Genetic variability of the prion protein gene (PRNP) in wild ruminants from Italy and Scotland

Abstract

The genetics of the prion protein gene (PRNP) play a crucial role in determining the relative susceptibility to transmissible spongiform encephalopathies (TSEs) in several mammalian species. To determine the PRNP gene variability in European red deer (Cervus elaphus), roe deer (Capreolus capreolus) and chamois (Rupicapra rupicapra), the PRNP open reading frame from 715 samples was analysed to reveal a total of ten single nucleotide polymorphisms (SNPs). In red deer, SNPs were found in codons 15, 21, 59, 78, 79, 98, 136, 168 and 226. These polymorphisms give rise to 12 haplotypes, and one of which is identical to the PRNP of American wapiti (Rocky Mountain elk, Cervus elaphus nelsoni). One silent mutation at codon 119 was detected in chamois and no SNPs were found in roe deer. This analysis confirmed that European wild ruminants have a PRNP genetic background that is compatible with TSE susceptibility, including chronic wasting disease.

Fig. 1

Novel noncoding single nucleotide polymorphisms (SNPs) at codons 15, 21 and 78 in the red deer PRNP. Electropherograms show one homozygous (codon 15) and three heterozygous (codons 21 and 78) genotypes. The SNP at codon 15 was detected only in homozygosis in this study.

Fig. 2

The phylogenetic tree of similarity among the PRNP gene sequences of the analysed wild ruminants and other wild and domestic ungulates. The following representatives of the suborder Ruminantia have been included in the analysis: mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus), fallow deer (Cervus dama), mouflon (Ovis musimon), goat (Capra hircus), Alpine ibex (Capra ibex), sheep (Ovis aries) and cow (Bos taurus). The GenBank accession numbers of the reference PRNP sequences are indicated. Bootstraps values > 50 (1,000 replicates) are indicated at the internal nodes. The length of each pair of branches represents the distance between sequence pairs. The scale bar represents the percentage of nucleotide differences.