Yang Tingting, Gao Linlin, Zhang Jiarong, Xie Wei, Hu Wenjing, Yan Jiangwei
School of Forensic Medicine, Shanxi Medical University, Jinzhong, Shanxi, China.
Shanxi Key Laboratory of Forensic Medicine, Jinzhong, Shanxi, China.
Electrophoresis. 2024 Nov;45(21-22):2019-2027. doi: 10.1002/elps.202400056. Epub 2024 Oct 14.
Formalin fixatives are widely used in forensics to preserve tissues. However, extracting high-quality genomic DNA from formalin-fixed samples is challenging. Traditional short tandem repeat (STR) analysis using capillary electrophoresis (CE) for forensic DNA typing frequently results in failure. Massively parallel sequencing (MPS) can handle many samples and thousands of genetic markers, usually single-nucleotide polymorphisms (SNPs) and STRs, in a single test. Thus, it is useful for assessing highly deteriorated forensic evidence. Few studies have examined the effectiveness of STRs and SNPs genotyping of formalin-fixed skeletons using MPS. In this study, 55 skeletal samples from 5 individuals that were treated under different formalin fixation times (5-75 days) were examined and sequenced using the ForenSeq DNA Signature Prep Kit on the Illumina MiSeq FGX platform. The results showed that as the duration of formalin fixation increased, the detection rates of STRs and SNPs gradually decreased. After 75 days of fixation, the average detection rates for STRs and SNPs were 4% and 10%, respectively. The cumulative discrimination power (CDP) of individual identification SNPs (iiSNPs) was >0.9999 on the 45th day. However, the CDP of STRs was 0.9930 on the 22nd day. Low detection rates were observed for six STRs (D1S1656, PentaE, D22S1045, PentaD, DX8378 and DX10103) and five SNPs (rs2920816, rs354439, rs1736442, rs338882 and rs1031825). In conclusion, DNA extracted from formalin-fixed skeletons decomposes rapidly over time, and MPS technology can be a useful tool for detecting forensic genetic markers in such samples.
福尔马林固定剂在法医学中被广泛用于保存组织。然而，从福尔马林固定的样本中提取高质量的基因组DNA具有挑战性。传统的使用毛细管电泳（CE）进行法医DNA分型的短串联重复序列（STR）分析经常失败。大规模平行测序（MPS）可以在一次测试中处理许多样本和数千个遗传标记，通常是单核苷酸多态性（SNP）和STR。因此，它对于评估高度降解的法医证据很有用。很少有研究使用MPS检查福尔马林固定骨骼的STR和SNP基因分型的有效性。在本研究中，对来自5个个体的55个骨骼样本进行了检查，这些样本在不同的福尔马林固定时间（5 - 75天）下处理，并使用Illumina MiSeq FGX平台上的ForenSeq DNA Signature Prep试剂盒进行测序。结果表明，随着福尔马林固定时间的增加，STR和SNP的检测率逐渐降低。固定75天后，STR和SNP的平均检测率分别为4%和10%。个体识别SNP（iiSNP）的累积鉴别力（CDP）在第45天时>0.9999。然而，STR的CDP在第22天时为0.9930。观察到六个STR（D1S1656、PentaE、D22S1045、PentaD、DX8378和DX10103）和五个SNP（rs2920816、rs354439、rs1736442、rs338882和rs1031825）的检测率较低。总之，从福尔马林固定的骨骼中提取的DNA会随着时间迅速分解，而MPS技术可以成为检测此类样本中法医遗传标记的有用工具。
