APP and Alzheimer disease: Although many studies have shown that RTN3 inhibits the APP process by directly interacting with β-secretase (BACE1) (He et al., 2004; Shi et al., 2009b), another important function of RTN3 in the formation of RTN3-immunoreactive dystrophic neurites (RIDNs) was emphasized in the pathogenesis of AD (Shi et al., 2009a).