A hallmark of prion diseases or transmissible spongiform encephalopaties is the conversion of the cellular prion protein (PrPC), expressed by the prion gene (prnp), into an abnormally folded isoform (PrPSc) with amyloid-like features that causes scrapie in sheep among other diseases. prnp together with prnd (which encodes a prion-like protein designated as Doppel), and prnt (that encodes the prion protein testi...