HTT and Huntington disease: In the context of a lentiviral vector gene delivery system, shRNA targeted to the human Htt mRNA reduced Htt mRNA levels by more than 80% and almost completely prevented loss of dopamine and cAMP-regulated phosphoprotein-32 (DARPP-32) expression, and restored deficits in striatal glucose metabolism and mitochondrial complex II activity in a rat HD model.