Age estimation based on blood DNA methylation levels in brown bears

Age is an essential trait for understanding the ecology and management of wildlife. A conventional method of estimating age in wild animals is counting annuli formed in the cementum of teeth. This method has been used in bears despite some disadvantages, such as high invasiveness and the requirement for experienced observers. In this study, we established a novel age estimation method based on DNA methylation levels using blood collected from 49 brown bears of known ages living in both captivity and the wild. We performed bisulfite pyrosequencing and obtained methylation levels at 39 cytosine-phosphate-guanine (CpG) sites adjacent to 12 genes. The methylation levels of CpGs adjacent to four genes showed a significant correlation with age. The best model was based on DNA methylation levels at just four CpG sites adjacent to a single gene, SLC12A5, and it had high accuracy with a mean absolute error of 1.3 years and median absolute error of 1.0 year after leave-one-out cross-validation. T..., ,年龄是解析野生动物生态学特征与种群管理的关键性状。传统的野生动物年龄估算方法为计数牙齿牙骨质（cementum）上形成的生长环。尽管该方法存在侵入性强、依赖专业观测人员等缺陷，但仍被应用于熊类的年龄估算。本研究以采集自49只已知年龄的圈养与野生棕熊的血液样本为材料，建立了一种基于DNA甲基化水平的新型年龄估算方法。本研究采用亚硫酸氢盐焦磷酸测序（bisulfite pyrosequencing）技术，获取了12个基因旁侧的39个胞嘧啶-磷酸-鸟嘌呤（CpG）位点的甲基化水平。其中4个基因旁侧的CpG位点甲基化水平与年龄呈显著相关。最优模型仅依托单个基因SLC12A5旁侧的4个CpG位点的甲基化水平构建，经留一法交叉验证（leave-one-out cross-validation）后，该模型展现出较高的估算精度，平均绝对误差为1.3年，中位数绝对误差为1.0年。T...,