AV IDENTITY IN ESCS · Specification of Arterial Venous Identity in Embryonic Stem Cells
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2006-07-01 → 2007-10-30
- EU contribution
- €150,804
- Participants
- 1
- Scheme
- IIF
Lines connect the coordinator with its partners.
Results in brief
Final Activity and Management Report Summary - AV IDENTITY IN ESCS (Specification of arterial venous identity in embryonic stem cells)
Targeted inactivation of genes involved in cardiovascular development in mice frequently leads to abnormalities in blood flow. We recently showed that blood flow played a crucial role in shaping vessel morphology; thus the presence of flow defects generally prohibited the precise assignment of the role of the mutated gene product in the vasculature, since primary defects due to the gene could not be separated from secondary defects due to the flow abnormalities. In this research we developed a method to distinguish between genetic defects caused by targeted inactivation of the neuropilin-1 (Nrp-1) receptor and hemodynamic or blood flow defects occurring when the Nrp-1 gene was deleted in embryos. We showed that vessel remodeling defects occurred concomitantly with the onset of blood flow and caused death of embryos at 10.5 days of gestation. Using mouse embryo culture, we established that flow defects were already present as soon as the heart began to beat and continuous circulation was never established in the mutant mice. The geometry of yolk sac blood vessels was altered and remodelling into yolk sac arteries and veins did not occur. To separate flow induced deficiencies from those caused by the Nrp-1 mutation we arrested blood flow in cultured normal and mutant embryos and followed their vascular development. We found that loss of Nrp-1 function rather than flow induced the altered geometry of the vascular plexus. Endothelial cell migration, but not replication, was altered in Nrp-1 mutants. Gene expression analysis of endothelial cells isolated from freshly dissected wild type and mutants and after culture in no-flow conditions showed down-regulation of the arterial marker genes connexin-40 and ephrinB2 related to the loss of Nrp-1 function. This method allowed genetic defects caused by loss of function of a gene important for cardiovascular development to be isolated even in the presence of hemodynamic defects.
Data: CORDIS, © European Union
Project objective
During embryonic development, formation of a functional cardiovascular system is critical for survival. When genes essential for cardiovascular development are ablated, embryos die by mid-gestation. Interestingly, this includes ablation of genes for arterial-venous (AV) differentiation indicating that arteries and veins are specified very early in development and that this specification is essential for proper cardiovascular function. AV identity was originally believed to be a trait acquired through local environmental cues. Recent evidence, however, has put this belief into question since arterial markers are expressed by endothelial cells before the onset of erythroblast circulation.Though the initial AV identity of endothelial cells may be genetically pre-determined, this identity remains plastic during development such that it can be reversed by altering local flow dynamics. Thus, specification of arterial-venous fate involves a complex interaction between signalling molecules and blood flow dynamics. In order to understand the role of these various inputs, we suggest combining the use of embryonic stem (ES) cell culture with micro-electro mechanical systems (MEMS) to allow us to expose small populations of ES cells to control environmental and chemical cues. Using the MEMS technology, flow and pressure can be controlled in channels equivalent to the size of embryonic vasculature, between 50-100µm.This technology has previously been used to understand the reaction of individual endothelial cells to environmental cues, however has never been applied to ES cells in order to understand the role of mechanical forces in endothelial cell differentiation. This research will thereby investigate which signals, both mechanical and genetic, are necessary for proper AV differentiation and improve our understanding of this process in vivo.
Original text from CORDIS.
Participants
- INSTITUT NATIONAL DE LA SANTE ET DE LA RECHERCHE MEDICALE · PARISCoordinatorFrance
Links
Data: CORDIS, © European Union