Westmark highlights a study which demonstrated how FMRP cooperates with other autism-related molecules in experience-dependent synaptic pruning through proteasome-mediated degradation of postsynaptic density 95 (PSD-95) and how that mechanism fails in fragile X syndrome (Tsai et al., 2012; Westmark, 2013). Here, FMR1 is linked to fragile X syndrome.