Cellular and genetic analysis of central nervous system myelination in zebrafish
Lead Research Organisation:
University of Edinburgh
Department Name: Centre for Neuroregeneration
Abstract
The myelin sheath is a plasma membrane extension of specialized glial cells that wraps around neuronal processes, called axons: in so doing, myelin permits the rapid conduction of nerve impulses. Damage to myelin causes the symptoms of many human diseases including multiple sclerosis (MS) and Charcot-Marie-Tooth (CMT) neuropathies. Myelin formation (myelination) is a much more efficient mechanism than the alternative way to increase nerve conduction, namely increasing axon diameter. Large diameter axons take up space, which constrains the size and complexity of organism that can evolve using only this strategy. It is fair to say, therefore, that complex nervous systems, such as our own, have evolved in large part due to the properties of the myelin sheath. Understanding the mechanisms that control myelination is thus of both fundamental biological and medical relevance. The zebrafish is a powerful model organism in which to dissect the cellular and genetic basis of myelination. Zebrafish embryos are transparent, and tools exist to watch fluorescently labeled cells behave in real time in the living organism, at a level of detail that is not feasible in other vertebrate laboratory animals. A second major attraction of the zebrafish is the ability to carry out large-scale affordable genetic screens to find genes required for specific biological processes. In a genetic screen carried out in our lab we identified 10 genes required for the development of myelinated axons. Although we have learned a great deal our screen certainly did not have the scope to identify all the genes that regulate myelination. Our current understanding of the genetic and cellular basis of myelin formation in the central nervous system (the brain and spinal cord) remains particularly rudimentary. The overall goal of my proposal, therefore, is to determine the cellular and genetic basis of myelin formation in the zebrafish central nervous system. 1. I will directly observe the precise cellular interactions between axons and glial cells that culminate in myelination, by high-resolution time-lapse microscopy in zebrafish. 2. Previous studies have led to the intriguing hypothesis that the level of neuronal activity can regulate myelin production, which may represent a fundamental mechanism by which localized brain activity could enhance nervous system function. I will test this hypothesis in intact animals for the first time by altering levels of neural activity in zebrafish embryos and looking at the effects of different treatments on myelin production and on neurophysiology. 3. Recently a particular genetic pathway (the neuregulin-erbb pathway) has been implicated as a key regulator of myelin formation in the peripheral nervous system (the part of the nervous system outside of the brain and spinal cord), but its role in the CNS is somewhat controversial. I have exciting preliminary data that I will now fully explore that this fundamental regulatory pathway does indeed regulate myelination in the CNS. 4. We still do not know the identity of many of the genes that are required for myelination in the CNS. I will perform a new genetic screen in zebrafish and focus in particular on genes that are required for myelination in the CNS. By comparing animals with mutations in specific genes with normal animals by high-resolution analyses such as time-lapse microscopy I will be able to define exactly which aspects of myelination those genes are normally required for. I hope to set up my own independent research group at the University of Edinburgh, in laboratories that are part of a new £600m research development at the Little France Biomedical Sciences Centre. This environment will provide a world-class infrastructure, and I will be adjacent to two of the leading researchers in the field of myelin biology, which will provide an ideal environment of intellectual support and potential collaboration, to continue to unravel the mysteries of myelination.
Technical Summary
The myelin sheath is a plasma membrane extension of oligodendrocytes (OLs) in the central nervous system (CNS) and Schwann cells (SCs) in the peripheral nervous system (PNS) that wraps around axons to allow the rapid transmission of nerve impulses. Although we know much about their early development we know much less about how these cells interact with axons at later stages to regulate myelination, especially in the CNS. This proposal will address four primary questions. 1. What are the cellular bases of myelination in the CNS in vivo? A single OL typically extends many individual processes to generate multiple myelin segments, but how this process occurs in vivo is almost entirely unclear. I will carry out time-lapse imaging to characterise the precise cell behaviors that surround myelination. I will also test if axon diameter is an intrinsic property of neurons that prefigures myelination or is regulated by OLs. 2. What is the role of neural activity during myelination in vivo? Previous studies have suggested that neuronal activity may regulate myelination, but how this occurs in vivo remains unclear. I will examine myelination following inhibition of all neural activity in vivo and create chimeric animals with both active and inactive neurons within a nerve to determine if different levels of activity can regulate myelin production. 3. How does ErbB signaling regulate myelination in the CNS? In the PNS ErbB receptor signaling is required for myelination but its role during myelination in the CNS remains unclear. We have exciting preliminary data that treatment with a pan ErbB inhibitor reduces myelination in the CNS. I will determine which ErbB receptor(s) mediate this and which aspects of CNS development and myelination require ErbB function. 4. What genes are required for myelination in the CNS? I will carry out a genetic screen in zebrafish to identify genes specifically required for late stages of OL development that surround myelination.
