Electric Field-induced Fusion of Sea Urchin Eggs

An electrical method is described which permits the fusion of denuded eggs of the sea urchin species Paracentrotus lividus. In a nearly non-conductive medium, containing 1.2 M glucose at pH 6.0-8.4, eggs or fertilized stages are brought into close membrane contact by dielectrophoresis arising from the application of a highly inhomogeneous alternating electric field. During this process the eggs aligne parallel to the field forming "egg-chains". In well pigmented eggs pigmentcapping is observed in the areas of cell contact. After completion of the alignment, the application of an additional single high field pulse of μs duration induces fusion of two or more eggs. The mechanism underlying the fusion process is the reversible electric breakdown of membranes in the zones of cell-to-cell contact. Fusion proceeds within 1-10 min at 10-20°C. Fused eggs have intact nuclei, can be fertilized, but undergo abortive cleavage.