Cellular and molecular insights into neurodegeneration mediated by the C9orf72 gene mutation

Lead Research Organisation: University of Edinburgh
Department Name: Centre for Clinical Brain Sciences

Abstract

The inability to study living human brain material has been a major hurdle to developing new treatments for people living with presently incurable neurodegenerative conditions, such as the dementias and motor neurone disease. Recent major discoveries in stem cell technologies, including from people with inherited forms of disease, have opened exciting new approaches, improving our understanding of underlying disease mechanisms, as well as contributing to the quest to discover new treatments. It is now possible to generate from a blood sample or skin biopsy, first unlimited numbers of master stem cells, and then the specific nerve cells that are affected in disease (for example, motor neurones), enabling the study of 'disease in a dish.'

My proposed research will exploit this approach to study living human motor neurones derived from people with the most common inherited form of motor neurone disease, due to a faulty gene, called C9orf72. I will then rigorously compare these with motor neurones grown from stem cells where the gene defect has been corrected, as well as motor neurones derived from healthy volunteers. My research focus is two-fold.

First, the latest evidence points to there being a reduction in the length of the cell's outgrowths (akin to tentacles of an octopus) in motor neurone disease. However, this remains to be proven objectively.

Second, using state-of-the-art molecular and computing techniques, I will be able to reveal the nuts and bolts - key molecular pathways - going on inside the motor neurones by studying the blueprint of the production of various critical proteins. This will allow me to identify whether there are some common themes in motor neurone disease, since it is these avenues that will hold the promise for further research and, ultimately, for finding new treatments.

Technical Summary

Motor neurone disease or amyotrophic lateral sclerosis (ALS) is a rapidly progressive and incurable neurodegenerative disorder, characterised by paralysis, due to loss of motor neurones (MNs). The underlying mechanism of cell-type specificity and death is unknown.
The seminal discovery that a hexanucleotide, repeat expansion in the C9orf72 gene underlies the most common cause of familial ALS (and also another, non-motor, illness, frontotemporal lobar degeneration, FTLD) makes it an attractive model for the study of the cellular and molecular mechanisms of neurodegeneration.
Combining genetic discoveries with technological advances in human induced pluripotent stem cells (iPSCs) and genome editing offers unprecedented opportunities to develop new experimental human models of neurological disease. Specifically, a potentially robust approach to interrogate the consequences of mutations in C9orf72 expressed at physiological levels is to study MNs derived from iPSCs obtained from patients with ALS carrying the C9orf72 mutant gene on an isogenic control background, permitting direct causality to be assigned to any phenotype, since the only variable is the mutation of interest.
My proposed research aims to use my host group's already validated 3 independent patient-derived mutant C9orf72 iPSC lines, with isogenic pairs, to generate MNs. Based on recent observations from both my host group's laboratory and that of others, I hypothesise that, first, there is a common cellular (morphological) phenotype - that of reduced neurite outgrowth length - and, second, there is a common molecular signature as demonstrated by examining the transcriptome. A series of experiments will inform a final set of experiments, whereby, through overexpression/knockdown of identified candidate genes or targeted pharmacological manipulation(s) of pathways identified from the transcriptomic work, a successful rescue strategy can be demonstrated to reverse the cellular phenotypic deficit.

Planned Impact

The World Health Organisation regards neurological diseases as one of the greatest threats to public health. Moreover, neurodegenerative disease represents one of the greatest medical and economic burdens to the UK. Our understanding of the neurobiology of neurodegenerative disorders lags behind that of other neurological disorders, but there is an emerging interest into the discipline of 'regenerative medicine'. Motor neurone disease or amyotrophic lateral sclerosis (ALS) is a prototypical neurodegenerative disease of mid-adulthood, characterised by the progressive degeneration of motor neurones in the brain and spinal cord, and is invariably fatal, with death occurring typically 3-5 years after diagnosis. There is considerable overlap with dementia (frontotemporal lobar degeneration, FTLD), such that tackling this spectrum of disease is of significant scientific and clinical importance. Recent advances in induced pluripotent stem cell (iPSC) technology allows, for the first time, a rational approach to human disease modelling.

Impact on commerce and policy-makers

Despite its huge potential, the uptake of iPSC technologies by industry is rightly cautious, owing to concerns about standards and reproducibility. The work carried out in the proposed CRTF will address this by studying pathogenesis in 3 independent cell lines against an isogenic background. My host laboratory is active in raising the bar on cell standards, cross-validating SOPs, and developing phenotypic read-outs for high-content and high-throughput compatibility. They also have extensive links with Pharma; continued engagement (for instance by the attendance of Pharma partners at the annual Spring School) and translation of the research to industrial platforms will be a significant long term outcome of the Chandran-Hardingham group.

Impact on patients, carers and the public

The fact that iPSCs are patient-derived, places patients at the heart of the proposed project. iPSC technology utilises patient genetics in a way that has hitherto not been possible. Patients and carers will be engaged in the project directly through interaction with myself, as a clinician-scientist and at patient focus/support groups. More widely, I will inform and engage the public through print and online media (press releases, websites, blogs, and social media). The general public has become more aware of ALS as a result of the 'ice bucket challenge'. I will place an emphasis on explaining the technology in an accessible way, such that it can provide real hope for the future. Edinburgh Neuroscience hosts regular events engaging the public and patients with scientists.

Impact on the public and third sectors

My supervisors have formed partnerships with major charities, such as the Motor Neurone Disease Association (MNDA), MND Scotland and the Euan MacDonald Centre. I will actively contribute to these partnerships and believe that it is essential to have regular interactions with charities and their members, involving them in research activities, and meeting interested patients and their families/carers.

Impact on the economy

The economic burden of ALS alone provides a sound basis for increased research output. It is estimated that the maximum direct costs to the health and social services for a person with ALS is approximately £200,000 annually, and represents a maximum cost to health and social services in UK of £373 million a year, in addition to indirect costs to the economy of approximately £1.1 billion (Motor Neurone Disease Association). Adding to this is the current cost of dementia to the UK economy, of approximately £26 billion a year (www.alzheimers.org.uk), meaning that studying this disease spectrum that straddles diseases of both movement and cognition will have economic benefit in the longer term. iPSC technology allows for the research to be relevant, since it involves disease modelling in human (as opposed to animal) models

Publications

10 25 50
 
Description Ask the Experts session 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Patients, carers and/or patient groups
Results and Impact Ask the Experts panel session in Glasgow just prior to the international ALS/MND symposium. This was also live broadcasted online, and we received questions both from the audience and also via the web. The session was very well received with excellent feedback and has allowed for our research to be communicated to patients, stimulating further research, and also reigniting hope for people living with this devastating disease. It also allowed me to network with leaders in the ALS research field (fellow panellists: Professor Dame Pamela Shaw, Professor Orla Hardiman).
Year(s) Of Engagement Activity 2018
URL https://www.mndscotland.org.uk/research/ask-the-experts-2018/