PSEN1 and Alzheimer disease: Initially it was found that ablation of PrPC rescued memory impairment, synaptic dysfunction and premature survival in the APPswe-PS1ΔE9 AD mouse model (APP-PS1) [12, 13], but shortly afterwards, it was reported that deletion of PrPC in a different AD mouse model, J20 transgenic mice, did not alter any of the parameters measured, and by contrast actually accelerated premature death in these animals [14].