Drosophila as a model to understand the role of glial cells in neurodegeneration
Lead Research Organisation:
King's College London
Department Name: Developmental Neurobiology
Abstract
The nervous system in human and all complex organisms is made not only by nerve cells (neurons) but also by glial cells. Glia performs a number of important functions such as insulation, nutritive support and maintenance of the right balance of signalling substances. These functions are essential to maintain an healthy nervous system throughout our lifetime and are often disrupted in many degenerative diseases of the nervous system and also in normal ageing.
Most studies on glial cell functions are conducted in laboratory animals like mice. Strategies for replacing or reducing animal experiments usually involve growing and manipulating cells in a dish. However because the function of glial cells is so intimately connected to its effect on neurons, these replacement strategies are less straightforward because it it is necessary to put together and manipulate two or more cell types (neurons and different kinds of glia).
We propose instead to replace mice with a small invertebrate organism, the fruitfly. This laboratory organism has glia in its nervous system and this glia performs all the functions found in humans.
The fruitfly also contains an equivalent for about 70% of all genes known to be involved in human disease, it is economic and easy to maintain and manipulate, and has been widely used in many labs for over a century.
Our previous work has generated a genetic model for a rare human neurodegenerative condition in the fruitfly. This has shown dramatic deficits in glial cells, which shorten the lifespan of the fly and impair its movements. A sensible hypothesis is that malfunctioning glial cells do not interact properly with neurons and this compromises the function of the nervous system and reduces lifespan.
We propose to use our fly models as a tool for discovery to figure out the role of glia, and to identify those genes involved in the communication between glia and neurons that are essential for a healthy nervous system.
Whereas the specific pathology will be used as a convenient starting point, we have designed our project so that it can discover the mechanisms that guarantee a proper function of the nervous system in general. These findings may be considered also as targets for future pharmacological research that will exploit glia-neuron communication to improve the health of patients with neurodegenerative diseases.
If we are successful we will not need mice to study this issue in our lab and this will also encourage reducing the use of mice both in our lab and in other labs interested in these problems. It will be more interesting and straightforward to test whether what we find in flies is also true in mice, than starting a new investigation from the beginning in mouse. In the first case fewer animals will need to be used in experiments, because those experiments will not guided by suppositions, rather from the precise knowledge of how the same thing works in the fruitfly and therefore can be better planned.
In conclusion, our work is likely to be very important both for thinking about new ways to improve health in neurodegenerative conditions, and for reducing experiments on animals.
Most studies on glial cell functions are conducted in laboratory animals like mice. Strategies for replacing or reducing animal experiments usually involve growing and manipulating cells in a dish. However because the function of glial cells is so intimately connected to its effect on neurons, these replacement strategies are less straightforward because it it is necessary to put together and manipulate two or more cell types (neurons and different kinds of glia).
We propose instead to replace mice with a small invertebrate organism, the fruitfly. This laboratory organism has glia in its nervous system and this glia performs all the functions found in humans.
The fruitfly also contains an equivalent for about 70% of all genes known to be involved in human disease, it is economic and easy to maintain and manipulate, and has been widely used in many labs for over a century.
Our previous work has generated a genetic model for a rare human neurodegenerative condition in the fruitfly. This has shown dramatic deficits in glial cells, which shorten the lifespan of the fly and impair its movements. A sensible hypothesis is that malfunctioning glial cells do not interact properly with neurons and this compromises the function of the nervous system and reduces lifespan.
We propose to use our fly models as a tool for discovery to figure out the role of glia, and to identify those genes involved in the communication between glia and neurons that are essential for a healthy nervous system.
Whereas the specific pathology will be used as a convenient starting point, we have designed our project so that it can discover the mechanisms that guarantee a proper function of the nervous system in general. These findings may be considered also as targets for future pharmacological research that will exploit glia-neuron communication to improve the health of patients with neurodegenerative diseases.
If we are successful we will not need mice to study this issue in our lab and this will also encourage reducing the use of mice both in our lab and in other labs interested in these problems. It will be more interesting and straightforward to test whether what we find in flies is also true in mice, than starting a new investigation from the beginning in mouse. In the first case fewer animals will need to be used in experiments, because those experiments will not guided by suppositions, rather from the precise knowledge of how the same thing works in the fruitfly and therefore can be better planned.
