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From: TSS ()
Subject: A major genetic component of BSE susceptibility
Date: October 17, 2006 at 2:05 pm PST

Research article

A major genetic component of BSE susceptibility

Katrin Juling*1, Hermann Schwarzenbacher1, John L Williams2,3 and

Ruedi Fries1

Address: 1Chair of Animal Breeding, Technical University of Munich, Hochfeldweg 1, 85354 Freising-Weihenstephan, Germany, 2Division of

Genetics and Genomics, Roslin Institute, Roslin, Midlothian EH25 9PS, UK and 3CERSA, Parco Tecnologico Padano, Via Einstein 26900 Lodi, Italy

Email: Katrin Juling* -; Hermann Schwarzenbacher -;

John L Williams -; Ruedi Fries -

* Corresponding author


Background: Coding variants of the prion protein gene (PRNP) have been shown to be major

determinants for the susceptibility to transmitted prion diseases in humans, mice and sheep.

However, to date, the effects of polymorphisms in the coding and regulatory regions of bovine

PRNP on bovine spongiform encephalopathy (BSE) susceptibility have been considered marginal or

non-existent. Here we analysed two insertion/deletion (indel) polymorphisms in the regulatory

region of bovine PRNP in BSE affected animals and controls of four independent cattle populations

from UK and Germany.

Results: In the present report, we show that two previously reported 23- and 12-bp insertion/

deletion (indel) polymorphisms in the regulatory region of bovine PRNP are strongly associated

with BSE incidence in cattle. Genotyping of BSE-affected and control animals of UK Holstein,

German Holstein, German Brown and German Fleckvieh breeds revealed a significant

overrepresentation of the deletion alleles at both polymorphic sites in diseased animals (P = 2.01

◊ 10-3 and P = 8.66 ◊ 10-5, respectively). The main effect on susceptibility is associated with the 12-

bp indel polymorphism. Compared with non-carriers, heterozygous and homozygous carriers of

the 12-bp deletion allele possess relatively higher risks of having BSE, ranging from 1.32 to 4.01 and

1.74 to 3.65 in the different breeds. These values correspond to population attributable risks

ranging from 35% to 53%.

Conclusion: Our results demonstrate a substantial genetic PRNP associated component for BSE

susceptibility in cattle. Although the BSE risk conferred by the deletion allele of the 12-bp indel in

the regulatory region of PRNP is substantial, the main risk factor for BSE in cattle is environmental,

i.e. exposure to feedstuffs contaminated with the infectious agent.



In this study we presented significant association between

PRNP promoter indel polymorphisms and the BSE status

in three of four investigated cattle populations (Figure 1,

Table 1 and Table 2). We conclude that the main effect on

BSE susceptibility seems to result from the 12-bp indel.

The causality of either or both polymorphism cannot be

verified in this study, however our data highlight that the

12 bp deletion allele is associated with increased risk for

an animal to succumb to feed-borne BSE (Table 4 and Figure

4). Thus, our findings show a substantial genetic component

for the susceptibility of cattle to BSE, conferred by

variants in the regulatory region of PRNP, a gene that has

been shown to be involved in prion disease susceptibility/

resistance in other species. However, the different dimensions

of the BSE epidemic in UK and Germany, on the one

hand, and the similar frequencies of the PRNP-associated

susceptibility alleles in UK and German cattle, on the

other, indicate, that the main BSE risk factor for cattle is

environmental, i.e. exposure to contaminated feed, and

not genetic.



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