Stephen Mullin – Phd Thesis
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Stephen Mullin – PhD thesis Risk stratification and targeted neuroprotection in Parkinson disease utilising the glucocerebrosidase pathway Dr. Stephen Mullin 64,106 words 1 Stephen Mullin – PhD thesis For my wife Tanya and my darling daughter Jessica. This thesis took too many evenings and weekends which should have been spent with you both. Without your love and support it would never have been completed. 2 Stephen Mullin – PhD thesis Acknowledgements Above all I must express my gratitude to all the participants who took part in the studies that make up this thesis. Their commitment to research is humbling and inspiring. Moreover, I must also thanks the support of the Gaucher association (in particular Tanya Histed Collins, Jeremy Manuel and Dan Brown) and Parkinson’s UK. Their support was crucial to all of the work presented here. This thesis is a grounded on foundations of the previous work, good will and patience of numerous people. My mother and father who took on the uneviable task of proof reading it. Prof. Sandip Patel, Dr. Bethan Kilpatrick and Dr. Lizzie Yates took a neophyte and taught him, in spite of his medic tendencies, to carry out single cell imaging. Dr. Joana Magalhaes and Dr. Ania Migdalska showed considerable restraint in showing me how breed and harvest mice primary cultures. Dr. Michelle Beavan and Dr. Alistair Mcneil passed on a cohort of patients which most PhD students would be the envy of most PhD students. The efforts of Dr. Marco Toffoli and Dr. Micol Avenali were vital to the cohort study. Jonathan Bestwick tolerated my very tentative and unprepared immersion into the world of repeated measures statistics. Prof. Henrik Zetterberg and Prof. Kevin Mills offered considerable time, capital and above all expertise in carrying out the various biomarkers studies, while Dr.Wendy Heywood and Jenny Hallqvist carried out many of these assays. Dr. Morton Stokholm and Prof. David Brooks supported and funded the PET imaging studies and looked after me during my myriad expeditions to Denmark. Dr. Alistair Noyce, Prof. Anette Schrag, Helen Brooker, Prof Keith Wesnes, Any Cartwright enabled the hugely complicated rapsodi portal to become a reality. Dr. Steven Lubbe and Prof. Huw Morris were invaluable sources of advice and expertise for the meta analysis of genetic case control data. AiM PD would not have been possible without Laura Smith, Katherine Lee, Gayle De Souza, Prof. Tom Foltynie, Dr. Phil Woodgate, Dr. Vincenzo Libri, Laura Henelly, Mark Elliot, Kerry Guile, Bryony Barling, Rita Smith and Edwina Sanders. Sarah Cable was the bedrock of most of the clinical work carried out in this thesis. Her energy and tireless commitment to subjects of tremendous sensitivity as well as her near infinite work ethics saved a number of projects on a number of occasions. Dr. Derralyn Hughes and Prof Atul Mehta have between them educated me about lysosomal storage diseases with patience and enthusiasm. Equally the staff of the lysosomal storge disease unit and most notably Patricia Pilgrim, June perry, Juniebel Cook and Linda Patridge must be thanked. Rob Baker, Dr. Matt Gegg, Dr. Christos Proukakis, Dr. Natalie Welsh, Dr. Christina Gewinner, Dr. Mark Cooper have provided help at advice throughout the thesis. Finally, I must thank my supervisor and mentor Prof. Tony Schapira, who taught, guided and supported me through the myriad highs and lows. It is an opportunity I hope some day I may be able to repay. 3 Stephen Mullin – PhD thesis Abstract: Objectives: Glucocerebrosidase mutations represent genetically the most significant risk factor for Parkinson disease, however their penetrance is incomplete and variable such that only a minority of glucocerebrosidase mutation carriers will develop Parkinson disease. In this thesis I aimed to investigate the basis for this incomplete penetrance, to identify indices which may be used to predict Parkinson disease conversion amongst glucocerebrosidse mutation carriers and to test a putative neuroprotective drug designed to modify the glucocerebrosidase pathway. Methods: In chapter 2 we used meta and joint analyses to calculate the odds ratio of developing Parkinson disease with individual glucocerebrosidase mutations. In chapter 3 we prospectively assessed a cohort of glucocerebrosidase mutation carriers without Parkinson disease for prodromal signs of Parkinsonism. In chapter 4 we sought to extend the scope, scale and sustainability of this study by producing a prototype study to assess these patients remotely through the internet. In chapter 5 we investigated whether novel imaging (PET using the PK-1195 and DAT ligands), serum (alpha synuclein, tau and inflammatory markers) and urine (hypothesis generating screen) could be used to