Worldwide attention has been given to scrapie, because bovine spongiform encephalopathy (BSE) could be experimentally transmitted to sheep. This ovine form of BSE was clinically identical to scrapie. In Japanese scrapie cases, a majority of the diseased sheep were from Suffolk, while 8 cases were from Corriedale. It is very likely that sheep-to-sheep transmission of scrapie has taken place in Obihiro, Hokkaido. Normal prion protein may play a role in the morphoregulatory signaling pathway, which orchestrates the specificity of a particular cellular response. Over-expression of normal prion protein in mice cause neurodegenerative disorders. Recently, Prnd was identified downstream of the mouse prion protein gene (Prnp), and encodes 179 amino acids and a prion protein (PrP)-like protein designated doppel (Dpl). Dpl was upregulated in the central nervous system of two PrP-deficient lines of mice, as well as in prionless cell lines. Dpl caused neurodegeneration similar to that caused by PrP. Linked expression of Prnp and Prnd may cause several neurodegenerative disorders.