Humanized transgenic mouse brain (TgHu) expressing the three polymorphic genotypes of PRNP codon 129 (TgHuMM, TgHuMV, TgHuVV) have been commonly used as a PMCA substrate to examine the zoonotic threat posed by animal prion diseases (Barria et al., 2014b). This evidence concerns the gene PRNP and prion disease.