Efficient RNA interference-based knockdown of mutant torsinA reveals reversibility of PERK-eIF2α pathway dysregulation in DYT1 transgenic rats in vivo

DYT1 dystonia is a neurological disease caused by a dominant mutation that results in the loss of a glutamic acid in the endoplasmic reticulum-resident protein torsinA. Currently, treatments are symptomatic and only provide partial relief. Multiple reports support the hypothesis that selectively reducing expression of mutant torsinA without affecting levels of the wild type protein should be beneficial. Published cell-based studies support this hypothesis. It is unclear, however, if phenotypes are reversible by targeting the molecular defect once established in vivo. Here, we generated adeno-associated virus encoding artificial microRNA targeting human mutant torsinA and delivered them to the striatum of symptomatic transgenic rats that express the full human TOR1A mutant gene. We achieved efficient suppression of human mutant torsinA expression in DYT1 transgenic rats, partly reversing its accumulation in the nuclear envelope. This intervention rescued PERK-eIF2 alpha pathway dysregulation in striatal projection neurons but not behavioral abnormalities. Moreover, we found abnormal expression of components of dopaminergic neurotransmission in DYT1 rat striatum, which were not normalized by suppressing mutant torsinA expression. Our findings demonstrate the reversibility of translational dysregulation in DYT1 neurons and confirm the presence of abnormal dopaminergic neurotransmission in DYT1 dystonia.