An Investigation Into the Genetic Architecture of Multiple System Atrophy and Familial Parkinson's Disease
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An investigation into the genetic architecture of multiple system atrophy and familial Parkinson’s disease By Monica Federoff A thesis submitted to University College London for the degree of Doctor of Philosophy Laboratory of Neurogenetics, Department of Molecular Neuroscience, Institute of Neurology, University College London (UCL) 2 I, Monica Federoff, confirm that the work presented in this thesis is my own. Information derived from other sources and collaborative work have been indicated appropriately. Signature: Date: 09/06/2016 3 Acknowledgements: When I first joined the Laboratory of Neurogenetics (LNG), NIA, NIH as a summer intern in 2008, I had minimal experience working in a laboratory and was both excited and anxious at the prospect of it. From my very first day, Dr. Andrew Singleton was incredibly welcoming and introduced me to my first mentor, Dr. Javier Simon- Sanchez. Within just ten weeks working in the lab, both Dr. Singleton and Dr. Simon- Sanchez taught me the fundamental skills in an encouraging and supportive environment. I quickly got to know others in the lab, some of whom are still here today, and I sincerely appreciate their help with my assimilation into the LNG. After returning for an additional summer and one year as an IRTA postbac, I was honored to pursue a PhD in such an intellectually stimulating and comfortable environment. I am so grateful that Dr. Singleton has been such a wonderful mentor, as he is not only a brilliant scientist, but also extremely personable and approachable. If I inquire about meeting with him, he always manages to make time in his busy schedule and provides excellent guidance and mentorship. I am extremely appreciative of the mentorship from my secondary supervisor, Dr. Henry Houlden, over the last three years. Despite my being a non-resident student, Dr. Houlden has been a great communicator and has been very helpful towards mapping out my future goals during my visits to UCL ION. As a physician-scientist, he has an excellent perspective on the balance required between both clinical and research aspects in one’s career. I have also been afforded the opportunity to shadow him in the 4 Neurology clinic during my time at UCL, which has been invaluable towards connecting the fruits of neurogenetics research with patient care in clinical neurology. Working with several other PhD students at UCL ION has been a pleasure. Lucia Schottlaender and Sarah Wiethoff have been wonderful colleagues and great friends. At the LNG, I have come to meet so many extraordinary people (from PhD students, to post docs and IRTAs) who I have both worked with and gotten to know including: Monia Hammer, Celeste Sassi, Christopher Letson, Timothy Ryan Price, Sampath Arepalli, Nick Bernstein, Sam Coster and many others. I would also like to specifically thank Ryan Price for helping me with the heritability analysis, as he has been a great asset to the LNG team. Secondly, I would like to greatly thank Dr. Mike Nalls and Jinhui Ding for helping me with my MSA exome sequencing analyses. Finally, I would like to thank my wonderful family for their love and support during these last few years. I could not have done it without all of you by my side. I’m so fortunate to have had this experience with everyone at LNG and UCL and look forward to future collaborations. 5 Table of Contents 1 Introduction ................................................................................................................. 18 1.1 Thesis objectives: ................................................................................................. 18 1.2 Why pursue genetics in disease? ......................................................................... 20 1.3 Advances in genomic technologies: unraveling the genetic basis of disease ...... 21 1.3.1 Monogenic diseases ...................................................................................... 22 1.3.1.1 Linkage analysis and positional cloning ................................................ 23 1.3.1.2 Next generation sequencing in monogenic diseases .............................. 25 1.3.2 Complex diseases .......................................................................................... 30 1.3.2.1 Candidate gene association studies in complex diseases ....................... 33 1.3.2.2 Genome wide association studies in complex diseases ......................... 34 1.3.2.3 Next generation sequencing in complex diseases .................................. 44 1.3.3 The future of human disease genetics ........................................................... 48 1.4 Parkinson’s disease .............................................................................................. 49 1.4.1 Clinical and neuropathological features of Parkinson’s disease ................... 49 1.4.2 Genetic etiology of monogenic PD ............................................................... 52 1.4.2.1 Autosomal dominant PD ........................................................................ 53 1.4.2.1.1 LRRK2 ............................................................................................ 53 1.4.2.1.2 SNCA .............................................................................................. 55 1.4.2.1.3 VPS35 .............................................................................................. 57 1.4.2.1.4 ATXN2 and ATXN3 ...................................................................... 57 1.4.2.1.5 MAPT ............................................................................................. 58 1.4.2.1.6 DCTN1 ............................................................................................ 58 1.4.2.1.7 GCH-1 ............................................................................................. 59 1.4.2.2 Autosomal recessive PD ........................................................................ 59 1.4.2.2.1 PARK2 ............................................................................................ 59 1.4.2.2.2 PINK1 ............................................................................................. 60 1.4.2.2.3 DJ-1/PARK7 ................................................................................... 60 1.4.2.2.4 ATP13A2 ........................................................................................ 61 1.4.2.2.5 FBXO7 ............................................................................................ 62 1.4.2.2.6 PLA2G6 .......................................................................................... 62 1.4.2.2.7 PANK2 ............................................................................................ 63 1.4.2.2.8 Other rare recessive forms of PD .................................................... 64 1.4.3 Molecular mechanisms of PD gene mutations .............................................. 65 1.4.4 Integrating critical molecular processes regulated by PD proteins ............... 66 1.4.5 Risk loci in PD .............................................................................................. 69 1.4.5.1 Risk loci identified by GWA ................................................................. 71 1.4.6 Interpretation of GWA findings and PD etiology ......................................... 75 1.4.7 Making progress in PD ................................................................................. 76 1.5 Multiple system atrophy ...................................................................................... 77 1.5.1 Clinical and neuropathological features of MSA .......................................... 78 1.5.2 Understanding MSA etiology ....................................................................... 83 1.5.3 Preliminary association studies ..................................................................... 83 1.5.4 The genetics of MSA .................................................................................... 85 1.5.4.1 Mendelian inheritance ............................................................................ 85 6 1.5.4.2 COQ2 mutations .................................................................................... 86 1.5.4.3 Genes encoding proteins involved in oxidative stress ........................... 88 1.5.4.4 PRNP...................................................................................................... 89 1.5.4.5 SNCA ..................................................................................................... 90 1.5.4.6 Other PD linked genes ........................................................................... 92 1.5.4.7 Copy number changes ............................................................................ 94 1.5.5 Proposed mechanisms of MSA pathogenesis ............................................... 96 1.5.5.1 Role of Neurotoxicity and Oxidative Stress .......................................... 96 1.5.5.2 Role of ubiquitin-proteasome system .................................................. 100 1.5.6 The dynamic behind key players: neurotoxicity, oxidative stress and the UPS 103 1.5.7 Drug Therapies and targets in MSA ........................................................... 104 1.5.8 A comparison of PD and MSA ................................................................... 106 1.5.9 How to move forward ................................................................................. 107 2 Estimating the heritable component of MSA ............................................................ 110 2.1 Introduction .......................................................................................................