The Fish Molecular Genetics and Biotechnology Laboratory, Department of Fisheries and Allied Aquacultures and Program of Cell and Molecular Biosciences, Aquatic Genomics Unit, Auburn University, Auburn, AL 36849, USA.
Dev Comp Immunol. 2012 May;37(1):77-86. doi: 10.1016/j.dci.2011.12.005. Epub 2011 Dec 16.
Innate immune system plays a significant role in all multicellular organisms. The key feature of the system is its ability to recognize and respond to invading microorganisms. Vertebrates including teleost fish have evolved an array of pathogen recognition receptors (PRRs) for detecting and responding to various pathogen-associated molecular patterns (PAMPs), including Toll-like receptors (TLRs), nucleotide-binding domain, leucine-rich repeat containing receptors (NLRs), and the retinoic acid inducible gene I (RIG-I) like receptors (RLRs). In this study, we identified 22 NLRs including six members of the NLR-A subfamily (NODs), two members of the NLR-B subfamily, 11 members of the NLR-C subfamily, and three genes that do not belong to any of these three subfamilies: Apaf1, CIITA, and NACHT-P1. Phylogenetic analysis indicated that orthologs of the mammalian NOD1, NOD2, NOD3, NOD4, and NOD5 were all identified in catfish. In addition, an additional truncated NOD3-like gene was also identified in catfish. While the identities of subfamily A NLRs could be established, the identities of the NLR-B and NLR-C subfamilies were inconclusive at present. Expression of representative NLR genes was analyzed using RT-PCR and qRT-PCR. In healthy catfish tissues, all the tested NLR genes were found to be ubiquitously expressed in all 11 tested catfish tissues. Analysis of expression of these representative NLR genes after bacterial infection with Edwardsiella ictaluri revealed a significant up-regulation of all tested genes in the spleen and liver, but a significant down-regulation in the intestine and head kidney, suggesting their involvement in the immune responses of catfish against the intracellular bacterial pathogen in a tissue-specific manner. The up-regulation and down-regulation of the tested genes exhibited an amazing similarity of expression profiles after infection, suggesting the co-regulation of these genes.
先天免疫系统在所有多细胞生物中都起着重要作用。该系统的关键特征是能够识别和响应入侵的微生物。包括硬骨鱼在内的脊椎动物已经进化出一系列病原体识别受体（PRRs），用于检测和响应各种病原体相关分子模式（PAMPs），包括 Toll 样受体（TLRs）、核苷酸结合域、富含亮氨酸重复序列受体（NLRs）和视黄酸诱导基因 I（RIG-I）样受体（RLRs）。在这项研究中，我们鉴定了 22 个 NLRs，包括 NLR-A 亚家族的 6 个成员（NODs）、NLR-B 亚家族的 2 个成员、NLR-C 亚家族的 11 个成员以及不属于这三个亚家族的 3 个基因：Apaf1、CIITA 和 NACHT-P1。系统发育分析表明，鲶鱼中均鉴定出哺乳动物 NOD1、NOD2、NOD3、NOD4 和 NOD5 的同源物。此外，还在鲶鱼中鉴定出一个额外的截断 NOD3 样基因。虽然可以确定亚家族 A NLR 的身份，但目前还不能确定 NLR-B 和 NLR-C 亚家族的身份。使用 RT-PCR 和 qRT-PCR 分析代表性 NLR 基因的表达。在健康的鲶鱼组织中，所有测试的 NLR 基因在 11 种测试的鲶鱼组织中均广泛表达。用爱德华氏菌感染后分析这些代表性 NLR 基因的表达，发现所有测试基因在脾脏和肝脏中均显著上调，但在肠道和头肾中显著下调，表明它们以组织特异性方式参与鲶鱼对胞内细菌病原体的免疫反应。感染后测试基因的上调和下调表现出惊人相似的表达谱，表明这些基因的共同调控。
