Polymorphism of prion protein gene (PRNP) in Nigerian sheep

Abstract

Polymorphism of the prion protein gene (<i>PRNP</i>) gene determines an animal's susceptibility to scrapie. Three polymorphisms at codons 136, 154, and 171 have been linked to classical scrapie susceptibility, although many variants of <i>PRNP</i> have been reported. However, no study has investigated scrapie susceptibility in Nigerian sheep from the drier agro-climate zones. In this study, we aimed to identify <i>PRNP</i> polymorphism in nucleotide sequences of 126 Nigerian sheep by comparing them with public available studies on scrapie-affected sheep. Further, we deployed Polyphen-2, PROVEAN, and AMYCO analyses to determine the structure changes produced by the non-synonymous SNPs. Nineteen (19) SNPs were found in Nigerian sheep with 14 being non-synonymous. Interestingly, one novel SNP (T718C) was identified. There was a significant difference (<i>P</i> < 0.05) in the allele frequencies of <i>PRNP</i> codon 154 between sheep in Italy and Nigeria. Based on the prediction by Polyphen-2, R154H was probably damaging while H171Q was benign. Contrarily, all SNPs were neutral via PROVEAN analysis while two haplotypes (HYKK and HDKK) had similar amyloid propensity of <i>PRNP</i> with resistance haplotype in Nigerian sheep. Our study provides valuable information that could be possibly adopted in programs targeted at breeding for scrapie resistance in sheep from tropical regions.