Isolation and characterization of intraspecific cybrids. Effect of mitochondrial DNA on their cellular properties.

Cybrid clones were obtained by fusing whole cells of rat glioma C6BU-1, resistant to 5-bromodeoxyuridine (BrdU), with cytoplasts of embryonic rat 3Y1CAP cells, resistant to chloramphenicol (CAP), in selective medium with BrdU and CAP. The clones resistant to BrdU and CAP were confirmed to be cybrids by chromosome and mtDNA analyses. More than half the mtDNA of all the cybrid clones was from the 3Y1CAP cells. After cultivation of a cybrid clone Y22 for 3 months in the absence of CAP, subclones were isolated. One subclone Y22-22 contained predominantly mitochondrial DNA (mtDNA) from the 3Y1CAP cells. Using this subclone, the effects of the mitochondrial genome on cellular properties were examined. The growth patterns, expression of glioma-specific beta-adrenergic receptor, and composition of the major proteins of C6BU-1 cells were not affected by transmitted mtDNA from the 3Y1CAP cells. This procedure for isolating cells containing predominantly foreign mtDNA will be useful in studies on the interaction between genomes of the mitochondria and nucleus.