Prion protein gene frequencies in three Sicilian dairy sheep populations

Abstract

The objective of this paper was to investigate the prion protein (PrP) genotype and haplotype frequencies in three Sicilian dairy sheep populations. The three populations were: (1) 1096 Valle del Belice animals, (2) 1143 Comisana animals, and (3) 1771 individuals from 5 flocks with scrapie outbreaks, in which the animals were crossbreds derived from indigenous Sicilian dairy breeds. PrP genotypes are described for the three codons 136 (Alanine or Valine; A, V), 154 (Histidine or Arginine; H, R), and 171 (Glutamine, Arginine or Histidine; Q, R, H) which represent polymorphisms known to be linked with scrapie susceptibility. The Valle del Belice haplotype frequencies were 32.3% ARR, 6.5% AHQ, 1.0% ARH, 58.8% ARQ, and 1.4% VRQ. The Comisana frequencies were 39.4% ARR, 2.9% AHQ, 2.9% ARH, 50.9% ARQ, and 3.9% VRQ. In the flocks with scrapie outbreaks the frequencies were 32.8% ARR, 2.4% AHQ, 1.7% ARH, 59.1% ARQ, and 3.9% VRQ. In all three populations ARQ and ARR were the most frequent haplotypes. Multiple generations of strong selection will be needed to fixate the most resistant ARR haplotype

PrP Gene Polymorphism in Medieval Remains of Sicilian Sheep

“…Moreover, we presumed genetic forces driving evolutionary changes occurred in the ancestral sheep population. The predominant ALRQ haplotypes found in this study are in line with the modern allelic distribution in Sicily [17]. According to the Van Kaam study, currently the ARQ haplotype mean frequency in Sicilians sheep is much higher (56.2%) compared to the resistant ARR (34.8%).…”

“…To date, Italian data on the amino acid frequencies at PrP gene are available and show the prevalence of the ARQ both homozygosis and heterozygosis with the ARR [16]. In the Sicilian sheep the haplotypes distributions follow the same trend as the rest of the Italian population [17] despite the genetic isolation that characterizes the native sheep breeds. Since there are no data available on the ancestral genotype distribution for the Sicilian sheep, through a retrospective study we evaluated PrP allelic profile using aDNA analysis directly from archaeological samples.…”