Change is good. This mantra isn’t good for just uptight type-As like me, but for embryos too. Morphogenesis describes the physical changes that shape an organism out of a ball of cells, and is at the center of countless obsessions and questions of developmental biologists. Today’s image is from a paper that helps us understand how a sheet of cells can form three-dimensional structures.
Morphogenesis describes the physical transformation and organization of cells into the shape of a developing organ or organism. In the developing fruit fly egg, the epithelial layer of cells surrounding the egg chamber develops two dorsally projecting tubes, in which appendages used for gas exchange by the embryo form. This transformation of a sheet of cells into a three-dimensional tube structure is not completely understood, but a recent paper describes the cell rearrangements involved. Osterfield and colleagues used live imaging and three-dimensional reconstruction to show that the formation of the appendages is driven by epithelial sheet bending and a series of cell intercalations, which correlates with the localizations of myosin and the polarity protein Bazooka. Using computational models, Osterfield and colleagues test how a pattern of line tensions in cell-cell edges in the epithelial sheet could drive three-dimensional changes. The images above show fruit fly egg chambers during appendage formation (top row). Three-dimensional reconstructions (bottom row) show the process from above (left) and the side (middle, right), with the arrow pointing to out-of-plane bending of the tissue.
Osterfield, M., Du, X., Schüpbach, T., Wieschaus, E., & Shvartsman, S. (2013). Three-Dimensional Epithelial Morphogenesis in the Developing Drosophila Egg Developmental Cell, 24 (4), 400-410 DOI: 10.1016/j.devcel.2013.01.017
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