Importantly, mutant Htt exon 1 carrying a polyQ expansion (herein 'mHtt-Ex1') suffices to cause HD-like disease in animal models (Goldberg et al., 1996; Sathasivam et al., 2013; Wellington et al., 2002) and is thus widely used as a relevant model for HD biology and pathology. The gene discussed is HTT; the disease is Huntington disease.