Surprising genetic finding

Scientists from the Sars International Centre for Marine Molecular Biology have presented completely new findings on the HOX genes - the “software” for animal design.

A few years ago, the scientists discovered the smallest genome among vertebrates in a tiny urochordate that goes by the name of Oikopleura dioica. The organism is about 5 mm long and its genome consists of only 70 million megabases (Mb). Although the human genome is forty times larger, Oikopleura is an excellent model organism. Studies of its compact genome may help to shed new light on the human genome, and scientists at the Sars Centre have already made a number of surprising discoveries.

Their studies involved examining what are known as HOX genes. These important genes are common for all animals and they help to control development from the stage of the fertilised egg to the formation of the general body structure. In human beings, they make sure that our fingers and ribs, for example, grow to the right shape and length.

In every species from the insects to human beings, the HOX genes lie clustered together in the chromosomes like pearls on a string. Scientists also believe that this grouping and sequence of the genes was of importance for their ability to function in a proper and coordinated way, i.e. that the HOX gene that lies first on the chromosome, for example, controls the development of the posterior part of the brain, while number two affects the upper part of the neck, and so on along the main axis of the body. When the scientists at the Sars Centre found these genes in Oikopleura dioica, however, it turned out that this was by no means the case. In this species, the genes do not cluster, although it looks as though they function in the same way as in animals in which they do.

“This finding is interesting because it indicates that the generally accepted theory regarding the position and function of the HOX genes is over-simplified. This work is also of importance for our understanding of how body shapes develop in the animal world in general,” says Rolf Brudvik Edvardsen, a research fellow who is co-author of the article “Hox cluster disintegration with persistent anteroposterior order of expression in Oikopleura dioica,” which has been published in the journal “Nature”.

The research is led by Professor Daniel Chourrout, director of the Sars Centre, which has also been cooperating with two other centres of genome research in Paris and Berlin .

The Sars Centre is Norway ’s representative in the European Molecular Biology (EMBL) network - a heavyweight in European research. This means that in the course of only a few years, the Centre has won recognition as the foremost European research institution in its field.

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