Figure 1. ab overexpression in scrib mutant clones promotes neoplastic overgrowth of eye/antennal epithelial tissue throughout an extended larval stage.

Mosaic eye/antennal discs (anterior to the left in this and all subsequent figures) generated with ey-FLP and taken from larvae 5 days (A–H) or 9 days (I,J) AEL. Clones are positively marked by GFP (white, or green in merges). Tissue morphology is shown by F-actin (red in merges), and cell fate by Elav and Dll (white, or blue in merges – dark blue when overlaid with GFP). Brain lobes in I,J are marked by BL. GFP (panels A–J), Elav (panels A′,C′,E′,G′,I′), Dll (panel B′,D′,F′H′,J′) and merges (panels A″–J″). (A,B) Control mosaic eye/antennal discs show the normal pattern of Elav expression in developing photoreceptor cells, and Dll expression within the antenna. (C,D) scrib¹ cells still express Elav and Dll, although the normal pattern of Elav-expressing photoreceptor cells is disrupted by alterations in tissue morphology. (E,F) ab overexpressing clones still express Elav and Dll, but are often larger than control clones within the antennal region, and in some discs ectopic domains of Dll expression are observed (F, arrowhead). (G,H) scrib¹+ab clones are larger than scrib¹ clones, and do not express Elav (G, arrowhead), although Dll expression is maintained (H, arrowhead). (I,J) scrib¹+ab clones at day 9 are massively overgrown and the two eye/antennal discs fuse with each other and with the Elav-expressing brain lobes (I), whilst the Dll-expressing domain in the antennal disc is maintained (J). Yellow scale bar = 50 µm.