In Fmr1-knockout (KO) mice—a model for fragile X syndrome—the protein levels of several FMRP targets are increased in PSD fractions either from the neocortex or hippocampus, including Sapap1–3, Shank1, Shank3, and various glutamate receptor subunits [117]. This evidence concerns the gene SHANK3 and fragile X syndrome.