Based on an altered expression of GABA receptor subunits in the absence of FMRP (Adusei et al., 2010) and a reduced production of GABA (Davidovic et al., 2011), it has been shown that an impairment of the GABAergic system is involved in FXS (D’Hulst and Kooy, 2007; Braat et al., 2015). This evidence concerns the gene FMR1 and fragile X syndrome.