a) Schematics of the C-terminus truncated Tau (Tau-ΔC, missing last 49 amino acids) used in the study, as compared to the full-length (FL) Tau. Below: western blotting analysis to confirm the expression of Tau deletion used in the study. Note the smaller size of the C-terminus truncated Tau (Tau-ΔC), as compared to that of the full-length Tau. Both Tau transgenes are tagged with GFP epitope at their C-termini. In (a-d), the ubiquitous arm arm-Gal4 driver was used to drive the ectopic Tau expression, protein expression was examined by anti-GFP antibody, with Actin served as loading control. + / + : samples from wildtype non-transgenic flies. ( b) Confirmation of the proper expression of endogenous dHtt as well as the human full-length Huntingtin (hHtt) and GFP proteins from the corresponding transgenes by Western blotting analyses. The ubiquitous arm-Gal4 driver was used to drive the hHtt and GFP transgene expression. n = 3 independent experiments. ( c and d) Ectopic expression of full-length human Huntingtin (hHtt) significantly rescued several dhtt associated phenotypes, including ( ko c) the reduced mobility and ( d) shortened lifespan of mutant adults. N values are indicated in the figure and were pooled from 4 independent experiments. ( e and f) Ectopic expression of hHtt significantly rescued Tau-induced phenotypes in dhtt mutant background, including the exacerbated ( ko e) mobility decline and ( f) reduced lifespan. A307-Gal4 driver was used to drive the Tau-ΔC-GFP and hHtt expression. N values are indicated in the figure and were pooled from n = 4 independent experiments. ( g– i) hHtt partially suppressed the increased accumulations of ( g– h) total ubiquitinated proteins and ( f) Tau-ΔC in dhtt mutant flies. Ubiquitous ko−/− arm-Gal4 driver was used to drive the hHtt expression; Tau-ΔC level was examined by anti-GFP antibody, with Actin serving as loading control. n = 3 independent experiments. All values are mean + s.e.m. and differences are significant for ∗ P < 0.05 using analysis of variance + Bonferroni test.