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iPSC derived cerebral organoids as a model of tauopathy

Lovejoy, Christopher Edward James; (2021) iPSC derived cerebral organoids as a model of tauopathy. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Insoluble, hyper-phosphorylated aggregates of tau are a pathological hallmark of a range of clinically diverse neurodegenerative diseases termed tauopathies, of which Alzheimer’s disease (AD) is the most common. The mechanisms linking neuronal death and tau dysfunction are not fully understood, but mutations uncovered in microtubule associated protein tau (MAPT) that cause aggressive frontotemporal dementia confirm a causative relationship between tau dysfunction and neurodegeneration. The tau protein exists as multiple protein isoforms in the adult human central nervous system (CNS), generated by alternative splicing of the MAPT gene. Disruptions to tau splicing are associated with a number of tauopathies, however, in vitro and in vivo models to understand the consequences of disrupted tau splicing have been lacking, due in part to species differences in tau splicing and the developmental regulation of tau in human neurons. Recently, the development of induced pluripotent stem cells (iPSC) has enabled the derivation of limitless numbers of human neurons with disease associated mutations of interest. The use of this system to model tauopathy has been challenging, in part due to the developmental regulation of tau splicing, with extended culture periods required for mature tau expression in iPSC derived neurons. Cerebral organoids are 3D based iPSC derived neuronal cultures, which help capture the heterogeneity and key aspects of architecture of the developing brain, such as distinct progenitor zones and lamination of neurons into distinct layers. We hypothesised that this may allow neurons to mature at a faster rate, resulting in earlier expression of all 6 isoforms of tau without extensive culture times. We investigated the utility of iPSC-derived cerebral organoids to model key aspects of tau biology. Cerebral organoids showed high variability in neuronal content and tau expression. To reduce this heterogeneity, we generated engineered cerebral organoids (enCORs), which utilise a floating scaffold to increase the efficiency of neural induction and reduce heterogeneity. We show that enCORs provide a robust and reproducible in vitro system for the analysis of tau expression and splicing in a 3D model. To investigate the effect of tau mutations, we generated enCORs from an isogenic series of iPSC with the MAPT 10+16 and P301S mutations. The presence of tau splicing mutations results in disease-associated alterations in tau expression, specifically a dose-dependent increase in 4R tau isoforms in the presence of the MAPT 10+16 variant. While the developmental regulation of tau splicing is conserved, maturation of tau splicing is accelerated in 3D cultures compared to 2D cultures. Finally, enCORs with coding mutations in MAPT are able to produce seed-competent tau species, suggesting enCORs recapitulate early features of tau pathology. In summary, enCORs provide a novel, robust in vitro system for the study of tau in development and disease.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: iPSC derived cerebral organoids as a model of tauopathy
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
URI: https://discovery.ucl.ac.uk/id/eprint/10122129
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