Abstract：
Age prediction is an important aspect of forensic science that offers valuable insight into identification. In recent years, extensive studies have been conducted on age prediction based on DNA methylation, and numerous studies have demonstrated that DNA methylation is a reliable biomarker for age prediction. However, almost all studies on age prediction based on DNA methylation have focused on age-related CpG sites in autosomes, which are concentrated on single-source DNA samples. Mixed samples, especially male-female mixed samples, are common in forensic casework. The application of Y-STRs and Y-SNPs can provide clues for the genetic typing of male individuals in male-female mixtures, but they cannot provide the age information of male individuals. Studies on Y-chromosome DNA methylation can address this issue. In this study, we identified five age-related CpG sites on the Y chromosome (Y-CpGs) and developed a male-specific age prediction model using pyrosequencing combined with a support vector machine algorithm. The mean absolute deviation of the model was 5.50 years in the training set and 6.74 years in the testing set. When we used a male blood sample to predict age, the deviation between the predicted and chronological age was 1.18 years. Then, we mixed the genomic DNA of the male and a female at ratios of 1:1, 1:5, 1:10, and 1:50, the range of deviation between the predicted and chronological age of the male in the mixture was 1.16-1.74 years. In addition, there was no significant difference between the methylation values of bloodstains and blood in the same sample, which indicates that our model is also suitable for bloodstain samples. Overall, our results show that age prediction using DNA methylation of the Y chromosome has potential applications in forensic science and can be of great help in predicting the age of males in male-female mixtures. Furthermore, this work lays the foundation for future research on age-related applications of Y-CpGs.
摘要：
年龄预测是法医学的一个重要方面，可以为识别提供有价值的见解。近年来,已经对基于DNA甲基化的年龄预测进行了广泛的研究，大量研究表明，DNA甲基化是预测年龄的可靠生物标志物。然而,几乎所有基于DNA甲基化的年龄预测研究都集中在常染色体中与年龄相关的CpG位点，集中在单一来源的DNA样本上。混合样品,尤其是男女混合样本，在法医案件中很常见。Y-STRs和Y-SNPs的应用可以为男性个体在男女混合物中的遗传分型提供线索。但是他们不能提供男性的年龄信息。对Y染色体DNA甲基化的研究可以解决这个问题。在这项研究中,我们在Y染色体上确定了5个与年龄相关的CpG位点(Y-CpGs),并使用焦磷酸测序结合支持向量机算法建立了男性特定年龄预测模型.模型的平均绝对偏差在训练集中为5.50年，在测试集中为6.74年。当我们用男性血液样本来预测年龄时，预测年龄和实际年龄之间的偏差为1.18岁。然后，我们以1:1、1:5、1:10和1:50的比例混合男性和女性的基因组DNA，混合物中男性的预测年龄和实际年龄之间的偏差范围为1.16-1.74岁。此外,在同一样本中，血迹和血液的甲基化值没有显着差异，这表明我们的模型也适用于血迹样本。总的来说,我们的研究结果表明,利用Y染色体DNA甲基化进行年龄预测在法医学中具有潜在的应用价值,对预测男女混合中男性的年龄有很大帮助.此外，这项工作为今后研究Y-CpG与年龄相关的应用奠定了基础。
