These defects can account for the abnormal maturation of dendritic spines in FXS (Swanger and Bassell, 2011; Bardoni et al., 2012; Maurin et al., 2014).The lack of FMRP interferes with mechanisms underlying metabotropic glutamate receptor (mGluR) receptor-dependent long-term depression (LTD) – a prominent form of synaptic plasticity (Huber et al., 2002) and epileptogenesis (Chuang et al., 2005). This evidence concerns the gene FMR1 and fragile X syndrome.