CELL ASSOCIATION PATTERN IN AGGREGATES CONTROLLED BY MULTIPLE CELL-CELL ADHESION MECHANISMS

We have previously assumed the presence of two mechanisms for the aggregation of Chinese hamster V79 cells, the Ca²⁺-dependent one and the Ca²⁺-independent one. In order to examine if each of these mechanisms contributed differently to the various aspects of cell aggregation, the morphology of V79 cell aggregates, pretreated so that they were provided with only one of the two adhesion mechanisms, was compared by light and electron microscopy. The adhesion among cells with only the Ca²⁺-dependent mechanism was very tight, with the formation of gap and intermediate junctions. Cells were arranged in a rod or dendric shape in aggregates. In aggregates of cells with only the Ca²⁺-independent mechanism, cells were loosely attached to each other without the formation of specialized junctions and the aggregates were of globular shape. In aggregates of cells with both mechanisms, both characteristics of the above two aggregates were found. Four clones of V79 cells, which formed colonies with different morphology when they were grown in soft agar, were isolated. It was found that such differences were due to the different activity of the Ca²⁺-independent mechanism among these clones. These results suggested that the two adhesion mechanisms play different roles in the cell arrangement in aggregates.