Both RGS2 and DLGAP1 exhibited significantly lower expression in postmortem AD brain tissues compared with matched controls of data set GSE5281.28 Moreover, RGS2 also exhibited lower expression in whole blood data set GSE63060 (ref. 29) for both AD and MCI patients compared with healthy controls (FD=−1.2 and −1.3; P=0.000072 and 0.0000012, respectively; Figure 4c), suggesting that its low blood expression may serve as a peripheral MCI and AD biomarker. This evidence concerns the gene RGS2 and Alzheimer disease.