a. A MECP2_e1/Myc fusion construct was cloned into a scAAV2 ITR backbone under a truncated version of the murine Mecp2 promoter. b. Graph showing transduction efficiency in three brain areas of Mecp2-null mice (n=3) at endpoint following tail vein injection of scAAV9/MeP-MECP2. See suppl. figure 3 for representative images. Plots show mean ± SEM. c. Survival plot showing extended survival of Mecp2-/y mice injected with scAAV9/MeP-MEPC2 (purple open boxes, n=12) compared to untreated controls (green closed boxes, n=10). The median survival period in the treated mice was significantly higher than in the untreated group (15.4 vs 10.6 weeks, respectively, P<0.01 Gehan-Breslow-Wilcoxon test). Control WT mice showed no mortality over the experimental period (filled circles, n=8). Arrow indicates scAAV/MeP-MECP2 injection time. d. Micrographs showing GABA immunolabelling of transduced (MeCP2-positive, arrows) and non-transduced cells (arrowheads) in layer 2/3 of motor cortex of a Mecp2-null mouse. e. Bar plot showing elevated levels of anti-GABA immunofluorescence in transduced cells (***p<0.001, t-test, n=166 cells). mut ITR, mutated inverted terminal repeat; MeP, truncated murine Mecp2 promoter; BGHpolyA, boving growth hormone polyadenylation signal. Scale bar in d = 10μm.