中文摘要：

髓样分化因子（myeloid differentiation factor88，MyD88）是TLR（toll-like receptor）信号通路的关键接头蛋白，在先天性免疫中发挥重要作用。实验首次克隆了欧洲鳗鲡MyD88基因cDNA全长序列，命名为AaMyD88，其全长为1539bp，开放阅读框为846bp，编码282个氨基酸。该蛋白三维丝带空间结构图与人类的MyD88十分相似，具有MyD88家族典型的死亡结构域和TIR（toll-1ike／IL-1receptor）结构域，其中TIR结构域中含有3个序列高度保守的boxl、box2和box3。同源性分析显示，欧洲鳗鲡MyD88氨基酸序列与斑点叉尾鲴相似性最高，为76．3％，与其他鱼类相似性为67．5％～73．2％，与哺乳动物相似性较低，为61．6％～62．6％。欧洲鳗鲡MyD88在系统进化树中与其他鱼类MyD88聚为一支，哺乳类以及两栖类MyD88分别聚为一支。实时荧光定量PCR检测发现，AaMyD88基因在欧洲鳗鲡各组织器官中均有表达，其中在肝脏中的表达量最高，心脏、肠、脾脏以及肾脏中也有较高的表达，而肌肉和鳃中的表达水平较低；欧洲鳗鲡经山羊IgG肌肉注射后，肾脏AaMyD88基因在第7天表达量有显著性提高，14d后恢复至正常水平，而脾脏AaMyD88基因表达水平从第7～21天持续显著上调，于第7天达到峰值，其表达量为肾脏的1．7倍；欧洲鳗鲡鳍细胞系经polyI：C处理后，AaMyD88基因表达水平在3h显著降低，6-48h均有显著升高，于12h达到峰值。LPS处理后的欧洲鳗鲡鳍细胞系AaMyD88基因表达水平在3h显著降低，6和12h显著升高，于12h达到峰值，24h后恢复至正常水平。polyI：C处理组MyD88基因表达水平在12～48h均显著高于LPS处理组。研究表明，MyD88在欧洲鳗鲡抵御外源微生物的免疫应答反应中发挥重要作用。

英文摘要：

Myeloid differentiation factor 88 （MyD88）is a universal and crucial adaptor protein of signal transduction activity elicited by TLR（ toll-like receptor）superfamily and plays an essential role in the innate immunity response. In this study, a MyD88 gene,AaMyD88, was cloned for the first time from Anguilla anguilla. Its full-length cDNA sequence is 1 539 bp,with an 846 bp open reading frame encoding a protein of 282 aa. The predicted three-dimensional structure of AaMyD88 can be merged well with the crystal structure of the human MyD88 and has the typical death domain and TIR（toll-like/IL-1 receptor） domain of the MyD88 family. In the TIR domain, three conserved boxes, named box 1, box 2 and box 3, are found. According to the comparison with known MyD88 amino acid sequences,the putative protein of AaMyD88 showed the highest identities with Ictalurus punctatus（76.3 % ）, and other bony fishes （67.5 % -73.2% ）, but low identities （61.6% - 62.6% ） with mammalian. All the sequences were clustered into three main branches in which all MyD88 of fish clustered together,while the MyD88 of mammalians and amphibians formed two separate clusters, qRT-PCR revealed the expression of AaMyD88 could be detected in all adult tissues examined. The highest expression level was observed in the liver, followed by the heart, intestine, and spleen,and the lowest expression level was found in muscle and gills. After injection with goat IgG, the AaMyD88 expression level was obviously up-regulated in the kidney at 7 d and returned to the normal level after 14 d. The obvious up-regulation of the AaMyD88 expression level was observed in the spleen from 7 d to 21 d,peaking at 7 d with a value 1.7 times higher than that of the kidney. After stimulation with poly I： C ,AaMyD88 transcripts in fin cell line were down-regulated significantly at 3 h, increased strongly from 6 h to 48 h,and peaked at 12 h. After treatment with LPS ,the expression level of AaMyD88 in fin cell line was sharply down-regulated at 3 h and began to