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Understanding Lamin A/C and Its Roles in Disease

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Understanding Lamin A/C and Its Roles in Disease UNDERSTANDING LAMIN A/C AND ITS ROLES IN DISEASE PATHOLOGIES AUDREY WANG SHIMEI BSC (HONS.), NANYANG TECHNOLOGICAL UNIVERSITY A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF BIOLOGICAL SCIENCES NATIONAL UNIVERSITY OF SINGAPORE 2014 i ii ACKNOWLEDGEMENTS I would like to express my sincere gratitude to Professor Colin L. Stewart (THE BOSS) for his continuous support of my PhD study. His guidance, motivation and most importantly, his quirky sense of humour have made these six years a great learning journey. His unsurpassed knowledge of lamins has opened my eyes to the world of nuclear dynamics. His exquisite taste in excellent wines, good food and foresight in choosing awesome people for the group made everything better. I would like to thank my mentor Dr. Henning Horn, who has been a great teacher to me on both academic and personal level. I’m extremely grateful to him for all his advice at work and personal matters, through good and difficult times. I also thank each and everyone in the BS lab for their great advice, support and friendship. I am very blessed to be in this lab and could not have asked for better folks to work with. In particular, Alex, Hen, Rafidah, Xiaoqian, Esther and Gracy who have helped in more ways than one, and Tinka, Dave, Anna for helping to read through bits and pieces of this thesis. I also must thank my collaborators from Ludwig-Maximilians University Munich: the late Prof Boris Joffe whom, sadly, I never met in person, and a very kind and brilliant scientist, Dr Irina Solovei. Without their persistence and great ideas, we would not have been able to publish in Cell. I’d also like to thank Dr Nick Barker and Prof Barbara Knowles for some of mouse lines mentioned in this thesis. I would also like to thank the members of my Thesis Advisory Committee, Prof. Christoph Winkler (NUS), Prof. Phan Toan Thang (NUS) and Prof Brian Burke (IMB). I am grateful for their time and advice during my Phd studies. I would like to acknowledge the financial, academic and technical support of the Institute of Medical Biology, A-STAR, and particularly in the award of the Scientific Staff Development Award that provided the necessary financial support for this research. I would also like to mention Professor Urs Boelsterli who was my first supervisor and opened my eyes to the world of research in toxicology and mitochondrial metabolism. His great personality and passion in science has made me aspire to be a better person and scientist. Above all, I would like to thank my husband Desmond and daughter Yoghurt for their unequivocal support and great patience at all times. iii TABLE OF CONTENTS LIST OF FIGURES ..................................................................................... XV LIST OF SYMBOLS ................................................................................. XIX CHAPTER 1 - INTRODUCTION .................................................................. 1 1.1 The nuclear envelope and lamina proteins .............................................. 1 1.1.1 The nuclear envelope ............................................................................ 1 1.1.2 The nuclear lamins ................................................................................ 2 1.1.3 Genes encoding lamins ......................................................................... 3 1.1.4 Structure of lamins ................................................................................ 4 1.1.5 Post-translation processing of lamins ................................................... 5 1.1.6 Expression profile of lamins ................................................................. 6 1.1.7 Integral membrane proteins of the INM ............................................... 9 1.1.7a LEM domain-containing proteins ................................................. 10 1.1.7b Lamin B Receptor (LBR).............................................................. 12 1.1.7c SUN and KASH proteins .............................................................. 13 1.2 Functions of Lamins ................................................................................ 15 1.2.1 Maintenance of the nuclear architecture ............................................. 16 1.2.2 Cytoskeleton organization and function ............................................. 18 1.2.3 Involvement in cellular signaling and functions ................................. 19 1.2.3a Lamins in DNA replication ........................................................... 20 1.2.3b Lamins in gene regulation ............................................................. 20 1.2.3c Regulation of genomic stability .................................................... 