PSEN1 and Alzheimer disease: Since the AD-related Aβ deposition was shown to be dramatically accelerated and further enhanced by the mutation of the APP cleaving enzyme presenilin 1 [68, 85–87], in this study we used APP/PSEN1 double TG mutants, as a presumably higher fidelity mouse model, to test for additive effects of less energetic (~150 MeV) proton radiation and at lower doses ≤1 Gy.