PrP Gene Polymorphism in Medieval Remains of Sicilian Sheep

Stefano Reale1, Mario Cosenza1, Luca Sìneo2, Letizia Arcoleo2, Gabriele Zaffora1, Daniele Macrì1, Fabrizio Vitale1
1Molecular Biology Department, Istituto Zooprofilattico Sperimentale della Sicilia “A. Mirri”, Palermo, Italy 2Laboratory of Anthropology, STEBICEF Department, University of Palermo, Palermo, Italy

Encephalopathy in sheep was at first described in Ireland in 1732 and was called scrapie. Ancient DNA in archaeogenetics represents an effective method to evaluate the ancestral pedigree of living animals and track evolutionary changes occurred between the past and the present day. Since several point mutations are today widely described in modern scrapie, no data about both se- quence and frequency are still available for the prion protein (PrP) gene in ancient breeds. In or- der to evaluate whether the haplotypes distribution in ancient sheep differed from those of the modern population we evaluated polymorphism at four well know codons of the Prp Open Read- ing Frame. In the present work, we collected 37 medieval sheep bone remains found at the Cala- thamet (n = 11), Palazzo Bonagia (n = 12) and Palazzo Steri (n = 14) Sicilians archeological sites and dated back between 9th - 15th century. Single nucleotide polymorphisms (SNPs) at codons 136, 141, 154 and 171 of the prion protein (PrP) were investigated using cycle sequencing. Sequenom Mass ARRAYiPLEX platform confirmed the results for 5 individuals out of 37. Cycle sequencing showed at all samples the AA136LL141RR154QQ171 (hereafter ALRQ/ALRQ) genotype except at 2 in- dividuals showing the very susceptible genotype VLRQ/VLRQ (n = 1) and the resistant (ALRR/ ALRR) (n = 1) respectively. Supported by a high incidence of susceptible genotype to prion infec- tion we concluded that presumably scrapie was already widespread enough in the medieval Sicily. Moreover, we described conceivable scenarios that could have underlain evolutionary changes in the medieval sheep population.