Chemotaxis A Threshold for Attraction

Cell migration is precisely controlled in the developing brain. Caric et al. investigated the role of the epidermal growth factor receptors (EGFRs) in controlling cell migration in the developing rodent telencephalon. In tissue explants, cells expressing high levels of EGFRs (neural stem cells, glial cells, and neurons) move toward an EGFR ligand source, such as transforming growth factor-α (TGF-α), heparin-binding epidermal growth factor (HB-EGF), EGF, amphiregulin, or β-cellulin. This chemotactic response was apparent in cells from explants isolated at times when endogenous EGFR levels are high or in cells that had been transfected with EGFR to force high levels of expression, suggesting that there may be a threshold of EGFR expression that is required to mediate chemotaxis. Expression of EGFR is temporally regulated, and expression of the EGFR ligands is spatially controlled. If the number of cells that express high levels of EGFRs is expanded by viral transduction, then these cells are diverted into the radial migratory path to the cortical plate and ventrolaterally into the lateral cortical stream, consistent with a role for EGFR in chemotaxis. Thus, the authors propose that if the amount of EGFR expressed in vivo reaches the threshold required for chemotaxis, then these cells will migrate toward sources of EGFR ligand.

D. Caric, H. Raphael, J. Viti, A. Feathers, D. Wancio, L. Lillien, EGFRs mediate chemotactic migration in the developing telencephalon. Development 128, 4203-4216 (2001). [Online Journal]