Use this URL to cite or link to this record in EThOS:
Title: Notch signalling dynamics during sprouting angiogenesis
Author: Ubezio, B.
ISNI:       0000 0004 5363 7937
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2014
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Restricted access.
Access from Institution:
During sprouting angiogenesis endothelial tip and stalk cells specification is regulated by a lateral-inhibition system involving Dll4/Notch and Vegf signalling pathways, the Vegf-Dll4/Notch negative feedback loop. Experimental observations and computational modelling have recently illustrated how this process is predicted to be extremely dynamic and exquisitely sensitive to Vegfa. In this study, we combined several in vitro and in vivo approaches in order to dissect the dynamic regulation of Dll4/Notch signalling driven by Vegfa, and to analyse the effects that this regulation has on vessel morphology. By measuring total Dll4 mRNA and protein levels in cultured endothelial cells, we initially demonstrated that Dll4/Notch dynamic activity is regulated by Vegfa in a dose-dependent manner in vitro. We then generated two novel fluorescence Dll4 reporters and by monitoring the relative signals within ES-derived sprouting embryoid bodies, we showed that Dll4 expression fluctuates in individual endothelial cells in correlation with dynamic cell movement. Importantly, we also found that Notch signalling activity, through the Vegf-Dll4/Notch feedback system, undergoes a phase transition between two distinct operational modes, depending on Vegfa concentration: physiological Vegfa levels lead to highly differential, ‘single cell’ Dll4 dynamics, associated with sustained sprout elongation and branching, while pathologically high Vegfa levels result in Dll4 synchronised fluctuations between clusters of cells, leading to sprouting and branching disruption and vessel enlargement. Finally, since we could observe synchronised cell clusters of Dll4 expression by Dll4 reporter and protein staining in the vessel expansions of Vegfa-injected and retinopathy model retinas, we suggested that synchronization is an important principle of vessel malformation in disease. We anticipate therefore that a better understanding of Notch signalling dynamics and its dependence on Vegfa concentrations will have important therapeutic implications.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available