A cDNA microarray (18 263 probes) was used for transcriptome analysis of bovine skeletal muscle (m. semitendinosus) in 12-month-old bulls of the beef breed Limousin (LIM) and the typical dairy breed Holstein-Friesian (HF, used as a reference). We aimed to identify the genes whose expression may reflect the muscle phenotype of beef bulls. A comparison of muscle transcriptional profiles revealed significant differences in expression of 393 genes between HF and LIM. We classified biological functions of 117 genes with over 2-fold differences in expression between the examined breeds. Among them, 72 genes were up-regulated and 45 genes were down-regulated in LIM vs. HF. The genes were involved in protein metabolism and modifications (22 genes), signal transduction (15), nucleoside, nucleotide and nucleic acid metabolism (13), cell cycle (9), cell structure and motility (9), developmental processes (9), intracellular protein traffic (7), cell proliferation and differentiation (6), cell adhesion (6), lipid, fatty acid and steroid metabolism (5), transport (5), and other processes. For the purpose of microarray data validation, we randomly selected 4 genes:trip12, mrps30, pycrl, andc-erbb3. Real-time RT-PCR results showed similar trends in gene expression changes as those observed in microarray studies. Basing on results of the present study, we proposed a model of the regulation of skeletal muscle growth and differentiation, with a principal role of the somatotropic pathway. It may explain at least in part the development of muscle phenotype in LIM bulls. We assume that the growth hormone directly or indirectly (through IGF-1) activates the calcium-signaling pathway with calcineurin, which stimulates myogenic regulatory factors (MRFs) and inhibits early growth response gene. The inhibition results in indirect activation of MRFs and impaired activation of TGF-beta1 and myostatin, which finally facilitates terminal muscle differentiation.

中文翻译：

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比较奶牛和牛肉品种公牛的骨骼肌转录谱。

使用 cDNA 微阵列（18 263 个探针）对牛骨骼肌（m. semitendinosus) 在 12 个月大的牛肉品种 Limousin (LIM) 和典型的奶牛品种 Holstein-Friesian (HF，用作参考) 中。我们旨在确定其表达可能反映肉牛肌肉表型的基因。肌肉转录谱的比较揭示了 HF 和 LIM 之间 393 个基因表达的显着差异。我们对 117 个基因的生物学功能进行了分类，这些基因在所检查的品种之间的表达差异超过 2 倍。其中，LIM vs. HF中有72个基因上调，45个基因下调。这些基因涉及蛋白质代谢和修饰（22 个基因）、信号转导（15 个）、核苷、核苷酸和核酸代谢（13 个）、细胞周期（9 个）、细胞结构和运动性（9 个）、发育过程（9 个） , 细胞内蛋白质运输 (7), 细胞增殖和分化 (6)、细胞粘附 (6)、脂质、脂肪酸和类固醇代谢 (5)、运输 (5) 和其他过程。出于微阵列数据验证的目的，我们随机选择了 4 个基因：trip12、mrps30、pycrl和c-erbb3。实时 RT-PCR 结果显示基因表达变化的趋势与微阵列研究中观察到的趋势相似。基于本研究的结果，我们提出了骨骼肌生长和分化调节的模型，其中主要作用是生长激素途径。它至少可以部分解释 LIM 公牛肌肉表型的发展。我们假设生长激素直接或间接（通过 IGF-1）通过钙调神经磷酸酶激活钙信号通路，从而刺激生肌调节因子 (MRF) 并抑制早期生长反应基因。抑制导致 MRF 的间接激活和 TGF-β1 和肌生长抑制素的激活受损，最终促进终末肌肉分化。