Structural and functional mitochondrial abnormalities associated with high levels of partially deleted mitochondrial DNAs in somatic cell hybrids.
Kearns-Sayre syndrome (KSS) is a progressive and ultimately fatal human encephalomyopathy that is associated with large-scale deletions of mitochondrial DNA (mtDNA). To gain new insights into the developmental pathobiology of this disease, we studied the maintenance and expression of deleted mtDNAs (delta-mtDNAs) in somatic cell hybrids generated by fusion of HeLacot cells with a KSS fibroblast clone containing both wild-type and delta-mtDNAs. We observed that delta-mtDNAs were preferentially maintained over the KSS wild-type mtDNAs (wt-mtDNAs) in almost all isolated hybrid clones. Mitochondrial metabolism was not compromised in hybrids containing as much as 70-79% delta-mtDNAs. Two clones containing more than 99% delta-mtDNA were severely deficient in oxidative phosphorylation and exhibited abnormal, enlarged mitochondria. These clones had undetectable levels of mtDNA-encoded polypeptides, but contained normal amounts of a nuclear DNA-encoded mitochondrial protein. The data suggest a nonrandom pattern of mtDNA segregation in the triplasmic hybrids and a correlation among delta-mtDNA, structural mitochondrial abnormalities, and mitochondrial dysfunction.
Department of Pathology, College of Physicians & Surgeons, Columbia University, New York, New York 10032.
S
S
Sancho
C T
CT
Moraes
K
K
Tanji
A F
AF
Miranda
D002455:Cell Division; D002478:Cells, Cultured; D004272:DNA, Mitochondrial / Q000235:genetics*; D006801:Humans; D006822:Hybrid Cells; D066298:In Vitro Techniques; D007625:Kearns-Sayre Syndrome / Q000235:genetics*; D008928:Mitochondria / Q000502:physiology* / Q000648:ultrastructure; D010101:Oxygen Consumption; D012150:Polymorphism, Restriction Fragment Length; D017384:Sequence Deletion
D004272:DNA, Mitochondrial