Prion Protein Codon Implicated in Resistance in Dogs Detected in Non-Domesticated Members of Mammalia

Transmissible spongiform encephalopathies (TSE) are fatal neurodegenerative diseases caused by the misfolding of proteins generated in the exon 3 region of the prion protein gene (PRNP). Recent investigations using protein misfolding cyclic amplification assays indicated that some canids displayed a low susceptibility to TSE due to a specific nonsynonymous substitution (human: N159D/E; canid: N163D/E; alignment herein: N302D/E) in the prion protein that may confer protection against prion seeding activity and propagation. To examine the molecular evolution underlying this observation, we determined the mammalian taxonomic distribution of the N159D/E substitution in 882 PRNP sequences representing 26 Orders, 132 families, and 686 species. Two families each in Carnivora (Canidae and Mustelidae) and Chiroptera (Mormoopidae and Vespertilionidae), and one family each in Artiodactyla (Moschidae) and Rodentia (Erethrizontidae), possessed N159D/E that has been reported to confer resistance to TSEs. Although no direct evidence linked a pattern of resistance (phylogenetic relatedness, geographic location, etc.) in these diverse species, it may be that coevolutionary pressures led 53 of the examined 686 species (1 domestic species, 52 wild species) to possess N159D/E. Therefore, the presence of N159D/E may not be the only factor in determining sensitivity to prion diseases; consequently, a more detailed investigation into the 53 species, such as knockout experiments, is warranted.