Detection and quantification of heteroplasmic mutant mitochondrial DNA by real-time amplification refractory mutation system quantitative PCR analysis: a single-step approach.
BACKGROUND
The A3243G mitochondrial tRNA leu(UUR) point mutation causes mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, the most common mitochondrial DNA (mtDNA) disorder, and is also found in patients with maternally inherited diabetes and deafness syndrome (MIDD). To correlate disease manifestation with mutation loads, it is necessary to measure the percentage of the A3243G mtDNA mutation.


METHODS
To reliably quantify low proportions of the mutant mtDNA, we developed a real-time amplification refractory mutation system quantitative PCR (ARMS-qPCR) assay. We validated the method with experimental samples containing known proportions of mutant A3243G mtDNA generated by mixing known amounts of cloned plasmid DNA containing either the wild-type or the mutant sequences.


RESULTS
A correlation coefficient of 0.9995 between the expected and observed values for the proportions of mutant A3243G in the experimental samples was found. Evaluation of a total of 36 patient DNA samples demonstrated consistent results between PCR-restriction fragment length polymorphism (RFLP) analysis and real-time ARMS-qPCR. However, the latter method was much more sensitive for detecting low percentages of mutant heteroplasmy. Three samples contained allele-specific oligonucleotide-detectable but RFLP-undetectable mutations.


CONCLUSIONS
The real-time ARMS-qPCR method provides rapid, reliable, one-step quantitative detection of heteroplasmic mutant mtDNA.
Bai
Ren-Kui
RK
Institute for Molecular and Human Genetics, Georgetown University Medical Center, Washington, DC, USA.
Wong
Lee-Jun C
LJ
D004272:DNA, Mitochondrial / Q000235:genetics*; D004587:Electrophoresis, Agar Gel; D006801:Humans; D028361:Mitochondrial Diseases / Q000235:genetics; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D004272:DNA, Mitochondrial