Characterization of Holstein and Normande whole milk miRNomes highlights breed specificities. Characterization of Holstein and Normande whole milk miRNomes highlights breed specificities

The concept of milk as a healthy food has opened the way for studies on milk components, from nutrients to microRNAs, molecules with broad regulatory properties present in large quantities in milk. Characterization of these components has been performed in several species, such as humans and bovine, depending on the stages of lactation. Here, we have studied the variation in milk microRNA composition according to genetic background. Using high throughput sequencing, we have characterized and compared the milk miRNomes of Holstein and Normande cattle, dairy breeds with distinct milk production features, in order to highlight microRNAs that are essential for regulation of the lactation process. In Holstein and Normande milk, 2,038 and 2,030 microRNAs were identified, respectively, with 1,771 common microRNAs, of which 1,049 were annotated and 722 were predicted. The comparison of the milk miRNomes of two breeds allowed to highlight 182 microRNAs displaying significant differences in the abundance. They are involved in the regulation of lipid metabolism and mammary morphogenesis and development, which affects lactation. Our results provide new insights into the regulation of molecular mechanisms involved in milk production. Overall design: microRNA profiles of whole milk from 17 primiparous cows (Holstein: four 2-years old and five 3-years old; Normande: three 2-years old and five 3-years old), at 2-months of lactation, generated by deep sequencing, using Illumina HiSeq 4000.

牛奶作为健康食品的理念推动了针对牛奶组分的研究，涵盖从营养物质到微RNA（microRNA）的各类成分——这类分子在牛奶中大量存在，且具备广泛的调控功能。目前已有多项研究针对人类、牛等多个物种的牛奶组分进行了表征分析，且相关研究均考虑了泌乳阶段的影响。本研究聚焦于不同遗传背景下牛奶微RNA组成的差异。我们借助高通量测序技术，对具有迥异泌乳生产特性的两个奶牛品种——荷斯坦（Holstein）与诺曼德（Normande）的牛奶微RNA组（miRNome）进行了表征与比较，旨在筛选出泌乳过程调控所必需的微RNA。在荷斯坦与诺曼德奶牛的牛奶中，我们分别鉴定出2038和2030种微RNA，其中共有微RNA为1771种，包含已注释微RNA 1049种、预测微RNA 722种。对两个品种的牛奶微RNA组进行比较后，我们筛选出182种丰度存在显著差异的微RNA。这些微RNA参与调控脂代谢以及乳腺形态发生与发育过程，进而影响泌乳功能。本研究结果为解析牛奶生产相关分子调控机制提供了新的视角。实验整体设计：采集17头初产奶牛（荷斯坦组：4头2岁龄、5头3岁龄；诺曼德组：3头2岁龄、5头3岁龄）泌乳2个月时的全脂牛奶样本，通过Illumina HiSeq 4000平台进行深度测序，以获取微RNA表达谱。