The First Genetic Characterization of the SPRN Gene in Pekin Ducks (Anas platyrhynchos domesticus)

The shadow of prion protein (Sho) encoded by the shadow of prion protein gene (SPRN) has been implicated in prion disease biology. Here, we identified the SPRN gene sequence and characterized its genetic polymorphisms in ducks. As a result, the duck and chicken Sho amino acid sequences shared 100% identity. Notably, we found an abundance of single nucleotide polymorphisms in the open reading frame of duck SPRN gene, which is comparable to those in prion disease-susceptible species. To date, there has been no evidence of prion disease in ducks to our knowledge. Given that our previous study on the duck prion protein gene suggested several characteristics of potential prion disease susceptibility, this study supports the need for additional experiments to examine the risk of developing prion diseases in ducks. Prion diseases are fatal neurodegenerative disorders characterized by an accumulation of misfolded prion protein (PrPSc) in brain tissues. The shadow of prion protein (Sho) encoded by the shadow of prion protein gene (SPRN) is involved in prion disease progress. The interaction between Sho and PrP accelerates the PrPSc conversion rate while the SPRN gene polymorphisms have been associated with prion disease susceptibility in several species. Until now, the SPRN gene has not been investigated in ducks. We identified the duck SPRN gene sequence and investigated the genetic polymorphisms of 184 Pekin ducks. We compared the duck SPRN nucleotide sequence and the duck Sho protein amino acid sequence with those of several other species. Finally, we predicted the duck Sho protein structure and the effects of non-synonymous single nucleotide polymorphisms (SNPs) using computational programs. We were the first to report the Pekin duck SPRN gene sequence. The duck Sho protein sequence showed 100% identity compared with the chicken Sho protein sequence. We found 27 novel SNPs in the duck SPRN gene. Four amino acid substitutions were predicted to affect the hydrogen bond distribution in the duck Sho protein structure. Although MutPred2 and SNPs&GO predicted that all non-synonymous polymorphisms were neutral or benign, SIFT predicted that four variants, A22T, G49D, A68T, and M105I, were deleterious. To the best of our knowledge, this is the first report about the genetic and structural characteristics of the duck SPRN gene.