Novel Insertion/Deletion Polymorphisms and Genetic Studies of the Shadow of Prion Protein (SPRN) in Raccoon Dogs

Prion diseases, or transmissible spongiform encephalopathies (TSEs), are a group of invariably fatal neurodegenerative disorders. One of the candidate genes involved in prion diseases is the shadow of the prion protein (<i>SPRN</i>) gene. Raccoon dogs, a canid, are considered to be a prion disease-resistant species. To date, the genetic polymorphisms of the <i>SPRN</i> gene and the predicted protein structure of the shadow of prion protein (Sho) have not been explored in raccoon dogs. <i>SPRN</i> was amplified using polymerase chain reaction (PCR). We also investigated the genetic polymorphisms of <i>SPRN</i> by analyzing the frequencies of genotypes, alleles, and haplotypes, as well as the linkage disequilibrium among the identified genetic variations. In addition, <i>in silico</i> analysis with MutPred-Indel was performed to predict the pathogenicity of insertion/deletion polymorphisms. Predicted 3D structures were analyzed by the Alphafold2. We found a total of two novel synonymous single nucleotide polymorphisms and three insertion/deletion polymorphisms. In addition, the 3D structure of the Sho protein in raccoon dogs was predicted to resemble that of the Sho protein in dogs. This is the first study regarding the genetic and structural characteristics of the raccoon dog <i>SPRN</i> gene.