title: Mitotic segregation of mitochondrial DNAs in human cell hybrids and expression of chloramphenicol resistance.
abstract: The relationship between the chloramphenicol (CAP)-resistant phenotype and the mtDNA genotype was investigated in segregating human, HeLa X HT1080, somatic cell hybrids. The parental mtDNAs were quantitated in heteroplasmic cells by using restriction fragment length polymorphisms (RFLPs) detected in Southern blots. CAP-resistant (R) X CAP-sensitive (S) hybrids selected and grown in CAP for brief periods had as little as 25% CAP-R mtDNA. With prolonged selection, the CAP-R mtDNA increased to 90-95%. Hybrids selected and passaged without CAP either retained both mtDNAs or progressively lost one mtDNA (mitotic segregation). The CAP-resistance phenotype of these hybrids changed abruptly when the proportion of CAP-R mtDNAs fluctuated around approximately 10% (threshold effect). Hybrids with greater than 25% HT1080 mtDNA had an additional characteristic. They cloned better with CAP than without. The cloning efficiency in CAP of hybrids having 90% HT1080 mtDNA was more than fivefold greater than the control.
mesh_terms: D002459:Cell Fusion; D002460:Cell Line; D002701:Chloramphenicol / Q000494:pharmacology*; D004262:DNA Restriction Enzymes; D004272:DNA, Mitochondrial / Q000235:genetics*; D004351:Drug Resistance; D005838:Genotype; D006367:HeLa Cells; D006801:Humans; D006822:Hybrid Cells; D008938:Mitosis; D010641:Phenotype
chemical_list: D004272:DNA, Mitochondrial; D002701:Chloramphenicol; D004262:DNA Restriction Enzymes