In the ataxic SCA182Q mouse model, with PC-specific 82Q repeats in the ataxin-1 gene, the progressive decline of mGluR1 function begins at the early stage of disease (at 5 weeks of age) before the onset of overt ataxia and PC morphological alterations (at 12 weeks of age; Clark et al., 1997; Zu et al., 2004). Here, GRM1 is linked to cerebellar ataxia.