Transgenic mice were also reported to develop a spontaneous neurological disease in the absence of PrPsc when preferentially expressing a transmembrane form of prion protein (PrPCtm) [58], [59], which would imply that CtmPrP is a key component in the pathway of neurodegeneration as in Gerstmann–Sträussler-Scheinker syndrome. The gene discussed is PRNP; the disease is nervous system disorder.