Single molecule PCR in mtDNA mutational analysis: Genuine mutations vs. damage bypass-derived artifacts

The area of somatic mtDNA mutation measurement is in a crisis because the methods used to quantify mtDNA mutations produce results varying by multiple orders of magnitude. The reason for these discrepancies is not clear, but given that most methods involve PCR, the prime suspect is PCR artifacts (e.g. spontaneous errors by the DNA polymerases used). In addition to simple misincorporation, another important source of artificial mutations is the conversion of chemically modified (e.g. damaged) nucleotides into mutations when bypassed by a thermostable DNA polymerase. These latter mutations are particularly difficult to account for because appropriate controls are not available. Here, we argue that single molecule PCR (smPCR) is uniquely positioned to account for these bypass-related artificial mutations and discuss the methodology involved in employing this technique.