Moreover, the PRNP M129V genotype, in combination with the type of disease-associated prion protein (PrPsc) deposited in the brain, is a strong modulator of the clinical phenotype of sporadic [2-6] and genetic forms [7] and also susceptibility to variant CJD (vCJD). The gene discussed is PRNP; the disease is variant Creutzfeldt-Jakob disease.