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Figure 1


Fig. 1. SG cells form the optic stalk, the monolayered tubular structure that surrounds the R axon bundle. Unless otherwise noted, all specimens are late third instar viewed from a lateral perspective. Gal4 expression was detected with UAS-mCD8GFP (green) and glial cells with anti-Repo (Blue), except where noted. (A) Developing Drosophila visual system. Photoreceptor cells extend their axons (R axons; white) toward the target region, the lamina (green, anti-Dachshund), in the optic lobe. R axons form a bundle in the optic stalk. (B) R axons (green, visualized with GMRGal4) are surrounded with glial cells (white). (C) Processes of WG (green, visualized using ptc-Gal4) enwrap R axons (magenta, anti-HRP) in the optic stalk (arrow). Note that ptc-Gal4 also labels a subset of epithelial cells of the eye disc (arrowhead). (D) SG cells (green, visualized using NP4702-Gal4) form the outer sheath (arrows) that surrounds the R axons (magenta, anti-HRP). (E) An optic stalk carrying NP4702-Gal4 and UAS-GFP. SG cells (green) are arranged along the AP axis, and form a sheath by tightly contacting each other. (E') A single SG cell, which is clonally labeled by mCD8GFP (green), extends two long processes anteroposteriorly. (F) An optic stalk carrying NP4702-Gal4, viewed from a horizontal perspective. SG cells (green) form a single-cell layer. LamininA (magenta, anti-LamininA) is detected on the surface of the SG cell layer. (G,H) Quantitative analysis of the optic stalk morphology. (G) An optic stalk stained with anti-Perlecan (magenta). The green bar indicates the height of the optic stalk, while the white bar indicates the diameter. (H) Quantification of the average length of height (A/P) and the diameter (D/V) of wild-type optic stalks. The error bars indicate s.d. (I,J) Schematic drawings of the optic stalk. (I) WG cell processes (gray) loosely enwrap several R axons (magenta). SG cells (green) surround the entire R axon bundle, forming an outer sheath. (J, left) The optic stalk consists of SG cells (green), which form a monolayered tubular structure, and is surrounded by the BM (gray). (J, right) The optic stalk viewed from a horizontal perspective (top) or a lateral perspective (bottom). (A,B,C,D,E,G) Anterior is upwards and dorsal is to the right. (F) Lateral down, dorsal right.