Atlantic Cod Genome Reveals Gap in Immune System

Researchers have sequenced the genome of the commercially important fish in the Northern Hemisphere, the Atlantic cod. The genome further revealed that the fish has a unique mechanism in fighting diseases.

University of Oslo evolutionary geneticist Kjetill Jakobsen and his team sequenced the Atlantic cod's genome to understand how to manage cod fisheries but was surprised that their findings led to understanding of the immune system evolution. After comparing the DNA of Atlantic cod with stickleback, the closest relative of the fish whose genome has been decoded, they discovered that the cod do not have the genes that code for proteins called MHCII, CD4, and invariant chain. These proteins are vital in the immune system of almost all vertebrates, especially in combating bacterial attacks. When these proteins are absent, the animals are expected to exhibit week antibody response. However, that is not the case for Atlantic cod.

The researchers found another part of the genome that gave hints on how the fish can survive bacterial infections. Atlantic cods have a wide range of Toll-like receptors, which enables the immune system to have fast responses but less complicated than T and B cell responses. The said receptors are also more varied than the MHCI molecules.

While these findings elucidate Atlantic cod's immune capabilities, these are not good news to the aquaculture industry at the moment. Due to the fish's unique immune system, it is not advisable that they are farmed outside their natural environment. However, the findings may lead to the development of cod-appropriate vaccines, said Jakobsen.

Read the original article at http://news.sciencemag.org/sciencenow/2011/08/cod-genome-reveals-stunning-gap-.html.