Fig. 3. GC-D⁺ glomeruli in the necklace area of the olfactory bulb. (A) Whole-mount view of the medial OB in an adult GCD-ITL homozygous mouse, stained with X-Gal. Axons enter the bulb through the cribriform plate (asterisk) on the ventral side, and project towards the caudal end of the OB where they form interconnected glomeruli. Anterior, left, dorsal up. (B) The lateral OB. A greater number of axons are entering on the lateral side, and larger glomeruli are formed. Asterisks denote the MOE turbinates. (C,D) The dorsal (C) and ventral (D) OB. Glomeruli are arranged as a closed necklace of beads on a string. Axons projecting from the MOE, glomeruli, and axonal connections between glomeruli are visible ventrally, whereas only glomeruli and axonal connections are visible dorsally. Anterior is up. (E) Three examples of lightly X-Gal stained glomeruli on the lateral OB of GCD-ITL homozygous 6-week-old (6 wk) mice. No obvious pattern of glomerular positions is apparent. Larger glomeruli tend to form on the ventral aspects of the bulb. Some glomeruli form a cluster, at a consistent position (arrows). Anterior, left; dorsal, up. (F) Section of necklace area in adult GCD-ITG homozygous mice. There are superficially located GFP⁺ glomeruli in the dorsal aspect (upper left), ventral aspect (lower left) and lateral aspect (right). A cluster of glomeruli can be seen (arrows). Dorsal is up. Scale bars: 1000 µm in A-D; 500 µm in E; 50 µm in F.