MicroRNAs (miRNAs) are small noncoding RNAs of approximately 22 nucleotides, highly conserved among species, which modulate gene expression by cleaving messenger RNA target or inhibiting translation. MiRNAs are involved in the regulation of many processes including cell proliferation, differentiation, neurogenesis, angiogenesis, and apoptosis. Beef tenderness is an organoleptic characteristic of great influence in the acceptance of meat by consumers. Previous studies have shown that collagen level, marbling, apoptosis and proteolysis are among the many factors that affect beef tenderness. Considering that miRNAs can modulate gene expression, this study was designed to identify differentially expressed miRNAs that could be modulating biological processes involved with beef tenderness. Deep sequence analysis of miRNA libraries from longissimus thoracis muscle allowed the identification of 42 novel and 308 known miRNAs. Among the known miRNAs, seven were specifically expressed in skeletal muscle. Differential expression analysis between animals with high (H) and low (L) estimated breeding values for shear force (EBVSF) revealed bta-mir-182 and bta-mir-183 are up-regulated (q value < 0.05) in animals with L EBVSF, and bta-mir-338 is up-regulated in animals with H EBVSF. The number of bovine predicted targets for bta-mir-182, bta-mir-183 and bta-mir-338 were 811, 281 and 222, respectively, which correspond to 1204 unique target genes. Among these, four of them, MEF2C, MAP3K2, MTDH and TNRC6B were common targets of the three differentially expressed miRNAs. The functional analysis identified important pathways related to tenderness such as apoptosis and the calpain–calpastatin system. The results obtained indicate the importance of miRNAs in the regulatory mechanisms that influence muscle proteolysis and meat tenderness and contribute to our better understanding of the role of miRNAs in biological processes associated with beef tenderness.

中文翻译：

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MiRNA在动物骨骼肌中差异表达，其牛肉嫩度的估计育种值不同。

微小RNA（miRNA）是大约22个核苷酸的小型非编码RNA，在物种之间高度保守，可通过切割信使RNA靶标或抑制翻译来调节基因表达。MiRNA参与许多过程的调控，包括细胞增殖，分化，神经发生，血管生成和凋亡。牛肉嫩度是消费者对肉类的接受程度具有很大影响的感官特征。先前的研究表明，胶原蛋白水平，大理石花纹，细胞凋亡和蛋白水解作用是影响牛肉嫩度的众多因素之一。考虑到miRNA可以调节基因表达，因此本研究旨在鉴定差异表达的miRNA，这些miRNA可以调节与牛肉嫩度有关的生物过程。对来自胸最长肌的miRNA文库的深度序列分析可以鉴定出42种新颖的和308种已知的miRNA。在已知的miRNA中，有七个在骨骼肌中特异性表达。具有高（H）和低（L）剪切力估计繁殖值（EBVSF）的动物之间的差异表达分析表明，在L（L）动物中bta-mir-182和bta-mir-183上调（q值<0.05） EBVSF和bta-mir-338在H EBVSF的动物中上调。bta-mir-182，bta-mir-183和bta-mir-338的牛预测靶标分别为811、281和222，对应于1204个独特的靶标基因。其中，MEF2C，MAP3K2，MTDH和TNRC6B中的四个是三种差异表达的miRNA的共同靶标。功能分析确定了与压痛有关的重要途径，例如细胞凋亡和钙蛋白酶-钙蛋白酶抑制剂系统。获得的结果表明，miRNA在影响肌肉蛋白水解和肉嫩度的调节机制中的重要性，并有助于我们更好地理解miRNA在与牛肉嫩度有关的生物过程中的作用。