Factors controlling the electrofusion of murine embryonic cells

A wide variety of physical and biological factors are involved in determining the success of electrofusion procedures. The optimal conditions for the fusion and survival of mouse two-cell embryos have been determined by manipulating the electric field parameters, medium composition, degree of cell-cell contact and the relationship between current flow and membrane orientation. The experiments demonstrate that the events which initiate embryonic cell fusion are dependent upon a closely defined electric field strength and associated pulse duration. We show further that high cell fusion rates are the product of an inverse relationship between dc field strength and pulse duration and the initiation of pore formation by electric field application is insufficient to induce successful fusion unless accompanied by appropriate post-pulse medium and adequate membrane contact. Manipulation of the direction of current flow, membrane orientation and degree of cell-cell contact have shown that the initiation of pore formation occurs across the entire surface of the cell membrane.