Concordance evaluation between mitochondrial DNA sequence data and base composition data derived through electrospray ionization mass spectrometry

The University of North Texas Center for Human Identification (UNTCHI) is one of two major laboratories in the United States utilizing DNA for missing persons identification. Nuclear DNA and mitochondrial DNA (mtDNA) are analyzed to link unidentified remains to a reference family. Due to the high cost of sequencing mtDNA, a single maternal relative's DNA sample is sequenced and used as the mitochondrial reference sequence for an entire pedigree in the UNTCHI Missing Persons family reference database. Using a single sequence as the only reference for pedigree association assumes the conservation of the mitochondrial sequence throughout the pedigree. It is possible to generate results of similar utility to mtDNA sequencing using electrospray ionization time-of-flight mass spectrometry (ESI-MS). The ESI-MS method is considerably faster and can be performed at a much lower cost. Incorporating such a technology into the missing persons analysis could allow for multiple samples within a pedigree to be used as references. In order for this technology to be utilized in UNTCHI, a validation study evaluating the reliability of the results obtained using mass spectrometry must be performed. By comparing mtDNA profiles of maternal relatives within pedigrees using ESI-MS, we can evaluate the assumption that all maternal pedigree members share the same mtDNA profile. ESI-MS analysis of maternal relatives may demonstrate whether variation can be expected within a given pedigree when comparing mtDNA data. To validate using mass spectrometry analysis for identification purposes, the concordance between the results obtained using the ESI-MS technology and the standard sequencing technique was evaluated.;DNA samples from maternal relatives within family pedigrees that are stored in the missing persons family reference database were amplified for the mtDNA control region and evaluated on an Ibis T5000TM Biosensor System. The base composition obtained by mass spectrometry was compared to the reference sequence on file for each family and any differences observed were noted. Further analysis on intra-familial levels of variation and heteroplasmy were evaluated by direct sequence comparison if observed.