Evaluation of reliability of STR typing in human colon carcinomas tissues used for identification purpose

The short tandem repeats (STRs) have become an important and widely used tool in forensic casework. Clinical tissue samples are not usually employed in forensic casework, but sometimes, malignant tissue samples may be the only source of biological material for forensic investigations. However, in use of such samples, uncertainties due to microsatellite instability (MSI) and loss of heterozygosity (LOH) may be encountered. In our study of 77 human colon carcinomas tissue with the AmpFlSTR Identifiler Kit comprising 15 STR loci and the amelogenin gene, we detected four kinds of changes between normal tissue and tumor tissue including pLOH, LOH, occurrence of an additional allele (Add) and occurrence of a new allele (New) instead of that found in normal tissue. The overall variation detectable rate was 11.28%, of which pLOH was 79.1%, LOH was 7.9%, Add was 7.9% and New was 5%. Of the above four changes, the incidence rate of pLOH, LOH, Add and New was respectively 8.93%, 0.89%, 0.89% and 0.57%. The STRs mostly affected were D18S51, D5S818, FGA and D19S433. Only pLOH was found at five loci including vWA, TPOX, TH01, D13S317 and amelogenin gene. Our results demonstrate that great care should be taken in the evaluation of typing results obtained from clinical tissue specimens, in particular when no reference samples are available, because genetic instability is a very common event observed in different tumors and the STRs used for individual identification could sometimes be affected.     

联苯胺预试验处理血痕后样本DNA定量的研究

目的探讨联苯胺血痕预试验处理后样本DNA含量的变化及对STR分型检测的影响。方法选取10名无关个体EDTA抗凝血液制成滤纸血痕,保存干燥时间分0．5h、1h、3h、6h、12h、24h六个实验组,并采用磁珠提取法、QIAcubeDNA提取纯化法、chelex-100提取法提取样本DNA,应用RT-PCR定量技术检测样本DNA含量,同时应用PCR-STR技术和Idfiler-plus试剂盒检测相应样本STR分型。结果联苯胺血痕预试验后处理样本,随保存时间的延长,其样本DNA含量显示逐渐降低的趋势。回归线性对数分析显示,磁珠提取法：Y=-0．40871n（x）＋0．7044R0—0．7633;QIAcubeDNA提取纯化法：Y=-0．23931n（x）＋0．4764R0—0．8715;chelex-100提取法：Y=-0．11781n（x）＋0．2302R2=0．9571。不同DNA提取方法对同一保存时间的联苯胺血痕预试验试剂处理样本DNA含量间差异有极显著性,P〈O．01。结论联苯胺血痕预试验后对后续STR分型影响较大,联苯胺血痕预实验后的血痕不能继续进行STR分型检测。     

DNA甲基化在组织/体液来源鉴定中的研究进展

对可疑生物样本的组织/体液进行来源鉴别是重建犯罪现场、推断犯罪性质等侦查活动中极为重要的一环。对表观遗传学理论的研究证明运用基因组中存在的组织特异性DNA甲基化差异位点(t DMRs)可以对组织/体液进行来源鉴别。本文旨在通过对近年来DNA甲基化在法医学领域用于鉴定人体组织/体液来源方面的研究成果进行阐述,试图用所得到的信息来分析DNA甲基化作为一种组织/体液鉴定遗传学标记的可能性、优劣点及其应用价值和发展前景,以期能为法医工作者的相关研究及实践提供参考。