The double-Ig-IL-1R related molecule (DIGIRR) is a member of the TIR (Toll -Interleukin-1 receptor) superfamily and plays an important role in the immune system, it is also as a negative regulator of the IL-1 signaling pathway. In this study, we identified and characterized the miiuy croaker DIGIRR (mmi-DIGIRR) gene. The results of gene structure analysis indicated that there were differences between the mmi-DIGIRR and mammalian SIGIRR, which there were two immunoglobulin (Ig) domains contained in extracellular region of mmi-DIGIRR. Sequence alignment analysis showed that fish DIGIRR shared some conserved sequences with other vertebrates and the evolution was relatively conservative. In order to further validate the function of mmi-DIGIRR and its expression levels in various tissues of fish, qRT-PCR has been conducted. The results showed DIGIRR has significant expression levels in liver, skin and muscle while expression levels in heart are low. The LPS-induced NF-κB activation was inhibited by overexpression of DIGIRR significantly. In conclusion, the evolution and function of mmi-DIGIRR were comprehensively analyzed in this study, which would provide a theoretical basis for the future research of fish DIGIRR.

双Ig-IL-1R相关分子（DIGIRR）是TIR（Toll -Interleukin-1受体）超家族的成员，在免疫系统中起着重要作用，它也是IL-1的负调节剂信号通路。在这项研究中，我们鉴定并鉴定了小黄鱼DIGIRR（mmi-DIGIRR）基因。基因结构分析结果表明，mmi-DIGIRR与哺乳动物SIGIRR之间存在差异，mmi-DIGIRR的胞外区含有两个免疫球蛋白（Ig）结构域。序列比对分析表明，鱼类DIGIRR与其他脊椎动物共有一些保守序列，进化相对保守。为了进一步验证mmi-DIGIRR的功能及其在鱼类各种组织中的表达水平，进行了qRT-PCR。结果表明，DIGIRR在肝脏，皮肤和肌肉中具有显着的表达水平，而在心脏中的表达水平较低。LPS诱导的NF-κB激活被DIGIRR的过表达明显抑制。综上，本研究对mmi-DIGIRR的进化和功能进行了综合分析，为今后鱼类DIGIRR的研究提供了理论依据。