Mount Holyoke College

In vivo cytoskeletal dynamics of living fish embryos
Movie #4:Actin dynamics in Apical Ridges of EVL Cells


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Epithelial cells that form confluent tissues, where each cell is tightly glued to its neighbors by circumferential junctions like bands of velcro, form the earliest skin of the killifish embryo. This process starts as a small cap of cells spreads to cover the entire sphere of yolk (in large fish embryos this is a herculean task, and can take days). Our videos of the apical (outside-facing) side of these cells show that the cell surface is extremely dynamic, blistering and boiling with small surface protrusions, filled with actin (see also movie #5). This video shows these protrusions in parts of three neighboring cells, and the circumferential actin-filled ridges at the cell margins are particularly dramatic. The actin used in these protrusions is the same pool used by deep cells for individual migration, and these enveloping (EVL) cells use the same kinds of biochemical controls for polymerization (rapid growth) and depolymerization (shrinkage) of filaments.