Molecular analysis of segmentation in the vertebrate embryo

Lead Research Organisation: MRC National Inst for Medical Research

Abstract

A central question in developmental biology is how different types of cells are organised and maintained in specific patterns during embryogenesis. One mechanism used during animal development is to subdivide a tissue into a series of building blocks, known as segments, that each later form a similar set of cell types. The main interest of this laboratory is to understand the molecular mechanisms that underlie a segmentation of tissue that occurs in part of the developing vertebrate nervous system, the hindbrain.|Our major strategy has been to identify genes that are active in specific hindbrain segments, and then to analyse their function by a variety of approaches. This has led us to identify a family of molecules involved in cell-cell communication between segments. We have shown that these molecules prevent cells in adjacent segments from intermingling, thus preventing a scrambling of the precisely organised pattern of segments. These molecules have similar roles in other tissues, and are likely to be of general importance for maintaining patterns during development.

Technical Summary

The subdivision of tissues into repeated building blocks, or segments, is an important and widely-used mechanism for organising tissues during animal development. The main interest of this laboratory is to identify and analyse molecular mechanisms involved in segmentation of a region of the vertebrate nervous system: the hindbrain and its derivatives. The subdivision of the hindbrain into segments underlies the organisation of nerves within this tissue, as well as of neural crest cells, a population of cells that migrate from the hindbrain to form parts of the peripheral nervous system and head skeleton. Understanding of hindbrain segmentation therefore has general implications for mechanisms that organise cells in the nervous system and in craniofacial development. Our major strategy has been to first identify candidate genes potentially involved in segmentation based upon their segmental expression in the developing hindbrain and/or neural crest. A variety of approaches are then taken to investigate the function of these genes, and mechanisms that regulate their expression. These approaches involve the use of several vertebrate model systems that have distinct experimental advantages for gain and loss of gene function experiments and for visualising developmental processes: zebrafish, Xenopus, chick and mouse. In previous work we identified Eph receptor tyrosine kinases that are segmentally expressed in the hindbrain. These receptors mediate intercellular signalling upon interacting with membrane-bound ligands, called ephrins, which can themselves transduce signals. Collectively, members of the Eph receptor and ephrin gene families are expressed in complex patterns in all developing tissues. Certain Eph receptors and ephrins are expressed in complementary sets of hindbrain segments, such that they interact at the interfaces between segments. We showed that Eph receptors and ephrins prevent the intermingling of adjacent cell populations in the early embryo, in neural crest cells and in the hindbrain. This restriction of cell intermingling prevents segments from scrambling with each other, thus enabling a sharp pattern to form and be maintained. In addition, we showed that Eph receptors and ephrins regulate cell communication via gap junctions. It has emerged that Eph receptors and ephrins have general roles in regulating repulsion and adhesion responses that control the movement of cells and neuronal growth cones during development. In ongoing work we are analysing biochemical mechanisms by which Eph receptors and ephrins control cell responses, and roles of these responses in vertebrate embryogenesis. In order to study the dynamic regulation of cell behaviour we are using in vivo confocal imaging and transgenic techniques to visualise cells during development. The work is on fundamental mechanisms of embryo development that has long term implications for understanding of normal development and genetic disorders. Part of our work (on Eph receptors and ephrins) may be relevant to neuronal regeneration after injury, and to the migration of tumour cells during metastasis.

Publications

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Breau MA (2013) A Hox gene controls lateral line cell migration by regulating chemokine receptor expression downstream of Wnt signaling. in Proceedings of the National Academy of Sciences of the United States of America

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Foster KE (2010) EphB-ephrin-B2 interactions are required for thymus migration during organogenesis. in Proceedings of the National Academy of Sciences of the United States of America

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Gerety SS (2013) An inducible transgene expression system for zebrafish and chick. in Development (Cambridge, England)

 
Description Marie Curie EU-Intra-European Fellowship
Amount £140,649 (GBP)
Organisation Marie Sklodowska-Curie Actions 
Sector Academic/University
Country Global
Start 07/2008 
End 06/2010
 
Title Eph-ephrin 
Description Stable cell lines for analysing cell responses and biochemistry of Eph-ephrin signaling 
Type Of Material Cell line 
Year Produced 2008 
Provided To Others? Yes  
Impact Collaboration leading to paper published in Science 236, 1502-1509 (2009) 
 
Description Eph-ephrin sorting 
Organisation Mount Sinai Hospital (Canada)
Department Samuel Lunenfeld Research Institute
Country Canada 
Sector Hospitals 
PI Contribution Development of cell sorting assay, provision of reagents and advice.
Collaborator Contribution Proteomic and siRNA screen to identify targets of Eph-ephrin signaling
Impact Not in PubMed yet. Science 326, 1502-1509 (2009)
Start Year 2008
 
Description Neuronal inhibition of neurogenesis 
Organisation Duke University
Country United States 
Sector Academic/University 
PI Contribution We identified a novel feedback mechanism that regulates neurogenesis.
Collaborator Contribution They provided a mutant zebrafish line and generated and provided transgenic lines that enable inducible blocking or activation of FGF signaling.
Impact Publication in press (Developmental Cell)
Start Year 2007
 
Description Role of Lunatic Fringe 
Organisation Helmholtz Association of German Research Centres
Department Helmholtz Zentrum Munchen
Country Germany 
Sector Public 
PI Contribution We identified a novel role of the Notch modulator, Lfng, in the lateral inhibition of neurogenesis
Collaborator Contribution Our collaborator generated and provided transgenic zebrafish lines to enable gene expression in specific hindbrain segments
Impact 19553285
Start Year 2007
 
Description Role of T-cadherin 
Organisation Moscow State University
Country Russian Federation 
Sector Academic/University 
PI Contribution We collaborated to study roles of T-cadherin - they analysed in vivo roles in angiogenesis, we studied roles in a cell culture model and during development.
Collaborator Contribution We collaborated to study roles of T-cadherin - they analysed in vivo roles in angiogenesis, we studied roles in a cell culture model and during development.
Impact 17486418
 
Title Btbd6 
Description Btbd6 targets degradation of protein implicated in leukeamia. However, MRCT concluded that the discovery is not suitable for protection. 
IP Reference  
Protection Protection not required
Year Protection Granted
Licensed No
Impact None.
 
Description Art/Science 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Film based on D'Alemberts Dream

Shown in art/science events
Year(s) Of Engagement Activity 2006
 
Description School visit - Bedford 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Talk to school children

Positive feedback from school.
Year(s) Of Engagement Activity 2009
 
Description Talk to school teachers 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Talk at Association for Science Education conference

No subsequent impact
Year(s) Of Engagement Activity 2006
 
Description U3A 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Talk to U3A

Positive feedback from audience
Year(s) Of Engagement Activity 2009