During development, the mammalian circulatory system is fixed in place before blood-flow commences. Different sets of genes control artery and vein formation, long before the vessels can be distinguished on the basis of direction of blood flow. This understanding has been mainly due to the discovery that vascular endothelial growth factor (Vegf) is necessary for arterial development.
Now, in the June 1 issue of
Lawson et al. used transgenic zebrafish with fluorescent blood vessels to search for new genes involved in artery development. They found that a mutation in one gene,