藻类rDNA特异性片段长度多态性在溺死鉴定中的应用

Application of Specific Fragment Length Polymorphism of Algae rDNA in Identification of Drowning Cases

目的通过检验水体和人体器官中硅藻核糖体DNA(rDNA) 5.8S部分序列、第二内转录间隔区(second internal transcribed spacer,ITS2)序列(5.8S+ITS2)的长度多态性差异,判断溺水死亡案件中受害人的落水地点以及受害人系生前落水还是死后被抛尸入水。方法以南京市公安局法医中心受理的2例硅藻检验鉴定案例为对象,利用5.8S+ITS2分子标记的长度多态性,分析藻类生物在水体、人体组织中种群结构的差异。结果案例1中,在受害人肺、肝组织和水体样本中均检出种类相近的硅藻,利用5.8S+ITS2分子标记在死者肺组织和水体样本中均检出330 bp和376 bp两种DNA片段,确定受害人系生前溺水。案例2中,在死者肺、肝组织中均未检出硅藻,利用5.8S+ITS2分子标记在死者肺组织中仅获得1条DNA片段,长度为331 bp,相对荧光单位值非常低,确定受害人系死后抛尸入水。结论本方法检验两案例的实验结果符合实际案情和硅藻镜检的结论,利用5.8S+ITS2分子标记研究水体和人体组织中特定微生物的种群结构差异,从而判断溺水死亡的落水地点以及受害人系生前落水还是死后被抛尸入水等问题具有可行性。

Objective To identify the drop-off location of victims in drowning cases,and confirm whether it is a fatal drowning or the victim is thrown into the water after death by detecting part of 5.8S sequence and second internal transcribed spacer(ITS2)(5.8S+ITS2)of diatom rDNA in water and organs.Methods Two cases identified by diatom examination,which received by Nanjing Municipal Public Security Bureau Forensic Center,were taken as the research objects.The difference of the population structure of algae in water and human tissue was analysed by length polymorphism of 5.8S+ITS2 marker.Results In case 1,similar species of diatom were detected from victim’s lung and liver tissues and the water sample.Two kinds of DNA fragments with length of 330 bp and 376 bp were detected from victim’s lung tissue and the water sample using 5.8S+ITS2 marker,which could confirm the victim was drowning before death.In case 2,there was no diatom found in victim’s lung and liver tissues.Only one kind of DNA fragment with length of 331 bp and low relative fluorescence unit(RFU)was obtained from victim’s lung tissue using 5.8S+ITS2 marker,thus the victim was thrown into the water after death.Conclusion The experimental results of the two cases in present study are consistent with the actual facts and the result of the diatom microscopic examination.The difference of population structure of specific microorganism in water and human tissue can be detected by 5.8S+ITS2 marker,which can help to identify the drop-off location of victims in drowning cases,and confirm whether it is a fatal drowning or the victim is thrown into the water after death.