Resolving mtDNA mixtures by denaturing high-performance liquid chromatography and linkage phase determination.

Mitochondrial DNA (mtDNA) sequencing can provide crucial information to forensic investigators when the quantity and quality of DNA would otherwise be limiting. The difficulty of analyzing mtDNA mixtures, however, has been a significant obstacle to its broader use in forensics. Denaturing high-performance liquid chromatography (DHPLC) in combination with direct sequencing makes it possible to determine the linkage phase of individual amplicons in a mixture. The reliability of the approach is based, in part, on the strong correlation between a change in the relative quantities of different DNA amplicons in a given mixture versus a change in the relative electrophoretic peak heights at mixed base positions. Using standard operating procedures previously validated for use in forensic laboratories, this approach enables sequence-specific fractionation of natural (heteroplasmic) or situational (multi-contributor) DNA mixtures prior to direct sequencing. As a novel approach for the rapid and accurate analysis of DNA mixtures, DHPLC may aid criminal investigators by making it possible to obtain definitive mitochondrial DNA results from otherwise challenging samples.