Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, PO Box 1066, Blindern, N-0316 Oslo, Norway.
Nature. 2011 Aug 10;477(7363):207-10. doi: 10.1038/nature10342.
Atlantic cod (Gadus morhua) is a large, cold-adapted teleost that sustains long-standing commercial fisheries and incipient aquaculture. Here we present the genome sequence of Atlantic cod, showing evidence for complex thermal adaptations in its haemoglobin gene cluster and an unusual immune architecture compared to other sequenced vertebrates. The genome assembly was obtained exclusively by 454 sequencing of shotgun and paired-end libraries, and automated annotation identified 22,154 genes. The major histocompatibility complex (MHC) II is a conserved feature of the adaptive immune system of jawed vertebrates, but we show that Atlantic cod has lost the genes for MHC II, CD4 and invariant chain (Ii) that are essential for the function of this pathway. Nevertheless, Atlantic cod is not exceptionally susceptible to disease under natural conditions. We find a highly expanded number of MHC I genes and a unique composition of its Toll-like receptor (TLR) families. This indicates how the Atlantic cod immune system has evolved compensatory mechanisms in both adaptive and innate immunity in the absence of MHC II. These observations affect fundamental assumptions about the evolution of the adaptive immune system and its components in vertebrates.
大西洋鳕鱼（Gadus morhua）是一种大型冷水性远洋鱼类，支撑着长期存在的商业渔业和新兴的水产养殖业。在这里，我们呈现了大西洋鳕鱼的基因组序列，其中显示了其血红蛋白基因簇在复杂的热适应方面的证据，以及与其他已测序的脊椎动物相比，其不寻常的免疫结构。基因组组装完全是通过 454 测序的霰弹枪和配对末端文库获得的，自动注释确定了 22154 个基因。主要组织相容性复合体 (MHC) II 是有颌脊椎动物适应性免疫系统的一个保守特征，但我们表明，大西洋鳕鱼已经失去了 MHC II、CD4 和不变链 (Ii) 的基因，这些基因对于该途径的功能至关重要。然而，在自然条件下，大西洋鳕鱼并不会特别容易患病。我们发现大量扩展的 MHC I 基因和其 Toll 样受体 (TLR) 家族的独特组成。这表明在没有 MHC II 的情况下，大西洋鳕鱼的免疫系统如何在适应性免疫和固有免疫中进化出补偿机制。这些观察结果影响了关于脊椎动物适应性免疫系统及其成分进化的基本假设。
