Analysis of the PRNP gene polymorphisms in healthy Greek sheep during 2012 – 2016

Abstract

ABSTRACT. Scrapie is a slowly progressive infectious disease of sheep and goats that causes degeneration of the central nervous system. Scrapie is one of several transmissible spongiform encephalopathies (TSEs), like the bovine spongiform encephalopathy (BSE). In sheep, polymorphisms at codons 136, 154 and 171 of the host gene PRPN that encodes the PrP protein, are known to be closely linked to susceptibility or resistance to natural and experimental classical scrapie. In many countries, but not in Greece, breeding programs have been implemented to increase genetic resistance. This study was supported mainly by the private initiatives of farmers willing to improve their flocks by increasing the resistance to scrapie. Thus, the PrP genotypes (of the three mentioned codons) from 5815 blood samples of clinically healthy rams from 160 healthy flocks during the period 2012 -2016 were determined. Additionally, 1399 blood samples were genotyped only for the 171 codon. Samples were analyzed by Real Time PCR (TaqMan probes) with specific labeled probes. Our results showed an increased percentage of the two genotypes, ARR/ARR and ARR/ ARQ linked with resistance to the disease (27.29% and 34.6%, respectively) and relatively reduced percentage of the genotype ARQ/ARQ (24.23%) which is associated with susceptibility to disease and is the most common genotype in the Greek flocks. This joined effort has resulted in the establishment of an important number of farms with an increased population of genetically resistant rams to classical scrapie.

Polymorphisms of Codons 110, 146, 211 and 222 at the Goat PRNP Locus and Their Association with Scrapie in Greece

“…The main constituent of the infectious agent is an aberrant isoform (PrP Sc ) of the normal cellular (PrP C ) prion protein (PrP), which is a cell–surface glycoprotein. The transmission and the incubation period of the disease depend on the exposure to the infectious agent, the scrapie strain, and the genetic background of the host [ 7 ]. In sheep, the polymorphisms at codons 136, 154, and 171 are known to be closely linked with susceptibility to natural and experimental scrapie, which have been utilized in the European countries for the implementation of national breeding programs to control scrapie.…”

Genetic improvement of indigenous Greek sheep and goat breeds

“…More than 25 PRNP genotypes have been detected in indigenous Greek sheep indicating high levels of genetic variation. Genotypes of risk groups 1 and 2, which are less susceptible to classical scrapie, have been reported in largely ranging frequencies (4.31 -40% and 6.7 -71.4% for risk groups 1 and 2, respectively) in both purebred and crossbred Greek sheep (Billinis et al, 2004;Ekateriniadou et al, 2007a;2007b;Boukouvala et al, 2018). No significant associations of PRNP genotypes with milk production and reproduction traits have been found in Chios sheep, indicating that selection for scrapie resistance is not expected to ad-J HELLENIC VET MED SOC 2020, 71 1ΠΕΚΕ 2020, 71(1)…”