David Wilkinson

 

Mechanisms of tissue organisation by Eph receptor and ephrin signaling

The formation and maintenance of organised tissues requires that different types of cells are kept in the correct location despite the proliferation and motility of cells that can cause intermingling. This is achieved through mechanisms that drive segregation to form sharp borders between distinct cell populations. Disruption of segregation mechanisms in disease leads to altered cell organisation, for example the invasion of metastatic tumour cells into other tissues. Eph receptor tyrosine kinases and ephrins underlie cell segregation and border formation in many tissues during vertebrate development and adult homeostasis. Upon interacting, Eph receptors and ephrins each transduce signals - termed 'forward' and 'reverse' signaling, respectively - potentially leading to bi-directional cell responses. Such signaling can segregate cells through the regulation of cell adhesion, cell repulsion and/or cortical tension. However, the intracellular pathways by which Eph receptors and ephrins regulate cell segregation have not been elucidated, and it remains unclear whether bi-directional or uni-directional signaling is required. 

Our studies seek to elucidate molecular mechanisms by which Eph-ephrin signaling underlies cell segregation and border formation. We focus on the developing hindbrain, in which Eph receptors and ephrins have critical roles in the formation of sharp segment borders, and in induction of boundary cells required to pattern neurogenesis. We use zebrafish as an in vivo model since it is amenable for combining gene manipulation and live imaging of cell behaviour. By use of Crispr/Cas9 technology, we have generated mutants for Eph receptors and ephrins implicated in hindbrain boundary formation, and created transgenic reporter lines for in vivo imaging. The aim of the Ph.D. project is to dissect roles and mechanisms of forward and reverse signaling in cell segregation in vivo. This will involve functional analysis of intracellular targets of Eph-ephrin signaling, and the generation of mutations that disrupt interactions of Eph receptors or ephrins with specific pathways. The findings will give new insights into how Eph-ephrin signaling underlies tissue organisation. The student will learn and apply powerful methods of gene manipulation and live imaging of cell behaviour in an amenable vertebrate model.

1. Taylor, H. B., Khuong, A., Wu, Z., Xu, Q., Morley, R., Gregory, L., Poliakov, A., Taylor, W. R. and Wilkinson, D. G. (2017)
Cell segregation and border sharpening by Eph receptor-ephrin-mediated heterotypic repulsion.
Journal of the Royal Society Interface 14: 20170338. PubMed abstract

2. Addison, M. and Wilkinson, D. G. (2016)
Segment identity and cell segregation in the vertebrate hindbrain.
Current Topics in Developmental Biology 117: 581-596. PubMed abstract

3. Cayuso, J., Xu, Q. and Wilkinson, D. G. (2014)
Mechanisms of boundary formation by Eph receptor and ephrin signaling.
Developmental Biology 401: 122-131. PubMed abstract

4. Terriente, J., Gerety, S. S., Watanabe-Asaka, T., Gonzalez-Quevedo, R. and Wilkinson, D. G. (2012)
Signalling from hindbrain boundaries regulates neuronal clustering that patterns neurogenesis.
Development 139: 2978-2987. PubMed abstract

5. Jørgensen, C., Sherman, A., Chen, G. I., Pasculescu, A., Poliakov, A., Hsiung, M., Larsen, B., Wilkinson, D. G., Linding, R. and Pawson, T. (2009)
Cell-specific information processing in segregating populations of Eph receptor ephrin-expressing cells.
Science 326: 1502-1509. PubMed abstract