Intercellular Communication in the Early Embryo
The existence of positional information within an embryo is an essential element of many theories of developmental biology. It is assumed that an embryonic cell is capable of responding to a message concerning its location in the embryo and that its future differentiation is determined by the message received. This concept is consistent with a great many experimental observations which indicate, as Goodwin and Cohen (1969) have suggested, that the embryo must possess a map and a clock and that the cells must be capable of reading both. Experiments on a variety of embryos have demonstrated that the clock is programmed during oogenesis. However, in many instances the map can be redrawn during early development to accommodate the number of cells in the embryo. The timing of many events (such as cell division and orientation of cleavages planes) appears to be primarily an intracellular phenomenon with an inflexible clock. But the decision of a cell to differentiate in one direction and not another often involves interaction with neighboring cells. Thus it is felt that the cell acquires information on its position in the embryo by reception of a message transmitted by another cell. These messages are critical for development because, whatever the intracellular mechanisms of differentiation are, the signal that selects the proper developmental pathway depends positional information.
KeywordsCoupling Coefficient Embryonic Cell Intercellular Communication Intercellular Junction Electrical Coupling
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