Direct STR typing from human bones

Identification by STR analysis of bones is time-consuming, mainly due to the lengthy decalcification required and complex DNA extraction process. To streamline this process, we developed a direct STR typing protocol from bone samples. We optimized bone sample amounts using femur and tibia and two commercial PCR kits (IdentifilerTM Plus and IDplex Plus kits). Optimally, 100 mg of bone powder in 300 mu L PBS buffer was heated at 98 degrees C for three minutes to produce a supernatant for DNA amplification. IDplex Plus performed better than IdentifilerTM Plus in terms of allele recovery and peak height. Fifteen samples of each of seven bone elements (1st distal phalange of hand, capitate, femur, metacarpal 4, patella, talus, and tibia; N = 105) were then subjected to direct STR typing with the optimized protocol, and 94.3% were high partial to full profiles. The performance of the developed protocol was similar for all bone elements. Median peak heights were significantly better in profiles of cancellous bone than compact bone (p = 0.033) and significantly different across the bone elements (p < 0.001). Ten casework samples from various conditions and up to 7-year-PMI were subjected to both direct STR and conventional STR typing. No significant difference in the number of alleles was seen (95% HDI of -13.5 to 5.15). As well as being rapid, convenient, and safe, the protocol could help improve STR typing from bones. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

A direct STR typing protocol from bone samples was developed and optimized, showing high partial to full profiles for various bone elements. Performance was similar across bone elements, with higher peak heights in cancellous bone. The rapid, convenient, and safe protocol could improve efficiency of STR typing from bones.