FMR1 and fragile X syndrome: Loss of FMRP in patients with FXS and Fmr1 KO mice leads to an increase in general mRNA translation due to hyperactivation of mTORC1 and ERK signaling, resulting in FXS pathology (Darnell et al. 2001; Osterweil et al. 2010; Sharma et al. 2010).