Epigenetic estimation of age in humpback whales - data held at Dryad

This is a local copy of a metadata record and dataset stored at Dryad. This local copy is maintained in order to provide a link to the originating Australian Antarctic program project. See the link to the Dryad site at the provided URL for full details on this data set.

Age is a fundamental aspect of animal ecology, but is difficult to determine in many species. Humpback whales exemplify this as they have a lifespan comparable to humans, mature sexually as early as four years and have no reliable visual age indicators after their first year. Current methods for estimating humpback age cannot be applied to all individuals and populations. Assays for human age have recently been developed recently based on age-induced changes in DNA methylation of specific genes. We used information on age-associated DNA methylation in human and mouse genes to identify homologous gene regions in humpbacks. Humpback skin samples were obtained from individuals with a known year of birth and employed to calibrate relationships between cytosine methylation and age. Seven of 37 cytosines assayed for methylation level in humpback skin had significant age-related profiles. The three most age-informative cytosine markers were selected for a humpback epigenetic age assay. The assay has an R2 of 0.787 (p = 3.04e-16) and predicts age from skin samples with a standard deviation of 2.991 years. The epigenetic method correctly determined which of parent-offspring pairs is the parent in more than 93% of cases. To demonstrate the potential of this technique, we constructed the first modern age profile of humpback whales off eastern Australia and compared the results to population structure five decades earlier. This is the first epigenetic age estimation method for a wild animal species and the approach we took for developing it can be applied to many other non model organisms.

本文件为存储于Dryad（Dryad）学术数据仓储的元数据记录与数据集的本地副本。维护该本地副本旨在关联至其原始来源——澳大利亚南极计划项目。如需获取该数据集的完整细节，请访问提供URL中指向Dryad平台的链接。

年龄是动物生态学的核心研究维度之一，但诸多物种的年龄难以精准测定。座头鲸便是典型例证：其寿命与人类相当，最早4年便可性成熟，且一岁之后便无可靠的视觉年龄标识。当前用于估算座头鲸年龄的方法无法覆盖所有个体与种群。

近期已有研究基于特定基因的DNA甲基化随年龄的变化模式，开发出了人类年龄检测方法。我们借助人类与小鼠基因中与年龄相关的DNA甲基化信息，在座头鲸体内鉴定出了同源基因区域。我们采集了已知出生年份的座头鲸皮肤样本，并以此校准胞嘧啶（cytosine）甲基化水平与年龄之间的关联关系。在针对座头鲸皮肤样本甲基化水平开展检测的37个胞嘧啶位点中，有7个位点呈现出显著的年龄相关特征。研究选取了3个年龄信息价值最高的胞嘧啶标记物，构建了座头鲸表观遗传年龄检测方法。该检测方法的决定系数R²为0.787（p=3.04×10^-16），基于皮肤样本预测年龄的标准偏差为2.991年。该表观遗传方法可在超过93%的案例中正确识别亲子对中的亲本个体。

为验证该技术的应用潜力，我们构建了澳大利亚东部海域座头鲸的首个现代年龄结构图谱，并将结果与50年前的种群结构进行了对比分析。本研究首次实现了野生动物物种的表观遗传年龄估算，且所开发的方法可推广应用于诸多非模式生物。