Chip-Seq Analysis of AIRE, FEZF2, and DEAF1 Transcription Factors in Human Thymus Tissue
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Master’s Thesis 2020 60 ECTS Faculty of Chemistry, Biotechnology, and Food Science (KBM) ChIP-seq analysis of AIRE, FEZF2, and DEAF1 transcription factors in human thymus tissue Dina Ruud Aronsen Biotechnology – molecular biology ChIP-seq analysis of AIRE, FEZF2 and DEAF1 transcription factors in human thymus tissue Dina Ruud Aronsen Supervisors: Prof. Dr. Benedicte A. Lie (Main supervisor) Dr. Teodora Ribarska Assoc. Prof. Siv Kjølsrud Bøhn Master thesis Department of Medical Genetics, Oslo University Hospital Faculty of Chemistry, Biotechnology and Food science Norwegian University of Life Sciences June 2020 i ii ©Dina Ruud Aronsen 2020 ChIP-seq analysis of AIRE, FEZF2 and DEAF1 transcription factors in human thymus tissue https://nmbu.brage.unit.no iii Acknowledgements The work of this thesis was carried out in collaboration with the Department of Medical Genetics, at Oslo University Hospital (OUS), as part of a Master´s Degree in Biotechnology at the Norwegian University of Life Sciences (NMBU), the main affiliation being the Faculty of Chemistry, Biotechnology and Food Science (KBM), from August 2019 to June 2020. Foremost, I would like to thank my main supervisor Benedicte A. Lie for the opportunity to be a part of her thymus group and conduct such interesting research. I am grateful for her guidance, insightful advice and the enthusiasm she has shown for my work. I am thankful for the outstanding work of my co-supervisor Teodora Ribarska, Postdoc. She guided and encouraged me through both the writing process and laboratory work. Her invaluable advice and knowledge have greatly contributed to my understanding throughout this process. Additionally, her laboratory expertise and guidance have helped me improve my laboratory skills and expanded my expertise by introducing me to several laboratory techniques. Additionally, I would like to thank my supervisor at NMBU, Siv Kjølsrud Bøhn, for valuable feedback and guidance. I would like to thank all past and present members of the Immgen-group for welcoming and including me and for providing advice along the way. I would like to extend an extra thank to the thymus-group for advice and for helping with laboratory work. Lastly, I would like to thank my loved ones, who have supported me throughout the entire process. I will be grateful forever for your love and encouragement. Oslo, June 2020 Dina Ruud Aronsen iv Abstract Autoimmune diseases develop as a consequence of incorrect establishment of self-tolerance. A key element in this process is the presentation of tissue-restricted antigens (TRA) by medullary thymic epithelial cells (mTECs) and antigen presenting cells (APCs) to the developing T-cells in the thymus. TRA expression is mostly driven by the transcription factors Autoimmune regulator (AIRE) and Forebrain Embryonic Zinc Finger-Like Protein 2 (FEZF2) in mTECs. Deformed Epidermal Autoregulatory Factor 1 Homolog (DEAF1), present in all thymic APCs, is suggested to also control TRA expression as it does in the lymph node. The purpose of this study was to establish and optimise chromatin immunoprecipitation (ChIP) method for use in human freshly frozen thymus tissues and apply it to determine the genomic binding sites of FEZF2, AIRE and DEAF1 in the infant human thymus in order to better understand the molecular mechanism of T-cell self-tolerance establishment. Aiming to reach the highest possible sensitivity and specificity of the enrichment, we optimised the ChIP procedure using homogenised frozen human thymic tissue (n=3) by testing the parameters: fixation (single or double crosslinking), fragmentation by sonication, antibody type and amount, and immunoprecipitation conditions. The optimal ChIP conditions were found to be: 1) Fixation for 5 min with 1 % formaldehyde and 2.5 mM disuccinimidyl glutarate with 20-30 mg tissue powder ; 2) Sonication to 300-500 bp average DNA fragment size; 3) IP with 5 µg anti-AIRE (GeneTex), 5 µg anti-DEAF1 (LSBio), and 1 µg FEZF2 (Abcam) per 100 µl chromatin (out of 2 mL chromatin isolated from 20-30 mg tissue powder) using 30 µl protein G magnetic beads (Dynabeads) per IP reaction. These condition provided the highest specific recovery of target regions for the three transcription factors, measured by qPCR. The optimal conditions were used in a pilot ChIP-seq experiment to locate binding sites of the transcription factors. Analysis of AIRE, FEZF2, and DEAF1 ChIP-seq data from human thymus and qPCR of ChIP using TEC and APC enriched cell sample isolated from half of a thymus showed low enrichment of target genes, which may be caused by scarcity of cells expressing AIRE, FEZF2, and DEAF1 in bulk thymus tissue or enriched for mTEC and APC thymus cell suspension. To assess the function of AIRE, FEZF2, and DEAF1 in mTECs and thymic APCs, further exploration using CUT&Tag or ChIP-seq will be needed using mTEC and APC enriched cell solution. v vi Table of Contents Acknowledgements ......................................................................................................................... iv Abstract ............................................................................................................................................ v Abbreviations .................................................................................................................................. ix List of Figures ................................................................................................................................. xi 1 Introduction ............................................................................................................................... 1 1.1 The Immune System .......................................................................................................... 1 1.1.1 Cells of the Immune System ...................................................................................... 1 1.1.2 The Innate Immune System ........................................................................................ 5 1.1.3 Human Leukocyte Antigen ........................................................................................ 5 1.1.4 The Adaptive Immune System ................................................................................... 6 1.2 T-cell Development ........................................................................................................... 8 1.2.1 Positive Selection ..................................................................................................... 10 1.2.2 Negative Selection .................................................................................................... 11 1.2.3 Peripheral tolerance .................................................................................................. 13 1.2.4 Antigen-Presenting Cells in the Thymus ................................................................. 13 1.3 AIRE, FEZF2, and DEAF1 Functions in APCs .............................................................. 14 1.3.1 AIRE ......................................................................................................................... 14 1.3.2 FEZF2 ....................................................................................................................... 15 1.3.3 DEAF1 ..................................................................................................................... 17 1.4 Autoimmune Diseases ..................................................................................................... 18 2 Aims ........................................................................................................................................ 20 3 Materials and Methods ............................................................................................................ 21 3.1 Thymus collection ........................................................................................................... 21 3.2 Frozen thymus tissue preparation .................................................................................... 21 3.3 Fresh thymus tissue dissociation ..................................................................................... 21 3.4 Chromatin Immunoprecipitation followed by Sequencing ............................................. 23 3.4.1 Chromatin isolation .................................................................................................. 25 3.4.2 Chromatin Immunoprecipitation .............................................................................. 27 3.4.3 Quantitative PCR (qPCR) ........................................................................................ 28 3.4.4 Library preparation and sequencing ......................................................................... 31 vii 3.5 ChIP DNA analysis ......................................................................................................... 32 3.6 CUT&Tag ........................................................................................................................ 32 4 Results ..................................................................................................................................... 36 4.1 AIRE, FEZF2, and DEAF1 expression in thymus .......................................................... 36 4.2 Chromatin Immunoprecipitation Optimisation ............................................................... 37 4.2.1 Crosslinking and Sonication Optimisation ............................................................... 37 4.2.2 Chromatin Immunoprecipitation