Mount Holyoke College

Killifish Embryo Deep Cell Migration:Crawling to the Site of a Wound

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This sequence was filmed by Rachel Fink, Mount Holyoke College. It appears in the video A Dozen Eggs: Time-Lapse Microscopy of Normal Development published by The Society for Developmental Biology and Sinauer Associates, Inc.

Individual deep cells migrate throughout the yolk sac of embryonic killifish, Fundulus heteroclitus. These cells migrate through the extracellular matrix of the subepithelial space. Because the embryos are large and transparent, they are ideal for video microscopy. Every detail of locomotion can be viewed as these cells migrate in vivo.

If a small wound is made in the overlying epithelium (the enveloping layer), the deep cells respond by migrating directly toward the site of the wound. This is true if the wound is as small as a single disturbed cell. The exciting thing about this is that merely by wounding the epithelium, a large population of cells can be immediately and repeatedly caused to move in a directional fashion. What is directing the cells toward the wound? There is some evidence that this may be galvanotaxis; directional locomotion in response to a change in an electric field. But chemotaxis and contact guidance may also play roles.

In the movie above, the black arrow points to the site of the wound, and folds in the epithelial layer appear as radiating lines. Soon the movie changes to a higher-power view of many deep cells migrating, and it is obvious that they are all heading toward the top of the screen, where the wound is.