AMINO-ACID POLYMORPHISMS OF PRP WITH REFERENCE TO ONSET OF SCRAPIE IN SUFFOLK AND CORRIEDALE SHEEP IN JAPAN

We investigated the relationships between amino acid polymorphisms of the prion protein (PrP), restriction fragment length polymorphisms (RFLP) of the PrP gene and the incidence of natural scrapie in Japan. Six variant alleles of the PrP gene were found in healthy sheep. Based on the substitutions at codons 112, 136, 154 and 171, these allelic variants were designated PrPMARQ, PrPTARQ, Prp(MVRQ), PrPMAHQ, PrPMARR and prp(MARH). Each RFLP haplotype (e1h1, e1h2 or e3h1) consisted of multiple alleles including PrPMARQ. Three of these variant alleles were found in scrapie-affected Suffolk sheep. PrPMARQ was associated with high disease incidence, PrPTARQ and PrPMARR were associated with low disease incidence. We found that one scrapie-affected Suffolk was homozygous for PrPMARR and four PrPSc-positive Suffolks carried PrPMVRQ. Both of two scrapie-affected Corriedales and two out of three scrapie-affected cross-breeds between Suffolk and Corriedale carried PrPMARH, suggesting that this allele associates with high incidence of scrapie in Corriedale and its cross-breeds.