predict PD conversion. In chapter 6 we used single cell calcium imaging in a primary neuronal mouse model carrying the 4 Stephen Mullin – PhD thesis N370S glucocerebrosidase mutation to investigate whether deranged calcium homeostasis might be the basis for the selective vulnerability of dopaminergic neurons in glucocerebrosidase mutation carrying cells. In chapters 7 and 8 we present optimisation and preliminary data from AiM PD, a phase II, open label, non placebo controlled trial of ambroxol, a small molecular chaperone of the glucocerebrosidase enzyme. Results: Chapter 2: We derived quantifiable estimates of Parkinson disease risk for 84GG, E326K N370S, L444P, D409H, RecNcil as well as important data relating to the ethnic distribution of these mutations. Chapter 3: The University of Pennslyvannia smell identification test and Montreal cognitive assessment scores of glucocerebrosidse mutation carriers were worse than those of controls. There is a clustering effect amongst glucocerebrosidse mutation carriers whereby poor scores in these assessments and the Beck’s depression index seemed to be present together in a subset of participants. Chapter 4: We show the rapsodi portal is able, using validated assessments, to detect Parkinson disease features. Preliminary data shows cognitive deficits amongst Glucocerebrosidase mutations carriers exist compared to controls. Chapter 5: PK11195 signal is increased in the substantia nigra of glucocerebrosidase mutation carriers compared to controls and this signal increase correlates with olfactory loss. Serum alpha synuclein levels in glucocerebrosidase carriers correlate with the number of severe (neuronopathic) mutations and a risk score derived from prospective assessment of prodromal Parkinson disease features. The hypothesis generating urine proteomics 5 Stephen Mullin – PhD thesis screen identified a number of potential markers of Parkinson disease conversion including elements of the IgG kappa light chain. Chapter 6: We found no evidence of deranged calcium homeostasis Chapter 7: The glucocerebrosidase enzyme activity assay has been optimised to be reproducibly used in cerebrospinal fluid samples in our hands. The optimal time to carry out the assay to prevent degradation of activity following freezing is within 2 weeks of collection. In vitro addition of ambroxol to control CSF at physiologically relevant concentrations caused a 50% reduction in activity levels, due presumably to anatagonistic binding to the active site of the enzyme. Chapter 8: Preliminary results show that ambroxol delivers a statistically significant increase in leucocyte glucocerebrosidase activity amongst glucocerebrosidase mutation carriers with Parkinson disease. These patients seem to have worse features of non motor Parkinson disease symptoms than idiopathic Parkinson disease cases. Conclusions: Our results collectively suggest it may be feasible to stratify risk of Parkinson disease conversion amongst glucocerebrosidse mutation carriers on the basis of genetic, clinical, imaging and biochemical indices. Moeover they suggest that ambroxol has potential as a neuroprotective agent in Parkinson disease. 6 Stephen Mullin – PhD thesis Publications Publications from thesis Arkadir, David, Tama Dinur, Stephen Mullin, Atul Mehta, Hagit N Baris, Roy N Alcalay, and Ari Zimran. 2016. “Trio Approach Reveals Higher Risk of PD in Carriers of Severe vs. Mild GBA Mutations..” Blood Cells, Molecules & Diseases, November. doi:10.1016/j.bcmd.2016.11.007. Mullin, Stephen and Anthony H V Schapira. 2015. “Pathogenic Mechanisms of Neurodegeneration in Parkinson Disease.” Neurologic Clinics of NA 33 (1). Elsevier Inc: 1–17. doi:10.1016/j.ncl.2014.09.010. Mullin, Stephen, and Anthony Schapira. 2015. “The Genetics of Parkinson's Disease..” British Medical Bulletin 114 (1): 39–52. doi:10.1093/bmb/ldv022. Pakpoor, Julia, Alastair Noyce, Raph Goldacre, Marianna Selkihova, Stephen Mullin, Anette Schrag, Andrew Lees, and Michael Goldacre. 2017. “Viral Hepatitis and Parkinson Disease.” Neurology, March, 10.1212/WNL.0000000000003848. doi:10.1212/WNL.0000000000003848. Porcari, Riccardo, Christos Proukakis, Christopher A Waudby, Benedetta Bolognesi, P Patrizia Mangione, Jack F S Paton, Stephen Mullin, et al. 2015. “The H50Q Mutation Induces a 10-Fold Decrease in the Solubility of Α-Synuclein..” Journal of Biological Chemistry 290 (4): 2395–2404. doi:10.1074/jbc.M114.610527. Manuscripts in preparation Mullin, Stephen, Katherine Lee, Laura Smith, Gayle De Souza, Phil Woodgate Vincenzo Libri Sarah Cable, Tom Foltynie, Anthony Schapira 2017 “Rationale and protocol for ambroxol in modification of Parkinson’s disease (AiM PD) trial.” Movement disorders Mullin, Stephen,, Laura Smith, Derralyn Hughes, Atul Mehta, Christos Proukakis, Huw R Morris, Vittorio Belloti, Steven