Abstract
Scrapie is a fatal neurodegenerative disorder of sheep and goats caused by post-translational conformational change in the host-encoded prion protein (PrPC). Susceptibility or resistance to scrapie has been associated with the presence of polymorphisms in the prion protein (PrP) gene. In the present study, we analyzed the PrP gene sequence to determine the frequency of polymorphisms in 56 sheep (28 each from Damani and Hashtnagri breeds) and 56 goats (28 each from Kamori and Local Hairy breeds). A total of 7 amino acid polymorphisms were detected in the PrP gene for sheep and 4 for goats. These amino acid polymorphisms were combined in 13 alleles and 15 genotypes in sheep and 5 alleles and 6 genotypes in goats. The overall frequency of the most sheep scrapie-resistant polymorphism (Q171R) was calculated to be 0.107. The most scrapie-susceptible polymorphism (A136V) was not detected in any of the studied sheep. The overall frequency of scrapie-associated polymorphism (H143R) in goats was found to be 0.152. Along with already known amino acid polymorphisms, two novel polymorphisms were also detected for each of sheep (Q171N and T191I) and goats (G22C and P63L). However, the overall frequency of these polymorphisms was extremely low.
Highlights
Scrapie in sheep and goats is the most ancient form among a group of chronic neurodegenerative disorders cumulatively known as prion diseases or transmissible spongiform encephalopathies (TSEs)
The unconventional etiology of TSEs is associated with the conversion of a normal hostencoded prion protein (PrPC-Cellular) to abnormal pathogenic conformers (PrPSc-Scrapie) which get accumulated in the brain and lymphoid organs of cases in the form of fibrillar aggregates [2]
Sequencing of the PrP gene showed seven amino acid polymorphisms in two sheep breeds (Damani and Hashtnagri) and four in two goat breeds (Kamori and Local Hairy) of Pakistan (Table 1). These amino acid polymorphisms were combined in 13 alleles and 15 genotypes in sheep and 5 alleles and 6 genotypes in goats
Summary
Scrapie in sheep and goats is the most ancient form among a group of chronic neurodegenerative disorders cumulatively known as prion diseases or transmissible spongiform encephalopathies (TSEs). TSEs other than scrapie include Cruetzfeldt-Jacob disease in humans, chronic wasting disease in deer and elk, mad cow disease in cattle and transmissible mink encephalopathy [1]. The unconventional etiology of TSEs is associated with the conversion of a normal hostencoded prion protein (PrPC-Cellular) to abnormal pathogenic conformers (PrPSc-Scrapie) which get accumulated in the brain and lymphoid organs of cases in the form of fibrillar aggregates [2]. The detection of PrPSc in relevant tissues is regarded as the major diagnostic marker for the clinical evaluation of TSEs [3]. The major concerns about TSEs are multiple
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