Wang Hui-Ju, Xiang Li-Xin, Shao Jian-Zhong, Jia Shen
College of Life Sciences, Zhejiang University, Hangzhou 310012, PR China.
Cytokine. 2006 Aug;35(3-4):126-34. doi: 10.1016/j.cyto.2006.07.010. Epub 2006 Sep 20.
Interleukin-21 (IL-21) is an important immune cytokine that was well characterized in human and mammals, but little is known in fish. In present study, an IL-21 homologue was cloned and well characterized from Tetraodon nigroviridis. The full-length Tetraodon IL-21 cDNA was 849bp in size, containing an open reading frame (ORF) of 438bp that translated a 145 amino-acid peptide, a 5' untranslated region (UTR) of 69bp, and a 3' UTR of 342bp. The deduced peptide shared identity of 20-49% with other known IL-21 sequences. The Tetraodon IL-21 gene had six exons while both human and Takifugu IL-21 gene contained only five exons. However, the level of synteny between human, Takifugu and Tetraodon genomes was well conserved during evolution. In vivo expression study showed that Tetraodon IL-21 mRNAs were constitutively expressed at a low level and only in limited tissues, including gut, gill and gonad in healthy fish, and stimulation with LPS increased the expression of IL-21 in these tissues and induced the expression of IL-21 in kidney, spleen and skin, indicating that IL-21 is an inflammatory stress inducible gene associated with the anti-bacterial defense in fish. Our study provided further evidence for the existence of IL-21 in fish, and gained further insight into the immunological functions of IL-21 gene in fish.
白细胞介素-21（IL-21）是一种重要的免疫细胞因子，在人类和哺乳动物中已得到充分研究，但在鱼类中的了解却很少。在本研究中，从黑青斑河鲀中克隆并鉴定了一种IL-21同源物。黑青斑河鲀IL-21 cDNA全长849bp，包含一个438bp的开放阅读框（ORF），可翻译出一个145个氨基酸的肽段，一个69bp的5'非翻译区（UTR）和一个342bp的3'UTR。推导的肽段与其他已知IL-21序列的同源性为20%-49%。黑青斑河鲀IL-21基因有六个外显子，而人类和红鳍东方鲀的IL-21基因都只有五个外显子。然而，在进化过程中，人类、红鳍东方鲀和黑青斑河鲀基因组之间的同线性水平保守性良好。体内表达研究表明，黑青斑河鲀IL-21 mRNA在健康鱼类中仅在包括肠道、鳃和性腺在内的有限组织中以低水平组成性表达，用LPS刺激可增加这些组织中IL-21的表达，并诱导肾脏、脾脏和皮肤中IL-21的表达，表明IL-21是一种与鱼类抗菌防御相关的炎症应激诱导基因。我们的研究为鱼类中IL-21的存在提供了进一步的证据，并进一步深入了解了IL-21基因在鱼类中的免疫功能。
