PRNP and human prion disease: Transmissible spongiform encephalopathies (TSE) are a group of neurodegenerative disorders, such as Creutzfeldt-Jakob disease (CJD), which are characterised by the conversion and accumulation of a disease-associated, proteinase K (PK)-resistant, misfolded isoform of the cellular prion protein (PrPC) called scrapie prion protein (PrPSc).