δ-secretase has been found to produce Aβ in the development of AD, which further induces phosphorylation of SGK1 and JAK2, and SGK1 can in turn activate STAT1, and δ-secretase simultaneously cleaves tau proteins and produces the tau(1−368) fragment, which binds to the activated STAT1 and promotes the production of Aβ thereby forming positive feedback regulation with phosphorylated SGK1 (Zhang et al., 2021). The gene discussed is MAPT; the disease is Alzheimer disease.