Zhu Yaoyao, Qi Chenchen, Shan Shijuan, Zhang Fumiao, Li Hua, An Liguo, Yang Guiwen
Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Science, Shandong Normal University, No. 88 East Wenhua Road, Jinan, 250014, People's Republic of China.
BMC Vet Res. 2016 Jun 27;12(1):127. doi: 10.1186/s12917-016-0750-4.
Common carp (Cyprinus carpio L.), one of the most economically valuable commercial farming fish species in China, is often infected by a variety of viruses. As the first line of defence against microbial pathogens, the innate immune system plays a crucial role in teleost fish, which are lower vertebrates. Interferon (IFN) regulatory factor 5 (IRF5) is a key molecule in antiviral immunity that regulating the expression of IFN and other pro-inflammatory cytokines. It is necessary to gain more insight into the common carp IFN system and the function of fish IRF5 in the antiviral and antibacterial response.
In the present study, we characterized the cDNA and genomic sequence of the IRF5 gene in common carp, and analysed tissue distribution and expression profile of this gene in response to polyinosinic:polycytidylic acid (poly I:C) and lipopolysaccharides (LPS) treatment. The common carp IRF5 (ccIRF5) gene is 5790 bp in length and is composed of 9 exons and 8 introns. The open reading frame (ORF) of ccIRF5 is 1554 bp, and encodes 517 amino acid protein. The putative ccIRF5 protein shares identity (65.4-90.0 %) with other fish IRF5s and contains a DNA binding domain (DBD), a middle region (MR), an IRF-associated domain (IAD), a virus activated domain (VAD) and two nuclear localization signals (NLSs) similar to those found in vertebrate IRF5. Phylogenetic analysis clustered ccIRF5 into the IRF5 subfamily with other vertebrate IRF5 and IRF6 genes. Real-time PCR analysis revealed that ccIRF5 mRNA was expressed in all examined tissues of healthy carps, with high levels observed in the gills and the brain. After poly I:C challenge, expression levels of ccIRF5, tumour-necrosis factor α (ccTNFα) and two IFN stimulated genes [ISGs (ccISG5 and ccPKR)] were up-regulated in seven immune-related tissues (liver, spleen, head kidney, foregut, hindgut, skin and gills). Furthermore, all four genes were up-regulated in vitro upon poly I:C and LPS challenges.
Our findings suggest that IRF5 might play an important role in regulating the antiviral and antibacterial response in fish. These results could provide a clue for preventing common carp infection by pathogenic microorganisms present in the aquatic environment.
鲤鱼（Cyprinus carpio L.）是中国经济价值最高的商业养殖鱼类之一，常受到多种病毒感染。作为抵御微生物病原体的第一道防线，先天免疫系统在硬骨鱼类（较低等的脊椎动物）中起着至关重要的作用。干扰素（IFN）调节因子5（IRF5）是抗病毒免疫中的关键分子，可调节IFN和其他促炎细胞因子的表达。有必要更深入地了解鲤鱼IFN系统以及鱼类IRF5在抗病毒和抗菌反应中的功能。
在本研究中，我们对鲤鱼IRF5基因的cDNA和基因组序列进行了表征，并分析了该基因在响应聚肌苷酸：聚胞苷酸（poly I:C）和脂多糖（LPS）处理时的组织分布和表达谱。鲤鱼IRF5（ccIRF5）基因长度为5790 bp，由9个外显子和8个内含子组成。ccIRF5的开放阅读框（ORF）为1554 bp，编码517个氨基酸的蛋白质。推测的ccIRF5蛋白与其他鱼类IRF5具有同一性（65.4 - 90.0%），并包含一个DNA结合域（DBD）、一个中间区域（MR）、一个IRF相关域（IAD）、一个病毒激活域（VAD）以及两个与脊椎动物IRF5中发现的类似的核定位信号（NLS）。系统发育分析将ccIRF5与其他脊椎动物IRF5和IRF6基因聚类到IRF5亚家族中。实时PCR分析显示，ccIRF5 mRNA在健康鲤鱼的所有检测组织中均有表达，在鳃和脑中表达水平较高。在poly I:C刺激后，ccIRF5、肿瘤坏死因子α（ccTNFα）和两个IFN刺激基因[ISGs（ccISG5和ccPKR）]在七个免疫相关组织（肝脏、脾脏、头肾、前肠、后肠、皮肤和鳃）中的表达水平上调。此外，在体外经poly I:C和LPS刺激后，所有四个基因均上调。
我们的研究结果表明，IRF5可能在调节鱼类的抗病毒和抗菌反应中起重要作用。这些结果可为预防鲤鱼受到水环境中存在的病原微生物感染提供线索。
