Figure 9.—

Loss of moleskin/dim-7 function leads to the sporadic loss of R8 photoreceptors. Expression of Elav (A, E, and I), Sens (B, F, and J), and BBO2 (C, G, and K) in control (A–D) vs. EGUF; msk⁵ (E–L) third instar larval eye discs is shown. I–L show a magnified view of the boxed area in H. Elav staining in wild-type third instar larval discs reveals the emerging crystalline order seen in the adult eye (A). Each wild-type Elav-positive cluster contains a Sens-positive R8 (B). The P{lacW} enhancer trap BBO2 is a later marker of the R8 photoreceptor. More mature R8 photoreceptors express both Sens and BBO2 (D and arrow in I–K). In contrast, the EGUF; msk⁵ eye (E–H) shows disruption of the wild-type organization with uneven spacing between Elav-positive clusters. Furthermore, some Elav-positive clusters lack Sens and BBO2 (arrowheads in I–L). Genotype of w; EGUF; msk⁵ is w; ey-GAL4,UAS-flp/BBO2; msk5, FRT79D/GMR-hid,Cl FRT79D. Genotype of w; EGUF; FRT79D is w; ey-GAL4,UAS-flp/BBO2; FRT79D/GMR-hid,Cl FRT79D.