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 te chnique of gene targeting to introduce specific mutations into the endogeno us murine PrP gene which resulted in a P101L substitution (Prnpa(101L)) in the murine PrP gene. This mutation is equivalent to the 102L mutation in th e human PrP gene which is associated with Gerstmann-Straussler syndrome. Si nce 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 in fected mouse can be investigated in this transgenic model. Mice homozygous for this mutation (101LL) while showing no spontaneous TSE disease were mor e 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 p roduce spontaneous genetic disease in mice but does dramatically alter incu bation periods following TSE infection. Additionally a rapid TSE transmissi on was demonstrated associated with extremely low amounts of PrPSc.