.................................................................................................................................. ii ACKNOWLEDGMENTS ........................................................................................................... iv LIST OF TABLES ..................................................................................................................... viii LIST OF FIGURES ..................................................................................................................... ix LIST OF APPENDICES .............................................................................................................. xi ABBREVIATIONS ..................................................................................................................... xii PROTEIN NAMES .................................................................................................................... xiv CHAPTER I: INTRODUCTION ............................................................................................... 1 1.1. The cell cycle ................................................................................................................................. 2 1.1.1. The basic principles of cell cycle regulation in eukaryotes .................................................... 2 1.1.2. The cell cycle and the centrosome cycle are intricately linked ............................................... 4 1.1.3. A network of kinases and phosphatases orchestrates mitotic processes ................................. 5 1.2. The centrosome ........................................................................................................................... 12 1.2.1. Centrosome functions and structure ...................................................................................... 12 1.2.2. The centrosome proteome ..................................................................................................... 13 1.2.3. Centrioles .............................................................................................................................. 14 1.2.3.1. Centriole architecture .................................................................................................................... 14 1.2.3.2. Centriole functions ........................................................................................................................ 15 1.2.4. The pericentriolar material (PCM) ........................................................................................ 16 1.2.5. The centrosome cycle ............................................................................................................ 25 1.2.5.1. Centriole duplication ..................................................................................................................... 25 1.2.5.2. Centrosome maturation and separation ......................................................................................... 28 1.3. The mitotic spindle ..................................................................................................................... 32 1.3.1. Microtubules are the basic elements of the mitotic spindle .................................................. 32 1.3.1.1. Astral microtubules regulate spindle positioning .......................................................................... 33 1.3.1.2. Interpolar microtubules fulfill important roles inside the mitotic spindle .................................... 34 1.3.1.3. Kinetochore microtubules are essential for chromosome segregation .......................................... 35 1.3.2. Microtubule nucleation pathways during mitotic spindle assembly ..................................... 37 1.3.2.1. RanGTP-dependent microtubule nucleation around chromatin .................................................... 38 1.3.2.2. CPC-dependent microtubule nucleation at kinetochores .............................................................. 39 1.3.2.3. Microtubule-dependent microtubule amplification within the spindle ......................................... 40 1.3.3. The role of mitotic motor and nonmotor proteins during spindle assembly ......................... 42 1.3.3.1. Mitotic motor proteins ................................................................................................................... 42 1.3.3.2. Nonmotor spindle proteins ............................................................................................................ 45 1.4. Spindle defects and human disease ........................................................................................... 49 1.4.1. Defects during spindle assembly can result in chromosome instability and aneuploidy ...... 49 1.4.2. Centrosomes are critical for asymmetric cell divisions during neurogenesis ....................... 52 1.5. Summary and rationale of my graduate work ........................................................................ 54 1.6. Figures ......................................................................................................................................... 56