1a.Objectives (from AD-416):
The objective of this cooperative research project is to investigate the influence of the bovine Prnp gene polymorphisms, E211K, on the susceptibility to BSE. Specifically, the research project will provide 134 embryos that will be used to generate approximately 62 animals, 31 of which will contain the rare allele for the purposes BSE research.
This ongoing SCA with Iowa State University to produce cattle with the E211K Prnp allele for BSE research has resulted in an E211/K211 heterozygous bull. We are now in the unique position to extend our research on this allele to include animals homozygous for K at position 211. Based upon our understanding of this novel polymorphism one would predict homozygotes would have a more rapid onset of clinical signs associated with genetic BSE than heterozygotes.
1b.Approach (from AD-416):
To achieve the research goals it is imperative to increase the number of animals available to study this Prnp polymorphism. One female calf of the 2006 BSE case was identified and carries the E211K allele. The specific objectives are to be accomplished through the production of multiple offspring from this E211K heifer through superovulation and embryo transfer.
Approximately 50% of the offspring will be heterozygous for the E211K polymorphism while the others will serve as genetically matched non-E211K controls. Collection of semen from an E211K heterozygous bull will allow creation of E211K homozygotes.
To protect this unique resource immediate collection of embryos is necessary. The initial goal is to harvest 134 embryos that should result in approximately 62 pregnancies (half of which will carry the E211K polymorphism) for immediate use in the studies to amplify the E211K material, test for genetic susceptibility to TSE, and develop a breeding group to produce calves for transmissibility studies.
To achieve the goal of understanding the role of the E211K polymorphism with regard to genetic BSE we have utilized superovulation and embryo transfer obtaining a E211/K211 containing bull. We are now in a position to collect semen from the E211/K211 heterozygous bull to create K211/K211 homozygotes. To accomplish this goal we plan to collect semen from this bull and through artificial insemination using semen from the E211/K211 bull with superovulation and embryo transplantation using other E211/K211 heterzygotes generate 30-40 embryos resulting in 15-20 pregnancies yielding approximately 5 K211/K211 homozygous animals and 10 E211/K211 heterozyous animals as well as 5 E211/E211 homozygous controls.
The objective of this cooperative research is to protect the unique resource afforded us in the form of the only known cow possessing the 211K PRNP allele and to produce offspring containing this allele for research purposes. To date, 20 live calves have been delivered, 8 of which contain the 211K PRNP allele. An additional 40 embryos have been frozen and preserved for future use. As reported in the previous year, 1 of the 211K animals produced was a bull. We have since collected semen (500 units) and embryos have been collected from a sibling mating. Roughly 25% of these embryos will be 211K homozygous. As a derivative of this work we have inoculated the 2006 E211K H-type bovine spongiform encephalopathy (BSE) into a 211K calf and allowed the first complete description of the pathology of this unusual BSE.