Control of Transgenic APP Expression by Dox
(A) Western blotting for transgenic APP using the human-specific 6E10 antibody shows expression of full-length protein in forebrain tissue from young predeposit double transgenic animals (line 107) and its suppression following dox treatment. Untreated animals show high levels of transgene expression; protein levels drop dramatically in animals acutely treated with dox for 2 wk. A faint, but detectable band of full-length protein remains in acutely treated animals that can be eliminated in mice born and raised on dox.
(B) Immunoblotting with the N-terminal antibody 22C11 to detect both transgenic and endogenous protein shows that dox treatment reduces APP/APLP to levels found in nontransgenic mice.
(C) Measurement of signal intensity from the Western blot in (A) shows transgenic APP levels are decreased more than 95% by dox in both acutely and chronically treated animals (97.2% for 4 wk + 2 wk dox, 98.0% for reared on dox versus 4 wk untreated; ANOVA effect of treatment group F 4,15 = 85.55, p < 0.001). APP levels in 4 wk + 2 wk dox, reared on dox, and nontransgenic (NTg) were not significantly different (p > 0.9, Tukey post-hoc test).
(D) Measurement of signal intensity from the Western blot in (B) shows total APP/APLP levels in dox-treated tTA/APP mice are significantly lower than in 4-wk-old untreated mice (ANOVA effect of treatment group F 4,15 = 84.41, p < 0.001) and indistinguishable from those of nontransgenic animals (p > 0.9, Tukey post-hoc test). *, p < 0.001 versus untreated 4-wk-old mice, Tukey post-hoc test applied to significant effect of group ANOVA.