Silva Deborah S B S, Antunes Joana, Balamurugan Kuppareddi, Duncan George, Alho Clarice S, McCord Bruce
Department of Chemistry and Biochemistry, Florida International University, Miami, FL, USA; Faculty of Biosciences, Laboratory of Human and Molecular Genetics, PUCRS, Porto Alegre, Brazil.
Department of Chemistry and Biochemistry, Florida International University, Miami, FL, USA.
Forensic Sci Int Genet. 2016 Jul;23:55-63. doi: 10.1016/j.fsigen.2016.01.017. Epub 2016 Feb 1.
Determining the type and origin of body fluids in a forensic investigation can provide important assistance in reconstructing crime scenes. A set of epigenetic markers, ZC3H12D, BCAS4 and cg06379435, have been developed to produce unique and specific patterns of DNA methylation that can be used to identify semen, saliva, and blood, respectively. To ensure the efficacy of these markers, developmental validation studies were performed to determine the conditions and limitations of this new tool for forensic analysis. DNA was extracted from human samples and bisulfite modified using commercial bisulfite modification kits. Specific primers were used to amplify the region of interest and the methylation profile of the CpG sites were determined by pyrosequencing. The percent methylation values at each CpG site were determined in multiple samples and averaged for each tissue type. The versatility of these new markers is presented by showing the results of validation studies on sensitivity, human specificity, stability and mixture resolution. When testing the markers using different organisms, we did obtain positive results for certain non-human primate samples, however, all other tested species were negative. The lowest concentration consistently detected varied from 0.1 to 10ng, depending on the locus, indicating the importance of primer design and sequence in the assay. The method also proved to be effective when inhibitors were present in the samples or when samples were degraded by heat. Simulated case- samples were also tested. In the case of mixtures of different cell types, the overall methylation values varied in a consistent and predictable manner when multiple cell types were present in the same sample. Overall, the validation studies demonstrate the robustness and effectiveness of this new tool for body fluid identification.
在法医调查中确定体液的类型和来源可为重建犯罪现场提供重要帮助。已开发出一组表观遗传标记物,即ZC3H12D、BCAS4和cg06379435,以产生独特且特异的DNA甲基化模式,分别用于识别精液、唾液和血液。为确保这些标记物的有效性,进行了发育验证研究,以确定这种用于法医分析的新工具的条件和局限性。从人类样本中提取DNA,并使用商业亚硫酸氢盐修饰试剂盒进行亚硫酸氢盐修饰。使用特异性引物扩增感兴趣区域,并通过焦磷酸测序确定CpG位点的甲基化谱。在多个样本中确定每个CpG位点的甲基化百分比值,并对每种组织类型求平均值。通过展示关于敏感性、人类特异性、稳定性和混合物分辨率的验证研究结果,呈现了这些新标记物的多功能性。在使用不同生物体测试这些标记物时,我们确实在某些非人类灵长类动物样本中获得了阳性结果,然而,所有其他测试物种均为阴性。始终能检测到的最低浓度因位点而异,范围为0.1至10纳克,这表明引物设计和序列在该检测中的重要性。当样本中存在抑制剂或样本因加热而降解时,该方法也被证明是有效的。还对模拟案例样本进行了测试。在不同细胞类型混合物的情况下,当同一样本中存在多种细胞类型时,总体甲基化值以一致且可预测的方式变化。总体而言,验证研究证明了这种用于体液识别的新工具的稳健性和有效性。