Fig. 6. Immunohistochemistry of necklace and ectopic glomeruli. (A) Sections (18 µm) through the caudal OB at the level of the necklace area of a GCD-ITG homozygous mouse stained with an antibody to PDE2A. All GFP⁺ axons (green) are also PDE2A⁺ (red), and are thus yellow in the overlay image. Right-most panel: large glomerulus. Dorsal is up. (B) Sections (18 µm) through the caudal OB at the level of the necklace area of a GCD-ITL homozygous, NP2- heterozygous mouse stained with an antibody to ß-galactosidase (red). A subset of Nrp2⁺ (GFP; green) glomeruli is also positive for ß-galactosidase (arrows); other necklace glomeruli are only Nrp2⁺ (asterisks). All GC-D⁺ glomeruli are also Nrp2⁺ (yellow in overlay). Right-most panel: high magnification. Dorsal is up. (C) Sections (18 µm) through the OB of a GCD-ITG homozygous, F homozygous mouse stained with antibodies to OMP (red). Green is the intrinsic green fluorescence of GFP. Three left panels: a high-magnification view of an ectopic glomerulus that is filled by GC-D⁺ axons (yellow in overlay), at the midlevel of the OB outside the necklace area. Right-most panel: example of glomeruli in the necklace area. A GC-D⁺ glomerulus (red and green) above a GC-D^- glomerulus (red only). Ectopic glomeruli reside deeper than glomeruli in the necklace area. Dorsal is up. (D) Sections (18 µm) through the midlevel OB outside the necklace area of a GCD-ITL homozygous, NP2- homozygous (GFP; green) mouse stained with antibodies to MAP2 (red) and ß-galactosidase (blue). MAP2 stained dendrites fill the glomeruli in the glomerular layer (GL) including the ectopic GC-D⁺/Nrp2⁺ glomerulus (light blue in overlay image), but are absent in the outer nerve layer (ONL). Scale bars: 100 µm in A,B,D; 50 µm in C.