Genotyping of PRNP coding region for scrapie in Indian sheep

Prions are unprecedented infectious pathogens that cause a group of invariably fatal neurodegenerative disease by an entirely novel mechanism. The conformational change in prion proteins results in a change from a predominantly α-helical protein to a β-sheet form, which causes scrapie in sheep and goat. The present study was carried out to identify polymorphisms of the prion protein gene (PrP) at the codons (136, 154 and 171) responsible for the susceptibility and resistance of the scrapie disease in the sheep. TheARQ is the most frequent allele which is less susceptible, but may get scrapie. The highly sensitive VRQ and resistant ARR alleles were not present in the Mandya sheep. Genotype ARQ/ARQ, ARQ/AHQ, and AHQ/AHQ were found in the analyzed population with 40.00, 40.00 and 20.00% respectively, showing little resistance to scrapie and require careful selection when used for breeding. Six groups (variants) were found in SSCP (single-strand conformation polymorphism) i.e., out of each group one sample was sequenced. Sequencing (accession No. KF207876-79) of samples allowed the identification of 5 other new polymorphisms on PrPgene at codon positions 98(S/R), 147(D/E), 175(Q/R), 184(N/H) and 189(Q/L). Absence of ARR allele in the Mandya sheep should be taken into considerationfor the implementation of a preventive selection programme to avoid erosion of the genetic stock.