Polymorphism of Prion Protein Gene and Evaluation on Genetic Risk for Scrapie in Three Native and One Introduced Breed in the Republic of North Macedonia

Abstract

Transmissible spongiform encephalopathy in sheep is known as scrapie. Polymorphisms at codons 136, 154, and 171 of the prion protein (PRNP) gene are associated with resistance or susceptibility to the disease. Based on allele combinations, sheep are classified into five genetic risk groups. The aim of this study was to determine the distribution of PRNP gene polymorphisms and assess the genetic susceptibility to scrapie among native and introduced sheep breeds reared in North Macedonia. A total of 309 unrelated animals from three native Pramenka-type sheep breeds, Karakachanian (n=92), Ovchepolian (n=91), and Sharplaninian (n=34), and one introduced breed, Awassi (n=92), were genotyped. The Awassi and Sharplaninian breeds were dominated by the ARQ/ARQ genotype (R3). In Karakachanian sheep, the ARR/ARQ genotype (R2) was most frequent, while Ovchepolian sheep showed equal predominance of ARR/ARQ (R2) and ARQ/ARQ (R3). High-risk genotypes (R4 and R5) were detected only in the Ovchepolian and Sharplaninian breeds. The ARQ allele was the most frequent in Awassi (0.7609), Ovchepolian (0.4945), and Sharplaninian (0.5000), whereas the ARR allele predominated in Karakachanian sheep (0.5772). The VRQ allele was detected only in the Ovchepolian and Sharplaninian breeds. These findings demonstrate genetic differences among the studied sheep populations and provide valuable information for breeding strategies aimed at increasing resistance to scrapie while conserving breed diversity.