PRNP and Creutzfeldt Jacob disease: In subsequent years, we showed that the phenotypic heterogeneity of the sporadic form of CJD (sCJD) is largely driven by the pairing of two sets of major determinants of disease phenotype: the genotype – MM, MV, VV – at the methionine (M)/ valine (V) polymorphic codon 129 of the human prion protein (PrP) gene and the type, 1 or 2, of the pathogenic, disease-related form of the prion protein (PrPD) [12, 24, 25, 27, 29].