Fig. 3. Peripheral glia direct fasciculation of olfactory neurons in the antenna but do not influence patterning of the lobe. (A-C) Pupal antennae stained with mAb 22C10 (blue) to visualize sensory neurons; glia are labeled with anti-Repo antibodies (red). In the wild type (A) at 25 hours APF, Repo-positive glial cells associate with the axons of the sensory neurons in three fascicles (1, 2, 3). Expression of GFP driven by MZ317-Gal4 GAL4 shows glial cell bodies and their processes wrapping each of the fascicles (green). (B) In 36 hour APF ato¹/Df(3R)p¹³ antennae, there is a reduction of glia ( 35 Repo-labeled cells in ato hypomorphs compared with 100 in the wild type) and the three fascicles (1*, 2* and 3*) merge into a single bundle. (C) 25 hours APF; MZ317-Gal4 UAS-GFP/UAS-DNCdc42; ato¹/Df(3R)p¹³ antenna. The MZ317-Gal4 enhancer trap line drives expression of DN-Cdc42 as well as GFP in glia. Glial cells (red) are reduced in number; remaining cells are aggregated in the proximal region of the antenna. Only two exiting fascicles (1* and 2*) can be recognized. Inset shows glial cells stained with anti-Repo; cell bodies are demarcated by dotted lines. Dying cells show a fragmented staining. (D-F) Olfactory lobe morphology of the genotype described in (C). (D) 36 hours APF; a single glomerulus shows Fas II staining; lobe associated glia (green) are present normally surrounding the lobe (dotted line). (E,F) 60 hours APF; glomerular formation proceeds normally and several glomeruli can be recognized (* in E). Ectopic expression of DN-Cdc42 in the glial cells associated with the lobe does not appear to affect their morphology and processes can be seen entering lobe (arrowheads in F). (G,H) Ectopic expression of constitutively active form of Rac in sensory neurons in SG18.1-Gal4 UAS GFP/+; UAS Rac^V12/+ animals. (G) 36 hour APF antenna stained with mAb22C10 (blue) and anti-Repo (red); the SG18.1-Gal4 GFP is shown in green. Sensory neurons exit normally in three fascicles (1, 2, 3) (ar, arista). (H) Adult antennal lobe from genotype described in G. The entry of sensory neurons into the antennal lobe is shown by arrowheads, but neurons within the lobe are completely disorganized. The inter-antennal commissure (?) fails to form. Scale bars: in A, 30 µm in A-C; in D, 30 µm in D-F; in H, 20 µm.