ABSTRACT
Cell interactions in embryos derived from a large diversity of phyla of the animal kingdom have been studied by developmental biologists for many decades. The interest in this specific topic has its foundation in the desire to understand more about the factors that direct the development of a single cell of the fertilized ovum to a precisely structured multicellular organism. Low resistance intercellular junctions between electrically nonexcitable cells were first observed with electrophysiological methods in 1964. Three years later, a cell membrane organelle was recognized by its ultrastructure and appeared to connect the intracellular compartments of cells in close apposition. The accumulated evidence that links gap junctions with events in embryo development was recently summarized by Guthrie. The timing of appearance, presence, and disappearance of gap junctions precedes or coincides with specific developmental events, which lends support to the idea that communication via cell-to-cell channels provides a specific pathway for intercellular signals of a transient nature.
