Research: HEAD AND SHOULDERS

In vertebrates, the skeleton and muscles of the shoulder and neck are formed as a composite rather than as separate systems, researchers at University College London and elsewhere have discovered.

In the past, the skeleton has been thought to be the basis of organisation in vertebrates, with distinct types of stem cell giving rise to the skeleton and muscles in separate processes.

Using a new genetic labelling technique able to track individual stem cells from the embryo to the adult animal, Dr Georgy Koentges from UCL, and colleagues in Sweden and the USA, found that mesenchymal stem cells were responsible for forming muscle scaffolds, the place where muscles anchor to bones, as well as the muscles themselves.

The work paints a completely new picture of vertebrate development. For example, cells derived from mesenchymal stem cells in the neural crest (a structure formed very early in embryonic development) anchor the head to the front of the shoulder. A separate population, originating from mesodermal stem cells, links trunk muscles to the posterior neck and shoulder skeleton.

These new findings explain why some genetic disorders affect particular parts of the neck and shoulders: the mutations affect specific populations of cells. They also shed light on the evolution of skeletons – for example, suggesting that a bone called the cleithrum, seen in extinct land animals, has become integrated into the shoulder blade in modern vertebrates.

This research was supported by the Wellcome Trust, the Biotechnology and Biological Sciences Research Council, the Medical Research Council, the US National Institutes of Health and the international Human Frontier Science Program.

External links

• Matsuoka T et al. Neural crest origins of the neck and shoulder. Nature 2005;436(7049):347–55.