Angiogenic network formation in the developing vertebrate trunk

Abstract

doi:10.1242/dev.00733 We have used time-lapse multiphoton microscopy of living Tg(fli1:EGFP) y1 Summary zebrafish embryos to examine how a patterned, functional network of angiogenic blood vessels is generated in the early vertebrate trunk. Angiogenic vascular sprouts emerge from the longitudinal trunk axial vessels (the dorsal aorta and posterior cardinal vein) in two spatially and temporally distinct steps. Dorsal aortaderived sprouts form an initial primary network of vascular segments, followed by emergence of vein-derived secondary vascular sprouts that interact and interconnect dynamically with the primary network to initiate vascular flow. Using transgenic silent heart mutant embryos, we show that the gross anatomical patterning of this networ

Catch of the day: zebrafish as a human cancer model

“…This model system is advantageous in that it provides a clear window to visualize mechanisms of microtumor formation, cell invasion and tumor-induced angiogenesis in a mature animal. Another advantage to using juvenile fish compared to using developing embryos is that all the major organs including the vasculature have completed development and have reached their mature pattern that is the same from animal to animal (Isogai et al, 2003). This makes interpretation of tumor-induced vascular effects uncomplicated and eliminates concerns with the perturbation of developmental processes.…”

Using a histone yellow fluorescent protein fusion for tagging and tracking endothelial cells in ES cells and mice

“…Maturation of embryonic blood vessels may also be hemodynamically determined (Isogai et al, 2003;Jones et al, 2004). Therefore, to understand in detail the dynamic events leading to vascular development in the mouse, it will be essential to image individual endothelial cells in live embryos.…”

“…Advances in microscopic imaging methods and improvements in genetically encoded fluorescent proteins have led to the development of powerful tools for studying cell behavior in live embryos. For example, endothelial-specific green fluorescent protein (GFP) reporters have proven useful for noninvasive observation of vascular development in zebrafish (Isogai et al, 2003;Lawson and Weinstein, 2002;Motoike et al, 2000). The uniform expression of GFP within the endothelial cells of these animals limits their utility in following cell movements: the position of a given cell can be tracked in three dimensions (3D) over time (i.e., in 4D) only if it is present among a group of nonexpressing cells, as in a mosaic or mixed-lineage population (e.g., see Anderson et al, 2000;Bak and Fraser, 2003;Hadjantonakis et al, 2001;Srinivas et al, 2004;Tam and Rossant, 2003).…”

Egfl7 knockdown causes defects in the extension and junctional arrangements of endothelial cells during zebrafish vasculogenesis

“…We hypothesize therefore that, in Egfl7 KD embryos, the ECs migrate in normal numbers to the region between hypochord and endoderm, at the midline of the trunk (Parker et al, 2004, and this study), but then miss a cue to take widely spread positions within the vascular area. The failure of the endothelia to extend and form a wide vessel lumen is probably not due to the lack of blood flow, because silent heart (sih) mutant embryos, which have no heart beat or blood circulation, form normal axial vessels with wide lumens (Isogai et al, 2003). The defect in extension of the endothelia in the KD zebrafish shows a striking analogy with the deficient vascular sprout extension recently demonstrated in Egfl7-knockout mice (Schmidt et al, 2007).…”