FMR1 and fragile X syndrome: A mouse model of Fragile X Syndrome with a KO of the Fmr1 gene not only resulted in anxiety and abnormal social behaviors but also increased GluA2 surface expression and reduced S880 phosphorylation of GluA2 in the hippocampus (Marsillo et al., 2021), the phosphorylation that is related to AMPAR endocytosis.