Existence of gradient in cell adhesiveness along the developing Xenopus hind limb bud, shown by a cellular sorting-out experiment in vitro

To examine the possibility of a difference in cell adhesiveness along the developing Xenopus hind limb bud axes, single mesenchymal cells from developing hind limb buds were cultured, allowing them to form an aggregate in a gyratory culture system. By observing the distribution of cells within aggregates, it was found that sorting-out occurred between cells from different positions and different stages. Cells derived from more distal positions tended to be situated interiorly in the aggregates. According to Steinberg's differential adhesion hypothesis, these results support the idea that there is a graded difference in cell adhesiveness along the proximo-distal axis of the developing limb, with adhesiveness increasing distally. Although similar sorting-out was observed between anterior and posterior cell populations, it could not be determined which cell populations were definitely more cohesive. These properties may be correlated with the experimentally demonstrated 'positional value', which should be different among cells located at different positions along the axes of the developing vertebrate limb bud.