Figure 3. Knockdown of soluble guanylyl cyclase (sGC) in neurons reduces GFAP toxicity.

(a) Schematic diagram of the dual-transcriptional system. To independently manipulate gene expression in glia and neurons, the GAL4/UAS system and the Q system are used together. GFAP^R79H (QUAS-GFAP^R79H) is expressed in glia with the Q system glial-specific driver ET31-QF (green box) and RNAi lines (UAS-RNAi) targeting sGC are expressed in neurons with the GAL4/UAS system neuronal-specific driver elav-GAL4 (pink box). Nitric oxide synthase (Nos) produces NO in glia from L-arginine and O₂. NO diffuses to neighbouring neurons and activates sGC, which converts GTP to cGMP. By expressing RNAi directed to sGC in neurons, NO signalling is blocked. (b) Knockdown of two Drosophila sGC subunits, Gycα99B and Gycβ100B, with independent RNAi lines, markedly reduces the number of TUNEL-positive cells in GFAP^R79H transgenic flies (total, left). Both neuronal (middle) and glial (right) cell death are rescued by reducing expression Gycα99B and Gycβ100B in neurons. **P<0.0001, compared with UAS-lacZ control, F=15.32; 11.62; 10.15; df=29; 29, 29. one-way ANOVA with Tukey's multiple comparison test, n=6 per genotype. Flies were 20 days old. Genotype: elav-GAL4; ET31-QF; QUAS-GFAP^R79H/UAS-RNAi. RNAi lines are indicated in the figure label.