Figure 7.

Gγ8-tgORs disrupt targeting of OSNs expressing endogenous receptors. A–F, Medial view of the OB from 3-week-old, heterozygous rI7→M71-lacZ (A–C) and P2-lacZ (D–F) mice stained for LacZ. In control rI7→M71-lacZ mice (A), hundreds of labeled axons project to the expected location in the OB; in contrast, mice expressing Gγ8-rI7 (B) or Gγ8-M72 (C) have many fewer stained fibers that meander without convergence (arrows). Less dramatic mistargeting was detected in P2-LacZ mice (D–F). In control animals, P2-lacZ OSNs target a single glomerulus in the medial OB (D). In Gγ8-rI7 (E) or Gγ8-M72 (F) mice, the majority of P2-LacZ-stained fibers innervate a glomerulus in the appropriate region of the OB but a subset of P2-OSNs typically project to distal regions of the OB and form ectopic glomeruli (arrows). G–J, Confocal images of the OB from Gγ8-M72 mice immunostained for LacZ expression (red), counterstained with DAPI (blue), and examined for tgOR expression (green, GFP). The major P2 glomeruli rarely contain any innervation from tgOR OSNs, as indicated for a medial P2 glomerulus (G). Ectopic P2 neuron projections focus on glomeruli that also contain tgOR-OSN innervation (H, I) as well as regions of small glomeruli that do not contain tgOR expressing axons (J). Scale bars: (in A) A–F, 500 μm, (in G) G–J, 50 μm. Ventral (V) and anterior (A) directions in whole-mount images are indicated.