We observed a marked decrease in CAST levels in HdhQ111 striatal cells, HdhQ7 striatal cells exposed to 3-nitropropionic acid (3-NP; a mitochondrial toxin that causes HD-like symptoms in rodents and primates38), and HEK293 cells overexpressing mtHtt carrying either 73Q or 145Q when compared with the control groups (Supplementary Fig. 4b–d). The gene discussed is CAST; the disease is Huntington disease.