The Influence of Cytoplast-to-Cell Ratio on Cybrid Formation

Fusions in which one of the partners is a cytoplasmic fragment of a cell, or cytoplast, have been extensively used in recent years to investigate a variety of problems in biology. For example, cytoplasmic inheritance can be observed. Properties of a cell that can be transferred and maintained through its cytoplasm to a recipient cell are presumed to be controlled by cytoplasmic hereditary factors. Thus, cytoplasmic transfer of chloramphenicol (CAP) resistance in mouse and human cells suggested that mitochondrial DNA (mtDNA) controlled CAP resistance (Bunn et al., 1974; Wallace et al., 1975), and this suggestion has proved correct (Clark and Shay, 1980; Blanc et al., 1981). Similarly, the cytoplasmic transfer of murine intracisternal A particles (Malech and Wivel, 1976) and of microtubule-organizing centers (Shay et al., 1978) suggest at least a partial replicative autonomy for these particles.