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University of Alberta Identification of differentially expressed genes in chronic wasting disease infected elk by Sandor C. Dudas //M A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Animal Science Department of Agricultural, Food and Nutritional Sciences Edmonton, Alberta Spring 2009 Library and Archives Bibliotheque et 1*1 Canada Archives Canada Published Heritage Direction du Branch Patrimoine de I'edition 395 Wellington Street 395, rue Wellington Ottawa ON K1A 0N4 Ottawa ON K1A 0N4 Canada Canada Your file Votre reference ISBN: 978-0-494-54675-8 Our file Notre reference ISBN: 978-0-494-54675-8 NOTICE: AVIS: The author has granted a non L'auteur a accorde une licence non exclusive exclusive license allowing Library and permettant a la Bibliotheque et Archives Archives Canada to reproduce, Canada de reproduire, publier, archiver, publish, archive, preserve, conserve, sauvegarder, conserver, transmettre au public communicate to the public by par telecommunication ou par I'lnternet, preter, telecommunication or on the Internet, distribuer et vendre des theses partout dans le loan, distribute and sell theses monde, a des fins commerciales ou autres, sur worldwide, for commercial or non support microforme, papier, electronique et/ou commercial purposes, in microform, autres formats. paper, electronic and/or any other formats. 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Canada•+• Abstract Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy (TSE) of mule deer, white tailed deer, moose and elk. This invariably fatal neurologic disease has spread across North America infecting a growing number of fanned and free ranging cervids. The increasing prevalence of CWD could potentially increase the risk of transmission to traditional domestic livestock or humans. A limited understanding of CWD neurodegeneration at a molecular level has severely limited new approaches to treating, diagnosing and controlling this disease. In this study, we have used a bovine DNA microarray to identify genes which are differentially expressed in CWD infected elk. Altered regulation of genes involved in cytoskeleton formation, synapse function and immune signaling, all of which have been suggested as important in neurodegeneration, were identified in the CWD elk. These results improve our understanding of CWD induced neurodegeneration at the molecular level and could potentially identify diagnostic or therapeutic targets. Preface Chronic wasting disease is a transmissible spongiform encephalopathy which is gaining more attention due to its increasing incidence, geographic range and potential threat to animal and human health. Due to the lack of a well characterized model systems to study this disease little research has been done specifically on CWD to answer one of the most important unknowns of TSE diseases, how they cause neurodegeneration. The first two chapters of this thesis review the experimental evidence implicating various causes in prion disease induced neurologic disease. The first chapter presents the current state of knowledge regarding causes of cell death in TSE diseases and which proteins, molecules and cellular functions are potentially involved. In chapter 2, the contributions that DNA microarray gene expression analysis have made to improving our understanding of molecular mechanisms involved in TSE induced cytotoxicity are discussed. Finally, chapter 3 describes CWD and the work we have done on CWD elk using microarray gene expression analysis to increase our knowledge of this disease. Acknowledgments I would like to thank the Alberta Prion Research Institute, Prionet Canada and the Canadian Food Inspection Agency for their financial support. Thank you to the University of Alberta Bovine Genomics Laboratory staff, especially Dr. Masaaki Taniguchi, Yan Meng, Dr. Leluo Guan and Dr. Stephen Moore. Your guidance and assistance both during my time up in Edmonton as well as when I was back in Lethbridge is much appreciated. To my current and past coworkers including Dr. Anne Beeston, Dr. Stephanie Booth, Renee Clark, Nancy Herman, Dr. Catherine Graham, John Gray, Dr. Klaus Jericho, Dr. Lome Jordan, Roberta Quaghebeur, Greg Tiffin and Jianmin Yang, thank you for your