Figure 1.

Vascular-specific zebrafish mutants identified by forward-genetic screening. A variety of different mutants affecting endothelial specification, differentiation, and patterning have been identified in the zebrafish, a few of which are shown here. In situ hybridization of 1-day-old wild-type (a) or cloche (clo) mutant (b) zebrafish with the vascular specific marker flk1 shows that the blood vessels are virtually absent in mutants. Confocal microangiography of 2-day-old wild-type (c) and violet beauregarde (vbg) mutant (d) zebrafish reveals enlarged primary vessels and lack of perfused secondary vessels in mutants (images shown are dorsal views of the head). In contrast, confocal microangiography of wild-type (e) and gridlock (grl) mutant embryos (f) reveals relatively normal cranial vasculature, but lack of trunk and tail circulation due to defects in the morphogenesis of the dorsal aorta. The grl gene (g) is expressed in the trunk dorsal aorta (arrows), but not in the adjacent trunk cardinal vein (arrowheads). Anterior is to the left in all panels.