Circular RNAs (circRNAs) are a novel class of endogenous ncRNA, which widely exist in the transcriptomes of different species and tissues. Recent studies indicate important roles for circRNAs in the regulation of gene expression by acting as competing endogenous RNAs (ceRNAs). However, the specific role of circRNAs in myogenesis is still poorly understood. In this study, we attempted to systematically identify the circRNAs involved in myogenesis and analyze the biological functions of circRNAs in chicken skeletal muscle development. In total, 532 circRNAs were identified as being differentially expressed between pectoralis major (PEM) and soleus (SOL) in 7-week-old Xinghua chicken. Among them, a novel circRNA (novel_circ_002621), generated by PTPN4 gene, was named circPTPN4 and identified. circPTPN4 is highly expressed in skeletal muscle, and its expression level is upregulated during myoblast differentiation. circPTPN4 facilitates the proliferation and differentiation of myoblast. Moreover, circPTPN4 suppresses mitochondria biogenesis and activates fast-twitch muscle phenotype. Mechanistically, circPTPN4 can function as a ceRNA to regulate NAMPT expression by sponging miR-499-3p, thus participating in AMPK signaling. circPTPN4 functions as a ceRNA to regulate NAMPT expression by sponging miR-499-3p, thus promoting the proliferation and differentiation of myoblast, as well as activating fast-twitch muscle phenotype.

中文翻译：

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circPTPN4 通过 miR-499-3p/NAMPT 轴调节肌生成

环状RNAs（circRNAs）是一类新型的内源性ncRNA，广泛存在于不同物种和组织的转录组中。最近的研究表明 circRNA 通过充当竞争性内源性 RNA (ceRNA) 在基因表达调控中的重要作用。然而，circRNAs 在肌生成中的具体作用仍然知之甚少。在这项研究中，我们试图系统地鉴定参与肌生成的circRNA，并分析circRNA在鸡骨骼肌发育中的生物学功能。在7周龄的兴化鸡中，总共鉴定出532个circRNA在胸大肌（PEM）和比目鱼肌（SOL）之间存在差异表达。其中，由PTPN4基因产生的一种新型circRNA（novel_circ_002621）被命名为circPTPN4并被鉴定。circPTPN4 在骨骼肌中高度表达，并且在成肌细胞分化过程中其表达水平上调。circPTPN4 促进成肌细胞的增殖和分化。此外，circPTPN4 抑制线粒体生物合成并激活快肌表型。从机制上讲，circPTPN4 可以作为 ceRNA 通过海绵化 miR-499-3p 来调节 NAMPT 表达，从而参与 AMPK 信号传导。circPTPN4 作为 ceRNA 通过海绵化 miR-499-3p 调节 NAMPT 表达，从而促进成肌细胞的增殖和分化，以及激活快肌表型。circPTPN4 可以作为 ceRNA 通过海绵化 miR-499-3p 来调节 NAMPT 表达，从而参与 AMPK 信号传导。circPTPN4 作为 ceRNA 通过海绵化 miR-499-3p 调节 NAMPT 表达，从而促进成肌细胞的增殖和分化，以及激活快肌表型。circPTPN4 可以作为 ceRNA 通过海绵化 miR-499-3p 来调节 NAMPT 表达，从而参与 AMPK 信号传导。circPTPN4 作为 ceRNA 通过海绵化 miR-499-3p 调节 NAMPT 表达，从而促进成肌细胞的增殖和分化，以及激活快肌表型。