Segregation of mitochondrial DNAs carrying a pathogenic point mutation (tRNA(leu3243)) in cybrid cells.
To investigate the mechanism of segregation of mitochondrial DNAs (mtDNAs) carrying a pathogenic point mutation in the tRNA(leu(UUR)) gene (A to G at position 3243) cytoplasts, derived from a heteroplasmic myoblast clone, were fused to rhoo cells to create cybrid cells carrying different proportions of mutant and wild-type mtDNAs. Although the individual myoblasts used as fusion partners contained predominantly mutant mtDNAs (mean proportion 0.77, range 0.46-0.94), the majority (56%) of the cybrid clones isolated after growth in selective medium were homoplasmic wild-type, indicating preferential replication of wild-type mtDNAs. Long-term culture of heteroplasmic cybrid clones in non-selective medium produced no change in the mean proportion of wild-type mtDNAs but an increase in population variance, consistent with a purely stochastic segregation mechanism. These results are at variance with a previous report suggesting a replicative advantage for mtDNAs carrying the tRNA(leu3243) point mutation.
Shoubridge
E A
EA
Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada.
D000225:Adenine; D000818:Animals; D001859:Bone Neoplasms; D002459:Cell Fusion; D002999:Clone Cells; D004272:DNA, Mitochondrial / Q000235:genetics*; D005838:Genotype; D006147:Guanine; D006801:Humans; D006822:Hybrid Cells; D009132:Muscles / Q000378:metabolism*; D012516:Osteosarcoma; D017354:Point Mutation; D012356:RNA, Transfer, Leu / Q000235:genetics*; D014407:Tumor Cells, Cultured
D004272:DNA, Mitochondrial; D012356:RNA, Transfer, Leu; D006147:Guanine; D000225:Adenine