Gregory2017_MMedSci Thesis_MolPath_Interrogating the spatial transcriptome of motor neurone disease.pdf

Description: Thesis submitted by Jenna M Degree in August 2017 for the degree of MMedSci in Molecular Pathology, at the University of Edinburgh.Abstract:Motor neurone disease is a neurodegenerative disease selectively affecting motor neurones resulting in denervation and rapidly progressive paralysis. A number of syndromic subtypes of disease have been described, the commonest being ‘limb-onset’ and ‘bulbar’ forms of the disease. In addition to physical symptoms, cognitive and behavioural deficits have been well described in over 50% of patients, with symptoms of frank frontotemporaldementia (FTD) in up to 15% of patients. The pathological mechanisms underlying the selective degeneration of motor neurones and the involvement of non-motor brain regions in this devastating disease are however poorly understood. Using a recent development in spatial RNA sequencing technology, called spatial transcriptomics (ST), it was possible to address these questions by analysing the transcriptome, with spatial resolution, of post- mortem brain tissue from patients with MND.Spatial transcriptomics (ST) analysis revealed sixteen significantly dysregulated transcripts in six disease-related pathways: (i) proteostasis, (ii) RNA/DNA-binding proteins, (iii) mitochondrial metabolism, (iv) extracellular matrix, (v) excitotoxicity and (vi) anti-apoptosis. Furthermore, targeted transcript analysis, using RNAScope, in postmortem brain and spinal cord tissue from MND cases and age and sex-matched controls, revealed a cell-type specific vulnerability of spinal motor neurons to excitotoxic stress. However due to the cell-type specific heterogeneity in expression of these key disease-related transcripts, across the brain and spinal cord of MND cases, these findings would not have been detected without spatial resolution, highlighting the importance of retaining spatial information when probing the pathogenesis of neurological diseases like MND.Taken together these findings reveal novel pathways in the pathogenesis of MND and shed light on the selective vulnerabilities of certain cell types to the disease process in MND, highlighting potential therapeutic and diagnostic targets.