Molecular Subtyping of PrP^res in Human Sporadic CJD Brain Tissue

Abstract

Across the spectrum of sporadic human prion diseases (also known as transmissible spongiform encephalopathies: TSE), there is considerable phenotypic diversity. Cumulative scientific evidence supports that prions, the infectious agents of prion diseases, are constituted predominantly, if not exclusively, by misfolded, typically protease-resistant, disease-associated isoforms of the prion protein (PrP^res). Consequently, tissue deposition of PrP^res is considered a hallmark of prion disease pathology, and this can be visualized by Western blotting after tissue homogenization and treatment with proteinases, particularly proteinase K (PK). Indeed, Western blot profiles of PrP^res are utilized as one marker of different prion strains, with such strains thought to contribute to at least part of the phenotypic variation observed in sporadic human prion disease. Typically, Western blotting of PrP^res demonstrates three bands of different electrophoretic mobility, depicting the di-glycosylated, mono-glycosylated and unglycosylated species although further subclassification and the delineation of novel sporadic disease subtypes, such as variably protease-sensitive prionopathy, has contributed greater complexity. Nevertheless, it is the mobility of the unglycosylated PrP^res band, the relative abundance of the two glycosylated bands or overall profile of the banding post-PK, in combination with the prion protein gene (PRNP) codon 129 genotype that allows the categorisation of molecular subtypes of sporadic human prion disease. These subtypes appear to correlate with distinct clinico-pathological profiles of sporadic Creutzfeldt-Jakob disease.