PRNP and prion disease: Prion diseases are a heterogeneous class of rare fatal neurodegenerative diseases caused by the abnormal misfolding of the ‘cellular’ prion protein (PrPC) into the transmissible ‘scrapie-type’ prion form (PrPSc) (Collinge, 2016; DeArmond and Prusiner, 1995; Halliday et al., 2014; Prusiner, 1991, 1998; Prusiner et al., 1990; Weissmann, 2004).