Figure 8.

APPL levels modify the degenerative phenotype. A, Expressing UAS-GFP in GMR-GAL4; UAS-dBACE^RNAi flies does not alter the degenerative phenotype (left) nor does GFP expression alone cause a phenotype (right). B, Coexpression of full-length APPL does not affect the vacuolization caused by the dBACE knockdown (left), although we now detect a few vacuoles in the lamina neuropil (arrow) in addition to the vacuoles in the lamina cortex (arrowheads). Expression of UAS-APPL alone results in a few vacuoles in the lamina cortex (arrowheads, right). C, Inducing UAS-dBACE^RNAi in flies lacking APPL (Appl^d) suppresses the degenerative phenotype and the occasional remaining vacuoles are very small (arrowhead, left) and comparable to those observed in the Appl^d control flies shown (arrowhead, right). D, In contrast, coexpression of the secretion-deficient form of APPL causes a strong enhancement of the lamina cortex phenotype (arrowheads, left). Expression of this construct alone results in vacuole formation in the lamina cortex (arrowheads, right), similar to expression of the dBACE^RNAi construct alone (A, left). E, Quantification of the vacuoles in dBACE knockdown flies with changes in APPL levels (left) and vacuolization caused by changes in APPL levels without knocking down dBACE (right). **p < 0.01, ***p < 0.001. All flies were 4 weeks old. Scale bar, 10 μm.