基于DNA甲基化标记的精液斑个体年龄推断研究

作为性犯罪案件中最常见的生物检材和最重要的关键证据，精液（斑）的个体年龄推断对犯罪调查具有重要意义。在已报道的众多年龄推断分子标记中，DNAm被认为是最理想的年龄推断指标。精子发生过程的高度复杂性，导致精子的DNAm模式与体细胞明显不同，具有高度特异性。与血液、唾液等生物检材相比，迄今有关精液的个体年龄推断研究极少，且存在标记数量少、推断精度低的问题，无法满足法医学“精准鉴定”的需求。由此，本课题拟采用新一代甲基化芯片在全基因组范围内对中国人精液AR-CpGs进行筛选，然后采用焦磷酸测序和甲基化SNaPshot两种检测技术对筛选的靶AR-CpGs甲基化水平的随龄变化规律进行系统研究并构建基于两种检测平台的年龄推断模型，以满足不同实验室的需求，最后进行全面的法医学应用评估。本项目旨在实现法医精液（斑）个体年龄的高精度推断，同时也为进一步研究DNAm在男性生殖细胞衰老过程中的调控机理奠定基础。

As the most common biological materials and the most important evidence in sexual crimes, age estimation of semen/seminal stains is of ultimate importance for criminal investigation. Among a series of biomarkers that have been reported so far, DNA methylation is considered to be the most promising biomarker for individual age estimation. Spermatogenesis is a highly complex process involving mitotic cell division, meiosis cell division and spermiogenesis, and this results in unique patterns of DNA methylation in spermatozoa, which is highly distinct from cells and tissues of somatic origin. Compared with biological materials such as blood and saliva, there are few studies on age estimation of semen so far. There are some problems for semen age estimation such as less markers and low prediction accuracy, which can not meet the needs of "Precision identification" in forensic medicine. Based on this, in this project, we will systematically screen age-related CpGs (AR-CpGs) in genome-wide from the semen DNA of Han Chinese individuals using a new generation of methylation array first. Then, to meet the needs of different laboratories, a systematic study on the age-related changes in DNA methylation levels of screened target AR-CpGs was performed using pyrosequencing and methylation SNaPshot assay, and two different age estimation models based on these two detection platforms will be constructed, respectively. Last, a comprehensive and systematic evaluation on application value in forensic practice will be carried out. The purpose of this project is to achieve a high-precision age estimation of semen/seminal stains, and to lay the foundation for the future study on the regulatory mechanism of DNA methylation in the aging process of male germ cells.