Evaluation of genetic variations of the PRNP gene in Mehraban and Romanov sheep breeds

This study was conducted to investigate the polymorphisms of the Prion protein gene (PRNP) exon 3 in Mehraban and Romanov sheep. Blood samples were collected from 124 sheep (85 Mahraban and 39 Romanov). After DNA extraction, polymerase chain reactions (PCR) were performed to amplify a 173 bp fragment of the PRNP gene exon 3 using a specific pair of primers. Polymorphisms of the studied fragments were explored using single strand conformational polymorphism (SSCP) and DNA sequencing analysis. In both Mehraban and Romanov breeds, three different banding patterns (AA, AG and GG genotypes) along with a single nucleotide polymorphism (g.625A>G) were identified, that deduced one amino acid substitution (p.171R>Q). Three haplotypes including ARR/ARR, ARR/ARQ and ARQ/ARQ were identified, which the most frequency (61.2 and 46.15% in Mehraban and Romanov breeds, respectively) was related to the ARR/ARR haplotype with high resistance to scrapie disease. The results of current study regarding the similarity of polymorphism in PRNP gene of domestic and foreign breeds could be used in sheep breeding programs.