Life at the Edge: Epiboly and Involution in the Zebrafish

Abstract

In the developing zebrafish, the mid-blastula stage embryo finds itself organized as an abashed mass of blastomeres on top of a large yolk cell. Over the next few hours, these cells begin a beautiful sweep over the yolk cell as they form the germ layers. These dramatic and exquisite movements form the zebrafish gastrula, and the changes in the embryo are so obvious that they form the basis for staging the embryo for much of the first day of development (Fig. 1). What physical forces underlie these movements? What is the genetic basis for these movements? And, what is the immediate consequence of cell movement for the embryo?