Variation in the prion protein gene (PRNP) sequence of wild deer in Great Britain and mainland Europe

Amy L Robinson,Mariella E Güere,Helene Tharaldsen,Fiona Houston,Josephine M Pemberton,Wilfred Goldmann,Sílvia Pérez-Espona,Helen Williamson,Stephanie L Smith,Jarmila Krojerová-Prokešová,Karis Baker

doi:10.1186/s13567-019-0675-6

Abstract

Susceptibility to prion diseases is largely determined by the sequence of the prion protein gene (PRNP), which encodes the prion protein (PrP). The recent emergence of chronic wasting disease (CWD) in Europe has highlighted the need to investigate PRNP gene diversity in European deer species, to better predict their susceptibility to CWD. Here we report a large genetic survey of six British deer species, including red (Cervus elaphus), sika (Cervus nippon), roe (Capreolus capreolus), fallow (Dama dama), muntjac (Muntiacus reevesii), and Chinese water deer (Hydropotes inermis), which establishes PRNP haplotype and genotype frequencies. Two smaller data sets from red deer in Norway and the Czech Republic are also included for comparison. Overall red deer show the most PRNP variation, with non-synonymous/coding polymorphisms at codons 98, 168, 226 and 247, which vary markedly in frequency between different regions. Polymorphisms P168S and I247L were only found in Scottish and Czech populations, respectively. T98A was found in all populations except Norway and the south of England. Significant regional differences in genotype frequencies were observed within both British and European red deer populations. Other deer species showed less variation, particularly roe and fallow deer, in which identical PRNP gene sequences were found in all individuals analysed. Based on comparison with PRNP sequences of North American cervids affected by CWD and limited experimental challenge data, these results suggest that a high proportion of wild deer in Great Britain may be susceptible to CWD.

Highlights

Chronic wasting disease (CWD) is a prion disease of cervid species that is widespread in North America and has recently emerged in Europe
The primary aims of this study were (i) to perform a comprehensive survey of the protein-coding sequence of the prion protein gene (PRNP) gene in the six major free-ranging or wild species of deer found in Great Britain (GB) and (ii) to compare the PRNP genotype distributions in British and European populations of red deer, as red deer are one of the most numerous wild species in both GB and mainland Europe, and are an economically important game species due to revenue generated via hunting, tourism and venison production [35]
The open reading frame (ORF) encoded by exon 3 of the PRNP gene is highly conserved among cervid species, and non-synonymous polymorphisms identified in individual species are usually reported as variations from a consensus sequence [25]

Summary

Introduction

Chronic wasting disease (CWD) is a prion disease of cervid species that is widespread in North America and has recently emerged in Europe. It belongs to a family of diseases termed transmissible spongiform encephalopathies (TSEs), which cause progressive and invariably fatal neurodegenerative disorders in humans and animals. CWD was first described in the 1960s as a wasting syndrome of captive mule deer (Odocoileus hemionus hemionus) and black-tailed deer (Odocoileus hemionus columbianus) in Colorado wildlife facilities [1]. The first European case of CWD, and the first natural case in a reindeer (Rangifer tarandus) was identified in Norway in March 2016 [7].

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