Sequence polymorphism of PrP exon 3 gene in Istrian and crossbred sheep

Polymorphisms in sheep PrP (prion protein) gene are known for scrapie susceptibility. We sequenced part of PrP exon 3 gene in 92 autochthonous Istrian (IS) and 38 crossbred sheep (CBS). ARQ, ARR and AHQ alleles were predominant with frequency of 0.674 (0.526), 0.228 (0.132) and 0.082 (0.263) in IS (CBS), respectively, while VRQ (0.011 in IS) and ARH (0.005 in IS and 0.079 in CBS) alleles were rare. We also found non-synonymous mutations at codons 112 (M^T), 127 (G^S) and 143 (H^R), and synonymous mutations at codons 231 (R) and 237 (L). Additional mutations were associated only with AHQ, ARH and ARQ alleles. The polymorphism of PrP gene in IS was not critical with respect to scrapie susceptibility and with some efforts number of "favourable" genotypes can be increased.