HTT and Huntington disease: A link between neuronal toxicity and amyloid aggregation is further supported by post-mortem analyses of HD brains, which contain amyloid aggregates formed primarily by N-terminal exon 1 truncations of Htt (Difiglia, 1997; Landles et al., 2010; Mangiarini et al., 1996; Ross and Poirier, 2004).