GRM5 and fragile X syndrome: Building upon the mGluR5 theory of FXS [26] and our own findings using postmortem brain tissue from people with autism, we hypothesize that activation of mGluR5 in the brains of children with autism [30,31,97] leads to subsequent translocation of protein for FMRP from neuronal cell bodies to dendrites, and eventual decrease in FMRP at synapses [25].