Zhang Pengpeng, Sheng Mingxuan, Du Chunyu, Chao Zhe, Xu Haixia, Cheng Xiaofang, Li Cencen, Xu Yongjie
Department of Biotechnology, College of Life Sciences, Xinyang Normal University, Xinyang, China.
Institute of Animal Science and Veterinary Medicine, Hainan Academy of Agricultural Sciences, Haikou, China.
Front Genet. 2021 Oct 22;12:769690. doi: 10.3389/fgene.2021.769690. eCollection 2021.
Brown adipose tissue (BAT) is specialized for energy expenditure, thus a better understanding of the regulators influencing BAT development could provide novel strategies to defense obesity. Many protein-coding genes, miRNAs, and lncRNAs have been investigated in BAT development, however, the expression patterns and functions of circRNA in brown adipogenesis have not been reported yet. This study determined the circRNA expression profiles across brown adipogenesis (proliferation, early differentiated, and fully differentiated stages) by RNA-seq. We identified 3,869 circRNAs and 36.9% of them were novel. We found the biogenesis of circRNA was significantly related to linear mRNA transcription, meanwhile, almost 70% of circRNAs were generated by alternative back-splicing. Next, we examined the cell-specific and differentiation stage-specific expression of circRNAs. Compared to white adipocytes, nearly 30% of them were specifically expressed in brown adipocytes. Further, time-series expression analysis showed circRNAs were dynamically expressed, and 117 differential expression circRNAs (DECs) in brown adipogenesis were identified, with 77 upregulated and 40 downregulated. Experimental validation showed the identified circRNAs could be successfully amplified and the expression levels detected by RNA-seq were reliable. For the potential functions of the circRNAs, GO analysis suggested that the decreased circRNAs were enriched in cell proliferation terms, while the increased circRNAs were enriched in development and thermogenic terms. Bioinformatics predictions showed that DECs contained numerous binding sites of functional miRNAs. More interestingly, most of the circRNAs contained multiple binding sites for the same miRNA, indicating that they may facilitate functions by acting as microRNA sponges. Collectively, we characterized the circRNA expression profiles during brown adipogenesis and provide numerous novel circRNAs candidates for future brown adipogenesis regulating studies.
棕色脂肪组织（BAT）专门用于能量消耗，因此更好地了解影响BAT发育的调节因子可为预防肥胖提供新策略。许多蛋白质编码基因、miRNA和lncRNA已在BAT发育中得到研究，然而，circRNA在棕色脂肪生成中的表达模式和功能尚未见报道。本研究通过RNA测序确定了棕色脂肪生成（增殖、早期分化和完全分化阶段）过程中的circRNA表达谱。我们鉴定出3869个circRNA，其中36.9%是新发现的。我们发现circRNA的生物合成与线性mRNA转录显著相关，同时，近70%的circRNA是通过可变反向剪接产生的。接下来，我们研究了circRNA的细胞特异性和分化阶段特异性表达。与白色脂肪细胞相比，近30%的circRNA在棕色脂肪细胞中特异性表达。此外，时间序列表达分析表明circRNA动态表达，在棕色脂肪生成中鉴定出117个差异表达circRNA（DEC），其中77个上调，40个下调。实验验证表明，鉴定出的circRNA能够成功扩增且RNA测序检测到的表达水平可靠。对于circRNA的潜在功能，GO分析表明下调的circRNA在细胞增殖相关术语中富集，而上调的circRNA在发育和产热相关术语中富集。生物信息学预测表明DEC包含大量功能性miRNA的结合位点。更有趣的是，大多数circRNA包含同一miRNA的多个结合位点，表明它们可能通过充当微小RNA海绵促进相关功能。总体而言，我们描绘了棕色脂肪生成过程中的circRNA表达谱，并为未来棕色脂肪生成调节研究提供了众多新的circRNA候选物。
