DNA methylation data facilitate the development of accurate molecular estimators of chronological age or “epigenetic clocks.” We present a robust epigenetic clock for the beluga whale, Delphinapterus leucas, developed for an endangered population in Cook Inlet, Alaska, USA. We used a custom methylation array to measure methylation levels at 37,491 cytosine–guanine sites (CpGs) from skin samples of dead whales (n = 67) whose chronological ages were estimated based on tooth growth layer groups. Using these calibration data, a penalized regression model selected 23 CpGs, providing an R² = 0.92 for the training data; and an R² = 0.74 and median absolute age error = 2.9 years for the leave one out cross‐validation. We applied the epigenetic clock to an independent dataset of 38 skin samples collected with a biopsy dart from living whales between 2016 and 2018. Age estimates ranged from 11 to 27 years. We also report sex correlations in CpG data and describe an approach of identifying the sex of an animal using DNA methylation. The epigenetic estimators of age and sex presented here have broad applications for conservation and management of Cook Inlet beluga whales and potentially other cetaceans.

中文翻译：

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用于估计现存白鲸年龄的表观遗传时钟


DNA 甲基化数据有助于开发准确的实际年龄分子估计器或“表观遗传时钟”。我们为白鲸（ Delphinapterus leucas ）提供了一个强大的表观遗传时钟，该时钟是为美国阿拉斯加州库克湾的濒危种群开发的。我们使用定制的甲基化阵列来测量死鲸 ( n = 67) 皮肤样本中 37,491 个胞嘧啶-鸟嘌呤位点 (CpG) 的甲基化水平，这些死鲸的实际年龄是根据牙齿生长层组估计的。使用这些校准数据，惩罚回归模型选择了 23 个 CpG，为训练数据提供R ² = 0.92；留一交叉验证的R ² = 0.74，中位绝对年龄误差 = 2.9 岁。我们将表观遗传时钟应用于 2016 年至 2018 年间通过活检飞镖从活鲸身上收集的 38 个皮肤样本的独立数据集。年龄估计范围为 11 至 27 岁。我们还报告了 CpG 数据中的性别相关性，并描述了一种利用 DNA 甲基化识别动物性别的方法。这里提出的年龄和性别的表观遗传估计对于库克湾白鲸和潜在的其他鲸类动物的保护和管理具有广泛的应用。