Insertion of extra OR sequences in the OR region or mutations in the post OR region are associated with spontaneous conversion of mutated PrPs to pathogenic PrPs, causing hereditary prion diseases in humans [67], suggesting that structural instability of the OR region or in the post-OR region might also be involved in the unfolding of the mutant PrPs (Figure 2D,E). This evidence concerns the gene MSMB and prion disease.