Skeletal muscle development, a long-term and complex process, is controlled by a set of the myogenic genes. Circular RNAs (circRNAs), a class of noncoding RNA, have been shown to regulate various biological processes. Recent studies indicate circRNAs may be involved in myogenesis, but the role and regulatory mechanism of circRNAs in myogenesis is largely unknown. In the present study, circCPE was firstly found to promote the bovine myoblast proliferation and inhibit cell apoptosis and differentiation by influencing the expression of FOXC1 in a miR138-mediated manner. And in vivo experiments revealed that overexpression of circCPE attenuates skeletal muscle regeneration. We identified a novel circular RNA circCPE by analyzing circRNAs sequencing data of bovine muscle tissue. Sequencing verification, RNase R treatment and Actinomycin D treatment confirmed the circular nature of circCPE in bovine muscle. Functional assays showed that overexpression of circCPE could inhibit bovine myoblast apoptosis and differentiation, as well as facilitate cell proliferation. Moreover, in vivo experiments revealed that overexpression of circCPE attenuates skeletal muscle regeneration. In consideration of circRNA action as miRNAs sponge, we found that circCPE harbors miR-138 binding sites and absorbed miR-138. Mechanistically, the rescue experiments showed that the overexpression of circCPE can counteract the inhibitory effect of miR-138 on the cell proliferation and the accelerated effects on the differentiation and apoptosis. Subsequently, we found that circCPE sequester the inhibitory effect of miR-138 on FOXC1 so as to involve in myogenesis. Collectively, we constructed a novel circCPE/miR-138/FOXC1 regulatory network in bovine myogenesis, which further provide stronger evidence that circRNA involved in muscle development acting as miRNA sponge.

中文翻译：

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环状RNA circCPE通过海绵miR-138调节成肌细胞发育

骨骼肌发育是一个长期而复杂的过程，由一组生肌基因控制。环状RNA（circRNA）是一类非编码RNA，已被证明可以调节各种生物过程。最近的研究表明 circRNAs 可能参与肌生成，但 circRNAs 在肌生成中的作用和调控机制在很大程度上是未知的。在本研究中，首次发现circCPE通过以miR138介导的方式影响FOXC1的表达来促进牛成肌细胞增殖并抑制细胞凋亡和分化。体内实验表明，circCPE 的过度表达会减弱骨骼肌再生。我们通过分析牛肌肉组织的 circRNAs 测序数据鉴定了一种新的环状 RNA circCPE。测序验证，RNase R 处理和放线菌素 D 处理证实了牛肌肉中 circCPE 的循环性质。功能测定表明，circCPE的过表达可以抑制牛成肌细胞凋亡和分化，并促进细胞增殖。此外，体内实验表明，circCPE 的过表达会减弱骨骼肌再生。考虑到 circRNA 作为 miRNA 海绵的作用，我们发现 circCPE 具有 miR-138 结合位点并吸收 miR-138。机制上，拯救实验表明circCPE的过表达可以抵消miR-138对细胞增殖的抑制作用和对分化和凋亡的加速作用。随后，我们发现 circCPE 隔离了 miR-138 对 FOXC1 的抑制作用，从而参与了肌生成。总的来说，