Inhibition of complex II by the HD-causing mutated Huntingtin (Htt) protein [14], as well as by HD-like pathology induced by pharmacological inhibition of complex II, e.g., by 3-nitropropionic acid (3-NP) [15], support the notion that deterioration of the complex II function is central in HD pathogenesis. This evidence concerns the gene HTT and Huntington disease.