An amber mutation of prion protein in Gerstmann-Sträussler syndrome with mutant PrP plaques.

We found an amber mutation in the open reading frame of the prion protein (PrP) gene. The codon 145 mutation (tyrosine to stop) was recognized on a PrP allele of a patient with Alzheimer-type clinical course. Pathologic examination revealed many amyloid plaques and neurofibrillary changes. However, the amyloid plaques in this patient were not composed of beta/A4 protein, but of PrP. Both wild and mutant PrP alleles were detected in the cerebral mRNA; however, only C-terminal truncated PrP was detected in the kuru plaques. We herein present evidence that only mutant PrP aggregates to make kuru plaques in the central nervous system.