22 iv 1.2.3d Regulation of adult stem cell differentiation ................................ 24 1.3 Diseases associated with the nuclear lamina ......................................... 26 1.3.1 Laminopathies ..................................................................................... 27 1.3.2 Nuclear envelopathies ......................................................................... 31 1.3.3 Mechanisms of disease ....................................................................... 33 1.4 Lamins and cancer ................................................................................... 35 1.5 Mouse models of Lmna mutations .......................................................... 37 1.6 Cre-lox technology ................................................................................... 41 1.7 Aims and objectives.................................................................................. 43 CHAPTER 2 - MATERIALS AND METHODS ......................................... 47 2.1 Mouse husbandry ....................................................................................... 47 2.2 Generation of Lmna∆/∆ knockout mice ....................................................... 47 2.3 Genotyping of mutant mice ....................................................................... 48 2.4 RNA extraction and quantitative real time-PCR (qRT-PCR) ..................... 48 2.5 Immunoblot analysis of tissues and cell lines ............................................ 49 2.6 Histological studies and immunofluorescence microscopy ....................... 49 2.7 Extraction and cell culture of mouse adult fibroblasts (MAFs) ................. 51 2.8 Generation of the LbrGT/GT mice ................................................................ 52 v 2.9 Microscopy and image acquisition and analysis for chromocenters ......... 53 2.10 Transcriptome analysis of Lmna∆/∆ and LbrGT/GT myoblast cultures ........ 53 2.11 Deleting Lmna in the intestinal epithelial cells (IECs) ............................ 55 2.12 Isolation of intestinal epithelial cells (IECs) ............................................ 56 2.13 Deriving a tumour-sensitized mouse line lacking Lmna .......................... 56 2.14 Preparation and scoring of intestinal polyps ............................................ 57 2.15 Deleting Lmna in the intestinal stem cells ............................................... 57 2.16 Deleting Lmna in the keratinocytes of skin and tongue epithelium......... 58 2.17 Measurement of epidermis thickness in Lmna∆/∆/K14-Cre mice .................. 59 2.18 Analysis of hair cycle in Lmna∆/∆/K14-Cre mice .......................................... 60 2.19 Analysis of wound healing capacity of Lmna∆/∆/K14-Cre mice ................... 60 2.20 Isolation of keratinocytes from mouse dorsal skin .................................. 61 2.21 Gene expression microarray analysis of Lmna-null keratinocytes ......... 62 2.22 Two-stage chemical carcinogenesis in Lmna∆/∆/K14-Cre mouse skin .......... 63 2.23 Cell culture of N/TERT-1 keratinocytes, viral infection and knockdown assay to obtain LMNAKD .................................................................................. 64 2.24 Cell proliferation assay of LMNAKD N/TERT-1 keratinocytes ................ 64 vi CHAPTER 3- DERIVING AND CHARACTERIZING A CONDITIONAL LAMIN A/C KNOCKOUT MOUSE MODEL .............. 69 3.1 The conditional lamin A mouse model (LmnaFL/FL) ................................... 69 3.2 Creating and validating the global lamin A/C knockout mice (Lmna∆/∆) .. 70 3.3 Lamin A/C transcripts and proteins are depleted in Lmna∆/∆ mice ............ 71 3.4 Characterization of the Lmna∆/∆ knockout mice ........................................ 73 3.5 Histological analysis of Lmna∆/∆ tissues .................................................... 75 3.6 Redistribution of emerin in Lmna∆/∆ MAFs ............................................... 75 3.7 Conclusions ................................................................................................ 77 CHAPTER 4 – LAMIN B RECEPTOR (LBR) AND LAMIN A/C SEQUENTIALLY TETHER PERIPHERAL HETEROCHROMATIN AND INVERSELY REGULATE DIFFERENTIATION ........................... 79 4.1 The LBRGT mouse line ............................................................................... 79 4.2 LbrGT/GT mice exhibit anomalies in skin morphology ................................ 81 4.3 Mammalian rod cells with inverted nuclei do not express both lamin A/C and LBR ........................................................................................................... 83 4.4 Expression of LMNA/C and LBR is temporally coordinated ................... 84 4.4 Nuclei not expressing LMNA/C undergo nuclear inversion in LbrGT/GT mice………….. ...............................................................................................
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