Graduate School, People's Public Security University of China, No.1 Muxidi Nanli, Beijing 100038, China; National Engineering Laboratory for Forensic Science, Key Laboratory of Forensic Genetics of Ministry of Public Security, Institute of Forensic Science, Ministry of Public Security, No.17 Muxidi Nanli, Beijing 100038, China.
CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Science, National Chromatographic Research and Analysis Center, 457 Zhongshan Road, Dalian 116023, China.
Forensic Sci Int Genet. 2022 Sep;60:102742. doi: 10.1016/j.fsigen.2022.102742. Epub 2022 Jun 18.
Hair shaft is one of the most common biological evidence found at crime scenes. However, due to the biogenic degradation of nuclear DNA in hair shaft, it is difficult to achieve individual identification through routine DNA analysis. In contrast, the proteins in hair shaft are stable and contain genetic polymorphisms in the form of single amino acid polymorphisms (SAPs), translated from non-synonymous single nucleotide polymorphisms (nsSNPs) in the genome. However, the number of SAPs detected still cannot meet the requirements of practical applications. This paper developed a deep coverage proteome analysis method by combining a three-step sequential ionic liquid-based protein extraction and 2D-RPLC-MS/MS with high and low pH to identify both variant and reference SAPs from 2-cm-long hair shafts. We identified 632 ± 243 protein groups from 10 individuals, with the average number of SAPs reaching 167 ± 21/person. These were further used to calculate random match probabilities (RMPs), a widely accepted forensic statistical term for human identification. The RMPs ranged from 6.53 × 10 to 3.10 × 10 (median = 2.62 × 10) when calculated with frequency of matching nsSNP genotype data from exomes, and ranged from 2.62 × 10 to 2.07 × 10 (median = 4.88 × 10) with SAP genotype frequency. All these results indicate that the deep coverage proteomics method is beneficial for improving SAP-based forensic individual identification in hair shaft, with great potential in crime investigation.
毛发是犯罪现场最常见的生物证据之一。然而，由于毛发核 DNA 的生物降解，通过常规 DNA 分析很难实现个体识别。相比之下，毛发中的蛋白质稳定，并且以单氨基酸多态性（SAP）的形式包含遗传多态性，这些 SAP 是由基因组中的非同义单核苷酸多态性（nsSNP）翻译而来。然而，检测到的 SAP 数量仍然不能满足实际应用的要求。本文通过结合三步顺序离子液体蛋白提取法和 2D-RPLC-MS/MS 与高低 pH 值，开发了一种深度覆盖的蛋白质组分析方法，从 2cm 长的毛发中鉴定出变异型和参考型 SAPs。我们从 10 个人中鉴定出 632 ± 243 个蛋白质组，平均 SAPs 数量达到 167 ± 21/人。这些 SAPs 进一步用于计算随机匹配概率（RMP），这是一个广泛接受的用于人类识别的法医统计术语。当使用外显子中匹配 nsSNP 基因型数据的频率计算时，RMP 范围从 6.53×10 到 3.10×10（中位数= 2.62×10），当使用 SAP 基因型频率计算时，RMP 范围从 2.62×10 到 2.07×10（中位数= 4.88×10）。所有这些结果表明，深度覆盖蛋白质组学方法有利于提高基于 SAP 的毛发个体识别的法医应用，在犯罪调查中有很大的潜力。
