Prion protein genotypes in Icelandic scrapie flocks: The effect of removing rams with a VRQ allele from Icelandic breeding stations

BMC Seminar Thursday 14 January, 12:00

Speaker: Eva Hauksdóttir, Biomedical scientist M.Sc., working in animal TSE screening at Keldur, the Institute for Experimental Pathology, University of Iceland. 

Title: Prion protein genotypes in Icelandic scrapie flocks: The effect of removing rams with a VRQ allele from Icelandic breeding stations

Zoom link: https://eu01web.zoom.us/j/67259826243

Abstract: Classical scrapie is a contagious, fatal neurodegenerative disease that affects sheep. It has been endemic in Iceland for about 140 years. The infectious agent is a prion, a pathological form (PrP^Sc) of the cellular prion protein, which is expressed by the Prnp gene. The infectivity of PrP^Sc is influenced by Prnp genotypes of the host, as they convey different resistance/susceptibility to classical scrapie. In 2008, Iceland had removed all rams carrying a V₁₃₆R₁₅₄Q₁₇₁ allele, which is most susceptible to classical scrapie, from the country’s breeding stations. The aim of this study was to assess the effect of removing VRQ-allele-carrying rams from Icelandic sheep breeding stations on the distribution of Prnp genotypes in classical scrapie flocks and their clinical suspect index samples, as well as the age of the index samples. Classical scrapie flocks, as well as their clinical suspect index samples, from the years 2010-2019 (n = 1450 and 10, respectively) were compared to 1998-2007 (n = 1081 and 32, respectively). The process for genotyping samples was DNA isolation, PCR, RFLP and electrophoresis. The age of the index cases was obtained from their ear tags. A significant difference was detected in the frequency of the corresponding amino acids at codons 136 and 154 (p < 0.0001 for both) in the classical scrapie flocks. However, there was no difference when comparing codons 136 (p = 0.9784) and 154 (no polymorphism) or age (p = 0.2808) between the clinical suspect index samples. The results imply that the removal of VRQ-allele-carrying rams from the breeding stations has brought about a change in the genetic variance of Prnp in classical scrapie flocks.