Forensic Science Graduate Program and Department of Environmental Toxicology, University of California, Davis, CA, USA.
Proteomics Core Facility, University of California, Davis, CA, USA.
Forensic Sci Int Genet. 2019 Jul;41:19-23. doi: 10.1016/j.fsigen.2019.03.009. Epub 2019 Mar 11.
The microanatomy of human hair differs as a function of the site of origin on the body. This was a major consideration when anatomical features of hair were used as a means of comparison and human identification. Recent advances have demonstrated that proteomics of the hair shaft can be used to develop profiles of protein abundance and genetically variant peptides, the latter in turn being used to infer genotypes of SNP alleles. Because the profile of proteins would be expected to change as hair anatomy changes, it is an open question if the profile of genetically variant peptides will also change. While some sample to sample variation is expected, a potential drawback of using genetically variant peptides to infer an individual genotype is that the proteomic profile might change as a function of body site origin as well as an individual's genotype. The hypothesis in this study is that the profile of hair shaft genetically variant peptides depends more on an individual's genotype than on the site of hair shaft origin. To test this an analysis of both protein expression levels and genetically variant peptides was conducted on 4 body sites (scalp, axillary, beard and pubic hair) from 5 individuals with 4 biological replicates. Levels of protein expression were estimated using label-free quantification on resulting proteomic mass spectrometry datasets. The same datasets were then also analyzed for the presence of genetically variant peptides. This study demonstrates that the protein profiles of hair shafts varied as a function of somatic origin. By contrast the profile of genetically variant peptides, and resulting inferred genotype of SNP alleles, were more dependent on the individual. In this study random match probabilities ranged up to 1 in 196. Individual identification based on genetically variant peptides therefore can be obtained from human hair without regard to the site of origin. If the site of hair shaft origin was legally relevant then microscopic analysis is still necessary. This study demonstrates the utility of proteomic analysis for extracting forensic information from hair shaft evidence.
人体头发的微观解剖结构因起源部位的不同而有所差异。这在利用头发的解剖特征进行比较和人类身份识别时是一个主要考虑因素。最近的进展表明，可以利用头发轴的蛋白质组学来开发蛋白质丰度和遗传变异肽的图谱，后者反过来又被用来推断 SNP 等位基因的基因型。由于预计头发解剖结构的变化会导致蛋白质谱的变化，因此一个悬而未决的问题是遗传变异肽的图谱是否也会发生变化。虽然预计会有一些样本间的变异，但使用遗传变异肽来推断个体基因型的一个潜在缺点是，蛋白质组图谱可能会随着身体部位起源以及个体基因型的变化而变化。本研究的假设是，头发轴遗传变异肽的图谱更多地取决于个体的基因型，而不是头发轴起源的部位。为了验证这一假设，对来自 5 名个体的 4 个身体部位（头皮、腋窝、胡须和阴毛）的 4 个生物学重复样本进行了头发轴蛋白质表达水平和遗传变异肽的分析。使用无标记定量法对产生的蛋白质组质谱数据集进行了蛋白质表达水平的估计。然后，对相同的数据集进行了遗传变异肽的存在分析。本研究表明，头发轴的蛋白质谱随身体起源的不同而变化。相比之下，遗传变异肽的图谱以及由此推断的 SNP 等位基因的基因型，则更多地取决于个体。在本研究中，随机匹配概率高达 1 比 196。因此，无需考虑起源部位，就可以从头发中获得基于遗传变异肽的个体识别。如果头发轴起源部位在法律上是相关的，那么仍然需要进行微观分析。本研究证明了蛋白质组学分析在从头发轴证据中提取法医学信息方面的实用性。
