Transgenic (Tg) mice with PrP but lack C1 fragments showed accelerated accumulation of pathogenic PrPSc after scrapie inoculation, whereas Tg(C1) mice expressing N-terminally deleted forms (PrP(Δ23–111)) in the absence of endogenous PrP remained completely healthy and did not accumulate PK-resistant PrP after scrapie inoculation [733]. This evidence concerns the gene PRNP and scrapie.