HTT and Huntington disease: In HD, IGF-1 signalling, Akt activity and subsequent phosphorylation of huntingtin at serine 421 are deregulated as HD progresses (Colin et al, 2005; Gines et al, 2003; Mochel et al, 2007; Pouladi et al, 2010; Saleh et al, 2009; Warby et al, 2005).