Fig. 4. Glomerular morphology and trajectory of misrouted P2 axons in GpiRNCAM transgenic mice. (A-D) High power images of P2 innervated glomeruli. Major P2 glomeruli showed a similar morphology in control mouse (A) and GpiRNCAM transgenic mouse (B). An increased number of a distinct type of P2 glomeruli, in which P2 axons contributed only fractionally to the total number of innervated axons, were detected in transgenic mice. These semi-innervated P2 glomeruli showed a similar morphology in mice heterozygous (C) and homozygous (D) for the targeted P2 allele. (E) Location (vertical lines) of serial coronal sections shown in E1-9. The semi-innervated P2 glomeruli analyzed was located 360 µm caudal to the major lateral P2 glomeruli. The drawing depicts a side view, with the major lateral P2 glomerulus (L), axon trajectory of P2 axons (red line) and semi-innervated P2 glomeruli (circle) located on the lateral side, whereas the major medial P2 glomerulus (M) is located on the opposite (medial) side of the olfactory bulb. (E1-9) High power images of serial coronal olfactory bulb sections from a GpiRNCAM transgenic mouse. Misguided P2 axons segregated from a lateral division of P2 axons close to the major lateral P2 glomerulus (E1), bypassed their correct target and coursed in a caudal and ventral direction (E2-7) to a glomerulus primarily innervated by axons of another OR specificity (E8-9). Photographs were processed to show ß-galactosidase staining in red, while UV visualized the nuclear counterstain in blue.