Genetic variability of the prion protein gene (PRNP) in thin-tailed and fat-tailed sheep

Scrapie is a deadly neurodegenerative transmissible spongiform encephalopathy (TSE) that affects sheep and goats. TSEs are a consequence of polymorphisms of the prion protein gene PRNP, which result in misfolded prion proteins. They are transmitted through contact with the abnormal proteins (prions). Currently, there are no data regarding the identification of PRNP variability in Indonesian sheep breeds.

This study aimed to identify variants of the PRNP gene and classify the risk of scrapie disease genotypically in thin-tailed and fat-tailed sheep.

DNA isolates from the blood samples of thin-tailed (ET) and fat-tailed (EG) sheep were amplified with the forward primer 5'-AAGCCACATAGGCAGTTGGA-3'and thereverse primer 5'-GAGACACCACCACTACAGGG-3'. A total of 10 samples of polymerase chain reaction products were sequenced and analyzed with molecular evolutionary genetics analysis v.11 software. The data were multiply aligned with comparison samples from GenBank.

We identified 10 nucleotide variations and 11 single-nucleotide polymorphisms at sites 379, 380, 566, 691, and 711. Four codon haplotypes were identified, namely G127A, G127S, G127V, and Q189L, as well as six genotypic variations at codon 127 and two at codon 189. All ET and EG samples had the scrapie codon A136L141R154Q171.

The lack of resistant genotypes and protective alleles in the sheep in this study rendered them less genetically resistant to classical scrapie and more susceptible to atypical scrapie. This is the first study on the identification of PRNP gene variations in sheep in Indonesia. Our results suggest the need for further PRNP research in sheep, especially in Indonesia, to anticipate the risk of a scrapie outbreak and determine the relationship between PRNP variants and phenotypic characteristics of sheep.