A single amino acid alteration in murine PrP dramatically alters TSE incubation time.

In order to investigate mutations linked to human TSEs, we have used the technique of gene targeting to introduce specific mutations into the endogenous murine PrP gene which resulted in a P101L substitution (Prnp(a101L)) in the murine PrP gene. This mutation is equivalent to the 102L mutation in the human PrP gene which is associated with Gerstmann-Sträussler syndrome. Since the mutated gene is in the correct chromosomal location and control of the mutant gene expression is identical to that of the wild type murine PrP gene, the precise effect of the 101L mutation in the uninfected and TSE infected mouse can be investigated in this transgenic model. Mice homozygous for this mutation (101LL) while showing no spontaneous TSE disease were more susceptible to TSE disease than wild type mice following inoculation with GSS infectivity. Disease was transmitted from these mice to mice both with and without the Prnp(a101L) allele. The 101L mutation does not therefore produce spontaneous genetic disease in mice but does dramatically alter incubation periods following TSE infection. Additionally, a rapid TSE transmission was demonstrated associated with extremely low amounts of PrP(Sc).