FXS is also generally associated with variable behavioral symptoms that can include anxiety, hyperactivity, hypersensitivity, stereotypies, memory deficits, and sleeping problems. FXS results from the loss of the fragile X mental retardation protein (FMRP), an RNA‐binding protein associated with mRNAs and the translation machinery and whose absence in Fmr1‐deleted mice (Fmr1‐KO) recapitulates FXS‐like phenotypes (The Dutch‐Belgian Fragile X Consortium, 1994; Mientjes et al, 2006), with perturbation of neuronal protein synthesis in hippocampus and cortex (Qin et al, 2005; Dolen et al, 2007). This evidence concerns the gene FMR1 and fragile X syndrome.