Mutations of epsilon-sarcoglycan gene (SGCE) have been implicated in myoclonus-dystonia (M-D), a movement disorder. To determine the pathophysiology of M-D, we produced Sgce knockout mice and found that the knockout mice exhibited myoclonus, motor impairments, hyperactivity, anxiety, depression, significantly higher levels of striatal dopamine and its metabolites, and an inverse correlation between the dopamine and serotonin metabolites. The results suggest that the diverse symptoms associated with M-D are indeed resulted from a single SGCE gene mutation that leads to alterations of dopaminergic and serotonergic systems. Therefore, antipsychotic agents and serotonin reuptake inhibitors may offer potential benefits for M-D patients.