People |
ORCID iD |
David Lyons (Principal Investigator) |
Publications
Almeida R
(2014)
On the resemblance of synapse formation and CNS myelination
in Neuroscience
Almeida R
(2016)
Oligodendrocyte Development in the Absence of Their Target Axons In Vivo.
in PloS one
Almeida RG
(2015)
Intersectional Gene Expression in Zebrafish Using the Split KalTA4 System.
in Zebrafish
Almeida RG
(2011)
Individual axons regulate the myelinating potential of single oligodendrocytes in vivo.
in Development (Cambridge, England)
Baraban M
(2016)
Adaptive myelination from fish to man.
in Brain research
Czopka T
(2013)
Individual Oligodendrocytes Have Only a Few Hours in which to Generate New Myelin Sheaths In Vivo
in Developmental Cell
Czopka T
(2011)
Dissecting mechanisms of myelinated axon formation using zebrafish.
in Methods in cell biology
Koudelka S
(2016)
Individual Neuronal Subtypes Exhibit Diversity in CNS Myelination Mediated by Synaptic Vesicle Release.
in Current biology : CB
Lyons DA
(2009)
Kif1b is essential for mRNA localization in oligodendrocytes and development of myelinated axons.
in Nature genetics
Mensch S
(2015)
Synaptic vesicle release regulates myelin sheath number of individual oligodendrocytes in vivo.
in Nature neuroscience
Description | Our work aims to understand mechanisms of nervous system development. We use zebrafish as a model organism, because they are a powerful system with which to carry out high-resolution microscopy in the living animal. Their embryos are small, transparent, and develop very rapidly. We have generated genetically modified fish that allow us to see by fluorescence specific cells of the nervous system in embryonic zebrafish as they develop without any surgical procedures. Zebrafish are also widely used as a system to discover what genes regulate specific biological processes and to test whether chemical compounds can affect specific biological processes. This is because zebrafish embryos are available in very large numbers, and, of course, develop in water, meaning, for example that many hundreds of chemicals can be tested for their effects on a biological process of interest. More specifically our interest lies in how our "white matter" is formed. Our white matter is primarily made up by myelinated axons. Nerve impulses in our brain and spinal cord are propagated along axons, and most of our axons are surrounded by a protective membrane called myelin that also acts as an insulator to allow rapid impulse propagation. By using zebrafish to study myelinated axon formation we have found that: 1. Axons control how much myelin is made by the myelin producing cells called oligodendrocytes. 2. Individual oligodendrocytes have a very short period in which to generate their myelin. 3. We have identified genes that promote myelin formation and genes that are required for myelin formation and axon development. 4. We have identified chemical compounds that promote myelination. |
Exploitation Route | Knowledge about how cells interact during nervous system development or specifically during white matter formation is important for understanding gene and chemical compound function and to understand cellular mechanisms of brain repair. The identification of genes and chemical compounds that regulate myelin formation is relevant to the development of therapies to promote myelin repair, which is an important goal, e.g. in the treatment of multiple sclerosis, and other diseases of myelin. |
Sectors | Healthcare Pharmaceuticals and Medical Biotechnology |
Description | We have generated a suite of transgenic zebrafish that have been shipped to over 30 laboratories world-wide for their use in basic bioscience research. |
First Year Of Impact | 2011 |
Description | ALERT 2014 |
Amount | £628,189 (GBP) |
Organisation | Biotechnology and Biological Sciences Research Council (BBSRC) |
Sector | Public |
Country | United Kingdom |
Start | 01/2015 |
End | 01/2016 |
Description | Innovative award |
Amount | £28,500 (GBP) |
Organisation | Multiple Sclerosis Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 09/2010 |
End | 09/2011 |
Description | International Progressive MS alliance |
Amount | $75,000 (USD) |
Organisation | National Multiple Sclerosis Society |
Sector | Charity/Non Profit |
Country | United States |
Start | 08/2014 |
End | 08/2015 |
Description | International Reintegration Grant |
Amount | € 100,000 (EUR) |
Organisation | European Commission |
Sector | Public |
Country | European Union (EU) |
Start | 04/2010 |
End | 04/2014 |
Description | Project grant |
Amount | £157,038 (GBP) |
Organisation | Multiple Sclerosis Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 01/2014 |
End | 12/2015 |
Description | Research Grant |
