Biodiversity and genetic polymorphisms against scrapie in Sopravissana sheep breed.

Scrapie is a neurodegenerative disease affecting ovine and it is one of several transmissible spongiform encephalopathies (TSEs). Scrapie is recognized as two forms – classical and atypical. Susceptibility or resistance to classical scrapie is strongly regulated by the polymorphisms at codons 136, 154 and 171 of the PRNP gene. Genetic role in atypical scrapie has been described at codons 141 and 154, these ones are involved in the occurrence of the disease at different risk degrees. The aim of this study was to assess the allelic and genotypic frequencies in Sopravissana breed, an endangered autochthon breed of central Italy; in addition, the presence and the frequency of potential protective ARQ allele variants able to increase scrapie resistance by preserving a higher variability of PRNP were evaluated. Three alleles (ARQ, ARR and AHQ) and seven genotypes were observed based on codons 136, 154 and 171 with different frequencies. Moreover, the entire coding sequence of prion protein (PRNP) of the ARQ/ARQ was sequenced; two non-synonymous L141F (23.8%) and H143R (16.7%), also two synonymous polymorphisms (codons 231 and 237) were found. The results showed that the ARQ/ARQ sheep should be considered as a genetic class, which may potentially include animals with different scrapie susceptibility because of the presence of additional polymorphisms. This may allow the application of alternative strategies for breeding programmes in this endangered breed. [ABSTRACT FROM AUTHOR]