Fatal Familial Insomnia - The Prion

The Prion

Gene PRNP that provides instructions for making the prion protein PrPC is located on the short (p) arm of chromosome 20 at position p13. Both FFI patients and those with Creutzfeldt-Jakob disease carry a mutation at codon 178 of the prion protein gene. FFI is invariably linked to the presence of the methionine codon at position 129 of the mutant allele, whereas CJD is linked to the presence of the valine codon at that position. "The disease is where there is a change of amino acid at position 178 when an asparagine (N) is found instead of the normal aspartic acid (D). This has to be accompanied with a methionine at position 129."