In a study of spinal cerebellar ataxia, overexpression of mutant ATXN1 protein in a mouse model stimulated the proliferation of stem cells in the developing cerebellum and excessive differentiation into GABAergic inhibitory neurons, leading to functional disruption of Purkinje cells and causing cerebellar impairment resulting in ataxia [8]. Here, ATXN1 is linked to cerebellar ataxia.