ABSTRACT: Prion disease has displayed large infection host ranges among several species; however, dogs have not been reported to be infected and are considered prion disease-resistant animals. Case-controlled studies in several species, including humans and cattle, indicated a potent association of prion protein gene (PRNP) polymorphisms in the progression of prion disease. Thus, because of the proximal location and similar structure of the PRNP gene among the prion gene family, the prion-like protein gene (PRND) was noted as a novel candidate gene that contributes to prion disease susceptibility. Several case-controlled studies have confirmed the relationship of the PRND gene with prion disease vulnerability, and strong genetic linkage disequilibrium blocks were identified in prion-susceptible species between the PRNP and PRND genes. However, to date, polymorphisms of the dog PRND gene have not been reported, and the genetic linkage between the PRNP and PRND genes has not been examined thus far. Here, we first investigated dog PRND polymorphisms in 207 dog DNA samples using direct DNA sequencing. A total of four novel single nucleotide polymorphisms (SNPs), including one nonsynonymous SNP (c.149G>A, R50H), were identified in this study. We also found two major haplotypes among the four novel SNPs. In addition, we compared the genotype and allele frequencies of the c.149G>A (R50H) SNP and found significantly different distributions among eight dog breeds. Furthermore, we annotated the c.149G>A (R50H) SNP of the dog PRND gene using in silico tools, PolyPhen-2, PROVEAN, and PANTHER. Finally, we examined linkage disequilibrium between the PRNP and PRND genes in dogs. Interestingly, we did not find a strong genetic linkage between these two genes. To the best of our knowledge, this was the first genetic study of the PRND gene in a prion disease-resistant animal, a dog.
