Micro ribonucleic acid (miRNA) is a type of noncoding RNA, and it has been revealed to play important roles in the activity of the mammary gland (MG) in some species. However, the function of miRNAs in MG of sheep is poorly understood. In the study, Gansu Alpine Merino (GAM; n = 9) and Small-tailed Han sheep (STH; n = 9) with different milk production traits were investigated. Microstructures and the expression profile of miRNAs of MG tissues at peak lactation were studied. Mature alveolar lumens of MG in appearance were larger in STH than GAM. The expression levels of CSN2 and the content of rough endoplasmic reticulum were also higher in STH ewes than GAM ewes. A total of 124 mature miRNAs were expressed, and 18 of these were differentially expressed between the 2 breeds. The KEGG analysis results showed that the targeted genes of differentially expressed miRNAs were mainly involved in some metabolic pathways and signaling pathways related to MG development, milk protein, and fat synthesis. The findings in the study can improve our understanding of the roles of miRNAs in the development and lactation of MG in sheep.

微核糖核酸 (miRNA) 是一种非编码 RNA，已被揭示在某些物种的乳腺 (MG) 活动中起重要作用。然而，对绵羊MG中miRNA的功能知之甚少。本研究对具有不同产奶性状的甘肃高山美利奴羊（GAM；n=9）和小尾寒羊（STH；n=9）进行了调查。研究了泌乳高峰期MG组织的微结构和miRNA的表达谱。MG的成熟肺泡管腔在STH比GAM大。STH母羊的CSN2表达水平和粗面内质网含量也高于GAM母羊。共表达了 124 个成熟的 miRNA，其中 18 个在 2 个品种之间差异表达。KEGG分析结果表明，差异表达miRNA的靶向基因主要参与与MG发育、乳蛋白、脂肪合成相关的一些代谢途径和信号通路。该研究的发现可以提高我们对 miRNA 在绵羊 MG 发育和泌乳中的作用的理解。