The genome sequence of Atlantic cod reveals a unique immune system

• Published in: Nature
• Main Authors: Star, Bastiaan, Nederbragt, Alexander J., Jentoft, Sissel, Grimholt, Unni, Malmstrøm, Martin, Gregers, Tone F., Rounge, Trine B., Paulsen, Jonas, Solbakken, Monica H., Sharma, Animesh, Wetten, Ola F., Lanzén, Anders, Winer, Roger, Knight, James, Vogel, Jan-Hinnerk, Aken, Bronwen, Andersen, Øivind, Lagesen, Karin, Tooming-Klunderud, Ave, Edvardsen, Rolf B., Tina, Kirubakaran G., Espelund, Mari, Nepal, Chirag, Previti, Christopher, Karlsen, Bård Ove, Moum, Truls, Skage, Morten, Berg, Paul R., Gjøen, Tor, Kuhl, Heiner, Thorsen, Jim, Malde, Ketil, Reinhardt, Richard, Du, Lei, Johansen, Steinar D., Searle, Steve, Lien, Sigbjørn, Nilsen, Frank, Jonassen, Inge, Omholt, Stig W., Stenseth, Nils Chr., Jakobsen, Kjetill S.
• Format: Text
• Language: English
• Published: 2011
• Subjects: Article; atlantic cod; Gadus morhua
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3537168; http://www.ncbi.nlm.nih.gov/pubmed/21832995; https://doi.org/10.1038/nature10342

Atlantic cod (Gadus morhua) is a large, cold-adapted teleost that sustains long-standing commercial fisheries and incipient aquaculture1,2. 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 vertebrates3,4, but we show that Atlantic cod has lost the genes for MHCII, CD4 and Ii that are essential for the function of this pathway. Nevertheless, Atlantic cod is not exceptionally susceptible to disease under natural conditions5. We find a highly expanded number of MHCI genes and a unique composition of its Toll-like receptor (TLR) families. This suggests how the Atlantic cod immune system has evolved compensatory mechanisms within both adaptive and innate immunity in the absence of MHCII. These observations affect fundamental assumptions about the evolution of the adaptive immune system and its components in vertebrates.