Effects of polymorphisms in ovine and caprine prion protein alleles on cell-free conversion

Abstract

In sheep polymorphisms of the prion gene (PRNP) at the codons 136, 154 and 171 strongly influence the susceptibility to scrapie and bovine spongiform encephalopathy (BSE) infections. In goats a number of other gene polymorphisms were found which are suspected to trigger similar effects. However, no strong correlation between polymorphisms and TSE susceptibility in goats has yet been obtained from epidemiological studies and only a low number of experimental challenge data are available at present. We have therefore studied the potential impact of these polymorphisms in vitro by cell-free conversion assays using mouse scrapie strain Me7. Mouse scrapie brain derived PrPSc served as seeds and eleven recombinant single mutation variants of sheep and goat PrPC as conversion targets. With this approach it was possible to assign reduced conversion efficiencies to specific polymorphisms, which are associated to low frequency in scrapie-affected goats or found only in healthy animals. Moreover, we could demonstrate a dominant-negative inhibition of prion polymorphisms associated with high susceptibility by alleles linked to low susceptibility in vitro.

Caprine PrP variants harboring Asp-146, His-154 and Gln-211 alleles display reduced convertibility upon interaction with pathogenic murine prion protein in scrapie infected cells

“…Structural studies on PrP SC molecules representing either the 22L or the Me7 strain, indicated conformational differences mainly associated with beta sheets, 59 suggesting potentially different interactions with the variants under study, that could possibly influence the effectiveness of subsequent conversion. Moreover, the profound discrepancy regarding the Lys-222 variant performance, which did not show significantly lower conversion relative to wild-type in our study as opposed to almost complete absence of conversion in the study of Eiden and colleagues, 24 could also be explained by previously reported differences in prion strains' behavior upon interaction with PrPs of the same sequence. 60 This further points out the importance of assessing a specific variant relative to several strains, in order to safely assess its protective effect against scrapie.…”

“…Similar to another cell-free conversion study, 24 our data indicate that the Asp-146, His-154 and Gln-211 variants are linked with protection against scrapie, albeit they are assigned with different conversion efficiencies in each experimental approach. These differences may reflect strain-specific (22L and Me7) effects on the tested alleles' conversion.…”

“…11,[21][22][23] These alleles' relative low occurrence frequency among herds and/or goat breeds examined in field studies, suggests that additional investigations within the context of a well defined experimental scheme, including sufficient test samples and controls, are required prior to gaining further conclusive information on their effects. Different experimental approaches, utilizing either in vitro 24 or in vivo [25][26][27][28] methodologies, have been used toward this direction.…”

“…The in vitro approach utilized a cellfree system to estimate the conversion potential of several alleles. 24 In parallel, in vivo studies were initialized on either transgenic mice harboring caprine Prnp alleles, 25 or on experimentally challenged goats carrying the genotypes of interest. [26][27][28] In the present work we report the in vitro study of murine-caprine PrP chimeras consisting of the mature caprine Prnp sequence and carrying the alleles of interest, in a murine cell model of scrapie.…”

Effects of PRNP polymorphisms on sperm quality traits in Chinese Holstein bulls

“…Therefore, the prion protein gene (PRNP) has been studied as a candidate gene for resistance to prion diseases. It had been proved that PRNP polymorphisms had a strong correlation with the resistance to sheep scrapie, and the correlation has been well documented for sheep (Luhken et al 2004;Goldmann 2008;Sweeney & Hanrahan 2008;Eiden et al 2011). In cattle, and the BSE is characterized by the accumulation of an abnormal and protease resistant isoform of prion protein (PrP) in the central nervous system.…”