Figure 10. Summary of the effect of expression of progranulin during vascular development.
The upper bar summarizes major landmarks in vascular development. VEGF and its receptors (yellow bar) are required for early vasculogenesis and for angiogenesis throughout development. Tie2 and its ligand angiopoietin (red bar) are required for cardiac development and for vessel stabilization, but not for early vasculogenesis (see text for details). When progranulin was expressed developmentally (purple bar) it had no effect on vasculogenesis, the formation of the primary capillary plexus, sprouting or endothelial-mesenchymal transition. Its major actions were on vessel size and structural stability in late embryonic and neonatal phases. The timing of its actions is therefore distinct from those of the well-established angiogenic growth factors, suggesting that its effect on vessel growth and stability constitutes a novel angiogenic pathway.