help and advice both in the lab and while writing my thesis. A special thank you to Dr. Stefanie Czub, your support and guidance have been instrumental in helping me complete this project. And finally to my wife Gina and my sons Donte and Dion, your love, support and encouragement kept me going even when this task seemed impossible. Words can not express how much this means to me or how much I love you for this. I will never forget it. Table of Contents Page 1.0. Literature Review: Transmissible spongiform encephalopathies (TSE) and neurologic disease 1.1. Introduction 1 1.2. TSE disease background 1 1.2.1. Discovery of TSE diseases 1 1.2.2. The aetiological agent 2 1.2.3. The infectious prion protein 3 1.3. Causes of TSE induced neurologic disease 4 1.3.1. Neuronal impairment 5 1.3.1.1. TSE induced synaptic changes 5 1.3.1.2. Neurotransmitter dysfunction 6 1.3.2. Neuronal cell death 7 1.3.2.1. Loss of functional PrPc 7 1.3.2.2. Toxicity of PrPsc 9 1.3.2.3. Other PrP species 9 1.3.2.4. PrPc relocalization and accumulation 10 1.3.2.5. Cell system and organelle disruption 11 1.3.2.6. Involvement of autophagy 12 1.3.2.7. Immune/inflammatory involvement 13 1.4. Summary 14 1.5. References 16 2.0. Literature Review: Microarrays for understanding TSEs 2.1. Introduction 24 2.2. Microarrays for understanding disease and infection 26 2.3. Microarrays for understanding prion diseases 28 2.3.1. Protein folding, trafficking and degradation 28 2.3.2. Immune and inflammatory response 30 2.3.3. Cellular metabolism 31 2.3.4. Ion and cytoskeletal related genes 33 2.3.5. Cell signalling 34 2.3.6. Findings from unique experimental designs 35 2.4. Summary 37 2.5. References 38 3.0. Project: Identification of differentially expressed genes in CWD infected elk 3.1. Introduction 46 3.2. Materials and methods 50 3.2.1. Animals 50 3.2.2. RNA extractions 51 3.2.3. Amplification and labelling of mRNA 52 3.2.3.1. Target preparation 52 3.2.3.2. Target labelling 52 3.2.3.3. Hybridization and washing 53 3.2.4. DNA Microarray expression analysis 54 3.2.5. Real time qRT-PCR verification 55 3.2.5.1. Primer design and testing 55 3.2.5.2. Selection of house keeping genes for qRT-PCR analysis 56 3.2.5.3. qRT-PCR testing and efficiency 57 3.2.5.4. qRT-PCR analysis of CWD elk 57 3.3. Results 3.3.1. Confirmation of disease status 59 3.3.2. Microarray results 59 3.3.2.1. Population comparison microarray results 59 3.3.2.2. Selected animal comparison microarray results 60 3.3.2.3. Genetic effects on microarray results 61 3.3.3. qRT-PCR results 62 3.3.3.1. House keeping gene selection and efficiency determination 62 3.3.3.2. Validation of candidate genes selected from microarray analysis using qRT-PCR 63 3.4. Discussion 64 3.4.1. Disease status at sampling 64 3.4.2. Microarrays 64 3.4.2.1. Effects of analyzing a genetically diverse population 66 3.4.2.2. Effects of the prion protein genotype on the differential expression of genes 66 3.4.3. Quantitative RT-PCR 67 3.4.4. Significance of differentially expressed genes 69 3.4.4.1. Structural genes 70 3.4.4.2. Immune/inflammatory response and cell signalling 72 3.4.4.3. Synapse function 73 3.4.4.4. Calcium ion related genes 75 3.4.4.5. Functional groups missing from our study 76 3.5. Conclusion 77 3.6. References 103 Appendix Appendix 1: Total RNA extraction protocol 109 Appendix 2: DNA Microarray protocol 111 Appendix 3: Quantitative real time PCR (qRT-PCR) protocol 116 Appendix 4: Formulas used for data analysis 117 List of Tables Page Table 3-1: Experimental animals used for the identification of differentially expressed genes in CWD infected brains. 80 Table 3-2: House keeping genes identified in previous brain qRT-PCR studies which were tried on our elk cDNA. 81 Table 3-3: Real time PCR primers/probes and associated amplification efficiencies. 82 Table 3-4: The genes identified as differentially expressed by comparing the CWD negative population to the CWD positive population (n = 287). 83 Table 3-5: Genes identified as differentially expressed in 4, 5 or 6 out of 6 CWD positive versus CWD negative elk by microarray analysis. Genes missing a comparison(s) involving animal #28 (132LM) are highlighted. 90 Table 3-6: Microarray results of differentially expressed genes in 5 or 6 out of 6 CWD elk versus control elk.