College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, Shenyang 110866, China.
Department of Animal Genetics, Breeding and Reproduction, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
J Agric Food Chem. 2022 Apr 6;70(13):4123-4137. doi: 10.1021/acs.jafc.1c07358. Epub 2022 Mar 24.
Intramuscular fat (IMF) content plays an important role in pork quality. Circular RNAs (circRNAs) implicate various biological processes; however, the regulatory mechanisms and functions of circRNAs in porcine IMF remains elusive. Hence, the study assessed the circRNA expression profiling in the longissimus dorsi muscle of pigs with high (H) and low (L) IMF content to unravel their regulatory functions in improving meat quality. The RNA sequencing analysis identified 29,732 circRNAs from six sampled pigs, most of which were exon-derived. In the muscle, 336 were differentially expressed (DE) between the H and L IMF groups; 196 circRNAs were upregulated, and 140 were downregulated. Subsequent qRT-PCR validation of 10 DE circRNAs revealed expression patterns consistent with the RNA-seq data. Gene ontology and KEGG enrichment analysis revealed that most significantly enriched DE circRNAs' host genes were linked to lipid metabolism and adipogenesis processes. The circRNA-miRNA regulatory network analysis found several circRNAs targeting miRNAs associated with adipogenesis. Finally, a novel circRNA, circPPARA, was identified with the expression positively correlated with the IMF content. Detailed analysis revealed that circPPARA was formed via head-to-tail splicing and was more stable than the linear PPARA, predominantly located in the cytoplasm. Functional studies using overexpression and siRNA constructs demonstrated that circPPARA promotes differentiation and hinders the proliferation of porcine intramuscular preadipocytes. Moreover, the dual-luciferase assay revealed that circPPARA adsorbed miR-429 and miR-200b, thereby promoting intramuscular adipogenesis in pigs. Our results identified a candidate circRNA, circPPARA, that affects porcine IMF content. The study provides knowledge of the regulatory functions of circRNAs in intramuscular adipogenesis and abundant resource for future research on circRNAs in pigs.
肌内脂肪（IMF）含量在猪肉品质中起着重要作用。环状 RNA（circRNA）涉及多种生物学过程；然而，circRNA 在猪 IMF 中的调控机制和功能仍不清楚。因此，本研究评估了高（H）和低（L）IMF 含量猪背最长肌中的 circRNA 表达谱，以揭示其在改善肉质中的调控功能。RNA 测序分析从 6 头采样猪中鉴定出 29732 个 circRNA，其中大多数是外显子衍生的。在肌肉中，H 和 L IMF 组之间有 336 个 circRNA 表达差异（DE）；196 个 circRNA 上调，140 个 circRNA 下调。随后对 10 个 DE circRNA 的 qRT-PCR 验证显示与 RNA-seq 数据一致的表达模式。GO 和 KEGG 富集分析表明，大多数显著富集的 DE circRNA 宿主基因与脂质代谢和脂肪生成过程有关。circRNA-miRNA 调控网络分析发现了几个靶向与脂肪生成相关的 miRNA 的 circRNA。最后，鉴定出一个与 IMF 含量呈正相关表达的新型 circRNA，circPPARA。详细分析表明，circPPARA 通过头尾拼接形成，比线性 PPARA 更稳定，主要位于细胞质中。使用过表达和 siRNA 构建体进行的功能研究表明，circPPARA 促进了猪肌内前体脂肪细胞的分化，抑制了其增殖。此外，双荧光素酶报告基因实验表明，circPPARA 吸附 miR-429 和 miR-200b，从而促进了猪的肌内脂肪生成。我们的研究结果确定了一个候选 circRNA，circPPARA，它影响猪的 IMF 含量。该研究为 circRNA 在肌内脂肪生成中的调控功能提供了知识，并为猪 circRNA 的进一步研究提供了丰富的资源。
