BACE1 and Alzheimer disease: Specifically, in AD miR-124 modulates both Aβ production by targeting BACE1 [58,60] APP [59] and tau phosphorylation levels through PTPN1 signaling [62], and its decrease was detected in the CSF of patients with AD, supporting its role as a potential diagnostic biomarker in AD [43] (Table 1, Figure 2).