This study compared STR, mtGenome, and nuclear SNP data generated using an ancient and forensic DNA extraction protocols sampled from fire-death victims.
The recovery and analysis of DNA from burned human remains represent some of the most challenging cases in forensic and bioarchaeological research. Low DNA yields are notoriously problematic in the most severe burned cases, resulting in STR dropout, low mtGenome and nuclear SNP coverage. Over a period of 2 years, the current study obtained and documented 62 samples from 27 fire-death and cremation cases in collaboration with the Maricopa County Office of the Medical Examiner (Phoenix, Arizona). Samples were chosen with the intent of obtaining different skeletal elements showing different levels of burning (burn categories I-V). STR profiles were generated using the PowerPlex® ESX 17 Fast Systems STR kit by Promega. In addition, DNA extracts were converted into double-stranded DNA libraries and enriched for mitochondrial DNA and nuclear SNPs for next-generation sequencing. The data show that STR profile quality, mtGenome, and SNP coverage significantly decreased at temperatures >550°C across both extraction procedures; however, partial STR profiles and low coverage mtGenomes were recovered using the ancient DNA extraction protocol, suggesting the retention of ultrashort DNA molecules at temperatures exceeding 550°C. These data confirm the difficulties in obtaining DNA from burnt skeletal material using conventional and next-generation sequencing technologies. Overall, these analyses suggest that ancient DNA methods offer an alternative to forensic techniques, especially under circumstances where traditional forensic applications have failed. (publisher abstract modified)