Spatio-temporal distribution of gap junctions in zebra fish embryo.

The distribution of gap junctions in zebra fish embryo is a dynamic process. They appear during cleavage stages and are uniformly distributed between deep cells in early blastula. By mid-blastula stage their density increases all over the embryo. At this stage lightly stained L cells and densely stained D cells (Dasgupta and Singh 1981; Wilhelm Roux's Arch Dev Biol 190:358) develop some differences in their surface properties due to which the frequencies of gap junctions between homologous (L-L and D-D) cells are two- to threefold higher than between heterologous (L-D) cells. Before the initiation of epipoly the gap junction occurrence increases in the envelopinglayer (EVL) and then decreases. The possible functional significance of the organization of these junctions is discussed.