Abstract
Polarising a cell or an embryo is a crucial and recurrent event during development, as it is important for cell differentiation and migration. Cells can become polarised along their apical-basal axis and also within the plane of the tissue layer to which they belong. The embryo develops three axes: the anteroposterior, the dorsoventral and the left-right axis. Recent work indicates instructive roles for cell adhesion molecules in establishing not only apical-basal polarity but also planar cell polarity and, surprisingly, in the generation of left-right asymmetry in vertebrates. Signalling cascades that regulate polarity formation seem to be conserved among different organisms, thereby raising the intriguing question of whether this also holds true for the cell adhesion molecules.
