PCDH9 and Alzheimer disease: In contrast, 17 AD-associated DEGs (Table 1) went from upregulated in 3xTg-AD mice to downregulated in wild-type at 6.5 mo (Srgap1, Lrfn5, Myt1l, Kndc1, Pcsk2, Cacna2d3, Prkar1b, Pcdh9, Mei, Foxp2, Lin7a, Pth2r, St8sia3, Slc17a7, Rbp4, Etv4, and Ncan), which serve as potential blood biomarkers during the MCI phase of AD pathology.