Alternatively, modulation of group III mGLUR activity may balance glutamatergic activity in the basal ganglia circuits during disease.101 Trafficking plays a critical role in modulating the spatiotemporal localization and activity of mGLURs.102-107 Excitotoxicity via glutamatergic signalling is a hallmark of HD, including signalling via metabotropic glutamate receptors.108 Enhanced levels of mGLUR7 surface expression may contribute to the glutamatergic signalling that occurs in HD cells and the downstream destruction resulting from glutamatergic excitotoxicity. Here, GRM7 is linked to Huntington disease.