Prion Protein Gene (PRNP) Variants and Evidence for Strong Purifying Selection in Functionally Important Regions of Bovine Exon 3
Prion protein gene (PRNP) variants and evidence for strong purifying selection in functionally important regions of bovine exon 3 Christopher M. Seabury†, Rodney L. Honeycutt†‡, Alejandro P. Rooney§, Natalie D. Halbert†, and James N. Derr†¶ †Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4467; ‡Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843-2258; and §National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, Peoria, IL 61604-3999 Communicated by James E. Womack, Texas A&M University, College Station, TX, September 1, 2004 (received for review December 19, 2003) Amino acid replacements encoded by the prion protein gene indel polymorphism has not been observed within the octapep- (PRNP) have been associated with transmissible and hereditary tide repeat region of ovine PRNP exon 3 (8, 10–20), whereas spongiform encephalopathies in mammalian species. However, an studies of cattle and other bovine species have yielded three indel association between bovine spongiform encephalopathy (BSE) and isoforms possessing five to seven octapeptide repeats (20–31). bovine PRNP exon 3 has not been detected. Moreover, little is Despite the importance of cattle both to agricultural practices currently known regarding the mechanisms of evolution influenc- worldwide and to the global economy, surprisingly little is known ing the bovine PRNP gene. Therefore, in this study we evaluated about PRNP allelic diversity for cattle collectively and͞or how the patterns of nucleotide variation associated with PRNP exon 3 this gene evolves in this lineage. In addition, although several for 36 breeds of domestic cattle and representative samples for 10 nondomesticated species of Bovinae contracted transmissible additional species of Bovinae.
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