In conclusion, our work is likely to be very important both for thinking about new ways to improve health in neurodegenerative conditions, and for reducing experiments on animals.
Technical Summary
Glial cells have evolved in close association with neurons in most sophisticated nervous systems and are essential for the development, proper functionality and maintenance of neuronal networks and of the whole nervous system. One of their key functions is to provide trophic support and buffering ability over time to neurons, which makes them a critical factor in homeostasis of the nervous system in ageing and for the onset and progression of neurodegenerative diseases.
Importantly for the 3Rs, because glial cell function is inevitably linked to that of its impact on neuronal cells and circuits, traditional cell culture approaches as a way or replacing animal experiments are less straightforward. As a consequence, virtually all information about glial cells in neurodegeneration has come from mouse studies.
We plan instead to to exploit our Drosophila model for dentatorubral-pallidoluysian atrophy (DRPLA) and a collection of microRNAs transgenic strains as a tool for discovery, to shed light on glial function and glia-neuron interactions in neurodegeneration, and as a solution for promoting replacement, and encouraging reduction, of animal experiments.
Our specific aims are:
1.To identify miRs and targeted genes of relevance in glia for polyglutamine neurodegeneration.
2.To identify miRs and targeted genes of relevance in neurons for polyglutamine neurodegeneration driven in glial cells.
3.To study the mechanism of action of the top miR(s)>genes network in glia-neuron interactions.
Although the paradigm we use is a rare human disease, our system is capable of identifying also general mechanisms that are relevant to any disease that involves glial malfunctioning and degeneration. In conclusion, in this project we will develop a research strategy of paramount importance for the 3R agenda, with a great potential for major findings in a key area of bio-medical research, of proven interest to biotechnological and pharmacological industry.
Importantly for the 3Rs, because glial cell function is inevitably linked to that of its impact on neuronal cells and circuits, traditional cell culture approaches as a way or replacing animal experiments are less straightforward. As a consequence, virtually all information about glial cells in neurodegeneration has come from mouse studies.
We plan instead to to exploit our Drosophila model for dentatorubral-pallidoluysian atrophy (DRPLA) and a collection of microRNAs transgenic strains as a tool for discovery, to shed light on glial function and glia-neuron interactions in neurodegeneration, and as a solution for promoting replacement, and encouraging reduction, of animal experiments.
Our specific aims are:
1.To identify miRs and targeted genes of relevance in glia for polyglutamine neurodegeneration.
2.To identify miRs and targeted genes of relevance in neurons for polyglutamine neurodegeneration driven in glial cells.
3.To study the mechanism of action of the top miR(s)>genes network in glia-neuron interactions.
Although the paradigm we use is a rare human disease, our system is capable of identifying also general mechanisms that are relevant to any disease that involves glial malfunctioning and degeneration. In conclusion, in this project we will develop a research strategy of paramount importance for the 3R agenda, with a great potential for major findings in a key area of bio-medical research, of proven interest to biotechnological and pharmacological industry.
Planned Impact
This proposal will have significant impact on the 3R agenda replacing animal experimentation in this current project and leading to a significant reduction in the future both in our lab, local institution and in the field.
Glial cell function is fundamental for the understanding of the nervous system and is of paramount importance in the field of neurodegeneration, widely regarded as a key research area for medical healthcare in Western countries.
Because glial cell function is inevitably linked to its impact on neuronal cells and circuits, traditional cell culture approaches as a way or replacing animal experiments are less straightforward for the intrinsic need of complex co-culture techniques and the difficulty of reconstituting in vitro the intricate glio-neuronal networks present in vivo. As a consequence, virtually all information about glial cell role in neurodegeneration has come from mouse studies.
Our work will demonstrate instead that Drosophila is a suitable model for advanced analysis of glia-neuron interaction in health and disease, and that experiments in this simple invertebrate can replace costly, long and ethically challenging mouse experiments. In addition this may help to also reduce mouse experiments to pinpointed verification of Drosophila results, which requires fewer animals and possibly more focused procedures than investigations entirely set up from the beginning in mouse.
