A recent report demonstrated that early parkinsonism is caused by defective DA release by mitochondrial dysfunction preceding cell death.143 In a conditional Ndufs2-knockout mouse that causes mitochondrial complex I disruption, loss of axonal DA release generated deficits in motor learning and fine motor control but was necessary but not sufficient for full levodopa-responsive parkinsonism, for which impairment of somatodendritic release within the SNpc was required. This evidence concerns the gene NDUFS2 and Parkinsonism.