Figure 5. Cxcr4a and Cxcl12 are required for coronary vessel formation.

Endothelial cells migrate over the surface of the heart, but fail to form a vascular network in adult cxcr4a mutant fish (A, Sibling control and B, Mutant). As cxcr4a mutant endothelial cells emerge onto the surface of the heart in juvenile zebrafish they have an uncharacteristic shape appearing truncated and highly spiculated (C–F). Movie stills show abnormal migration of endothelial cells in the mutant (G). Unlike wildtype cells, cxcr4a mutant cells project and retract multiple processes in different directions while migrating over the ventricle (arrowheads). They often migrate individually in different changing vectors and fail to make and maintain connections between each other. cxcl12a; cxcl12b double mutants show general retardation in growth in comparison with siblings raised under the same (optimized) husbandry conditions (H). Unlike their siblings, no endothelial cells are observed on the surface of heart of cxcl12a/b double mutant fish (I, sibling; J, cxcl12a; cxcl12b double mutant). Italicized age indicates zebrafish are raised using optimized husbandry, body length in brackets. Scale bars 50, µm except in H, which is 10mm.