APP and fragile X syndrome: A possible link between FXS and AD has been proposed since FMR protein binds to the amyloid precursor protein (APP; Sokol et al., 2011), APP is overexpressed in the FMR1 KO mice brain (D’Agata et al., 2002) and the group 1 mGluR agonist DHPG increases APP translation (Westmark and Malter, 2007; Sokol et al., 2011).