Scientists studying how developing blood cells migrate to their proper destinations in fruit flies have discovered the ancestral role of a protein better known for ensuring that tumors have adequate blood supply. The protein, called vascular endothelial growth factor (VEGF), has gained notoriety for guiding the development of new blood vessels that nourish cancerous tumors. When researchers block VEGF, the tumors blood supply is cut off because new blood vessels dont form.

Now scientists say that VEGF and its receptors also help direct individual blood cells to their destinations in developing fruit fly embryos. The researchers say that this may be VEGFs ancient function, and that only recently in evolutionary time did VEGF assume its role in blood vessel development. The results even suggest that ancestral blood cells may have evolved into blood vessels, says Howard Hughes Medical Institute investigator Mark A. Krasnow at Stanford University.

Nobody knows how blood vessels evolved, he said. Our idea is that some population of blood cells acquired the ability to form tubular structures through which the rest of blood cells could then move. Eventually the tubules invaded the heart to form the closed circulatory system that we know today.

Nam Cho, Krasnow and colleagues at Stanford University, and Felix Karim and colleagues at the South San Francisco-based biotechnology company Exelixis Incorporated reported their findings in the March 22, 2002, issue of the journal Cell.

Migration of mammalian blood cells in adult physiology has been studied intensely, but the really amazing long distance migration of blood cells during embryonic development, which appears to be a highly programmed process, is not understood at all, said Krasnow. We believe we have discovered a molecular basis for long-range blood cell migration.

The scientists first identified four
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
28-Mar-2002