Fatal familial insomnia (FFI) and a subtype of familial Creutzfeldt-Jakob disease (CJD178) are two prion diseases that have different clinical and pathological features, the same aspartic acid to asparagine mutation (D178N) at codon 178 of the prion protein (PrP) gene, but distinct genotypes generated by the methionine-valine polymorphism at codon 129 (129M or 129V) in the mutant allele of the PrP gene. The D178N, 129M allele segregates with FFI while the D178N, 129V allele segregates with CJD178. The proteinase K resistant PrP (PrP(res)) isoforms present in FFI and CJD178 differ in degree of glycosylation and size. Thus, the amino acid, methionine or valine, at position 129 of the mutant allele, in conjunction with D178N mutation results in significant alterations of PrP(res) in FFI and CJD178. The 129 polymorphic site also exerts influence through the normal allele: the course of the disease is shorter in the patients homozygous at codon 129 and other minor but consistent phenotypic differences occur between homozygous and heterozygous FFI patients. The comparative study of PrP(res) distribution in FFI homozygotes and heterozygotes at codon 129 has lead to the conclusion that the phenotypic, differences observed between these two FFI patient populations may be the result of different rates of conversion of normal PrP into PrP(res), at least in some brain regions.
|Number of pages||9|
|Publication status||Published - 1995|
ASJC Scopus subject areas
- Pathology and Forensic Medicine