Eph and ephrin expression patterns in the D. melanogaster larval third instar optic lobe.

<p>A1–A5) anti-HRP staining (green) reveals overall optic lobe architecture. Posterior to the morphogenetic furrow (MF), retinal axons of ommatidia (small circles, A1) in the developing eye disk (ED; A2) project through the optic stalk (OS; A2) to topographically innervate two target regions in the brain: the lamina (Lam; demarcated by the lamina furrow, LF; A3) and the medulla (A5), which lies proximal to the lamina. Axons of medulla cortical neurons (Med cortex; A5) also project topographically to form a crescent-shaped neuropil (Med n'pil; A5). Schematic representations of optic lobe architecture are shown in A1 (eye and lamina) and A4 (medulla). B1-B5) anti-Eph staining (grayscale). Across the ED, Eph expression appears uniform posterior to the MF. Within the Lam, Eph expression is highest at the posterior midline and lowest at the dorsal-ventral margins of the anterior (B2, B3; depicted schematically in B1). Within the medulla, Eph expression is again highest at the midline, diminishing along the dorsal-ventral axis (B5; depicted schematically in B4). C1–C5) anti-Ephrin staining (grayscale) reveals uniform expression of Ephrin across the developing ED (C2). Within the Lam Ephrin expression appeared relatively uniform (C3). Ephrin-specific expression patterns in the developing ED and Lam are depicted schematically in C1. Within the medulla, Ephrin expression mirrors that of Eph: highest at the midline, diminishing along the dorsal-ventral axis (C5; depicted schematically in C4). D) Summary of Eph/Ephrin expression patterns in the developing visual system (horizontal perspective, which depicts the spatial relationship of the lamina and medulla target fields). Anterior (red arrow) and dorsoventral margins (yellow arrows) are indicated. All image panels were of late third larval instar stage brains stained for HRP (anti-HRP, A2, A3, A5), Eph (anti-Eph, B2, B3, B5) or Ephrin (anti-Ephrin, C2, C3, C5). Note that A2, B2, and C2 are the same image for which individual channels have been displayed. All other images represent distinct specimens. Dorsal (D), ventral (V), anterior (A) and posterior (P) orientations (central compass) are identical for all panels.