Polymorphisms of the prion protein gene in Italian patients with Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob disease (CJD) is a transmissible neurodegenerative disorder characterized by the accumulation of the amyloid protein PrP in the CNS. Two coding polymorphisms of the PrP gene (PRNP) are a methionine (Met) to valine (Val) change at codon 129, and a deletion in the octapeptide coding region. In the United Kingdom, homozygosity at codon 129 appears to be associated with a predisposition to develop CJD. However, in Japan, where allelic frequencies and genotype distribution are significantly different, such an association has not been demonstrated. To determine whether such deletion(s) or codon 129 polymorphisms of PRNP predispose to the development of CJD in Italian patients, 31 sporadic CJD patients with no known PRNP mutations, and 186 unrelated control subjects were studied. Genotypic frequencies at codon 129 in these Italian CJD patients revealed a significant excess of methionine alleles, and a different genotype distribution in comparison with the normal Italian population. Deletions of a 24-bp segment located in the PrP octapeptide coding region were found in two control subjects, but in none of the sporadic CJD patients. These data suggest that Met homozygosity at codon 129 may contribute, with other environmental or endogenous factors, to CJD development.