In our lab we also work on DRPLA mouse models and are planning to investigate the role of glia in this pathology though a new conditional model. The studies proposed here in Drosophila will guide our future experiments in mouse limiting them to verification of specific hypothesis in a limited number of animals to achieve exclusively the necessary validation of evolutionary conservation of the mechanisms, miRs and genes implicated in Drosophila.
Of course we recognise that the differences between flies and mammals will be an important limitation and should always be considered when translating findings between models, and from models (whether vertebrate or invertebrates) to humans. However, Drosophila has already had an enormous impact in the field of neurodegeneration and it is estimated that ~70% of disease-causing genes in humans have a conserved orthologue in flies. Furthermore the relative genetic simplicity of Drosophila allows often a clearer insight into disease mechanisms bypassing the complexity of genetic redundancy.
This scheme can be the blueprint for many other researchers interested in glial cell function, not only in the field of neurodegeneration and we will actively advocate it by also distributing freely the large collection of tools already in our hands and those that we will generate for this project.
In a wider perspective our approach is applicable to all cases in which understanding a biological or medical issue requires simultaneous manipulation of more than one cell type interacting in complex in-vivo environments, i.e. muscle degeneration in neurological conditions, stem cell niche effects or inflammatory responses in several non-infectious diseases.
Should Drosophila be successful as a model for these complex in-vivo scenarios in which traditional cell culture methods are limited, it will be hard to underestimate the impact on 3R and ultimately the importance of our project in this trend.
Glial cell function is fundamental for the understanding of the nervous system and is of paramount importance in the field of neurodegeneration, widely regarded as a key research area for medical healthcare in Western countries.
Because glial cell function is inevitably linked to its impact on neuronal cells and circuits, traditional cell culture approaches as a way or replacing animal experiments are less straightforward for the intrinsic need of complex co-culture techniques and the difficulty of reconstituting in vitro the intricate glio-neuronal networks present in vivo. As a consequence, virtually all information about glial cell role in neurodegeneration has come from mouse studies.
Our work will demonstrate instead that Drosophila is a suitable model for advanced analysis of glia-neuron interaction in health and disease, and that experiments in this simple invertebrate can replace costly, long and ethically challenging mouse experiments. In addition this may help to also reduce mouse experiments to pinpointed verification of Drosophila results, which requires fewer animals and possibly more focused procedures than investigations entirely set up from the beginning in mouse.
In our lab we also work on DRPLA mouse models and are planning to investigate the role of glia in this pathology though a new conditional model. The studies proposed here in Drosophila will guide our future experiments in mouse limiting them to verification of specific hypothesis in a limited number of animals to achieve exclusively the necessary validation of evolutionary conservation of the mechanisms, miRs and genes implicated in Drosophila.
Of course we recognise that the differences between flies and mammals will be an important limitation and should always be considered when translating findings between models, and from models (whether vertebrate or invertebrates) to humans. However, Drosophila has already had an enormous impact in the field of neurodegeneration and it is estimated that ~70% of disease-causing genes in humans have a conserved orthologue in flies. Furthermore the relative genetic simplicity of Drosophila allows often a clearer insight into disease mechanisms bypassing the complexity of genetic redundancy.
This scheme can be the blueprint for many other researchers interested in glial cell function, not only in the field of neurodegeneration and we will actively advocate it by also distributing freely the large collection of tools already in our hands and those that we will generate for this project.
In a wider perspective our approach is applicable to all cases in which understanding a biological or medical issue requires simultaneous manipulation of more than one cell type interacting in complex in-vivo environments, i.e. muscle degeneration in neurological conditions, stem cell niche effects or inflammatory responses in several non-infectious diseases.
Should Drosophila be successful as a model for these complex in-vivo scenarios in which traditional cell culture methods are limited, it will be hard to underestimate the impact on 3R and ultimately the importance of our project in this trend.
Organisations
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ORCID iD |
| Manolis Fanto (Principal Investigator) |