HTT and Huntington disease: Beta-amyloid and tau are linked to AD (Terry, 1963; Masters et al., 1985; Grundke-Iqbal et al., 1986; Goate et al., 1991; Haass and Selkoe, 1993), alpha-synuclein to PD (Polymeropoulos et al., 1997; Uversky, 2007), huntingtin to HD (Davies et al., 1997; DiFiglia et al., 1997), TDP43 to ALS, and frontotemporal lobar degeneration (FTLD) (Arai et al., 2006; Neumann et al., 2006) and prion to TSE (Aguzzi, 2007).