Gap junctions are ubiquitous.
They appear to be involved in the control of growth, the sharing of metabolic products between neighboring cells and in the exchange of signals. Gap junctions appear early between cells. In recent studies we have begun to use confocal microscopy to look at the distribution of a connexin, CX43, by immunofluorescence. We can look at thick slices and reconstruct portions of the embryo in three dimensions. Perhaps the most interesting observation so far has been that CX43 is particularly abundant in those parts of the embryo where inductive tissue interactions are taking place.