Work by researchers at the Institute of Molecular Biology and Biotechnology (IMBB) in Greece, whose results are published today in the journal Science, reveals that the repeated parts of animal bodies - for example the vertebrae in our spine - are generated by a similar mechanism not only among vertebrates (fish, birds, mammals, etc.) but also in our more distant relatives, the insects.

All living organisms - humans, other animals, plants, microbes - are related to one another: they descend from common ancestors that lived hundreds of million years ago. They all share a common history that is evident in the structure of their genes and the functions of their cells. Apart from these similarities there are also important differences, mechanisms that have taken different evolutionary paths, explaining the differences that one easily observes when comparing plants, fungi and animals, or an insect, a fish and a mouse.

The vertebrae and the ribs of humans and other animals are perhaps the clearest indication that the body of vertebrates is made from repeated units, called somites. The somites form sequentially from head to tail as the embryo grows (in humans this occurs approximately 3 weeks after conception), by a mechanism that involves successive pulses of expression of specific regulatory genes. The mechanism is referred to as the 'segmentation clock'. The Development and Evolution team at IMBB, led by Dr Michalis Averof, developed new imaging techniques that enabled it to study the same process in insects, using a beetle as an experimental organism. Insects do not have vertebrae, but their body is composed of segments that form sequentially in the embryo. The team found that, similar to vertebrates, the formation of insect segments is accompanied by pulses of gene expression. We still do not know whether this similarity is due to our common origins with insects - i.e. whether this mechanism already existed in our common ancestors - or whether it reflects a similar mechanism that was invented independently in the insect and vertebrate lineages. Whatever the evolutionary origin of the mechanism, this work highlights the profound similarities that underlie development in diverse animals, and contributes to a better understanding of these mechanisms using a new experimental model.

The research was conducted at IMBB, in Heraklion (Crete), by Andres Sarrazin, Andrew Peel and Michalis Averof. It was funded by the European Union FP6 programmes Marie Curie 'CELLIMAGE' and 'ZOONET'.

Further information:
Michalis Averof (averof@imbb.forth)
http://www.imbb.forth.gr/people/averof/
http://www.sciencemag.org/content/early/2012/03/07/science.1218256