Computational modelling of dopaminergic networks and exploring the effects of protein aggregates on the function of these neuronal circuits

Lead Research Organisation: University of Warwick
Department Name: School of Life Sciences

Abstract

This project will bridge the fields of experimental neuroscience and theoretical computational mathematical modelling. Patch Clamping will be used to explore the way in which dopamine neurons are connected and how they respond to protein aggregation. The project will also expand on previous neuronal microcircuit network work, both in the hippocampus and also of dopaminergic neurons in the SNc. Acquisition of such network information will be greatly assisted by the production of simplified computational models, which allow the production of large networks without requiring large amount of computational power.
In order to translate this initial electrophysiology data into a network model, matlab will be used to generate dynamic IV curves. These can then be compared across different cell types and conditions. We propose to modify the rEIF model, which is already published for pyramidal neurons in the hippocampus, but does not accurately describe the electrophysiological properties of dopaminergic neurons. It will need to be altered using the electrophysiology data to give accurate spike prediction and hence a reliable model.
Our initial experimental plan is to inject a-syn oligomers (Kaufman et al) into dopaminergic neurons and measure early changes in electrophysiology of the neurons over time. We also plan to inject tau oligomers into pyramidal cells to see how the aggregation affects the neuronal responses. As protein aggregation is a problem that develops primarily with increasing age, different ages of mice will be used to compare the response to the addition of oligomers.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
BB/M01116X/1 01/10/2015 30/09/2023
1782613 Studentship BB/M01116X/1 03/10/2016 31/03/2021 Emily Hill
 
Description I have undertaken three key projects as part of this awarded PhD:

Project 1: Whole-cell patch clamp recording was used to introduce known concentrations of recombinant oligomeric full-length tau-441 (oTau) into cortical neurons via the patch pipette. I measured changes to electrophysiological parameters, basal synaptic transmission and synaptic plasticity. This approach allowed the evaluation of the direct effects of oTau within a neural network that was otherwise free from tau pathology. In single CA1 cells, oTau increased input resistance and altered action potential dynamics. These results were not observed following the introduction of either vehicle or monomeric Tau. oTau introduced into presynaptic neurons induced a decrease in synaptic transmission. In contrast, introduction of oTau into postsynaptic neurons had no effect on basal synaptic transmission, but markedly impaired synaptic plasticity. Published in eNeuro (2019), Neuronline (2020)

Project 2: Following on from Project 1, I introduced alpha synuclein into dopaminergic neurons in the substantia nigra to look at the effects on electrophysiological properties. I worked with collaborators in the institute of mathematics (Warwick) to adapt exciting computational models to implement with this data to fully characterise the changes (manuscript in preparation).

Project 3: The substantia nigra (SN) and ventral tegmental area (VTA) are vital for the control of movement, goal-directed behaviour and encoding reward. Surprisingly I found that firing of neurons in these nuclei could be modulated by physiological changes in PCO2. CO2 is a waste product of cellular metabolism, and its levels in blood are a key regulator of breathing. Blood PCO2 can be detected by hemichannels of Connexin 26 (Cx26). Dopaminergic neurons (DNs) in the SN of young rodents (P7-10) express mRNA for Cx26 and Cx30 which are CO2-sensitive. By P17-21 the DNs express only CO2-insensitive connexins. Here we show that the DNs (at P7-10) possess functional Cx26 hemichannels that allow physiological variations of CO2 to modulate their excitability. As predicted from their connexin mRNA profile, their CO2 sensitivity at later ages. Unexpectedly, we found a nearby population of GABAergic neurons in the VTA which also possess CO2 sensitive hemichannels of Cx26. These neurons retain their CO2 sensitivity throughout postnatal development. Our findings reveal an unexpected role for CO2 in regulating the activity of these key brain regions and demonstrates a mechanism by which autonomic state can alter complex movement-related and goal-directed behaviours (manuscript in review, iScience)

I also have 3 additional papers:
• Role of A1 receptor activated GIRK channels in the suppression of hippocampal seizure activity (published 2020, Neuropharmacology, 1st author)
• Non-opioid analgesia based on Ga signalling bias (in review, Science, 2nd author)
• Design and characterisation of a plasmid library for producing tau protein variants (in review, 3rd author)

I have co-authored 2 successful small project grants to ARUK (£5000) for my tau project and have numerous collaborations on projects outside of the scope of the PhD project with groups in The University of Tromso, University of Gothenburg and the Human Microbiome institute in New York.
Exploitation Route I will have published 7 papers by the end of my award. I have a number of projects still on the go that will yield further publications. I have presented this work at 4 conferences over the course of my PhD (ARUK, ADPD, BNA and SfN) I hope to build on my findings through grant and fellowship applications.
Sectors Healthcare

 
Description ARUK Small project grant
Amount £5,000 (GBP)
Organisation Alzheimer's Research UK 
Sector Charity/Non Profit
Country United Kingdom
Start 02/2020 
End 02/2021
 
Description ARUK midlands network small project grant
Amount £5,000 (GBP)
Organisation Alzheimer's Research UK 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2018 
End 07/2018
 
Description Extension to the tau project. 
Organisation University of Gothenburg
Country Sweden 
Sector Academic/University 
PI Contribution I completed all of the initial work for the paper published in eNeuro, 2019. I came up with the ideas and designed all of the research for this collaboration. I aim to test different truncations of tau to understand the mechanisms underlying the observations in the paper. I will also use human Alzheimers disease tissue to validate the results with my recombinant tau.
Collaborator Contribution I was provided with the truncations of tau and CSF samples by my collaborators
Impact eNeuro paper out, more to come
Start Year 2019
 
Description Metal mapping of human Lewy Body pathology 
Organisation University of Warwick
Country United Kingdom 
Sector Academic/University 
PI Contribution Assisted in the training of other group members and performed the staining of Parkinsons disease samples for Lewy body mapping with IHC. Assisted in data collection at the run (Diamond) to carry out the mapping study
Collaborator Contribution I joined the group for this project, this is their field. All other data collection was completed by the group
Impact Collaboration between myself (Life Sciences) and the Collingwood group in Engineering. No outcomes yet, publications hopefully in the future
Start Year 2019