Similar to the aberrant expression of ionotropic glutamate receptors, reductions in metabotropic glutamate receptor-5 (mGluR5) protein levels have been reported in both the motor cortex from RTT autopsy samples and in the brain of mouse models of RTT, implicating mGluR5 in the pathogenesis of RTT [112]. The gene discussed is GRM5; the disease is Rett syndrome.