Direct STR amplification from whole blood and blood- or saliva-spotted FTA without DNA purification

The DNA purification step has been thought to be essential for typing of STR DNA. However, this process is time-consuming, and there is a risk of unexpected cross-contamination during purification. We report a new method for direct short tandem repeat (STR) amplification using a newly developed direct PCR buffer, AnyDirect, which can amplify STR loci from whole blood and blood- or saliva-spotted FTA cards without DNA purification. The autosomal and Y chromosomal STR loci were analyzed for whole blood and blood or saliva spots of random individuals, followed by comparison of the results with those of corresponding purified DNA. The results from whole blood and blood spots showed perfect concordance with those from purified DNA without allele or locus drop-out. However, in the case of saliva spots, no amplification or locus drop-out was observed in some of the samples, which offers a topic for further study. Additionally, some commercial hot-start DNA polymerases other than AmpliTaq Gold DNA polymerase were also found to be compatible with this buffer system. Therefore, this direct PCR buffer was demonstrated to be useful for fast forensic DNA analysis or criminal DNA databases for which there is no need to store DNA samples.     

Quantifiler observations of relevance to forensic casework

The Quantifiler (QF) kit is regularly used by forensic scientists for DNA quantitation. We performed in-house validation studies which revealed some interesting observations. The QF standard displayed a two-fold difference between two different lot numbers which suggests that every standard should be tested prior to use. The Promega K562 DNA standard works well with the QF kit. c. 41% of samples that inhibited the internal PCR control (IPC) system within the QF kit still produced good Profiler Plus reactions. QIAquick was effective at removing inhibitors. The presence of dyes within casework samples were observed not to inhibit QF amplifications. Template DNA greater than 100 ng/muL appeared to inhibit the IPC. Close to identical concentration results were obtained when alternative analysis settings were used. These validation findings will assist DNA processes involved in forensic casework.     

大鼠心肌组织中microRNA和18S rRNA的降解与死亡时间的相关性

目的探讨大鼠死后心肌组织中microRNA和18S rRNA的含量变化与死亡时间的关系。方法将SD大鼠断颈处死后置于25℃室温、50%湿度的环境中,于死后不同时间提取心肌组织中总RNA。利用实时荧光定量PCR检测大鼠心肌组织中miR-1-2和18S rRNA的含量变化,结果用循环阈值(Ct值)表示,分析死亡时间与Ct值的关系,最终建立死亡时间推断的回归分析方程。结果大鼠死后120h内心肌组织中miR-1-2含量无明显变化,此后开始下降;而18S rRNA含量在96 h内逐渐增多,随后开始缓慢下降。大鼠死后不同时间18S rRNA的Ct值以及18S rRNA和miR-1-2的ΔCt值与PMI呈非线性相关,二次曲线拟合的R2值分别为0.9487、0.8072。结论 18S rRNA的Ct值和18S rRNA与miR-1-2的ΔCt值与PMI之间存在明显非线性关系,可以作为早期死亡时间推断的指标。     

Bioinformatics and human identification in mass fatality incidents: the world trade center disaster

Victim identification initiatives undertaken in the wake of Mass Fatality Incidents (MFIs) where high-body fragmentation has been sustained are often dependent on DNA typing technologies to complete their mandate. The success of these endeavors is linked to the choice of DNA typing methods and the bioinformatic tools required to make the necessary associations. Several bioinformatic tools were developed to assist with the identification of the victims of the World Trade Center attacks, one of the most complex incidents to date. This report describes one of these tools, the Mass Disaster Kinship Analysis Program (MDKAP), a pair-wise comparison software designed to handle large numbers of complete or partial Short Tandem Repeats (STR) genotypes, and infer identity of, or biological relationships between tested samples. The software performs all functions required to take full advantage of the information content of processed genotypic data sets from large-scale MFIs, including the collapse of victims data sets, remains re-association, virtual genotype generation through gap-filling, parentage trio searching, and a consistency check of reported/inferred biological relationships within families. Although very few WTC victims were genetically related, the software can detect parentage trios from within a victim's genotype data set through a nontriangulated approach that screens all possible parentage trios. All software-inferred relationships from WTC data were confirmed by independent statistical analysis. With a 13 STR loci complement, a fortuitous parentage trio (FPT) involving nonrelated individuals was detected. Additional STR loci would be required to reduce the risk of an FPT going undetected in large-scale MFIs involving related individuals among the victims. Kinship analysis has proven successful in this incident but its continued success in larger scale MFIs is contingent on the use of a sufficient number of STR loci to reduce the risk of undetected FPTs, the use of mtDNA and Y-STRs to confirm parentage and of bioinformatics that can support large-scale comparative genotyping schemes capable of detecting parentage trios from within a group of related victims.     

PCR检测鸡毒霉形体和鸡滑液囊霉形体的研究

根据禽霉形体 16SrRNA的基因序列设计、合成了 1对引物 ,用这对引物对鸡毒霉形体 (Mycoplasmagallisep ticum ,MG)和鸡滑液囊霉形体 (Mycoplasmasynoviae ,MS)菌株DNA进行PCR扩增 ,得到了与预期大小相一致的约 5 80bp的PCR产物 ,而这对引物对其他禽病病原DNA或RNA模板的扩增结果为阴性。PCR方法对MG和MS的最小检出量分别为 2 pg和 3pg。应用已建立的PCR方法检测MG人工感染样品和临床样品 ,从人工感染样品中均检测到MG ,临床样品的MG阳性检出率为 10 .2 5 % ,高于常规分离培养的阳性检出率     

小鼠皮肤切创细胞因子的基因表达变化及其与损伤时间关系

目的 观察细胞因子在小鼠皮肤切创组织不同时间的基因表达变化及其与损伤时间的关系。方法用免疫组织化学染色法和RT-PCR法,检测小鼠皮肤切创组织中不同时间的白细胞介素-1α和-1β(IL-1α、-1βB),以及单核细胞趋化蛋白-1(MCP-1)、吞噬细胞炎性蛋白-1α和-2(MIP-1α、-2)的基因表达变化。结果 皮肤切创后在早期可诱导IL-1α和IL-1β的基因表达,6h达第一次高峰,24h下降,第3d再次出现高峰后,第6d下降至正常水平;而MCP-1、MIP-1α和MIP-2则在损伤后6h左右开始出现,3d达高峰,然后呈下降趋势。在这些被检因子中,以IL-1α、IL-1β、MIP-1α和MIP-2的变化幅度较大,而MCP-1的变化相对较小。结论 切创组织中IL-1α、-1β和MCP-1,以及MIP-1α、-2的基因表达随伤后不同时间呈现一定规律性变化;同时对同一组织多种细胞因子检查推测损伤时间完全可行。     

PCR-RFLP技术鉴定ABO基因型的法医学应用研究

目的 建立 PCR－ RFLP、非变性 PAG胶垂直电泳和银染技术进行 ABO基因分型的方法体系,并对 200名广东汉族人群 ABO基因型频率进行了调查。方法 用 Chelex－ 100和酚、氯仿抽提法处理样本, PCR扩增后用非变性聚丙烯酰胺凝胶垂直电泳和银染技术检测分型。结果 ABO位点特异性扩增片段长度为 175bp～ 210bp, 6种基因型频率分布为 0.025 0～ 0.430 0,杂合度 H值为 0.516 2,个体识别力 DP值为 0.711 1。结论 该方法可成功运用于血液、血痕、精斑、毛发、骨组织和混合斑等检材的个体识别及亲权鉴定的检验。