Comparing different post-mortem human samples as DNA sources for downstream genotyping and identification

Area of Science:

• Forensic Science
• Molecular Biology
• Genetics

Background:

• DNA profiling from decomposing remains is difficult in tropical climates like the Philippines.
• High humidity and temperatures accelerate decomposition, complicating identification of disaster victims or crime scene remains.
• Traditional reliance on femur samples is hindered by sample collection challenges during mass casualty events.

Purpose of the Study:

• To assess the efficacy of various biological samples for DNA extraction and genotyping in challenging post-mortem conditions.
• To identify alternative samples to femur for DNA analysis in the Philippines.
• To evaluate DNA yield and the presence of PCR inhibitors in different tissue types.

Main Methods:

• DNA was extracted from multiple sample types (body fluid, bone marrow, muscle, clavicle, femur, metatarsal, patella, rib, vertebra) from cadavers and exhumed remains.
• A detergent-washing followed by an organic DNA extraction method was employed.
• Autosomal Short Tandem Repeat (STR) and Y-STR DNA typing were performed using PowerPlex® systems and analyzed on an AB3500 Genetic Analyzer.

Main Results:

• Amplifiable DNA was successfully obtained from most analyzed samples, including non-bone and bone samples.
• Complete DNA profiles were generated from bone marrow, femur, metatarsal, and patella using 0.1 ng DNA template.
• PCR inhibitors were detected in bone marrow, muscle, rib, and vertebra samples, but did not prevent successful genotyping in most cases.

Conclusions:

• Bone marrow and teeth (represented by metatarsal and patella) are viable alternatives for DNA profiling in the Philippines.
• The evaluated DNA extraction method is effective for various sample types, even with PCR inhibitors present.
• Successful DNA typing from diverse post-mortem samples aids human identification efforts in resource-limited settings.