Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, 650500, China.
LPS, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing, 210008, China; State Key Laboratory of Pharmaceutical Biotechnology, School of Life Science, Nanjing University, Nanjing, 210023, China.
Fish Shellfish Immunol. 2019 Mar;86:1053-1057. doi: 10.1016/j.fsi.2018.12.061. Epub 2018 Dec 25.
Amphioxus is a key model for studying comparative immunity of vertebrates. Circular RNA (circRNA), as RNAs with a circular structure, has received little attention until recently, where several studies have reported that circRNA expression changes are involved in the immune response in animals. However, circRNA and its immune role in amphioxus have not been previously studied. Here, circRNAs in Chinese amphioxus (Branchiostoma belcheri) were sequenced, and 1859 circRNAs were identified using two algorithms (find_circ and CIRI). The analysis of miRNA target sites on circRNAs showed that 332 circRNAs may function as miRNA sponges. Furthermore, we identified circRNAs that were conserved between B. belcheri and vertebrates, tracing the origin of these circRNAs within chordates. Additionally, in combination with several key antiviral immune (poly(I:C), pIC) pathways identified in our previous B. belcheri studies, nine circRNAs potentially involved in these pathways were identified using bioinformatic predictions. Among these nine circRNAs, eight were selected to examine their expression response in B. belcheri challenged by pIC in comparison to control using real-time quantitative PCR. The results showed that four circRNAs were induced as part of the antiviral response against pIC, while expression of two circRNAs was decreased, and the expression levels of the remaining two were not significantly altered after pIC challenge. This work is the first to identify circRNAs and reveal their antiviral role in amphioxus. Therefore, it opens a new window to explore the comparative immunology of circRNAs in chordates and the regulatory roles of circRNAs in antiviral immunity in amphioxus.
文昌鱼是研究脊椎动物比较免疫学的重要模式生物。环状 RNA（circRNA）作为具有环状结构的 RNA，直到最近才受到关注，有几项研究报道circRNA 的表达变化参与了动物的免疫反应。然而，文昌鱼中的 circRNA 及其免疫作用尚未被研究过。本研究对中国文昌鱼（Branchiostoma belcheri）的 circRNA 进行了测序，使用两种算法（find_circ 和 CIRI）鉴定了 1859 个 circRNA。circRNA 上 miRNA 靶位点的分析表明，332 个 circRNA 可能作为 miRNA 海绵发挥作用。此外，我们鉴定了在文昌鱼和脊椎动物之间保守的 circRNA，追踪了这些 circRNA 在脊索动物中的起源。此外，结合我们之前在文昌鱼研究中鉴定的几个关键抗病毒免疫（多聚肌苷酸：聚肌胞苷酸（poly(I:C)），pIC）途径，通过生物信息学预测，鉴定了 9 个可能参与这些途径的 circRNA。在这 9 个 circRNA 中，选择了 8 个进行实时定量 PCR 检测，比较 pIC 刺激前后文昌鱼中这些 circRNA 的表达变化。结果表明，有 4 个 circRNA 作为抗病毒反应的一部分被诱导，而 2 个 circRNA 的表达水平降低，另外 2 个 circRNA 的表达水平在 pIC 刺激后没有明显改变。这项工作首次鉴定了 circRNA，并揭示了它们在文昌鱼中的抗病毒作用。因此，它为探索脊椎动物 circRNA 的比较免疫学以及文昌鱼抗病毒免疫中 circRNA 的调控作用开辟了新的窗口。
