The phenotype of human
prion diseases is influenced by the
prion protein (PrP) genotype as determined by the
methionine (M)/
valine (V) polymorphism at
codon 129, the
scrapie PrP (PrPSc) type and the etiology. To gain further insight into the mechanisms of phenotype determination, we compared two-dimensional immunoblot profiles of
detergent insoluble and
proteinase K-resistant PrP species in a type of
sporadic Creutzfeldt-Jakob disease (sCJDMM2), variant CJD (vCJD) and sporadic fatal
insomnia (sFI). Full-length and truncated PrP forms present in the insoluble fractions were also separately analyzed. These three diseases were selected because they have the same M/M PrP genotype at
codon 129 and the same type 2 PrPSc, but different etiologies, also sCJDMM2 and sFI are sporadic, whereas vCJD is acquired by
infection. We observed minor differences in the PrP
detergent-insoluble fractions between sCJDMM2 and vCJD, although both differ in the corresponding fractions from sFI. We detected more substantial heterogeneity between sCJDMM2 and vCJD in the two-dimensional blots of the
proteinase K-resistant PrP fraction suggesting that different PrP species are selected for conversion to
proteinase K-resistant PrP in sCJDMM2 and vCJD. These differences are mostly, but not exclusively, due to variations in the type of the N-linked
glycans. We also show that the over-representation of the highly glycosylated forms distinctive of the
proteinase K-resistant PrPSc of vCJD in one-dimensional blots is due to differences in both the amount and the natures of the
glycans. Overall, these findings underline the complexity of phenotypic determination in human
prion diseases.