AD brains have a heightened expression of UPR activation markers, including phosphorylated PERK, eukaryotic initiation factor 2α (eIF2α), and IRE1, as well as BiP, which correlate with Braak stages [255–258], suggesting that UPR has a bearing on AD pathology at an early stage. This evidence concerns the gene EIF2AK3 and Alzheimer disease.