The PRNP gene polymorphism in Rough-coated Pomeranian Landrace sheep
Prion protein (PrP) is a membrane glycoprotein whose abnormal form is believed to cause a group of disorders known as transmissible spongiform encephalopathies (TSEs), which affect the brain and nervous system of both human beings and animals. The most familiar TSEs are Creutzfeldt-Jakob Disease (CJD) in human beings, and bovine spongiform encephalopathy (BSE) and scrapie in sheep and goats. It is well established that resistance or susceptibility to scrapie has a genetic background that is closely linked to amino acid variations within PrP at positions 136 (A/V), 154 (R/H) and 171 (Q/R). The ARR (alanine at codon 136 and arginine at codons 154 and 171) allele is associated with the highest resistance to scrapie, whereas the VRQ allele is linked to the highest susceptibility. In the present study the allelic and genotypic frequencies of the PRNP gene in the Rough-coated Pomeranian Landrace (RPL) were determined. Polymorphisms at codons 136, 154 and 171 were identified with the PCR-RFLP method. Of the eight observed genotypes, ARR/ARQ (35.9%) and ARQ/ARQ (24.4%) were the most frequent. This study reported a presence of AHQ/AHR genotype (2.6%) that has not previously been recorded in any sheep breed. The predominance of wild-type ARQ (46.8%) haplotype, which is linked to the risk of scrapie development, suggested a genetic susceptibility to scrapie in RPL sheep. Although the frequency of ARR/ARR in RPL sheep was low, the highest frequency of the ARR/ARQ genotype could be helpful in increasing the number of individuals carrying the ARR/ARR genotype and reducing the risk of genetic defects within the population.
Keywords: Sheep, scrapie, PRNP gene, polymorphism