Susceptibility to scrapie in sheep depends on the host PrP genotype. No data about the linkage of the rare ARK allele to differential scrapie susceptibility are currently available. Several tissues isolated from sheep from an Italian scrapie outbreak and carrying the ARK allele were examined for the presence of the pathological prion protein. A weak positivity was detected only by Western blot in the brainstem of one ARK/ARH sheep. This result shows that the ARK allele does not confer full resistance against scrapie and that the allele needs to be studied further before it can be considered for breeding purposes.
"Due to its rarity, knowledge about the role of this allele in classical scrapie susceptibility is very poor. Acutis et al. (2006) analyzed tissues of sheep carrying the ARK allele in the course of an Italian scrapie outbreak and observed weak classical scrapie positivity in one sheep. However, that sheep carried another rare allele (ARH), making it difficult to understand which of the two was more influential in classical scrapie susceptibility. "
[Show abstract][Hide abstract] ABSTRACT: This study investigated classical scrapie susceptibility in four native Italian sheep breeds
(Lamon, Brogna, Alpagota, Foza) through PrP genotyping. The investigation revealed that
the majority of animals overall showed moderate to high susceptibility to classical scrapie.
The Lamon and Brogna breeds exhibited the highest frequency of the highly susceptibleVRQ
allele (38.1% and 19.3%, respectively), while the Alpagota and Foza had a high frequency
of the ARQ allele (85% and 64%, respectively), also considered to confer susceptibility. The
Foza breed showed a significantly high frequency (P < 0.01) of the rare ARK allele (9.7%);
a similar frequency has never been described before in the literature. This study stresses
the importance of genotyping native sheep breeds both to better organize conservation
schemes and to assess the risk of contracting classical scrapie. Additionally, the investigated
native breeds revealed some characteristics that could be interesting for research purposes.
These sheep could in fact be used to investigate the susceptibility of the ARK allele to
classical scrapie, but also to determine whether its relatively high frequency is indicative
that the origin of the Foza breed differs from the other Venetian sheep breeds.
Small Ruminant Research 06/2013; 113(2-3):323-328. DOI:10.1016/j.smallrumres.2013.03.009 · 1.13 Impact Factor
"Interestingly, the TRQ allele was observed only in Chios sheep, whereas the ARK allele was found in Ki > vi > rci > k sheep. Although this ARK rare haplotype allele was found together with the ARH allele by Acutis et al. (2006) in one scrapie-positive sheep, in this study we found it together with ARQ, as was described by Portela et al. (2006). Gootwine et al. (2008) also detected the ARK allele in the Awassi breed of sheep, but only as homozygotes. "
[Show abstract][Hide abstract] ABSTRACT: Scrapie, a transmissible spongiform encephalopathy (TSE) or prion disease, is a fatal, neurodegenerative disease in sheep and goats. This disease has been known in Europe for more than 250 years. Susceptibility to scrapie is associated with polymorphisms in the sheep prion protein gene (PrP) gene. In sheep, polymorphism in the PrP gene has been identified at a number of codons, and polymorphisms at codons 136, 154 and 171 have reported linkage with susceptibility to scrapie. Polymorphisms at the PrP locus were studied in 413 animals representing three native sheep breeds (Imroz, Chios and Kıvırcık) in Turkey. Genomic DNA was obtained from blood, and genotypes were screened using PCR and direct DNA sequencing. We report 17 genotypes derived from seven different alleles. The most frequent genotype in the Kıvırcık sheep is ARQ/ARQ, whereas the ARR/ARQ genotype is predominant in the Chios and Imroz breeds. In general, the ARQ haplotype was the predominant haplotype. ARQ haplotype was also predominant in the Kıvırcık and Chios sheep breeds, whereas the Imroz sheep predominantly had the ARR haplotype. The susceptibility-associated VRQ haplotype was found in 2.38%, 0.35% and 0.81% of the Imroz, Kıvırcık and Chios sheep, respectively. Moreover, seven additional polymorphisms have been detected at codons G127S, G127V, H143R, G145S, Y172D, N174Y and Q189L. Among these polymorphisms, the N174Y allele is a novel polymorphism, and the G145S allele is a novel allele for a known polymorphic locus.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.