Electrophoresis of proteins in intercellular bridges

Abstract

Cytoplasmic polarity giving rise at mitosis to daughter cells with distinct but complementary morphogenetic functions has been proposed by Jaffe and co-workers to have transcellular ion currents as one of its essential physiological steps¹. The clearest evidence is from fucoid eggs in which such currents have been shown to parallel the prospective axis of germination^2,3. The currents are caused by stabilized accumulations of cation pumps on one side of the cell, and of permeability channels on the opposite side⁴; they are strong enough to suggest that the accompanying gradient in electrical potential could have an electrophoretic effect on the distribution of cytoplasmic constituents, including those that serve as morphogenetic determinants. Although ion currents correlated with axes of morphogenesis have thus been clearly established, their effects on intracellular localizations and morphogenetic activity have remained speculative⁵. We report here evidence that an endogenously generated gradient in electrical potential in the oocyte–nurse cell syncytium of Hyalophora cecropia can, in fact, influence the distribution of soluble proteins in a cytoplasmic continuum.