Enucleation of mammalian cells by cytochalasin B. II. Formation of hybrid cells and heterokaryons by fusion of anucleate and nucleated cells

The development of methods for the formation of hybrid cells and heterokaryons by virus-induced fusion of chemically-enucleated cells and nucleated cells has been described. Heterokaryons and hybrid cells formed by fusion of anucleate mouse peritoneal macrophages (MPM) and nucleated mouse L and human HEp-2 cells were identified by mixed haemadsorption, by their sensitivity to trypsin and by their capacity to ingest antibody-coated sheep red blood cells. The expression of macrophage markers in these cells declined rapidly after fusion. Hybrid cell and heterokaryon formation was identified in mixed cultures of anucleate L cells and nucleated MPM, and was accompanied by the reactivation of DNA synthesis in the macrophage nuclei. Other hybrids and heterokaryons were formed by virus-induced fusion of anucleate MPM and nucleated chick embryo erythrocytes and anucleate L cells and nucleated HEp-2 cells. The value of anucleate-nucleate cell hybrids in the study of metabolic and genetic regulation in mammalian cells is discussed.