PolgA D257A mutation increases normalized Aβ42 levels in APP/Ld mice. (A) Hemi-brain homogenates of ~12 month-old APP/Ld and D257A; APP/Ld mice were prepared and Aβ42 levels were measured using a human Aβ42-specific ELISA. Values are expressed in nanograms per milligram of total brain protein. Note that the raw Aβ42 levels are not significantly elevated in D257A; APP/Ld mice (n = 10), but that an upward trend exists, as compared to APP/Ld mice (n = 12). (B) 15 μg/lane of the same mouse brain homogenates in (A) were used for immunoblot analysis of full-length transgenic human APP/Ld protein using the anti-human APP monoclonal antibody 6E10. Ponceau S staining was used as a loading control. The numbers on immunoblot correspond to specific genotypes (as denoted in boxed legend key) of individual brain homogenates that were randomly loaded. (C) Full-length APP/Ld immunosignals in (B) were quantified by phosphorimager, normalized to Ponceau S staining intensities per lane, and expressed as percentage of the mean APP/Ld immunosignal. Note that levels of APP/Ld are significantly reduced in the D257A; APP/Ld mice compared to APP/Ld mice (mean ± SEM; **p < 0.01; Student’s t-test). (D) Raw Aβ42 ELISA values (ng/mg) from (A) were normalized to the mean transgenic APP/Ld protein levels for each genotype as determined in (C). Note that Aβ42 levels normalized to APP/Ld are significantly increased in the D257A; APP/Ld mice compared to APP/Ld mice (mean ± SEM; *p < 0.05; Student’s t-test).