Investigation on STR profiling of maternal DNA from a degraded placenta with an abandoned newborn male baby.

The placenta is a unique and complex organ composed of a mixture of fetal and maternal tissues. In this study, we aimed to detect maternal short tandem repeats (STRs) in degraded placenta from a newborn male baby found abandoned in a river. In order to deduce maternal alleles-which was not possible by sampling of different parts of the placenta-we collected samples from the maternal blood pool in the intervillous space and applied a multi-step method (named tempo-gap DNA extraction) for extracting DNA at defined time points after cell lysis (10 min, 2 h 10 min, and 4 h 10 min). The first lysis step (10 min) effectively removed severely degraded DNA; this was followed by a second lysis step (2 h 10 min) for high recovery of both fetal and maternal DNA. The third lysis step (4 h 10 min) effectively eliminated unwanted residual fetal DNA. The differential lysis of fetal and maternal cells occurred not because fetal and maternal cells exhibited different lysis behavior, but because of the difference in their numbers. Although all of the lysates showed fetal cell contamination, we were able to derive a maternal STR profile from the good-quality mixed STR profile from the second lysate of placental piece B. This study provides technical insight into concurrent issues encountered during routine forensic analysis of DNA samples, such as degradation, cell contamination (mixed DNA), and low-template DNA.