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Perugia, Italy

Curcio L.,Area Ricerca e Sviluppo | Curcio L.,University of Perugia | Sebastiani C.,Area Ricerca e Sviluppo | Ceccobelli S.,University of Perugia | And 3 more authors.
Livestock Science | Year: 2015

Prions are responsible for transmissible spongiform encephalopathies (TSEs), also called scrapie in sheep. Single nucleotide polymorphisms (SNPs) in PRNP have been shown to play a crucial role in terms of incubation period and/or susceptibility to scrapie. Considering codons 136, 154, 171, five main alleles, associated with different degrees of susceptibility to classical scrapie have been detected. Homozygous ARR sheep are resistant to scrapie infection, however this genotype is not so frequent in some breeds. VRQ and ARQ alleles on the other hand are associated with a high susceptibility to scrapie. Additional polymorphisms within the ARQ allele, have been associated with scrapie resistance. Therefore, it is important to assess the frequency of both main and minor allelic variants, in order to develop a breeding programme based on genetic selection that simultaneously, increases scrapie resistance, and maintains a high variability of PRNP. Allelic and genotypic PRNP frequencies, at the three main codons, were determined in four sheep breeds reared in central Italy (Appenninica, Bergamasca, Comisana and Sarda). Moreover homozygous ARQ sheep have been investigated to measure the frequencies of minor allelic variants. In this study the AT112RQ and ARQK176 protective allelic variants were detected. The AT112RQ allele was observed (ranging from 6.3% to 31.8%) in all the analysed breeds with the exception of Sarda sheep. The ARQK176 allele by contrast was observed only in Sarda breed (4.6%). Moreover five non synonymous polymorphisms were also found (Q101R, G127S, L141F, H143R, and H180Y). © 2015 Elsevier B.V.. Source

Curcio L.,Area Ricerca e Sviluppo | Curcio L.,University of Perugia | Sebastiani C.,Area Ricerca e Sviluppo | Di Lorenzo P.,University of Perugia | And 2 more authors.
Animal | Year: 2016

Scrapie is a naturally occurring transmissible spongiform encephalopathy in sheep and goat. It has been known for ~250 years and is characterised by the accumulation of an abnormal isoform of a host-encoded prion protein that leads to progressive neurodegeneration and death. Scrapie is recognised in two forms, classical and atypical scrapie. The susceptibility to both types of scrapie is influenced by polymorphisms of the prion protein gene (PRNP). Sheep susceptibility or resistance to classical scrapie is strongly regulated by the polymorphisms at codons 136, 154 and 171 of the PRNP. The genetic role in atypical scrapie in sheep has been defined by polymorphisms at codons 141, 154 and 171, which are associated with different degrees of risk in the occurrence of the ovine disease. Progress has been achieved in the prevention of scrapie in sheep due to efficient genetic breeding programmes based on eradication and control of the disease. In Europe, the success of these programmes has been verified by applying eradication and genetic selection plans. In general terms, the ovine selection plans aim to eliminate and reduce the susceptible allele and to enrich the resistant allele ARR. During outbreaks all susceptible animals are slaughtered, only ARR/ARR resistant rams and sheep and semi-resistant females are preserved. In the occurrence of scrapie positive goats a complete cull of the flock (stamping out) is performed with great economic loss and severe risk of extinction for the endangered breeds. The ability to select scrapie-resistant animals allows to define new breeding strategies aimed to boost genetic progress while reducing costs during scrapie outbreaks. Allelic variants of PRNP can be protective for caprine scrapie, and the knowledge of their distribution in goats has become very important. Over the past few years, the integration of genetic information on goat populations could be used to make selection decisions, commonly referred to as genetic selection. The objective of this review was to summarise the main findings of polymorphisms of the caprine prion protein (PrP) gene and to discuss the possible application of goat breeding schemes integrating genetic selection, with their relative advantages and limitations. © The Animal Consortium 2016 Source

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