Time and mode of fusion of human fibroblasts treated with polyethylene glycol (PEG)

SOMATIC cell fusion has become a powerful tool in cell biology and genetics1–3 Until recently the standard reagent for increasing the rate of fusion in cultures of animal cells was inactivated Sendai virus4. In 1974 polymers of ethylene glycol (polyethylene glycol, PEG), over a wide range of molecular weights, were shown to be very effective, non-toxic chemical ‘fusogens’ for higher plant protoplasts5. They were then applied to fuse hen erythrocytes6 and these with yeast protoplasts7. Applied to mammalian, including human, cultured somatic cells they yielded hybrid cells capable of indefinite multiplication8,9. Applied to somatic cell protoplasts of two species of higher plants, they yielded hybrid protoplasts which regenerated, multiplied and developed into whole hybrid plants10. The list of cells and cell organelles fused has now expanded to include bacterial and fungal protoplasts and chloroplasts. It is reasonable to expect that PEG will induce the fusion of almost any two biological membranes and become an increasingly useful tool in their investigation6,11.