Identification of MLL-AF9 Related Target Genes and Micrornas Involved in Leukemogenesis
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Identification of MLL-AF9 related target genes and microRNAs involved in leukemogenesis Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften (Dr. rer. nat.) an der Fakultät für Biologie der Ludwig-Maximilians-Universität München Durchgeführt am Forschungszentrum des Dr. von Haunerschen Kinderspitals der Ludwig-Maximilians-Universität München vorgelegt von Katrin Kristina Fleischmann München, 3. Mai 2012 Erstgutachterin: Frau Prof. Dr. Elisabeth Weiss Zweitgutachter: Herr Prof. Dr. Michael Schleicher Sondergutachter: Herr Prof. Dr. Adelbert Roscher Tag der Abgabe: 03.05.2012 Tag der mündlichen Prüfung: 17.09.2012 What is a scientist after all? It is a curious man looking through a keyhole, the keyhole of nature, trying to know what's going on. Jacques Yves Cousteau Preamble and Acknowledgments How to explain the change from evolutionary ecology to tumor biology? After my diploma thesis in evolutionary ecology and a major in ecology, I was facing some skepticism while being interviewed for PhD positions in the biomedical field. What was my motivation to study biology? Why do I continue to feel this strong enthusiasm for this field? For me, it was always the grand question “How does life work?” that drove me and which may interconnect almost every aspect within natural sciences. Only when we strive to get answers to this grand question we may reach an understanding as to what happens in disease. I am profoundly grateful to my dear colleagues Dr. Julia von Frowein, Dr. Thomas Magg and Dr. Uta Fuchs who supported me to become one of their colleagues at the research center of the Dr. von Haunerschen Kinderspital. Since then, innumerable great and inspiring discussions allied us. With them and many other splendid colleagues at our research center (among them Kristin Hähnel, Carola Laudano, Rita Meilbeck and many others who may forgive that I can not name all), I shared a vivid exchange of information and cordial coffee breaks. They all made every- day-life at our research center always joyful and worthwhile. I profoundly thank Prof. Dr. Adelbert Roscher for his experimental advice and supervision, many stimulating discussions, for directing my thesis over these years and for his help when it was most crucial. Further great thanks go to: Prof. Dr. Elisabeth Weiss for her friendly support and for representing this thesis at the Faculty of Biology of the Ludwig-Maximilians Universität München. PD Dr. Irene Schmid whose friendly support has always been of great value for my research at the Dr. von Haunerschen Kinderspital and for providing insights into the clinical oncology. PD Dr. Philipp Pagel for bioinformatical collaboration, stimulating discussions and open ears in a truly remarkable cooperation. Prof. Dr. Arndt Borkhardt for the initiation of this work and for supporting me while he was still at our institute. And last but not least to: My dearest Markus, with whom I could share endless happy moments in nature and every-day-life while traveling, climbing and going on ski-randonnée, for taking care of a healthy work-life-balance. My loving parents Sigrid and Prof. Dr. Rudolf Schröck for supporting me in my interests and in every way anyone could wish. My brother and fellow scientist Dr. Florian Schröck for his friendship and interest in my work and for seeing it from a different angle. My family and friends for their friendship and support. This work has been supported by the Graduiertenkolleg 1202 „Oligonucleotides in Cell Biology and Therapy“ from the Deutsche Forschungsgemeinschaft. Index 1 Index 1 Index ..................................................................................................................................... I 2 List of figures...................................................................................................................... V 3 List of tables .................................................................................................................... VII 4 Summary ............................................................................................................................. 1 5 Zusammenfassung .............................................................................................................. 3 6 Introduction ........................................................................................................................ 5 6.1 Genetic aberrations in leukemia ...................................................................................... 5 6.2 The genes MLL, AF9, MLL-AF9 and their functions ...................................................... 5 6.3 The role of MLL-AF9 fusion gene in leukemia ............................................................. 10 6.4 MicroRNAs and their role in hematologic malignancies .............................................. 11 6.5 Aim of this study ........................................................................................................... 14 7 Material and Methods ...................................................................................................... 15 7.1 Cell and molecular biological methods ......................................................................... 15 7.1.1 Cell culture ............................................................................................................ 15 7.1.2 SiRNAs and miRNA mimics ................................................................................ 15 7.1.3 Transfections of siRNAs, miRNA-mimics and shRNA plasmids ........................ 16 7.1.4 Confocal fluorescence microscopy ....................................................................... 17 7.1.5 Cell diameter and proliferation ............................................................................. 18 7.1.6 Flow cytometric measurements ............................................................................. 19 7.1.6.1 Transfection efficiency ................................................................................... 19 7.1.6.2 Monitoring of stable transfected cells ............................................................. 19 7.1.6.3 Cell cycle analysis ........................................................................................... 19 7.1.6.4 Apoptosis detection ......................................................................................... 20 7.1.7 RNA extraction and determination of RNA concentration, purity and integrity .. 21 7.1.8 Reverse transcriptase quantitative real-time PCR ................................................. 21 7.1.9 Gene expression profiling ..................................................................................... 22 7.1.10 MicroRNA profiling and confirmatory techniques ............................................... 23 7.1.10.1 Quantitative microRNA detection via TaqMan miRNA Low Density Array and single assay qRT-PCR .................................................................. 23 7.1.10.2 Semiquantitative microRNA detection via microarrays ................................ 23 I Index 7.2 Biochemical methods .................................................................................................... 24 7.2.1 Western blot .......................................................................................................... 24 7.2.2 TaqMan Protein Assay ........................................................................................... 25 7.3 Biostatistical methods ................................................................................................... 27 7.3.1 Gene expression profiling data analysis ................................................................. 27 7.3.2 Quantitative LDA miRNA profiling data analysis ................................................ 29 7.3.3 Semiquantitative microarray miRNA profiling data analysis ................................ 30 7.3.4 Correlation analysis of array and qRT-PCR data ................................................... 31 7.3.5 Functional disease ontology analysis ..................................................................... 31 7.3.6 Functional gene ontology analysis ......................................................................... 31 7.3.7 MiRNA target prediction ....................................................................................... 32 7.4 Prioritization of likely candidate genes ......................................................................... 32 8 Results ................................................................................................................................ 35 8.1 Experimental design and siRNA selection .................................................................... 35 8.1.1 Transfection method and efficiency ....................................................................... 35 8.1.2 Design and selection of efficient siRNAs against MLL-AF9 in THP1 cells .......... 37 8.2 MLL-AF9 knockdown ................................................................................................... 39 8.2.1 Experimental conditions ........................................................................................ 39 8.2.2 Validation of MLL-AF9 knockdown ...................................................................... 39 8.3 Cellular phenotype and functional endpoints of MLL-AF9 knockdown ....................... 43 8.4 MLL-AF9 knockdown dependent effects on gene expression ...................................... 47 8.4.1 Quality control of gene expression profiling results .............................................