Induction or Inhibition Interactions

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Inductive Interaction: The interaction between two groups of cells in which a signal passed from one group of cells causes the other group of cells to change their developmental state.

Lateral Inhibition: The signal produced by one cell that prevents adjacent cells from adopting the same developmental fate as that of the first cell.

These two types of cell-cell interactions are both demonstrated in the development of the vulva in the nematode C. elegans. Vulva development has been studied through the analysis of mutants that either have no vulva or too many.

Initally, all cells have the potential to adopt any of the required roles. They are called an equivalence group. To make an intact vulva, one of the cells must develop into the primary vulva cell and two others must become secondary vulva cells. The remaining cells become tertiary vulva cells that make up the surrounding body wall of the worm.

The anchor cell is essential in allocating the different cell fates. This cell lies underneath the equivalence group. The anchor cell secretes a polypeptide ligand that binds to a receptor present on all of the equivalence group cells. Only the cell that receives the highest level of this signal will develop into the primary vulva cell.

The anchor cell operates through the inductive interaction to commit a cell to the primary vulva fate.

Once established, the primary vulva cell sends out a different paracrine signal to its immediate neighbours to prevent them from becoming a primary vulva cell. This process of lateral inhibition leads these cells to develop into secondary vulva cells. Remaining equivalence group cells become tertiary vulva cells.