EARLY DEVELOPERS

Somehow, a single cell – the fertilised egg – has to generate an entire adult body, with all its body parts in the right place. In many organisms, the asymmetric distribution of key factors in the egg establishes polarities such as the front-to-back axis. In mammals, though, this process is more flexible and poorly understood. Dr Magdalena Zernicka-Goetz and colleagues have now shown that despite this flexibility, early patterns of cell division in mice can influence the course of development.

Dr Zernicka-Goetz, a Senior Research Fellow at the Gurdon Institute of Cancer and Developmental Biology in Cambridge, carefully manipulated one-cell mouse embryos before they divided. Her aim was to alter the plane of cell division, or how the contents of the cell are partitioned between daughter cells, and to use cell-labelling techniques to see what happened to the progeny of each cell.

Using such techniques she was able to show that, in most embryos, the first cell cleavage predicts the 'embryonic–abembryonic' axis – one daughter cell tends to give rise to tissues of the animal, plus some surrounding tissues, while the other tends to generate cells that will form supporting tissues and others that will signal how the body should develop. But whether or not this happens depends on the pattern of cleavage divisions.

Dr Zernicka-Goetz also discovered that it was possible to predict the future development of cells in four-cell embryos that had divided following a certain pattern. Moreover, the progeny of each of the four cells had different developmental properties – contradicting received wisdom that all four cells are equivalent at this stage. Remarkably, however, all cells in embryos retain developmental flexibility and so these properties are not fixed until later.

See also

• Research: Remembering the mark - animal cloning and genetic 'memory'

External links

• Plusa B et al. The first cleavage of the mouse zygote predicts the blastocyst axis. Nature 2005;434(7031):391–5.
• Piotrowska-Nitsche K et al. Four-cell stage mouse blastomeres have different developmental properties. Development 2005;132(3):479–90.