Guidance by Galvanotaxis - Mechanisms of Morphogenesis - page 111

FIGURE 10.2 A DC electric field can cause asymmetric diffusion of a charged molecule. The figure assumes
a net positive charge, which is typical of growth factors.
of neurons placed in an electric field. 15 What is more, blocking this accumulation abolishes
the galvanotactic response. The principle Con A-binding receptors of these growth
cones are the acetylcholine receptors, 13 suggesting that, in this case at least, the electric field
controls the direction of migration by causing an unequal distribution of receptors for chem-
ical attractants. Similarly, the EGF receptors of human keratinocytes are drawn to the cath-
odal side of the cell. 11,14 As far as the internal machinery of a cell is concerned, an induced
accumulation of receptors for a potential chemoattractant would have the same result as
an external gradient of that chemoattractant; symmetry would be broken, and internal
gradient would be established and the cell would move in that direction ( Figure 10.3 ).
The redistribution of receptors as a means of coupling electric fields to directed migration
is an intriguing model, but needs to be interpreted with caution because simple correlation of
FIGURE 10.3 Direct current electric fields bias the distribution of acetylcholine receptors (AchR) on growth
cones. They have a similar effect on EGF receptors on keratinocytes.