PRNP and prion disease: The overexpression of Prnd, especially in PrPC-knockout (PrP0/0) mice, causes progressive ataxia with the Purkinje cell loss in cerebellar folia [3], [19], [20] and demyelination of peripheral nerves [21], suggesting that Dpl, in the absence of PrPC, induces neuropathogenic damages mimicking neurodegeneration, which is different from prion diseases.