Fusion of human cells with Haplopappus protoplasts by means of Sendai virus

Plant-Animal Cell Fusions

The successful fusion of plant protoplasts and animal cells depends on a variety of factors. A method using high pH, high Ca2+ concentration and raised temperature has advantages over the polyethylene glycol method first used to fuse plant and animal cells. Electric field-induced fusion will perhaps be superior to both methods. The readiness with which the two different cytoplasms fuse was found to influence the success of interkingdom fusions; the high pH/high Ca2+ method leads to more rapid and complete cytoplasmic fusion than the polyethylene glycol method. Immunofluorescence studies of the extent of plasma membrane interaction in plant-animal heterokaryons have been made, using antibodies to animal cell membrane components. The influence of the culture medium on the survival of plant-animal heterokaryons and on the dominance of one or other cell partner has also been investigated. Further studies should indicate whether both genotypes are functioning in such interkingdom heterokaryons.

Fusion between human and Drosophila melanogaster cells induced by polyethylene glycol

Polyethylene glycol was used to induce interspecific somatic cell fusion between human fibroblasts (stock F6) and Drosophila melanogaster cells from established cell lines (Cl 82 and 11 P102), characterized by different ploidy levels. The present investigation defines some parameters for Drosophila cell fusion and interspecific fusion between Drosophila and human cells. The cytological analysis provided evidence of spontaneous as well as induced human-Drosophila heterokaryon formation. The presence in the same cell of two types of nuclei, distinguishable because of their different size and morphology, was confirmed autoradiographically by 3H-thymidine pre-labelling of Drosophila cells. Furthermore, the retained DNA synthetic activity and some examples of mitotic figures of both types of nuclei in the heterokaryons indicate the viability of the fused cells.

Transfer of antibiotic resistance genes between yeast and mammalian cells under conditions favoring cell fusion

Antibiotic resistance to G418 has been transferred into Chinese hamster cell lines via a plasmid vector. The same plasmid, which also contained the Leu2 gene, has been used to transform Leu2- yeast (strain MC16) to leucine prototrophy. Subsequent fusion between transformed yeast and untransformed hamster cells demonstrated that plasmid DNA could be transferred and its genes expressed within the mammalian cell genome. The fusion of transformed hamster cells with untransformed MC16 yeast cells demonstrated that DNA integrated within the mammalian cell genome could be transferred to correct the Leu2 deficiency and also confer G418 resistance on some yeast colonies.

Hybridization frequencies of Chinese hamster and mouse fibroblasts fused with polyethylene glycol at different cell densities

We have determined the effect of parental cell concentration at the time of fusion with polyethylene glycol on the frequency of viable somatic hybrids and of polykaryocytes of different multiplicity, between Chinese hamster (line Wg3) and mouse (line 3TP) fibroblasts. Fusion appeared to be dictated by the random encounter of cells only at low cell concentrations. However, no evidence for species-specific restriction of fusion was obtained at any cell concentration.

DNA synthesis and division in interkingdom heterokaryons

Drosophila cells and plant protoplasts were fused by polyethylene glycoldimethylsulfoxide treatment. DNA synthesis in plant and animal cells and in their heterokaryons were monitored by [3H]thymidine autoradiography. In appropriate media both the parental cells and the heterokaryons preserved their DNA synthetic activity. Division of the heterokaryons were also observed.

Effects of pH, Ca2+, temperature, and protease pretreatment on interkingdom fusion

The incubation of carrot protoplasts and cultured Xenopus cells in a protease solution has been shown to enhance their subsequent interkingdom fusion by a high pH/high Ca2+ method. The effects of Ca2+ concentration, pH, and temperature on the frequency of heterokaryon formation have also been studied. Potentially viable heterokaryons have been repeatedly produced at high frequencies (consistently greater than 10%), far exceeding those so far achieved in PEG-mediated fusion. Cell aggregates are readily dispersed after this method of fusion, permitting the accurate estimation of fusion frequencies.