Application of recombinant calpain-1 to recombinant huntingtin or to mouse brain extracts caused the appearance of fragments with molecular weights between 45 and 72 kDa, which could also be observed in post-mortem brain samples of both healthy and HD-affected subjects (Kim et al., 2001, 2003; Gafni and Ellerby, 2002; Lunkes et al., 2002). The gene discussed is HTT; the disease is Huntington disease.