Submitted to: Genetics Selection Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2008
Publication Date: 8/19/2008
Citation: White, S.N., Hoesing, L.M., O'Rourke, K.I., Waldron, D., Rowe, J., Alverson, J. 2008. Prion gene (PRNP) haplotype variation in United States goat breeds. Genetics Selection Evolution. 40(5):553-561. Interpretive Summary: Scrapie eradication efforts are focused on sheep and cost $18 million annually in the U.S. However, goats can also get scrapie. This study addressed the potential to use goat genetics to reduce scrapie in goats and to limit the risk that goats might maintain scrapie even if it is eradicated in sheep. The prion gene was sequenced in 449 U.S. goats of 10 breeds, most of which had never had their prion gene examined. There were 6 prion gene polymorphisms in these U.S. goats, and 3 of them have been associated with some form of increased scrapie resistance in previous studies. These potential resistance alleles are at low frequencies overall, but they are more common in some breeds than others. This suggests that it should be possible to breed for more scrapie-resistant goats both by using the existing alleles and by breeding in additional variants from other breeds. However, more research is necessary to see whether the resistance alleles convey partial or complete protection from scrapie. Overall, this study examined prion gene alleles in U.S. goats and suggests possible breeding strategies to enhance goat scrapie resistance that could be used to supplement current scrapie eradication efforts.
Technical Abstract: Scrapie eradication efforts cost 18 million dollars annually in the United States and rely heavily upon PRNP genotyping of sheep. Genetic resistance might reduce goat scrapie and limit the risk of goats serving as a scrapie reservoir, so PRNP coding sequences were examined from 446 goats of 10 breeds, 8 of which had not been previously examined at PRNP. The 10 observed alleles were all related to one of two central haplotypes by a single amino acid substitution. At least five of these alleles have been associated with increased incubation time or decreased odds of scrapie. To the best of our knowledge, neither S146 nor K222 have been found in any goats with scrapie, though further evaluation will be required to demonstrate true resistance. S146 was more common, present in several breeds at widely varying frequencies, while K222 was observed only in two dairy breeds at low frequency. These data suggest potential both for selection within breeds and for marker-assisted introgression of alleles between breeds. Overall, this study provided frequency data on PRNP alleles in U.S. goats, showed the pattern of relationships between haplotypes, and suggested possible breeding strategies that might be used to supplement scrapie eradication efforts.