From migration to circulation

Apathway required for blood vessel development in vertebrates also functions in flies, according to new results from Nam Cho, Mark Krasnow (Stanford University, Stanford, CA), and colleagues. The results imply that cell migration, not angiogenesis, may have been the original function of the vascular endothelial growth factor receptor (VEGFR) tyrosine kinase family and its ligands.

The active migration of bloodcells, or hemocytes, occurs during fly embryogenesis when the heart has not yet begun pumping. Fly blood does not travel through a closed circulatory system, but Cho found that flies have homologues of the VEGF pathway, which is required for vertebrate blood vessel development. This suggests that the proteins have a more ancient function.

That function appears to be the migration of blood cells during embryogenesis, according to the new study. Cho and colleagues...