Amount | £15,000 (GBP) |
Organisation | The Royal Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 04/2012 |
End | 04/2013 |
Description | Research Prize |
Amount | £200,000 (GBP) |
Organisation | Lister Institute of Preventive Medicine |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 08/2012 |
End | 08/2017 |
Description | Senior Research Fellowship |
Amount | £1,930,597 (GBP) |
Organisation | Wellcome Trust |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 02/2014 |
End | 01/2019 |
Title | mbp:GFP |
Description | Transgenic zebrafish to visualise myelinating glial cells |
Type Of Material | Biological samples |
Year Produced | 2011 |
Provided To Others? | Yes |
Impact | Publications Use in screening assays Use by >30 international laboratories |
Title | mbp:GFP-CAAX |
Description | Transgenic zebrafish to visualise myelin sheaths |
Type Of Material | Biological samples |
Year Produced | 2011 |
Provided To Others? | Yes |
Impact | Publications Use in screening assays Distributed to over 40 laboratories worldwide |
Description | Becker |
Organisation | University of Edinburgh |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Expertise in coordinating mutagenesis screens in zebrafish Expertise in chemical screening using zebrafish |
Collaborator Contribution | New assays to identify genes and chemicals that regualte nervous system development in zebrafish |
Impact | Five direct collaborative funding awards: major equipment grant from BBSRC ALERT 2014, 2 strategic investments by the University of Edinburgh Institutional Support Fund and 2 by the RS MacDonald Trust. |
Start Year | 2012 |
Description | Biogen |
Organisation | Biogen Idec |
Country | United States |
Sector | Private |
PI Contribution | Use of zebrafish to discover genes and compounds that affect myelination and neuronal injury. |
Collaborator Contribution | Expertise in multiple sclerosis therapy development, chemistry and drug discovery and development |
Impact | An automated high-resolution in vivo screen in zebrafish to identify chemical regulators of myelination. Early JJ, Cole KL, Williamson JM, Swire M, Kamadurai H, Muskavitch M, Lyons DA. Elife. 2018 Jul 6;7. pii: e35136. doi: 10.7554/eLife.35136. PMID: 29979149 |
Start Year | 2013 |
Description | Franklin |
Organisation | University of Cambridge |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Use of zebrafish to identify compounds that promote myelination |
Collaborator Contribution | Expertise in myelination, overall project management and organisation of prospective drug development project |
Impact | NA to date |
Start Year | 2012 |
Description | Mahad |
Organisation | University of Edinburgh |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Expertise in live imaging myelinated axons |
Collaborator Contribution | Conceptual framework to test mitochondrial response to myelinated axon damage, tools and reagents. |
Impact | One successful funding application to the National Multiple Sclerosis Society |
Start Year | 2014 |
Description | Poole |
Organisation | University College London |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Gene discovery screen using zebrafish to identify molecular regulators of myelination. We carried out screen, identified mutants, prepared DNA for whole genome sequencing to identify causative mutations. |
Collaborator Contribution | Dr. Poole identified mutations causing mutant phenotypes by bioinformatic analyses of whole genome sequence datasets. |
Impact | Manuscripts in preparation |
Start Year | 2015 |
Description | Simons |
Organisation | Max Planck Society |
Department | Max Planck Institute for Experimental Medicine |
Country | Germany |
Sector | Academic/University |
PI Contribution | Expertise and reagents for the study of myelinated axons using zebrafish |
Collaborator Contribution | Expertise in cell biology of myelination |
Impact | Publication in Cell. Publication in Developmental Cell |
Start Year | 2012 |
Description | Talbot |
Organisation | Stanford University |
Country | United States |
Sector | Academic/University |
PI Contribution | Expertise in use of zebrafish to study myelinated axons |
Collaborator Contribution | Expertise in use of zebrafish to study myelinated axons |
Impact | Manuscript in revision at Current Biology relevant to BBSRC grant. |
Start Year | 2011 |
Description | ffrench-Constant |
Organisation | University of Edinburgh |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | Expertise in the use of zebrafish to study myelinated axons |
Collaborator Contribution | Expertise in myelin biology |
Impact | Collaborative manuscripts published in Development, Developmental Cell. Manuscript in preparation. |
Start Year | 2010 |