DICER1 and Parkinson disease: First, already a heterozygous ablation of Dicer in adult DA neurons resulted in a progressive loss of striatal DA and its metabolites, with apparent differential vulnerability of male versus female mice Importantly, DICER1 appears to also be downregulated in DA neurons from PD patients,32, 39 implying that the age-related decline of Dicer function could represent a mechanism contributing to pathogenesis of PD.