panels denotes the dendritic knob. Scale bars: 1000 µm A,B; 40 µm C, left two panels; 20 µm C, right panel; 20 µm in D,E.