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Neovascularization of the Xenopus embryo
O Cleaver1, K F Tonissen, M S Saha
1Institute for Cellular and Molecular Biology, University of Texas at Austin 78712, USA.
Summary
Vascular endothelial growth factor (VEGF) and its receptor Flk-1 (VEGFR-2) are crucial for embryonic blood vessel development. Their signaling pathways regulate both the formation and organization of the vascular system in Xenopus embryos.
Area of Science:
- Developmental Biology
- Molecular Biology
- Cell Biology
Background:
- Vascular endothelial growth factor (VEGF) and its receptor Flk-1 (VEGFR-2) are essential for embryonic vascular development.
- Gene knockout studies in mice demonstrate the critical role of VEGF and Flk-1 in vascular system formation.
Purpose of the Study:
- To investigate the expression patterns and roles of Xenopus VEGF and Flk-1 during early embryonic development.
- To examine the involvement of VEGF/Flk-1 signaling in both vasculogenesis and angiogenesis in Xenopus.
Main Methods:
- Cloning of Xenopus homologues of flk-1 and VEGF.
- Analysis of gene expression patterns throughout early embryonic development.
- Ectopic expression of VEGF in Xenopus embryos via microinjection.
Main Results:
- Flk-1 is expressed in endothelial precursor cells forming major embryonic blood vessels.
- VEGF expression is localized in tissues adjacent to flk-1-expressing cells.
- Expression of both genes is transient, correlating with vascular plexus formation and declining after circulation onset.
- Flk-1 is also expressed in intersegmental veins, suggesting a role in angiogenesis.
- Ectopic VEGF expression leads to the formation of large, disorganized vascular structures.
Conclusions:
- VEGF/Flk-1 signaling plays a significant role in both vasculogenesis and angiogenesis in the Xenopus embryo.
- Ectopic VEGF can disrupt the normal architecture of the developing vascular network, highlighting its regulatory function.